17 February 2009

Water wheels begin their come back

Tom Shelley reports on a vast amount of untapped energy that can be obtained by applying some new technology to a very old idea



Although the basic idea is very old, one couple that have been spearheading a comeback for water wheels is Paul and Ingrid Bromley. They started developing a new generation of water wheels in 1991, primarily as a schools project.
Water wheels can be driven by the action of gravity water, water falling from a higher to lower under, or by harnessing the kinetic energy of flowing water. It is a very efficient way of harnessing energy with 80 to 90% conversion efficiency.
As Paul Bromley explains, advances in technology allow their wheels to be made with better steels than previously possible. And electronic technology allows them to use a Chinese made multi-pole generator to turn the energy into mains voltage and frequency AC current.
Paul acknowledges he has had help from PTC to, “encourage technical and design improvements.” It used to take him four weeks to produce a set of drawings by traditional methods before he began to use the parametric abilities within Pro/Engineer. It now takes two weeks to produce a top down CAD design, and just ten minutes to produce a complete set of drawings for a wheel that is customised to a particular water head and flow rate.
He has come up with a design for a 2m diameter, “Pico Wheel”, which produces 1.1kW. Efficiency at the axle is about 80%, with 3 to 5% losses in gearing and 19% in the generator, which equates to a water to wire efficiency of about 60%. They call their design the “Pedley Wheel”, after Pedley Wood in Cheshire, where the development took place.
By 1996, his wheel had been proven to be cheaper and more efficient for low head sites than comparable small turbines and the time had come to put it to the test. An isolated village in Sri Lanka was selected and the first Pedley wheel was installed there in 1998.
This wheel now supplies 25 houses and families with electricity, which is being used to power everything from sewing machines to refrigerators and it even supports a village hairdresser who has set up shop next door. A total of six wheels have since been constructed and installed in the country providing over one thousand people with 25kW of electricity in more than 200 homes.
As regards to cost, the wheels cost £6000, but are installed as a charitable venture at no cost to the Sri Lankan community through the Pedley Wheel Trust. Villagers pay about £1 per month for their water wheel produced electricity as opposed to £4 per month for kerosene which produces fumes and is the cause of countless fire related accidents throughout South Asia. He said that users can book hours of power supply for specific tasks such as ironing or spice grinding, but that one of the big consequences is enabling communications including telephones and connection to the Internet.
In a European context, cost of each installed kW is about £4000 for a water wheel, as opposed to £9000 for wind power, which takes into account the wind only blowing sufficiently to produce power for about 30% of the time, and £2750 for nuclear. The cost of power stations burning coal but equipped for carbon capture and storage is unknown at the present time.
There are also wheels at Pow Gill in Cumbria, and Stornaway in the Hebrides. And wheels described as, “Coming soon” include a 5m wheel generating 4kW from 100 litres per second at Holywell in North Wales, a 3.5m diameter wheel generating 2.5kW at Ludlow for Shropshire County Council and a 6m diameter wheel generating 5kW for two homes in Derbyshire.
Presently, all the wheels are overshot wheels where the water is applied to the top of the wheel as this is the most cost effective to produce. But many situations exist where the water head is only 1m or none at all, yet there is much kinetic energy to be extracted from a fast flowing stream. So the wheel has to be either breast fed where water is applied to the middle, or undershot. Paul told us that he is now working on design solutions with assistance from Birmingham City University for these situations and hopes to announce them soon.
The design of wheels on a desktop model scale is also being promoted through PTC as a schools science project to encourage interest in science and engineering.

The Role Of The Water Wheel
Water wheels have the potential to make a significant contribution to the world’s desire for carbon free energy. The idea is to couple them with low-cost generators to deliver usable power at mains frequency.
Water wheels were used in Ancient Greece and reached the height of development in the nineteenth century. In 1900 there were 30,000 working water wheels in the United Kingdom and 197,000 working water wheels in Germany.
The idea of micro-generation, exploiting energy on small scales, is particularly attractive to Third World countries where grid power is not available. Additionally, the emerging economies of China and India are likely to feed their increasing appetite for electrical energy by fossil fuel powered generators.
In Pakistan, according to the country’s “Vision 2030” report, hydroelectric power could produce 46,000MW of which only 6,500MW has been exploited. However, to meet the country’s projected 2030 energy need, Pakistan too is currently planning to burn vast amounts of coal, regardless of the consequences, unless economically viable alternatives can be found fairly quickly.
Even in England, a short walk along the banks of the little river Darenth, which happens to run past the office where “Eureka” is produced, shows site after site where water wheels once extracted power. But nobody seems to think they are worth bothering to exploit today.
According to a study by the Forum for Renewable Energy Development in Scotland, there are 657MW of financially viable hydroelectric schemes to exploit there, sufficient to power around 600,000 homes.

Pointers:
* The wheels produce a few kW, depending on water flow, at an installed cost in Europe of about £4000 per kW, less in the Third World
* There are currently three wheels working in the UK, with three more planned, and six in Sri Lanka, with more planned, depending on funding
* There are at least 30,000 potential sites in the UK, and 200,000 in Germany, where wheels could be put back into places where there were water wheels before. There is 657 MW of small scale untapped hydroelectric potential in Scotland and 40,000 MW in Pakistan and similarly vast amounts in other developing countries

Author
Tom Shelley

Supporting Information

Websites
http://www.pedleywheel.org.uk/

Companies
Parametric Technology (UK) Ltd

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