The differences in hot water demand between families living in the same solar-supplied multi-storey house has always been a source of complaints and disputes in India. A solution was found with the creation of a new hot water management system by Indian company Akson's Solar.
A multi-family house covering part of its hot water demand with a solar system usually has a central tank on its rooftop, from which the hot water is distributed into the flats. There has so far been no controlling unit measuring the hot water delivered to each family and often the over-use of hot water by one family resulted in a lack of hot water for other flats. Collector manufacturer and system designer Akson's has filled the gap by developing a programmable hot water distribution management system called »Delta«.
Delta measures the amount of hot water delivered to each flat and interrupts the hot water flow once it reaches the daily quantity allocated to each family within the building. The use of Delta requires individual hot water tanks in the bathroom of individual flats instead of the central hot water storage tanks on the roof top. At first the available hot water will be delivered in equal portions to each flat’s hot water tank and Delta records the quantity delivered. As soon as the sunlight heats the water in the collector again, the controller will calculate and deliver the missing quantity of water, in order to fulfil the family's daily supply. If any of the individual hot water tanks do not possess the capacity to store the entire or remaining quantity of hot water, the delivery is to be reserved as a »bonus« for later use on any other day in the future.
Delta delivers hot water at a fixed temperature. There is an electrical back up heater in the hot water tank, from which the hot water is distributed to each tap within the flat. The use of electrical hot water geysers is avoided. Whenever a tank reaches a minimum level of hot water, the controller unit is to open the cold water valve, start the electrical back up heater and provide a constant hot water flow without manual intervention.
So far, there has not been any competition to Akson’s water management unit for large solar thermal installations in multi-family houses in India. The new product has therefore sparked a great interest throughout the sector, as well as among ministry officials.
This text was written by Jaideep Malaviya, an expert in Solar Thermal based in India (firstname.lastname@example.org)