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        <link:usedOn>link:presentationLink</link:usedOn>
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        <link:usedOn>link:presentationLink</link:usedOn>
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      <link:roleType id="UnauditedCondensedConsolidatedStatementsOfCashFlows" roleURI="http://www.oesx.com/role/UnauditedCondensedConsolidatedStatementsOfCashFlows">
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        <link:usedOn>link:presentationLink</link:usedOn>
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      <link:roleType id="UnauditedCondensedConsolidatedStatementsOfOperations" roleURI="http://www.oesx.com/role/UnauditedCondensedConsolidatedStatementsOfOperations">
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    </xsd:appinfo>
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  <xsd:element id="oesx_AccountsReceivablesDueMaximumPeriod" name="AccountsReceivablesDueMaximumPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_AccountsReceivablesDueMinimumPeriod" name="AccountsReceivablesDueMinimumPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_AccruedContractCostsCurrent" name="AccruedContractCostsCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="oesx_AccruedExpensesPolicyTextBlock" name="AccruedExpensesPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_AgreementWithWisconsinDepartmentOfCommerceMember" name="AgreementWithWisconsinDepartmentOfCommerceMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_AgreementwithTramontinaU.S.CookwareInc.Member" name="AgreementwithTramontinaU.S.CookwareInc.Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_ConcentrationRiskSupplierOneMember" name="ConcentrationRiskSupplierOneMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_ConcentrationRiskSupplierTwoMember" name="ConcentrationRiskSupplierTwoMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_CreditAgreementMember" name="CreditAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_CustomerEquipmentFinanceNotesPayableMember" name="CustomerEquipmentFinanceNotesPayableMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_DeLageLandenFinancialServicesInc.Member" name="DeLageLandenFinancialServicesInc.Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_DebtInstrumentBuyoutOption" name="DebtInstrumentBuyoutOption" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="oesx_DebtInstrumentNumberOfContractsForCollateral" name="DebtInstrumentNumberOfContractsForCollateral" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="oesx_December2014OTAFinanceProgramMember" name="December2014OTAFinanceProgramMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_DeferredCompensationArrangementWithIndividualCompensationExpensePeriodOfRecognition" name="DeferredCompensationArrangementWithIndividualCompensationExpensePeriodOfRecognition" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_DistributionServicesMember" name="DistributionServicesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_EffectiveIncomeTaxRateReconciliationNetofDiscreteTaxItemsPercent" name="EffectiveIncomeTaxRateReconciliationNetofDiscreteTaxItemsPercent" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_EmployeeStockPurchasePlanClosingMarketPriceOfSharesPurchased" name="EmployeeStockPurchasePlanClosingMarketPriceOfSharesPurchased" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_EnergyManagementMember" name="EnergyManagementMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_EngineeredSystemsMember" name="EngineeredSystemsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_EntitythatCurrentDirectorOwnsMinorityInterestandServesasBoardofDirectorsChairmanMember" name="EntitythatCurrentDirectorOwnsMinorityInterestandServesasBoardofDirectorsChairmanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_FairValueOfClosingCommonStockPrice" name="FairValueOfClosingCommonStockPrice" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="oesx_FinancingReceivableTypeAxis" name="FinancingReceivableTypeAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_FinancingReceivableTypeDomain" name="FinancingReceivableTypeDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_FiniteLivedandIndefiniteLivedIntangibleAssetsGross" name="FiniteLivedandIndefiniteLivedIntangibleAssetsGross" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="oesx_GreaterThanNinetyDaysMember" name="GreaterThanNinetyDaysMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_HarrisSellersNoteMember" name="HarrisSellersNoteMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_HighIntensityFluorescentLightingProductsMember" name="HighIntensityFluorescentLightingProductsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_IncomeTaxTextualAbstract" name="IncomeTaxTextualAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_InventoryFinishedGoodsValuationReserves" name="InventoryFinishedGoodsValuationReserves" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="oesx_InventoryRawMaterialsandSuppliesValuationReserves" name="InventoryRawMaterialsandSuppliesValuationReserves" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="oesx_InventoryReserveLengthofTimeofInventoryUsageConsidered" name="InventoryReserveLengthofTimeofInventoryUsageConsidered" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_InventoryWorkinProcessValuationReserves" name="InventoryWorkinProcessValuationReserves" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element id="oesx_LineofCreditFacilityAdditionalBorrowingCapacity" name="LineofCreditFacilityAdditionalBorrowingCapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="oesx_LineofCreditFacilityCovenantTermsMinimumIndebtednessRatio" name="LineofCreditFacilityCovenantTermsMinimumIndebtednessRatio" nillable="true" substitutionGroup="xbrli:item" type="xbrli:pureItemType" xbrli:periodType="instant" />
  <xsd:element id="oesx_LineofCreditFacilityPotentialMaximumBorrowingCapacity" name="LineofCreditFacilityPotentialMaximumBorrowingCapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element id="oesx_NumberofRecentlyRetiredMembersoftheBoard" name="NumberofRecentlyRetiredMembersoftheBoard" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
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  <xsd:element id="oesx_OperatingLeasesMonthlyRentalPaymentsReceivable" name="OperatingLeasesMonthlyRentalPaymentsReceivable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="oesx_OperatingLossCarryforwardsAssociatedWithExerciseOfNonQualifiedStockOptions" name="OperatingLossCarryforwardsAssociatedWithExerciseOfNonQualifiedStockOptions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
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  <xsd:element abstract="true" id="oesx_OtherLongTermDebtMember" name="OtherLongTermDebtMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element id="oesx_PeriodOfTimeWithoutInterestAccruingOrPrincipalPaymentsDue" name="PeriodOfTimeWithoutInterestAccruingOrPrincipalPaymentsDue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_PowerPurchaseAgreementProductRevenueRecognizableTerm" name="PowerPurchaseAgreementProductRevenueRecognizableTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_PrepaidExpensesAndOtherCurrentAssetsPolicyTextBlock" name="PrepaidExpensesAndOtherCurrentAssetsPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_ProceedsfromExerciseofWarrantsandStockOptions" name="ProceedsfromExerciseofWarrantsandStockOptions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="oesx_PropertyPlantAndEquipmentEstimatedUsefulLife" name="PropertyPlantAndEquipmentEstimatedUsefulLife" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_Provisionforinventoryreserves" name="Provisionforinventoryreserves" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_RestrictedSharesIssuedToKeyEmployeesAbstract" name="RestrictedSharesIssuedToKeyEmployeesAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_SaleLeasebackTransactionAreaofLeasedProperty" name="SaleLeasebackTransactionAreaofLeasedProperty" nillable="true" substitutionGroup="xbrli:item" type="num:areaItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_SaleLeasebackTransactionLeaseTerm" name="SaleLeasebackTransactionLeaseTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_SaleLeasebackTransactionRentExpensePerSquareFoot" name="SaleLeasebackTransactionRentExpensePerSquareFoot" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_SalesTypeNetMember" name="SalesTypeNetMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeited" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeited" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantSharesIssuedToEmployee" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantSharesIssuedToEmployee" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantSharesIssuedToNonEmployee" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantSharesIssuedToNonEmployee" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="oesx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerSharePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardPerSharePrice" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="oesx_WellsFargoBankNationalAssociationMember" name="WellsFargoBankNationalAssociationMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>





