Techno–ecological synergies of solar energy for global sustainability

The strategic engineering of solar energy technologies—from individual rooftop modules to large solar energy power plants—can confer significant synergistic outcomes across industrial and ecological boundaries. Here, we propose techno–ecological synergy (TES), a framework for engineering mutually beneficial relationships between technological and ecological systems, as an approach to augment the sustainability of solar energy across a diverse suite of recipient environments, including land, food, water, and built-up systems. We provide a conceptual model and framework to describe 16 TESs of solar energy and characterize 20 potential techno–ecological synergistic outcomes of their use. For each solar energy TES, we also introduce metrics and illustrative assessments to demonstrate techno–ecological potential across multiple dimensions. The numerous applications of TES to solar energy technologies are unique among energy systems and represent a powerful frontier in sustainable engineering to minimize unintended consequences on nature associated with a rapid energy transition

Renewable Energy in the Context of Sustainable Development

Historically, economic development has been strongly correlated with increasing energy use and growth of greenhouse gas (GHG) emissions. Renewable energy (RE) can help decouple that correlation, contributing to sustainable development (SD). In addition, RE offers the opportunity to improve access to modern energy services for the poorest members of society, which is crucial for the achievement of any single of the eight Millennium Development Goals. Theoretical concepts of SD can provide useful frameworks to assess the interactions between SD and RE. SD addresses concerns about relationships between human society and nature. Traditionally, SD has been framed in the three-pillar model—Economy, Ecology, and Society—allowing a schematic categorization of development goals, with the three pillars being interdependent and mutually reinforcing. Within another conceptual framework, SD can be oriented along a continuum between the two paradigms of weak sustainability and strong sustainability. The two paradigms differ in assumptions about the substitutability of natural and human-made capital. RE can contribute to the development goals of the three-pillar model and can be assessed in terms of both weak and strong SD, since RE utilization is defined as sustaining natural capital as long as its resource use does not reduce the potential for future harvest. The relationship between RE and SD can be viewed as a hierarchy of goals and constraints that involve both global and regional or local considerations. Though the exact contribution of RE to SD has to be evaluated in a country specifi c context, RE offers the opportunity to contribute to a number of important SD goals: (1) social and economic development; (2) energy access; (3) energy security; (4) climate change mitigation and the reduction of environmental and health impacts. The mitigation of dangerous anthropogenic climate change is seen as one strong driving force behind the increased use of RE worldwide. The chapter provides an overview of the scientific literature on the relationship between these four SD goals and RE and, at times, fossil and nuclear energy technologies. The assessments are based on different methodological tools, including bottom-up indicators derived from attributional lifecycle assessments (LCA) or energy statistics, dynamic integrated modelling approaches, and qualitative analyses. Countries at different levels of development have different incentives and socioeconomic SD goals to advance RE. The creation of employment opportunities and actively promoting structural change in the economy are seen, especially in industrialized countries, as goals that support the promotion of RE. However, the associated costs are a major factor determining the desirability of RE to meet increasing energy demand and concerns have been voiced that increased energy prices might endanger industrializing countries’ development prospects; this underlines the need for a concomitant discussion about the details of an international burden-sharing regime. Still, decentralized grids based on RE have expanded and already improved energy access in developing countries. Under favorable conditions, cost savings in comparison to non-RE use exist, in particular in remote areas and in poor rural areas lacking centralized energy access. In addition, non-electrical RE technologies offer opportunities for modernization of energy services, for example, using solar energy for water heating and crop drying, biofuels for transportation, biogas and modern biomass for heating, cooling, cooking and lighting, and wind for water pumping. RE deployment can contribute to energy security by diversifying energy sources and diminishing dependence on a limited number of suppliers, therefore reducing the economy’s vulnerability to price volatility. Many developing countries specifically link energy access and security issues to include stability and reliability of local supply in their definition of energy security. Supporting the SD goal to mitigate environmental impacts from energy systems, RE technologies can provide important benefits compared to fossil fuels, in particular regarding GHG emissions. Maximizing these benefits often depends on the specific technology, management, and site characteristics associated with each RE project, especially with respect to land use change (LUC) impacts. Lifecycle assessments for electricity generation indicate that GHG emissions from RE technologies are, in general, considerably lower than those associated with fossil fuel options, and in a range of conditions, less than fossil fuels employing carbon capture and storage (CCS). The maximum estimate for concentrating solar power (CSP), geothermal, hydropower, ocean and wind energy is less than or equal to 100 g CO2eq/kWh, and median values for all RE range from 4 to 46 g CO2eq/kWh. The GHG balances of bioenergy production, however, have considerable uncertainties, mostly related to land management and LUC. Excluding LUC, most bioenergy systems reduce GHG emissions compared to fossil-fueled systems and can lead to avoided GHG emissions from residues and wastes in landfill disposals and co-products; the combination of bioenergy with CCS may