No water for a solar system

The closing event of the Science Gallery’s Surface Tension: The Future of Water took place last night. As the curtains are closed on this wonderful show, I interviewed Joanne Mac Mahon whose PhD research featured in the exhibition. Mac Mahon is part of a team in the Department of Civil, Structural and Environmental Engineering in TCD. Over the past ten years, they’ve developed a water disinfection system that uses sunlight to clean water.

It has long been recognized that a local source of clean water is essential to enable development. Not only does it prevent water-borne diseases but the time saved hauling water allows people to improve their skills and attend school. Africa has one plentiful resource, sunlight, which has been exploited by the Trinity team. The system they have developed is a set of clear pipes on a reflective surface. The water is fed through them by gravity and the UV radiation from sunlight is used to kill any bacteria and viruses present. Tanks are used to store the clean water once it has been fed through the pipes.

Installing the system in Ndulyani (2008)

Mac Mahon explained that the current recommended solar disinfection system can only be used at a household level. Families place clear 2L bottles of water on their roofs for 6 hours (without clouds) and wallah… pathogen-free water. So what does the Trinity intense-sunbed-style system offer? It takes the hassle from each household as it disinfects water continuously and can supply a community. The simplicity of the materials and lack of need for electricity and chemicals enables it to be used in rural areas of Africa. A 2008 pilot in a rural village, Ndulyani, in Kenya showed that it served more than the immediate village: “People were coming further afield to collect water. Up to 1,000 people were using it”. 

When Mac Mahon went to Kenya this summer to check how the pilot system was doing, she didn’t know what to expect. Unfortunately the solar disinfection system had stopped working but it wasn’t for any reason she had predicted. After almost 4 years of no rain, the water source had dried up completely. “I didn’t expect no water. There was nothing we could do when the water system had dried up”. It was not all negative news as the system had worked for over a year and the villagers were very positive about it.

Dam in Ndulyani 2008 (top) & dried up in 2011 due to prolonged drought (bottom)

Mac Mahon is determined to continue the pilot by installing a bore hole. This will be used as a back-up supply during times like the current drought. Water can be pumped up to storage tanks and fed by gravity into the solar disinfection system already installed. I wondered why water from a bore hole would need to be disinfected but Mac Mahon stated that they “were not sure of the quality of water from the bore hole and there is a history of water being contaminated”. The Trinity team is currently trying to raise funds to complete this part of the project. They need a whopping €22,000 and hope to achieve this on Fund-It over the next four weeks. Watch the video below for more information.

Sustainability always springs to mind when discussing projects like this. I have written previously about the Play Pump, a project that received abundance of support but upon evaluation showed to be more work for the villagers than a standard bore pump. Monitored pilots such as this one in Ndulyani are important to ensure projects are sustainable and feedback is received before large-scale implementation.

Finally, I was curious to know what had driven Mac Mahon to work on this African project. She has an engineering background and had completed aid work for a number of years. Missing engineering, she went back to college and this project came up. “For me, it was the perfect way to blend engineering with the development work that I had done”.

So as the exhibits in Surface Tension: The Future of Water are packed away, the projects they represent are not in bubble-wrap beside them. Talking to MacMahon reminded me that this exhibition wasn’t about facts, figures or fun things to see. Don’t let it be out of sight, out of mind!

Images: Courtesy of Trinity College Dublin

2 thoughts on “No water for a solar system

  1. Hi Maria, thanks for the great post. It really brought home to me that safe drinking water is a basic human right and not a privilege. This is where technology, science and strong leadership can really make a difference and I want to wish the best of luck to Joanne and the team over the next four weeks.

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