How is a solar thermal system planned?

In order to be able to plan a solar thermal system, the hot water demand and, in the case of a supporting heating system, the heating demand must be determined. In principle, the size of a solar thermal system depends on the desired solar coverage, but the available space (roof, façade) and the statics set limits.

Another important parameter is the orientation of the system. Roof slopes between 20° and 60° are optimal for solar systems, with flatter roofs (between 20° and 30°) being more advantageous in summer and steeper roofs (50° to 60°) in winter. (Austria Solar)

As a guideline, a 4-person household for domestic water heating needs 1 to 1.5 m2 collector surface per person (4-6 m2) with a solar storage tank volume of 0.3 to 0.4 m3 (300-400 l) and an annual average coverage rate of 50 to 60 % (Lenz et al. 2010). For systems with additional heating support, 8 to 16 m2 are dimensioned, combined with a water storage tank of 1,000 litres.

For energy-efficient buildings, a collector surface of 10 to 20 m2 and a storage tank volume of 0.7 to 2.0m3 can cover 20 to 30 % of the total heat demand (Lenz et al.2010). Ideally, the total heat demand of passive-house quality EFH can be covered by solar energy. Essential for efficient operation is the quality of the components (collector, heat exchanger), the optimal design and combination of collector surface, storage tank (buffer storage, stratified storage tank), dimensioning of the pipe system.