What Is Solar Water Heating?

Solar water heating is the conversion of sunlight into heat for water heating using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes. Solar Water Heating System are widely used for residential and some industrial applications.

A sun-facing collector heats a working fluid that passes into a storage system for later use. Solar Water Heating Systems are active (pumped) and passive (convection-driven). They use water only, or both water and a working fluid. They are heated directly or via light-concentrating mirrors. They operate independently or as hybrids with electric or gas heaters. In large-scale installations, mirrors may concentrate sunlight onto a smaller collector.
Freeze protection measures prevent damage to the system due to the expansion of freezing transfer fluid. Drain back systems drain the transfer fluid from the system when the pump stops. Many indirect systems use antifreeze (e.g., propylene glycol) in the heat transfer fluid.

In some direct systems, collectors can be manually drained when freezing is expected. This approach is common in climates where freezing temperatures do not occur often, but is somewhat unreliable since it relies on an operator.
When no hot water has been used for a day or two, the fluid in the collectors and storage can reach high temperatures in all non-drain back systems. When the storage tank in a drain back system reaches its desired temperature, the pumps stop, ending the heating process and thus preventing the storage tank from overheating.

Some active systems deliberately cool the water in the storage tank by circulating hot water through the collector at times when there is little sunlight or at night, losing heat. This is most effective in direct or thermal store plumbing and is virtually ineffective in systems that use evacuated tube collectors, due to their superior insulation. Any collector type may still overheat. High pressure, sealed solar thermal systems ultimately rely on the operation of temperature and pressure relief valves. Low pressure, open vented heaters have simpler, more reliable safety controls, typically an open vent.

Sample designs include a simple glass-topped insulated box with a flat solar absorber made of sheet metal, attached to copper heat exchanger pipes and dark-coloured, or a set of metal tubes surrounded by an evacuated (near vacuum) glass cylinder. In industrial cases a parabolic mirror can concentrate sunlight on the tube. Heat is stored in a hot water storage tank. The volume of this tank needs to be larger with solar heating systems to compensate for bad weather and because the optimum final temperature for the solar collector is lower than a typical immersion or combustion heater. The heat transfer fluid (HTF) for the absorber may be water, but more commonly (at least in active systems) is a separate loop of fluid containing anti-freeze and a corrosion inhibitor delivers heat to the tank through a heat exchanger (commonly a coil of copper heat exchanger tubing within the tank). Copper is an important component in solar thermal heating and cooling systems because of its high heat conductivity, atmospheric and water corrosion resistance, sealing and joining by soldering and mechanical strength. Copper is used both in receivers and primary circuits (pipes and heat exchangers for water tanks).

Another lower-maintenance concept is the 'drain-back'. No anti-freeze is required; instead, all the piping is sloped to cause water to drain back to the tank. The tank is not pressurized and operates at atmospheric pressure. As soon as the pump shuts off, flow reverses and the pipes empty before freezing can occur.

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How It Works

Residential solar thermal installations fall into two groups: passive (sometimes called "compact") and active (sometimes called "pumped") systems. Both typically include an auxiliary energy source (electric heating element or connection to a gas or fuel oil central heating system) that is activated when the water in the tank falls below a minimum temperature setting, ensuring that hot water is always available. The combination of solar water heating and back-up heat from a wood stove chimney can enable a hot water system to work all year round in cooler climates, without the supplemental heat requirement of a solar water heating system being met with fossil fuels or electricity.

When a solar water heating and hot-water central heating system are used together, solar heat will either be concentrated in a pre-heating tank that feeds into the tank heated by the central heating, or the solar heat exchanger will replace the lower heating element and the upper element will remain to provide for supplemental heat. However, the primary need for central heating is at night and in winter when solar gain is lower. Therefore, solar water heating for washing and bathing is often a better application than central heating because supply and demand are better matched. In many climates, a solar hot water system can provide up to 85% of domestic hot water energy. This can include domestic non-electric concentrating solar thermal systems. In many northern European countries, combined hot water and space heating systems (solar combisystems) are used to provide 15 to 25% of home heating energy. When combined with storage, large scale solar heating can provide 50-97% of annual heat consumption for district heating.

Advantages 

You’ll Never Run out of Solar Energy

Solar energy is collected through the direct sunlight that you get on your property. As long as the sun is still shining, you’ll never have to worry about running out of energy. One of major advantages of solar energy in South Africa is that the supply will never be exhausted, even when you have a lot of clouds in the sky. The solar energy will always continue to replenish itself.

No Electricity Bill for Energy from Direct Sunlight

Another of many advantages of solar energy is that you won’t have a bill from the electricity company when you have the sun giving you solar energy for free. You do however need to get the equipment to take advantage of the energy that you can get for free. Once your property is solarized, you’ll never get a bill again from your local utility company. You will have a return on investment quickly. In addition to the equipment, you’ll need to get solar panels installed by a professional.

Switching to Solar Energy is a Cost-Effective Alternative

Technology for switching to solar energy is changing rapidly and it’s also improving. Yes, it is expensive, but the amount of energy that you can get from the photovoltaic panel technology can be obtained economically. The reason why you need to go with the flow of technology is that you need new ways to keep your energy costs in control. As technology improves, the cost of the technology will decrease.

Solar Energy is Safe for the Environment

The traditional method of getting and using energy harms the environment because fossil fuels can give you a highly polluted area to live in. Solar energy does not contaminate your home or anything outdoors. There aren’t any emissions that harm anyone or anything.

You are minimizing the negative effects by going green. Another one of many advantages of solar energy is that not only are emissions eliminated, you can also stop noise which is also a type of pollution.

You Can Access Solar Power and Energy Anywhere

Solar energy can be accessed anywhere. The only prerequisite is that the sun must shine there. If an area that you install in doesn’t have any power cables or other source of electricity, you can have and use solar energy to power anything.

No Maintenance with Your Solar Energy System

The advantages of solar energy in South Africa also include that once you have your solar energy system installed and set up, you don’t need to maintain it in any way. You don’t need to spend anything besides your initial setup costs. You may need to add a solar panel later on but you won’t need to install a brand-new system. There are no additional costs associated with having a solar energy system in your home or business.

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