Tag Archive for: Solar

The International Landscape of Solar Farms and Agrivoltaics

Rebecca A. Efroymson, Environmental Scientist, Oak Ridge National Laboratory); and Jonathan M. O. Scurlock, Chief Adviser for Renewable Energy & Climate Change, National Farmers’ Union of England and Wales

Solar photovoltaic (PV) power, the most popular form of renewable energy on farms, is being adopted all over the world. Growers and processors of food worldwide have a long history of using the sun’s energy to produce and dry their crops, and solar PV is adding a modern twist to our relationship with the sun. It is no surprise that some of the best locations on Earth for harnessing solar energy are often ideal places for agriculture and horticulture. However, intelligent design for multi-purpose land use can alleviate real or perceived conflicts between energy and food production. Solar modules can shade crops where light intensity is in excess of crop requirements, reducing water evaporation; they can be mounted on agricultural buildings to power farm business energy needs; and they can export low-carbon electricity to meet wider demands for “green” power and the transition to a “net zero” global economy.

We use the term agrivoltaics broadly to describe any combination of agricultural activity and solar electricity production, but outside the USA, the term usually refers more specifically to the intimate juxtaposition of solar modules and agricultural land use. Examples include PV modules mounted at a height of several meters to allow access to land below by farm machinery or large livestock, where they provide shelter from storms or excessive solar radiation, and the integration of solar PV into greenhouses for crop protection.

We caught up with a range of projects across three continents to report upon their objectives and their future prospects.

Around 30% of British farmers have either rooftop or ground-mounted solar energy. The National Farmers Union (NFU) aspires to the goal that every farmer and grower have the opportunity to become a net exporter of low-carbon energy. The falling capital cost of both solar and battery electricity storage has resulted in a growing pipeline of solar installations across a range of sizes, including large 100-hectare (ha) and 1,000-ha solar farm projects, largely independent of government policy support. The NFU advises farmers that solar PV can be deployed across entire fields, as small, ground-mounted installations around field margins or adjacent to farmyards, on farm buildings, and on domestic rooftops. Developers of solar farms are encouraged by the NFU to follow best practice guidelines for multi-purpose land use, combining energy production, continued agricultural management such as grazing, and creation of wildlife habitat. NFU’s strong preference is for large-scale solar farm development to be located on lower-quality agricultural land, avoiding as much as possible the most productive and versatile soils. Roof-mounted solar systems in Britain continue to offer a sound investment, making between 10% and 25% simple return on capital annually at current electricity prices, depending on how much of the generated power is used on-site. At of the end of 2021, about 70% of the United Kingdom’s 14 gigawatts of solar power generation capacity was located in the agricultural sector.

Multi-purpose land use – sheep grazing and hedgerows of natural vegetation around a large (44-megawatt) solar farm near Haverfordwest in the United Kingdom. Photo Credit: Jonathan Scurlock

In the Netherlands, the Symbizon project at Almere, near Amsterdam, has brought together a Swedish energy company with Dutch researchers and a private organic farm to construct a 700-kilowatt solar park with alternating strips of PV modules and rows of crops. Starting in spring 2023, the production of herbs will be investigated, and potatoes, beans, beetroot, broccoli, and grains may be included in this pilot study. Pivoting double-sided (bifacial) solar modules will catch the reflected light from soil and crops.

Nearby in Germany, Goldbeck Solar is an innovator in solar agrivoltaic structures. The company has developed a system of solar PV arches that slide on side rails, allowing farmers to shelter or expose various crops. Typically oriented east to west for maximum solar energy yield, the arches span up to 9 meters, at a height of 2.5 to 3 meters, allowing a degree of control over temperature, humidity, and light. These agrivoltaic modules can also provide shelter for livestock from extreme weather, such as high temperatures and hail. The modules are currently undergoing trials in the four-year Sunbiose project in the Netherlands, which had already succeeded in growing raspberries under the partial shelter of solar PV modules. 

