Technical data

SOLAR
THERMAL
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Steca Elektronik GmbH | 87700 Memmingen | Germany | Fon [phone] | Fax [phone] | www.stecasolar.com
S O L A R T H E R M A L
Solar thermal systems
Solar thermal systems convert incident solar
irradiation into heat so that it can be used
to heat domestic hot water or for additional
heating.
The solar irradiation is converted into heat in the
collector whose main component is a selectively-
coated absorber. The heat is pumped via a closed
piping system, the solar circuit, from the collector
to the storage tank. The solar system not only
provides hot water in the summer and in tran-
sitional periods, but can also even provide some
in winter. A frost-resistant mixture of water and
glycol is used to prevent the heat-transfer fluid
freezing in the solar circuit.
Temperature differential control
A temperature differential controller regulates the
transport of heat from the collector to the storage
tank. The controller always starts the circulation
pump of the solar circuit when the temperature
in the collector is several degrees warmer than the
temperature at the bottom of the storage tank.
This transports the solar fluid from the collector to
the lower heat exchanger, where the heat is trans-
ferred to the drinking water in the storage tank via
the solar circuit heat exchanger. The cooled solar
fluid then flows back to the collector in the return
pipes.
The heated drinking water rises in the storage tank.
The water is stratified in the storage tank according
to its density or temperature: The hottest water is
at the top (where it is drawn off), the coldest water
is at the bottom (where cold water is fed in).
With the current standard system size for one to
two family houses (approx. 1.0 to 1.5 m² collec-
tor surface per person and approx. 80-100 l sto-
rage tank volume), the drinking water in summer
is primarily heated by the solar system. This results
in an annual solar coverage (percentage of the to-
tal energy requirement for heating drinking water
provided by solar energy) of approx. 60 percent.
The remaining 40 percent must be covered by ad-
ditional heating. This is generally performed by a
solid fuel and the upper reheating heat exchanger
of the storage tank.
You can select a tailor-made controller from the
Steca solar thermal controller product family based
entirely on the requirements of your solar system.
A range of monitoring and control functions gua-
rantee that your solar system runs safely and maxi-
mise its service life.
A
D
C
B
E
Legend:
A Collector
B Solar Station
C Storage tank
D Central-heating boiler
E Usage of water
Temperature differential
controller
Storage tank
Temperature
sensor
Solar circuit
Pump
Collector
Temperature
sensor