Page 109 - Low Temperature Energy Systems with Applications of Renewable Energy

98 Low-Temperature Energy Systems with Applications of Renewable Energy

condenses at the evaporator. Dried air from the evaporator, equipped with a condensate
collector, returns to the condenser of the HP. When installing a thermosiphon unit, the
evaporator is in the air direction in front of the HP evaporator, and the condenser is in
front of the HP. The amount of heat generated in a HP condenser installed to reduce the
humidity of the pool air is greater than the amount required to heat the dried air. There-
fore, excess heat can be used to heat the water in the pool.
In addition, one should note that a rule requiring 5% daily water changing at 25 C

makes it logical to use the heat of this water in a heat pump (before the water is
drained) to heat the replacement water. Retrofitting heat pumps in existing pools
can achieve a 2e3 year payback period for the capital investment; for new pools,
the payback is rapid, only 3e6 months. To maintain air parameters in pools regulated
by sanitary standards, it is necessary to perform the following actions: remove a sig-
nificant amount of water vapor formed as a result of evaporation from the surface of
the pool and as a result of respiration of swimmers and spectators; compensate for
heat effects through enclosing structures, i.e., heat losses in winter and heat gain in
summer; maintain the composition of air as regulated by sanitary standards, especially
in the presence of a large number of people in the swimming pool area.
All these measures require high power costs considering that in winter with venti-
lated air being emitted into the atmosphere, a huge amount of low-temperature heat is
lost and a large amount of energy is consumed for heating inflow air. Figure 3.13 il-
lustrates the concept of a system of heat recovery from discharged ventilation air by
means of heat exchangers and an “air-to-air” heat pump.
In this basic arrangement during winter, it is necessary to supply only 8.5% of the
required amount of energy from an external source. About 38% of the total amount of
heat is returned by the heat exchanger, 13% by means of the heat pump, and 32% due
to recirculation. In summer, the built-in heat pump allows air in the pool to be dried
under any weather conditions. The system has regulation, manually adjusted for a
given mode of operation (swimmer training, sports competitions, classes with fitness
groups, etc.) and automatically adjusts depending on external weather conditions. The
long-term operation of the system has shown its energy efficiency is characterized by
an 8-fold reduction in peak thermal load. The introduction of the system has removed a
cause of corrosion of metal and concrete building structures. The payback period of the
system was 18 months. Such experience can be used in systems of heat utilization of
discharged ventilation flows of movie and concert halls, sports complexes, industrial
enterprises, and buildings in farming and industrial complexes.

3.2.2 Outdoor pools
The heating of water in outdoor pools from an energy point of view is feasible only at

an ambient temperature of 10e12 S. In other colder periods heat consumption is too
large. Heat is used to compensate for heat losses and daily heating of the 5% of water

that is changed. The water temperature should be higher than 20 C and lower than
23 C. The water temperature in the shower used by swimmers leaving the pool should