Solar Energy Perspectives - IEA

Solar Energy Perspectives: Buildings
Figure 4.9 Combination of ASHP with solar collectors
Heating system
Solar
collectors
Storage
Hot
water
Heat pump
Ambient
air
Cold
water
Source: Henning and Miara/Fraunhofer Institute for Solar Energy Systems.
Key point
Effective use of air-source heat pumps may require glazed collectors.
Heat pumps and solar thermal systems can either complement or compete with each
other. Heat pumps specially designed for domestic hot water may even rival solar water
heaters. In mild climates, these thermodynamic devices usually recycle low-temperature
heat from laundry rooms or garages and use it to warm water. In warmer climates, they
would take the form of “de-super-heaters”, using the rejected heat from air-conditioning
systems.
Heat pumps are not always run by electricity. Thermally driven heat pumps exist, and are
usually large and fuelled by natural gas in the commercial sector. In theory, thermally driven
heat pumps could be run by solar heat, but the mismatch between resource and demand
makes the investment economic only for reversible heat pumps used for both heating and
cooling, as shown below. In this case, solar heat will save a little additional electricity during
the heating season, and a lot more during the cooling season.
Space cooling, air-conditioning
Passive solar cooling is the cheapest option, mixing traditional practice with modern
technology. It includes the design of houses and other buildings, protection against the sun
in summer, thermal masses, ventilation, solar chimneys, use of solar walls to let fresh air from
the polar side enter the buildings, shadows, evaporation of water (deciduous trees provide
both), fountains, ponds and other attractive features. It extends to the design of streets and
cities.
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© OECD/IEA, 2011