Water Heating through Solar Thermal Collection Process

Engr. Dr. Muhammad Nawaz Iqbal

A solar-oriented gatherer warms a functioning liquid that passes into a capacity framework for some time later use. SWH are dynamic pumped and detached convection-driven. They use water just, or both water and a functioning liquid. They are warmed straightforwardly or by means of light-concentrating mirrors. They work autonomously or as cross breeds with electric or gas radiators. Whenever no boiling water has been utilized for a little while, the liquid in the authorities and capacity can arrive at high temperatures in all non-drain back frameworks. At the point when the capacity tank in a drain back framework arrives at its ideal temperature, the siphons quit, finishing the warming system and in this way forestalling the capacity tank from overheating. Simple plans incorporate a basic glass-finished off protected box with a level solar based safeguard made of sheet metal, joined to copper heat exchanger lines and dull hued, or a bunch of metal cylinders encompassed by a cleared (close to vacuum) glass chamber. In modern cases an allegorical mirror can focus daylight on the cylinder. Heat is put away in a hot water stockpiling tank. The volume of this tank should be bigger with sun powered warming frameworks to make up for awful climate and on the grounds that the ideal last temperature for the solar based authority is lower than a common submersion or ignition radiator. Private solar based warm installations fall into two gatherings: inactive usually called smaller and dynamic usually called pumped frameworks. Both normally incorporate an assistant energy source (electric warming component or association with a gas or fuel oil focal warming framework) that is initiated when the water in the tank falls under a base temperature setting, guaranteeing that heated water is accessible 100% of the time. Whenever a solar based water warming and high temp water focal warming framework are utilized together, sun powered hotness will either be gathered in a pre-warming tank that feeds into the tank warmed by the focal warming, or the solar oriented hotness exchanger will supplant the lower warming component and the upper component will stay to accommodate supplemental hotness. Heat is transferred from the “heat-transfer fluid” (HTF) fluid to the potable water in indirect or closed loop systems using a heat exchanger. The most common HTF is a mixture of antifreeze and water that contains non-toxic propylene glycol.

A drain back system is an active indirect system in which a pump circulates the HTF (typically pure water) via the collector. The collector plumbing is not pressured, and it contains an open drain back reservoir in conditioned or semi-conditioned area. Unless the pump is running, the HTF stays in the drain back reservoir, and when the pump is turned off, it returns there (emptying the collector).

Flat plate heat loss can be reduced by using evacuated tube collectors (ETC). Convectional heat loss cannot traverse a vacuum, hence it serves as an effective isolation device to maintain heat within the collection pipes. The vacuum is formed between two concentric tubes because two flat glass sheets are usually not robust enough to endure a vacuum. The water piping in an ETC is typically encircled by two concentric glass tubes separated by a vacuum that allows heat from the sun to enter (to heat the pipe) while limiting heat loss. A thermal absorber has been applied to the inner tube.

By thermally insulating the tank, ICS or batch collectors prevent heat loss.  This is accomplished by encasing the water tank in a glass-topped box that allows the sun’s heat to reach it. The box’s other walls are thermally insulated, which reduces convection and radiation. On the inside, the box might also have a reflective surface. This reflects heat back into the tank that has been lost. The amount of heat produced by a solar water heating system is mostly determined by the amount of heat produced by the sun at a given location (insolation). Insolation in the tropics can be rather high, up to 7 kWh/m2 per day, compared to 3.2 kWh/m2 per day in temperate zones. Due to changes in local weather patterns and the quantity of overcast, even at the same latitude, average insolation can vary greatly from location to location.