Environmental Engineering Reference
In-Depth Information
Solar
absorber
Control
cool
Pump
warm
Figure 3.2
Principle of Solar Thermal Swimming Pool Heating
conditions or during the night, the pool water cools down in the absorber,
which now acts as a radiator. A simple two-step controller with hysteresis can
avoid this; if sensors detect that the temperature difference between pool and
absorber is above a certain threshold level, the pump is switched on.
A conventional auxiliary heating system can be integrated to ensure that
the desired pool temperature can always be achieved. If the pool is solar heated
only, the water temperature will fluctuate with the weather. During bad
weather periods, the water temperature is slightly lower; however, this is often
acceptable because the pool is not used so much under these conditions.
The typical
heat demand of outdoor swimming pools
in moderate climates
is between 150 kWh and 450 kWh per square metre of pool surface. A well-
designed solar heating system can maintain a base temperature of 23°C, and
thus a fossil heating system is not necessary. For a pool with a surface area of
2000 m
2
, a solar heating system can avoid the burning of 75,000 litres of fuel
oil and the production of 150,000 kg CO
2
(boiler efficiency 80 per cent) every
season. Covering the pool during the night can minimize the heat losses and
save additional energy.
As a rule of thumb, the
size of the solar absorber surface
should be 50-80
per cent of the pool surface; however, this depends significantly on the climate.
Experience from previous installations or computer simulations can provide
more exact values for the system designer. The absorber costs are of the order
€
100/m
2
. Usually the costs of solar heating systems are lower than the costs of
fossil fuel heating systems. Only if the outdoor swimming pool is to be
operated all year round or if the pool temperature has to be rather high would
an auxiliary fossil heating system reduce costs compared to solar energy
solutions alone.
Electricity is needed to run the pump of a solar swimming pool heating
system (see also Chapter 6, section on costs of a solar thermal system for
domestic water heating, p240); however, a small photovoltaic system could
generate this electricity. Then, the temperature control can be omitted in some
