Maximize the benefits of solar energy through techno-ecological synergies

This transition to decarbonize economies will be a global task, including efforts to establish laws to foster renewable energy development, and transition entire industries like cement and agriculture to lower carbon futures.

The transition towards renewable energy, which is cost-effective today requires a paradigm shift in thinking: The subterranean fossil fuels that power much of the world today have a small spatial yet vast environmental footprint compared to the more diffuse renewable energy resources most of which, for now, must be collected on Earth’s surface.

In a world of increasing land use pressure, and with the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services’ (IPBES’) global assessment identifying land use change as the dominant driver of decline in nature (above that of climate change), this poses a significant challenge.

Unlike other energy systems, solar energy generated from PV can be coupled with the built environment, human infrastructure, or working landscapes, including agriculture, rangelands, and aquaculture. This presents an opportunity to maximize multiple overlooked environmental benefits of solar energy deployment through techno-ecological synergies – a framework for engineering mutually beneficial relationships between technological and ecological systems.

We, an international group of researchers led by Dr. Rebecca R. Hernandez a Professor at the University of California, Davis and 11 other organizations, think that techno-ecological synergies represent an important framework for the sustainable production of electricity. We recently published a paper in Nature Sustainability that provides a comprehensive examination of the opportunities to enhance the ecological and technological advantages of solar energy. Solar electricity generation coupled with sites that sequester carbon or increase ecosystems services, such as improvements for pollinator habitats — and offered an important new framework for analyzing solar projects to maximize sustainable outcomes.

Sixteen different types of solar installations with potential techno-ecological synergies were identified, including installations over previously disturbed land, over water, as distributed energy generators, in agroecological systems, and distributed throughout the electricity grid. This approach would result in land sparing of undisturbed natural areas conserving plant, animal, including pollinator biodiversity and intact carbon sequestration cycles.

The techno-ecological synergies framework can act as a tool both for speeding the transition and for promoting smart planning of solar installations. By providing further evidence of solar energy’s net benefits, the framework can be applied in regulatory and policy discussions to counter attacks by fossil fuel companies and traditional electric utilities that stand to profit from maintaining the status quo.

The framework also provides an opportunity to thoughtfully maximize benefits of as many solar installations as possible. By considering the compounding climate and extinction crises, as well as the challenges of providing electricity for a rapidly growing global population with increasing demands per capita, unintended consequences of a mass energy transition can be avoided and co-benefits embedded.

Corporations and governments are beginning to make shifts by committing to 100% clean energy and divesting from fossil fuels. These policies and practices ensure that solar energy will continue to grow rapidly in some places. But others are dragging their feet. Implementing plans to adopt clean energy and compelling those that are slow-to act to move creates large questions such as how quickly the transition will happen, and where and how solar energy is developed. How an organization transitions to use of 100% clean energy – specifically including requests for additional ecosystem and agricultural benefits – is becoming increasingly important. Xcel Energy and Clif Bar are two recent examples of a utility and a corporation requesting more in their solar request for proposals process.

Across these techno-ecological synergies, we characterized 20 specific benefits, ranging from grid resilience to land sparing to pollinator habitat, and then created a matrix to communicate these synergistic outcomes:

One important example the authors identified is the opportunity for solar energy on degraded lands, such abandoned mines and brownfields. The authors found that degraded lands in the United States account for almost twice the land area of California. Of this land, the most degraded sites, such as EPA Superfund sites, could produce over 1.6 million GWh per year of PV solar electricity. That’s more than 35% of total U.S. consumption of electricity in 2015.

Center-pivot agriculture is another techno-ecological synergy. The team estimates 21,000 km2 or 1,350 GWh could be produced in the U.S. by utilizing these lands. This could also be directly tied to irrigation systems.

Drawing on prior research from Dr. Hernandez’s lab led by coauthor Madison Hoffaker, the team estimates 39 TWh per year of energy potential over 104 km2 of agricultural reservoirs in California’s Central Valley. This could contribute 15% of California’s annual electricity and save 0.12 km3 of water per year.

Further, if degraded lands were targeted for solar development instead of lands such as shrublands and prairies, which have more potential for carbon sequestration benefits, the authors note, then overall climate emissions associated with land use would be reduced. Research from the U.S. Geological Survey notes that arid landscapes will be a source of emissions through 2100 because of land use change. Better land use practices could turn this source to a sink through improved conservation.

The paper also highlights food systems as an opportunity for solar techno-ecological synergies. The authors identified 10 potential beneficial outcomes of “agrivoltaic systems,” or panels placed within the same land area as agricultural production. These benefits include increased foraging resources for managed and native pollinators, increased water-use efficiency and soil erosion prevention. Solar energy infrastructure can also alter microclimatic conditions that benefit overall crop production with increased water use efficiency, and keep PV systems cooler and operating more efficiently. Co-siting agriculture and PV systems also results in higher yields of food and solar energy combined compared to when the food and solar energy production were separate.

On water systems, the authors examine the multiple benefits of “floatovoltaics” for panels attached to pontoons that float on water. These systems can provide eleven potential beneficial outcomes, ranging from reducing algae growth to preventing loss of water from evaporation – a benefit that is particularly important for considering solar placed over aquifers, reservoirs, and water treatment or desalination systems in water-stressed regions. The team noted prior research that found 4,500 m2 of floatovoltaics covering the entirety of the reservoir produces 425,000 kWh and saves 5000 m3 of water via avoided evaporation per year.

Finally, in built-up systems, we highlighted solar synergies on rooftops and other developed spaces on or near where people live and work like parking lots. Rooftop panels can insulate buildings to improve energy savings and ultimately support human health and comfort. Panels can cool buildings and parking lots by reflecting light, potentially reducing the urban heat island effect and decreasing the need for air conditioning in hot summer months.

Emerging solar technologies, such as transparent solar panels, and flexible solar for fencing, roadways, and other applications only highlight how advances in materials science open more doors for the techno-ecological synergies. Continued innovations in solar, but also in wind, storage and energy efficiency will provide even more opportunities.

The team consider the characterization of these benefits in their paper as a promising “springboard for the integration of solar energy techno-ecological synergies into industry and society.” They acknowledge that these synergies may require their own policies, incentives, and subsidies in addition to those already in place for other clean energy technologies, including larger-scale solar.

Table 1 in the paper notes that over 800,000 km2 of degraded land available in the United States for solar development: brownfields, Superfund sites, landfills, abandoned mines, contaminated and abandoned agricultural lands

We offer this framework with the hope that it be used in cost-benefit analyses purposes of electric rate-making, resource procurement and planning, net metering, and other value-setting processes that affect distributed solar markets and ultimately delivers both energy and environment benefits.