provide for further reductions. For transport fuels, some first-generation biofuels result in relatively modest GHG mitigation potential, while most next-generation biofuels could provide greater climate benefits. To optimize benefits from bioenergy production, it is critical to reduce uncertainties and to consider ways to mitigate the risk of bioenergy-induced LUC. RE technologies can also offer benefits with respect to air pollution and health. Non-combustion-based RE power generation technologies have the potential to significantly reduce local and regional air pollution and lower associated health impacts compared to fossil-based power generation. Impacts on water and biodiversity, however, depend on local conditions. In areas where water scarcity is already a concern, non-thermal RE technologies or thermal RE technologies using dry cooling can provide energy services without additional stress on water resources. Conventional water-cooled thermal power plants may be especially vulnerable to conditions of water scarcity and climate change. Hydropower and some bioenergy systems are dependent on water availability, and can either increase competition or mitigate water scarcity. RE specific impacts on biodiversity may be positive or negative; the degree of these impacts will be determined by site-specific conditions. Accident risks of RE technologies are not negligible, but the technologies’ often decentralized structure strongly limits the potential for disastrous consequences in terms of fatalities. However, dams associated with some hydropower projects may create a specific risk depending on site-specific factors. The scenario literature that describes global mitigation pathways for RE deployment can provide some insights into associated SD implications. Putting an upper limit on future GHG emissions results in welfare losses (usually measured as gross domestic product or consumption foregone), disregarding the costs of climate change impacts. These welfare losses are based on assumptions about the availability and costs of mitigation technologies and increase when the availability of technological alternatives for constraining GHGs, for example, RE technologies, is limited. Scenario analyses show that developing countries are likely to see most of the expansion of RE production. Increasing energy access is not necessarily beneficial for all aspects of SD, as a shift to modern energy away from, for example, traditional biomass could simply be a shift to fossil fuels. In general, available scenario analyses highlight the role of policies and finance for increased energy access, even though forced shifts to RE that would provide access to modern energy services could negatively affect household budgets. To the extent that RE deployment in mitigation scenarios contributes to diversifying the energy portfolio, it has the potential to enhance energy security by making the energy system less susceptible to (sudden) energy supply disruption. In scenarios, this role of RE will vary with the energy form. With appropriate carbon mitigation policies in place, electricity generation can be relatively easily decarbonized through RE sources that have the potential to replace concentrated and increasingly scarce fossil fuels in the building and industry sectors. By contrast, the demand for liquid fuels in the transport sector remains inelastic if no technological breakthrough can be achieved. Therefore oil and related energy security concerns are likely to continue to play a role in the future global energy system; as compared to today these will be seen more prominently in developing countries. In order to take account of environmental and health impacts from energy systems, several models have included explicit representation of these, such as sulphate pollution. Some scenario results show that climate policy can help drive improvements in local air pollution (i.e., particulate matter), but air pollution reduction policies alone do not necessarily drive reductions in GHG emissions. Another implication of some potential energy trajectories is the possible diversion of land to support biofuel production. Scenario results have pointed at the possibility that climate policy could drive widespread deforestation if not accompanied by other policy measures, with land use being shifted to bioenergy crops with possibly adverse SD implications, including GHG emissions. 712 Renewable Energy in the Context of Sustainable Development Chapter 9 The integration of RE policies and measures in SD strategies at various levels can help overcome existing barriers and create opportunities for RE deployment in line with meeting SD goals. In the context of SD, barriers continue to impede RE deployment. Besides market-related and economic barriers, those barriers intrinsically linked to societal and personal values and norms will fundamentally affect the perception and acceptance of RE technologies and related deployment impacts by individuals, groups and societies. Dedicated communication efforts are therefore a crucial component of any transformation strategy and local SD initiatives can play an important role in this context. At international and national levels, strategies should include: the removal of mechanisms that are perceived to work against SD; mechanisms for SD that internalize environmental and social externalities; and RE strategies that support low-carbon, green and sustainable development including leapfrogging. The assessment has shown that RE can contribute to SD to varying degrees; more interdisciplinary research is needed to close existing knowledge gaps. While benefi ts with respect to reduced environmental and health impacts may appear more clear-cut, the exact contribution to, for example, social and economic development is more ambiguous. In order to improve the knowledge regarding the interrelations between SD and RE and to fi nd answers to the question of an effective, economically effi cient and socially acceptable transformation of the energy system, a much closer integration of insights from social, natural and economic sciences (e.g., through risk analysis approaches), refl ecting the different (especially intertemporal, spatial and intra-generational) dimensions of sustainability, is required. So far, the knowledge base is often limited to very narrow views from specifi c branches of research, which do not fully account for the complexity of the issue

