Thursday, January 31, 2013
Energy Institute: Potential for Hydropower on the River Thames.
The following is cobbled together from some notes taken at this event, hosted at the Energy Institute (London) on January 28th (2013): http://www.energyinst.org/events/view/909
The thread is, that since we have the river (Thames) close to us, surely we can use its flow of water to produce energy. Thus, weirs in particular, might be considered as assets, of which there are 44 on the Thames, owned by the Environment Agency. Each weir has been screened for its potential in hydropower generation, with consideration to: the "head" (i.e. the drop between the flowing water at the upper and lower parts), and the prevailing flow of the river there. Along the Thames, the head range is 0.7--2.7 metres, with an average of 1.8--1.9 metres. Since this is in the region of the 2 metres reckoned to be viable for power generation, the prospects appear favourable; however, environmental impacts must be considered too. It is the duty, after all, of the Environment Agency (EA) to protect the environment.
Interestingly, it is developers rather than the EA who build hydropower installations, to whom the EA grant a lease for their use of the weir. Romney weir - work on which started in September 2011, and is due to be completed in March 2013 - has some spare capacity for water flow as a flood relief channel (most weirs still need to be kept for flood defence).
Here are some points of consideration taken from, the Environment Agency - Consultation on river flow and water abstraction standards for hydropower : https://consult.environment-agency.gov.uk/portal/ho/br/standards/hydro
*Flows, constraints and water abstractions
*Monitoring of environmental impact - In Europe some schemes taken out because of environmental damage.
*Impoundment licence - authorises holder to obstruct or impede flow.
*Flood risk assessment - flood defences.
*Fish pass approval from national panel - there are both sea trout and salmon in the Thames.
*Hydropower is possible at Teddington, for which an application is close to being placed. The anticipated output is 450--490 kW, from 3 screws.
*The most fish-friendly kind of turbine is the Archimedes screw, which accordingly is the preferred technology.
*The existing Thames weirpools, especially gravels, are valuable for fish spawning, and the cumulative impact on spawning grounds mist be considered.
*Since there is no such thing as a "typical year", the impact on wildlife will be monitored over 15 years, to get a kind of "average".
*The proposed installation at Goring (and Streatley) http://ergobalance.blogspot.co.uk/2011/11/further-proposed-hydroelectric-power-on.html was mentioned, over which there is apparently some concern from local residents about noise. I believe that to install the three turbines needs and investment of £2.5 million, hardly a trivial sum! The Goring scheme has taken years to get moving, and is intended to be funded by sale of shares (e.g. 500 investors putting in £5,000 each?). The maximum power output is reckoned at 300 kW, with an average of probably 140 kW. A 3 blade screw is envisaged for Goring, a design on which tests have been made with live fish - most of which survived. Goring is a community led project, as is that at Osney.
*At Romney, a 5 blade screw is planned, which computer models suggest should be fish friendly, but the proof of this will be with actual fish, once it has started. If it proved to be a fish-shredder, it would have to be shut down, as is the case for all such schemes, should they prove to result in damage to the environment
*20-22 sites are being pursued, but because weirs were not designed to be used as hydropower installations, they are subject to a lengthy approval process.
Useful sources of info: Hydropower: A guide for you and your community / Generating energy / Publications / Home (England) - Energy Saving Trust England : http://www.energysavingtrust.org.uk/Publications2/Generating-energy/Hydropower-A-guide-for-you-and-your-community
Setting up a low carbon community group: from kitchen table to willing & able | Low Carbon Hub : http://www.lowcarbonhub.org/advice/2011/12/05/setting-up-a-climate-change-community-group-from-kitchen-table-to-willing-able
Protecting the environment by promoting the use of hydropower: British Hydropower Association : http://www.british-hydro.org/index.html
And a few final points (some from the lectures, and some of my own):
Hydropower is a critical feature of electricity generation in many countries http://en.wikipedia.org/wiki/Hydroelectricity, most notably Norway which gets 98+% from its water systems, closely followed by Brazil (86%) and Venezuela (69%); hydropower provides 61% of Canada's electricity, while for the United States it is a little under 6%, and the U.K. nearer 1%.
On the Thames, a working facility exists at Mapledurham http://ergobalance.blogspot.co.uk/2011/11/100-kw-hydroelectric-turbine-at.html although this is privately owned, rather than by the EA. The head is 2.05 m. Once all the planning permission, licenses etc. have been secured, practical challenges remain: e.g. it is not easy to undertake construction on a river, since access to the work area is often difficult. In the case of Teddington, the river is tidal as well as fluvial and hence it flows up and down continually. To avoid environmental contamination, biodegradable oil is recommended to lubricate the hydraulics in plant machinery.
Impacts on wildlife must be considered, i.e. protected species, invasive species, fish rescue. In the event of an emergency, contingency plans must be in place, e.g. in the case of a flood, plant & coffer damns should be removed, then simply move out & let it flood! The final weir in the line is at Richmond, and is owned by Port of London authority, with a half lock and barrage. It is tidal and is left open for part of the day. Caversham weir has too low a head and is not suitable for hydro. A facility with Sunbury proposed 4 screws is proposed at Sunbury. Although, 3 screws would be the most efficient, it has been decided that having 2 fixed speed plus 2 variable turbines is the best compromise for the overall prevailing river conditions there. The EA is considering the prospect of removing some of the weirs that are not needed for navigation, as part of the overall strategy.
Goring & Streatley Hydro-electricity project (PDF slides) http://www.chilternsaonb.org/uploads/files/ConservationBoard/PlanningDevelopment/Dave%20Holt.pdf
Small scale hydropower rejected sites https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/47952/755-wag-report-annex-4.pdf
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