Designing for Sustainability: Solar Water Pumps

As mentioned in the article, why hand pumps are unsustainable, hand pumps are the most preferred solutions for water supply in areas without both water and electricity namely: developing countries.

At the heart of it, is the fact that hand pumps are cheap and can be easily fabricated in any country. Given that most international development organizations do have limited funds, this fits their budget. Local residents can also be trained to maintain the system. This looks good in theory but in action it leads to broken pumps after one year(without maintenance) and a recurring water problem! This is unsustainable.

If hand pumps are not sustainable which water solution is?

Conversely, Solar water pumps use free sunshine to generate energy. Solar panels trap this energy and convert it to DC power which is then used to run the DC motor in the pump. A solar water pump is simple a solar panel connected to a DC pump. Each panel has a warranty of 20-25 years and most submersible pumps have a warranty of 10 years. Since the process is automatic, no human energy needs to be expended to collect water.

Instead the water is pumped to an overhead tank and then it flows through gravity to wherever the user may please. Unlike hand pumps, solar water pumps do not corrode because they are often made from stainless steel. Therefore they do not contaminate the quality of water pumped. As far as maintenance is concerned, a general wiping of the panel is required to remove dust that causes shading and cleaning debris from the pump suction pores.

The economic case for Solar water pumps

So the only question that remains is: what is the price? Can the solar water pump compete at the same level with hand pump? The answer is an equivocal yes. According to Bloomberg New Energy Finance, the levelized cost of electricity(LCOE) from solar PV, which is now almost a quarter of what it was just in 2009, is set to drop another 66% by 2040.This is best exemplified by a solar panel in Kenya that costs £50 for 144Wp. A DC submersible pump with a head of 30m and a rating of 144W costs £150. Without installation but including shipping brings the cost of this solar water pump to £200. With installation factored in, the cost could go up to £350 depending on distance to installation site. From the cost perspective, solar water pumps are at the same level with hand pumps. By reducing the cost of SWP's by 90%, Sustainable Water wants to make sure solar water pumps are affordable to everyone in developing countries.i.e farmers,pastrolists,schools.

Why do most water charities and international aid organizations opt for the handpump?

Simply because it is the done thing. The truth is that most organizations do not have a member of the community present when they are planning these solutions. So they never get user feedback on the solutions proposed. Once the hand pumps are installed, few organizations have maintenance in mind. So when they break down, the problem recurs. I believe the only way to get this right is by designing with sustainability in mind.

Asheim said’ Development is only sustainable if is ensures a continuous/increasing quality of life. The hand pump fails this test every single time it breaks down because it decreases the quality of life. A solar water pump has little to no maintenance costs associated with it. It has a lifetime of 20 years and uses sunshine which is free. Hand pumps are mechanical needing human energy to pump water. They are also limited in head as they are surface suction pumps.

For charities, it is worth considering how our actions might affect the recipient. Is the purpose of our aid for relief, rehabilitation or development? Relief is temporary and immediately in response to a crisis. Rehabilitation is restoring people back to where they were before the crisis hit. Development is moving people beyond where they were.

SDG 6 and solar water pumps

Why should we keep doing the same thing over and over again and expecting different results? Put more aptly, how are we to achieve SDG6 by 2030 if we keep losing half of the water pumps/ solutions installed? It is akin to filling a water tank that loses half the water once we pour it in.

By using solar water pumps we can secure water supply for the next 25 years!

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Ingenuity Lab, Ingenuity Centre
University of Nottingham, Nottingham, NG7 2TU