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Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Jul. 31, 2017	Aug. 30, 2017
Document Information [Line Items]
Entity Registrant Name	Ocean Power Technologies, Inc.
Entity Central Index Key	0001378140
Trading Symbol	optt
Current Fiscal Year End Date	--04-30
Entity Filer Category	Smaller Reporting Company
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		12,526,124
Document Type	10-Q
Document Period End Date	Jul. 31, 2017
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017
ASSETS
Cash and cash equivalents	$ 11,414	$ 8,421
Marketable securities	25	25
Restricted cash- short-term	361	334
Accounts Receivable	86	48
Unbilled receivables	163	296
Litigation receivable	350
Other current assets	383	622
Total current assets	12,782	9,746
Property and equipment, net	146	170
Restricted cash- long-term	154	154
Other noncurrent assets	3	3
Total assets	13,085	10,073
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	183	586
Accrued expenses	1,530	3,059
Litigation payable	350
Warrant liabilities	286	323
Current portion of capital lease obligations	36	35
Deferred credits payable current	600	600
Total current liabilities	2,985	4,603
Long-term portion of capital lease obligations	14	23
Total liabilities	2,999	4,626
Commitments and contingencies
Ocean Power Technologies, Inc. stockholders’ equity:
Preferred stock, $0.001 par value; authorized 5,000,000 shares, none issued or outstanding
Common stock, $0.001 par value; authorized 50,000,000 shares, issued 12,621,205 and 6,313,996 shares, respectively	13	6
Treasury stock, at cost; 70,081 and 48,065 shares, respectively	(295)	(263)
Additional paid-in capital	200,549	193,234
Accumulated deficit	(190,043)	(187,370)
Accumulated other comprehensive loss	(138)	(160)
Total stockholders' equity	10,086	5,447
Total liabilities and stockholders’ equity	$ 13,085	$ 10,073

Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Jul. 31, 2017	Apr. 30, 2017
Preferred stock par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	12,621,205	6,313,996
Treasury stock (in shares)	70,081	48,065

Unaudited Consolidated Statements of Operations - USD ($) shares in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Revenues	$ 195,000	$ 202,000
Cost of revenues	217,000	127,000
Gross profit (loss)	(22,000)	75,000
Operating expenses:
Product development costs	1,102,000	1,636,000
Selling, general and administrative costs	1,641,000	1,519,000
Total operating expenses	2,743,000	3,155,000
Operating loss	(2,765,000)	(3,080,000)
Change in fair value of warrant liabilities	37,000	(752,000)
Interest income, net	3,000
Foreign exchange gain	62,000	5,000
Net loss	$ (2,663,000)	$ (3,827,000)
Basic and diluted net loss per share (in dollars per share)	$ (0.22)	$ (1.72)
Weighted average shares used to compute basic and diluted net loss per share (in shares)	12,268,683	2,228,585

Unaudited Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Net loss	$ (2,663)	$ (3,827)
Foreign currency translation adjustment	22	(31)
Total comprehensive loss	$ (2,641)	$ (3,858)

Unaudited Consolidated Statements of Stockholders' Equity - 3 months ended Jul. 31, 2017 - USD ($) $ in Thousands	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Apr. 30, 2017	6,313,996	(48,065)
Balance at Apr. 30, 2017	$ 6	$ (263)	$ 193,234	$ (187,370)	$ (160)	$ 5,447
Net loss				(2,663)		(2,663)
Stock based compensation			91			91
Issuance of restricted stock, net (in shares)	114,459
Issuance of restricted stock, net
Sale of stock, net of financing costs (in shares)	6,192,750
Sale of stock, net of financing costs	$ 7		7,214			7,221
Acquisition of treasury stock (in shares)		(22,016)
Acquisition of treasury stock		$ (32)				(32)
Other comprehensive loss					22	22
Balance (in shares) at Jul. 31, 2017	12,621,205	(70,081)
Balance at Jul. 31, 2017	$ 13	$ (295)	200,549	(190,043)	(138)	10,086
Adoption of accounting standard update related to stock compensation accounting (ASU 2016-09)			$ 10	$ (10)

Unaudited Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Cash flows from operating activities:
Net loss	$ (2,663,000)	$ (3,827,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Foreign exchange gain	(62,000)	(5,000)
Depreciation and amortization	31,000	34,000
Loss on disposal of property, plant and equipment	4,000
Compensation expense related to stock option grants and restricted stock	91,000	218,000
Change in fair value of warrant liabilities	(37,000)	752,000
Changes in operating assets and liabilities:
Accounts receivable	(38,000)	(150,000)
Unbilled receivable	133,000	(13,000)
Other assets	239,000	(370,000)
Accounts payable	(405,000)	264,000
Accrued expenses	(1,531,000)	215,000
Unearned revenues		(39,000)
Net cash used in operating activities	(4,238,000)	(2,921,000)
Cash flows from investing activities:
Purchases of marketable securities		(25,000)
Purchases of equipment	(12,000)	(5,000)
Net cash used in investing activities	(12,000)	(30,000)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of costs	7,221,000
Proceeds from issuance of common stock and related warrants, net of costs		5,261,000
Payment of capital lease obligations	(9,000)
Payment of debt		(32,000)
Acquisition of treasury stock	(32,000)	(4,000)
Net cash provided by financing activities	7,180,000	5,225,000
Effect of exchange rate changes on cash and cash equivalents	90,000	(13,000)
Net increase in cash, cash equivalents and restricted cash	3,020,000	2,261,000
Cash, cash equivalents and restricted cash, beginning of period	8,909,000	7,030,000
Cash, cash equivalents and restricted cash, end of period	11,929,000	9,291,000
Supplemental schedule of cash flows information:
Cash paid for interest	$ 1,000	$ 2,000

Note 1 - Background, Basis of Presentation and Liquidity

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Business Description and Basis of Presentation [Text Block]

(

) Background, Basis of Presentation and Liquidity

a)	Background

Ocean Power Technologies, Inc. (the “Company”) was founded in

1984

in New Jersey, commenced business operations in

1994

and re-incorporated in Delaware in

2007.

The Company is developing and commercializing its proprietary systems that generate electricity by harnessing the renewable energy of ocean waves. The Company uses proprietary technologies that convert the mechanical energy created by the heaving motion of ocean waves into electricity. The Company has designed and continues to develop the PowerBuoy product line which is based on modular, ocean-going buoys, which the Company has been periodically ocean testing since

1997.

The Company markets its PowerBuoys in the United States and internationally. Since fiscal

2002,

government agencies have accounted for a significant portion of the Company’s revenues. These revenues were largely for the support of product development efforts. The Company’s goal is that an increased portion of its revenues be from the sale or lease of products and maintenance services, as compared to revenue to support its product development efforts. As the Company continues to advance its proprietary technologies, it expects to continue to have a net decrease in cash from operating activities unless and until it achieves positive cash flow from the planned commercialization of products and services.

b)	Basis of Presentation

The accompanying unaudited consolidated financial statements have been prepared in accordance with generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form

-Q and Article

of Regulation S-

Accordingly, they do

not

include all the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. The interim operating results are

not

necessarily indicative of the results for a full year or for any other interim period. Further information on potential factors that could affect the Company's financial results can be found in the Company's Annual Report on Form

-K for the year ended

April 30, 2017

filed with the Securities and Exchange Commission (“SEC”) and elsewhere in this Form

-Q.

c)	Liquidity/Going Concern

The consolidated financial statements have been prepared assuming the Company will continue as a going concern. The Company has experienced substantial and recurring losses from operations, which have contributed to an accumulated deficit of

$190.0

million as of

July 31, 2017.

As of

July 31, 2017,

the Company had approximately

$11.4

million in cash and cash equivalents on hand. The Company generated revenues of

$0.2

million during each of the

three

months ended

July 31, 2017

and

2016.

Based on the Company’s cash and cash equivalents and marketable securities as of

July 31, 2017,

the Company believes that it will be able to finance its capital requirements and operations into the quarter ending

July 31, 2018.

The Company will require additional equity and/or debt financing to continue its operations. The Company cannot provide assurances that it will be able to secure additional funding when needed or at all, or, if secured, that such funding would be on favorable terms. These factors raise substantial doubt about the Company’s ability to continue as a going concern.

The consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. The consolidated financial statements do

not

include any adjustments relating to the recoverability and classification of recorded assets amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty.

Management is evaluating different strategies to obtain the required additional funding for future operations. These strategies

may

include, but are

not

limited to, additional funding from current or new investors, officers and directors; borrowings of debt; a public offering of the Company’s equity or debt securities; partnerships and/or collaborations. There can be

assurance that any of these future-funding efforts will be successful.

In fiscal

2017

and the

three

months ended

July 31, 2017,

the Company has continued to make investments in ongoing product development efforts in anticipation of future growth. The Company’s future results of operations involve significant risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are

not

limited to, risks from lack of available financing and insufficient capital, performance of PowerBuoys,

its inability to market and commercialize its PowerBuoys, technology development, scalability of technology and production, dependence on skills of key personnel, concentration of customers and suppliers, deployment risks and laws, regulations and permitting. In order to continue to implement its business strategy, the Company requires additional equity and/or debt financing. The Company closed

four

equity financing arrangements during the year ended

April 30, 2017

and

three

months ended

July 31, 2017.

The Company does

not

currently have any committed sources of debt or equity financing, and the Company cannot assure that additional equity and/or debt financing will be available to the Company as needed on acceptable terms, or at all. Historically, the Company has raised capital through securities sales in the public capital markets. If sufficient additional financing is

not

obtained when needed, the Company

may

be required to further curtail or limit operations, product development costs, and/or selling, general and administrative activities in order to reduce its cash expenditures. This could cause the Company to be unable to execute its business plan, take advantage of future opportunities and

may

cause it to scale back, delay or eliminate some or all of its product development activities and/or reduce the scope of or cease its operations.

