Slide 1AgendaSystem DefinitionSystem DefinitionModel StructureModel StructureModel StructureModel StructureSimulation Decision RuleDeterministic Design ResultsResults (Uncertainty Included)ConclusionsReflectionsFinal Application PortfolioCommunityLevelSolarEnergySystemDanielMarticelloESD.71Fall 20101Agenda•System Definition•Model Structure•Deterministic design results•Flexible design results•Conclusions and Reflections•Next Steps2System Definition3TheVision•Community level system•Linked solar panels•Central energy storage•Negotiated off-peak rateExercisescope•Single home in Tucson AZ•Historic hourly solar data•20-year timeframeSystem Definition4Solarpanels•Initial install (5.52 kWh DC) [$17,000] •Additional increments are 0.92 kWh [~$2,500]Flywheelenergystorage•5 kWh unit [$60,000]•Production systems from 5-25 kWh available [$60K-$120K]Gridpower•Peak and off-peak rates“GreenPower”Subsidy•$2.70/W DC•Reduced initial CAPEX by ~$15,000Model Structure•Solar Panels–Output dependent on three factors•Size of the array: 24 panels•Solar insolation: Tucson AZ (representative hourly data)•Efficiency of conversion: 77% (system chosen for model)5Model Structure•Home Power Consumption Profile– Energy consumption consists of two components•Variable load tied to amount of heating or cooling required•Base load that includes other usage (appliances, lighting, etc)•Used standard curves scaled to capture heating/cooling use6Model Structure•Energy Storage (Flywheel storage system)– 20-year + lifetime (Not cycle limited)•Size based on static case (discharge cycle vs ops savings)•5 kWh chosen to limit cost but get to flat peak in the curve7175,200 Total data points• Hourly over 20 yearsModel Structure•Grid Power–Price/kWh is source of uncertainty–Modeled as a random walk– Starting price of 10.3 cents/kWh8Simulation Decision RuleIf the current year’s grid provided electricity price is 10% or more above last year’s price, add an additional 4 panels to each home’s array.•Reduce reliance on grid power as price increases•Justifies additional solar panel installation•Implemented using two different thresholds–10% and 5% growth in electricity price year-to-year•Discount rate of 10%9Deterministic Design Results•$700-$1,500 saved in electricity costs per year •Savings are insufficient to overcome large CAPEX–Despite CAPEX subsidy of $2.70/W DC expense10Summary of ResultsCAPEX $14,235.00Project NPV ($6,086.38) LossYear 0 1 2 3 4 5 6Peak power ($/KWh) $0.10 $0.10 $0.11 $0.11 $0.11 $0.11 $0.11Off-peak power ($/KWh) $0.07 $0.07 $0.07 $0.07 $0.07 $0.07 $0.07Expand? 0 0 0 0 0 0Capital Expense -$14,235.00 Ops Savings $799.92 $807.92 $816.00 $824.16 $832.40 $840.72 $849.13Expansion Costs $0.00 $0.00 $0.00 $0.00 $0.00Cash Flow -$13,435.08 $807.92 $816.00 $824.16 $832.40 $840.72 $849.13DCF -$13,435.08 $734.47 $674.38 $619.20 $568.54 $522.02 $479.31NPV -$6,086.38 …Results (Uncertainty Included)11Threshold Mean P90 P05 Std Dev10% w/ 1% trend ($6,087) ($5,821) ($6,351) $1575% w/ 2% trend ($5,446) ($5,013) ($5,796) $2605% w/ 3% trend ($4,379) ($3,123) ($5,160) $68110% DR1% growth rate5% DR2% growth rate5% DR3% growth rateConclusions•Large CAPEX makes system a financial loss–Large expense of flywheel–Historical growth rate of electricity price is small•Uncertaintly was too small to drive large change in outcome•Potential game changers–Rapid increase in price of electricity–Incorporation of economy of scale (Demand response)•Scheduled energy use across multiple homes–Carbon credits (system avoids ~6.8 metric tons/year)– Reduction in the cost of flyweel / other storage option12Reflections•Assumptions are a key aspect of any model–Consumption profiles, uncertainty modeling, etc•Screening models are valuable–Allows for more iterations and analysis•Never stop looking for coding errors!Next Step•Model that incorporates sharing across homes–Sharing of generating resources–Scheduling/deconfliction of energy
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