Tag Archive for: Solar

In this Teatime from April 21, 2022, Tom Murphy, the Director of Penn State’s Marcellus Center for Outreach and Research (MCOR), presents Leasing for Community and Grid Scale Solar – Key Consideration While Negotiating.  Tom’s current work is as an educational consultant in transitioning to clean energy including utility and community scale solar.   Teatimes are a series of educational agrivoltaic webinar presentations that are jointly run by The AgriSolar Clearinghouse and the American Solar Grazing Association.

By Lee Walston and Heidi Hartmann, Argonne National Laboratory

Pollinator habitat at a solar facility in Minnesota. Photo: Lee Walston, Argonne National Laboratory.

Many of us have witnessed regional land-use transformations towards renewable energy in the last decade. As the fastest growing electricity generating sector in the U.S., solar energy development has grown more than 20x in the past decade and is projected to be the dominant renewable source of electricity by 2040. The recent DOE Solar Futures Study predicts that over 1 terawatt (TW) of utility-scale solar electricity developments will be required to meet net-zero clean-energy objectives in the U.S. by 2050 (Figure 1). This represents a solar land-use footprint of over 10 million acres across the U.S. – roughly the combined area  of Connecticut, Massachusetts, and Rhode Island.

Figure 1. Source: Solar Futures Study

A fundamental question we all face is how to balance solar energy development with other land uses such as agriculture. Given the current and projected land-use requirements, sustained development of solar energy will depend on finding renewable energy solutions that optimize the combined outputs of energy production, ecosystem services, and other land uses. Dual land-use approaches that co-locate solar energy with other forms of land uses, such as agriculture or habitat restoration, have emerged as promising strategies to improving the landscape compatibility of solar energy. The establishment of native pollinator-friendly vegetation at solar facilities (“solar-pollinator habitat”) is one strategy to improve the multifunctionality of these lands that not only provide renewable energy but also offer several ecosystem service benefits such as: (1) biodiversity conservation; (2) stormwater and erosion control; (3) carbon sequestration; and (4) benefits to nearby agricultural fields.

Understanding the true ecosystem service benefits of solar-pollinator habitat will require field studies in different geographic regions to examine the methods of solar-pollinator habitat establishment and link these processes with measured ecosystem service outputs. Given the time required to conduct these direct field studies, most discussions of solar-pollinator habitat thus far have centered on qualitative ecosystem outcomes. Fortunately, there are ways to quantitatively understand some of these potential outcomes. Native habitat restoration has been a focus of scientific research for many years, and we can use these studies to understand the regional methods for solar pollinator habitat establishment (e.g., types of seed mixes, vegetation management) and relate these habitat restoration activities with quantifiable ecosystem responses. For example, there are decades of research on the restoration of the prairie grassland systems in the Midwest and Great Plains – regions that have seen losses of over 90% of their native grasslands due to agricultural expansion.

Because many solar facilities in the Midwest are sited on former agricultural fields, research on ecological restoration of former agricultural fields could be very useful in understanding the establishment and performance of solar-pollinator habitat in the same region. We can look to these studies as surrogate study systems for solar-pollinator habitat and utilize the data from these studies to make inferences on the ecosystem outcomes of solar-pollinator habitat. Along with a team of research partners, we recently took this approach to quantify the potential ecosystem services of solar-pollinator habitat in the Midwest. Our goal was to understand how solar energy developments co-located with pollinator-friendly native vegetation may improve ecosystem services compared to other traditional land uses. We began by reviewing the literature to collect a range of data on vegetation associated with three different land uses: agriculture, solar-turfgrass, and solar-pollinator habitat. The data for each land use included information on vegetation types, root depths, carbon storage potential, and evapotranspiration, to name a few.  

We then developed ecosystem service models for each land use scenario. The land uses corresponded to the following scenarios (Figure 2):

1. Agriculture scenario (baseline “pre-solar” land use);

2. Solar-turfgrass (“business as usual” solar-turfgrass land use) and

3. Solar-pollinator habitat (grassland restoration at solar sites).

We mapped and delineated 30 solar sites in the Midwest and used the InVEST modeling tool to model the following four ecosystem services across all sites and land-use scenarios:

Figure 2. Illustration of land use scenarios at each solar site. Source: Walston et al., 2021.

Our results, published in the journal Ecosystem Services, found that, compared to traditional agricultural land uses, solar facilities with sitewide co‑located, pollinator‑friendly vegetation produced a three-fold increase in pollinator habitat quality and a 65% increase in carbon storage potential. The models also showed that solar-pollinator habitat increased the site’s potential to control sedimentation and runoff by more than 95% and 19%, respectively (Figure 3). This study suggests that in regions where native grasslands have been lost to farming and other activities native grassland restoration at solar energy facilities could represent a win‑win for energy and the environment.