June 2, 2016,

the Company entered into a securities purchase agreement, which was amended on

June 7, 2016 (

as amended, the “Purchase Agreement”) with certain institutional purchasers (the

“June

Purchasers”). Pursuant to the terms of the

June

Purchase Agreement, the Company sold an aggregate of

417,000

shares of Common Stock together with warrants to purchase up to an aggregate of

145,952

shares of Common Stock. Each share of Common Stock was sold together with a warrant to purchase

0.35

of a share of Common Stock at a combined purchase price of

$4.60.

The net proceeds to the Company from the offering were approximately

$1.7

million, after deducting placement agent fees and estimated offering expenses payable by the Company, but excluding the proceeds, if any, from the exercise of the warrants issued in the offering. The warrants have an exercise price of

$6.08

per share, became exercisable on

December 3, 2016 (

“Initial Exercise Date”), and will expire

five

years following the Initial Exercise Date.

The Company paid the placement agents approximately

$0.1

million as placement agent fees in connection with the sale of securities in the offering. The Company also reimbursed the placement agents

$35,000

for their out of pocket and legal expenses in connection with the offering.

July 22, 2016,

the Company entered into the Second Amendment to the Purchase Agreement (the “Second Amended Purchase Agreement”) with certain purchasers (the

“July

Purchasers”). Pursuant to the terms of the Second Amended Purchase Agreement, the Company sold an aggregate of

595,000

shares of Common Stock together with warrants to purchase up to an aggregate of

178,500

shares of Common Stock. Each share of Common Stock was sold together with a warrant to purchase

0.30

of a share of Common Stock at a combined purchase price of

$6.75.

The net proceeds to the Company from the offering were approximately

$3.6

$9.36

per share. The Warrants will expire on the

fifth

(

5th

) anniversary of the initial date of issuance.

October 19, 2016,

the Company sold

2,760,000

shares of common stock at a price of

$2.75

per share, which includes the sale of

360,000

shares of the Company’s common stock sold by the Company pursuant to the exercise, in full, of the over-allotment option by the underwriters in a public offering. The net proceeds to the Company from the offering were approximately

$6.9

million, after deducting underwriter fees and offering expenses payable by the Company.

May 2, 2017,

the Company sold

6,192,750

shares of common stock at a price of

$1.30

per share, which includes the sale of

807,750

$7.2

million, after deducting underwriter fees and offering expenses payable by the Company.

The sale of additional equity or convertible securities could result in dilution to stockholders. If additional funds are raised through the issuance of debt securities, these securities could have rights senior to those associated with the Company’s Common Stock and could contain covenants that would restrict its operations. Financing

may

not

be available in amounts or on terms acceptable to the Company, or at all. If the Company is unable to obtain required financing, it

may

be required to reduce the scope of its operations, including its planned product development and marketing efforts, which could materially and adversely harm its financial condition and operating results. If the Company is unable to secure additional financing, it

may

be forced to cease operations.

Note 2 - Summary of Significant Accounting Policies

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Significant Accounting Policies [Text Block]

(

) Summary of Significant Accounting Policies

(a) Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its majority-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

(b) Use of Estimates

The preparation of the consolidated financial statements requires management of the Company to make a number of estimates and assumptions relating to the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the period. Significant items subject to such estimates and assumptions include the recoverability of the carrying amount of property and equipment; fair value of warrant liabilities, valuation allowances for receivables and deferred income tax assets; estimated costs to complete projects; and percentage of completion of customer contracts for purposes of revenue recognition. Actual results could differ from those estimates.

The current economic environment, particularly the macroeconomic pressures in certain European countries, has increased the degree of uncertainty inherent in those estimates and assumptions.

The Company’s contracts are either cost plus or fixed price contracts. Under cost plus contracts, customers are billed for actual expenses incurred plus an agreed-upon fee. Under cost plus contracts, a profit or loss on a project is recognized depending on whether actual costs are more or less than the agreed upon amount.

The Company has

two

types of fixed price contracts, firm fixed price and cost-sharing. Under firm fixed price contracts, the Company receives an agreed-upon amount for providing products and services specified in the contract, a profit or loss is recognized depending on whether actual costs are more or less than the agreed upon amount. Under cost-sharing contracts, the fixed amount agreed upon with the customer is only intended to fund a portion of the costs on a specific project. Under cost sharing contracts, an amount corresponding to the revenue is recorded in cost of revenues, resulting in gross profit on these contracts of zero. The Company’s share of the costs is recorded as product development expense.

Generally, revenue under fixed price or cost plus contracts is recognized using the cost to cost percentage-of-completion method, measured by the ratio of costs incurred to total estimated costs at completion. In certain circumstances, revenue under contracts that have specified milestones or other performance criteria

may

be recognized only when the customer acknowledges that such criteria have been satisfied. If an arrangement involves multiple deliverables, the delivered items are considered separate units of accounting if the items have value on a stand-alone basis. Amounts allocated to each element are based on its objectively determined fair value, such as the sales price for the product or service when it is sold separately or competitor prices for similar products or services.

In addition, recognition of revenue (and the related costs)

may

be deferred for fixed price contracts until contract completion if the Company is unable to reasonably estimate the total costs of the project prior to completion. These contracts are subject to interpretation and management

may

make a judgment as to the amount of revenue earned and recorded. Because the Company has a small number of contracts, revisions to the percentage-of-completion determination, management interpretation or delays in meeting performance and contractual criteria or in completing projects

may

have a significant effect on revenue for the periods involved. Upon anticipating a loss on a contract, the Company recognizes the full amount of the anticipated loss in the current period.

Unbilled receivables represent expenditures on contracts, plus applicable profit margin,

not

yet billed. Unbilled receivables are normally billed and collected within

one

year. Billings made on contracts are recorded as a reduction of unbilled receivables, and to the extent that such billings and cash collections exceed costs incurred plus applicable profit margin, they are recorded as unearned revenues.

(d) Cash, Cash Equivalents, Restricted Cash and Security Agreements

Cash and Cash Equivalents

The Company considers all highly liquid investments with a maturity of

three

months or less when purchased to be cash equivalents. The Company invests excess cash in an overnight U.S. government securities repurchase bank account and a money market account. In accordance with the terms of the repurchase agreement, the Company does

not

take possession of the related securities. The agreement contains provisions to ensure that the market value of the underlying assets remain sufficient to protect the Company in the event of default by the bank by requiring that the underlying securities have a total market value of at least

100%

of the bank’s total obligations under the agreement.

	July 31, 2017		April 30, 2017
	(in thousands)

Checking and savings accounts	$	4,400	$	4,241
Overnight repurchase account		7,014		4,180
	$	11,414	$	8,421

Restricted Cash and

Security Agreements

A portion of the Company’s cash is restricted under the terms of

two

security agreements.

One agreement is between the Company and Barclays Bank. Under this agreement, the cash is on deposit at Barclays Bank and serves as security for letters of credit and bank guarantees that are expected to be issued by Barclays Bank on behalf of OPT LTD,

one

of the Company's subsidiaries, under a credit facility established by Barclays Bank for OPT LTD. The credit facility is approximately

€0.3

million (

$0.3

million) and carries a fee of

per annum of the amount of any such obligations issued by Barclays Bank. The credit facility does

not

have an expiration date, but is cancelable at the discretion of the bank. As of

July 31, 2017,

there was

€0.3

million (

$0.3

million) in letters of credit outstanding under this agreement.

The

second

agreement is between the Company and Santander Bank. Under this agreement, the cash is on deposit at Santander Bank and serves as security for letter of credit issued by Santander Bank for the lease of new warehouse/office space in Monroe Township, New Jersey. The agreement cannot be extended beyond

January 31, 2025,

and is cancelable at the discretion of the bank. Restricted cash includes the following:

	July 31, 2017		April 30, 2017
	(in thousands)

Barclay's Bank Agreement	$	361	$	334
Santander Bank		154		154
	$	515	$	488

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in the statement of cash flows.

	July 31, 2017		April 30, 2017
	(in thousands)

Cash and cash equivalents	$	11,414	$	8,421
Restricted cash- short term		361		334
Restricted cash- long term		154		154
	$	11,929	$	8,909

(e) Marketable Securities

Marketable securities with original maturities longer than

three

months but that mature in less than

one

year from the balance sheet date are classified as current assets. Marketable securities that the Company has the intent and ability to hold to maturity are classified as investments held-to-maturity and are reported at amortized cost. The difference between the acquisition cost and face values of held-to-maturity investments is amortized over the remaining term of the investments and added to or subtracted from the acquisition cost and interest income. As of

July 31, 2017

and

April 30, 2017,

all of the Company’s investments were classified as held-to-maturity.

(f) Foreign Exchange Gains and Losses

The Company has invested in certain certificates of deposit and has maintained cash accounts that are denominated in British pounds sterling, Euros and Australian dollars. These amounts are included in cash, cash equivalents, restricted cash and marketable securities on the accompanying consolidated balance sheets. Such positions

may

result in realized and unrealized foreign exchange gains or losses from exchange rate fluctuations, which are included in “Foreign exchange gain/(loss)” in the accompanying consolidated statements of operations.

(g) Property and Equipment

Property and equipment is stated at cost, less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives (

three

seven

years) of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the remaining lease term. Expenses for maintenance and repairs are charged to operations as incurred. Property and equipment is also reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset

may

not

be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of the asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of the asset exceeds its estimated future cash flows, then an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset.

(h) Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash balances, bank certificates of deposit and trade receivables. The Company invests its excess cash in highly liquid investments (principally, short-term bank deposits, Treasury bills, Treasury notes and money market funds) and does

not

believe that it is exposed to any significant risks related to its cash accounts, money market funds or certificates of deposit.

