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Is anyone aware of the pros and cons of solar water pumping over hand water pumps?

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Clean water is essential to life but access to it is often limited in developing countries. Access to improved water sources was one of the Millennium Development Goals. Yet, as recently as 2011, 768 million people still drew water from an unimproved source and 636 million of these lived in rural areas [1]. The World Health Organisation [2], defines improved water sources to include household connections, public standpipes, boreholes, protected dug wells, protected springs, and rainwater collection; all within ‘reasonable access’ [3]. Options for providing potable water in a development context include:

• Surface water from rivers, lakes, ponds or shallow wells but risks contamination by faecal coliforms.

• Ground water from bore holes is less likely to be contaminated with faecal coliforms, but could need assessing for salinity or toxicity such as arsenic which is an issue in Bangladesh. Hand, diesel and renewable energy powered pumps can be used.

• Water tanker trucks can provide clean water but need to be able to get to the community. Water can also be delivered by motorbike. These services have costs. Having given a general introduction identifying the problem the focus of the answer is the advantages and disadvantages of solar water pumping compared to hand pumping. In both cases a bore hole or well is needed where a subterranean aquifer is present. Hand pumps are normally shallow wells and require physical labour and time which prevents other opportunities being carried out. Only one person can collect water at a time which can cause disagreements.

Solar water pumps are dependent on an adequate solar resource. They need a raised tank to store the water pumped during the day, but this can allow for a network of water distribution pipes and taps so that more than one person can collect water at a time. Typically, operation and maintenance costs for solar water pumping are low, but initial capital costs are high, although the price of systems is falling.

To present a case for solar water pumping, a project from Malawi is outlined based on a study by [4]. The unelectrified village of Nlukla is 25km south of the city of Blantyre in southern Malawi. The population of 820 rely on a 6m deep hand elephant pump. Coliforms from this hand pump were reported at 5800 per 100ml by [5] compared to the 0 per 100ml limit in UK [6].

A solar water pumping system was designed for Nlukla village. Daily water demand was based on 20 litres per person. Irradiation data was obtained from [7] for the location at Lat -15.676 and Lon 35.141. The lowest monthly irradiance of 4.34kWh/m2 /day was used in the model. A 50m borehole, with a 70m dynamic head was proposed. The sizing of photovoltaic (PV) array in terms of hydraulic power and solar irradiation was given by [8]. The main system components consisted of 1kW PV modules, a Grundfos SQF 2.5-2 Submersible Pump, 4 water tanks, pipes and taps for a gravity fed public distribution ... (more)

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2017-12-01 12:23:57 -0600
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Dec 01