Agrivoltaics are being tested in East Africa, where their shade can reduce heat stress and water loss, and farmer incomes in disadvantaged rural communities may be improved. An experimental facility opened in 2022 in Insinya, Kenya, through partnership with Universities of Sheffield, York and Teesside in the United Kingdom, the Stockholm Environment Institute, World Agroforestry, the Centre for Research in Energy and Energy Conservation, and the African Centre for Technology Studies. Some 180 PV modules, each 345 watts, have been installed about 3 meters above the ground, allowing a variety of crops to be grown under the shade from the strong equatorial sun. Geoffrey Kamadi of The Guardian reports that benefits include improved yields of cabbage, eggplant, and lettuce; a reduction in water loss; and a reduction in high daytime temperatures and UV damage.

Small-scale agrivoltaic development (less than 0.1 ha) has progressed rapidly in Japan, producing 0.8% of the total solar power generated in the country in 2019. Japan has perhaps the greatest number of agrivoltaic farms to date, with more than 120 plant species being cultivated on agrivoltaic farms. The Solarsharing Network provides a catalog of 27 agricultural crops (Solar Sharing for FUN | SOLAR SHARING NETWORK| Solar Sharing Association of Japan (solar-sharing.org) and their light needs. Innovative crop systems include tea, according to Makoto Tajima and Tetsunari Lida of the Institute for Sustainable Energy Policies.

One pilot agrivoltaic project in New Zealand is seeking low-growing flowering plants like alyssum to attract bees and reflect light up to rows of bifacial PV modules. The high energy demand of irrigation systems can benefit from on-farm solar energy. In New Zealand, as in the U.S., UK, and Australia, sheep and other small livestock graze under solar modules, avoiding the need for mowing. As New Zealand reporter Delwyn Dickey notes, the success of such large-scale agrivoltaic systems (i.e., solar farms) may be determined by an insistence upon dual land use during the consenting process and the willingness of solar energy development companies to adopt dual land use.

Clearly, from small-scale intimate mingling of solar PV with agricultural production to multi-purpose land use in the largest of solar farms, the merits of harvesting the sun’s energy twice are appreciated the world over. The outlook for agrivoltaics is bright indeed.

AgriSolar News Roundup: Tomatoes in California, Agrisolar Research in the Southwest, Symbizon Project in Netherlands 

Research Suggests Agrivoltaics Could Help California’s Tomato Industry 

“Emerging research suggests growing tomato plants below and between solar panels could help the country’s billion-dollar-plus tomato industry, especially in places where it faces increasing stress from heat and drought. Shade provided by solar panels can help conserve water, create humidity, and lower temperatures that can become too much even for heat-loving tomatoes.” – Energy News Network  

Research Shows That Crops and Solar Panels Are Highly Compatible 

“By elevating solar panels far enough above the ground so people, plants, and animals can operate underneath, we can ‘essentially harvest the sun twice,’ says University of Arizona researcher Greg Barron-Gafford. Enough sunlight to grow crops gets past the panels, which also act as a shield against extreme heat, drought, and storms. 

Barron-Gafford and his team were able to triple the yield of chiltepin peppers, wild chiles common to the area, by growing them under PV panels on test plots vs. unshaded control plots; cherry tomato output doubled. What’s more, the soil on the PV plots retained 5 to 15 percent more moisture between waterings. ‘The plants aren’t just freeloading under the solar,’ adds Barron-Gafford; they actually help the panels become more efficient. ‘Every time plants open their pores to let carbon dioxide in, water escapes,’ he explains. This lowers the temperature beneath the panels—the same way restaurant misters make outdoor dining bearable in scorching heat. The cooling effect, the researchers calculated, resulted in a 3 percent bump in electricity production during the growing season.” – Mother Jones 

Symbizon Project Aims to Find New Ways to Combine Agriculture and Solar 

“During a four-year pilot project, Dutch independent research organization TNO, in collaboration with Vattenfall and Aeres University of Applied Sciences (UAS), is developing a sun tracking algorithm that monitors various factors, such as crop yield, energy yield and the effects of herb strips, weather forecast, energy price and soil condition.”  – Vattenfall 

