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Pumping Off Grid Energy options

Pumping: Energy for Rural Water Supply

Providing access to water is a critical community development task. In most areas, water is not readily available where it is needed for settlements or farming. Sooner or later, community, household, rangeland or agricultural planners must devise methods of supplying water on site. This means pumping it out of a borehole or well, or diverting it from a spring, lake, stream or river.

Water systems planning for communities, refugee camps, settlements and farms is a complicated process, usually carried out by qualified experts. In rural areas without access to grid power, water supply experts may not have sufficient energy knowledge to select the most appropriate power source for a given pump requirement. This module is designed to help planners choose effective energy systems to meet their water supply requirements.

1.0 Types of Water Supply

 There are three general water supply requirements in rural areas:

Table 1: Net present comparative costs of 5 energy systems for irrigation

Energy Source

1 ha


5 ha


20 ha


PV pumping




Grid Electricity




Grid Electricity (3km extension)








Gasoline / petrol




Source: Whiffen, et al., 1992

2.0 Determining Pumping Needs and Water Source Specifics

Pumps should be chosen based on the actual requirements of the site. These include the actual water requirements, site security, the amount of money available, the maintenance, the service available, and the spare parts infrastructure. Hundreds of pumping systems fail in developing countries because they are introduced without a critical understanding of, or attention to, these issues. Before buying a pump or pumping system, it is wise to visit a water pump supplier familiar with your area to find out what type of pumping systems are already in use.

There are two important prerequisites for community water pumping technology projects:

Even before choosing a pump type, you need to carefully look at water needs, and the quality of your water source. Suppliers often use the figure m4 (i.e. meters to the fourth power) when calculating pump energy needs; this represents volume of water (cubic metres, m3) times the static head/vertical lift (metres, m).

2.1 Amount of water needed and variation by month. This is the single most important criterion for selecting pumps, and is typically given in cubic metres (m3) or litres (1,000 litres of water = 1 m3). The amount of water required can be calculated by considering the number of people, livestock or hectares requiring water supply. (see Table 2). Remember that water requirements change seasonally with humans as well as livestock and farming systems.

2.2 Depth of the water (vertical head). The height that water (given in metres or feet) must be pumped is the second critical factor when choosing pumps. This is the total vertical distance between the pump and the storage container or point of discharge. It may be quite small in the case of surface water, or as high as 200 metres (or more), in the case of a borehole.

2.3 Water storage. Is there a need for water storage? What is the size of the required storage tank? Remember, with pumps that deliver a high volume, there is less of a need for storage. On the other hand, pumps withirregular output, such as wind and PV pumps, require more storage. In such systems, 2 to 5 days is a minimum storage volume. However, storage can often be more expensive than the rest of the pumping system combined. Given this factor, pumping systems that are incapable of delivering large quantities of water over constant periods (e.g., wind and PV) are often rejected by people over more constant, high volume systems, such as diesel and petrol pumps.

Water source characteristics.

There are two categories of water sources:

 Table 2: Nominal Water Requirements

Typical Usage

Nominal Daily Water Supply Requirement (litres)

Human (subsistence level)

5-7 litres of clean drinking water per person per day are considered "subsistence" by the UN. Does not include water for washing or cleaning.

Human (acceptable)

40 litres



Cattle watering






Irrigation (vegetables) 1 ha


Source: Whiffen, et al.

3. Considering Technologies Choices

There are a number of technologies for pumping water, ranging from very basic to extremely complicated. Actual choice of pumping technology will depend on your individual water requirements and the level of infrastructure in your location. Commercially available pumping systems fall into the two classes, mechanical and electrical. The following categories are in most wide use for water pumping:

In the case of electricity systems, one of the weakest links in the system is the type of pump, rather than the energy technology. Avoid batteries on pumping systems wherever possible. Where costs permit, pump water to a storage tank that supplies water by gravity, particularly when using an intermittent energy source such as wind or photovoltaics.

 Table 3: Pumping Technology Options

Type of Pump

 Head (metres/m)




25-35 metres

Compatibility and the ready supply of spare parts critical

Diesel pump

Practically no limit

Fuel consumption, availability of spares, O&Mcosts


25-35 metres average (can be much greater with higher powered pumps)

Fuel consumption, availability of spares, O&M costs

Wind pumps

150 m maximum

Minimum mean wind speed 2.5 m/s


Depends on head/speed of source

Must be located at site with moving water

Electric Pumps

500 kWp
1000 kWp

1500 kWp


5 metres

10-15 m

25-100m (flow very low at high heads)

Minimum mean insolation 4 kWh/m2/day.

Not viable for high heads or flow rates.

Submersible pump must be sealed. Spares must be available.

Wind electric pump

Limit imposed by electricity generated

Minimum mean wind speed 4 m/s

Diesel genset & electric pump

Practically no limit

Fuel consumption, availability of spares, O&M costs. Expensive to use genset unless for other purposes additional to pumping.

Gasoline genset & electric pump

Practically no limit

Fuel consumption, availability of spares, O&M costs. Expensive to use genset unless for other purposes additional to pumping.

3.1 PV’s Niche in Water Pumping:

PV pumping is a mature technology with scores of quality products available. However, the market for PV pumps has not grown as fast as expected a decade ago. This is largely due to the high investment costs of PV systems, the intermittence of supply (hence, the requirement for, and expense of, storage), the need for sealed submersible pumps, and the lack of information about them.

