Introduction

Definitions

The somewhat arid discussion of the semantics of active hybrid and passive systems has been alluded to in the previous chapter.

Here, an active system is really taken to mean a bolt-on arrangement, which is usually not part of the building structure (for example, a solar hot-water heating system) and which often involves pumps or fans. Of course, some solar air heaters do form the roofs of buildings (see Section 5.2) and some hot-water systems flow naturally by a thermosiphon.

Popularity of solar heating

The UK Solar Trade Association assesses how widely such systems are used, and the 1981 figures show that there are 60 firms manufacturing solar systems or components or installing them. From 1974 to 1981, 173,000 m2 of collector were produced. About 21,000 m2 of hotwater system were installed in 1981, comprising about 5000 systems. About 2400 swimming-pool systems have been installed from 1974 to 1981. The main complaints seem to involve misunderstandings either by clients or manufacturers of the likely output or benefit of a given system. There has been no ‘Gallup Poll’ of users' reactions in the UK, but in the US a study for the Solar Energy Research Institute shows these conclusions: two-thirds of houseowners strongly wish to see solar energy developed over other sources; one-third of people feel solar is technically and economically practical today for homes; two-thirds of people have not considered investing in solar technology for their homes.