How a Czech agricultural university explored combining electricity generation and crop growing

Researchers at the Czech University of Life Sciences Prague have been studying for two years how to combine electricity generation with crop cultivation. The results so far show that raspberries grown under agrivoltaics are identical to those grown without panels.

Few people would expect to find raspberry bushes growing beneath solar panels in the small atrium at the heart of the Czech University of Life Sciences Prague’s Faculty of Engineering pavilion. Yet this is where, between laboratories, classrooms and offices, an experimental agrivoltaic installation combining crop cultivation and electricity generation is hidden.

“Every grower needs to know how shading affects growth, fruit ripening or sugar content, as well as how the crop manages water – questions that need answers,” says Milan Kroulík, who is developing the research at the Faculty of Engineering. The results so far look promising, and the benefits are even mutual, as water evaporating from plants can improve the efficiency of photovoltaic panels.

For many people, it is difficult to imagine how electricity generation and crop cultivation can be combined in practice. What does your experimental installation here at the faculty look like?

We decided to install a photovoltaic power plant above raspberry bushes. We have our own structure, approximately three metres high. We use opaque panels with 50% shading, achieved by alternating panels and gaps so that light transmission matches the required ratio. We also have an unshaded control variant so that we can observe the differences.

Here at the university, we grow two varieties, Polka and Tulameen. In total, we have 30 raspberry bushes under the panels and 30 outside them, in three rows. We monitor how the photovoltaic installation affects their yields, fruit quality and the overall condition of the crop. So far, these shade-tolerant species – raspberries are commonly found in forests – appear to thrive under the panels.

How long have you been conducting this research?

At this point, we have completed two years of monitoring. The project will continue this year, but we certainly do not want to stop there. We plan to extend and further expand the research. In addition to raspberries, we are also considering planting and monitoring blueberries.

Farmers are concerned about how shading affects the fruit itself. What conclusions have you reached after two years of research?

Every grower needs to know how shading affects growth, fruit ripening or sugar content, as well as how the crop manages water – questions that need answers. That is why one of the main objectives of our project is to monitor the impact of agrivoltaics on plant health and fruit yields. We regularly collect fruit and monitor its quality. We record its size and weight, as well as the levels of various substances, vitamins and acids. We also monitor the condition of the bushes, how they grow, transpiration (the release of water through the plant’s surface, editor’s note) and photosynthetic activity.

The results to date show that for raspberries, we have not recorded any significant differences in yield or fruit quality between the shaded and unshaded areas. The comparison shows that plants under the panels cope better with hot summer days. They use water more efficiently and generally perform better at higher temperatures than in a fully sun-exposed area.

However, we are also focusing on other factors. For example, we are examining how the plants affect electricity generation itself. Water evaporating from the plants cools the surrounding area, which can improve the efficiency of photovoltaic panels. In this case, the benefits are mutual.

What was this year’s raspberry harvest like?

We harvest very intensively and are satisfied with the quality. Last year, when the crop was in full production and the two-year-old Tulameen variety also began bearing fruit, we harvested 85 kilograms of very high-quality fruit. We even harvest every three days; otherwise, the raspberries start to spoil quickly. We are therefore looking into the possibility of robotic harvesting, as it is demanding to manage. Within the photovoltaic power plant, we already operate robotic mowers.

What do you do with the raspberries after harvesting?

We always subject part of the harvest to analysis, monitoring the content of individual substances. The rest is processed here at the faculty, which is not a problem. We are also considering further processing in the food technology pavilion and are experimenting with lyophilisation, or freeze-drying.

The electricity generated could also be used for that. What is the capacity of your power plant?

It is a smaller installation with a maximum capacity of around five kilowatts. During the warm months, we use surplus energy to power pumps and irrigation. In future, we could consider, for example, a cold-storage unit for fruit, although for now we have no problem consuming the raspberries immediately.

Agrivoltaics could also protect fruit from heavy rain and hail. Have you encountered anything like this?

Fortunately, we have not experienced such a situation here yet. But we can already see that shading helps plants tolerate summer heat better and reduces the risk of leaves being scorched by sunlight.

