Traditionally the water pumping technology of choice has been the wind pump. Wind pumps provide long lasting solutions with a basic technology which is well understood and can be maintained locally. However even wind pumps have become expensive to install and to replace.

Solar water pumps and dc pumps are currently being used to irrigate crops, water livestock, and provide potable drinking water. Solar water pump uses peak solar array output which frequently coincides with high water demand during long, dry summer days. In the event of cloudy weather solar water pump systems often use storage tanks to store excess water. Unlike generator powered water pumping systems, solar water pumps do not require fuel or constant maintenance. Solar water pumps can also be designed for portability to be moved as water demand or change of seasons requires. Solar water pumps cost less to operate, offer modular capability to be quickly expanded as demand increases, unlike a generator or windmill water pumps.

Diesel water pumping is attractive due to the large power range of the pumps and the availability of water when it is needed. It can pump water for varying daily demands through longer operating periods (assuming sufficient borehole strength), thus allowing for the flexibility required in some applications. The technology is well understood and service for diesel engines is readily available. Recent fuel price increases and generally intensive maintenance schedules however can make diesel water pumps a costly pumping option.

Solar water pumps are often thought of as being an expensive technology, which is not able to pump enough water and which is not durable.

However, solar water pumps have come a long way in 25 years and today there are solar pumps on the market which have improved on previous technology.

1: Submersible pumps which can pump up to 200m heads;

2: Pumps that are able to pump larger volumes of water, e.g.:

At 100m, about 10,000 liters per day;

At 50m, about 20,000 liters per day;

Above performance can be doubled through dual systems (if the borehole allows his).

3: Low maintenance requirements (3 to 5 years).

4: Good performance which means fewer solar panels to pump the same amount of Water.

5: Some of the pump models can be backed-up by a genset to pump additional water with the same pump during the night or during overcast days;

6: Good quality and reliability.

7: Simple to install: Furthermore, solar pumps are well known for having the following features:

8: Require minimal attention as they are self-starting;

9: Solar pumps are "good" for boreholes as they pump over the whole day;

10: Weak boreholes can be used effectively with a low volume pump due to pumping 8 to

10 hours a day;

11: In most cases, a solar pump offers an ideal solution to the diesel option which requires operating funds (with uncertainty about future diesel prices), time investment for operating pump (manual starting etc) and logistics for fuel, maintenance, installation and de-installation;

12: Tracking arrays can be used to increase daily water pumping rates;

13: Solar pumps offer clean solutions with no danger of borehole contamination.

Theft of solar photovoltaic panels is a problem and one needs to look at counter measures if there is a risk of theft. Refer to web links below for more information.

Cost of solar and diesel pumps:

A cost comparison was conducted for solar and diesel water pumps over a range of pumping heads (10 to 200m) and a range of daily flow rates (3 to 50m3/day). The all-inclusive costs were calculated taking into account.

The initial upfront cost, the operating costs (diesel fuel for the operating life), maintenance costs, and replacement costs (diesel engine, solar submersible pump unit etc).Calculating the all-inclusive cost is a fair way of comparing solar pumps (usually higher upfront cost) with a diesel pump (usually lower upfront cost, but with ongoing diesel and intensive maintenance costs). The all-inclusive cost takes a long term approach and is calculated over a twenty year period, which is also the minimum life expectancy of a solar panel. The cost comparisons show that diesel pumps are on average two to four times more expensive over a 20 year period than solar pumps for pumping the same average amount of water per day! Refer to costing approach in final report for more detailed information.