PV pumping systems typically consist of a PV array, a load matching device, and a motor/pump. Photovoltaic systems have several beneficial features including virtually no recurrent costs. They can be considered for power requirements below 4 kWp, and are attractive below 2 kWp. Most systems are available between 200 and 1500 Wp.

Three typical commercial systems include:

3.2 Hand pumps have been in use for centuries. Recent efforts by the United Nations, donors, non-governmental organisations (NGOs), and private companies and individuals to extend potable drinking world to all people in the world have resulted in rapid growth in the number of hand pump models

Most hand pumps are robust. Most models available on the market can be operated by virtually anyone, from child to elder. However, given water volume and head requirements, hand pumping can be a time- and energy-consuming task. Hand pumping is a poor option for those who can afford other options. (for an interesting evaluation of hand pumps in action.

The optimal situation for a hand pump is a shallow, protected well (low head), with a quick recharge of the water table, with the pump situated next to the house or point of use. The pump should be robust, easy to maintain, require as little human energy as possible, and be easy to maintain. Even more optimal is when the pump in use is used by a number of other households, so that spares are readily available (and inexpensive), and technicians are available to maintain and repair the pumps. A number of such pumps are available. Prices (excluding the cost of digging the well and protecting it) can be as low as US$ 100, or as high as US$ 1000.

3.3 Windpumps have been used to pump water for a thousand years. Wind has been used for pumping for irrigation and drinking water on all continents. A number of technologies, ranging from old robust models developed for ranches and farms in the early part of the 20th Century, to new, sophisticated and efficient models are widely available throughout the world. Wind pumps are produced in many developing countries, as well as many European, Asian and Latin American countries.

A wind pump will require a minimum wind speed 2.5 m/s, and will rarely operate at its prime at speeds lower than 4 m/s. Wind pumps need to be sited directly over, or very near, the well. This restricts their use because often a well site or river are in low areas, or areas surrounded by trees, with poor wind speeds and regimes. Wind generators are far more flexible in this regard, and can provide electricity not only for water pumping, but also for other uses. Because of the intermittent nature of wind, storage is required for virtually all wind pumps. This raises the cost considerable. The cost of wind pumps is high.

However, most require relatively little and infrequent maintenance. Intermittence of wind, the generally low rates of discharge, the costs of storage, and the investment cost of the wind pumps discourage their use for potable water compared to other alternatives. There were more than 6 million wind pumps in operation in the United States in 1930. Today there are fewer than 50,000. There were nearly 10,000 wind pumps operating in Kenya in 1950, while today there are perhaps fewer than 300. On the other hand, there has been a "renaissance" in wind pumping in South Africa. After a decline similar to that elsewhere in the world, there are now more than 1 million wind pumps in use in South Africa today.

Perhaps the best situation for a wind pump is in an area with a shallow, protected water source, with a steady, reliable wind regime (average wind speeds of 5 m/s). The area would have few surrounding trees, and a large storage facility (at least five days' supply of water, for periods of calm). The price for such a pump, with 3m blade, excluding well and storage, would range between US$ 750 to US$ 2500, depending upon the height of the tower and the make (imported, locally made, etc.).

3.4 Wind generator pumps. Wind turbines produce electricity which can then be used to drive an electric pump (like PV). Wind turbines use pumps similar to PV units. They have the advantage over wind pumps (mechanical) in so far as they can be located in sites with the best wind conditions, and do not need to be located directly over the water source. Wind turbines require higher mean wind speeds than wind pumps (4 m/s or more). As with wind pumps, the wind regime needs to be studied carefully when choosing this option, and when siting the turbine.

3.5 Hydraulic rams/Hydrorams. Hydraulic rams are a tried and true technology that has been in use for a number of years. Hydrorams use the energy from fast-moving streams to pump water, and can pump water up heads of 50 metres or more. A ram must be located either in a fast moving stream. This limits their application.

3.6 Petrol and diesel water pumps have been in use since the early part of the 20th Century. Large, robust irrigation pumps can be found on the Nile that have been in operation for 70 years. New, inexpensive petrol and diesel pumps (and even kerosene pumps) are increasingly available from the Far East, and can be purchased in almost any country where irrigation and pumping equipment is sold.

Both petrol and diesel generators can be used to provide electricity for driving pumps. Sealed submersible pumps have proven to be the most robust and cost-effective for small-scale applications, generally for drinking water. Special care should be taken when choosing pumps, and electricity-generating systems should be sized for the pumping load, unless other non-pumping applications are required.

Petrol gensets are portable. They are very suitable for small-scale irrigation as they are inexpensive and can be carried to site and back, and can be used to generate electricity for other applications. However, the amount of water they can deliver is relatively limited, and the cost of fuel and spares is relatively high. Moreover, petrol gensets have a relatively short life span, particularly if they are used as base load.

Diesel gensets can deliver high flow rates even at high heads. However, given the cost of diesel gensets, they would never be purchased only for water pumping (as a diesel pump would be a much more sensible technology choice). Their costs and benefits, as with a petrol genset used for pumping, need to be weighed considering their other uses, and not just their use as pumps. As with wind turbines, and petrol gensets, they do not need to be located directly near water sources, but can be located where they are needed most (e.g., in a camp, a house, a school, a hospital, etc.), with the electric pump supplied by cable. 

Click on any of the icons below, or click here for further reading on pumping, or here for supplier information on pumping. If you wish to go to the next module, click here for the "Cooling, Refrigeration and Freezing Module (Number 3)" of this Guidebook, or click on one of the other modules below. Click here for links to visit some good links to other Internet sites.

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