Utility-scale solar energy deployments are not as land intensive as they were a decade ago, thanks to improved power and energy densities. As a result, developers and others who turn to older benchmarks for solar module power and energy density will “significantly overstate” land requirements.
Those are the findings of a new study by researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and Bowdoin College.
The paper was published in the IEEE Journal on Photovoltaics and found that both power and energy density have “increased significantly” over the past decade.
Udated benchmarks as of 2019 that were established by the study are as follows:
Power density: 0.35 MWDC /acre (0.87 MWDC /hectare) for fixed-tilt and 0.24 MWDC /acre (0.59 MWDC /hectare) for tracking plants.
Energy density: 447 MWh/year/acre (1.10 GWh/year/ hectare) for fixed-tilt and 394 MWh/year/acre (0.97 GWh/year/hectare) for tracking plants.
The paper also expressed power density in AC capacity terms. Those numbers are 0.28 MWAC /acre (0.69 MWAC /hectare) for fixed-tilt and 0.18 MWAC/acre (0.45 MWAC/hectare) for tracking plants. The authors said they prefer to work in terms of DC, but offered the AC conversion for purposes of comparison against the densities of other utility-scale generation sources, which are typically expressed in AC terms.
The authors said that concerns about the land requirements and land-use impacts of utility-scale PV have grown as deployment has accelerated and as decarbonization plans call for the solar sector’s rapid expansion. Backlash has grown as utility-scale solar projects are proposed for existing farmland. Places like Virginia and Ohio have become hotbeds for rural interests that are opposed to solar power plants’ expansion.
The researchers also said the amount of land required to build a utility-scale PV plant is also an important cost consideration. Other PV plant costs (such as for modules and inverters) tend to decline with greater deployment due to learning and economies of scale.
By contrast, land costs are “perhaps more likely to increase” with greater deployment as competition for prime sites intensifies, the authors said. Both concerns—expanded land requirements and land-use impacts, as well as rising land costs—can be mitigated by increasing the power and energy densities of utility-scale PV.
The authors said their study provides what may be the first major update of utility-scale PV’s power and energy densities in nearly a decade. They based their work on a sample of ground-mounted PV plants larger than 5 MW-AC that were built in the United States from 2007-2019. The sample included 736 plants totaling 35,482 MWDC (27,001 MWAC) that came online from 2007 to 2019 across 38 states. The sample includes 92% of the total universe of utility-scale PV plants in the United States that achieved commercial operations from 2007 to 2019
The researchers used ArcGIS to draw polygons around satellite imagery of each plant within the sample, and to calculate the area occupied by each polygon. When combined with plant metadata, these polygon areas allowed the researchers to calculate power (expressed in MW/acre) and energy (MWh/year/acre) density for each plant in the sample, and to analyze density trends over time, by fixed-tilt versus tracking plants, and by plant latitude and site irradiance.
Based on their study, the authors said that the median power density increased by 52% for fixed-tilt plants and 43% for tracking plants from 2011 through 2019. Meanwhile, the median energy density rose by 33% for fixed-tilt and 25% for tracking plants over the same period.
The study may be accessed here.
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