US rooftop solar energy installations could generate enough electricity to comprise the equivalent of up to 39% of the total national electricity sales market, according to a new analysis from the Energy Department’s National Renewable Energy Laboratory (NREL).
The new analysis — which made use of detailed light detection and ranging (LiDAR) data for 128 US cities, and newly improved data analysis methods and simulation tools — found that the technical potential for rooftop solar photovoltaic (PV) systems in the country is right around 1,118 gigawatts (GW) of capacity, and 1,432 terrawatt-hours (TWh) of annual generation.
These figures represent a large increase over earlier NREL estimates — which placed the technical potential at 664 GW of capacity and 800 TWh of annual electricity generation.
A new press release provides more:
Analysts attribute the new findings to 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.
…To calculate these estimates, NREL analysts used LiDAR data, Geographic Information System methods, and PV-generation modeling to calculate the suitability of rooftops for hosting PV in 128 cities nationwide-representing approximately 23% of US buildings-and provide PV-generation results for 47 of the cities. The analysts then extrapolated these findings to the entire continental United States. The result is more accurate estimates of technical potential at the national, state, and zip code level.
…Within the 128 cities studied, the researchers found that 83% of small buildings have a suitable location for PV installation, but only 26% of those buildings’ total rooftop area is suitable for development. Because of the sheer number of this class of building across the country, however, small buildings actually provide the greatest combined technical potential. Altogether, 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% of the total technical potential of rooftop PV.
“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 US electricity demand,” noted Robert Margolis, NREL senior energy analyst and co-author of the report.
Margolis also commented that the new figures only relate to already existing (and well-suited) rooftops — ground-mounted installations, installations over parking lots, solar windows, etc; none of these are included. It should also be realized that as solar PV module solar conversion efficiency increases, so will these estimates.
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