The table below shows the percentage of the Company's revenues derived from customers whose revenues accounted for at least

10%

of the Company's consolidated revenues for at least

one

of the periods indicated:

	Three months ended July 31,
Customer	2017			2016

Mitsui Engineering & Shipbuilding		67	%		100	%
U.S. Department of Defense Office of Naval Research		33	%		-
		100	%		100	%

The loss of, or a significant reduction in revenues from a current customer could significantly impact the Company's financial position or results of operations. The Company does

not

require its customers to maintain collateral.

(i) Warrant Liabilities

The Company's warrants to purchase shares of its common stock are classified as warrant liabilities and are recorded at fair value. The warrant liabilities are subject to re-measurement at each balance sheet date and the Company recognizes any change in fair value in its consolidated statements of operations within “Change in fair value of warrant liabilities.” The Company will continue to adjust the carrying value of the warrants for changes in the estimated fair value until such time as these instruments are exercised or expire. At that time, the liabilities will be reclassified to “Additional paid-in capital”, a component of “Stockholders' equity” on the consolidated balance sheets.

(j) Net Loss per Common Share

Basic and diluted net loss per share for all periods presented is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Due to the Company's net losses, potentially dilutive securities, consisting of outstanding stock options and non-vested performance-based shares, were excluded from the diluted loss per share calculation due to their anti-dilutive effect.

In computing diluted net loss per share, options to purchase shares of common stock, warrants on common stock and non-vested restricted stock issued to employees and non-employee directors, totaling

701,977

for the

three

months ended

July 31, 2017

and

711,453

for the

three

months ended

July 31, 2016,

were excluded from each of the computations as the effect would be anti-dilutive due to the Company's losses.

(

)

Share-Based Compensation

Costs resulting from all share-based payment transactions are recognized in the consolidated financial statements at their fair values. The aggregate share-based compensation expense recorded in the consolidated statements of operations for the

three

months ended

July 31, 2017

and

2016

was approximately

$0.1

million and

$0.2

million, respectively. The following table summarizes share-based compensation related to the Company’s share-based plans by expense category for the

three

months ended

July 31, 2017

and

2016:

	Three months ended July 31,
	2017		2016
	(in thousands)

Product development	$	13	$	53
Selling, general and administratvie		78		165
Total share-based compensation expense	$	91	$	218

(l) Recently Issued Accounting Standards

May 2014,

the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”)

No.

2014

09,

“

Revenue from Contracts with Customers (Topic

606

).”

ASU

2014

outlines a new, single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. This new revenue recognition model provides a

five

-step analysis in determining when and how revenue is recognized. The new model will require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration a company expects to receive in exchange for those goods or services. The FASB subsequently issued additional clarifying standards to address issues arising from implementation of the new revenue standard, including a

one

-year deferral of the effective date for the new revenue standard. Public companies should now apply the guidance in ASU

2014

to annual reporting periods beginning after

December

15,

2017

and interim periods within those annual periods. Earlier application is permitted only as of annual reporting periods beginning after

December

15,

2016,

including interim periods within that annual period. As such, the Company is required to adopt this standard effective in fiscal

2019,

which begins

May 1, 2018.

Companies

may

use either a full retrospective or a modified retrospective approach to adopt ASU

2014

09.

The Company has

not

yet completed its final review of the impact of this guidance; however the Company anticipates applying the modified retrospective method upon adoption of ASU

2014

May 1, 2018.

The impact to the Company could be affected by the nature and terms of potential future contracts with customers, as those contracts

may

have terms that differ from the Company’s current contracts.

August 2014,

the FASB issued ASU

2014

15,

“Disclosure of Uncertainties about an Entity’s Ability

to Continue as a Going Concern”,

which describes how an entity should assess its ability to meet obligations and sets rules for how this information should be disclosed in the financial statements. The standard provides accounting guidance that will be used along with existing auditing standards. The new standard applies to all entities for the

first

annual period ending after

December 15, 2016,

and interim periods thereafter. Early application is permitted. The Company adopted ASU

2014

for the fiscal year

2017.

The Company’s addition of the standard did

not

have a material impact on its disclosures.

See section (c) “Liquidity/Going Concern” within Note (

) “Background and Liquidity” of the consolidated financial statements included in this Quarterly Report on Form

-Q for further discussion on the Company’s ability to continue as a going concern.

January 2016,

the FASB issued ASU

No.

2016

01,

“Recognition and Measurement of Financial Assets and Financial Liabilities”,

which makes limited amendments to the guidance in U.S. GAAP on the classification and measurement of financial instruments. The update significantly revises an entity's accounting related to the classification and measurement of investments in equity securities and the presentation of certain fair value changes for financial liabilities measured at fair value. It also amends certain disclosure requirements associated with the fair value of financial instruments. The update will take effect for public companies for fiscal years beginning after

December 15, 2017,

including interim periods within those fiscal years. The Company will evaluate the effect of ASU

2016

for future periods as applicable.

February 2016,

the FASB issued ASU

No.

2016

02,

“Leases (Topic

842

).” The new standard establishes a right-of-use (ROU) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than

months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. ASU

2016

is effective for annual periods beginning after

December

15,

2018,

including interim periods within those annual periods, with early adoption permitted. A modified retrospective transition approach is required for lessees for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. The Company is evaluating the effect ASU

2016

will have on its consolidated financial statements and disclosures and has

not

yet determined the effect of the standard on its ongoing financial reporting at this time.

March 2016,

the FASB issued ASU

No.

2016

09,

“Compensation - Stock Compensation (Topic

718

)

”

The amendments of ASU

No.

2016

were issued as part of the FASB's Simplification initiative focused on improving areas of GAAP for which cost and complexity

may

be reduced while maintaining or improving the usefulness of information disclosed within the financial statements. The amendments focused on simplification specifically with regard to share-based payment transactions, including accounting for forfeitures, income tax consequences, classification of awards as equity or liabilities and classification on the statement of cash flows. The guidance in ASU

No.

2016

is effective for fiscal years beginning after

December 15, 2016,

and interim periods within those annual periods. The Company adopted ASU

2016

May 1, 2017.

Certain of the amendments are applied using a modified retrospective transition method by means of a cumulative-effect adjustment to equity as of

May 1, 2017,

while other amendments are applied retrospectively, prospectively or using either a prospective or a retrospective transition method. Upon adoption, the Company is beginning to account for forfeitures as they occur rather than estimate a forfeiture rate and has recorded a cumulative-effect adjustment in equity of approximately

$10,000

on the date of initial adoption. In periods subsequent to adoption, a higher expense will be recognized earlier during the respective vesting periods of stock-based awards that are

not

forfeited. The Company expects that the income tax amendments within ASU

2016

will have

impact on its results of operations or cash flows because it is in a net operating loss position with a full valuation allowance.

August 2016,

the FASB issued ASU

2016

15,

“Statement of Cash Flows (Topic

230

): Classification

of Certain Cash Receipts and Cash Payments”,

providing additional guidance on

eight

specific cash flow classification issues. The goal of the ASU is to reduce diversity in practice of classifying certain items. The amendments in the ASU are effective for

fiscal years beginning after

December 15, 2017,

and interim periods within those fiscal years and early adoption is permitted. The Company has evaluated the effect ASU

2016

will have on its consolidated financial statements and disclosures and has determined the standard will have

impact on its ongoing financial reporting at this time.

November 2016,

the FASB issued ASU

2016

18,

“Statement of Cash Flows (Topic

230

): Restricted

Cash”,

which amends guidance and presentation related to restricted cash in the statement of cash flows, including stating that amounts generally described as restricted cash and restricted cash equivalents should be included within cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown in the statement of cash flows. An entity is required to provide a disclosure indicating the reconciliation of all cash accounts. The amendments in the ASU are effective for

fiscal years beginning after

December 15, 2017,

and interim periods within those fiscal years and early adoption is permitted. The Company has early adopted ASU

2016

effective

May 1, 2017.

In connection with the adoption of the standard the Company has used a retrospective transition method for each period presented in the statement of cash flows. The Company reclassified

$488,000

and

$300,000

of restricted cash to cash, cash equivalents and restricted cash, beginning of period for the period

April 30, 2017

and

April 30, 2016

in the statement of cash flows. The Company reclassified

$266,000

of restricted cash to cash, cash equivalents and restricted cash, end of period for the period ended

July 31, 2016

in the statement of cash flows.

Note 3 - Marketable Securities

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]

(

) Marketable Securities

Marketable securities with initial maturities greater than

three

months but that mature within

one

year from the balance sheet date are classified as current assets and are summarized as follows:

	July 31, 2017		April 30, 2017
	(in thousands)

Certificate of Deposit	$	25	$	25

Note 4 - Accrued Expenses

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Supplemental Balance Sheet Disclosures [Text Block]

(

) Accrued Expenses

Accrued expenses consist of the following at

July 31, 2017

and

April 30, 2017.

	July 31, 2017		April 30, 2017
	(in thousands)

Project costs	$	46	$	898
Contract loss reserve		298		238
Employee incentive payments		142		643
Accrued salary and benefits		420		484
Legal and accounting fees		358		478
Accrued taxes payable		132		132
Other		134		186
	$	1,530	$	3,059

Note 5 - Deferred Credits Payable	3 Months Ended
Note 5 - Deferred Credits Payable	Jul. 31, 2017
Notes to Financial Statements
Customer Advances and Deposits Disclosure [Text Block]	( 5 ) Deferred Credits Payable During the year ended April 30, 2001, in connection with the sale of common stock to an investor, the Company received $0.6 million from the investor in exchange for an option to purchase up to 500,000 metric tons of carbon emissions credits generated by the Company during the years 2008 through 2012, at a 30% discount from the then-prevailing market rate. If the Company received emission credits under applicable laws and failed to sell to the investor the credits up to the full amount of emission credits covered by the option, the investor was entitled to liquidated damages equal to 30% of the aggregate market value of the shortfall in emission credits (subject to a limit on the market price of emission credits). Under the terms of the agreement, if the Company did not become entitled under applicable laws to the full amount of emission credits covered by the option by December 31, 2012, the Company was obligated to return the option fee of $0.6 million, less the aggregate discount on any emission credits sold to the investor prior to such date. In December 2012, the Company and the investor agreed to extend the period for the sale of emission credits until December 31, 2017. As of July 31, 2017, the Company has not generated any emissions credits eligible for purchase under the agreement. As a result, the Company anticipates returning the option fee of $0.6 million. Therefore, the $0.6 million is reflected in the consolidated balance sheets within “Deferred credits payable current” as of July 31, 2017 and April 30, 2017, respectively.

