HIMHOT: Low-Cost Solar Water Heaters for Himalayan Region

A study carried out in 2011 initiated by the Global Solar Water Heating Project (GSWHP) of the United Nations Development Programme (UNDP) clearly stated the need for low-cost solar water heaters in the Himalayan Region. The GSWHP later used the study’s findings to organise a design competition with the aim to develop innovative low-cost solar water heaters suitable for this region. The requirements: the systems had to be light, modular, not require piped water supply and cost around INR 1,500 (approx. USD 300). One of the competition’s successful outcomes has been the HIMHOT, a storage collector with a transparent cover area of 0.5 m x 0.5 m. The photo shows the HIMHOT prototype being tested by a family in the northern Indian Himalayan region. The tests have shown that on a clear and sunny day, one unit can provide 25 litres of hot water with a ∆T of 25 to 30° per day.
Photo: Greentech Knowledge Solutions Private Ltd

The prototype development was a joint effort of SKM Design Pvt Ltd, a firm specialising in product design, and consulting company Greentech Knowledge Solutions Pvt Ltd. The prototype’s outer frame is made of stainless steel, the front glazing of a thin but tough and unbreakable polycarbonate sheet. The collector’s insulation consists of an Expanded Polystyrene (EPS) thermocole sheet. The dry weight of the system is close to 5 kg, and its design allows the HIMHOT owner to easily carry the collector by hand or on the back. HIMHOT can achieve temperatures of up to 70 °C. To have hot water in the afternoon, the user simply needs to fill the tank on the top of this ready-to-use system and keep the system directly in the sun. To prevent heat losses, he or she can fold the system or use the provided strap to lock it. The handle to lift the system also acts as a pivot stand.

The company manufactured a total of 40 units during the last 12 months in which the system was put to the test. Testing took place at more than 10 locations, including the Solar Energy Centres in the city of Gurgaon. The test results show that on clear sunny days, HIMHOT can provide an average ∆T of 25 to 30oC in three hours of solar radiation. A ∆T of 25 to 30oC means 25 litres of hot water (two batches a day) from a single unit.

Right now, the developers are optimising the product based on the users’ test experiences. They plan to have the system tested for commercial use in February 2013. The target market segments are "households (both rural and urban) in the hilly regions, across which hot water is required throughout the entire year because ambient temperatures are low, such as in the Himalayan region or in other hilly regions of peninsular India". Once the results of the commercial test are in, an advertisement campaign will try to reach all residents of the country’s mountainous regions.

This text was written by Jaideep Malaviya, an expert in solar thermal based in India (malaviya@solrico.com)

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