Hot water is a substantial part of the building services and a significant energy consumer.
When using hot water in the kitchen and the baths of the tagungswerk guest house in Berlin not only water through the direct consumption of groundwater (Berliner tap water) is consumed but also a significant amount is spent on energy. This takes place in the tagungswerk as throughout the whole KuBiZ project primarily through the use of gas. But electricity is used as well – mainly for pumps that get run on the water circuits. In order to circulate the hot 60° hot water in the house, we use a relatively small so-called “high-efficiency pump” from the best energy efficiency class (A). Even with the use of gas and electricity we create a (indirect) water footprint.
To make the hot water throughout the house as efficient and environmentally friendly as possible, we decided during the reconstruction and renovation of the building to separate the heating and hot water supply. This allows in the summer months, to turn the large boiler (400 litre boiler capacity) completely off and to produce hot water only with a small gas heater. Here we save a lot energy by reducing the amount of process heat. In addition, we have installed a solar heating system with a size of 36.5 m² collector area on the south roof. Using this system, we can make solar energy for water heating available. Last year we were able to use about 8.7 MWh solar energy.
On sunny days in spring and summer, we cover most of the energy required for hot water supply from solar energy. Nevertheless, our share of the water footprint of hot water usage is not small. In our overall water-footprint calculation of tagungswerk we used an estimate because an accurate calculation would have exceeded our capacity. The positive effects of the solar thermal system were taken into account.
In the context of the project “Water and Sustainability” and in order to use the best practice example of our solar hot water production in education and make it visible for our guests we installed an extension of the control electronics which now also allows to make the current values and the facility-scheme in Internet (on the website of tagungswerk and KuBiZ) visible. In addition a digital display board which provides information on the solar thermal yield at the main entrance, which is being renovated yet, will be installed after the work is finished. The preparations for this have already been taken from us.
Here is the result of our work.