What do these results mean? We hope these results can help industry, communities, regulators, and policymakers better understand the potential ecosystem benefits of solar-pollinator habitat. These findings may be used to build cooperative relationships between the solar industry and surrounding communities to better integrate solar energy into agricultural landscapes. While our study provides a quantitative basis for understanding these potential ecosystem benefits, additional work is needed to validate model results and collect the primary data that would support economic evaluations to inform solar-native grassland business decisions for the solar industry and quantify the economic benefits of services provided to nearby farmers, landowners, and other stakeholders.

Figure 3. Average ecosystem service values for the thirty Midwest solar facilities modeled with InVEST: (A) pollinator supply; (B) carbon storage; (C) sediment export; and (D) water retention. Source: Walston et al. 2021.

Several agricultural farms in Nigeria are found in off-grid locations where there is the lack of water supply despite the abundant groundwater resources possessed by the country. Since water is one of the key resources for agricultural production, majority of the farms only resort to the use of fossil fuel-powered generators to pump water for their operations in Nigeria. However, concerns about the frequent increase in fuel cost, the maintenance, and the environmental issues associated with running fossil-fuel generators have driven the need for a clean and sustainable energy source. The photovoltaic (PV) pumping system is becoming more popular as an alternative energy source of water pumping for irrigation farming. This study presents the effects of total system head and solar radiation on the techno-economic design of PV-pumping system for groundwater irrigation of crop production in Nigeria. It also calculates the quantity of emissions avoided by the PV. The technical design is based on standard methodology to determine the PV capacity that can operate the pump to satisfy the daily water requirements for the crops, while the economic aspect involves the assessment of the life cycle cost and the cost of water per m3. The result reveals that the pump power ranges from 0.158 kW to 0.293 kW and the PV power ranges from 1.90 kW to 3.52 kW for a system head of 10 m and solar irradiation of 5.25 kWh/m2/day, respectively, while the unit cost of water ranges from $0.05/m3 to $0.054/m3, and the life cycle cost ranges from $7004 to $12331. This provides insights into the effects of varying the system head and the solar radiation, demonstrating that the PV-pumping system underperforms at higher system heads, but performs effectively at higher solar radiation. This is due to the decrease in the discharge rate and an increase in power output, respectively. The study will be useful for planning PV-based water pumping system for agricultural purposes. Adopting this method of supplying crop water requirements will go a long way to guarantee food security in Nigeria and other developing countries with similar climate and economic situations. Such a method is expected to lead to zero hunger in the country in the long-run.

A lot of economic analyses have been conducted in the last ten years to establish the most cost-effective solution for irrigation and evaluation of the project profitability. The benefits generated by the PVWP providing water by a submersible pump located inside a deep well have been highlighted for Divjaka region. The solar potential in the site is quite enough to be used to pump water from the deep well into the tank positioned at an effective altitude which can provide the water quantity and pressure by gravity. The study shows that installing a PVWP system represents the best technical and economic solution to drive a water pump that provides water for sprinkler irrigation. The economic benefits have been also addressed, evaluating the energy production and distribution throughout the year and the specific cost per m3 of water supplied (€/m3). Renewables are the key to enhance food and water security, drive agri-food productivity, leading to socioeconomic benefits in recovering from post-Covid-19. By combining our knowledge, data collected, surveys together can contribute to economic growth of our community-ensuring access to clean and affordable energy and raising the standard of living of rural and most vulnerable communities. In the area there are used two types of water pumping for irrigation purposes: Diesel driven water pumps and electricity powered water pumps. Both systems are very costly due to the high fuel cost and on the other hand self-investment to bring electricity from the national distribution lines are needed. The study shows very good results compared to the existing water pump systems (totally based on fossil or electricity from the grid) applied for irrigation purposes in Albania. Further investment in RES is essential for agri-food systems transformation and development, climate resilience and net-zero strategies by 2030 in Albanian context, as the majority of the rural population lies their economy on agriculture. The use of this kind of system could have an important contribution in the diversification of energy sources, mitigation of GHG, social and economic development of our country.

The purpose of this guide is to help Michigan communities meet the challenge of becoming solar ready by addressing SES within their planning policies and zoning regulations. This document illustrates how various scales and configurations of photovoltaic SES fit into landscape patterns ranging between rural, suburban, and urban.

