Everyone of the above choices is a big ticket expense. The way, cement, steel and plastic tanks are priced today, creating 30,000 litres elevated storages is unaffordably expensive. Their environmental costs in cement, steel and plastic is another matter altogether. That’s when an out of the box solution occurred to me.
There is a modest solar electric system at pointReturn now. I can run a small -up to say 1/4HP or 250 watts- electric pump, totally free, on solar energy. So why not, place heavy, lower cost storage tanks at ground level near the strongRoom and let the overflow from the existing OHT collect into these. Then whenever the OHT runs low, a small pump can lift it back into the OHT at no energy cost.
Cost of on-ground tanks are dramatically lower than above-ground ones. There is a wider choice in the type of tank: plastic, ferrocement, hole in the ground, discarded truck tanks etc. Serendipitously, I had been interacting with a potter in the nearby village of Dargas. This village once famous for a whole street of potters is now diminished to just two households. I have been working with Ramalingham and his wife to create a number of artifacts out of terracotta.
“What is the largest sized tank you can build,” I asked him. “I can build fairly large ones but they will be three parts that you’d have to cement together onsite,” he said. he held out his hands apart and then raised a palm to indicate the diameter and height of the tank. A quick calculation told me they’d be 1,000 litres each.
I don’t lack for space; 30 tanks on the ground can in fact be placed with dramatic effort. The cost would be decidedly lower. There could be a small revival in the potter’s business. Energy consumed in creating the tankage will be minimal and hardly aggravate the planet’s condition. That is the route I shall take; my elation can be inferred.
But a few caveats emerged. Ramalingham counseled caution: “I have not built one in a long, long time; it’s possible the three parts might distort after firing and not fit snug. So let’s hasten slowly with a few trial pieces.” Then there was the issue of the coming rains when he cannot gather clay from the lake bed. So the first piece is at least three months away but it is firmly on the agenda.
Meanwhile I can’t afford the water go waste. So to plug the problem in hurry, I bought a 6,000 litre LLDP tank that cost Rs.22,000. It stands 7′ tall. The top of the OHT is about 12′. The height to which the small pump has to lift is therefore modest- between 5′ and 8′. I shall live with this arrangement till we develop terracotta tanks.
There is another tweak that I have put in place. The windmill is about 200′ away from the OHT. The mill raises water up in a stand pipe that is taller than the height at which the OHT are – but just about. Theoretically, water must flow from the higher lever in the mill’s stand pipe to the OHT. When the mill turns over slowly, the pumping rate is low and the water flows without problem. However at moderate winds, when water is pumped at a greater rate, the stand pipe is not evacuated fast enough. A back pressure builds up that causes the stand pipe to wastefully spill a lot of water around the windmill tower’s foot. Last fortnight, this problem was rectified by adding an extra 12′ to the stand pipe’s height.