Sustainability in the Solar Industry
Figure 1. Projected growth of various fuels.
By Chris Kline and Dan Salas
Utility-scale solar power in the United States is projected to continue growing for the next several decades in support of national energy goals. The primary purpose of utility-scale solar is to produce safe electricity at scale while reducing greenhouse-gas emissions as compared to emissions from fossil-fuel-powered facilities that solar photovoltaic (PV) technology is replacing.
However, solar PV growth is coming at a time when key stakeholders are expecting and demanding more from corporations than simply providing clean energy. Investors, regulators, legislators and community members are holding corporations—including utilities and solar developers—to a growing range of environmental, social and governance (ESG) expectations. These expectations are an increasingly important component in the design and operation of utility-scale solar facilities. This article examines some of these key environmental ESG issues as well as how solar developers, engineers and scientists are addressing them.
Historic and Projected Growth of U.S. Solar PV
The United States is undergoing a transformation in how electricity is generated. The U.S. Energy Information Administration (USEIA) reports that in 2020 electricity generated from renewable energy comprised about 21 percent of the nation’s total. This proportion is expected to double to 42 percent during the next three decades (see Figure 1). Further, USEIA reports that within the renewable-energy sector, electricity generated from solar is expected to grow from its current proportion of 16 percent to nearly 50 percent during the same timeframe. Power from utility-scale solar comprises the bulk of this growth (see Figure 2).
The terms “sustainability” and “ESG” often are used interchangeably, but they actually refer to different but related concepts. A business or project may be considered “sustainable” if it operates or is organized to balance the environmental, social and financial topics material to that entity. “ESG” refers to the processes and metrics businesses use to benchmark and manage those sustainability goals.
For example, a sustainable business minimizes its environmental footprint; its ESG goal may be to set a greenhouse-gas emission-reduction target of 40 percent during its current baseline to be achieved by 2030. Corporate stakeholders, particularly investors, increasingly are expecting businesses to report and manage to a range of ESG goals. Greenhouse-gas emissions are key environmental ESG indicators. Other common environmental ESG goals include biodiversity, water quality and waste minimization. While social and governance topics are integral to a comprehensive ESG program, this article will only examine environmental topics.
ESG Challenges and Opportunities for Utility-Scale Solar
By definition, a utility-scale solar project generates power and feeds it to the grid, supplying a utility with energy. The business transaction typically is governed by a power-purchase agreement (PPA), essentially a contract stating the amount of power that will be generated and what the utility will pay for that power. Utility-scale solar projects may range in size from a few megawatts and 10-20 acres to hundreds of megawatts requiring thousands of acres.
Increasingly, the trend is for larger utility-scale projects to come online, typically designed to operate for 30 years or more. These larger projects, in particular, present ESG challenges and opportunities.
Lifecycle Carbon Footprint
Integral to almost any ESG reporting standard is a requirement to measure and reduce the greenhouse-gas footprint for a project, facility or organization. Although solar has a smaller footprint than fossil fuel, solar’s footprint isn’t zero. Figure 3 is a general comparison of the CO2 equivalent emissions from electricity generated from a coal plant with that of a solar PV facility.
A challenge for any solar developer is to more-precisely define and report its greenhouse-gas emissions. In particular, Scope 3 emissions (the “upstream” and “downstream” processes illustrated on Figure 3) are quite difficult to estimate and manage. Even if the overall solar facility’s emissions are relatively small (e.g., 40g CO2 eq/kWh vs. 1,000g CO2eq/kWh for a coal plant), emissions still must be measured, reported and, through time, reduced. For a solar facility, this effort may include specifying the use of panels manufactured using energy-efficient processes.
Land-Conversion ESG Issues
In the United States, large-scale solar projects first were developed in the west and southwest due to legislative and regulatory incentives in California as well as the prevalence of sunny days in the desert southwest. Due to a number of factors—including improved solar PV performance through use of bifacial panels, reduced costs, access to the electric grid and state renewable energy goals—large solar projects now are being built throughout the country. As shown in Figure 4, three of the top five states for new solar installations are located in the eastern United States.
However, large projects have an unavoidable environmental impact on the landscape. Solar developers seeking to meet their own ESG goals (and those of key stakeholders such as investors as well as power purchasers such as utilities and large corporations) are fiercely competing to develop projects that minimize environmental impact and innovate ways to create environmental co-benefits through siting and beneficial vegetation.
In regions such as the Midwest, large solar projects are being developed on land previously used for agriculture production. The conversion of literally hundreds of thousands of acres of agricultural land to solar-power production represents an environmental ESG challenge and opportunity for solar developers.
Environmental factors that utility-scale solar developers consider in the design of their facilities include water quality, particularly from stormwater runoff; habitat and biodiversity impacts; soil health; and carbon-sequestration opportunities related to vegetation installed under and around these facilities. As with any facility designed to operate for 30 or more years, operation and maintenance considerations are integral to engineering decisions. Facilities designed to minimize construction costs may not be the most economical to operate during the project’s lifetime.
One particular topic illustrates how utility-scale solar design decisions and ESG considerations intersect: vegetation installed under and around solar facilities.
