Agrivoltaism: A Win-win System?

Is agrivoltaism a win-win system? Installing solar panels on top of agricultural crops through the agrivoltaic system provides many benefits, but it also gives birth to many controversies.

Community policies provide for a clear and real coordination of energy crops and those intended for food, so that each country can establish the destination of the adequate land use, to provide a sustainable gain for both parts – food and energy.

Renewable energy sources are a priority for the European Union, especially in the context of climate challenges. Energy production has never been so important for the strategic autonomy of Europe, believes Thierry Breton, Commissioner for the Internal Market of the European Union.

Agrivoltaism allows to keep agricultural land and use the land areas for the development of renewable energy. The importance of photovoltaic panels in the carbon neutrality policy by 2050 should not be neglected either, reconciling the climate and industrial ambitions of the European Union.

 

Solar energy on agricultural land at European level

Currently, solar power is a very important source of renewable and sustainable energy, capitalized through an ever-evolving technology range. The cell used to make modules five years ago, for example, is no longer used today. Therefore, constant innovation is needed.

At the CEA-Liten Institute (The French Alternative Energies and Atomic Energy Commission), the first European research centre fully dedicated to energy transition, a contribution is made to the development of new-generation cells with a much higher efficiency than those available on the current market. The mass market is currently offering efficiency levels between 22 and 23% for the conversion of sunlight into electricity. Work is being done on a generation that could reach an efficiency of 25%, while preparing the next generation that is expected to exceed efficiencies of 30%. This is known as a tandem cell approach, which involves combining two types of material, one based on silicon while the other is organic. European academics are also working a new PV module project suitable for desert environments, as well as other research and innovation projects within the scope of the Horizon Europe framework program.

PV cell improvement

Because of rising concern about the impact of fossil fuel-based energy on global warming and climate change, photovoltaic cell technology has advanced significantly in recent years as a sustainable source of energy.

To date, photovoltaic cells have been split into four generations, with the first two generations accounting for most of the current market.

First generation of thin-film technologies is based on monocrystalline or polycrystalline silicon and gallium arsenide cells and includes well-known medium- or low-cost technologies with moderate yields, whereas second generation includes devices with lower efficiency and manufacturing costs.

Third generation is based on novel materials and has a wide range of design options, as well as expensive but highly efficient cells. However, fourth generation, also known as “inorganics-in-organics,” combines the low cost and flexibility of polymer thin films with the durability of innovative inorganic nanostructures (metal nanoparticles or metal oxides) in organic-based nanomaterials (Materials for Photovoltaics: Overview, Generations, Recent Advancements and Future Prospects by Muhammad Aamir Iqbal, Maria Malik, Wajeehah Shahid, Syed Zaheer Ud Din, Nadia Anwar, Mujtaba Ikram and Faryal Idrees/January 20th, 2022).

Third-generation PV cells

These organic semiconductors or dye-sensitized solar cells could be interesting in that they could contribute to the production of electricity outside the spectral regions required for plant photosynthesis (especially the red and blue spectral bands of the visible spectrum). They could be considered photo-selective covers.

These cells could be particularly suitable for existing infrastructures such as greenhouses, where they could be, for example, attached to the wall. Despite the features that seem promising in terms of flexibility, brightness, colour diversity, degree of transparency and environmental costs, these technologies are not yet stable or efficient enough to convert solar energy into electricity.

Concentrator cells

The technology of luminescent solar concentrators (such as those developed by the Swiss company Insolight) aims to focus a beam of light on a given point of a photovoltaic cell, thanks to optical lenses, to maximize its intensity. The interest of these concentrator cells would also lie in their ability to separate direct light from diffuse light (the latter being able to be transmitted to crops).

The cells would be able to track the sun by moving horizontally a few millimetres per day to keep the cells aligned with the component of the light beam. These technologies are still in the development stage, being relatively expensive and relatively difficult to implement, given the precision required in moving the cells to ensure alignment with the light beam.

Insolight’s first agrivoltaic pilot installation in France is completed. The pilot uses insolagrin dynamic agrivoltaic solution over strawberries. The project was created in partnership with Amarenco and Invenio. Energesia is the photovoltaic installer for the project.

Perovskites could take solar cells to new heights

Researchers at the U.S. Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL) made a technological breakthrough and constructed a perovskite solar cell with the dual benefits of being both highly efficient and highly stable.

The work was done in collaboration with scientists from the University of Toledo, the University of Colorado-Boulder, and the University of California-San Diego.

A unique architectural structure enabled the researchers to record a certified stabilized efficiency of 24% under 1-sun illumination, making it the highest reported of its kind. The highly efficient cell also retained 87% of its original efficiency after 2,400 hours of operation at 55 degrees Celsius.

Perovskite, which refers to a crystalline structure, has emerged in the last decade as an impressive means to efficiently capture sunlight and convert it to electricity. Research into perovskite solar cells has been focused to a large degree on how to increase their stability.

Instruments and technologies under development

Photovoltaic panels technologies are constantly evolving. These technologies are obviously not specific to agrivoltaics as such – some research focuses on improving the efficiency of PV panels – but it is always interesting to follow the trends.

Some operators have started to implement three-dimensional photovoltaic tables that can be moved and integrate photovoltaic modules directly into their structure.

Mobile solar units are also starting to appear. These units can be designed of as pre-assembled solar panels in a container – the container consists of 200 pre-assembled and pre-wired PV panels that can be quickly installed and moved. Although these units were initially designed for disaster areas, they could be used in complex cropping or lever systems.

 

Semi-transparent tables

Unlike conventional opaque tables, semi-transparent tables contain conventional PV cells, but also transparent spaces on the table to let more light through. These tables, by construction, generate less power since there are fewer photovoltaic cells per square meter. However, the price of these tables is relatively higher than for conventional tables, so there is a compromise between agricultural production and energy production by the panels.

 

Agricultural robots under PV panels?

Since the environments under the panels are very structured and controlled, could we envisage having agricultural robots working under the panels (for example, weeding robots)? The fact that an infrastructure already exists could even be an asset for moving robots (on rails). Fences around PV installations could be an opportunity to use robotic machines in a safe way, and not be constrained by the Machinery Directive (which requires an operator to be present on site to ensure that the robot does nothing).

If we also consider the issue of energy autonomy of robots, the fact that these robotic units operate under photovoltaic panels, i.e., with a potential source of renewable energy at their disposal, could make it possible to move towards a reduction of dependence on fuels. But this is a matter of the future.

Risks and constraints of agrivoltaics

Agrivoltaism is still in the experimental stage. Therefore, real performance, especially in the long run, cannot be fully guaranteed, even if the initial results are encouraging.

Therefore, the agrivoltaism practice is unavoidably debated in the agricultural sector. Some fear in particular that this system will be more profitable for solar energy production and less for agricultural crops. Installing an agrivoltaic plant is indeed quite complex and must take into account many aspects to be effective, including the layout of the solar panels, the…