A solar water heater is a cost-effective system for generating hot water for domestic usage. They can be used in any climate condition, and the fuel they use--sunlight--is FREE! It can also provide up to 50% and 90% of a household's hot water requirements, depending on your climate and the model of your heater.
How a solar water heater works? The basic principle to how a solar water heater works is actually very simple. Cold water is spread put over the roof to be heated by solar energy harnessed by solar panels. The heated water is transported to a holding tank, or moved via its own heat or pumps to allow more cold water to be heated. In-built safety devices are also fitted in a solar water heater to prevent over-heating of water especially on a sunny day.
Solar water heater systems
There are two main types of solar water heater systems available in the market. The difference between these models is how water to be heated is transferred between the collection tank and storage tank.
Passive water collection heaters
This solar water heater system involves the collection of cold water on a tank that is mounted in the roof and heated via solar energy. They are also more energy-efficient as they do not require electricity to pump the water. There are two main circulation systems available for this:
- Open/direct circuit system - the tanks are linked to allow flowing of water from one tank to another. This system is good for areas that do not experience freezing conditions.
- Closed circuit/indirect system - it makes use of a heating fluid, present together with the water in the collection tank, to transfer its heat to the water upon heating. This system is commonly used in areas that experience frosts or freezing conditions during winter, as the heating fluid also possess anti-freezing properties. Such fluids include water and glycol/water mixtures.
To transport the water, passive systems used either gravity-fed or closed-coupled flow. The gravity-fed system has the water collection tank situated above the storage tank on the roof. Via natural gravitational force, the water is transported via pipes from the collection to the storage tanks and to your taps. For the closed-coupled system, the collection tank is located below the storage tank and via normal water pressure transport the water to storage and to your taps.
Active water collection heaters
This solar water heater system is good if you have limited space in the roof or already a traditional hot water system. The storage tank for this system can be situated on the ground or under the house, with the heated water from the collection tank pumped to the storage tank.
One benefit of this system is that it can be set up by just converting your already present traditional hot water system to that of a solar-powered system. However electricity is needed to power the pump if you have an active solar water heater system.
Regardless of what solar water heater system you install, you must position the solar panels in the roof at an angle that has maximum exposure to the sun's rays. One more point to consider is the size of the tank that you need to cater to your family's needs. Do not buy something larger than what you need.
In the event of days when the sun is not shining, you have to buy and install a booster to heat the water to prevent the temperature in your solar water heater from falling below a fixed value. Such boosters are powered by electricity, gas, petrol or diesel. However boosters are energy-guzzlers if they're used too often. Therefore timers can be installed if you realise that your booster system is being used too much.