New analysis from NREL nearly doubles its previous estimates, showing US building rooftop PV could generate close to 40% of national electricity sales.
Analysts have used detailed light detection and ranging (LiDAR) data for 128 US cities, along with improved data analysis methods and simulation tools, to update the NREL estimate of total US technical potential for rooftop PV systems. The analysis reveals a technical potential of 1,118 GW of capacity, equaling 1,432 TWh of annual energy generation.
Put in another perspective, this new total is equivalent to a whopping 39% of the nation’s electricity sales.
Significant increase in new analysis
The new estimate is much greater than the previous NREL analysis, which tallied 664 GW of installed capacity and 800 TWh of annual energy generation.
NREL analysts attribute these new findings to a number of factors, including increases in module power density, improved estimation of building suitability, higher estimates of the total number of buildings, and improvements in PV performance simulation tools.
The analysis appears in “Rooftop Solar Photovoltaic Technical Potential in the United States: A Detailed Assessment.” The report quantifies the technical potential for rooftop PV in the US, which is an estimate of how much energy could be generated if PV systems were installed on all suitable roof areas.
“This report is the culmination of a three-year research effort and represents a significant advancement in our understanding of the potential for rooftop PV to contribute to meeting U.S. electricity demand,” said Robert Margolis, NREL senior energy analyst and co-author of the report.
Within the 128 cities studied, the researchers found that 83 percent of small buildings are suitably sited for PV installation. However, only 26% of these buildings’ total rooftop area is regarded as suitable for development.
The analysis concludes small buildings have the greatest combined technical potential for rooftop PV. It reports small building rooftops could accommodate up to 731 GW of PV capacity and generate 926 TWh per year of PV energy-approximately 65% of the country’s total rooftop technical potential.
Medium and large buildings have a total installed capacity potential of 386 GW and energy generation potential of 506 TWh per year, approximately 35 percent of the total technical potential of rooftop PV.
“An accurate estimate of PV’s technical potential is a critical input in the development of regional deployment plans,” said Pieter Gagnon, an engineering analyst of solar policy and technoeconomics at NREL and lead author of the report. He said this data will provide municipalities, utilities, solar energy researchers wit a better foundation for PV research and policymaking strategies.
“It is important to note that this report only estimates the potential from existing, suitable rooftops, and does not consider the immense potential of ground-mounted PV,” said Margolis. “Actual generation from PV in urban areas could exceed these estimates by installing systems on less suitable roof space, by mounting PV on canopies over open spaces such as parking lots, or by integrating PV into building facades. Further, the results are sensitive to assumptions about module performance, which are expected to continue improving over time.”
As to its research methodology, NREL states “technical potential is an established reference point for renewable technologies,” quantifying the amount of energy which can be captured from a particular resource.
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