Environmental Co‐Benefits of Maintaining Native Vegetation With Solar Photovoltaic Infrastructure

Abstract Co‐locating solar photovoltaics with vegetation could provide a sustainable solution to meeting growing food and energy demands. However, studies quantifying multiple co‐benefits resulting from maintaining vegetation at utility‐scale solar power plants are limited. We monitored the microclimate, soil moisture, panel temperature, electricity generation and soil properties at a utility‐scale solar facility in a continental climate with different site management practices. The compounding effect of photovoltaic arrays and vegetation may homogenize soil moisture distribution and provide greater soil temperature buffer against extreme temperatures. The vegetated solar areas had significantly higher soil moisture, carbon, and other nutrients compared to bare solar areas. Agrivoltaics in agricultural areas with carbon debt can be an effective climate mitigation strategy along with revitalizing agricultural soils, generating income streams from fallow land, and providing pollinator habitats. However, the benefits of vegetation cooling effects on electricity generation are rather site‐specific and depend on the background climate and soil properties. Overall, our findings provide foundational data for site preservation along with targeting site‐specific co‐benefits, and for developing climate resilient and resource conserving agrivoltaic systems

Shifts in hydropower operation to balance wind and solar will modify effects on aquatic biota

To avoid negative consequences to freshwater biota from climate change, society must complete the transition from fossil to renewable electricity sources. However, temporal patterns in hydropower generation (and flow releases that affect aquatic biota) may change with increased wind and solar penetration. We used power cost modeling to characterize current and future within-day and seasonal patterns in hydropower generation across the Eastern Interconnection in a wet and a dry year. Compared to the baseline, future hydropower generation across the grid decreased during the day and increased before dawn and after dusk. At a project level, such a pattern would suggest ‘double peaking’ operation (up- and down-ramping before dawn and after dusk, with lower releases midday). Variation in generation was higher in wet years than dry years, foreshadowing possible flow constraints on hydropower flexibility. At the grid scale, projected ramping rates were higher in all seasons. A review of the ecological literature suggests that these changes would shift the timing of invertebrate drift and elevate the risk of nest scouring during up-ramping and the risk of stranding or dewatering during down ramping. Thermal conditions may be moderated by increased ramping. Strategies for adapting to future shifts in the renewable portfolio range from re-regulation in reservoir cascades to providing flow refuge (structures and vegetation) below individual projects. Coordinated basin-scale operation can distribute peaking operation to maintain grid support while restricting local ramping at critical ecological times. In addition, research to design hybrid renewable systems that add battery storage is needed to understand how we can mitigate future risks to aquatic communities while promoting the use of renewable energy. This study, which is among the first to examine ecological side-effects of the shift to renewable energy in freshwater ecosystems, lays out a path toward understanding and navigating changes to flow regimes under the energy transition

Water use and supply concerns for utility-scale solar projects in the Southwestern United States.

As large utility-scale solar photovoltaic (PV) and concentrating solar power (CSP) facilities are currently being built and planned for locations in the U.S. with the greatest solar resource potential, an understanding of water use for construction and operations is needed as siting tends to target locations with low natural rainfall and where most existing freshwater is already appropriated. Using methods outlined by the Bureau of Land Management (BLM) to determine water used in designated solar energy zones (SEZs) for construction and operations&maintenance, an estimate of water used over the lifetime at the solar power plant is determined and applied to each watershed in six Southwestern states. Results indicate that that PV systems overall use little water, though construction usage is high compared to O&M water use over the lifetime of the facility. Also noted is a transition being made from wet cooled to dry cooled CSP facilities that will significantly reduce operational water use at these facilities. Using these water use factors, estimates of future water demand for current and planned solar development was made. In efforts to determine where water could be a limiting factor in solar energy development, water availability, cost, and projected future competing demands were mapped for the six Southwestern states. Ten watersheds, 9 in California, and one in New Mexico were identified as being of particular concern because of limited water availability

Water use and supply concerns for utility-scale solar projects in the Southwestern United States.