During the last several years, concerns about wild, native pollinators gained attention. In 2015, the White House revealed a national strategy for protecting pollinators, which was intended to combat the ongoing declines of native pollinators as well as those of commercial honey bees. Despite this, declines in pollinators have continued. There have been several listings of pollinators under the Endangered Species Act, including the rusty patched bumble bee in 2017. In 2020, the U.S. Fish and Wildlife Service published a decision noting that the monarch butterfly “warrants listing.” It’s currently under a “precluded” status, meaning it’s undergoing continued consideration. Earlier in 2021, the American bumblebee was petitioned for a listing under the Endangered Species Act.
Numerous states have created pollinator scorecards intended to influence vegetation decisions in site designs for solar projects. Scorecards often are voluntary, but some states and municipal governments have required certain scores be met for various permit or ordinance approvals. Addressing these metrics can be challenging and sometimes expensive. Moreover, after vegetation is designed, the site owner must be prepared for establishment and maintenance to sustain this vegetation while also maintaining compatibility with energy-generation and operational needs. To do this, intentional design and management is required to ensure success and avoid expensive failures.
Engineering and Environmental Research to Understand Solar-Facility Vegetation Concerns
The co-location of pollinator plantings at large-scale solar facilities (10 MW or larger) recently gained increased interest from energy companies, state and local governments and others, but it faces barriers to adoption due to uncertainties around the scale and configuration of pollinator plantings as well as effects on PV performance, installation and operational costs, and ecological benefits. A three-year project, funded by the U.S. Department of Energy Solar Energy Technology Office, is bringing together leading researchers, large-scale solar developers and practitioners to investigate the ecological and economic benefits as well as performance impacts of co-located pollinator plantings at utility-scale solar facilities.
The research is led by the University of Illinois Chicago Energy Resources Center and is supported by researchers from Argonne National Laboratory, the National Renewable Energy Laboratory, University of Illinois – Champaign, and Cardno. The team will leverage existing and new research, collaborative partnerships, and industry and other stakeholder involvement to achieve the following objectives:
1. Research co-location and scalability of pollinator plantings at six solar facilities with capacities greater than 10 MW, namely PV performance impacts, economic considerations and ecological benefits.
2. Create comprehensive implementation guidance and decision tools to assist solar developers and other stakeholders when considering pollinator plantings at large-scale solar facilities.
3. Engage solar-industry partners and share findings with broader industry stakeholders.
The project will study the PV performance impacts, economic considerations and ecological benefits of co-locating pollinator plantings at large-scale solar facilities through field research at six operating large-scale solar facilities (see Figure 5). A variety of pollinator-beneficial seed mixes will be introduced at four or more of the solar-facility test sites during the first year of the study and the remaining site(s) in the second year. It likely will take two to five years for the pollinator plantings to become fully established. Trends in performance and ecological impacts may start to be seen about one year after planting (i.e., during the second field season) and will become more evident in the second year after planting (i.e., third field season).
For the PV performance field research, the project team will test whether evapotranspiration of the plantings results in a cooler microclimate underneath the panels, thereby improving PV panel efficiency and power production. The team will collect data on environmental conditions under and around the panels as well as PV performance data provided by site operators.
The ecological performance field research will evaluate the diversity and abundance of native pollinator insects, birds and bats in and around the pollinator plantings using a variety of different sampling methods (e.g., netting, observational transects, acoustic and ultrasonic monitors). Plant diversity and abundance (particularly flowering species) within the pollinator plantings also will be assessed. The economic analysis will consist of the collection of cost data on the installation and maintenance of pollinator plantings compared to other ground-cover types (e.g., turf and gravel).
Data will be gathered from solar-facility test sites, other solar facilities, and past work from the National Renewable Energy Laboratory’s Innovative Site Preparation and Impact Reductions on the Environment (InSPIRE) project. The project team will conduct a lifecycle cost analysis to compare different configurations and options.
Utilizing field research and a review of existing literature, the project also will develop an implementation manual for pollinator plantings at large-scale solar facilities that includes key considerations for planning, design, installation and maintenance. In addition, the project will provide three online tools:
1. A cost-benefit calculator for site owners and developers to evaluate the economic costs and benefits of including pollinator plantings at large-scale solar facilities.
2. A solar-site seed-selection tool for users to select plants based on specific site conditions, including EPA ecoregions, soil moisture, plant height, sun exposure, soil pH and cost.
3. A solar-specific update to the existing pollinator scorecard developed by the Rights-of-Way as Habitat Working Group to assist owners and operators in evaluating pollinator vegetation at large-scale solar facilities after it’s established.
Engineers designing utility-scale solar projects face three significant “mega trends”:
1. The global imperative to reduce greenhouse-gas emissions.
2. ESG expectations investors and other key stakeholders are demanding.
3. Leveraging new research to improve planning for co-located environmental benefits.
The unique challenges associated with land conversion and the potential benefits from carbon sequestration present an opportunity for creative design considerations. The data from the research in this article should benefit engineers and designers as they tackle these challenges and also should help corporations achieve
their ESG goals.