Procurement

Careful analysis of the prerequisites is required for a successful solar heating investment. An early and thorough survey of the physical basis is essential. This includes the different locations for the solar collectors, space for the storage tank and the system equipment, and the pipe runs to and from the solar collectors. It is also important to note and consider the advantages of combinations of systems where solar heating can make a contribution, and the synergies that can be gained. Of course the will to invest and the costs for alternatives must also be established. See the checklist in Box 9.1. Box 9.1 Start the right way Make a survey of the prerequisites; evaluate suitability

Are the basic conditions suitable for solar heating? This is the main determinant for investment. Check the summer load; check that roof areas are available, and that there is space for pipe runs and the storage tank. Apart from this the other decisive factor is the possibility of designing a heating system to which solar collectors can be connected. The will to invest and the profitability requirement are other essential factors.

Design and size accurately

The solar heating plant will give the best results (for both heat production and economy) if the size is optimized. The area of the solar collectors and the volume of the storage tank must be suited to existing conditions. Correct input data is essential for good preliminary studies and design and sizing work.

Choose a technique with quality

A solar collector is exposed to tough external conditions – everything from snow, ice and wind to very high working temperatures (in some cases over 250°C). Choose a solar collector that has been tested by a certified testing station. The testing stations have lists of solar collectors that have passed the initial tests, thereby giving a form of quality label.

Orientate the solar collectors correctly

Choose a favourable orientation (see Table 2.1), and avoid overshadowing. Solar collectors produce no heat at all when completely in shadow.

Heat store

The storage tank is often the most important component in a heating system and therefore affects the operation, output, economy and, in some cases, the convenience (service and need for inspection). The design and construction of the heat store determine the efficiency of the system. Decisive factors are, for example, temperature stratification and heat losses (degree of insulation) and also that the overall system is suitable for the heat producers included and correctly connected, according to the supplier’s instructions.

Choice of components

All component parts in the solar collector loop are exposed to the heat transfer fluid, which has specific properties and high working temperatures. To prolong the operation and service life of the system, the components must be of the quality to stand the stresses they are subjected to. Some components must be inspected annually, and this must be made clear in the running and maintenance manual (for example the freezing point and corrosiveness of the heat transfer fluid, the function of the pump and control unit, cleaning of the filter, solar collector fixings). The regulations and recommendations for the relevant country must also be followed.

Control devices

Some safety components are obligatory in the system, such as the safety valve, and the manometer for reading pressure. Other components are advisable, to be able to check the operation: for example temperature sensors on the supply to and return from the solar collectors and at different levels in the storage tank. A flowmeter is also useful. A time recorder on the pump for the solar loop is useful to be able to compare operation times between different periods (the same month, different years and so on).

Choose the supplier carefully

Choose a supplier who can give satisfactory guarantees, references and running and maintenance manuals. It is a great advantage if the supplier has a local representative (retailer) with regard to the possibility of quick service and inspection. In the same way the stock kept of the most important spare parts and the quality of the products delivered should be checked.

Visit a plant in operation

To get an idea of the technology a visit should be made to a plant in operation. The user can give valuable information on operation from experience.