| Introduction | | | | |
| | | | Â- Reduces your energy bill |
| Solar water heating systems use sunlight to | | | | |
| heat water. Solar energy is a pollution free | | | | Â- It is environmental friendly and |
| and rich energy resource that can be used to | | | | pollution free |
| complement many of your energy requirements. | | | | |
| Solar energy can be used as a form of heat as | | | | Â- Reduces greenhouse emissions by |
| in the case of solar water heating. | | | | minimizing the use of electric or gas water |
| | | | heater |
| Solar water heating systems are a combination | | | | |
| of solar thermal collectors, a fluid system | | | | Â- Qualifies for the 30% federal tax credit |
| to pass the heat from the collector to the | | | | |
| point of use, and a tank to store heat for | | | | Â- Doubles the amount of hot water available |
| later use. The systems can be used to heat | | | | |
| water for domestic or business consumption, | | | | Selecting a Solar Water Heater |
| for swimming pools, under floor heating, | | | | |
| energy source for space heating and cooling | | | | In the United States the typical hot water |
| and industrial uses. | | | | usage is 15 to 30 gallons per person everyday |
| | | | for home use. The typical water tank is sized |
| When placed in low latitudes areas (below 40 | | | | to store a day's worth of use. So for a |
| degrees), solar water heating system can | | | | family with four members you could use an 80 |
| supply around 60 to 70% of domestic hot water | | | | gallon tank for everyday water requirements |
| consumption with temperatures up to 60 | | | | of 20 gallons a person per day. |
| °C. The most frequently used types of | | | | |
| solar water heaters are evacuated tube | | | | So when choosing a system you should first |
| collectors (44%), glazed flat plate | | | | analyze if freeze protection is required. If |
| collectors usually used for domestic hot | | | | the place you live is freeze-free, a batch |
| water (34%) and unglazed plastic collectors | | | | heater or a thermosiphon unit is sufficient. |
| largely used to heat swimming pools (21%). | | | | If you have larger needs, go in for open loop |
| | | | direct pump system circulating water from |
| Solar water heating systems are one of the | | | | storage tank to flat plat collector. If |
| most cost-effective utilization of solar | | | | freeze protection is required or the water is |
| energy which supplies hot water for domestic | | | | hard, you can go in for drain back or closed |
| use. Each year, more than a few thousands of | | | | loop systems with antifreeze and a heat |
| solar water heaters are being installed all | | | | exchanger. |
| over the world. | | | | |
| | | | There are different types of solar water |
| How it works | | | | heating models and systems available. When |
| | | | purchasing and installing a solar water |
| To use solar energy to heat water, a | | | | heating system you need to do the following: |
| collector needs to be fastened to the top of | | | | |
| a building or on a wall which faces the sun. | | | | Â- Consider the cost of a solar water |
| Collectors could also be free-standing. There | | | | heating system |
| are two types of solar water heating systems; | | | | |
| active that has circulating pumps and | | | | Â- Assess your location's solar resource |
| controls and passive that is driven by | | | | |
| natural convection. | | | | Â- Find the right system size |
| | | | |
| The collector can be made of a set of metal | | | | Â- Find out the system's energy efficiency |
| tubes surrounded by an evacuated glass | | | | |
| cylinder or a glass covered insulated box | | | | Â- Estimate and compare system costs |
| with a flat solar absorber made of metal | | | | |
| sheet which is attached to copper pipes and | | | | Â- Find out local conventions and |
| painted black. A solar water heating system | | | | regulations. |
| pumps cold water required to be heated to a | | | | |
| collector and the hot water flows back to a | | | | Installation and maintenance costs |
| collection tank. This type of system can | | | | |
| supply adequate hot water for an entire | | | | For installing solar heaters one has to take |
| family. | | | | into account the solar resource, climate, |
| | | | your building code and safety considerations. |
| The working fluid for the absorber could hot | | | | After the installation it is required to |
| water from the tank but usually it is a | | | | maintain your system well. Passive systems do |
| separate loop of fluid which has anti-freeze | | | | not need much maintenance. In active systems |
| and a corrosion inhibitor which provides heat | | | | the plumbing and other usual water heating |
| to the tank through a heat exchanger. Another | | | | components require the usual maintenance as |
| method is the 'drain-back' which does not | | | | regular systems. Maintenance is required for |
| require anti-freeze. Here the piping is | | | | every 3-5 years and the ones with electrical |
| sloped so that water is drained drain back to | | | | components need to have certain parts |
| the tank. The tank is open to atmospheric | | | | replaced after 10 years. |
| pressure. When the pump is switched off, the | | | | |
| water flow is reversed and the pipes drain | | | | The initial costs of a solar system if |
| off before freezing occurs. | | | | financed and evaluated with energy costs, |
| | | | then the monthly cost of solar heat will work |
| Central heating is required at night when | | | | out cheaper than most regular hot water |
| there is no sunlight and in the winter when | | | | heaters. Also, the federal and local |
| sunlight is limited. Water in the collector | | | | incentives are high. |
| could result in high temperatures when the | | | | |
| sunlight is good or if the pump fails. So it | | | | Summing up |
| becomes important to have designs that take | | | | |
| into account to provide relief of pressure | | | | Solar water heating systems are a highly |
| and excess heat with the help of a heat dump. | | | | cost-effective way to produce hot water for |
| | | | your house. They produce hot water in almost |
| Benefits | | | | climatic conditions and the only fuel they |
| | | | use is sunlight which is available free of |
| United States expends more than $13 billion | | | | charge. |
| every year on energy for domestic water | | | | |
| heating. It equals to almost 11.4 barrels of | | | | The total installed capacity of solar water |
| oil per household. | | | | heating systems as of 2007 is around 154 GW. |
| | | | China leads in the utilization of solar water |
| Solar water heating systems reduces the fuel | | | | heating systems with installed capacity of 70 |
| needed to heat water as the system uses the | | | | GW as of 2006 and a plan to achieve 210 GW by |
| sun's renewable energy. Solar water heating | | | | 2020. Israel leads in the per capita usage of |
| systems can also be used for car washes, | | | | solar water heating systems with almost 90% |
| hotels and motels, restaurants and swimming | | | | of homes using this system. In the United |
| pools. The advantages of solar water heating | | | | States, Canada and Australia, solar water |
| systems are the following: | | | | heating systems are largely used to heat |
| | | | swimming pools with the installed capacity of |
| Â- Reduces 80 to 95% of the water heating | | | | 18 GW as of 2005. |
| bill | | | | |