Note 6 - Warrants

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Warrant Disclosure [Text Block]

(

) Warrants

June 2, 2016,

the Company entered into a securities purchase agreement, which was amended on

June 7, 2016 (

as amended, the

“June

Purchase Agreement”) with certain institutional purchasers (the

“June

Purchasers”). Pursuant to the terms of the

June

Purchase Agreement, the Company sold an aggregate of

417,000

shares of Common Stock together with warrants to purchase up to an aggregate of

145,952

shares of Common Stock. Each share of Common Stock was sold together with a warrant to purchase

0.35

of a share of Common Stock at a combined purchase price of

$4.60.

The warrants have an exercise price of

$6.08

per share, became exercisable on

December 3, 2016 (

“Initial Exercise Date”), and will expire

five

years following the Initial Exercise Date.

July 22, 2016,

the Company entered into a Second Amendment to the Purchase Agreement (the “Second Amended Purchase Agreement”) with certain institutional purchasers (the

“July

Purchasers”). Pursuant to the terms of the Second Amended Purchase Agreement, the Company sold an aggregate of

595,000

shares of Common Stock together with warrants to purchase up to an aggregate of

178,500

shares of Common Stock. Each share of Common Stock was sold together with a warrant to purchase

0.30

of a share of Common Stock at a combined purchase price of

$6.75.

The Warrants were exercisable immediately at an exercise price of

$9.36

per share. The Warrants will expire on the

fifth

(

5th

) anniversary of the initial date of issuance.

Both sets of warrants contain a feature whereby they could require the transfer of assets and therefore are classified as a liability in accordance with ASC

480.

As such, the warrants with a value of

$0.3

million and

$0.3

million at

July 31, 2017

and

April 30, 2017,

respectively, are reflected within “Warrant liabilities” in the unaudited consolidated balance sheets.

An unrealized gain and unrealized loss of approximately

$37,000

and

$752,000,

respectively, were included within “Change in fair value of warrant liability” in the consolidated statements of operations for the

three

months ended

July 31, 2017

and

2016,

respectively. The Company determined the fair value using the Black-Scholes option pricing model with the following assumptions:

	July 31, 2017			July 31, 2016

Dividend rate		0.0%			0.0%
Risk-free rate		1.68%			1.00%
Expected life (years)	4.0	-	4.4	5.0	-	5.4
Expected volatility		140.3%			125.4%

Note 7 - Stock-based Compensation

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Disclosure of Compensation Related Costs, Share-based Payments [Text Block]

(

) Stock-Based Compensation

(a) Stock Options

Valuation Assumptions for Options Granted during the

three

months ended

July 31, 2017

and

2016

The fair value of each stock option granted, for both service-based and performance-based vesting requirements during the

three

months ended

July 31, 2017

and

2016,

was estimated at the date of grant using the Black-Scholes option pricing model, assuming

dividends, and using the weighted average valuation assumptions noted in the following table. The risk-free rate is based on the US Treasury yield curve in effect at the time of grant. The expected life (estimated period of time outstanding) of the stock options granted was estimated using the "simplified" method as permitted by the SEC's Staff Accounting Bulletin

No.

110,

Share-Based Payment.

Expected volatility was based on the Company’s historical volatility during the

three

months ended

July 31, 2017

and

2016.

The below assumptions were used to determine the weighted average per share fair value of

$1.10

for stock options granted during the

three

months ended

July 31, 2016.

options were granted during the

three

months ended

July 31, 2017.

	Three months ended July 31,
	2017		2016

Risk-free interest rate		N/A		1.3	%
Expected dividend yield		N/A		0.0	%
Expected life (in years)		N/A		5.5
Expected volatility		N/A		85.6	%

A summary of stock options under our stock incentive plans is detailed in the following table.

						Weighted
						Average
				Weighted		Remaining
	Shares			Average		Contractual
	Underlying			Exercise		Term
	Options			Price		(In Years)
Outstanding as of April 30, 2017		237,214		$	14.64		7.6
Granted		-		$	-
Exercised		-		$	-
Cancelled/forfeited		(6,910	)	$	161.18
Outstanding as of July 31, 2017		230,304		$	10.24		7.6
Exercisable as of July 31, 2017		128,641		$	16.10		6.3

As of

July 31, 2017,

the total intrinsic value of outstanding and exercisable options was approximately

$5,000

and

$4,000,

respectively. As of

July 31, 2017,

approximately

100,323

additional options were unvested, which had

intrinsic value and a weighted average remaining contractual term of

9.2

years. There was approximately

$69,000

and

$83,000

of total recognized compensation cost related to stock options during each of the

three

months ended

July 31, 2017

and

2016,

respectively. As of

July 31, 2017,

there was approximately

$0.1

million of total unrecognized compensation cost related to non-vested stock options granted under the plans. This cost is expected to be recognized over a weighted-average period of

0.4

years. The Company typically issues newly authorized but unissued shares to satisfy option exercises under these plans.

(b) Restricted Stock

Compensation expense for non-vested restricted stock is generally recorded based on its market value on the date of grant and recognized ratably over the associated service and performance period. During the

three

months ended

July 31, 2017,

the Company granted

114,584

shares subject to service-based vesting requirements and

shares subject to performance-based vesting requirements. The achievement or vesting requirement of the performance-based grants is tied to the Company’s total shareholder return (“TSR”) relative to the total shareholder return of

three

alternative energy Exchange Traded Funds as measured over a specific performance period.

vesting of the relevant shares will occur in instances where the Company’s TSR for the relevant period is below

80%

of the peer group. However, additional opportunities to vest some or all of a portion of the shares in a subsequent period

may

occur. Compensation expense for these awards with market-based vesting is calculated based on the estimated fair value as of the grant date utilizing a Monte Carlo simulation model and is recognized over the service period on a straight-line basis.

Restricted stock issued and unvested as of

July 31, 2017

included

12,000

shares of unvested restricted stock subjected to performance-based vesting requirements.

A summary of non-vested restricted stock under our stock incentive plans is as follows:

				Weighted
	Number			Average Price per
	of Shares			Share

Issued and unvested at April 30, 2017		103,412		$	3.99
Granted		114,584		$	1.40
Vested		(70,650	)	$	4.55
Cancelled/forfeited		(125	)	$	1.40
Issued and unvested at July 31, 2017		147,221		$	2.04

There was approximately

$22,000

and

$0.1

million of total recognized compensation cost related to restricted stock for the

three

months ended

July 31, 2017

and

2016,

respectively. As of

July 31, 2017,

there was approximately

$0.2

million of total unrecognized compensation cost related to unvested restricted stock granted under our plans. This cost is expected to be recognized over a weighted average period of

1.5

years.

During the

three

months ended

July 31, 2017

and

2016,

22,016

and

447

shares, respectively, of common stock were purchased by the Company from employees to pay taxes related to the vesting of restricted stock.

Note 8 - Fair Value Measurements

3 Months Ended

Jul. 31, 2017

Notes to Financial Statements

Fair Value Disclosures [Text Block]

(

) Fair Value Measurements

The Company measures and reports certain financial and non-financial assets and liabilities on a fair value basis. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). GAAP specifies a

three

-level hierarchy that is used when measuring and disclosing fair value. The fair value hierarchy gives the highest priority to quoted prices available in active markets (i.e., observable inputs) and the lowest priority to data lacking transparency (i.e., unobservable inputs). An instrument’s categorization within the fair value hierarchy is based on the lowest level of significant input to its valuation. The following is a description of the

three

hierarchy levels.

Level 1	Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Active markets are considered to be those in which transactions for the assets or liabilities occur in sufficient frequency and volume to provide pricing information on an ongoing basis.

Level 2	Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. This category includes quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in inactive markets.

Level 3	Unobservable inputs are not corroborated by market data. This category is comprised of financial and non-financial assets and liabilities whose fair value is estimated based on internally developed models or methodologies using significant inputs that are generally less readily observable from objective sources.

Transfers into or out of any hierarchy level are recognized at the end of the reporting period in which the transfers occurred. There were

transfers between any levels during the

three

months ended

July

31,

2017

and

2016.

The following information is provided to help readers gain an understanding of the relationship between amounts reported in the accompanying consolidated financial statements and the related market or fair value. The disclosures include financial instruments and derivative financial instruments, other than investment in affiliates.

Following are descriptions of the valuation methodologies used to measure material assets and liabilities at fair value and details of the valuation models, key inputs to those models and significant assumptions utilized.

Warrant Liabilities

The fair value of the Company's warrant liabilities (refer to Note

) recorded in the Company's financial statements is determined using the Black-Scholes option pricing model and the quoted price of the Company's common stock in an active market, volatility and expected life, is a Level

measurement. Volatility is based on the actual market activity of the Company's stock. The expected life is based on the remaining contractual term of the warrants and the risk free interest rate is based on the implied yield available on U.S. Treasury Securities with a maturity equivalent to the warrants' expected life.

The following table presents financial assets and liabilities measured at fair value on a recurring basis as of

July

31,

2017.

	Total Carrying Value in Consolidated Balance Sheet		Quoted prices in active markets for identical assts or liabilities (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)

Warrant liabilities	$	286	$	-	$	-	$	286

The following table presents financial assets and liabilities measured at fair value on a recurring basis as of

April

30,

2017.

