Why pay more for gas or electric when you can get solar hot water? A solar hot water heater can save money on utilities bills, while giving you that good feeling of helping the environment.
Solar water systems do exactly as the label suggests: They leverage the natural heat from the sun to warm up water for home or commercial use.
Solar systems are especially useful in warm climates where freezes aren’t a major issue. Still, people colder climates can still use solar water heating systems, as long as they have freeze protection. The initial costs for a system designed for a colder climate will also be a little higher.
Solar Hot Water System Designs
A solar hot water system can come in a variety of designs. These are generally categorized by how the water or heat is collected, and how the liquid is pumped through the system.
Commercial solar water heating technologies are available, though not always easily accessible via large utility companies. For example, in Australia, you can’t find Origin Energy solar hot water systems – they offer gas and electric hot water solutions.
You can also build your own solar water heater. This requires a significant amount of time and effort, and includes the purchase of a variety of materials, including some sort of tank (such as old electric boiler), a window frame, and copper piping. You can find many step-by-step DIY solar water heater tutorials online.
Just be aware that if you live in a city or other municipality with zoning laws, your home-grown water heater may violate local regulations. People who live in rural areas without much local government oversight will have more opportunity to build and test such homegrown solar water systems.
Types of Solar Water Heater Collectors
A solar water heating system requires a tank to store the heated water, and collectors, which is where the water is collected and heated prior to storage. Here are the three main collector types:
1. Batch Collectors / Integrated Collector-Storage (ICS) Systems
Batch collectors (also known as ICS systems) heat the water in tubes or tanks that reside in an insulated box. The water can collect for a while in these tubes and get very hot, so a tempering valve mixes cold water with the hot to protect from scalding. These types of collectors don’t work as well in cold climates.
2. Flat-Plate Collectors
Flat-plate collectors, as you would expect, use flat “absorber plates” that are connected to copper tubes. These can generally hold up to 40 gallons of water, which is enough for one person. Therefore, families would need more flat-plate collectors to generate the amount of hot water needed.
3. Evacuated Tube Collectors
Evacuated tube collectors are the most efficient and work the best in colder climates. They can even work when it is cloudy outside. Unfortunately, they are also the most expensive type of solar water collector.
They are called evacuated tubes because they work a bit like a thermos. A tube is placed within another tube, and between those tubes is a vacuum. The vacuum prevents heat loss.
Types of Solar Water Heater Circulation Systems
Of course, once the water is heated by the sun, it will need to be circulated so people can benefit from it. Here are the types of solar water circulation systems:
1. Direct Systems
In a direct system, the water itself is circulated after it is heated. Because water can freeze, this system requires freeze protection in colder climates.
2. Indirect Systems (Closed-Loop)
In an indirect system, a non-freezing liquid is utilized to capture the solar heat, and then that liquid is put through a heat exchanger to heat up the water in the storage tank. As you would expect, this is the preferred system to use in colder climates where the temperature regularly goes below zero.
3. Passive Systems
Passive systems circulate the water or liquid using natural convection. Natural convection is a natural property of fluid whereby it can circulate due to the differences in temperature in the fluid. This is the same way that the atmosphere circulates around the planet, causing wind.
4. Active Systems (Forced Circulation)
An active system must use an electrical pump system to move the water. For the person who wants to stay off the grid as much as possible, this brings up the issue of how that electricity is generated. It is possible to run the pumps off of solar power as well.
The Future Will Include Solar Hot Water
While solar hot water heaters have not become mainstream yet, as gas and electric prices continue to increase, solar water heating will become more popular. This will be especially true in the south and other areas with temperate climates.