Mobile heat transport: Alternative energy concept for Friedberg school complex
There are no agricultural biogas plants to which the school could be connected – as in Mering – in the immediate vicinity. As part of the extension of the Konradin Realschule school, where a small air heat pump and a photovoltaic system were planned for the new building currently under construction, the district's building department has again increased its efforts to find a more sensible, large solution for the whole school centre.
The bifa environmental institute in Augsburg, which had carried out studies on a regional Augsburg local heat network on behalf of the Ministry of the Environment, finally had a great idea: Mobile heat transport turns unused waste heat into heating energy for schools. A competent partner for a pilot project is available: the AVA waste recovery plant.
The idea sounds so simple: A kind of overseas container contains a latent heat storage unit. The storage medium used is sodium acetate, and water flows through an integrated heat exchanger. The container is charged with waste heat, in the same way as a battery is charged. This waste heat, possibly after it has been used to generate electricity, is otherwise simply blown out into the atmosphere. Suppliers can be large industrial plants, waste incineration plans or biogas plants without connected district heating system. Following a short transport distance, only a few manual steps are required to connect the container to a discharge station of the property to be heated and it transfers thermal heat to the building's own heating system for hours.
The patent originates from space flight and is already 25 years old. The function is based on the phase transition from solid to fluid and the energy absorbed or discharged. The system has already been in use in the described form for around two and a half years in the Ruhr region. District administrator Christian Knauer visited the facility last year with his administration and bifa employees and was convinced: "It works!". A primary school in Bottrop ("Innovation City") and the water in a swimming pool in Dortmund are already heated with mobile waste heat. There have not been any stoppages to date. It is only planned to use the system to cover the so-called base load of the building heating, i.e. it will always be used in combination with conventional heating, which provides the heating for the peak loads and ensures security of supply.
Wastes from the region will become energy for the region – a concept that Dirk Matthies, Managing Director of AVA GmbH in Augsburg, is also really enthusiastic about. "We are still a long way from recovering and using all our waste heat. If we place it in heat containers we are making a double contribution to climate protection: We use the waste heat of the AVA and reduce the use of fossil fuels." District administrator Christian Knauer also sees two economic benefits: "Firstly, new fields of business will be developed for the AVA, in which we as the local authority also have a shareholding, and secondly, we make our heating costs independent of oil and gas price changes and at a favourable price level."
The pilot project in the Friedberg school centre has been running since 7th January this year. In view of the implementation contract, the company LaTherm has made further large investments in the development and optimised the containers, which are now more like tanks. The district's technical teams and the AVA have worked together on the necessary controls since the middle of the previous year, in order to fill the containers optimally with heat, and to be able to empty them by the maximum possible amount.
In the meantime, after a few operating days, 2,100 kWh has already been transported with each delivery. If the containers produce their full output in the morning, then at approx. 0° C their own gas burners have a break. Two schools including the extensions, two sports halls and a swimming pool are only heated by the mobile heat. Since school began in the new year well over 50 % of the heat consumption of these buildings have been covered by waste heat. "During this short time, 5,000 m³ gas have already been saved and therefore 10,000 kg CO2 have been avoided", announced Markus Hertel of the bifa environmental institute. By comparison, transport by truck generates only two to five percent of this.
The progress of the project is being monitored attentively by the biogas farmers in the region. Especially because many older plants are located a long way from buildings and until now have not been able to use the waste heat. The intention is also for the concept to be pushed into the awareness of industrial companies, because each kilowatt hour of heat used sensibly saves twice: valuable raw materials – regardless of whether fossil or regenerative – do not have to be burned and no electricity is required for cooling systems.