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<!-- Created: Thu Jul 11 19:46:46 UTC 2013 -->
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  <xs:element name="OfferingAgreementOfferingTerm" type="xbrli:durationItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item" id="optt_OfferingAgreementOfferingTerm"/>
  <xs:element name="USDepartmentofEnergyMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_USDepartmentofEnergyMember"/>
  <xs:element name="AsiaandAustraliaMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_AsiaandAustraliaMember"/>
  <xs:element name="SpanishTaxAuthoritiesMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_SpanishTaxAuthoritiesMember"/>
  <xs:element name="BarclaysBankAgreementMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_BarclaysBankAgreementMember"/>
  <xs:element name="ExpectedToVestMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_ExpectedToVestMember"/>
  <xs:element name="StockIncentivePlan2006Member" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_StockIncentivePlan2006Member"/>
  <xs:element name="LongTermMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_LongTermMember"/>
  <xs:element name="NJBPUAgreementMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NJBPUAgreementMember"/>
  <xs:element name="AustraliaMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_AustraliaMember"/>
  <xs:element name="RelatedtolossoncontractMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_RelatedtolossoncontractMember"/>
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  <xs:element name="NonEmployeeDirectorsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NonEmployeeDirectorsMember"/>
  <xs:element name="CheckingandsavingsaccountsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_CheckingandsavingsaccountsMember"/>
  <xs:element name="UnitedStatesMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_UnitedStatesMember"/>
  <xs:element name="CurrentYearMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_CurrentYearMember"/>
  <xs:element name="FederalMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_FederalMember"/>
  <xs:element name="NewJerseyBoardofPublicUtilitiesMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NewJerseyBoardofPublicUtilitiesMember"/>
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  <xs:element name="NonvestedRestrictedStockMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NonvestedRestrictedStockMember"/>
  <xs:element name="NewJerseyStateOperatingLossSoldMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NewJerseyStateOperatingLossSoldMember"/>
  <xs:element name="UnitedKingdomMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_UnitedKingdomMember"/>
  <xs:element name="MitsuiShipbuildingAndEngineeringMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_MitsuiShipbuildingAndEngineeringMember"/>
  <xs:element name="OfficeFurnitureandEquipmentMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_OfficeFurnitureandEquipmentMember"/>
  <xs:element name="UKGovernmentsTechnologyStrategyBoardMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_UKGovernmentsTechnologyStrategyBoardMember"/>
  <xs:element name="CertificatesofdepositsandUSTreasuryobligationsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_CertificatesofdepositsandUSTreasuryobligationsMember"/>
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  <xs:element name="USTreasuryobligationsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_USTreasuryobligationsMember"/>
  <xs:element name="CertificatesofdepositdenominatedinAustraliandollarsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_CertificatesofdepositdenominatedinAustraliandollarsMember"/>
  <xs:element name="StateOfNewJerseyCommissionOnScienceAndTechnologyMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_StateOfNewJerseyCommissionOnScienceAndTechnologyMember"/>
  <xs:element name="ShortTermMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_ShortTermMember"/>
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  <xs:element name="NewJerseyStateMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NewJerseyStateMember"/>
  <xs:element name="ComputersandSoftwareMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_ComputersandSoftwareMember"/>
  <xs:element name="OptionsGrantedToConsultantsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_OptionsGrantedToConsultantsMember"/>
  <xs:element name="StockPlan2001Member" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_StockPlan2001Member"/>
  <xs:element name="EuropeanUnionWaverPortProjectMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_EuropeanUnionWaverPortProjectMember"/>
  <xs:element name="NextFiveYearsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_NextFiveYearsMember"/>
  <xs:element name="USNavyMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_USNavyMember"/>
  <xs:element name="CurrentMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_CurrentMember"/>
  <xs:element name="CertificateofdepositdenominatedinUSdollarsMember" type="nonnum:domainItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_CertificateofdepositdenominatedinUSdollarsMember"/>
  <xs:element name="DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="optt_DocumentAndEntityInformationAbstract"/>
</xs:schema>
