Not every location can benefit from solar power but research shows that 50% of UK households are suitable for the installation of solar collectors⁸. Suitability depends mainly on shade (from other buildings or natural features) and the availability of a south-facing angled roof.

The Greenhouse is situated in central Norwich (see Figure 4) in Norfolk, England, at a latitude of 52.6° N.

The Greenhouse uses two 30-tube arrays (see figure 5), each measuring 1.96 by 2.12 m (including the header pipe) and weighing 68 kilograms. The total surface area of collector tubes is 7.8 m².

Figure 5. The Greenhouse roof with two sets of evacuated tube collectors. The photo also shows the Greenhouse photo-voltaic panels, used to generate electricity.

In the Northern Hemisphere, the maximum solar radiation is received on south facing surfaces. Figure 6 demonstrates that the Greenhouse is almost south facing (200°). The ideal angle (also known as the pitch) of the roof is between 20° and 50° to the horizontal, at the Greenhouse it is 45°.

Figure 6. The orientation and sunlight exposure of the Greenhouse solar collectors.

The collectors can be self-installed and there are also companies that specialise in this procedure (see inside back cover). At the Greenhouse, the system took about one week for two people to install. This is above average as the Greenhouse is a large three-storey building on a busy city road with a relatively inaccessible rooftop that required scaffolding.

Figure 7. Installation of one of the 30-tube solar collector arrays on the roof of the Greenhouse.

Prior to the connection of the tubes, two hot water cylinders were installed along with all the internal pipework, both tanks have a capacity of 273 litres (60 gallons). The copper cylinders are foam lagged (CFC-free) for insulation with a single coil heat exchanger in the secondary (solar only) cylinder and a double coil (solar and gas-heated) in the primary cylinder. Figure 8 shows how the solar water system is linked to the cylinders and the domestic water supply. The use of two cylinders was considered beneficial because of the above average hot water requirements of the Greenhouse building. A normal home would generally only need one hot water cylinder.