The state capital of Baden-Württemberg is working on the urban energy turnaround and is aiming for climate neutrality by 2050. A design for the quarter emerged from the urban planning competition. The former Olga Hospital site will be used primarily for residential us as well as some commercial space, a daycare center and a retailer.
Transsolar was given the task of creating an energy concept. In addition to the aspects of building design, such as the quality of the envelope surfaces and technical equipment, a sustainable solution for the future energy supply had to be determined.
The goal was to use passive and active measures and as much renewable energy as possible to bring the primary energy demand of the settlement to the level of passive houses (120 kWh/(m²*a). The measures required to achieve this were investigated and evaluated with regard to the resulting CO₂ emissions and local renewable energy generation. Several scenarios were developed for the heat supply. The planning team prepared a cost estimate in terms of investment and operating costs in order to evaluate the individual scenarios of the energy concept economically as well.
In addition, the study evaluated the design in terms of shading or sunlight on the facades and roofs. For the different supply scenarios, the area required for solar use was determined and compared with the existing areas.
Two solutions were considered for the energy supply: thermal solar energy and connection to the district heating available on site - or a combined heat and power plant (CHP) with a gas peak boiler system; both variants with installation of sufficient photovoltaic surface on the roofs of the four building sites. After considering all the constraints, the installation of a CHP unit for the simultaneous generation of heat and electricity was recommended.
The energy concept approved by the municipal council for the site with 224 apartments now provides for a local heating network for all four construction sites. Heat and electricity will be generated in a new CHP unit and used in the new neighborhood. A 900-kilowatt condensing boiler covers peak loads. A photovoltaic system will supply electricity from the building roofs with an area of 1,700 m² and an electrical output of 280 kWp. The heating center and PV system are operated by Stadtwerke Stuttgart, which sells heat to tenants and apartment owners and offers the locally generated electricity at favorable conditions.