Solar photovoltaic (PV) is an important strategy to de-carbonize the energy sector in the United States and to reduce the health, environmental, and climate change damages associated with the production of electricity from fossil fuel sources. While the potential for solar PV in the residential and commercial sectors has been widely studied, the potential in educational buildings is largely unknown. Educational institutions account for 11% of total US building electricity consumption and 14% of building floorspace. These buildings also contribute to approximately 4% of total US CO2 emissions, thus playing a potentially important role in climate mitigation strategies. We estimate the electricity use for 132k educational institutions across the US and estimate electricity generation, greenhouse gas and health damaging air emissions reductions, and private and social costs and benefits that would result from adopting rooftop solar PV. We find that solar PV in US educational institutions could provide 100 TWh of electricity services annually, meeting 75% of these buildings' current electricity consumption. We estimate the highest generation potential in Texas, California, and Florida with K-12 public educational institutions comprising the bulk of that generation. The provision of electricity services from rooftop solar PV on educational institutions could reduce health, environmental, and climate change damages by roughly $4 billion per year (assuming a social cost of carbon of $40/ton and value of statistical life of $10M in 2018 USD). Two key findings from this study are that: (i) the private costs of solar for educational institutions still exceed the private benefits from reduced electricity consumption across the entire country (unless a third party operation model is used, in which case some locations can have net-benefits), and (ii) with the exceptions of California and New York, the social health, environmental and climate change benefits exceed the levels of current incentives provided by the state and retail subsidies.

The design and techno-economic performance of a compact additively manufactured (AM) molten salt (MS)-to-supercritical carbon di-oxide (sCO2) primary heat exchanger (PHE) for solar thermal application is described. The PHE design consists of sCO2 flow through an array of microscale pin fins while the MS flows through mm-scale rectangular channels. Constraints imposed by AM using laser powder bed fusion method are considered in the design. Structural and fluid flow simulations are performed to arrive at a viable design of the core and headers. A simplified one-dimensional steady state model for the PHE is developed including the impact of surface roughness from the AM process. A process-based cost model is used to determine the tradeoff between thermofluidic design and manufacturing cost. A parametric study is performed using the thermo-fluidic and cost models to determine the set of geometrical and flow variables that result in high power density and low cost, while restricting the pressure drop on the sCO2 side to less than 2% of line pressure. Flow rates of MS and sCO2 were varied over heat capacity rate ratios ranging from 0.2 to 1. Results indicate that it is possible to design a low-pressure drop AM PHE with an effectiveness of 90% and a power density in excess of 10 MW/m3 (including headers). Fabrication of representative nickel superalloy specimens are shown to demonstrate that low-porosity parts with the requisite dimensional tolerance of PHE core can be generated.