Introduction

As the UK government tries to encourage more householders to produce their own energy, changingclimate.org takes a look at some of the benefits of solar water heating. We also point out some of the deterrents. Read this as the first step if you know nothing about solar water heating.

Solar water heating panels are on Bryant Homes at Newcastle Great Park. Photo courtesy: Bryant Homes.

Sections in this article

• The Pros and Cons

• Swimming pools

• Use of solar heating after disasters

• Solar water heating in Europe

• Where Next?

The Pros and Cons

Every solar water-heating system has a solar collector that faces the sun and either heats water directly or heats a "working fluid" that, in turn, is used to heat water. The heated water may be moved through the house with pumping mechanisms (active systems) or by natural convection (passive systems). There are many types of solar water heaters. Each has strengths to recommend it for specific climates and water conditions.

Solar water panel on a roof

In colder climates, an antifreeze solution runs through the tubes to keep the tubes from freezing.

 Benefits

• Fuel costs are free. Once the higher initial costs of a solar system are recovered through reduced or avoided energy costs (i.e., lower utility bills), solar systems require maintenance costs only.
• The cost of a solar water heating system is relatively minor if you include it in a 30-year mortgage. 
• Solar water heaters do not pollute. They do not contribute to the production of carbon dioxide, nitrogen oxides, sulphur dioxide, and other air pollutions.
• Solar water heating technology is effective regardless of ambient temperature. In colder climates, more energy is required to heat incoming ground-water, so using solar energy in these conditions can have a dramatic effect on utility bills. In addition, colder incoming ground water allows solar water heaters to operate at higher efficiencies.

Disadvantages

• The purchase and installation costs of solar water heating systems are still higher than the purchase and installation costs of conventional electric or gas water-heating systems
• Contrary to some beliefs, most of these systems are not designed to meet the entire hot water needs of most homes. Instead, solar water heaters are designed to pre-heat water. It takes a great deal of "traditional" energy-electricity, natural gas, or propane-to bring cold water up to the hot temperatures used in most homes. It subsequently takes much less of this expensive energy to bring already warmed water up to preferred temperatures. Depending on geographic location, solar water heaters can provide up to 80% of a home's annual water-heating needs.

Swimming pools

Solar swimming pool heating is the most common way that people in the United States utilize solar energy today. Solar pool-heating systems increase water temperature by 10 degrees or more over an unheated pool, and can extend the swimming season by two to three months. When systems are installed to replace a conventional gas or electric swimming pool heater, the initial investment can usually be recovered in approximately three years, sometimes less.

Swimming pool heating systems are also often used to offset or eliminate the use of conventional natural gas-fired swimming pool heaters, and in some cases electric heat pump pool heaters. A solar water heater offsets 1.5 to 2.5 tons of carbon dioxide per year.

Use of solar heating after disasters

Solar thermal systems can continue to provide some space heating as well as hot water when the grid is unavailable. When coupled with photovoltaic cells or wind to provide electricity, even fan- and pump-driven systems can continue to work.  Solar thermal technologies can also assist in recovery operations. Following hurricanes in Florida, portable systems were installed at emergency shelters, providing the hot water necessary for sanitation. Small portable personal systems, long used by the recreational community, have provided welcome hot showers to rescue workers in disaster-relief efforts.

Two surveys of business communities affected by natural disasters identify power as extremely important. Following the 1994 Northridge Earthquake, the University of Southern California conducted a survey to identify reasons for business interruption. Fourth ranked was loss of utility services, following employee inability to get to work, employees dealing with personal matters, and a damaged workplace. In a second study, the University of Delaware's Disaster Research Center surveyed businesses to determine what services were considered most critical. Two communities were selected, one that had been damaged by floods and one that is susceptible to earthquakes. Businesses in both communities cited electricity as the most critical "lifeline" service, more essential than telephones, natural gas, or water. Losses from disrupted power can be as much as 40% of the total insured loss, according to a report by Lawrence Berkley Laboratories. Electricity-producing technologies like photovoltaics and wind can mitigate these effects.

Solar water heating in Europe

Solar thermal water heating technology has been used for over 60 years. Over 1 million domestic solar water heating systems have been sold in Greece since the early-1990s. Principally used for heating water in private houses, public buildings and swimming pools. Although the use of active solar technologies would not be expected to meet a large proportion of the total energy needs of Europe, they are reliable, have a reasonable life span and are particularly suited to local manufacture. There is much potential for solar power, especially in the islands.

In Denmark there is progress with around 5% of new dwellings constructed with the capacity to heat water by solar power. The main obstacles to increasing the share of solar water heating are architectural preferences for ‘the traditional' and the excessively long payback times for solar technology. The payback is affected by the size and complexity of the system (Greek ones are highly standardised, simple and low cost), the need to protect from frost and reduced sunshine hours in winter, as well as the cost of the replacement fuel.

Where Next?

On ClimateX.org

For more of a background on solar photovoltaics- the use of solar energy to produce electricity- see "Introducing Solar Photovoltaics" in this section.

External links

A good overview and information about solar water heating can be found at the U.S. Department of Energy

If you are interested in a first hand account from someone in the North of the UK who has installed solar water heating panels, we recommend visiting the following firsthand account written by a lady in Cumbria.

For an inspirational account of one Oxfordshire woman's ongoing conversion of her house from normal semi to ‘ecohouse', including solar water heating, see this link (the process continues to be updated in 2007) http://www.sageoxford.org.uk/ecohousef.htm

There are 7 excellent case studies about pioneers who have carried out 'eco-conversions' on very different types of houses. Read full details and view photos at the 40% house 'pioneers' pages.