	Total Carrying Value in Consolidated Balance Sheet		Quoted prices in active markets for identical assts or liabilities (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)

Warrant liabilities	$	323	$	-	$	-	$	323

The following table provides a summary of changes in fair value of the Company’s warrant liabilities held at

July 31, 2017.

Fair Value Measurement Using Significant Unobservable Inputs ( Level 3)

	Total
	Warrant
	Liability
	(in thousands)

Fair value – April 30, 2016	$	-
Issuance		1,814
Transfers		-
Change in fair value		(1,491	)
Fair value – April 30, 2017	$	323

Change in fair value		(37	)
Fair value – July 31, 2017	$	286

There were

re-measured assets or liabilities at fair value on a non-recurring basis during the

three

months ended

July 31, 2017

and

2016,

respectively.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Note 9 - Commitments and Contingencies	3 Months Ended
Note 9 - Commitments and Contingencies	Jul. 31, 2017
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	( 9 ) Commitments and Contingencies (a) Litigation Shareholder Litigation and Demands The Company and certain of its current and former directors and officers are defendants in a derivative lawsuit filed on March 18, 2015 in the United States District Court for the District of New Jersey captioned Labare v. Dunleavy, et. al., Case No. 3:15 -cv- 01980 -FLW-LHG. The derivative complaint alleges claims for breach of fiduciary duty, abuse of control, gross mismanagement and unjust enrichment relating to the now terminated agreement between Victorian Wave Partners Pty. Ltd. (VWP) and the Australian Renewable Energy Agency (ARENA) for the development of a wave power station. The derivative complaint seeks unspecified monetary damages and other relief. On July 10, 2015, a second derivative lawsuit, captioned Rywolt v. Dunleavy, et al., Case No. 3:15 -cv- 05469, was filed by another shareholder against the same defendants in the United States District Court for the District of New Jersey alleging similar claims for breach of fiduciary duty, gross mismanagement, abuse of control, and unjust enrichment relating to the now terminated agreement between VWP and ARENA. The Rywolt complaint also seeks unspecified monetary damages and other relief. On February 8, 2016, the Court issued an order consolidating the Labare and Rywolt actions, appointing co-lead plaintiffs and lead counsel, and ordering a consolidated amended complaint to be filed within 30 days of the order. On March 9, 2016, the co-lead plaintiffs filed an amended complaint consolidating their claims and seeking unspecified monetary damages and other relief. On April 21, 2016, a third derivative lawsuit, captioned LaCalamito v. Dunleavy, et al., Case No. 3:16 -cv- 02249, was filed by another shareholder against certain current and former directors and officers of the Company in the United States District Court for the District of New Jersey alleging similar claims for breach of fiduciary duty relating to the now terminated agreement between VWP and ARENA. The LaCalamito complaint seeks unspecified monetary damages and other relief. The Company has not been formally served and has not yet responded to the complaint. On June 9, 2016, a fourth derivative lawsuit, captioned Pucillo v. Dunleavy, et al., was filed by another shareholder against certain current and former directors and officers of the Company in the United States District Court for the District of New Jersey alleging similar claims for breach of fiduciary duty, unjust enrichment, and abuse of control relating to the now terminated agreement between VWP and ARENA. The Pucillo complaint seeks unspecified monetary damages and other relief. On August 2, 2016, the parties in the Pucillo lawsuit filed a Stipulation and Proposed Order pursuant to which: (i) the defendants agreed to accept service of the Pucillo complaint; (ii) the parties agreed to stay the Pucillo action pending the filing and resolution of a motion to consolidate the Pucillo action with the Labar e and Rywolt actions; and (iii) the parties agreed that the defendants shall not be required to respond to the Pucillo complaint during the pendency of the stay. The Court approved the Stipulation on August 3, 2016. On October 25, 2016, the Court approved and entered a Stipulation and Order that, among other things, (i) consolidated the four derivative actions; (ii) identified plaintiff Pucillo as the lead plaintiff in the consolidated actions; and (iii) stayed the consolidated actions pending the settlement hearing scheduled for November 14, 2016 in the securities class action and further order of the Court. During the month of August, 2017, the Company tentatively reached a settlement with the plaintiff subject to final documentation. The settlement, once finalized and if approved by the court, provides, among other things, for a settlement payment by or on behalf of the Company of $350,000, of which the Company’s insurer would pay the complete amount of $350,000. As a result, the Company has accrued $350,000 related to this matter as a probable and reasonably estimable loss contingency during the three months ended July 31, 2017. The Company also recorded a receivable of $350,000 from its insurance carrier with the offset to the statement of operations. On May 26, 2017, an attorney claiming to represent two stockholders sent the Company’s Board of Directors a Stockholder Litigation Demand letter (“Stockholder Demand”). The Stockholder Demand alleges that the voting of shares for the 1 -for- 10 reverse stock split at the 2015 annual meeting of stockholders held on October 22, 2015 was not properly counted, and further alleges that, although the Company reported the reverse stock split as having been passed, if the vote was properly counted the reverse stock split would not have been approved. The Stockholder Demand requests the Board of Directors either to deem the reverse stock split as ineffective and disclose the same or to seek a proper and effective stockholder ratification of the reverse stock split. In addition, the Stockholder Demand requests the Board of Directors to adopt and implement adequate internal controls and systems to prevent the alleged improper voting from recurring. On June 23, 2017, the Company responded to the Stockholder Demand, explained the procedures that were followed for the 2015 annual meeting of stockholders and provided the Oath of the Inspector of Elections and the Certificate of the Inspector of Elections that certified as accurate the results of the voting at the meeting including voting on the reverse stock split proposal. On June 26, 2017, the attorney representing the alleged stockholders replied to the Company’s response, further alleged that the proxy statement underlying the 2015 annual meeting provided voting instructions that misled the stockholders regarding whether their brokers could vote on the reverse stock split proposal, and renewed their requests of the Board. On July 24, 2017, the Company provided an additional response to the Stockholders Demand, denied the allegations, and declined to take any of the actions requested. Employment Litigation On June 10, 2014, the Company announced that it had terminated Charles Dunleavy as its Chief Executive Officer and as an employee of the Company for cause, effective June 9, 2014, and that Mr. Dunleavy had also been removed from his position as Chairman of the Board of Directors. On June 17, 2014, Mr. Dunleavy wrote to the Company stating that he had retained counsel to represent him in connection with an alleged wrongful termination of his employment. On July 28, 2014, Mr. Dunleavy resigned from the Board and the boards of directors of the Company's subsidiaries. The Company and Mr. Dunleavy have agreed to suspend his alleged employment claims pending resolution of the shareholder litigation, and have since agreed to continue to the suspension pending resolution of the derivatives litigation. Except for the pending settlement noted previously, we have not established any provision for losses relating to these claims and pending litigation. Due to the stages of these proceedings, and considering the inherent uncertainty of these claims and litigation, at this time we are not able to predict or reasonably estimate whether we have any possible loss exposure or the ultimate outcome of these claims. (b) Regulatory Matters SEC Investigation On February 4, 2015, the Company received a subpoena from the SEC requesting information related to the VWP Project. The Company has provided information to the SEC in response to that subpoena. As part of the same investigation, on July 12, 2016, the SEC issued second subpoena requesting information related to the Company’s April 4, 2014 public offering. The Company has provided information to the SEC in response to that subpoena. The SEC investigation is ongoing and the Company continues to cooperate with the SEC in its investigation. We are unable to predict what action, if any, might be taken by the SEC or its staff as a result of this investigation or what impact, if any, the cost of responding to the SEC’s investigation or its ultimate outcome might have on our financial position, results of operations or liquidity. We have not established any provision for losses relating to this matter. Spain IVA (sales tax) In June 2012, the Company received notice that the Spanish tax authorities are inquiring into its 2010 IVA (value-added tax) filing for which the Company benefitted from the offset of approximately $0.3 million of input tax. The Company believes that the inquiry will find that the tax credit was properly claimed and, therefore, no liability has been recorded. The Company issued two letters of credit totaling €0.3 million ( $0.3 million) at the request of the Spanish tax authorities. On January 31, 2017 the Company has received $0.2 million from the Spanish tax authorities as a result of the conclusion of the inquiry. In addition, during February 2017, the Spanish tax authorities approved of the release of the two outstanding letters of credit. Spain Income Tax Audit The Company is currently undergoing an income tax audit in Spain for the period from 2008 to 2014, when its Spanish branch was closed. The branch reported net operating losses for each of the years reported. It is anticipated that the Company will be assessed a penalty relating to these tax years for these losses. The Company has estimated this penalty to be $132,000 , and as such, for the period ended April 30, 2017 and July 31, 2017, the Company has recorded $132,000 for this penalty to Accrued expenses in its balance sheet.

Note 10 - Income Taxes	3 Months Ended
Note 10 - Income Taxes	Jul. 31, 2017
Notes to Financial Statements
Income Tax Disclosure [Text Block]	( 10 ) Income Taxes The Company did not recognize any consolidated income tax benefit (expense) during the three month periods ended July 31, 2017 and 2016. The Company has recorded a valuation allowance to reduce its net deferred tax asset to an amount that is more likely than not to be realized in future years. Accordingly, the benefit of the net operating loss that would have been recognized was offset by changes in the valuation allowance. The Company applies the guidance issued by the FASB for the accounting and reporting of uncertain tax positions. The guidance requires the Company to recognize in its consolidated financial statements the impact of a tax position if that position is more likely than not to be sustained upon examination, based on the technical merits of the position. We are currently undergoing an income tax audit in Spain for the period from 2008 to 2014, when our Spanish branch was closed. The branch reported net operating losses for each of the years reported. It is anticipated that we will be assessed a penalty relating to these tax years for these losses. We have estimated this penalty to be $132,000 , and as such, for the period ended April 30, 2017 and July 31, 2017, we have recorded $132,000 for this penalty to Accrued expenses in the Balance Sheet. At July 31, 2017 the Company had no other unrecognized tax positions. The Company does not expect any material increase or decrease in its income tax expense in the next twelve months, related to examinations or uncertain tax positions. U.S. federal and state income tax returns were audited through fiscal 2014 and fiscal 2010 respectively. Net operating loss and credit carry forwards since inception remain open to examination by taxing authorities, and will continue to remain open for a period of time after utilization.

