There
can be some advantages gained by connecting Solar Thermal Collectors to Heat
Pump water heaters, but there are some important points to assess before this
combination can be recommended. The
first point to consider is the economics of the project. In other words will the addition of Solar
Thermal Panels provide sufficient reduction in traditional energy use, which can
then be calculated as a cost reduction when compared to the actual initial cost
of supplying and fitting the Solar Thermal Collector Panels?
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There is an unwritten expectation for energy
efficient products such as Solar Thermal and Heat Pump systems to provide a reasonable “payback”
period, and this can sometimes be linked to the expected life cycle of the
system or probably more closely linked to the warranty period offered for the products
involved. If the capital cost can be recovered within the warranty period then it is worth being given further consideration. However, when assessing the value of
adding Solar Thermal Collector Panels to a Heat Pump installation it must also
be remembered that during the daylight hours when the Solar Thermal Collector
Panels could be contributing to the energy input of the system, that is also the
period of each day that the Heat Pump units would be operating at their highest
efficiency as well so the amount of purchased (input) energy for the Heat Pump units during
the day time period could be between 3½ to 4.0 times less than the actual
output that is produced in the form of hot water depending upon geographical
location, ambient temperature and humidity.
The thermal contribution to a Heat Pump system from Solar
Thermal Collector Panels is governed by the amount of radiation that is available
at any given time and this can be intermittent because of varying weather
conditions. Therefore it is important
to recognize that the Heat Pump units must be considered as the primary heat
source and sized accordingly to be able to meet the total hot water requirement
of the project due to the reliability of Heat Pumps being able to produce
energy efficient hot water in all conditions including daytime, night time, as
well as cloudy or rainy periods. The
Solar Thermal collectors will therefore only provide supplementary energy input
during periods when there is a favorable level of radiation available for
collection. A number of factors can
influence the decision to add Solar Thermal Collectors to a Heat Pump
installation or not, but generally it has been found that in Regions where
Government or Utility incentives are offered for the inclusion of Solar Thermal
Collector Panels and the value of that incentive covers the cost of the Solar Thermal Collector Panels then obviously the economic equation is positive
however, when no incentives or subsidies are available then there are some
questions that need to be asked as to the added value of the Solar Thermal Collector Panels fitted to Heat Pump Units.
