The 'energy and future storage' stores heat from combined heat and power for the district heating network: When a lot of electricity is needed, the heat generated at the same time is stored – like in a thermos. If consumers need to heat, it will be returned. This replaces oil and gas in cold spells with renewable energies. The cylinder has a diameter of approx. 25m/ 82ft with approx. 40m/ 131ft height. The store receives a modern façade construction. The top floor will house a dining facility, which leads to a total height of about 55m/ 180ft utilizing elevators and circular staircase. The occupancy per floor is limited to a maximum of 200 people. The highlight of the bistro, which is open to the public, and the convention room is the 360 degree view over the Rhine and into the Neckar valley. So the question arises: "Which kind of façade combines the requirements for thermal protection in summer, good daylighting and unobstructed views?”
Transsolar had to achieve the following: Unobstructed view to the outside, sufficient daylight everywhere, and comfortable climate inside; always with regard to resources, users, costs and open for new, different, even unusual solutions. Simulations on computer models combined with location-based weather data were used to make this happen.
The 4.4m high, fully glazed façade of the upper floor is ideal for uninterrupted views. The problem, however, is the potential sun exposure. A solar control glazing, which absorbs the heat inputs alone, produces a strong discoloration of the light. A movable sunscreen effectively reduces the solar gains, but hinders the all-round view (analogy glacier glasses). A fixed horizontal sunshade can offer shade for the facade and allow the view (analogy sombrero). Which fixed sun protection meets the requirements of daylight, shading and view?
Solar Rose as a design tool: As the date for the design of the sunscreen, August 15 was chosen because the sun's position is decreasing, but the outside temperature is still high. That means on a sunny day, it could quickly get too warm. The limit of the maximum solar input per day was set at 1.5 kWh/m². This ensures that the summer heat insulation according to DIN 4108 is fulfilled and that even with full coverage it is still possible to achieve the desired thermal comfort with only radiant cooling. A solar rose (derived from a wind rose) shows the result of the simulation (Figure 2). Depending on the orientation, the necessary quotient between the depth of the overhang d and the height of the glass façade h can be read, which is necessary to reach the target value of the solar entries on the daily average.
From this, the depth of the "roof overhang" can be determined. For the glass façade with a height of 4.4m, a full shading with d/h=1 would require a projection of 4.4m – which leads to structural problems on the one hand and to the restriction of daylight in the depth of the room on the other hand. Translated into the analogy of a sombrero: It would be too big. The solution to the problem is a combination: horizontal solid sunscreen, above it 'roller blinds' that let in light as needed. This hybrid brings the analogy to the classic sombrero to and end: the now not quite large 'hat brim' is lowered featuring added 'blinds'.