GEYSERS

Reach for the sun ... go solar!

Along with the possibilty of constant power outages this winter, we may also be faced with a looming water crisis. You may have to bath or shower in cold water. We’ve taken a look at another possible solution to keep the water flowing in your home this winter ...

Solar Water Heating (SWH) is a system designed for heating water using energy from the sun. The way the system works, is that solar energy is collected by a panel, which is connected by pipes to a hot water storage device, like a hot water cylinder. These systems can be installed for domestic hot water, heating swimming pools and caravans to name a few.

Why should solar heating be considered?

Domestic hot water systems can cost effectively generate hot water for your home as they are fueled by sunshine, which is free! If these systems are installed properly by a proffesional, they should be virtually maintainance free. Solar water heaters also friendly to the environment as they reduces greenhouse gas emissions.

What are the pros and cons of using solar heating?

Solar heating can be used in conjuction with an existant gas or electric system. When there is a power outage, you can rest assured that you will have the luxury of free hot water. One should also take into consideration that solar energy is a renewable resource. However, a slight downside of solar heating is that the panels, installed on the roof may make your house look a little less ‘pretty’ and when electricity is cheap, the installation may take time to pay for itself, but regardless, you know you will always have hot water.

What different types of solar heating does one get?

Generally two systems are available. The direct circulation system, circulates household water through the collectors and into the home. This system works well in a climate where temperature rarely drop to freezing point, Gauteng not being suitable in winter. The other, the indirect circulation system, circulates a non-freeze, heat transfer fluid through the collectors and a heat exchanger. This then heats the water that flows into the home. This system is popular and recommended where temperatures do tend to drop.

How does solar heating work?

In order to heat water using solar energy, a collector is attached to iether the roof of a building, or a wall, facing the sun. In some cases, the collector may be may be free-standing. The working fluid is iether pumped, which is know as an active system or driven by natural convection – passive system, through it. The collector, a simple glass topped, insulated box with a flat solar absorber, made from a sheet of metal is attached to copper pipes and painted black. However, a set of metal tubes surrounded by an evacuated
(near the vacuum) glass cylinder, could also be used. A simple water heating system would pump cold water out into a collector to be heated. The heated water then flows back into the collection tank. Heat is stored in a hot water tank. The volume of this tank will be larger for a solar heating system in order to allow for bad weather, as the final temperature for the absorber is lower than a typical immersion or combustion tank. This type of collection tank could provide enough hot water for the average family.

How do seasonal changes affect the system?

Solar water heating depends on radiation and not on direct sunlight, so the system will still work when the weather is overcast. However in winter, although a panel can be effective in helping warm your water, you may still need to use your existing geyser to supplement some of your water heating needs. In Spring, summer and autumn, a solar panel can yield surprising results, often not needing any assistance from the geyser. Depending on the system you have, and how and when you use your hot water the most, you could find that almost all your water heating needs are met by a solar water heating panel at these times of the year.

Is a solar heating system cost effective?

Heating water can account for between 25 and 55 per cent of the energy consumed in your home. You can easily reduce your monthly water heating bills by selecting the appropriate water heater for your home and also by using some energy- efficient water heating strategies such as :

Like dishwashers, up to 90% of the cost of operating washing machines is associated with the energy needed to heat the water. Reduce the amount of hot water used by washing clothes in warm water, instead of hot, or in cold water, instead of warm.
Washing only full loads will also reduce hot-water consumption.
Reduce the amount of hot water used by turning the hot-water faucet off while shaving or brushing your teeth.
When you plan to be away from home for three or more days, turn the water heater thermostat down to the lowest setting, or turn the heater off completely. Be sure you know how to relight the pilot light on the gas heater before you turn it off.
For electric water heaters, install a timer that can automatically turn the heater off at night and on in the morning. A simple timer can pay for itself in energy saved in about one year. More expensive, multisetting timers are also available.Reduce the amount of hot water used by installing low-flow shower heads and faucet aerators.

What are solar panels made of?

Glazed flat-plate collectors are insulated, weather-proofed boxes which contain a dark absorber plate under on or more glass or plastic (polymer) covers. Unglazed flat-plated collectors, typically used for solar pool heating, have a dark absorber plate, made of metal or polymer, without a cover or enclosure. Integral collector storage systems, also know as ICS or batch systems, feature one or more black tanks or tubes in an insulated glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues on to the conventional back-up water heater, providing you with a reliable source of hot water. Evacuated-tube solar collectors feature parallel rows of transparent glass tubes which each contain a glass outer tube and a metal absorber tube attached to a fin. The fin’s coating absorbs solar energy but inhibits radiative heat loss. These collectors are more commonly used for commercial applications. Most decent panels have a 4mm hail resistant glass and are able to withstand most heavy hailstorms. If systems are installed correctly very little maintanance is required. Services are however recommended every two years.

The South African climate is very suitable for solar heating as we have lots of sunshine, something the government can not tax us on yet!