Current developments in solar park expansion in Hesse – including the mega solar park project in Büttelborn – Creative image: Xpert.Digital
Hesse is pushing ahead with the expansion of solar energy at record speed
Photovoltaics expansion in Hesse doubles: What's behind it?
The expansion of photovoltaics in Hesse is progressing at an impressive pace. At the end of 2023, the state had 3,728.5 megawatts of installed PV capacity distributed across 240,146 systems. With 680 MW of newly installed capacity in 2023 – almost twice as much as the previous year – solar energy is becoming the driving force behind Hesse's energy transition. This report highlights some of the most significant current developments and challenges in the field of solar energy in Hesse.
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Büttelborn: Groundbreaking mega solar park project approved
The local council in Büttelborn (district of Groß-Gerau) has unanimously approved the construction of an ambitious solar park. The project stands out due to its impressive dimensions: A photovoltaic system with a peak output of 70 megawatts is planned for a 48-hectare site in the Worfelden district. This scale makes the park one of the most significant in southern Hesse.
The plant is designed to theoretically supply enough electricity for all approximately 23,300 households, as well as all buildings and facilities of the municipal administration. In fact, it generates one and a half times the amount of electricity needed for the entire town of Büttelborn, as Mayor Marcus Merkel (SPD) emphasizes. This overproduction allows the municipality to feed surplus electricity into the regional grid.
The technical implementation involves laying a six-kilometer-long underground cable to Darmstadt-Arheilgen to connect the solar park to the power grid. Following approval from the Darmstadt Regional Council in December 2023, the municipality now plans to quickly obtain the necessary building permits. The goal is ambitious: the photovoltaic park is expected to feed its first kilowatt-hours of electricity into the grid as early as the beginning or middle of 2026 – according to Mayor Merkel, this would be a “record time”.
Citizen participation as a key element
A key element of the Büttelborn project is the planned citizen participation. The involvement of the local population will be facilitated through a citizen energy cooperative, which will enable residents to financially benefit from the solar park and cover their own electricity needs. The Starkenburg eG energy cooperative will play a key role in this local citizen participation process.
This form of participatory energy transition aims to increase public acceptance of the project while simultaneously maximizing local consumption of the electricity generated on-site. Mayor Merkel emphasizes: “The goal is to consume as much of the locally generated solar power as possible on-site.”
Ecological and economic importance
With an annual production of around 70 million kilowatt-hours of electricity, the Büttelborn solar park will become a key component of the regional energy transition. The plant will contribute to an annual reduction in CO2 emissions of approximately 35,000 tons, thus significantly advancing Büttelborn towards climate neutrality. This saving is equivalent to the annual CO2 emissions of more than 20,000 average passenger cars.
With its virtually climate-neutral electricity supply, Büttelborn is positioning itself as a pioneer in municipal energy transition in southern Hesse. The project demonstrates how municipalities can not only assume ecological responsibility through strategic investments in renewable energies, but also secure predictable and stable energy costs for their budgets in the long term.
Schwalm-Knüll Energy Cooperative: Successful citizen participation in solar projects
Since its founding in 2011, the Schwalm-Knüll eG energy cooperative has established itself as a key player in the energy transition in Northern Hesse. With around 500 members, it focuses on the principle of local value creation through renewable energies. One success story is the MunDepot Allendorf solar park, which has been feeding solar power into the public grid since March 2024.
Allendorf Ammunition Depot: Modern solar concept with biodiversity
The MunDepot Allendorf solar park has a total capacity of 2,154 kWp, which produces enough electricity to theoretically power 600 households. The plant saves approximately 1,035 tons of CO2 annually, thus making a significant contribution to climate protection in the region. The integrated biodiversity concept is particularly noteworthy: the area is grazed by a shepherd with 25 sheep, which supports the ecological enhancement of the site.
The choice of a site on a former special-use area – the former munitions depot – demonstrates how beneficial the repurposing of previously contaminated land for solar parks can be. “We need to put our heads together and openly discuss what is possible,” explains Horst Kaisinger, board member of the Schwalm-Knüll energy cooperative. Cooperation with the town of Schwalmstadt, the landowner, enabled the solar park to be built while adhering to biodiversity standards.
Local value creation through energy cooperatives
Over the past ten years, the Schwalm-Knüll energy cooperative has generated approximately seven million euros in direct added value for the region. These economic benefits are realized locally through dividend payments, interest, leases, and business taxes. This model demonstrates how renewable energies are not only ecologically sound but can also contribute economically to strengthening rural areas.
The cooperative is already planning further projects, including a cooperation with the city of Schwarzenborn and the Kassel municipal utilities to build an energy park with wind turbines and possibly another photovoltaic open-field plant.
Security risks at solar parks: Theft in Malsfeld
Alongside the positive developments, there are also challenges in securing solar parks. A recent example is the theft of copper cables from a solar park in Malsfeld-Ostheim (Schwalm-Eder district).
During the night of November 11-12, 2024, unknown perpetrators forcibly entered a solar park on Rotdornstraße in Malsfeld-Ostheim. They cut and stole approximately 1,000 meters of installed copper cable with an estimated total value of €40,000. The damage caused by the forced removal of the cables could not initially be quantified. The report was filed with the Melsungen police station on November 22, 2024.
