Austrian heat supplier Energiecomfort is expanding its solar heat services: The company based in Vienna, the capital of Austria, services around 5,000 m² of collector area for 50 different multi-family building projects across the Vienna area. Over the coming weeks, a 1,500 m² collector field for the newly built residential district Waldmühle Rodaun will go into operation, for which Energiecomfort will act as an Energy Service Company to provide the entire heat supply for the around 445 flats built on the grounds of a former cement factory on the outskirts of Vienna. The residents are planned to move in next year, but the solar heat will already be used for screed drying and heating during construction in the coming winter season.
Photo: Waldmühle Rodaun Betreuungsgesellschaft mbH
“Our core business is the construction and operation of heating plants for the residential sector,” Christoph Gerstbauer, Sales and Product Manager of Energiecomfort, describes the work of the subsidiary of local utility Wien Energie. “Since the municipality of Vienna stipulates high-efficiency heat supply systems for all newbuilds and since 2012, for existing buildings regarding 25 % renovation, we install a lot of gas boilers including solar thermal in multi-family buildings.”
In half of the projects, the builders own the solar collector field because they want to receive the building construction subsidies coupled to the installation of a renewable heating system. The other half of the projects is operated entirely by Energiecomfort, which sells the energy to the residents. “The latter is our favoured model because annual energy settlement with end consumers is easier when we run both the fossil fuel boilers and the solar plants,” Gerstbauer explains.
Heat pumps receive heat from a solar storage tank
This is also the case regarding the new residential district Waldmühle Rodaun. Energiecomfort was commissioned by Austrian building developer Waldmühle Rodaun Errichtungsgesellschaft to design the complete hot water and space heating supply for the residential area. Since district heating was not an option for the area up on the hill on the outskirts of Vienna, Energiecomfort designed three heating stations, each of them equipped with a heat pump providing heat at 62 °C for the buildings’ micro-grid. The heat pumps receive their heat from a 55 m3 storage with a maximum temperature of 35 °C. Based on the temperature, the 1,500 m² solar field installed on the roofs of the multi-family buildings feeds its energy either into the heat pump storage tank (max. 35 °C) or into the buffer tank of the micro-grid at minimum 62 °C. Energiecomfort plans to add gas boilers as backup when solar will not be able to cover all needs of the heat pump storage. The heat specialists successfully applied for the large-scale solar plant subsidy scheme by the Austrian Climate and Energy Fund. “Only this 40 % subsidy for solar thermal installation costs has made it possible to offer the solar heat at prices competitive with gas,” Gerstbauer says.
Simulation of the planned share of solar, heat pump and gas boiler in the total heating and hot water demand of 2,444 MWh/a for the Waldmühle Rodaun quarter
Energiecomfort invited tenders for installing the 1,500 m² collector field on the roof of the multi-family buildings, and turnkey system supplier S.O.L.I.D. from Austria was the company that won. It installed a field on already existing cement blocks provided by the builder. “Solar yield is important to us, which is why we requested a specific power per m² of collector field aperture area in the tender,” the sales and product manager points out. Energiecomfort has planned irradiation sensors on the roofs to measure the efficiency of the field under real-life conditions.