Solar Hot Water System utilizes solar energy to heat water to the desired temprature. The heated water may be stored in insulated tanks for use in the morning or used during day time. The complete Solar Hot Water Tank, Circulation pump, Temperature Controller for the pump and instrumentation to measure water flow rates, quantity of water used, temperatures of hot and cold water, electrical energy consumed and cumulative time for which circulation pump runs. A typical Solar Hot Water System is schamatically.
A solar collector is a device which captures Solar Energy converte it into heat and used it to heat water. There are different designs of Solar Collector in use. The most commonly used design is of tube and fin type.
The sun-ray pass through the transparent glass and strike on the black surface of the absorber. The black coating on the absorber convert the radiation energy of sun-rays into heat. This heat is conducted to the tubes by fin which is made of copper or high conductivity material. The tube carry water which receives heat from the tube and becomes hot. To reduce the heat losses and thereby increase the efficiency of the solar collector, thermal insulation is provided at the back of the absorber.
The glass covers serves two main purpose. It reduces the effect of wind and heat losses, and protects the black coating on the absorber from the effects of weather, rain etc.
India in northern hemisphere, therefore maximum sunshine is captured by a surface facing South direction over the whole year. This is particularly so during winter.
For maximum efficiency, the sun-rays should Strike the collector at right angles.
For water heating applications, maximum output is required during winter when the sun is at lower altitudes. For maximum output therefore, the collectors should face south direction and be kept at an inclination equal to latitude of the place, which is around +15 to +20 degrees.
The capacity of a solar hot water system is specified is LPD. It is a short form for Liters Per Day. The intensity of Solar radiation varies through out the day, hence capacity cannot be specified in terms of hourly output.
To determine the capacity of the solar system required. first find out the hot water consumed during the day as well as during night, over 24 hours during winter season. the capacity of the solar hot water system in LPD should be equal to or grater than the hot water consumed during the 24 hours.
The water heated by the solar collector needs to be transferred to the insulated storage tank. when the heated water in transferred by means of a pump ( usually for large capacity systems ) it is called forced flow (FF) system. Most industrial systems are FF systems.
When circulation of heated water from collector to the storage tank is by means of the density difference between hot and clod water, it is called thermosyphon (TS) system. In this system the storage tank storage tank must be placed above the collector.
FTC means Fixed Temperature Control.
The operation of the circulation pump of forced flow system needs to be controlled to avoid pumping of cold water into the hot water storage tank. In FTC control, it is achieved by monitoring the temperature at the outlet of the collector. The pump is switched ON only when the outlet temperature is higher than the SET temperature. If the temperature falls below the SET temperature, the pump is automatically switched OFF.
Yes. The cold water is heated during the day & it is stored in an specially insulated storage tank all night, this insulation prevents the water from losing heat, so that you have piping hot water the next morning.
Yes ! The advantage of the solar hot water geyser is that you get hot water any time of the day or night, and irrespective of the fact whether there is electricity or not! This is true, but is limited to system capacity- the maximum quantity of hot water that can be utilised in a day will depend on the system capacity. If you withdraw more water than the rated capacity, then the water might not be hot enough.
India receives a clear and good sunshine almost throughout the year as it is close to the tropics. Even during winter the Solar Geyser works extremely well as it has been especially designed for maximum efficiency during the winter season. However during the monsoon season, depending on the hours of sun shine available, you may get varying degrees of warm water. NRG offers an optional electric heater installed within the solar geyser, to heat water during the rainy season, if you desire hotter water.
Electric geysers are usually set to 60 C, so you need to mix some cold water in geyser outlet water to make it suitable for bathing. It is almost the same with domestic solar water heating systems, the water temperature are generally about 60 C with an variation of about +/- 5 C, depending on season. So the Solar Geyser can adequately replace the electric geyser, plus save money on the electric bill.
Yes. Much higher temperatures are possible with the Solar Geyser, though the use is restricted to the industrial sector. NRG has designed many industrial systems with high temperatures such as 95 C for provided boiler feed water.
GEDA (a Govt organization) has calculated the cost benefits of a Solar Geyser, they are stated below:
The life-cycle cost of energy of saved electrical energy is Rs. 5600 per year at the point of end-user. If the SWH is purchased as an add-on to an existing geyser, the simple payback period for the consumer would be 5.45 years. If the SWH is purchased instead of a conventional geyser, the payback period for the consumer would reduce to 3.58 years
Most domestic Solar Geysers don’t require a lot of maintenance, as there are no moving parts in the solar geyser. The only maintenance needed is cleaning of the glass once a month for best results. And if you live in a hard water area, the descaling process once every year is recommended.
For Industrial systems, the pumps need to be inspected at frequent intervals, check for scaling and choking periodically and replacement of some parts of the control panel, as and when required.
NRG uses all Aluminium, Stainless Steel or Copper parts for the Solar Hot water systems manufactured by us, hence they usually last for about 15-20 years. Some maintenance may required periodically to get maximum efficiency like electric back-up etc. may need replacement. We have some of our very first Solar Geysers (manufactured 15-18 years ago!) still functioning properly to the great satisfaction of our customers.
Yes! The system can be designed into your house to fit unobtrusively on to a sloping roof, with a storage tank concealed, etc. This is best done, with the active involvement of your architect with our representative at the design stage itself, any modifications or changes later on are difficult to incorporate.
Yes, you will find advertisements of cheaper systems ranging from Rs.10,000 onwards. However, most of these systems do not use the high quality materials used by NRG (infact some use Plastic for heating water!!) and are therefore badly designed and less efficient. These systems do not provide 60 C temperatures like NRG Solar Geysers and more importantly do not last very long.
NRG SPV systems use CFL (Compact Fluorescent Lamp) lamps. They are used as they consume 70 – 80 % less energy than ordinary incandescent bulbs and the CFL light output of 5, 7, 9 & 11 watts is comparable to 25, 40, 60 & 75 watts ordinary bulb respectively.
The number of operating hours depends upon SPV model & quantity of CFL’s used with it. In general, the systems are so designed so as to be able to run each CFL lamp for around 3 hours daily.
There are different SPV systems available, from the Solar lantern to Home lighting to Solar Power Pack, each with further individual configurations. So depending on the configuration you choose, the number of CFL lamps, DC fans etc will vary.
Yes. NRG offers the Solar Power Pack. This can be used to run a part of your house exclusively on Solar Energy. But these appliances consume more power so the number of solar modules, batteries etc. required is much larger, thus making the total cost of such a system substantially high.
SPV systems generate electricity even in cloudy weather, though their output is reduced. SPV needs just the sunlight and not the heat from the sun, therefore the system even can work in rainy season i.e. in diffused light conditions, as well as in winter. Thus in a country like India the SPV system function throughout the year.
Maintenance required is minimum and is restricted to checking the water level in battery after every few months and maintaining the water level by adding distilled water. Cleaning the glass surface of the solar module with the water and soft cloth periodically to remove dust is also helpful.
Solar PV Module : 25 years CFL Lamps : 5-10 years Charge Controllers : 5-10 years
The main cost in solar lighting system is due to the solar module. The manufacturing process of solar cell is a complicated & expensive procedure. This pushes up the overall cost of solar lighting system.