This incident is not an isolated case: In a similar incident in December 2024, unknown individuals stole copper cables and inverters worth approximately €50,000 from a solar park in Gudensberg (also in the Schwalm-Eder district). The perpetrators scaled the fence, cut several hundred meters of power cable, and dismantled some inverters.
These incidents highlight the growing problem of solar park security. The valuable materials and components make these facilities attractive targets for theft. Operators should therefore invest more heavily in security measures such as surveillance systems, improved fencing, and regular inspections to protect their installations.
Opel's "grEEn-campus": Company location with sustainable energy supply
The automotive group Stellantis, which also owns the Opel brand, is pushing ahead with an ambitious future project at its Rüsselsheim site: the “grEEn-campus”. This is intended to serve as the heart of the future Stellantis Germany and global Opel headquarters, with a consistent focus on sustainability.
Comprehensive use of solar energy
A key element of the “grEEn-campus” is the planned photovoltaic system with approximately 7,000 panels to be installed on the roofs. These are intended to cover the entire electricity demand of the office buildings. This renewable energy generation will allow the complex to operate in a carbon-neutral manner, without the use of fossil fuels.
The project is part of a larger initiative: Stellantis and Prosolia Energy have signed an agreement for the development, construction, operation, and maintenance of a total of eight new photovoltaic plants in Germany and France. Three of the photovoltaic projects are planned for Germany – at the Stellantis plants in Kaiserslautern, Rüsselsheim, and Bochum – with a combined capacity of ten megawatts.
Holistic sustainability concept
The “grEEn-campus” goes beyond simply using solar energy and incorporates further sustainability components. Building climate control is achieved through efficient heat pump technology; rainwater is used to irrigate the green spaces, thus reducing water consumption. The greening of building components also contributes to increasing biodiversity.
The groundbreaking ceremony for the “grEEn-campus” is planned for this year. The project underscores the company's commitment to Opel as a German brand and is intended to make a significant contribution to Stellantis' goal of becoming CO2-neutral by 2038.
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Photovoltaic expansion in Hesse: Trends and political framework
The expansion of photovoltaics in Hesse is experiencing a remarkable upswing. In 2023, photovoltaic systems with a total capacity of 680 megawatts were installed, a significant increase compared to the 398 MW of the previous year. Preliminary figures for the first half of 2024 suggest another record increase for 2024 (358 MW).
Political framework and funding measures
The Hessian state government has taken various measures to promote the expansion of solar energy. On November 16, 2022, the Hessian state parliament passed an amendment to the energy law, which stipulates, among other things, that photovoltaic systems must be installed on new parking lots with more than 50 parking spaces, as well as on state-owned buildings.
An important tool for promoting ground-mounted solar installations is the newly launched Hessian solar cadastre, which has been expanded to include open spaces. With just a few clicks, it allows users to calculate solar energy potential, for example on their own roof, and has been rated as the most successful free information and planning service of its kind, with over 330,000 users since the end of 2016.
New regulations for designating solar areas will apply in Hesse following the implementation of the federal government's solar package on May 15, 2024. Accordingly, agriculturally disadvantaged areas throughout Germany are now eligible for subsidies for ground-mounted photovoltaic (PV) systems under the Renewable Energy Sources Act (EEG). In Hesse, approximately 530,000 hectares of agricultural land are therefore considered disadvantaged, representing about 60% of the state's arable and grassland.
Open-field facilities in focus: Biodiversity instead of monoculture
Despite the boom in solar energy, challenges and controversies remain, particularly regarding ground-mounted solar installations. The construction of solar parks on agricultural land is a subject of heated debate. Critics among farmers and environmental organizations warn of an irreparable loss of agricultural land. For example, the German Federation for the Environment and Nature Conservation (BUND) in Brandenburg argues that arable land should primarily be used for food and feed production.
To address these concerns, the German Nature and Biodiversity Conservation Union (NABU) and the German Solar Association (BSW) have jointly developed criteria for environmentally compatible ground-mounted photovoltaic systems. These criteria stipulate that ground-mounted PV systems can enable a combination of nature and climate protection through the extensification of land use. A significant improvement in biodiversity is particularly achievable if the land was previously used for conventional agriculture.
The future of solar energy in Hesse
The projects and developments presented demonstrate that Hesse is well on its way to advancing the energy transition through the massive expansion of solar energy. With a share of 28.1 percent of gross electricity consumption, renewable energies are playing an increasingly important role in Hesse's energy supply.
The success of the energy transition depends not only on technical and economic factors, but also on public acceptance. The examples presented show that citizen participation through energy cooperatives can be a key element for the successful implementation of solar projects. At the same time, security aspects must be given greater consideration to protect installations from theft and vandalism.
Integrating biodiversity concepts and carefully selecting suitable sites – preferably previously impacted areas or less agriculturally valuable regions – can help minimize conflicts between energy production, agriculture, and nature conservation. With this balanced approach, Hesse can contribute to the national energy transition while simultaneously promoting local economic development and environmental protection.
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