Solar water heating
Practical Action
Type
Output
Temperature (°C)
Uses
Sector
Mounting
Glazed & liquid-based
30-80
Heating, domestic
hot water,
swimming pool
heating (indoor)
Domestic, commercial
buildings, leisure
centres
New build and
retrofit as flexible
mounting
possibilities.
Glazed & air-based
20-50
Heating of
ventilation air. Can
sometimes provide
domestic hot water
heating.
Domestic
Roof-mounted
Unglazed & liquid based
Unglazed & air-based
<30
20-30
Outdoor swimming
pool, car wash and
fish farm water
heating
Heating of
ventilation air,
crop drying
Commercial
Commercial
Flexible
Wall-cladding
Table 3: Types of Flat Plate Collector (Capturing Solar Energy, 2009)
Although liquid-based collectors are more prone to freezing and/or overheating, they are
generally more efficient than their air-based counterparts.
There are two main types of evacuated tube collectors:
Type
Direct-flow
Heat pipe
Output
Temperature (°C)
Uses
50-95
Domestic hot water and swimming
pool heating (indoor), cooling
50-95
Domestic hot water and swimming
pool heating (indoor), cooling
Sector
Domestic, Commercial
Domestic, Commercial
Mounting
Horizontal and vertical mounting
possible
Mount at an angle >25° to horizontal
Table 4: Types of Evacuated Tube Collector (Capturing Solar Energy, 2009)
Although evacuated tube collectors are able to operate at lower radiation levels and provide
higher output temperatures than flat plate collectors, they are more expensive and therefore
less widely applied.
The size of the installation is dependent on location and capacity required as the collector area
is proportional to its efficiency. Certain rules of thumb defined by the Chartered Institute of
Building Services Engineers (CIBSE) can be used as a guideline when sizing a system. From
the below it is evident that less area is required for the evacuated tube collectors as they are
more efficient. However, this should be considered alongside their higher cost when selections
are being made.
Required collector area:
Flat plate:
Evacuated tube:
1.0-1.5m2 of absorber per person
0.7-1.0m2 of absorber per person
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