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    <element id="OPTT_PropertyPlantAndEquipmentUsefulLifeTableTextBlock" name="PropertyPlantAndEquipmentUsefulLifeTableTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ScheduleOfRightofUseAssetsAndLeaseLiabilitiesTableTextBlock" name="ScheduleOfRightofUseAssetsAndLeaseLiabilitiesTableTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ScheduleOfConsolidatedStatementOfOperationsOfAcquisition" name="ScheduleOfConsolidatedStatementOfOperationsOfAcquisition" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ExerciseOfPrefundedWarrantsNetOfIssuanceCostsShares" name="ExerciseOfPrefundedWarrantsNetOfIssuanceCostsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_StockIssuedDuringPeriodSharesNewIssuesOne" name="StockIssuedDuringPeriodSharesNewIssuesOne" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ExerciseOfCommonWarrantsNetOfCostsShares" name="ExerciseOfCommonWarrantsNetOfCostsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_AggregateOfferingPriceOfCommonStock" name="AggregateOfferingPriceOfCommonStock" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_DebtForgivenessDescription" name="DebtForgivenessDescription" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PaymentOfPayrollTaxesRelatedToStockOptionExercises" name="PaymentOfPayrollTaxesRelatedToStockOptionExercises" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_FairValueOfBasePurchasePrice" name="FairValueOfBasePurchasePrice" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PerformanceObligationSharesCompensation" name="PerformanceObligationSharesCompensation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_SecondAmendedPurchaseAgreementMember" name="SecondAmendedPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_TwoThousandAndEighteenInducementPlanMember" name="TwoThousandAndEighteenInducementPlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_TwoThousandAndFifteenOmnibusIncentivePlanMember" name="TwoThousandAndFifteenOmnibusIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_CharlesFDunleavyMember" name="CharlesFDunleavyMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PreFundedWarrantsMember" name="PreFundedWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_CheckingAndSavingsAccountsMember" name="CheckingAndSavingsAccountsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ComputerEquipmentAndSoftwareMember" name="ComputerEquipmentAndSoftwareMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_OfficeFurnitureAndEquipmentMember" name="OfficeFurnitureAndEquipmentMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
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    <element id="OPTT_StockPurchaseAgreementMember" name="StockPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_AspireCapitalFundLLCMember" name="AspireCapitalFundLLCMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PerformancceBasedStockOptionsMember" name="PerformancceBasedStockOptionsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_TwoExecutivesMember" name="TwoExecutivesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_StockIncentivePlanMember" name="StockIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_TwoThousandNinteenATMFacilityMember" name="TwoThousandNinteenATMFacilityMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_AGPAllianceGlobalPartnersMember" name="AGPAllianceGlobalPartnersMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_RestrictedCashAndSecurityAgreementsMember" name="RestrictedCashAndSecurityAgreementsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_SantanderBankMember" name="SantanderBankMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_LetterOneMember" name="LetterOneMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_LetterTwoMember" name="LetterTwoMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ForeignFinancialInstitutionsMember" name="ForeignFinancialInstitutionsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_EniSPAMember" name="EniSPAMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_EGPMember" name="EGPMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_OtherMember" name="OtherMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_EngineeringAndProductDevelopmentMember" name="EngineeringAndProductDevelopmentMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_MonroeTownshipMember" name="MonroeTownshipMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PaycheckProtectionProgramMember" name="PaycheckProtectionProgramMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_EmployeeMember" name="EmployeeMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_SubjectToServiceBasedVestingRequirementsMember" name="SubjectToServiceBasedVestingRequirementsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_EURMember" name="EURMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PerformanceStockOptionsMember" name="PerformanceStockOptionsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_TwoThousandTwentyATMFacilityMember" name="TwoThousandTwentyATMFacilityMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
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    <element id="OPTT_EmployeesAndExecutivesMember" name="EmployeesAndExecutivesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_RecordedAdditionalPenaltyMember" name="RecordedAdditionalPenaltyMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_JunePurchaseAgreementMember" name="JunePurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_AugustTwentyTwentyMember" name="AugustTwentyTwentyMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_StockPurchaseAgreementOneMember" name="StockPurchaseAgreementOneMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_OfficeFurnitureAndFixturesMember" name="OfficeFurnitureAndFixturesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_EquipmentUnderCapitalizedLeaseMember" name="EquipmentUnderCapitalizedLeaseMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_ThreeDentAcquisitionMember" name="ThreeDentAcquisitionMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_CommonWarrantsMember" name="CommonWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_PerformanceBasedStockOptionsMember" name="PerformanceBasedStockOptionsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_AsiaAndAustraliaMember" name="AsiaAndAustraliaMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_NJMember" name="NJMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="OPTT_AccountReceivableContractAssetsAndContractLiabilitiesAbstract" name="AccountReceivableContractAssetsAndContractLiabilitiesAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
</schema>
