„We chose the Veolia Water Technologies plant because it is a stationary plant that continuously treats the water. From other suppliers, we had offers for mobile plants that we would only have used for several months.“
Hartmut Langlitz
Chairman of the Supervisory Board of Energiedorf Bergheim eG
| The client
Ortenberg-Bergheim, a small town with a population of 650 in the Wetterau region of Hesse: In 2008, the plan to build a local district heating network to supply the town centrally with heat and hot water was born here. At that time, sewer and civil engineering work was pending. What could be more obvious than to lay a heating network at the same time? On the initiative of committed residents, the energy cooperative "Energiedorf Bergheim eG" was founded.
In the meantime, about 130 houses with about 170 households are connected to the local heating network. In addition, all public facilities are also supplied: the sports center, the church, the fire department, the kindergarten and the village community center. Each year, the cooperative produces 3500 MWh of heat - not only cheaply, but above all sustainably.
Heat generation is based on a three-stage system:
Woodchip combustion
The heating water is primarily heated with wood chips as an energy source, a renewable raw material that is more than sufficiently available in the densely forested region. Even wood that has been attacked by bark beetles and is therefore of inferior quality can be used here.
Solar thermal system
A solar thermal system serves as the second component. With a collector area of 1,300 square meters, solar collectors with a total capacity of one megawatt generate the hot water in the summer months. This means that during this time, the boilers for burning the wood chips remain cold. As a result, only 80 percent of heat generation is accounted for by the wood chips, and 20 percent by solar thermal energy.
The concept is rounded off by additional hot water tanks to cushion the morning peak load in the winter months and to bridge days with little sunshine in the summer. The electricity for operating the pumps and other electrical consumers comes from the company's own photovoltaic systems, which are installed directly on the roof of the heating center and also the neighboring village community center.
Redundancy boiler
To ensure security of supply, a redundant boiler is also installed to meet exceptional peak loads in particularly cold winters. Classically operated with heating oil, however, it only has to cover a few heating hours over the year. The oil-fired boiler is so large that it could theoretically heat the network on its own if the woodchip-fired boilers were to fail.
| The client's needs
For heat distribution, the Bergheimers use two water circuits: a primary circuit in the heating plant with 140 cubic meters of water and the actual local heating network with a capacity of about 65 cubic meters.
The standard values for the quality of the heating water are prescribed by the VDI 2035 standards and, for larger heating networks, by the corresponding AGFW FW 510 worksheet. In addition, the requirements of the boiler manufacturers apply, which reject recourse claims if the quality of the circuit water deviates from these. "That's why we have to treat it regularly. So far, we have had no problems in the network with water losses due to leaks. However, the conductivity was still too high at a value of over 100, which had to be lowered and the pH adjusted accordingly," explains Langlitz.
| The solution
For water treatment, a BerkeSELECT IQ+ system from Veolia was installed in the bypass of the heating circuit. The system continuously extracts water from the heating circuit, which is fed through filter bags. Depending on the requirements, softening, desalination, alkalization or filtration of the water and, in addition, degassing takes place in this way. Degassing of the heating water increases the efficiency of a system, as air-filled cavities in the system cannot occur at all. In addition, the water is thus also free of carbonic acid, which otherwise causes corrosion. At the same time, recirculated water treatment also ensures that the make-up water, which is used to keep the quantity of water in the network constant, is of the required quality.
| The result
Since commissioning, the conductivity value has fallen as planned and has now reached the target value. The water, which has been treated in accordance with standards, ensures that the local heating network can be operated efficiently and energy-savingly with optimum heat transfer on a permanent basis. Corrosion, scale or silting are prevented for long-term and trouble-free operation.
Simple maintenance
The treatment system is installed in the off-line flow. When the capacity of the filter bags is exhausted, the water is drained from the BerkeSELECT IQ+ and the filter bags can be easily changed. The system is then resealed and restarted. "Maintenance is relatively easy to perform; it takes less than a quarter of an hour," Langlitz says.
Pioneer of the energy turnaround
The local heating network of Energiedorf Bergheim eG is now regarded as a model for other "energy villages" as well. There are now more than 80 villages that have also set up their own networks with the support of state and federal funding. "The current energy crisis in particular shows that independent energy supply via local heating networks is a good alternative. We are independent of prices on the gas and oil markets. And once the heating system is paid off, we can go even lower with our heating prices," concludes Hartmut Langlitz. The socially responsible turnaround in heating has therefore long been in full swing in the Wetterau region.