Page 111 - Low Temperature Energy Systems with Applications of Renewable Energy

100 Low-Temperature Energy Systems with Applications of Renewable Energy

3.3 Heat pumps for heating buildings and public
premises

The specific nature of facilities such as theaters, movies, restaurants, exhibition cen-
ters, supermarkets, train stations, hotels, hospitals, etc. requires a significant amount
of ventilation air when rooms are filled with people. Given that warm air concentrates
at the top of large rooms, mixing this air with the lower cold air that surrounds people is
an important opportunity for energy savings, especially in auditoriums and supermar-
kets. Also, it is important to adjust the frequency of ventilation depending on the num-
ber of people filling the premises, given that an average person needs about 0.005 m 3
of fresh air per second.
Heat sources for heat pumps in the above-mentioned premises are ventilation emis-
sions that can be used for heating fresh air, and in some cases, for hot water supply, as
for example, in heating water for kitchens in restaurants. Of course, in summer there is
a need for air conditioning, so the heat pump can be used both as a refrigerating ma-
chine and as a way to obtain heating. The latter version is suitable for a small heat de-
mand (hot water in bathrooms, kitchens, etc.). In grocery supermarkets, heat from
refrigerator condensers can cover 50e70% of space heating demands, but in many
cases this heat is simply discharged to the environment, thereby necessitating addi-
tional consumption of heat energy from boilers and heating networks.
In hospitals, various areas should be categorized according to their functions and
then the corresponding temperature requirements should be specified. In order to facil-
itate operation, heat pumps should be designed and built with a power being sufficient
for centralized heat supply with well-isolated heat networks. The heat pump can simul-
taneously cool water needed for air conditioning, and heat water needed for sanitary
purposes in summer. A traditional boiler should be used as a peak source for winter
heating. In some cases, due to the varying functionality of rooms and their occupancy
with patients or visitors, local individual heat pumps should be used. With the intro-
duction of lower night rates for electricity, it makes sense to use cold and heat storage
units to cover peak loads and save money.

3.3.1 Ventilation systems
Among the most effective facilities for the application of heat pump technologies are
the ventilation systems of industrial, public and residential premises. Due to the small
difference in temperatures of the inflow and exhaust air, it is possible to attain high
energy efficiency using heat pumps in ventilation systems at moderate ambient temper-
atures. However, when the temperature of ambient air is lowered, the efficiency of sim-
ple heat pump ventilation circuits decreases significantly, which results in the use of
more complex circuits. In this regard, excellent results are achievable with heat
pump and recuperative ventilation systems, in which the final energy effect is deter-
mined by a combination of an exhaust air heat recovery unit and a heat pump.