Ron visits the mill to view for himself the use of water for power generation
In the search for environmentally friendly renewable energy many people, including myself, have advocated 'micro-generation' i.e. small scale generation from windmills, solar panels etc. It has been argued that a further opportunity for micro-generation exists in water power from our rivers, pointing to the numerous rivers that we have where water mills were once dotted along their courses.
One such river is The Frome, which flows through Somerset on its way to join The Avon. In the past there were at least 15 working mills along the river. There was one at Tellisford, a very small village near Bradford-on-Avon. Mr Battersby and his partner bought the disused mill a few years ago and they decided to try to harness the water power with a modern turbine. With the aid of some small grants they conducted a feasibility study that encouraged them to go ahead and install a Kaplan turbine.
Two years ago I saw a little of the extensive civil engineering work that proved necessary in order to site the turbine and recently I saw the finished installation at work. The turbine actually started turning in January of this year and it was soon generating a very creditable 55kW (74 horsepower in old money), most of which was supplied to the national grid. It had been a fairly wet winter so that in January the river flow was rather high. Mr Battersby anticipated that the turbine output could be as low as 10kW in the summer months with an annual average output of around 32kW.
It has been a very well executed project and the effort involved is praiseworthy; one might anticipate that the turbine will continue to produce electricity for many years with relatively low maintenance costs. Tellisford offers one of the best sites on the river, few others offer as much potential. Nevertheless 32kW is not a lot of power when thinking in terms of the national need and this mill demonstrates the problem in trying to harness the power of these relatively gentle rivers. The whole project cost approximately £250,000, less than 10% was funded by grants, the rest was supplied by Mr Battersby and his partner. All the electricity generated in excess of their own need is sold to the national grid at an attractive price; nevertheless they estimate that it will take 25 years to recover their investment, depending on the future price of energy.
Another similar project at Lyme Regis made the news recently when it started operation. It is expected to produce 32,000 kWh/year, which corresponds to an average output of 3.65kW. A professor from Southampton University made a study of the potential of these types of river turbines and concluded that the total capability was disappointingly less than 1% of the national consumption.
With both of these installations it was pleasing to see that they quoted their performance in meaningful units. So often with renewable energy projects, especially wind turbines, the true output is hidden by stating that the output is sufficient for 'x' homes, which is rather meaningless. One suspects that it is a deliberate attempt to disguise the fact that the output is low in measurable units and that these installations are a poor return on the investment. Such a poor return may be justified in the long term but let us not be bamboozled.