Note 11 - Operating Segments and Geographic Information	3 Months Ended
Note 11 - Operating Segments and Geographic Information	Jul. 31, 2017
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	( 11 ) Operating Segments and Geographic Information The Company's business consists of one segment as this represents management's view of the Company's operations. The Company operates on a worldwide basis with one operating company in the US and operating subsidiaries in the UK and in Australia. Revenues and expenses are generally attributed to the operating unit that bills the customers. During the three months ended July 31, 2017 and 2016, the Company’s primary business operations were in North America.

Significant Accounting Policies (Policies)

3 Months Ended

Jul. 31, 2017

Accounting Policies [Abstract]

Basis of Accounting, Policy [Policy Text Block]

b)	Basis of Presentation

-Q and Article

of Regulation S-

Accordingly, they do

not

-K for the year ended

April 30, 2017

filed with the Securities and Exchange Commission (“SEC”) and elsewhere in this Form

-Q.

Liquidity, Policy [Policy Text Block]

c)	Liquidity/Going Concern

$190.0

million as of

July 31, 2017.

As of

July 31, 2017,

the Company had approximately

$11.4

million in cash and cash equivalents on hand. The Company generated revenues of

$0.2

million during each of the

three

months ended

July 31, 2017

and

2016.

Based on the Company’s cash and cash equivalents and marketable securities as of

July 31, 2017,

the Company believes that it will be able to finance its capital requirements and operations into the quarter ending

July 31, 2018.

not

Management is evaluating different strategies to obtain the required additional funding for future operations. These strategies

may

include, but are

not

assurance that any of these future-funding efforts will be successful.

In fiscal

2017

and the

three

months ended

July 31, 2017,

not

limited to, risks from lack of available financing and insufficient capital, performance of PowerBuoys,

four

equity financing arrangements during the year ended

April 30, 2017

and

three

months ended

July 31, 2017.

The Company does

not

obtained when needed, the Company

may

cause it to scale back, delay or eliminate some or all of its product development activities and/or reduce the scope of or cease its operations.

June 2, 2016,

the Company entered into a securities purchase agreement, which was amended on

June 7, 2016 (

as amended, the “Purchase Agreement”) with certain institutional purchasers (the

“June

Purchasers”). Pursuant to the terms of the

June

Purchase Agreement, the Company sold an aggregate of

417,000

shares of Common Stock together with warrants to purchase up to an aggregate of

145,952

shares of Common Stock. Each share of Common Stock was sold together with a warrant to purchase

0.35

of a share of Common Stock at a combined purchase price of

$4.60.

The net proceeds to the Company from the offering were approximately

$1.7

$6.08

per share, became exercisable on

December 3, 2016 (

“Initial Exercise Date”), and will expire

five

years following the Initial Exercise Date.

The Company paid the placement agents approximately

$0.1

million as placement agent fees in connection with the sale of securities in the offering. The Company also reimbursed the placement agents

$35,000

for their out of pocket and legal expenses in connection with the offering.

July 22, 2016,

the Company entered into the Second Amendment to the Purchase Agreement (the “Second Amended Purchase Agreement”) with certain purchasers (the

“July

Purchasers”). Pursuant to the terms of the Second Amended Purchase Agreement, the Company sold an aggregate of

595,000

shares of Common Stock together with warrants to purchase up to an aggregate of

178,500

shares of Common Stock. Each share of Common Stock was sold together with a warrant to purchase

0.30

of a share of Common Stock at a combined purchase price of

$6.75.

The net proceeds to the Company from the offering were approximately

$3.6

$9.36

per share. The Warrants will expire on the

fifth

(

5th

) anniversary of the initial date of issuance.

October 19, 2016,

the Company sold

2,760,000

shares of common stock at a price of

$2.75

per share, which includes the sale of

360,000

$6.9

million, after deducting underwriter fees and offering expenses payable by the Company.

May 2, 2017,

the Company sold

6,192,750

shares of common stock at a price of

$1.30

per share, which includes the sale of

807,750

$7.2

million, after deducting underwriter fees and offering expenses payable by the Company.

may

not

be available in amounts or on terms acceptable to the Company, or at all. If the Company is unable to obtain required financing, it

may

be forced to cease operations.

Consolidation, Policy [Policy Text Block]

(a) Consolidation

Use of Estimates, Policy [Policy Text Block]

(b) Use of Estimates

The current economic environment, particularly the macroeconomic pressures in certain European countries, has increased the degree of uncertainty inherent in those estimates and assumptions.

Revenue Recognition, Policy [Policy Text Block]

The Company has

two

may

In addition, recognition of revenue (and the related costs)

may

have a significant effect on revenue for the periods involved. Upon anticipating a loss on a contract, the Company recognizes the full amount of the anticipated loss in the current period.

Unbilled receivables represent expenditures on contracts, plus applicable profit margin,

not

yet billed. Unbilled receivables are normally billed and collected within

one

Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]

(d) Cash, Cash Equivalents, Restricted Cash and Security Agreements

Cash and Cash Equivalents

The Company considers all highly liquid investments with a maturity of

three

not

100%

of the bank’s total obligations under the agreement.

	July 31, 2017		April 30, 2017
	(in thousands)

Checking and savings accounts	$	4,400	$	4,241
Overnight repurchase account		7,014		4,180
	$	11,414	$	8,421

Restricted Cash and

Security Agreements

A portion of the Company’s cash is restricted under the terms of

two

security agreements.

one

of the Company's subsidiaries, under a credit facility established by Barclays Bank for OPT LTD. The credit facility is approximately

€0.3

million (

$0.3

million) and carries a fee of

per annum of the amount of any such obligations issued by Barclays Bank. The credit facility does

not

have an expiration date, but is cancelable at the discretion of the bank. As of

July 31, 2017,

there was

€0.3

million (

$0.3

million) in letters of credit outstanding under this agreement.

The

second

January 31, 2025,

and is cancelable at the discretion of the bank. Restricted cash includes the following:

	July 31, 2017		April 30, 2017
	(in thousands)

Barclay's Bank Agreement	$	361	$	334
Santander Bank		154		154
	$	515	$	488

	July 31, 2017		April 30, 2017
	(in thousands)

Cash and cash equivalents	$	11,414	$	8,421
Restricted cash- short term		361		334
Restricted cash- long term		154		154
	$	11,929	$	8,909

Marketable Securities, Policy [Policy Text Block]

(e) Marketable Securities

Marketable securities with original maturities longer than

three

months but that mature in less than

one

July 31, 2017

and

April 30, 2017,

all of the Company’s investments were classified as held-to-maturity.

Foreign Currency Transactions and Translations Policy [Policy Text Block]

(f) Foreign Exchange Gains and Losses

may

Property, Plant and Equipment, Policy [Policy Text Block]

(g) Property and Equipment

Property and equipment is stated at cost, less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives (

three

seven

may

not

Concentration Risk, Credit Risk, Policy [Policy Text Block]

(h) Concentration of Credit Risk

not

believe that it is exposed to any significant risks related to its cash accounts, money market funds or certificates of deposit.

The table below shows the percentage of the Company's revenues derived from customers whose revenues accounted for at least

10%

of the Company's consolidated revenues for at least

one

of the periods indicated:

	Three months ended July 31,
Customer	2017			2016

Mitsui Engineering & Shipbuilding		67	%		100	%
U.S. Department of Defense Office of Naval Research		33	%		-
		100	%		100	%

The loss of, or a significant reduction in revenues from a current customer could significantly impact the Company's financial position or results of operations. The Company does

not

require its customers to maintain collateral.

Warrant Liability, Policy [Policy Text Block]

(i) Warrant Liabilities

Earnings Per Share, Policy [Policy Text Block]

(j) Net Loss per Common Share

In computing diluted net loss per share, options to purchase shares of common stock, warrants on common stock and non-vested restricted stock issued to employees and non-employee directors, totaling

701,977

for the

three

months ended

July 31, 2017

and

711,453

for the

three

months ended

July 31, 2016,

were excluded from each of the computations as the effect would be anti-dilutive due to the Company's losses.

Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]

(

)

Share-Based Compensation

three

months ended

July 31, 2017

and

2016

was approximately

$0.1

million and

$0.2

million, respectively. The following table summarizes share-based compensation related to the Company’s share-based plans by expense category for the

three

months ended

July 31, 2017

and

2016:

	Three months ended July 31,
	2017		2016
	(in thousands)

Product development	$	13	$	53
Selling, general and administratvie		78		165
Total share-based compensation expense	$	91	$	218

New Accounting Pronouncements, Policy [Policy Text Block]

(l) Recently Issued Accounting Standards

May 2014,

the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”)

No.

2014

09,

“

Revenue from Contracts with Customers (Topic

606

).”

ASU

2014

five

one

-year deferral of the effective date for the new revenue standard. Public companies should now apply the guidance in ASU

2014

to annual reporting periods beginning after

December

15,

2017

and interim periods within those annual periods. Earlier application is permitted only as of annual reporting periods beginning after

December

15,

2016,

including interim periods within that annual period. As such, the Company is required to adopt this standard effective in fiscal

2019,

which begins

May 1, 2018.

Companies

may

use either a full retrospective or a modified retrospective approach to adopt ASU

2014

09.

The Company has

not

yet completed its final review of the impact of this guidance; however the Company anticipates applying the modified retrospective method upon adoption of ASU

2014

May 1, 2018.

The impact to the Company could be affected by the nature and terms of potential future contracts with customers, as those contracts

may

have terms that differ from the Company’s current contracts.

