Solar Water Heater Advantages

We planned for water heater and installed the hot water piping for our new house during construction. But we didn’t know then, that it would cost us so little.After 3yrs, when we decided to have one, I searched the internet and found that among electric, gas geysers and solar heaters, Solar Water Heater (SWH) is the cheapest and best. I found that there are 2 basic models in SWHs. FPC(Flat Plate Collector) and ETC(Evacuated Tube Collector). Both of these models have a drum like water storage tank of 100 or 200 litres, with an inlet for cold water and outlet for hot water. At the bottom of the tank between the inlet and outlet are connected the solar heating devices (flat plate in FPC and evacuation tubes in ETC).

Water heating principle:In both these models you’ll have to feed these units with water coming from atleast 6ft above its storage tank. The cold water goes into its storage tank, as cold water is heavier descends down into the heating panels, gets heated up due to sun rays and as hot water is lighter it raises up and comes back to the same storage tank. This process goes on continuously until the sun shines. I mean to say that the cold and hot water gets mixed in the same storage tank. When hot water is used, same quantity of cold water replaces it in the tank. (So if more quantity of hot water is used up continuously after sunset, the cold water replacing it will take up the heat from the already hot water in the tank, and so reducing the temp of already hot water.)

FPC (Flat Plate Collector) is a model where the heating is done by one single solar plate facing the sun. Pros: Little lesser in cost compared to ETC. Cons: Heating efficiency is not as good as the ETC during rainy seasons or when sun is not so bright. In FPC, maximum absorption is during afternoon, bright sunny days (when sun rays fall exactly perpendicularly to the solar plate).

ETC (Evacuated Tube Collector) has 15 parallely placed cylindrical boro-silicate glass tubes in which water circulates down, gets heated and ascends up into storage tank. Pros: At any given time during the day, the sun rays are always perpendicular to the tubes circular surface. So maximum absorption of solar energy at all times. Sufficiently hot water even during cloudy, rainy days. Cons: Little costlier than FPC model.

A 100LPD(litres/day) is enough for a family of 4-5 members. Indian govt. provides 85% of the cost at 2% per annum interest rate. The most costliest thing in this setup is the hot water piping from your solar output in the terrace to your bathrooms in ground floor. If you have already done this, then there’s no reason for not going for SWH. I used Ashirwad PVC pipes.

Getting the loan: 100LPD unit costs Rs.19,500 and 200LPD unit costs Rs. 38,000. Canara, Syndicate, SBI, etc banks give 2% per annum loans. Check http://mnes.nic.in Even if you can afford, a clever fellow will avail the loan. Your SWH seller should arrange for the loan. But, now-a-days they don’t do so and advice to get the loan ourselves. As the interest incurred is so low, not many banks (even those mentioned on ‘mnes’ website) show interest to give this loan. But, if your seller provides it or if you could manage to get the loan from your bank, then you are done. Give the quotation to the bank, get the cheque for 85% cost, pay to SWH seller along with 15% cash, get the SWH unit. That’s it. Pay an EMI of ~Rs.600 for 100LPD or Rs.1200 for 200LPD units.

Advantages of two 100LPD units over one 200LPD unit: As you use the hot water, cold water gets into the SWH tank and mixes with already hot water, slightly reducing the heat. When, we use two 100LPD units connected in series to each other, the inlet of distal unit is the hot water outlet of the proximal unit. This way, the distal 100LPD unit will receive only hot water input, thus reducing the heat loss.

My Experience: As I availed loan, I opted for two 100LPD V-guard units connected in series, keeping in mind my growing family. The water is steaming. I’ll have to cover ¾ of the glass tubes during summer. Enjoy the feeling of steamy hot water during winter nights. One surprising experience is, at 10pm in the night when you go to have bath and find your hot water is empty, don’t panic, you don’t have to wait until the sunshine again, switch on your overhead tank motor, and you’ll get instant hot water. The hot water output stops, and seals itself, if it doesn’t get cold water input. So, when your overhead tank is empty, the hot water is locked and retained in SWH tank and opens up as soon as it gets the cold water input again on switching on the motor. The only maintainance you’ll have to do is clean the dust from the glass tubes occasionally.

There are many SWH providers, but most of them provide FTC models. I purchased V-guard ETC model from Hyderabad. Their representatives though couldn’t arrange the loan for me, but they were very professional and patiently explained me everything. My advice is “Go for it. Its really fit and forget instrument.” I am happy that I don’t have to trouble my mom in the kitchen busy making breakfast to share the gas stove for my hot water anymore. Moreover, each 100LPD will get a free electric heater coil installed into the storage tank. It acts as an electric back-up, just in case if its rains continuously for 2/3 days without sunshine (once in a blue moon situation)