If you are looking to save money on your monthly energy bills, sticking to an ancient process that’s still in use today may help – using the sun to heat up water. Yes, we’re talking about Solar Water Heaters! The first one was patented by Clarence Kemp in 1981 and since then the technology has matured with improvements in design, storage, and components to turn into a reliable water heating solution today.
But why should we switch from our regular old geysers?
Solar water heaters offer some unrivaled advantages over conventional electric geysers. Here is an exhaustive list of all the benefits that you can expect to enjoy when switching to a solar water heating solution.
- Saves you money:
A solar water heater can supply 80 percent of your hot water needs. On average, a 100 liter per day capacity solar water heater can save you up to 1500 units of electricity per year. This roughly translates into a 3-4 years payback period. After which, you’ll literally have free hot water for the rest of the equipment’s life span which is often estimated to be 25-30 years and considering solar energy is free of cost. A lot of cost savings indeed! - Round-the-clock hot water supply:
Solar water heaters come with insulated water storage tanks to store hot water and make it readily available for use even after sunset. You can also add a heat pump to the solar water heaters for a reliable round-the-clock hot water supply. - Low Maintenance:
Solar water heaters have no moving parts and therefore no tear, wear, or breakages, which means that they’re relatively low on maintenance. If the pump and antifreeze are considered, relatively inexpensive annual maintenance can ensure that everything works just fine. In case you have hard water that is fed into the water heating system, you may need to descale the collector tubes as and when you face heating and water flow issues. But this can also be fixed using water softeners. - Rust-free, hygienic hot water for use:
Geysers are made up of metals that can rust. This can contaminate the water. On the other hand, solar water heaters often come with stainless steel or glass enamel tanks that prevent rusting. Thus, providing you with rust-free hygienic hot water and ensuring your safety. - Also helps in protecting the environment:
Electricity is produced using non-renewable energy sources such as coal and natural gas which are greenhouse gas emitters. On the other hand, solar water heaters depend on 100% clean, renewable solar energy. In fact, a 100-liter capacity solar water heater can prevent 1.5 tons of CO2 emissions according to the Department of New and Renewable Energy, Government of Haryana.
Okay the benefits seem great! But which one do you choose?
Selecting the right solar water heater requires you to do a lot more research than if you were just looking for a run-of-the-mill electric water heater, thanks to the different sizes, types and feature configurations that they come in! So let’s break down the various types of Solar Water Heaters on offer and go through the use cases that each of these work best in!
- Direct and Indirect Solar Water Heaters
Solar Water Heaters are classified into direct and indirect systems based on whether your water gets heated directly or indirectly
Direct Solar Water Heaters – Also referred to as open loop systems, these circulate water from the tank to the collector and back, delivering hot water for you to use. They are suitable for areas where the temperature rarely goes below freezing point.
Indirect Solar Water Heaters – Also referred to as closed loop systems, these use a heat-transfer fluid which is usually antifreeze. This liquid circulates through the collectors and piping systems and transfers heat from the collector to the water in the insulated tank through a heat exchanger. Such water heaters operate reliably in extreme cold or hot conditions, as the heat transfer fluid is averse to both freezing and overheating. - Active and Passive Solar Water Heaters
Solar Water Heaters can be differentiated into active and passive depending on whether or not they use pumps.
Active solar water heaters use an electric pump to circulate water or antifreeze through the system. They also regulate the circulation process through temperature controllers that assess the temperature difference between fluid leaving the collector and water in the storage tank to turn the pump on or off. This prevents frequent use of the pump and overheating of water in the tank.
On the other hand, passive solar heaters, also known as thermosiphons, do not use pumps but instead rely on natural heat-driven convection forces and gravity to circulate water or antifreeze through the system. In these, the water tanks are usually placed above the collectors to help with convection and ensure that there is some pressure.
An Integral Collector Storage system (ICS), another example of a passive direct solar water heating system, has a collector that also acts as a storage tank. The integrated setup is placed in an insulated glazed box that absorbs sunlight to heat the water.
Passive solar systems cost less and require less maintenance than active systems, but operate mainly in regions with moderate temperatures. On the contrary, active systems cost more, but can work even in cold regions and are more efficient due to a higher flow rate. - Evacuated-tube and Flat Plate Collector Water Heaters
Evacuated tube panels are made up of a series of 1.5 to 2-meter-long glass tubes arranged in rows, sloping lengthwise up and down the roof. These are best suited for cold regions or areas with low sunlight.
Metal flat plate collectors have a dark absorber plate under glass or plastic covers to absorb sunlight and heat the water flowing through them. They heat small batches of water on your roof and are used mainly in regions with sufficient sunlight all year round. They have no moving parts and hence require little maintenance.
Since they’re made of metal, flat plate collectors outlive evacuated tube collectors since they are made of glass.
Both these collectors can be used in direct, indirect, active, and passive solar water heating systems.
Now that you have learnt so much about Solar Water Heaters, you may be looking to buy one for yourself!
If you’re looking for a system that best fits your house, Check out our blog – Selecting the right water heater for your house!
On the other hand, if you’re looking to explore a commercial installation, check out our blog – Choosing Water Heaters for your Business