Eighteenth century pump and solar power technology provide irrigation solution

Increasing soil moisture levels through irrigation can lead to substantial increases in agricultural productivity, but most smallholder farmers in Africa do not have enough money to buy expensive equipment.

The system, being developed by product design engineering agency the Imagination Factory as part of an InnovateUK-funded competition for the Department for International Development, is designed to pump up to six tonnes of water per day, while requiring very little operation or maintenance.

The device, which under the terms of the competition must have a production cost of no more than £30 per unit, is based on a steam-powered pump, according to Julian Swan, co-founder of the Imagination Factory.

“The pump dates back to the very beginning of steam engines, the Thomas Savery pump, developed at the beginning of the industrial revolution, and patented in 1698,” said Swan. “It has no moving parts other than a ball valve, no pistons, no seals, and is very simple.”

A solar collector directs heat from the sun onto an absorber tube containing water, to produce steam.

The device then uses this steam to positively displace the water inside the pump chamber, said Swan. “It then relies on the steam collapsing and condensing to create a hard vacuum, and that then sucks water back into the pump chamber.”

To develop the design, the team scoured the library and collection of the London Museum of Water and Steam, including 100 year-old textbooks and instruction manuals, in a bid to understand how the pumps originally worked.

“There are no design guides, so it was a case of going through the archives, trying to measure off engravings to work out what the geometries of the pump chamber were,” said Swan.

The team completed the feasibility stage of the programme, in which they built a proof of concept rig, and were then chosen to take their design on to the next stage of the competition. They are now developing the concept into a demonstrator system.

They hope to begin testing the pump in a country in sub-Saharan Africa next year.