Solar power: can it out-perform diesel when pumping water?

Innovation, Water

Brian McSorley on an Oxfam solar water pumping programme in arid northern Kenya that is testing – and sometimes overturning – assumptions about solar power, and finding that for many communities, it beats using diesel.

In Turkana many communities have required significant external support during previous droughts, to ensure critical dry season water points remain functional to minimise loss of life – of both people and animals.

Diesel systems are capable of very high output, but their fuel consumption means very high operational costs too. In droughts they might need to operate for 18 hours a day to keep people and animals alive. But the Catch-22 is that just when people need water the most, they are least able to afford to operate diesel pumps. As the economy contracts they lack the money needed to buy the fuel. Operation becomes intermittent. Generally, too, many diesel pumps have exceeded their original design life and are poorly maintained; their failure rate is high. If governments or NGOs provide fuel
to subsidise the costs of operation, and spare parts, it reinforces a sense of dependency and fails to address the underlying economic and management issues.

Oxfam is implementing a Drought Management Initiative with funding from the European Commission, and as part of this, we have installed eight solar pumping systems in seven villages. Five of these replaced diesel, enabling us to make direct comparisons.

The seven communities all report significant benefits as a result of using solar water systems. The most important are improved access to water and reliability of supply. The tangible evidence of this is that during the 2011 drought, widely reported as the worst in 60 years, all these villages were self-reliant in terms of water supply, and were even able to set up small irrigated plots.

For example, the community of Meyan was previously dependent on traditional scoop holes, which were unsafe not only because of waterborne diseases but also physically dangerous as sometimes they collapsed, burying and killing people as they collected water. The solar pump has provided this village with a continuous water supply which people have used to start kitchen gardens and cook food. The community reports that there is less illness and above all, they value the fact that they can still get a water supply during periods when it is difficult to collect tariffs for fuel.

Two frequent assumptions about the supposed inadequacies of solar power have particularly been challenged by this experience. One is that the output of a solar pump would not be able to meet demand. In fact, due to improved continuity and reliability, the actual net output from the solar systems is significantly greater than that of diesel systems. The second is that the capital cost of solar is significantly more expensive than diesel. This is not so. Solar pumps tend to replace larger capacity submersible pumps and generators of comparable or greater cost. This is the result of a
common tendency to oversize generators and pumps, a “bigger is better” mentality which persists even within District Water Offices (and the agencies who supply the equipment).

And as expected, the solar pump has significantly lower operating costs. As the Chairperson of Kaaleng Water User Association said: “We never used to have any savings before; since the installation of a solar pump, we’ve been able to save 11,000 Kenyan Shillings (approximately 1,000 Euros) and paid all the debts.”

There are some challenges with the new solar pumps. The main constraint is that they cannot pump a sufficient quantity of water from deep boreholes. Output also drops significantly in cloudy conditions, and there is none at all at night. However, this is easily overcome by having a small back-up petrol generator (which each village has). The Turkana environment is ideally suited to solar, with ample sunshine and fairly shallow groundwater depth. In other places with higher demand and/or deeper groundwater, solar may not be appropriate. Nevertheless, Oxfam’s experience in Turkana
demonstrates that solar is simpler and more reliable and a big step in the right direction in terms of increasing the level of self-reliance of communities during dry seasons and drought, and reducing the level of external support.

Author: Brian McSorley
Archive blog. Originally posted on Oxfam Policy & Practice.