Rainwater Management in Agrivoltaic Systems – Research & Development Potential

Agrivoltaics is a concept in which a piece of land is simultaneously used for both energy and food production by mounting photovoltaic modules at a certain height above (or in between strips of) agricultural land. A local and system-level incorporation of water management is imperative to the sustainable implementation of agrivoltaics. Water raining on the module can be gathered and used for distinct purposes: groundwater recharge, crop irrigation, and cleaning and cooling of the PV modules. This research provides an initial overview of positive and negative impacts for each water use concept and outlines issues that should be taken into consideration and the potential for research and development. Various Managed Aquifer Recharge (MAR) technologies are a way to clean and store the water periodically in an underlying aquifer. Irrigation increases yield within the plant level and therefore increases the system’s output. Thanks to the power supply generated by the PV modules, high-tech irrigation systems can be implemented in agrivoltaic systems; the special adaption of irrigation systems to agrivoltaics poses significant potential for research and development. Meanwhile, the necessity, i.e., profitability of cleaning and/ or cooling PV modules depends on local environment and economic factors. Several cleaning techniques have been developed to mitigate soiling, ranging from manual cleaning to fully automatic cleaning systems. In agrivoltaics systems, the soiling risk can increase. Semi-automatic systems seem to have the greatest potential for agrivoltaics, because they can be used with farming equipment. Multiple cooling techniques have been developed to decrease cell temperature to increase power output, with some of them involving water. Water flowing over the module surface is a promising a promising cooling technique for agrivoltaic applications. Attaching a perforated tube to the upper edge, the entire module can be covered in a thin film of water which cools very effectively (while also cleaning the surface). A closed-circuit system could be created involving the technical components used for rainwater harvesting. The economic feasibility of cooling panels in agrivoltaic systems needs to be investigated. In certain locations, rainwater-harvesting could also be relevant for ground-mounted PV systems.

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Decommissioning Solar Energy Systems Resource Guide

When solar projects reach the end of their expected performance period, there are several management options. They include extending the performance period through reuse, refurbishment, or repowering of the facility or fully discontinuing operations and decommissioning the project. In this resource guide, the Center for Rural Affairs briefly expands upon these options as well as potential decommissioning plans, followed by suggestions for county governments once the decision to decommission a project has been made.

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Genetic Algorithms-Based Optimum PV Site Selection Minimizing Visual Disturbance

In this paper, an integrated methodology is developed to determine optimum areas for Photovoltaic (PV) installations that minimize the relevant visual disturbance and satisfy spatial constraints associated with land use, as well as environmental and techno-economic siting factors. The visual disturbance due to PV installations is quantified by introducing and calculating the “Social Disturbance” (SDIS) indicator, whereas optimum locations are determined for predefined values of two siting preferences (maximum allowable PV locations—grid station distance and minimum allowable total coverage area of PV installations). Thematic maps of appropriate selected exclusion criteria are produced, followed by a cumulative weighted viewshed analysis, where the SDIS indicator is calculated. Optimum solutions are then determined by developing and employing a Genetic Algorithms (GAs) optimization process. The methodology is applied for the municipality of La Palma Del Condado in Spain for 100 different combinations of the two siting preferences. The optimization results are also employed to create a flexible and easy-to-use web-GIS application, facilitating policy-makers to choose the set of solutions that better fulfils their preferences. The GAs algorithm offers the ability to determine distinguishable, but compact, regions of optimum locations in the region, whereas the results indicate the strong dependence of the optimum areas upon the two siting preferences.

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AgriSolar News Roundup: Agrivoltaic Research in Australia, Solar and Farmland Compatibility, Agrisolar Development in Oregon

Australian Researchers Develop Solar Panels Optimized for Agrisolar  

“University of New South Wales researchers have teamed up with Tindo Solar to develop a line of semi-transparent modules, specialized for agrivoltaic cropping, which will use nanoparticles tuned to capture different parts of the light spectrum. ‘There is evidence you don’t need the full spectrum and some plants will work even better if you provide them with only part of the spectrum,’ project lead and UNSW Associate Professor Ziv Hameiri tells PV Magazine Australia. Crucially, he says, the project will also open a line between farmers, solar researchers and industry, creating the potential for mutual benefits.”  – PV Magazine 

Agrisolar Operations Show That Solar Does Not Compete with Farmland 

“In short, Agrivoltaics is a rapidly growing branch of the energy transition. It is being applied to all manner of crops across the world. All kinds of benefits are emerging, with China even using it to reverse desertification. Not only is it expanding clean energy production, it is providing a vital second income stream for farmers. Banning it would cut off a really important opportunity for Britain’s farmers, at a time when rural poverty is a real issue.” – Green Peace 

