Solar water heating or solar hot water is water heated by the use of solar energy. Solar heating systems are generally composed of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage. The system may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use. The systems may be used to heat water for a wide variety of uses, including home, business and industrial uses. Heating swimming pools, underfloor heating or energy input for space heating or cooling are more specific examples.
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.
Residential solar thermal installations can be subdivided into two kinds of systems: 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 such as 50°C. Hence, hot water is always available. The combination of solar water heating and using the back-up heat from a wood stove chimney to heat water 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.
History
Flat-plate collectors for solar water heating were popular in Florida and Southern California in the 1920s. Levi Yissar built the first prototype Israeli solar water heater and in 1953 he started NerYah Company, Israel's first commercial manufacturer of solar water heaters. Despite the abundance of sunlight in Israel, solar water heaters were used by only 20% of the population by 1967. Following the energy crisis in the 1970s, in 1980 the Israeli Knesset passed a law requiring the installation of solar water heaters in all new homes (except high towers with insufficient roof area). As a result, Israel is now the world leader in the use of solar energy per capita with 85% of the households today using solar thermal systems (3% of the primary national energy consumption).
During this time, there was some resurgence of interest in solar heating in North America. Technical innovation has improved performance, life expectancy and ease of use of these systems. Installation of solar water heating has become the norm in countries with an abundance of solar radiation, like Cyprus, Israel and Greece, as well as in Japan and Austria, where there is less.
In 2005, Spain became the first country in the world to require the installation of photovoltaic electricity generation in new buildings, and the second (after Israel) to require the installation of solar water heating systems in 2006. Australia adopted the mandatory regulation for solar thermal for new construction in 2006 as well.
Solar water heating systems have become popular in China, where basic models start at around 1,500 yuan (US$190), much cheaper than in Western countries (around 80% cheaper for a given size of collector). It is said that at least 30 million Chinese households now have one, and that the popularity is due to the efficient evacuated tubes which allow the heaters to function even under gray skies and at temperatures well below freezing.
Usage
Hot water heated by the sun can be used to:
- Heat water (e.g. for sanitary purposes such as showering, washing, ...)
- Generate electricity
Designs suitable for hot climates can be much simpler and cheaper, and can be considered an appropriate technology for these places. In the southern regions of Africa like Zimbabwe, solar water heaters have been gaining popularity, thanks to the Austrian- and other EU-funded projects that are promoting more environmentally friendly water heating solutions.
The global solar thermal market is dominated by China, Europe, Japan and India.
Israel
Israel's use of solar water heaters is estimated to save the country two million barrels of oil a year, and the country has the highest per capita use in the world. In the 1950s there was a fuel shortage in the new Israeli state, and the government forbade heating water between 10 p.m. and 6 p.m. As the situation worsened, engineer Levi Yissar proposed that instead of building more electrical generators, homes should switch to solar water heaters. He built a prototype in his home, and in 1953 he started NerYah Company, Israel's first commercial manufacturer of solar water heaters. By 1967 around one in twenty households heated their water with the sun and 50,000 solar heaters had been sold. However, cheap oil from Iran and from oil fields captured in the Six Day War made Israeli electricity cheaper and the demand for solar heaters dropped. With the 1970s oil crisis, Harry Zvi Tabor, the father of Israel's solar industry, developed the prototype solar water heater that is now used in over 30%-40% of Israeli homes.
In 1980, the Israeli Knesset passed a law requiring the installation of solar water heaters in all new homes (except high towers with insufficient roof area). As a result, Israel is now the world leader in the use of solar energy per capita (3% of the primary national energy consumption).
As of the early 1990s, all new residential buildings were required by the government to install solar water-heating systems, and Israel's National Infrastructure Ministry estimates solar panels for water-heating already satisfy 4% of the country's total energy demand. Israel and Cyprus are the per capita leaders in the use of solar water heating systems with over 30%-40% of homes using them.
Technique
In order to heat water using solar energy, a collector is fastened to the roof of a building, or on a wall facing the sun. In some cases, the collector may be free-standing. The working fluid is either pumped (active system) or driven by natural convection (passive system) through it.
The collector could be made of a simple glass topped insulated box with a flat solar absorber made of sheet metal attached to copper pipes and painted black, or a set of metal tubes surrounded by an evacuated (near vacuum) glass cylinder. In some cases, a parabolic mirror is used to concentrate sunlight on the tube.
A simple water heating system pumps cold water out to a collector to be heated, the heated water flows back to a collection tank. This type of collector can provide enough hot water for an entire family.
Heat is stored in a hot water tank. The volume of this tank needs to be larger with solar heating systems in order to allow for bad weather, and because the optimum final temperature for the absorber is lower than a typical immersion or combustion heater.
The working fluid for the absorber may be the hot water from the tank, but more commonly (at least in active systems) is a separate loop of fluid containing anti-freeze and a corrosion inhibitor which delivers heat to the tank through a heat exchanger (commonly a coil of copper tubing within the tank). 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 is open to atmospheric pressure. As soon as the pump shuts off, flow reverses and the pipes are empty before freezing could occur.
When a solar water heating and hot-water central heating system are used in conjunction, 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 in place to provide for any heating that solar cannot provide. 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.
The water from the collector can reach very high temperatures in good sunshine, or if the pump fails. Designs should allow for relief of pressure and excess heat through a heat dump.
Economics, energy, environment, and system costs
The typical 50 gallon electric water heater uses 11.1 barrels of oil a year, which translates into the same amount oil used by a typical 4 door sedan driven by the average consumer. Electric utility companies often provide electricity by burning and releasing energy from fuels such as oil, coal and nuclear energy. An electrical home hot water heater sits on an electrical grid and may be driving the use of unclean fuels on the other end of the grid. Solar water heating systems can significantly reduce such electricity consump
Hi Temp for Solar Pool Heating | Heatpumps | Heat Pump heating ...
Hi Temp Solar Pool Heating has brought fun and enjoyment to swimming pool owners throughout South Africa for many years with our quality range of Pool Heating Products.
Pool Heating | Swimming Pool Heating | Solar Pool Heating
HomeComfort offers great solar pool heating solutions to heat up your swimming pool energy efficiently.
Solar Pool Heaters Swimming Pool Heating Systems Solar Hot Water
Solar pool heating and solar water heating systems for houses that protect the environment through energy efficient green technology
swimming pool solar heating panels and systems information
About Solar Heating For Swimming Pools Introduction. Solar swimming pool heating is the most cost-effective application of solar energy. Unglazed collectors (solar panels), which ...
Certifications, approvals and testing of solar swimming pool heating ...
Certifications, approvals and testing of solar swimming pool heating systems and services by Solar Industries.
Poolsolar swimming pools solar heating swimming pool solar matting ...
Poolsolar swimming pool solar matting swimming pool solar mat matting system low cost diy pool heating UK Great Britain
Pool Heating | Solar Pool Heating | Solar Panels
Experience the Cape Solar Heating difference today, call 021 556-7228 . Solar pool heating is great, it means the difference between swimming occasionally, to swimming every ...
Solar Pool Heating - By Deluxe Pool Heating of Perth Australia
I just had to write to express our gratitude for the very professional installation of our new swimming pool solar heating system.
Solar Pool Heating Warm Water. No Energy Costs in Marbella Costa del ...
You are here because: you own a swimming pool you are paying for maintenance 12 months per year you do not really swim that much outside of the summer months
Cape Town Solar Pool Heating Specialist
Why Solar Solutions - Why solar pool heating? The unique individual tube design by SOLAR SOLUTIONS ... Your solar heated swimming swimming pool is a big investment. Maximize on ...