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