The potential for protection is particularly important in orchards. Structures there tend to be significantly taller than those in smaller plantings, to allow sufficient room for tree growth and the installation of protective nets. The question remains whether panels could fully replace anti-hail nets, as they do not yet cover the area as effectively. For example, hail could penetrate from the sides.

Can agrivoltaics protect against temperature fluctuations?

In a smaller planting such as this one, the impact of photovoltaic panels on the microclimate is limited, particularly because of its location in a courtyard. For larger areas, a protective effect can be expected, for example against spring frosts. However, we cannot determine this from our current research.

How do panels affect biodiversity?

For example, we have found that raspberry bushes are very attractive to bees. In general, these shrubs flower throughout the season, providing them with a continuous food source, which attracts a considerable number of pollinators.

Biodiversity needs further research, but it appears that photovoltaic panels, particularly in fields, could help increase it. The species composition of animals may change. In spring, the microclimate beneath panels warms up more quickly, which may encourage the earlier appearance of some species, while in summer overheating may lead others to migrate. Overall impacts so far appear rather positive, including in terms of enhancing biodiversity.

Does agrivoltaics also affect water retention in the landscape?

Vegetated strips in the areas around panels could play a role. The effect will depend on the orientation and type of installation. For example, vertical panels can help interrupt runoff paths, while with horizontal installations we monitor the impact on drip erosion and soil washout. Water management is important in practice; for example, installing gutter systems could significantly increase the cost of the structure. Concentrated water runoff from panels needs to be addressed, and ways must be found to allow it to infiltrate the ground.

What other crops besides raspberries are suitable for combined electricity generation?

Our choice of crops is limited by an implementing decree that restricts the installation of power plants above permanent crops. Within these areas, installations can be envisaged in most cases. The first ones are already being built. These include orchards and vineyards, as well as the aforementioned types of soft fruit. Hop gardens, nurseries and areas with shade-tolerant species are also suitable.

You regularly speak at agricultural conferences and other events. Do you see interest in this topic among growers?

The discussion is very lively and is frequently raised. Interest in agrivoltaics is evident.

What does this innovation offer Czech farmers and fruit growers from an economic perspective?

It is positive that renewable energy sources can also be used on agricultural land in a way that efficiently combines cultivation with electricity generation. Agrivoltaics could open up new opportunities especially for fruit growers facing economic challenges, for example by combining energy production for their own use in cold stores and dryers, or by operating robotic and autonomous systems. Further development will show what specific benefits this technology can bring in practice.

Installing agrivoltaics is substantially more expensive than conventional ground-mounted or rooftop photovoltaics. Is it worth farmers investing in it?

It is very complicated. The economics of agrivoltaics are complex and depend on many factors, including upfront investment, subsidy options, use of the electricity generated and the profitability of the agricultural production itself. The return on investment may not always be straightforward, especially for installations on agricultural land, where projects are still largely at the pilot-farm stage. All these aspects and parameters must be assessed in the final project. The benefits will become clear in the future.

Agrivoltaics is already being tested on hectares of land in France. Do you also follow international research?

Certainly, this is also a newer and not yet fully explored topic abroad. We follow developments in other countries, but it is always necessary to take account of specific climatic conditions and solar irradiation potential. These are of course different in Italy or southern France than in Central Europe. Southern countries routinely face different temperatures and solar radiation intensity, where shading is desirable to prevent fruit damage. However, this will gradually also apply to Czechia with the advancing climate change and extreme weather events.

Will you continue working on this topic?

Certainly, we have already built up the facilities here at the faculty. Companies are interested in collaborating with us on development and research. We also want to explore further applications, for example in field robotics or autonomous systems for agriculture.

Cooperation with other growers is also taking shape. In addition to the smaller installation at our university in Suchdol, we are working with Školky Litomyšl. This spring, we plan to begin measurements at an installation at the Research and Breeding Institute of Pomology in Holovousy. It is not ours, but by agreement with the institute we can verify certain parameters beneath its panels.