A solar water heater is the most competitive alternative to conventional water heating methods such as electric geysers and fuel-fed boilers. It makes an attractive and sustainable option, with its global distribution, pollution free nature, virtually inexhaustible supply and near-zero operational cost. Solar water heaters run on a free fuel (i. e. sunshine), thus saving on energy costs that help recover its initial cost in just 2-4 years. Hot water throughout the year: the system works all year round, though you’ll need to heat the water further with a boiler or immersion heater during the winter months.
Cut your bills: sunlight is free, so once you’ve paid for the initial installation your hot water costs will be reduced. Cut your carbon footprint: solar hot water is a green, renewable heating system and can reduce your carbon dioxide emissions. Solar water heating systems use solar panels, called collectors, fitted to your roof. These collect heat from the sun and use it to heat up water which is stored in a hot water cylinder. A boiler or immersion heater can be used as a back up to heat the water further to reach the temperature you want.
There are two types of solar water heating panels: evacuated tubes (as in the picture above) flat plate collectors, which can be fixed on the roof tiles or integrated into the roof. Larger solar panels can also be arranged to provide some contribution to heating your home as well. However, the amount of heat provided is generally very small and it is not normally considered worth while. Maintenance costs for solar water heating systems are generally very low. Most solar water heating systems come with a five-year or ten-year warranty and require little maintenance.
Once fitted your installer should leave written details of any maintenance checks that you can carry out from time to time, ensuring everything is working properly. Perhaps the most important thing you can check for yourself from time to time is whether there are any leaks. If there are any leaks of anti-freeze (even if you can’t see any liquid) this will have a strong smell. If you notice this you should contact your installer. In general you should keep an eye on your system to check that it is doing what it has been designed to do.
If you are not getting hot water or the solar pipework is cold (when the pump is running) on warm, sunny days then again you should contact your installer. For peace of mind some installation companies offer an annual service check. You should have your system checked more thoroughly by an accredited installer every 3-7 years, or as specified by your installer. It is likely that after this period of time the anti-freeze that is used to protect your system in the winter months will need to topped up or be replaced as it breaks down over time reducing the performance of your system.
Anti-freeze lasts better if the solar water system is used throughout the year and not left unused during the warmest weeks of the year. This cost of replacing the anti-freezer is usually around ? 100. The other thing that your installer should check is the pump. In a well maintained system, pumps can last for ten years plus and usually cost around ? 90 to replace. Solar water heating systems can achieve savings on your energy bills. Based on the results of our recent field trial, typical savings from a well-installed and properly used system are ? 60 per year when replacing gas heating and ? 5 per year when replacing electric immersion heating; however, savings will vary from user to user. Typical carbon savings are around 230kgCO2/year when replacing gas and 500kgCO2/year when replacing electric immersion heating. Spherical reflector type cooker Spherical mirrors are the simplest type of concentrator and are easy to build and use. It is easy to focus sun rays, and if one opts for a moving vessel to meet the focus, cooking can also be done very easily. Such a design was suggested for the first time in the year 1961 by Stam (1961).
He suggested a large reflector of 4. m diameter made of local material which could even include mud, and the reflector surface suitably smoothed with fine mud/cement and coated with aluminized polyester. An appropriate technology handbook describes a simple method of construction of the spherical mirror in the ground (a tall tripod with a long string to which a stone is attached at the tip, will act as a guide for excavating a hollow in the ground) and after finishing and stabilizing the interior, the reflector material could be stuck to make it into a spherical mirror. Such a mirror, of about 2. m in diameter, would do useful work for at least five to six hours a day.
The cooking vessel could be hung from the tripod or a suitable stand and positioned to meet the focus. Dan Halacy (1974) suggests a similar design. He uses two full and several half cardboard ribs to fabricate the base and attaches mylar film as a reflector. This device was meant mainly for campers. Bamboo and/or other locally available materials could be used to fabricate such hemispherical baskets. Recently Prof. Quintone of the United Kingdom has taken up this design and is trying to popularize it in places likePeru.