August 2014,

the FASB issued ASU

2014

15,

“Disclosure of Uncertainties about an Entity’s Ability

to Continue as a Going Concern”,

first

annual period ending after

December 15, 2016,

and interim periods thereafter. Early application is permitted. The Company adopted ASU

2014

for the fiscal year

2017.

The Company’s addition of the standard did

not

have a material impact on its disclosures.

See section (c) “Liquidity/Going Concern” within Note (

) “Background and Liquidity” of the consolidated financial statements included in this Quarterly Report on Form

-Q for further discussion on the Company’s ability to continue as a going concern.

January 2016,

the FASB issued ASU

No.

2016

01,

“Recognition and Measurement of Financial Assets and Financial Liabilities”,

December 15, 2017,

including interim periods within those fiscal years. The Company will evaluate the effect of ASU

2016

for future periods as applicable.

February 2016,

the FASB issued ASU

No.

2016

02,

“Leases (Topic

842

).” The new standard establishes a right-of-use (ROU) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than

months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. ASU

2016

is effective for annual periods beginning after

December

15,

2018,

2016

will have on its consolidated financial statements and disclosures and has

not

yet determined the effect of the standard on its ongoing financial reporting at this time.

March 2016,

the FASB issued ASU

No.

2016

09,

“Compensation - Stock Compensation (Topic

718

)

”

The amendments of ASU

No.

2016

were issued as part of the FASB's Simplification initiative focused on improving areas of GAAP for which cost and complexity

may

No.

2016

is effective for fiscal years beginning after

December 15, 2016,

and interim periods within those annual periods. The Company adopted ASU

2016

May 1, 2017.

Certain of the amendments are applied using a modified retrospective transition method by means of a cumulative-effect adjustment to equity as of

May 1, 2017,

$10,000

on the date of initial adoption. In periods subsequent to adoption, a higher expense will be recognized earlier during the respective vesting periods of stock-based awards that are

not

forfeited. The Company expects that the income tax amendments within ASU

2016

will have

impact on its results of operations or cash flows because it is in a net operating loss position with a full valuation allowance.

August 2016,

the FASB issued ASU

2016

15,

“Statement of Cash Flows (Topic

230

): Classification

of Certain Cash Receipts and Cash Payments”,

providing additional guidance on

eight

specific cash flow classification issues. The goal of the ASU is to reduce diversity in practice of classifying certain items. The amendments in the ASU are effective for

fiscal years beginning after

December 15, 2017,

and interim periods within those fiscal years and early adoption is permitted. The Company has evaluated the effect ASU

2016

will have on its consolidated financial statements and disclosures and has determined the standard will have

impact on its ongoing financial reporting at this time.

November 2016,

the FASB issued ASU

2016

18,

“Statement of Cash Flows (Topic

230

): Restricted

Cash”,

fiscal years beginning after

December 15, 2017,

and interim periods within those fiscal years and early adoption is permitted. The Company has early adopted ASU

2016

effective

May 1, 2017.

In connection with the adoption of the standard the Company has used a retrospective transition method for each period presented in the statement of cash flows. The Company reclassified

$488,000

and

$300,000

of restricted cash to cash, cash equivalents and restricted cash, beginning of period for the period

April 30, 2017

and

April 30, 2016

in the statement of cash flows. The Company reclassified

$266,000

of restricted cash to cash, cash equivalents and restricted cash, end of period for the period ended

July 31, 2016

in the statement of cash flows.

Note 2 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Jul. 31, 2017

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	July 31, 2017		April 30, 2017
	(in thousands)

Checking and savings accounts	$	4,400	$	4,241
Overnight repurchase account		7,014		4,180
	$	11,414	$	8,421

Restrictions on Cash and Cash Equivalents [Table Text Block]

	July 31, 2017		April 30, 2017
	(in thousands)

Barclay's Bank Agreement	$	361	$	334
Santander Bank		154		154
	$	515	$	488

Schedule of Cash, Cash Equivalents, and Restricted Cash [Table Text Block]

	July 31, 2017		April 30, 2017
	(in thousands)

Cash and cash equivalents	$	11,414	$	8,421
Restricted cash- short term		361		334
Restricted cash- long term		154		154
	$	11,929	$	8,909

Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]

	Three months ended July 31,
Customer	2017			2016

Mitsui Engineering & Shipbuilding		67	%		100	%
U.S. Department of Defense Office of Naval Research		33	%		-
		100	%		100	%

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three months ended July 31,
	2017		2016
	(in thousands)

Product development	$	13	$	53
Selling, general and administratvie		78		165
Total share-based compensation expense	$	91	$	218

Note 3 - Marketable Securities (Tables)

3 Months Ended

Jul. 31, 2017

Current [Member]

Notes Tables

Marketable Securities [Table Text Block]

	July 31, 2017		April 30, 2017
	(in thousands)

Certificate of Deposit	$	25	$	25

Note 4 - Accrued Expenses (Tables)

3 Months Ended

Jul. 31, 2017

Notes Tables

Schedule of Other Assets and Other Liabilities [Table Text Block]

	July 31, 2017		April 30, 2017
	(in thousands)

Project costs	$	46	$	898
Contract loss reserve		298		238
Employee incentive payments		142		643
Accrued salary and benefits		420		484
Legal and accounting fees		358		478
Accrued taxes payable		132		132
Other		134		186
	$	1,530	$	3,059

Note 6 - Warrants (Tables)

3 Months Ended

Jul. 31, 2017

Notes Tables

Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table Text Block]

	July 31, 2017			July 31, 2016

Dividend rate		0.0%			0.0%
Risk-free rate		1.68%			1.00%
Expected life (years)	4.0	-	4.4	5.0	-	5.4
Expected volatility		140.3%			125.4%

Note 7 - Stock-based Compensation (Tables)

3 Months Ended

Jul. 31, 2017

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three months ended July 31,
	2017		2016

Risk-free interest rate		N/A		1.3	%
Expected dividend yield		N/A		0.0	%
Expected life (in years)		N/A		5.5
Expected volatility		N/A		85.6	%

Share-based Compensation, Activity [Table Text Block]

						Weighted
						Average
				Weighted		Remaining
	Shares			Average		Contractual
	Underlying			Exercise		Term
	Options			Price		(In Years)
Outstanding as of April 30, 2017		237,214		$	14.64		7.6
Granted		-		$	-
Exercised		-		$	-
Cancelled/forfeited		(6,910	)	$	161.18
Outstanding as of July 31, 2017		230,304		$	10.24		7.6
Exercisable as of July 31, 2017		128,641		$	16.10		6.3

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

				Weighted
	Number			Average Price per
	of Shares			Share

Issued and unvested at April 30, 2017		103,412		$	3.99
Granted		114,584		$	1.40
Vested		(70,650	)	$	4.55
Cancelled/forfeited		(125	)	$	1.40
Issued and unvested at July 31, 2017		147,221		$	2.04

Note 8 - Fair Value Measurements (Tables)

3 Months Ended

Jul. 31, 2017

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Total Carrying Value in Consolidated Balance Sheet		Quoted prices in active markets for identical assts or liabilities (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)

Warrant liabilities	$	286	$	-	$	-	$	286

	Total Carrying Value in Consolidated Balance Sheet		Quoted prices in active markets for identical assts or liabilities (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)

Warrant liabilities	$	323	$	-	$	-	$	323

Changes on Value of Warrant Liability [Table Text Block]

Fair Value Measurement Using Significant Unobservable Inputs ( Level 3)

	Total
	Warrant
	Liability
	(in thousands)

Fair value – April 30, 2016	$	-
Issuance		1,814
Transfers		-
Change in fair value		(1,491	)
Fair value – April 30, 2017	$	323

Change in fair value		(37	)
Fair value – July 31, 2017	$	286

Note 1 - Background, Basis of Presentation and Liquidity (Details Textual)					3 Months Ended		12 Months Ended
	May 02, 2017 USD ($) $ / shares shares	Oct. 19, 2016 USD ($) $ / shares shares	Jul. 22, 2016 USD ($) $ / shares shares	Jun. 02, 2016 USD ($) $ / shares shares	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Apr. 30, 2017 USD ($)
Retained Earnings (Accumulated Deficit)					$ (190,043,000)		$ (187,370,000)
Cash and Cash Equivalents, at Carrying Value					11,414,000		$ 8,421,000
Proceeds from Issuance or Sale of Equity						$ 5,261,000
Revenues					$ 195,000	$ 202,000
Number of Financing Agreements Closed					4		4
Purchase Agreement [Member]
Proceeds from Issuance or Sale of Equity			$ 3,600,000	$ 1,700,000
Class of Warrant or Right, Exercise Price of Warrants or Rights \| $ / shares			$ 9.36	$ 6.08
Class of Warrant or Right, Expiration Period			5 years	5 years
Stock Issued During Period, Shares, New Issues \| shares			595,000	417,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights \| shares			178,500	145,952
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right \| shares			0.3	0.35
Price Per Common Stock and Warrant \| $ / shares			$ 6.75	$ 4.60
Purchase Agreement [Member] \| Placement Agents [Member] \| Placement Agent Fees [Member]
Payments of Stock Issuance Costs				$ 100,000
Purchase Agreement [Member] \| Placement Agents [Member] \| Reimbursement of Out of Pocket and Legal Expenses [Member]
Payments of Stock Issuance Costs				$ 35,000
Offering Agreement [Member]
Share Price \| $ / shares	$ 1.30	$ 2.75
Stock Issued During Period, Shares, New Issues \| shares	6,192,750	2,760,000
Over-Allotment Option [Member]
Proceeds from Issuance or Sale of Equity	$ 7.20	$ 6,900,000
Stock Issued During Period, Shares, New Issues \| shares	807,750	360,000

