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Renewably Powered I Photovoltaics <br />On -Site Design Considerations <br />Where to create solar arrays: ground, rooftop, or parking canopies? <br />The first constraint on system size is the available space on the property. Since ground mounted solar arrays are typically the least expensive, this is the first <br />priority, followed by rooftop and then parking canopies. Solar systems benefit from economies of scale - generally, the larger the system, the cheaper it is per <br />kW. <br />Financial size optimization <br />In some cases, it is possible to add more solar capacity than can be used by the facility. Typically, based on current regulations, this scenario would mean <br />giving the value of this electricity back to the utility. All recommended on -site solar in this roadmap avoids significant amounts of such value "give back". <br />Roof age <br />Roof membranes and solar PV modules have similar lifespans, about 30 years. De-installation/re-installation of a solar system is costly, creating unviable <br />economics in addition to unnecessary hassle for facilities management down the road. The PV array at the Library is the only recommended system that is <br />roof -mounted. This array should be installed at the time of the Library roof replacement. <br />Assumed useful life of solar <br />The National Renewable Energy Laboratory estimates the operational lifespan of photovoltaic systems to be 25 to 40 years, and a recent study by the Lawrence <br />Berkeley National Lab found that utility scale solar developers assume an average useful life of -35 years. The financial pro forma included in this roadmap <br />assumes a useful life of the ground and canopy mounted solar arrays of thirty years, and 25 years for roof mounted arrays (based on typical 25 year roof life). <br />While this is longer than the warranty period, it is expected the arrays will be functional for this period and potentially beyond. A small output degradation is <br />assumed over time, consistent with standard industry practice. Note the pro forma does assume micro -inverter replacement as part of solar operation and <br />maintenance at year 15. <br />Agrivoltaics <br />The co -location of ground mounted solar arrays <br />and agriculture (such as community pea patches), <br />or carbon sequestering/pollinator habitat restored <br />native meadows, are a great holistic sustainability <br />solution. All ground mount systems should have some <br />component of agrivoltaics to further mitigate carbon <br />whether it's drought resistant irrigation, pollinator <br />habitats, or wild flowers. <br />Planting plan for Denver Botanic <br />Gardens Solar Array <br />Zone 1 Zone 2 Zone 3 <br />Vegetable Pollinator Vegetable <br />Production Habitat Cover Production <br />Crop Rotation <br />Zone 4 Zone 5 Zone 6 <br />Pollinator Native Plant Vegetable <br />Habitat Cover Seed Bank Production <br />Crop Rotation <br />.I <br />Potential future opportunities for larger -scaled Louisville <br />owned renewables <br />Virtual net metering <br />The State of Colorado recently adopted virtual net metering <br />legislation, which potentially enables utility customers with <br />multiple site portfolios to transfer the electricity value of <br />solar production from one location to another. The details <br />of this legislation are complex and still being understood, <br />but over time, it may enable Louisville to look at larger scale <br />opportunities, such as undeveloped land, open water, or park <br />areas to be used for solar production . <br />Water reservoir or sewage processing pond floating solar <br />A specific opportunity for larger scale solar (which would <br />require net metering to make financially feasible) is floating <br />solar. An initial evaluation suggests that an array-400kWdc <br />could sit at the Sid Copeland Treatment Plant reservoir. <br />Typically arrays need to be on the scale of 1-2MW or larger to <br />cost -compete with ground mount options. <br />CITY OF LOUISVILLE I FINAL REPORT V3 1 INTERNAL DECARBONIZATION PLAN 121 <br />34 <br />