Photovoltaic (PV) Pumping

Introduction

There are two distinct fields of application for PV pumping systems: drinking water supply and irrigation. Experience from past projects has proven PV pumping systems to be technically mature and suitable for utilization in rural areas of developing countries. The systems in use have very low failure rates (below 1,5% of operation time) and are therefore highly reliable. The daily operation does not require specially-trained personnel, maintenance efforts and costs are low; therefore the comparatively high investment costs can be compensated.

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.

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.

PVP -Power	Head [m]	Flow Rate [m³]	People Supplied (Consuming 25 l/c*d)
1 kWp (equals about 500 m4/day)	10 30 50	50 15 10	2000 600 400
2 kWp (equals about 1000 m4/day)	10 30 50	100 35 20	4000 1400 800
4 kWp (equals about 2000 m4/day)	10 30 50	200 65 40	8000 2600 1600

Average Investment  [Euro]	1 kWp	2 kWp	4 kWp
Pumping System (PV-Generator, Inverter, Pump)	8000	15000	25000
Ready-to-operate  PV Pumping System (Pumping system, logistics, set-up, reservoir, construction, water distribution)	16000	25000	41000

Pv pumping costs.png

 

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.

GIZ has experience of PVP irrigation in projects in Chile (smallholder farmers), Ethiopia (tree nursery Forestry Dep.) and Bangladesh (irrigation of paddy fields). Experience in Bangladesh has shown that PV panels can have significant spatial requirements depending on the energy needed. This leads to disadvantages for farmers. KfW (German Development Bank) has supported the installation and dissemination of PVP pumps for irrigation in several countries in sub-Saharan Africa (Eritrea, Guinea, Mali, Namibia, Burkina Faso). At experimental level there are already technical solutions available for the application of PVP in stand-alone systems to irrigate an area of 30-40 hectares by using variable frequency drives (VFD) for any AC-motor.

Further Reading

• GIZ INTERNAL: DMS folder containing additional documents on PV pumping (documents also available upon request from GTZ-HERA)
• Product overview  and cases of market leader Grundfos
• Drinking water supply