Potential power?

When talking about the UK’s renewable energy potential, the amount of renewable energy that may be achieved by exploiting the 20,000 weirs and watermill sites in the country – possibly 600-1000MW - is often overlooked.

The Domesday Book apparently records more than 5000 mill sites in the 10th and 11th Centuries. Many more were developed between the 12th -20th Century. Between 1850 and 1940 numerous companies and foundries were both manufacturing and/or importing and installing turbines in the British Isles. Local foundries in every area were producing their own variation of Francis Turbines for low head installations. There is historical evidence in the archives showing manufacturers and sites where these turbines were installed.

It has been suggested that ‘experience is yesterday' s answer to today's problem’. One might take this a stage further and suggest that ‘today's answer has yet to be tried and proven’. Today's students seem to have little knowledge of past technologies and what has happened to the full time five year apprenticeship? In the not too distant past education allowed for both experience and qualifications. Today's graduates have qualifications but the computer screen is all too often the horizon of their experience. To understand small and micro hydro power they might well benefit from reading technical information from 1850-1950. By 1960 technical colleges were disposing of hydraulic turbine test rigs - I personally bought some of these redundant units. Water companies were also taking out energy recovery turbines and replacing them with electric motors.

In the past 10 years or more there has been a move in the reverse direction. Many universities are spending money on renewable energy/hydro power. Water companies are installing energy recovery turbines. However, graduates involved still appear to lack the historical knowledge and the practical understanding of the subject. The priority seems to be low cost installations rather than quality that will last a lifetime.

Today we are confronting a new, very serious, battle to save our planet. Renewable energy is our best hope. It has to be said that hydropower of any size has a high up front cost which may take perhaps 8-15 years to recover, but thereafter pays excellent dividends. Large hydro provides us with the vast majority of renewable energy currently being generated from any source but even small or very small installations are competitive. Unfortunately there are several examples of low cost solutions, installed by those lacking experience, that have failed even before costs have been recovered and such botched attempts are used to support the efforts of others who wish to deny this significant source of renewable energy to the UK.

With the aforementioned in mind, I would like to refer you to a recent 139 page report by TV Energy, who are an independent not-for-profit energy agency partly funded by different bodies, one of whom is the Environment Agency (EA). The report may be downloaded on www.tvenergy.org.

Entitled ‘Hydropower in South East England’, the report starts by highlighting the fact that the south east of England is ‘festooned’ with mill sites but goes on to dismiss the great majority of them and downsizes the rest - in doing so demolishing the power potential even for these remaining sites. For instance, the table on page 118 for Thames weirs has used minimum flows for the basis of their calculations and has come up with power outputs very significantly smaller than the useful potential of each weir.

The requirements of the EA handbook ‘Hydropower for Agency Staff’ occupies a significant number of pages (18) of the TV Energy report. The EA has no remit to be interested in hydro power. It derives no income from hydro power (Act of Parliament April 8 1981). They are not allowed to charge for the water passing through small and micro hydro power schemes.

The EA claim to purchase all their electricity from renewable sources. In the past I have queried why the EA does not use the potential 25MW on the above mentioned 44 Thames weirs over which it has complete control. The Thames drops some 76m between Lechlade and Teddington and has, for example, flows at Sandford Weir near Oxford suitable for a turbine passing up to 30m3/sec (dry summer flow less than 10m3/sec, winter flows sometimes in excess of 350m3/sec. Further downstream the flows naturally increase with an even greater potential). The possibilities here are typical of run of river installations all over the world, particularly in France and Europe where successful schemes are common place on heads as low as 1.4m.

Sandford Weir had a papermill until the 1970' s and two vertical shaft turbines on 2.69m head which produced two to three times the expectation of power presented in the TVEnergy report. The report concludes that Sandford weir has the potential for just 135kW installed capacity - why when with modern turbines it is capable of producing upwards of four times this amount? More than likely it is because of the fixed output of the turbine type they have selected to recommend.

Since the south east is festooned with mill sites why did the report identify only 1400 sites, then downsize this to 900 and then consider just 400 which it then suggests have a total installed capacity of just 6MW? Furthermore to dismiss certain types of turbine technology by saying that the Francis and Crossflow type turbines are inappropriate below 3m head is also incorrect - there are numerous examples to prove otherwise. One of the many continental manufacturers has a list of some 140 successful installations of crossflow turbines on from 1.4m to 3m head that they have carried out in recent years on the continent and individually generating up to 100 kW+.

Our country's present aim is to achieve 10% of our renewable energy by 2010. Exploiting run of river hydro power has the potential to make a major contribution. Failing to identify the theoretical potential and/or downsizing this potential without giving good reasons is misleading if not irresponsible.