Photovoltaic (PV) Pumping

Regular cleaning of PV modules and maintenance by competent personnel as well as reliable availability of replacement parts are a basic requirement for efficient and sustainable system operation. Furthermore, awareness campaigns for users as well as an appropriate maintenance concept with private sector participation are essential for success. Experience from PV pumping project have shown that there is a general danger from theft and vandalism of PV modules. Measures such as the construction of walls or fences can reduce this risk, as can awareness raising activities among the local population.

There are two distinct fields of application for PV pumping systems: drinking water supply and irrigation.

Drinking Water Supply

For sites up to about 2,000 inhabitants and pumping heads up to about 60 meters PV pumping systems are often more cost-effective than diesel pumps, or at least competitive. For larger systems, a combination of PV and diesel pumps has proven worthwhile (hybrid systems).

A big disadvantage are still the high investment costs for a PV pumping system which can be up to 2-3 times the investment for a comparable diesel pump in a village with 1,000-2,000 inhabitants. However, the overall costs (investment + operation) for small PV pumping systems (1 kWp) are well below of comparable diesel pumps. For medium size systems (2 kWp), comparison is still in favour of PV pumps. For systems of 4 kWp and larger, a break even situation arises which requires proper cost comparison depending on the local conditions.

There is broad application for medium-sized standard systems of 2kWp and a pumping capacity of 1,000 m⁴/day (m⁴/day = flow rate (m³) x pumping head (m) per day, equals e.g. about 35 m³/day x 30 m head) on sunny days. This amount of water is sufficient to supply about 1,400 people with 25 liters/person/day. A study from 2008 revealed for Senegal that solar pumping systems are more cost-effective than diesel pumps up to a pumping capacity of 3,150 m⁴/day. This equals a daily total amount of water of 45m³ with a pumping head of 70 meters supplying 2,000 people.

Irrigation

Economics of PV pumping systems for irrigation is dependent on numerous factors. In general, PV pumps for irrigation can only be operated cost-efficiently under the following conditions:

• In order to reduce the energy requirements of PVP irrigation systems water-conserving and energy-saving micro-irrigation techniques have to be applied.
• The plot size for PVP irrigation should be below 4 hectares.
• High rates of system utilisation are necessary to achieve economic viability of PVP irrigation systems.
• Therefore PVP systems are limited to irrigate permanent crops and continuous crop rotation in arid climates.
• High value-added cash crops like fruits, vegetables and spices should be given preference to recoup the high initial investment.
• Low-interest loans should be available for the same reason.
• PVP irrigation systems require a careful planning of the crop schedule and are more demanding of user skills.