The overlap between the groups living with neither electricity nor clean water has been estimated to be 1 billion people [1]. This has motivated us with the aim of providing a robust and sustainable technology that can treat water using renewable energy for people living in remote communities. We began by researching PV-powered RE-membrane systems, given that many arid regions that possess a limited and/or poor quality drinking water also exhibit high levels of solar radiation. This has already been shown to be the case for central Australia - a region that experiences an abundance of solar radiation (daily average of >6.7 kWh/m2) and minimal rainfall (200-300 mm per year), but a large groundwater reserves exist under most of the country. In many remote communities, drinking water is supplied from groundwater bores, which are of varying quality ranging from drinkable water to incomsumable brackish water. If the groundwater exhibits an overall salinity of less than 500 mg/L and minimal trace contaminants (for example arsenic, boron, uranium, nitrates, fluoride) then this can be a good solution, however there are several health problems associated with drinking high salinity groundwater. Therefore, for remote communities that possess a brackish groundwater resource, a small PV-powered desalination system can produce ample amounts of potable water and is a sustainable alternative to trucking water over great distances to remote locations.
In response, we developed the system shown in Figures 1 and 2, which uses a hybrid filtration system comprised of an ultrafiltration (UF) membrane to remove bacteria, viruses and particulates, coupled to a reverse osmosis (RO) or nanofiltration (NF) membrane to desalinate the brackish groundwater. The system is powered by 150W of PV panels and can provide about 1000 L of drinking water per (average solar) day for remote communities, using brackish groundwater source. Since both PV and membranes are modular technologies, the size could be scaled up or down.
Our system does not rely on batteries due to increased life-cycle cost, reduced robustness and environmental concerns regarding the waste. However, this introduces a R&D challenge: can we design membrane filtration systems that are directly coupled to RE generators with no energy storage?
All of our present research has indicated that the answer to this question is "yes!" and we have expanded our R&D in this area to encompass:
All of the work in this theme is performed together with the environmental engineering Membrane Technology Research Group at The University of Edinburgh.
References: [1] B. S. Richards, L. Masson, A. I. Schäfer (2009). Impact of Feedwater Salinity on Energy Requirements of a Small-Scale Membrane Filtration System, in Appropriate Technologies for Environmental Protection in the Developing World, pages 123 - 137. [2] M. Werner, A. I. Schäfer. Social aspects of a solar-powered desalination unit for remote Australia communities (2007), Desalination, 203, 375 - 393. [3] A. I. Schäfer, A. Broeckmann, B. S. Richards (2007) Renewable energy powered membrane technology. 1. Development and charazterization of a photovoltaic hybrid membrane system, Environmental Science and Technology, 41, 998-1003. [4] Richards, B. S., Capão, D. P. S. & Schäfer, A. I. (2008) Renewable energy powered membrane technology. 2. The effect of energy fluctuations on performance of a photovoltaic hybrid membrane system, Environmental Science and Technology, 42, 4563-4569. [5] Richards, L. A., Richards, B. S. & Schäfer, A. I. Renewable energy powered membrane technology. 3. Salt and inorganic trace contaminant removal by nanofiltration/reverse osmosis, Environmental Science and Technology, (submitted).