How to Select a Solar Water Heating System

Deciding on which solar system is best suited for an application is a complicated process due to the various aspects which need to be considered. EFA Solar’s dedicated sales team is always available to assist you with any queries regarding Solar Water Heating and to help you through the process.

Below is a list of the most significant factors that need to be taken into account:

System Size

This is a very important consideration to ensure you achieve all the benefits of a Solar Water Heater, without compromising your lifestyle in any way. The average person uses 40-50 litres of hot water a day. By multiplying this number by the number of people in your household you can get an estimate for an appropriate size tank.

Evacuated Tube or Flat Plate Collector

Flat Plate collectors present a good solution for thermosyphon systems due to their longitudinal internal tubing, which aids in the density differentially driven water flow. Due to their basic components and simplified construction, these collectors tend to be a more cost-effective option and with the advancement of technology and the introduction of non-reflective glass, have far better efficiency than the previous generation of Flat Plate collectors. Flat Plate collectors are more suited to higher ambient temperature environments (such as the lower lying areas of northern South Africa), where the relatively high heat-loss co-efficient is not as critical. Evacuated Tube Collectors are considered new technology in the Solar Water Heating industry and have only recently been introduced into the South African market. Due to their very high conversion efficiencies, they have significantly increased the scope of the Solar Water Heating industry. These high efficiencies are attributed to the very low heat-loss factors due to the vacuum insulation of the tubes and the circular cross sections which allow the tubes to function even when the sun is low in its arc. These collectors are ideally suited to areas of extreme latitudes or experience low ambient temperatures such as the High Veld and Western Cape areas of South Africa.

Pumped or Thermosyphon

Thermosyphon systems are a cost-effective solution. However, in the majority of cases this system requires the tank to be mounted on the roof, above the collector, in a close coupled configuration. This arrangement is often deemed unsightly and may detract from the image of the home. It is possible to install a thermosyphon system with the tank inside the ceiling, however, this is dependent on the pitch of the roof being sufficient. If aesthetics are important, a pumped system provides greater flexibility as the relative positions of the tank and collector are not critical. The pumped system also provides greater efficiency and control, as the system is actively governed by a pump and thermostat which allows for specific temperature ranges to be set.

12V or 220V Controlled System

A pumped system can either be powered by mains(220V) supply or direct current (12 V). The mains supply option affords a higher circulating flow rate, but is susceptible to power failures. A DC power supply has a back-up battery, and may include a PV panel to power the circuit, offering a complete off-grid solution.

Eskom rebate or not

EFA Solar offers both Eskom accredited and non-accredited systems. The non-accredited systems are competitively priced, do not require the administration of claiming the rebate and carry the same guarantee as the accredited systems. The accredited systems, although initially more costly, become an economical solution once the rebate has been claimed from Eskom. In addition, the accreditation also serves as an endorsement of quality to the system.

Retrofit

A retrofit system is an option if your geyser is not older than three years.Retrofit systems offer a cheaper option as you simply convert your current electric geyser into a solar geyser. It must, however, be recognized that these systems will not be as efficient as a complete solar system. Tanks designed for solar systems are different to conventional geyser tanks in that they have greater insulation which reduces heat loss and have an additional two inlet ports for the collector attachment. The positioning of these ports plays a critical role on the system’s efficiency as they determine how the cold water mixes with the hot and where your outlet water is drawn off.

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