- JAIDEEP N MALAVIYA

The benefits of Solar Water Heater (SWH) are hardly noticed and there is absolute lack of awareness among masses on the potential of this solar energy technology.

Ever since the National Solar Mission was launched in January 2010 solar energy has been the centre stage and brought India on the global map as one of the few national progressing solar energy developments. The target then set was 22 GW of all solar photovoltaics (PV) power generation and 20 million m² of solar water heater (SWH) collector area spread over 3 phases that end by the year 2022. Phase I that ended in March 2013 and supposed to be a trigger with a mild target was well achieved, with solar thermal even surpassing the target.

Presently the installed solar capacity in India is nearly 3,500 MW of solar PV and close to 9 million m² of solar thermal collector. The recently concluded RE-INVEST event received roaring response to India’s renewable energy commitments of over 175,000 MW, with solar energy capturing the lion’s share of 100,000 MW. The National Solar Mission target for solar PV now stands revised to 100 GW, to be achieved by 2022.

It is often noticed that solar thermal rarely gets any attention in all solar energy related announcements despite the fact that India is now the world’s third largest developing SWH market after China and Turkey, as per a study conducted by solrico, Germany. Fig. 1 below shows the growth of solar thermal in India.

One prominent difference between a solar PV and a solar thermal system is that the former generates power while the latter saves power. Often any renewable energy is seen as energy producing technology hence it is anticipated that this could be the reason for solar thermal not getting due attention. The Ministry of New and Renewable Energy has even withdrawn the subsidy on SWH in August 2014, but that has not hampered the market growth and the demand in fact continues to grow steadily.

Each square metre of SWH saves annually about 600 kWh of power assuming 200 days of operation and generating hot water temperature @ 60oC. For the same 1 m2 area a solar PV system will generate 150 kWh at 15% conversion efficiency. What is noteworthy here is that for a given area, SWH is nearly 4 times as efficient as solar PV. This statement should however not be seen as negating the use of solar PV, rather solar thermal should receive equal respect.

According to the 2011 census report there are close to 7.6 crore urban houses and 16 crore rural houses. Of these 96% of urban houses and 78% of rural houses have permanent roof structures and are potential customers for any SWH. It is assumed that each of these houses uses hot water for varied applications. Considering 20% of urban households and 2% of rural households as present target potential each using a SWH of 2 m2 collector area, the net potential comes to 3.65 crore m2. The ultimate target that can be assumed is 100% of urban households and 50% of rural households, which is close to 40 crore square metres. It is also noteworthy that the roofs, which use hot water for commercial and industrial applications, have not been considered and is another potential zone.

The government can easily consider revising the solar collector area target under National Solar Mission to 40 million m2 from the existing 20 million m2 until 2022.

Each square metre SWH collector generating hot water at 60oC substitutes a typical 1.5 kW electrical heater at any given time. The 3.65 crore m2 SWH area active on any given day thus reduces the electrical heating demand by almost 55,000 MW. For every m2 the daily electricity saved is about 2.5 kWh. Thus on any normal sunny day the energy saved by the 3.65 crore m2 SWH collector area works out to 2,190 crore kWh (units). Each kg of coal produces close to 4 kWh. Thus the amount of coal saved daily will be 55 lakh tonnes (2190 crore/4).

The present cost of SWH is typically around Rs 7,500 per m² and pays back within 3 years, assuming cost of electricity at ` 4/kWh for residential use.

The government should include this inexpensive source of solar energy in all its future planning and targets and initiate a national movement by involving Municipal Corporations for mandatory use in all buildings. Most essentially electric utility companies should extend electricity rebates as it enables them save their coal and also helps in reducing their peak demand and hence avoid setting up of additional power plants.

The benefits of SWH are hardly noticed and there is absolute lack of awareness among masses on the potential this solar energy technology.

(The author is Secretary General, Solar Thermal Federation of India. National Solar Energy Helpline 1800 2334477)