Oregon State Develops 5-Acre Agrisolar Project 

“Oregon State University has started construction on a $1.5 million research project to optimize dual-use, co-developed land hosting solar photovoltaic arrays and agriculture. The five-acre Solar Harvest project is located at Oregon State’s North Willamette Research and Extension Center in Aurora, Oregon, 20 miles south of Portland. The 326-kW project is the result of a partnership between Oregon State and the Oregon Clean Power Cooperative, which developed the solar array and financed the construction of the solar array.” – Solar Power World 

Global energy assessment of the potential of photovoltaics for greenhouse farming

Agrivoltaic (APV) systems have emerged as a promising solution to reduce the land-use competition between PV technology and agriculture. Despite its potential, APV is in a learning stage and it is still necessary to devote big efforts to investigate its actual potential and outdoor performance. This work is focused on the analysis of APV systems in agriculture greenhouses at global scale in terms of energy yield. In this study, a novel dual APV model is introduced, projected in four representative locations with a high crop cultivation greenhouse implantation, i.e. El Ejido (Spain), Pachino (Italy), Antalya (Turkey) and Vicente Guerrero (Mexico), and for 15 representative plant cultivars from 5 different important socioeconomic families of crops, i.e. Cucurbitaceae, Fabaceae, Solanacae, Poaceae, Rosaceae. At this stage, semi-transparent c-Si PV technology has been considered due its high efficiency and reliability. The results show that APV systems could have a transparency factor around 68% without significantly affecting the total crop photosynthetic rate. Taking this into account, APV systems would produce an average annual energy around 135 kWh/m2, and values around 200 kWh/m2 under a favorable scenario. This could represent a contribution to the total market share between 2.3% (Mexico) and 6% (Turkey), and up to 100% of the consumption demand of greenhouses equipped with heating and cooling (GSHP), and lighting.

Global energy assessment of APV PotentialDownload

Technoecologies of Solar Commoning: Activating the Immanent Potentials of Solar Infrastructure, Practices and Affect

In the context of accelerated climate crisis this article investigates the energetic-political possibilities of solar energy in the Czech Republic. In the absence of solar cooperatives, the article examines residential PV installations and a ground-mounted solar mono-plantation as a terrain for possible commoning. It proposes technoecologies as a framework and tool to not only focus on what solar infrastructure brings together, but also what is left out or disarticulated in specific arrangements but can be seen as infrastructure’s productive “limits” that entail possibilities for differential inclusion, regeneration, and care. Ethnographic technoecological analysis shows how unexpected plant growth within the plantation points to multispecies refuges transforming the electric monoculture, and how electrical rewiring could connect PV arrays to households in multiple occupancy buildings (paneláky) in ways that enable new forms of sharing and joyful squandering of electricity in times of energy abundance.

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Energetic Comparison of Vertical Bifacial to Tilted Monofacial Solar

In this article, a vertical bifacial + reflector configuration is presented as a candidate for solar canals and other applications that allow dual use of the land. Modeling with weather data from Merced, CA shows output to be competitive with fixed 20° tilt systems, with south-facing vertical orientation showing 117% and 87% of annual output of south-facing 20° systems with and without a reflector, respectively. Repetition with weather data from Houston, Denver, and Miami produces similar results, with values ranging from 112%–121% and 82%–94%, which serve as conservative estimates due to lack of modeled soiling on tilted systems in the latter comparison. South-facing vertical orientations have better performance in nonsummer months relative to other systems, resulting in a flatter seasonal curve, with useful implications for load balancing and energy storage. East- and west-facing vertical orientations outperform their fixed tilt defaults, even without a reflector, and tolerate higher dc/ac inverter ratios than similar south-facing vertical orientations before appreciable clipping effects are seen.

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Homeowner’s Guide to the Federal Tax Credit for Solar Photovoltaics

This guide provides an overview of the federal investment tax credit for residential solar photovoltaics (PV). The federal residential solar energy credit is a tax credit that can be
claimed on federal income taxes for a percentage of the cost of a solar PV system paid for by the taxpayer.

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