Investments in Energy Efficiency and Solar Photovoltaic Systems for the Tohono O'Odham Nation: An Economic Feasibility Study

Objectives: This study analyzes the costs and benefits to the Tohono O’odham Nation of alternatives to lessen their reliance on external supplies of electricity (grid dependency). Two options are considered: (a) investments to improve the energy efficiency for existing public buildings and (b) investments in distributed solar photovoltaic systems. Analysis considers the effects of interest rates, net metering options and the potential of solar
tracking technologies on relative costs and benefits of alternative investments.

Methods: Estimates of investment options for energy efficiency were obtained from a detailed energy study (ASHRAE Level II) of 28 tribal facilities of >200,00 square feet conducted by 7th Gen Energy Solutions. Distributed solar photovoltaic options were assessed using the HOMER micro power optimization software developed by the National Renewable Energy Laboratory (NREL). Data on tribal facilities and local energy market parameters were used to evaluate the economic feasibility of alternative designs for grid-connected power systems for a variety of applications. Comparisons were made between (a) investments in improved building energy efficiency, (b) investments in new photovoltaic systems and (c) joint investments in both improved energy efficiency and photovoltaic.

Results: The HOMER analysis suggests that the optimal solution in alleviating grid dependency is to just retrofit the tribal buildings for improved energy efficiency. Given the current electricity pricing and taxation policies in place, this provided a higher payoff than either investment in PV systems alone or combining improved building energy efficiency measures with PV systems. A combination of lower price per watt for solar photovoltaic and an increase in current electricity price per kWh would make the investment more viable.

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