Renewable Energy – Solutions for application in the communal energy infrastructure

SOLAR THERMAL ENERGY |
13
5
1
Design of a solar
thermal system
in a building
2 3 4
1) Solar collector
2) Solar storage tank
3) Boiler
4) Solar controller
with expansion
vessel
5) Consumer
Possible applications and benefits for municipalities:
Solar thermal systems convert solar radiation directly
into heat, thus saving costs and reducing CO 2 emissions.
They can be used for:
• Single and multi-family houses,
apartment buildings
• Municipal buildings such as kindergartens,
retirement and residential homes
• Tourist buildings such as guesthouses and hotels
• Industrial and commercial processes
• Local and district heating networks
Functional principle and design
At the heart of a solar thermal system are solar collectors
containing absorbers made of copper or aluminium.
These absorbers take in energy-rich short-wave
solar radiation and convert it into usable heat. The heat
is then transferred to a heat transfer medium. This is
usually a frost-proof solar fluid that circulates within
the system. A circulation pump transports the heat
from the collectors through the solar pipes and to the
heat storage tank. Due to the fact that the solar fluid
is in a separate circuit, a heat exchanger transfers the
heat to the domestic or heating water. From the storage
tank, the heat then reaches the hot water distribution
or the heating system.
Robustly built flat-plate collectors are available, which
have the largest market share, as well as more powerful
evacuated tube collectors. Air collectors, a niche product,
can be used for additional ventilation.
In domestic hot water systems, a drinking water storage
tank stores hot water for bathing and washing. In
heating-support systems, either a buffer storage tank
is used that only stores the heating water, or a combination
storage tank where a drinking water storage
tank is integrated into the heating tank.
In the case of a domestic hot water system, it is advisable
to dimension the system in such a way that
the demand for heat in summer is completely covered
by solar energy. The boiler can then remain switched
off during the warmer months and, depending on the
design, in spring and autumn, too.
Heating-support systems must also be scaled proportionately
in accordance with the share of solar heat
to total heating energy. The collectors are aligned in
such a way that they absorb as much solar radiation as
possible during winter. The space required for the heat
storage tank, which is usually installed in the heating
or engineering room, must also be taken into account.