| Traditionally the water pumping technology of | | | | panels to pump the same amount of Water. |
| choice has been the wind pump. Wind pumps | | | | 5: Some of the pump models can be backed-up |
| provide long lasting solutions with a basic | | | | by a genset to pump additional water with the |
| technology which is well understood and can be | | | | same pump during the night or during overcast |
| maintained locally. However even wind pumps | | | | days; |
| have become expensive to install and to replace. | | | | 6: Good quality and reliability. |
| Solar water pumps and dc pumps are currently | | | | 7: Simple to install: Furthermore, solar pumps are |
| being used to irrigate crops, water livestock, and | | | | well known for having the following features: |
| provide potable drinking water. Solar water pump | | | | 8: Require minimal attention as they are |
| uses peak solar array output which frequently | | | | self-starting; |
| coincides with high water demand during long, dry | | | | 9: Solar pumps are “good” for boreholes |
| summer days. In the event of cloudy weather | | | | as they pump over the whole day; |
| solar water pump systems often use storage | | | | 10: Weak boreholes can be used effectively with |
| tanks to store excess water. Unlike generator | | | | a low volume pump due to pumping 8 to |
| powered water pumping systems, solar water | | | | 10 hours a day; |
| pumps do not require fuel or constant | | | | 11: In most cases, a solar pump offers an ideal |
| maintenance. Solar water pumps can also be | | | | solution to the diesel option which requires |
| designed for portability to be moved as water | | | | operating funds (with uncertainty about future |
| demand or change of seasons requires. Solar | | | | diesel prices), time investment for operating pump |
| water pumps cost less to operate, offer modular | | | | (manual starting etc) and logistics for fuel, |
| capability to be quickly expanded as demand | | | | maintenance, installation and de-installation; |
| increases, unlike a generator or windmill water | | | | 12: Tracking arrays can be used to increase daily |
| pumps. | | | | water pumping rates; |
| Diesel water pumping is attractive due to the | | | | 13: Solar pumps offer clean solutions with no |
| large power range of the pumps and the | | | | danger of borehole contamination. |
| availability of water when it is needed. It can | | | | Theft of solar photovoltaic panels is a problem |
| pump water for varying daily demands through | | | | and one needs to look at counter measures if |
| longer operating periods (assuming sufficient | | | | there is a risk of theft. Refer to web links below |
| borehole strength), thus allowing for the flexibility | | | | for more information. |
| required in some applications. The technology is | | | | Cost of solar and diesel pumps: |
| well understood and service for diesel engines is | | | | A cost comparison was conducted for solar and |
| readily available. Recent fuel price increases and | | | | diesel water pumps over a range of pumping |
| generally intensive maintenance schedules | | | | heads (10 to 200m) and a range of daily flow |
| however can make diesel water pumps a costly | | | | rates (3 to 50m3/day). The all-inclusive costs |
| pumping option. | | | | were calculated taking into account. |
| Solar water pumps are often thought of as being | | | | The initial upfront cost, the operating costs (diesel |
| an expensive technology, which is not able to | | | | fuel for the operating life), maintenance costs, and |
| pump enough water and which is not durable. | | | | ?replacement costs (diesel engine, solar |
| However, solar water pumps have come a long | | | | submersible pump unit etc).Calculating the |
| way in 25 years and today there are solar pumps | | | | all-inclusive cost is a fair way of comparing solar |
| on the market which have improved on previous | | | | pumps (usually higher upfront cost) with a diesel |
| technology. | | | | pump (usually lower upfront cost, but with ongoing |
| 1: Submersible pumps which can pump up to | | | | diesel and intensive maintenance costs). The |
| 200m heads; | | | | all-inclusive cost takes a long term approach and is |
| 2: Pumps that are able to pump larger volumes of | | | | calculated over a twenty year period, which is |
| water, e.g.: | | | | also the minimum life expectancy of a solar panel. |
| At 100m, about 10,000 liters per day; | | | | The cost comparisons show that diesel pumps |
| At 50m, about 20,000 liters per day; | | | | are on average two to four times more |
| Above performance can be doubled through dual | | | | expensive over a 20 year period than solar |
| systems (if the borehole allows his). | | | | pumps for pumping the same average amount of |
| 3: Low maintenance requirements (3 to 5 years). | | | | water per day! Refer to costing approach in final |
| 4: Good performance which means fewer solar | | | | report for more detailed information. |