SOLAR POWER HOT WATER   

Introduction: 

  Solar power  hot 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 power hot 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 power hot 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 Solar Power Hot Water 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, closed loop ststem that has circulating pumps and controls and passive that is driven by natural convection.

Example Of Active, Closed Loop Solar Heating System:

Example Of Passive, Batch Solar Heating System:

  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.