This research presents a highly transparent concentrator photovoltaic system with solar spectral splitting for dual land use applications. The system includes a freeform lens array and a planar waveguide. Sunlight is first concentrated by the lens array and then reaches a flat waveguide. The dichroic mirror with coated prisms is located at each focused area at the bottom of a planar waveguide to split the sunlight spectrum into two spectral bands. The red and blue light, in which photosynthesis occurs at its maximum, passes through the dichroic mirror and is used for agriculture. The remaining spectrums are reflected at the dichroic mirror with coated prisms and collected by the long solar cell attached at one end of the planar waveguide by total internal reflection. Meanwhile, most of the diffused sunlight is transmitted through the system to the ground for agriculture. The system was designed using the commercial optic simulation software LightTools™ (Synopsys Inc., Mountain View, CA, USA). The results show that the proposed system with 200× concentration can achieve optical efficiency above 82.1% for the transmission of blue and red light, 94.5% for diffused sunlight, which is used for agricultural, and 81.5% optical efficiency for planar waveguides used for power generation. This system is suitable for both high Direct Normal Irradiance (DNI) and low DNI areas to provide light for agriculture and electricity generation at the same time on the same land with high efficiency.

The increasing pressure on land resources for food and energy production along with efforts to maintain natural systems necessitates the development of compatible land uses that maximize the co-benefits of multiple ecosystem services. One such land sharing opportunity is the restoration and management of native grassland vegetation beneath ground-mounted solar energy facilities, which can both protect biodiversity and restore related ecosystem services. In this paper, the researchers applied the InVEST modeling framework to investigate the potential response of four ecosystem services (carbon storage, pollinator supply, sediment retention, and water retention) to native grassland habitat restoration at 30 solar facilities across the Midwest United States. Compared to pre-solar agricultural land uses, solar-native grassland habitat produced a 3-fold increase in pollinator supply and a 65% increase in carbon storage potential. The researchers also observed increases in sediment and water retention of over 95% and 19%, respectively. They applied these results to project the potential benefits of adoption of native grassland management practices in current and future solar energy buildout scenarios. Their study demonstrates how multifunctional land uses in agriculture-dominated landscapes may improve the provision of a variety of ecosystem services and improve the landscape compatibility of renewable energy and food production. These findings may be used to build cooperative relationships between the solar industry and surrounding communities to better integrate solar energy into agricultural landscapes.

Colloidal quantum dots (QDs) are nanometer-sized semiconductor crystals grown via low-cost solution processing routes for a wide array of applications encompassing photovoltaics, light-emitting diodes (LEDs), electronics, photodetectors, photocatalysis, lasers, drug delivery, and agriculture. A comprehensive technoeconomic cost analysis of perovskite quantum dot optoelectronics is reported. Using economies-of-scale considerations based on price data from prominent materials suppliers, we have highlighted that increased QD synthesis yield, solvent recycling, and synthesis automation are critical to market adoption of this technology and driving quantum dot film fabrication costs down from >$50/m^2 to ∼$2−3/m^2

Decomposition models of solar irradiance estimate the magnitude of diffuse horizontal irradiance from global horizontal irradiance. These two radiation components are well-known to be essential for the prediction of solar photovoltaic systems performance. In open-field agrivoltaic systems, that is the dual use of land for both agricultural activities and solar power conversion, cultivated crops receive an unequal amount of direct, diffuse and reflected photosynthetically active radiation (PAR) depending on the area they are growing due to the non-homogenously shadings caused by the solar panels installed (above the crops or vertically mounted). It is known that PAR is more efficient for canopy photosynthesis under conditions of diffuse PAR than direct PAR per unit of total PAR. For this reason, it is fundamental to estimate the diffuse PAR component in agrivoltaic systems studies to properly predict the crop yield.

Solar electricity from solar parks in rural areas are cost effective and can be deployed fast therefore play an important role in the energy transition. The optimal design of a solar park is largely affected by income scheme, electricity transport capacity, and land lease costs. Important design parameters for utility-scale solar parks that may affect landscape, biodiversity, and soil quality are ground coverage ratio, size, and tilt of the PV tables. Particularly, low tilt PV at high coverage reduces the amount of sunlight on the ground strongly and leads to deterioration of the soil quality over the typical 25-year lifetime. In contrast, vertical PV or an agri-PV designed fairly high above the ground leads to more and homogeneous ground irradiance; these designs are favored for pastures and croplands. In general, the amount and distribution of ground irradiance and precipitation will strongly affect which crops can grow below and between the PV tables and whether this supports the associated food chain. As agrivoltaics is the direct competition between photosynthesis and photovoltaics. Understanding when, where and how much light reaches the ground is key to relate the agri-PV solar park design to the expected agricultural and electricity yields. We have shown that by increasing the minimum height of the system, decreasing the size of the PV tables and decreasing the coverage ratio, the ground irradiance increases, in particular around the gaps between the tables. The most direct way of increasing the lowest irradiance in a solar park design is to use semi-transparent PV panels, such as the commercially available bifacial glass-glass modules. In conclusion: we have shown that we can achieve similar ground irradiance levels in an east- and west-facing design with 77% ground coverage ratio as is achieved by a south-facing design at 53% coverage.