CHP Project of the Month: Cultural Center in Alzey, Germany

Geothermal energy, photovoltaics, storage facilities, and a cogeneration plant supply the Alzey Cultural Center. The project was implemented using a contracting model with a shared investment structure.

A troublesome natural gas heating system was the starting point for a fundamental modernization of the energy supply at the Alzey Cultural Center. The building is located in the jurisdiction of the district administration of the Alzey-Worms district in Rheinhessen. The "EnergieDienstleistungsGesellschaft Rheinhessen-Nahe" (EDG) implemented an energy concept based on near-surface geothermal energy in conjunction with an innovative combined heat and power plant and a photovoltaic system.

"We proposed this system as a contracting service provider because the listed building is supplied with classic radiator heating and, in cold weather, higher flow temperatures are required, which would otherwise negatively impact the efficiency of the geothermal heat pumps," explains EDG Managing Director Christoph Zeis in an interview with Energie & Management.

Zeis explains: "After the contract was awarded and signed in the summer of 2024, planning could begin. In the second half of the year, the water law permit for the geothermal energy plant was granted." Construction work began in May 2025, and the plant has been in operation since the 2025/2026 heating season.


System concept with geothermal energy, CHP and storage

Before modernization, the listed Alzey Cultural Center had a 34-year-old natural gas heating system with an output of 190 kW. EDG replaced this with a combination of systems including geothermal energy, CHP, photovoltaics, and storage. A combined heat and power plant (CHP) with an electrical output of 20 kW and a thermal output of 44 kW, including condensing boiler technology. The CHP plant is supplemented by two brine-water heat pumps, each with a heat output of 31.6 kW. The heat source for the heat pumps is a geothermal field that was constructed with ten geothermal boreholes, each 100 meters deep.

EDG pursued the goal of achieving the highest possible level of self-sufficiency for the cultural center. To this end, the contracting service provider also installed a photovoltaic system with a capacity of 29.4 kW on the roof of the building and a battery storage system with a capacity of 16 kWh.
 

Electricity and heat generation in interaction

The Alzey Cultural Center has a heat demand of around 135,000 kWh per year. Of this, the CHP plant is expected to provide around 65 percent — primarily during the heating season. The remaining 35 percent is generated by heat pumps, which also meet peak heat demand via power-to-heat using hot gas extraction. The necessary flexibility is achieved via heat storage tanks with a volume of 6,000 liters.

In terms of electricity requirements, EDG expects annual consumption to be around 50,000 kWh. The plan is to generate around 95 percent of this from decentralized in-house production on site. In this energy concept, the CHP plant covers energy concept, with only around 2,000 full utilization hours, primarily covers the electricity demand during the heating period between October and March, when photovoltaics are naturally only available to a limited extent.

"In the transition periods and in summer, the PV system takes over the job when the CHP plant is not needed," says Christoph Zeis.

The CHP plant generates around 40,000 kWh of electricity per year, with the photovoltaic system adding a further 30,000 kWh. Since the grid consumption is around 2,500 kWh per year, EDG plans to feed in around 22,500 kWh per year, which will be recorded separately according to the KWKG and EEG electricity in accordance with the relevant metering concept.

Flexible driving and network perspective

The special feature of the energy supply lies in the operating mode. The CHP plant is electrically superimposed, and the buffer storage tank has also been dimensioned to be large. This allows the CHP heat generation to be decoupled from the current heat demand, so that the CHP share of 65 percent can be achieved.

Zeis also sees this as having a beneficial effect on the grid: "On the electricity side, we see this mode of operation in the solar-deficient autumn and winter months as contributing to the relief of the distribution grids, to which heat pumps and charging points for e-mobility are increasingly having to be connected." Zeis also highlights the integration of geothermal energy: "We have implemented the cogeneration system with heat pumps based on geothermal energy. This environmental heat source requires significantly more investment than outside air, but enables higher annual performance factors and thus energy efficiency."

In addition, the system ensures passive cooling of the building, which is linked to the regeneration of the soil during the summer months. "Parallel to the construction of the modern CHP plant, we have implemented energy-saving measures in the heat distribution system and equipped all heating circuits with high-efficiency pumps," adds Zeis. The efficient generation and distribution ensemble also includes an EDG energy management system for remote control, remote monitoring, and continuous optimization of all processes along the heat and power demand chain.

Contracting agreement and subsidies

According to EDG, another special feature of the project is the contracting model chosen. The investment share of the heat pump system, including the geothermal field, was provided by the district of Alzey-Worms as the building owner through subsidies from Rhineland-Palatinate's “KIPKI program” (Municipal Investment Program for Climate Protection and Innovation).

"EDG covered the investment share of the CHP segment with CHP units and all accessories, as well as the construction of the PV system including battery storage, so that very economical heat and electricity prices could be achieved,“ Zeis is pleased to report.” Like all our contracts, the contracting agreement, like all our agreements, includes complete maintenance and servicing of the systems, including remote control, remote monitoring, and troubleshooting."

The primary energy factor of the system is 0.36. In conjunction with the photovoltaic system, the cultural center achieves climate neutrality in its balance sheet. The annual CO2 savings amount to around 53 tons. The Mainz-Bingen district in the east of Rhineland-Palatinate founded EDG in 1998. Today, the contracting service provider has 16 municipal shareholders, including the neighboring district of Alzey-Worms, and is responsible for ensuring that the energy supply for all buildings remains secure, affordable, and sustainable in the future.

Article by Heidi Roider
Picture: Landkreis Alzey-Worms Rheinhassen