In his beautifully designed and illustrated site he presents detailed instructions on fabricating the design and using it. The cooker below is a simple steel bowl used for carrying sand, is coated with a reflector foil and a blackened cooking vessel is put in it. The entire assembly is covered over by a flat sheet glass. The design is very similar toSuryakund cited by Kuhnke et al in their book Solar Cookers in the third world. In Suryakund, the vessels are kept in a inverted glass jar. Like Suryakund, this cooker too would suffer from limitation of size.
Unfortunately, this simple design has not attracted much attention, but on a very big scale, like in power generation (as in Marseilles, France), such a hemispherical mirror is being used (Jet Propulsion Laboratory 1981). Scientists ofAustralia (Anon. 1979) have presented a similar design. Margaret Koshoni developed the Cone Cooker to suit the needs of Nigerian women. Most people live in flats with balconies; the structure of the balconies will shade the CooKit and make a shadow. The Cone Cooker being placed on a stand has the advantage of elevation and the stand can be moved about without disturbing the cooking.
Medved et al. , propose an interesting design (1996) called a ‘SOLAR BALL’. It is an inflatable plastic ball with lower part of reflective material. The cooking vessel is kept at the base. It is an interesting variation but there appears to be some serious limitations with reference to size of the ball as well as size and handling of the cooking vessel. Recently, the spherical geometry seems to have made a come back, and we see that at Auroville in India a 15 meter diameter mirror cooks food for over 1500 persons. A similar large solar bowl was built at the University of Mexico. photovoltaic solar cells
PV cells are made from layers of semi-conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers. The stronger the sunshine, the more electricity is produced. Groups of cells are mounted together in panels or modules that can be mounted on your roof. The power of a PV cell is measured in kilowatts peak (kWp). That’s the rate at which it generates energy at peak performance in full direct sunlight during the summer. PV cells come in a variety of shapes and sizes. Most PV systems are made up of panels that fit on top of an existing roof, but you can also fit solar tiles.
Solar tiles and slates Solar tiles are designed to be used in place of ordinary roof tiles. A system made up of solar tiles will typically cost around twice as much as an equivalent panel system, although you will save the money you would have spent on roof tiles or slates. Solar tile systems are not normally as cost-effective as panel systems, and are usually only considered where panels are not considered appropriate for aesthetic or planning reasons. Solar PV needs little maintenance – you’ll just need to keep the panels relatively clean and make sure trees don’t begin to overshadow them.
In the UK panels that are tilted at 15° or more have the additional benefit of being cleaned by rainfall to ensure optimal performance. Debris is more likely to accumulate if you have ground mounted panels. If dust, debris, snow or bird droppings are a problem they should be removed with warm water (and perhaps some washing-up liquid or something similar – your installer can advise) and a brush or a high pressure hose (or telescopic cleaning pole) if the panels are difficult to reach. Always be careful if you are working above the ground or near the top of a ladder.
Alternatively, there are a number of specialist window cleaning companies who will clean solar PV panels for you at a cost (of around ? 30 based on our research in March 2012) depending on the size of your array and location. Many of these companies use a water fed pole system which does away with the need for a ladder. Once fitted, your installer should leave written details of any maintenance checks that you should carry out from time to time to ensure everything is working properly. This should include details of the main inverter fault signals and key trouble-shooting guidance.
Ideally your installer should demonstrate this to you at the point of handover. Keeping a close eye on your system and the amount of electricity it’s generating (alongside the weather conditions) will familiarise you with what to expect and alert you to when something might be wrong. The panels should last 25 years or more, but the inverter is likely to need replacing some time during this period, at a current cost of around ? 1,000. Consult with your installer for exact maintenance requirements before you commit to installing a solar PV system. Photovoltaics is the direct conversion of light into electricity at the atomic level.
Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity. The photoelectric effect was first noted by a French physicist, Edmund Bequerel, in 1839, who found that certain materials would produce small amounts of electric current when exposed to light. In 1905, Albert Einstein described the nature of light and the photoelectric effect on which photovoltaic technology is based, for which he later won a Nobel prize in physics.
The first photovoltaic module was built by Bell Laboratories in 1954. It was billed as a solar battery and was mostly just a curiosity as it was too expensive to gain widespread use. In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications.
A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photovoltaic module. Modules are designed to supply electricity at a certain voltage, such as a common 12 volts system. The current produced is directly dependent on how much light strikes the module. Photovoltaic solar plants work like this: As light hits the solar panels, the solar radiation is converted into direct current electricity (DC). The direct current flows from the panels and is converted into alternating current (AC) used by local electric utilities.
Finally, the electricity travels through transformers, and the voltage is boosted for delivery onto the transmission lines so local electric utilities can distribute the electricity to homes and businesses. Solar-Thermal plants work like this: Solar collectors capture and concentrate sunlight to heat a synthetic oil called therminol, which then heats water to create steam. The steam is piped to an onsite turbine-generator to produce electricity, which is then transmitted over power lines. On cloudy days, the plant has a supplementary natural gas boiler. The plant can burn natural gas to heat the water, creating steam to generate electricity.
Solar power plants use the sun’s rays to produce electricity. Photovoltaic plants and solar thermal systems are the most commonly used solar technologies today. ` Solar cells such as these are used in photovoltaic solar technology There are two types of solar power plants. They are differentiated depending on how the energy from the sun is converted into electricity – either via photovoltaic or “solar cells,” or via solar thermal power plants. Photovoltaic plants A photovoltaic cell, commonly called a solar cell or PV, is a technology used to convert solar energy directly into electricity.
A photovoltaic cell is usually made from silicon alloys. Particles of solar energy, known as photons, strike the surface of a photovoltaic cell between two semiconductors. These semiconductors exhibit a property known as the photoelectric effect, which causes them to absorb the photons and release electrons. The electrons are captured in the form of an electric current – in other words, electricity. Solar thermal power plants A solar thermal plant generates heat and electricity by concentrating the sun’s energy. That in turn builds steam that helps to feed a turbine and generator to produce electricity.
There are three types of solar thermal power plants: 1) Parabolic troughs This is the most common type of solar thermal plant. A “solar field” usually contains many parallel rows of solar parabolic trough collectors. They use parabola-shaped reflectors to focus the sun at 30 to 100 times its normal intensity. The method is used to heat a special type of fluid, which is then collected at a central location to generate high-pressure, superheated steam. 2) Solar power tower This system uses hundreds to thousands of flat sun-tracking mirrors called heliostats to reflect and concentrate the sun’s energy onto a central receiver tower.
The energy can be concentrated as much as 1,500 times that of the energy coming in from the sun. A test solar power tower exists in Juelich in the western German state of North-Rhine Westphalia. It is spread over 18,000 square meters (194,000 square feet) and uses more than 2,000 sun-tracking mirrors to reflect and concentrate the sun’s energy onto a 60-meter-high (200 foot high) central receiver tower. The concentrated solar energy is used to heat the air in the tower to up to 700 degrees Celsius (1,300 degrees Fahrenheit).
The heat is captured in a boiler and is used to produce electricity with the help of a steam turbine. Solar thermal energy collectors work well even in adverse weather conditions. They’re used in the Mojave Desert in California and have withstood hailstorms and sandstorms. 3) Solar pond This is a pool of saltwater which collects and stores solar thermal energy. It uses so-called salinity-gradient technology. Basically, the bottom layer of the pond is extremely hot – up to 85 degrees Celsius – and acts as a transparent insulator, permitting sunlight to be trapped from which heat may be withdrawn or stored for later use.