Note 2 - Summary of Significant Accounting Policies (Details Textual) € in Millions	3 Months Ended
	Jul. 31, 2017 USD ($) shares	Jul. 31, 2016 USD ($) shares	Jul. 31, 2017 EUR (€)	May 01, 2017 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2016 USD ($)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount \| shares	701,977	711,453
Allocated Share-based Compensation Expense	$ 91,000	$ 218,000
Cumulative Effect of New Accounting Principle in Period of Adoption
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	11,929,000	9,291,000			$ 8,909,000	$ 7,030,000
Accounting Standards Update 2016-18 [Member] \| Restatement Adjustment [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 266,000			$ 488,000	$ 300,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (10,000)
Retained Earnings [Member] \| Accounting Standards Update 2016-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ (10,000)
Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Maximum [Member]
Property, Plant and Equipment, Useful Life	7 years
Barclays Bank [Member]
Line of Credit Facility, Commitment Fee Percentage	1.00%
Long-term Line of Credit	$ 300,000		€ 0.3

Note 2 - Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017
Cash and cash equivalents	$ 11,414	$ 8,421
Checking and Savings Accounts [Member]
Cash and cash equivalents	4,400	4,241
Overnight Repurchase Account [Member]
Cash and cash equivalents	$ 7,014	$ 4,180

Note 2 - Summary of Significant Accounting Policies - Cash Restricted Under Security Agreements (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017
Restricted cash	$ 515	$ 488
Barclays Bank Agreement [Member]
Restricted cash	361	334
Santander Bank [Member]
Restricted cash	$ 154	$ 154

Note 2 - Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017	Jul. 31, 2016	Apr. 30, 2016
Cash and Cash Equivalents, at Carrying Value	$ 11,414	$ 8,421
Restricted cash- short term	361	334
Restricted cash- long term	154	154
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 11,929	$ 8,909	$ 9,291	$ 7,030

Note 2 - Summary of Significant Accounting Policies - Revenues by Major Customers (Details) - Customer Concentration Risk [Member] - Sales Revenue, Net [Member]	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Revenues, percentage	100.00%	100.00%
Mitsui Engineering and Ship Building [Member]
Revenues, percentage	67.00%	100.00%
U.S. Department of Defense Office of Naval Research [Member]
Revenues, percentage	33.00%

Note 2 - Summary of Significant Accounting Policies - Share-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Allocated Share-based Compensation Expense	$ 91	$ 218
Product Development [Member]
Allocated Share-based Compensation Expense	13	53
Selling, General and Administrative Expenses [Member]
Allocated Share-based Compensation Expense	$ 78	$ 165

Note 3 - Marketable Securities - Marketable Securities That Mature Within One Year (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017	Apr. 30, 2016
Marketable securities	$ 25	$ 25	$ 25

Note 4 - Accrued Expenses - Accrued Expenses (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017
Project costs	$ 46	$ 898
Contract loss reserve	298	238
Employee incentive payments	142	643
Accrued salary and benefits	420	484
Legal and accounting fees	358	478
Accrued taxes payable	132	132
Other	134	186
Accrued expenses total	$ 1,530	$ 3,059

Note 5 - Deferred Credits Payable (Details Textual) $ in Thousands	Jul. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2001 USD ($) T Rate
Customer Advances or Deposits, Noncurrent \| $			$ 600
Deferred Credits Payable Option Details \| T			500,000
Deferred Credits Payable Market Discount Rate \| Rate			30.00%
Deferred Credits Payable Market Liquidated Damages Rate \| Rate			30.00%
Customer Advances and Deposits, Current \| $	$ 600	$ 600

Note 6 - Warrants (Details Textual) - USD ($)			3 Months Ended
Note 6 - Warrants (Details Textual) - USD ($)	Jul. 22, 2016	Jun. 02, 2016	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2017
Fair Value Adjustment of Warrants			$ (37,000)	$ 752,000
Warrant [Member]
Derivative Liability, Current			$ 300,000		$ 300,000
Purchase Agreement [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 9.36	$ 6.08
Class of Warrant or Right, Expiration Period	5 years	5 years
Stock Issued During Period, Shares, New Issues	595,000	417,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	178,500	145,952
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	0.3	0.35
Price Per Common Stock and Warrant	$ 6.75	$ 4.60

Note 6 - Warrants - Fair Value Assumptions for Warrants (Details) - Warrant [Member]	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Dividend rate	0.00%	0.00%
Risk-free rate	1.68%	1.00%
Expected life (years) (Year)
Expected volatility	140.30%	125.40%
Minimum [Member]
Dividend rate
Risk-free rate
Expected life (years) (Year)	4 years	5 years
Expected volatility
Maximum [Member]
Dividend rate
Risk-free rate
Expected life (years) (Year)	4 years 146 days	5 years 146 days
Expected volatility

Note 7 - Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 1.10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 5,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 4,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	100,323
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	9 years 73 days
Allocated Share-based Compensation Expense	$ 91,000	$ 218,000
Treasury Stock [Member]
Treasury Stock, Shares, Acquired	22,016	447
Employee Stock Option [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	146 days
Allocated Share-based Compensation Expense	$ 69,000	$ 83,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	100,000
Restricted Stock [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 200,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 182 days
Allocated Share-based Compensation Expense	$ 22,000	$ 100,000
Restricted Stock [Member] \| Service-based Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	114,584
Restricted Stock [Member] \| Performance-based vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	12,000

Note 7 - Stock-based Compensation - Fair Value Assumptions for Options (Details) - Employee Stock Option [Member]	3 Months Ended
	Jul. 31, 2016
Risk-free interest rate	1.30%
Expected dividend yield	0.00%
Expected life (in years) (Year)	5 years 182 days
Expected volatility	85.60%

Note 7 - Share-based Compensation Plans - Stock Options Under the Plans (Details)	3 Months Ended
	Jul. 31, 2017 $ / shares shares
Beginning Balance, shares underlying options (in shares) \| shares	237,214
Beginning Balance, weighted average exercise price (in dollars per share) \| $ / shares	$ 14.64
Ending Balance, weighted average exercise price (in dollars per share) \| $ / shares	$ 10.24
Balance, weighted average remaining contractual term (Year)	7 years 219 days
Granted (in shares) \| shares
Granted (in dollars per share) \| $ / shares
Exercised (in shares) \| shares
Exercised (in dollars per share) \| $ / shares
Cancelled/forfeited (in shares) \| shares	(6,910)
Cancelled/forfeited (in dollars per share) \| $ / shares	$ 161.18
Ending Balance, shares underlying options (in shares) \| shares	230,304
Exercisable, shares underlying options (in shares) \| shares	128,641
Exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 16.10
Exercisable, weighted average remaining contractual term (Year)	6 years 109 days

Note 7 - Share-based Compensation Plans - Non-vested Restricted Stock Under the Plans (Details) - Non-vested Restricted Stock [Member]	3 Months Ended
	Jul. 31, 2017 $ / shares shares
Beginning Balance, issued and unvested (in shares) \| shares	103,412
Beginning Balance, issued and unvested (in dollars per share) \| $ / shares	$ 3.99
Ending Balance, issued and unvested (in dollars per share) \| $ / shares	$ 2.04
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares	114,584
Granted (in dollars per share) \| $ / shares	$ 1.40
Vested (in shares) \| shares	(70,650)
Vested (in dollars per share) \| $ / shares	$ 4.55
Cancelled/forfeited (in shares) \| shares	(125)
Cancelled/forfeited (in dollars per share) \| $ / shares	$ 1.40
Ending Balance, issued and unvested (in shares) \| shares	147,221

Note 8 - Fair Value Measurements (Details Textual) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Liabilities, Fair Value Adjustment	$ 0	$ 0
Assets, Fair Value Adjustment	$ 0	$ 0

Note 8 - Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Apr. 30, 2017
Warrant liabilities	$ 286	$ 323
Warrant [Member] \| Fair Value, Measurements, Recurring [Member] \| Reported Value Measurement [Member]
Warrant liabilities	286	323
Warrant [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Warrant liabilities
Warrant [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Warrant liabilities
Warrant [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Warrant liabilities	$ 286	$ 323

Note 8 - Fair Value Measurements - Changes on Value of Warrant Liability (Details) - Warrant [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2017	Apr. 30, 2017
Fair value	$ 323
Issuance		1,814
Transfers
Change in fair value	(37)	(1,491)
Fair value	$ 286	$ 323

Note 9 - Commitments and Contingencies (Details Textual) € in Millions		1 Months Ended		3 Months Ended	12 Months Ended
	Oct. 22, 2015	Aug. 31, 2017 USD ($)	Jun. 30, 2012 USD ($)	Jul. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jan. 31, 2017 USD ($)	Jun. 30, 2012 EUR (€)
Estimated Litigation Liability, Current				$ 350,000
Tax Authority, Spain [Member] \| Foreign Tax Authority [Member]
Input Tax			$ 300,000
Letters of Credit Outstanding, Amount			$ 300,000				€ 0.3
Foreign Tax Examination Refund						$ (200,000)
Tax Authority, Spain [Member] \| Foreign Tax Authority [Member] \| Accounts Payable and Accrued Liabilities [Member]
Income Tax Examination, Penalties Expense				132,000	$ 132,000
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio	10
Stipulation [Member]
Litigation Settlement, Amount Awarded to Other Party		$ 350,000
Litigation Settlement, Amount Paid by Insurer		$ 350,000
Estimated Litigation Liability, Current				350,000
Insurance Settlements Receivable				$ 350,000

Note 10 - Income Taxes (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
Note 10 - Income Taxes (Details Textual) - USD ($)	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2017
Unrecognized Tax Benefits	$ 0
Income Tax Expense (Benefit)	0	$ 0
Tax Authority, Spain [Member] \| Foreign Tax Authority [Member] \| Accounts Payable and Accrued Liabilities [Member]
Income Tax Examination, Penalties Expense	$ 132,000		$ 132,000

Note 11 - Operating Segments and Geographic Information (Details Textual)	3 Months Ended
	Jul. 31, 2017
Number of Operating Segments	1