As large utility-scale solar photovoltaic (PV) and concentrating solar power (CSP) facilities are currently being built and planned for locations in the U.S. with the greatest solar resource potential, an understanding of water use for construction and operations is needed as siting tends to target locations with low natural rainfall and where most existing freshwater is already appropriated. Using methods outlined by the Bureau of Land Management (BLM) to determine water used in designated solar energy zones (SEZs) for construction and operations&maintenance, an estimate of water used over the lifetime at the solar power plant is determined and applied to each watershed in six Southwestern states. Results indicate that that PV systems overall use little water, though construction usage is high compared to O&M water use over the lifetime of the facility. Also noted is a transition being made from wet cooled to dry cooled CSP facilities that will significantly reduce operational water use at these facilities. Using these water use factors, estimates of future water demand for current and planned solar development was made. In efforts to determine where water could be a limiting factor in solar energy development, water availability, cost, and projected future competing demands were mapped for the six Southwestern states. Ten watersheds, 9 in California, and one in New Mexico were identified as being of particular concern because of limited water availability

If you build it, will they come? Insect community responses to habitat establishment at solar energy facilities in Minnesota, USA

Global declines in insect populations have important implications for biodiversity and food security. To offset these declines, habitat restoration and enhancement in agricultural landscapes could mutually safeguard insect populations and their pollination services for crop production. The expansion of utility-scale solar energy development in agricultural landscapes presents an opportunity for the dual use of the land for energy production and biodiversity conservation through the establishment of grasses and forbs planted among and between the photovoltaic solar arrays (‘solar-pollinator habitat’). We conducted a longitudinal field study across 5 years (2018–2022) to understand how insect communities responded to newly established habitat on solar energy facilities in agricultural landscapes by evaluating (1) temporal changes in flowering plant abundance and diversity; (2) temporal changes in insect abundance and diversity; and (3) the pollination services of solar-pollinator habitat by comparing pollinator visitation to agricultural fields near solar-pollinator habitat with other agricultural field locations. We found increases over time for all habitat and biodiversity metrics: floral rank, flowering plant species richness, insect group diversity, native bee abundance, and total insect abundance, with the most noticeable temporal increases in native bee abundance. We also found positive effects of proximity to solar-pollinator habitat on bee visitation to nearby soybean ( Glycine max ) fields. Bee visitation to soybean flowers adjacent to solar-pollinator habitat were comparable to bee visitation to soybeans adjacent to grassland areas enrolled in the Conservation Reserve Program, and greater than bee visitation to soybean field interior and roadside soybean flowers. Our observations highlight the relatively rapid (<4 year) insect community responses to grassland restoration activities and provide support for solar-pollinator habitat as a feasible conservation practice to safeguard biodiversity and increase food security in agricultural landscapes

The Land Sparing, Water Surface Use Efficiency, and Water Surface Transformation of Floating Photovoltaic Solar Energy Installations

Floating photovoltaic solar energy installations (FPVs) represent a new type of water surface use, potentially sparing land needed for agriculture and conservation. However, standardized metrics for the land sparing and resource use efficiencies of FPVs are absent. These metrics are critical to understanding the environmental and ecological impacts that FPVs may potentially exhibit. Here, we compared techno-hydrological and spatial attributes of four FPVs spanning different climatic regimes. Next, we defined and quantified the land sparing and water surface use efficiency (WSUE) of each FPV. Lastly, we coined and calculated the water surface transformation (WST) using generation data at the world’s first FPV (Far Niente Winery, California). The four FPVs spare 59,555 m2 of land and have a mean land sparing ratio of 2.7:1 m2 compared to ground-mounted PVs. Mean direct and total capacity-based WSUE is 94.5 ± 20.1 SD Wm−2 and 35.2 ± 27.4 SD Wm−2, respectively. Direct and total generation-based WST at Far Niente is 9.3 and 13.4 m2 MWh−1 yr−1, respectively; 2.3 times less area than ground-mounted utility-scale PVs. Our results reveal diverse techno-hydrological and spatial attributes of FPVs, the capacity of FPVs to spare land, and the utility of WSUE and WST metrics