About Solar Water Heaters
Solar water heaters are probably the most commonly used applications of Solar Energy. These have been around for a long while now. These heaters are efficient and economical and helps cut down on energy bills. Since they’ve been around for quite some time, they’ve evolved technologically over time.
A solar water heater usually comprises of the following components – solar thermal collectors, a water storage tank, a circulation system, and sometimes a back-up gas or electric booster.
Solar thermal collectors installed on the roof heat a liquid kept inside an absorber. The circulation system circulates this heated liquid. Heat energy from this liquid is passed to the water kept in a storage tanks using heat exchangers. The storage tank is well insulated and therefore doesn’t lose heat. This is pretty much the working principle of all solar heaters.
Types of Solar Water Heaters
Before getting into choosing water heaters, let’s review the different kinds of heaters available in the market.
Solar heaters are broadly classified into direct systems and indirect systems. In direct systems, water itself is heated and then circulated. In indirect heating systems, a liquid is used (usually an antifreeze), which is heated and then the heat of the liquid is exchanged with water.
They are further classified into active and passive systems based on the mechanism used for circulation of hot fluid.
In active systems, pumps are used to circulate household water or the antifreeze liquid. They also have electronic controllers for regulating the overall heating process. These controllers make sure that the pump is on only when the circulating fluid is warmer than the water stored by around 8 degrees Celsius. This way overheating of water can be avoided.
In passive systems, circulation depends purely on natural convection forces. Since warmer air rises, the storage tanks are placed above the solar thermal collectors. They are cheaper than active systems but aren’t really reliable.
Choosing Solar Water Heaters
Against this backdrop, let’s look at what kind of solar heaters to go for.
- If there are many people in your household, water consumption rate will also be very high. Added to this, if you live in a region with warm climate, a direct active heating system would be the best choice for you considering overall cost and efficiency.
- If your home water consumption is high and is more during the morning hours, you should go for an indirect active heating system with a drainback system. This drainback system will ensure the there is no heat-induced damage to the antifreeze liquid or the solar collectors. Moreover these systems ensure that heat from water isn’t lost during the night time.
- If you’ve hot weather all year round and are cost conscious and do not wish to get into the hassle of maintaining the heating system, passive heaters are the best for you.
- If you live in a region with a moderate climate and are on a moderate budget, go for a thermosyphon system. Thermosyphons are passive systems that are built to work well in cold climates.
- If you in a cold place, you should never go for a direct heating systems. It’s always better to go indirect systems that come with antifreeze liquids. These systems can function well even during cold temperatures.