Agrophotovoltaics – Existing Solution for New Problems

Whether in Chile, Germany or somewhere else in the world – bringing home the harvest after a long working day is a satisfying feeling. As the German folk song “Im Märzen der Bauer” (In March the farmer) says: “He ploughs and he harrows and sows all it seeds […] and when all is blooming it gives them delight”. Nowadays, it is not that easy like in the song from the 1920s. Farming is much more complex, expensive, and energy-intensive. In addition, there are conflicts related to the use of agricultural land. One approach is the interdisciplinary field of research “Agrophotovoltaics” that investigates how agricultural land can be used both for plants or farm animals and photovoltaic power generation.

The “double harvesting” of electricity and biomass from the same area is a desirable result. It was in 1981 already that our founder Prof. Adolf Goetzberger had the same idea. When he provided the basis for agrophotovoltaics (APV) with his idea of double land use, critics feared interferences in the landscape and land speculation with unforeseeable consequences (Source: Sonnenenergie (1981), Nr.3, S.19-22). Probably, the time was not yet ripe and therefore the concept disappeared for the next 30 years…

Land use conflicts and economic pressure for agriculture

Since then, general conditions have changed. Land use conflicts about energy generation and food production are gaining an increasing amount of ground in public discussion (“food versus fuel” debate). Normally, an area cannot be used for both.

In Germany, a traditional greenfield photovoltaic plant is usually identified as “special area photovoltaic” in the land use plan. Such an area is being built by converting dormant industrial parks and unprofitable farmland in green area and building a photovoltaic plant on it. Afterwards, this area is no longer available for food production. Although the farmland that can be used for photovoltaic plants has been strongly reduced with the amendment of the German Renewable Energy Sources Act in 2010, it is foreseeable that profitable areas will be used again as soon as feed-in tariffs will be discarded due to cost reductions in photovoltaic plants.

This repurposing of farmland would cause disadvantages both for politics and the entire society. In general, it is not desirable to build photovoltaic plants on the most fertile soils. Thus, Germany will be more dependent on the food export from other countries than it already is.

On the other hand, there are farmers under pressure because of the changed conditions and the land use conflicts. Many small farmers have to quit, whereas large, energy-intensive farms come out on top. High performance farms are the key to staying competitive. In order to survive, many farmers prefer growing energy rather than agricultural crops. With regard to the land use, this has been an “either/or” decision so far.

Agrophotovoltaics – The idea of double harvesting

Now, let us consider the forgotten idea of Prof. Goetzberger from the 1980s (he must be a real forward thinker to develop solutions for future problems)…, and remember the farmer in the above mentioned German folk song who is delighted when all is blooming. He would be even more delighted if he could profit from “double harvesting” and does not have to give up neither his farmland nor agricultural subsidies and the energy self-supply.

The concept of APV offers a solution: At a height of three to five meters above the farmland, solar modules are installed on substructures. The area below this construction can still be used for agricultural cultivation, special crops (such as fruit and grapes) and livestock farming. The production of energy and food is possible at the same time. In future, this “mixed area” should be identified as “special area agrophotovoltaic” in the land use plan.

First findings

Besides the obvious benefit of dual land use, APV can help farmers to diversify their income structure and to become more stable. Land use is no longer an “either/or” decision but a “both…and”.

The shadowing of plants and animals caused by the construction is certainly not an unwanted compromise. Our research has shown that an optimal placement and orientation of the module (figure 1) will support some crops to have less light and temperature stress.

Also the orientation of the modules plays an important role in building the construction. The traditional southern orientation of the photovoltaic plant does not support the crop growth because the radiation on the ground is irregular (figure 2). An orientation south-east has led to better results (figure 3).

Potatoes, grapes, hops, spinach, salad and many other crops are particularly suitable for APV cultivation (figure 4).

Benefits for arid and off-grid regions

One important side effect of the shadowing is that less irrigation is needed. Especially arid regions with high solar radiation often provide ideal conditions for photovoltaic energy generation. In addition, farmers in these regions highly suffer from permanent water shortages.

This problem often occurs in combination with an inadequate electricity grid. Building these modules on farmland offers the additional advantage that farmers in off-grid regions can use the electricity for self-supply and do not have to rely on expensive and CO2-intensive diesel generators. Thus, the concept of APV allows for the conservation of resources in many ways.

Support for the project “AgroPV-Chile”

These factors also play a decisive role in the project “AgroPV-Chile” that is carried out in collaboration with the Fraunhofer Centro de Tecnologías para Energía Solar CSET Fraunhofer Centro de Tecnologías para Energía Solar CSET. Based on the first results of our  project »APV-RESOLA«, in which we as the project managers focused on the installation and operation of a test plant in Herdwangen near Lake Constance, we are working with other project partners as advisors in Chile.

Within the project “AgroPV Chile”, demonstration plants will be built in three different regions around the capital Santiago de Chile. The farms have been selected in collaboration with the project partner Fedfruta (Federación Gremial Nacional de Productores de Fruta). Questions like “Which crops does the farmer grow?”, “What is the energy used for?”, “Is the location properly protected against theft?”, “How can it be fed into the power circuit?” or “Is there a temporary storage?” were raised.

Aim of the project is to test the interaction of different arable crops and climatic regions. The APV research team from Fraunhofer ISE supports the Fraunhofer CSET with regard to construction preparation, communication with investors and the public as well as the development of substructures for the modules. At the end of the project term (15 months), a consultation with regard to the business model is planned.

It is particularly impressive how open-minded farmers have been to the project from the beginning. Both investors and participants are surprisingly enthusiastic although there are less resources available than in Germany.

Video: Visit at the farmers participating in the APV project in Chile…

Challenges and prospects

However, it must be mentioned that the plants in Germany have to withstand more complex demands than the demonstration plants in Chile. The required distance between the pillars of the substructure with more than 18 meters is already a major challenge. On the one hand, this space is necessary for agricultural machines to maneuver under the modules. On the other hand, it is a real challenge with regard to the static. In Chile, the plants do not need to be higher than three meters and not that wide because the machines are smaller, rarely used and many tasks are done manually. Another side effect in Germany: Due to the high material usage the plants are more expensive. Therefore, business models will play an important role in our work in the future.

Nevertheless, we believe that agrophotovoltaic will be more and more accepted in the future. If we are serious about the expansion of the energy system the development of photovoltaic plants will be essential. Given the stagnant cultivation of roof and open areas, APV presents an attractive alternative. Critics will certainly get accustomed to the redesigned landscape. And different does not always mean bad, it just means different.