Solar water heaters make use of the solar energy to generate hot water. Solar water heaters find their use in a number of applications ranging from home, industrial and business uses.
Solar water heaters can be used in Bungalows and apartments. Commercially they can find their use in hotels, Dormitories and hospitals. Solar water heater can provide for the large scale demand of hot water required in industries like process industries etc. Solar water heaters can be used for heating swimming pools and a solar water heating system can also be used in solar thermal cooling system to promote temperature control in buildings. During cool conditions the system can be used to provide hot water.
Solar water heater designs vary, and the complexity of the design and its type is determined mostly by a number of factors such as the ambient temperature change that take place during night and day cycle, changes in solar radiation and ambient temperature between winter and summer and the water temperature required. Performance of the solar water heater differs from site to site depending upon the level of solar energy available at the place.
The minimum efficiency of the solar water heater is measured by the temperature or the amount of hot water required during the months of winter when the requirement of the hot water is largest. Similarly the maximum efficiency of the solar water heater is measured by the necessity to prevent the water from becoming excessively hot.
Solar water heater systems are usually have solar thermal collectors, interconnecting pipes, a water storage tank and fluid system that transfers the heat to the tank from the collectors. The thermodynamic mechanism used here is different from semiconductor photovoltaic cells which use light to generate electricity, whereas here the process comprises of heating the liquid directly by the sun and there is no generation of electricity.
There can be broadly two types of solar water heaters namely- active and passive.
Passive solar water heaters
Passive systems do not use a pump and use heat pipes for circulation. Integrated Collector Storage is a special type. Here the tank provides for both-as the solar collector as well as the storage. These are usually not pressurized and hence flow depends on the gravity. These have a glass in the front. Passive systems are efficient and simple and less expensive but are suitable for moderate climates only.
Convection Heat Storage unit is another type of passive system which is a level up from the Integrated Collector storage. These are usually evacuated tube collectors or the plate type and have a built-in insulated tank. Convention is used for the movement of water. The advantage of this over Integrated Collector storage is that it can be used with less sunshine as it is more efficient.
Passive systems can also be classified as the direct and indirect passive systems.
In direct i.e. open loop passive system the water circulates between storage and collector tank. The water in the collector rises and flows to the storage due to convention as soon as it becomes warm. However these types are not suitable in cold climates because if the water in the collector freezes at night then it can damage the panels.
In Indirect or closed loop passive system an antifreeze heat transfer fluid (HTF) is used which is non toxic. Once this fluid gets heated, it flows to the tank due to convection. The heat of the HCF is transferred to the water by a passive heat exchanger.
Passive solar water heaters require very less maintenance as they are quite simple and do not have complicated electrical or mechanical parts. However the efficiency of passive heaters is also lower than that of the active heaters. Overheating is generally prevented here.
Active solar water heaters
Active solar water heaters make use of a pump for the circulation of the water. These are again classified into two types: direct and indirect active systems.
Direct systems directly pump water to the collector and storage tank, while the indirect ones use heat transfer fluid. A controller is needed here to turn the pump on and off because the pump should operate only when the fluid present in the collector becomes hotter than the water present in the storage tank.
The advantage of electronically controlled pump is that the storage tank can be located lower than collector which is not feasible in the passive systems. The freedom of location of storage tank enables it to be located at a place where the heat loss is minimized. The pump controllers also prevent overheating. Hot water is pumped through the collector which is cold in night, thus avoiding overheating. Similarly water from the storage tank can be pumped through the collector during cold weather to prevent freezing.
The advantage of active water heater systems is that they can tolerate higher temperatures and therefore are more efficient then passive heaters. But they are more expensive as well as more complex than the passive heater systems. Moreover they have to rely on electricity in order to run the controller and the pump.
Modern active solar water heaters have intelligent controllers to allow a range of different functions.
During good sunshine the water in the collector can attain very high temperatures. Therefore solar water heater designs should be such that allow excessive pressure and excess heat to be relieved through a heat dump.
Similarly in order to prevent damage due to freezing, freeze protection measures must be included. To ensure that there is no damage due to expansion of transfer fluid due to freezing some systems use drain back and drain down measures that is they drain he fluid if the pump stops, while others use anti freeze.
Cost of the solar water heater systems
In places where there is no need for freeze protection an ICS solar water heater can prove to be extremely cost effective. At higher latitudes the initial cost increases due to complexity of the design, but not the life cycle cost. Since the solar energy is free, the operating cost is significantly reduced in comparison with other energy sources.
The solar energy has various benefits because of which it has become next big thing as far as energy resources are concerned. Solar energy is available in abundance and that too free of cost making it cost efficient. After the initial investment which is a little high but is recovered very soon there is no other cost involved. Solar energy is a clean source of energy. It does not result in production of any harmful gases which further cause SMOG, acid rain or other greenhouse effects. Solar energy is better than nuclear power also because no there is no danger of radiations involved. Moreover it is available in abundance and everywhere. Energy of sun is there free of cost for everyone on earth without the worries of depletion as is the case with other non renewable sources.
