Legislation to foment the use of renewable energies and solar thermal energy in building construction: The case of Spain - Solar Energy Sciences and Engineering Applications - page 654

needs during its design and dimensioning, installation, maintenance and use. This
regulation also establishes the certification procedure to verify this compliance 18 .
20.4 THE SOLAR THERMAL SYSTEM
Low-temperature thermal solar systems 19 use solar energy as a direct heat source for
thermal uses such as space heating, domestic hot water, swimming pool heating, etc.
These systems capture the sun's energy by means of solar collectors and store it so
that it can be used when needed (see Figure 20.3.2). For those periods when there is
not sufficient solar radiation and/or energy consumption is greater than expected, the
system can also include a supplementary back-up system that automatically switches
on and which uses more conventional energy sources such as gas, electricity or diesel
fuel.
Figure 20.4.3 shows the diagram of a solar installation for a multi-dwelling build-
ing with a central energy storage system and a back-up system with a boiler that runs
on a more conventional energy source. The installation consists of an array of solar
collectors that transform solar radiation directly into thermal energy, releasing it into
a working fluid. The collectors are arranged in rows, each with the same number of
elements (see Figure 20.4.2). The rows of collectors can be interconnected in paral-
lel, in series or a combination of the two (see Figure 20.4.1). Cut-off valves should
be installed at the entry and exit points of the rows of collectors and between the
pumps so that they can be used to isolate these components during maintenance and
repair work.
Figure 20.4.1 Connection between solar collectors: a) in series; b) in parallel and c) In series-parallel.
18 Reglamento de Instalaciones Térmicas en los Edificios . Article 1.
19 The energy from solar radiation is transformed into thermal energy by means of a heat col-
lection process. It is regarded as low temperature when the solar energy obtained is used for
temperatures lower than 80 ◦ C.