The laypersons guide to solar.

 

Solar is the new buzzword, but what does it all mean

 

The sun supplies earth with heat and light. Anything referring to the sun is called SOLAR. Both heat and light are solar energy sources.
 

The heat energy is called solar thermal.
 

The light energy is also called solar PV or photovoltaic.

For all practical purposes you cannot mix the two.

 

You cannot use solar heat to make electricity.

 

You cannot use solar light to generate heat.

 

We at Sunpower Solar Water Heating specialize in Solar Thermal – this is heating geysers with solar heat.

The basic principles are :

The more people using hot water, the more storage you need = bigger geyser. We average 50 litres of hot water storage per adult per day.

The bigger the geyser, the bigger the heating panel needed to heat the water.

The closer the panel to the geyser, the greater the efficiency of the entire system

The fewer components needed, the cheaper the system.

We provide several systems for private houses.

They range from R3700 to over R20 000.

In order of increasing cost they are:

 

1. Low pressure one piece systems with the system placed as high as possible on your roof. This is especially applicable to low income houses where no geyser has ever been installed. (Low pressure system)

 

1. High pressure two piece systems with the heating panel and a special solar geyser both being outside either on a pitched roof or on a stand on a flat or very slightly sloping roof. (Close coupled external system) Available in 150 litres – 300 litres

 

Flat roof stand with a close coupled external system – 150 litres

 

Close coupled external system on a pitched roof - 200 litres

 

Close coupled external system on a pitched roof – 150 litres.

1. High pressure two piece system with the heating panel outside on the pitched roof, and the special solar geyser being inside the roof on a base above the top of the heating panel. (Split thermosiphon system) Available in 150 litres – 300 litres

 

In this system, the roof is steep enough to have the geyser inside the roof above the heating panel. 200 litres geyser inside the roof.

1. High pressure two piece system with the heating panel outside on the pitched roof, and the special solar geyser or converted regular geyser being inside the roof. The water is pumped from the geyser through the heating panel and back into the geyser. An intelligent pump controller turns the pump on when the water heating panel is hotter than the geyser water, and turns it off when the panel is no longer hotter than the water inside the geyser. (Split pumped system) Available in 150 litres – 300 litres

 

 

In this system the geyser is a long way from the heating panel, so a pump is required. The copper piping is well insulated. 200 litre geyser inside the roof.

EFFICIENCY

Ironically the efficiency is also in the same order with the most affordable system being the most efficient. However there are different advantages and drawbacks associated with each type of system. Generally the drawbacks are highlighted as the household income increases. The richer you are, the fussier you can afford to be!

Advantages –

1. Low pressure. The heating panel links into the geyser for maximum efficiency. The system is immediately above the point of use, so there are minimal losses. It is possible to use lower pressure ( cheaper) plumbing fittings and piping. Any problems from a leak will not result in damage inside the house.
2. Close coupled external system. The geyser and heating panel are very close to each other, so the system is efficient in gaining heat.
3. Split thermosiphon system. The geyser is hidden from view. No pumps or controllers are needed.
4. Split pumped system. The geyser can remain where it is. It is possible to convert some regular geysers to solar geysers. Some pump controllers include geyser element timers. The piping between the heating panel and geyser is thinner (cheaper) than for thermosiphon systems.

Drawbacks –

1. Low pressure. The flowrate through the pipes and taps is limited by the height of the geyser on the roof above the taps. It will be slower than water supplied by municipalities. It is best used when taps to the bath or basin are separate. Care must be taken to balance the pressure to showers and mixers. Mixers and showerheads if used cannot have small holes as this restricts the water flow and may result in poor water flow. The roof angle and direction are critical to the efficiency of the system. Any roof that is not north east to north west facing will either need a special frame built for it at greater cost, or will lose efficiency. Low pressure external systems are not well known in South Africa, so a specialist plumber may be required.
2. Close coupled external system. The geyser insulation is critical. The best insulated geysers provide the best systems. Unfortunately the standards in South Africa are not stringent and no manufacturers are prepared to advertise their real losses to differentiate their geysers from their oppositions. This leads people to choose geysers purely on price. Externally fitted geysers need better sealed electrical connection points to prevent rain getting into them (called IPX4) that are more expensive. You cannot add a geyser blanket to an external geyser.
3. Split thermosiphon system. The piping from the heating panel to the geyser needs to be 22mm and well insulated. The shallower the roof pitch, the longer the pipe length will be and the less efficient the complete system. Longer pipe lengths cost more and reduce the efficiency of the system. In most cases you will need to raise the geyser above the ceiling onto a special wooden base to get good water flow between the heating panel and the geyser.
4. Split pumped system. You need an electric pump and a pump controller to get maximum efficiency. The pumps and controllers are relatively expensive compared with unpumped systems. The electrical components have a shorter expected lifespan than the rest of the system.

Pricing excluding installation

1. Low pressure external system

· 100 litre system R3700

1. Close coupled external system.
   • 150 litre
   • 200 litre
   • 250 litre
   • 300 litre
2. Split thermosiphon system.
   • 150 litre
   • 200 litre
   • 250 litre
   • 300 litre
3. Split pumped system.
   • 150 litre
   • 200 litre
   • 250 litre
   • 300 litre