Solar energy is renewable source of energy which is available as and when required so no hassles of storage or transportation of any fuel etc. Solar energy is considered a clean fuel as it does not emit any harmful gases or by products hence is environment friendly and does not contribute to today’s main environment concern “global warming”. It is easy to install also as not much wiring is needed in the process. Solar energy reduces noise pollution also along with air and water pollution. Solar panels do not make even a peep sound as compared to noise made by big drilling machines and gensets. Air is clean and no harmful gases are produced in any way using solar technology. No residue is produced which will result in polluting our environment in any way. So there is no health hazards involved in using solar technology. Dependency on grids reduces by using solar technology and consumer can become independent and can even sell back extra energy produced.
We have other renewable sources of energy also but solar energy is first in the race. There are several reasons to it. We have energy by water- Hydro energy but it results in soil erosion and degradation in long run causing other concerns. Then we have wind energy but it is highly uncertain so a consumer cannot totally depend on it.
Using solar energy for your home can increase the value of your home also as people like to spend money on homes which are energy independent as this can result in saving power bills and helps saving the environment too. Storing solar energy is much easier than storing oil and gas which can result in leaking oil tanks and exploding gas tanks.
Since the solar systems are simple and smart a person can self install them without much problem. And since these systems are modular they can be easily upgraded and adjusted any time without much effort. Maintaining solar panel system is easy as the parts are not movable and no parts which cause wear and tear.
Countries are trying to control emission rates of industries so in western countries they have made pollution credits. If one industry is using the power of solar energy it can save its credits and can further sell it other industries and thereby generating profits. So solar energy along with making industries independent can help them generate some profit too and this thing is called emission trading. New technologies are being developed and this would help generate new job opportunities also in coming times so solar energy would also bring about various infrastructural gains to people involved.
Solar energy can be used as an independent source or along with other conventional sources of energy. It does not involve any reoccurring cost hence it can be easily maintained and you can increase your consumption whenever you want by just adding extra solar panels. Moreover you get various grants, rebates and tax exemptions for using solar energy by government. So all in all solar energy has so many benefits that in coming years its use is expected to rise exponentially.
So we have seen the benefits of solar energy. Since our future lies with this energy resource so it is the need of the hour that we start shifting our focus towards it and stop all the environmental disasters that are happening and make earth a cleaner and greener space for our coming generations.
Solar energy can be utilized using two technologies – thermal and photovoltaic. Thermal solar power harnesses heat of sun directly like solar cooker etc and photovoltaic cell converts light into electricity or DC current. PV cell does not require direct sunlight so it can work in light cloudy conditions also. This technology was developed by NASA scientists in 1958 for their spacecrafts. A photovoltaic cell consists of layers of fine silicon wafers. When sunlight falls on these layers an electric field is generated across the layers and this result in flow of electricity. Semiconductors like silicon are used because they have a property of releasing electrons when solar energy falls on them, helping electrons to circulate and generate electricity.
When these photovoltaic cells are connected together they form a solar panel. PV solar panels come in mono crystalline, poly crystalline, amorphous and thin – film varieties. These solar panels are connected together in an array to produce electricity to do various things like heating water, generating light using solar lanterns and pumping water etc. The average lifetime of a PV panel system is approximately 20 years and it can be used independently or along with other conventional power sources. One should try to avoid any harm to solar panels to ensure its long life. Solar panels are usually covered with glass to avoid any moisture reaching parts of it and causing any harm.
Solar panels can be used to light up both interiors and exteriors of the house. One can use solar panels to light up their garden and drive way outside the house or use solar power to light up and heat up inside of any house. Solar panels can be used for sun bricks, solar powered security cameras, air crafts using solar energy, solar powered watches and phones etc.
Solar panels require proper maintenance else they wear out very soon. They should be kept away from any harm because if any harm is caused to the PV cells inside the panel it becomes useless.
Because of new technologies found by our researchers size and cost of PV cell has reduced drastically in recent years. Japan has invented a PV cell so thin that it can be used under clothing also. New technology of printable panels is also coming up in which these panels can be printed or coated directly on the surface exposed to sunlight.
The demand for solar panels is increasing in India because India receives plentiful solar radiations in its vast arid land areas. Moreover there are vast rural areas in India where the cost of providing conventional sources of energy is quite high so solar energy is a boon in these areas. According to Indian Meteorological Department states of Rajasthan and Gujrat receive maximum annual global radiations. Since large parts of Rajasthan are barren and scarcely populated central government has thought of setting huge solar power stations there. Depletion of fossil fuels and need for pollution free energy resource has made India recognize solar energy as its next big energy resource.