Clean Cool Water in a Dry Place
I am sitting on a flat rock under a tree in rural Uttar Pradesh, several kilometers outside of Jhansi. All around us the ground is dry and parched and the weather resembles being inside an oven – dry and hot, but there is a little green patch in front of me, where vegetables are growing with a vengeance. I watch as cold clear water flows into the field, and Chanda, the land’s farmer, carefully and meticulously channels the water into each section of the small plot. Onions, tomatoes, eggplant, chilies, each get their turn to be soaked. I remove my sandals and dip my feet into the water, in an effort to cool myself down a little.
This cool clear water comes from an open well a few dozen meters from the vegetable patch. That is the reason we are here. As part of the ongoing CITE evaluation of solar pumps, the team is visiting Chanda’s farm to evalutate not only the pump’s technical performance, but also to discover how it has impacted her life. Chanda is using a solar irrigation pump installed by Punchline Energy, facilitated by the NGO Development Alternatives, and funded through a grant from the Coca-Cola Foundation. She shares the pump with three other farmers on small plots, and although her vegetables are currently only sold at the local market, she will be sowing lentils in the next field over which she will sell as a summer crop to the wholesaler in June.
These summer crops would not be possible without irrigation in a year of good rains, and to put it mildly, the last few years have not been good to the area around Jhansi. This area normally gets upward of 750mm of water each year, but for the last three years, the rainfall has been between 250-300mm. The resulting drought has meant that even farmers with access to wells and pumps have been unable to irrigate, as many of their wells have gone dry. Chanda’s farm, in a location on the downward side of a water channel, has not yet had any problems with the well. To say she is grateful for the water is an understatement. Others are not so lucky and many have had to move to the cities to find other means of supporting their families.
Chanda’s solar irrigation pump is one of six installed by Development Alternatives around the end of 2014 and beginning of 2015. Of these six, four are not functioning properly due to a lack of water in the wells. Two of these function for only a few minutes at a time before the well empties. The remaining two aren’t in use at all because the wells are completely dry.
This highlights one of the problems in pump sizing, which is particularly important for solar pumps. Agricultural wells are tricky business, I am finding. My childhood wishing well understanding of a deep dark hole perpetually filled with water doesn’t, well, hold water. Well depths are constant at the depth to which they have been dug, either by hand or with a boring machine. However, water levels can fluctuate greatly depending on rainfall patterns, irrigation usage, nearby reservoir and channel construction, and local water recharge initiatives. The size of the pump should take into account the water requirement, the recharge rate of water into the well, and the pump head, or pumping depth. Often, pumps are intentionally oversized in order to remove the maximum water in minimum time.
With solar pumps, this has an important impact on capital cost. Solar panels in a solar irrigation system are sized depending on the required power to the pump. A larger pump requires a larger array with more panels, which are by far the most expensive component of the system. “Right-sizing” the pump not only increases the efficiency of the well, it can also greatly reduce the cost of the system as a whole by decreasing the number of panels necessary to make the pump function.
We measure flow-rate and water drawdown from the well as well as the current produced by the panels. This information will be used in our analysis of this system against the others that we are visiting during our tour of India this summer.
The system installed for Chanda’s farm is mostly likely oversized – a 3HP pump for a 30ft well gets water out quickly, but it also drains the well dry. As a result, the panels required are much too large and the cost of the system is quite high – 2.5 lakh rupees, or about $3750. Chanda and two other farmers pay a total of Rs. 36,000 per year, which means her panels will be repaid in about 7 years. This is possible because with the water she gets from the solar pump, she increases her income by cultivated crops in season she wouldn’t have otherwise. Because a grant has been used to purchase her pump, the money she repays goes into a fund to provide solar pumps to other farmers belonging to her cooperative.