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Innogy Plc Plan for Hydro-Electric Scheme
at Romney Lock, Windsor

Thamesweb are grateful to RWE npower for permission to reproduce this information and pictures on The Royal Windsor Web Site.
Graphics ©RWE npower

There is a discussion area for this project here


Dec 2007 It seemed that this project had been abandoned.

May 2008 A Planning Appication has been lodged for a revised scheme. Discussion area here

The Hydro Electric Scheme

The original artist's impression of the hydro-electric scheme at Romney Weir. This has since been amended. see below.

We usually associate hydro-electric schemes with giant dams and flooded valleys extending for hundreds of miles so it comes as a pleasant surprise to hear of an innovative scheme to supply power to Windsor Castle from the river that flows by its doors. Modern technology now makes it possible to harness the normally placid flow of the Thames by means of a discrete turbine house which could generate enough power to satisfy the needs of the Castle via an underground cable.
  Even though the fall from the 'upstream' Windsor reach of the river, to the downstream reach below Romney is only four feet, that difference in height is apparently sufficient to generate significant electrical power and with the government's ambitious target that by 2010, 10% of the country's electricity should come from clean, renewable sources of energy, Windsor has a source of just such clean energy readily to hand. In fact, for over 70 years, the energy at Romney Weir in Windsor was used by hydro-turbines at Tangier Island to pump water to communities on both sides of the river.
  Romney Weir is almost unique in that it has more gates than it currently needs such that not all the gates can be opened at once. If they were, the reaches downstream would be unable to cope. In addition, the constriction that is Windsor Bridge could not supply that amount of water either.
  Innogy plc (formerly known as National Power) is proposing to install a small hydro-plant that would be capable of generating 200kW of electrical power, providing 1.3 million units of electricity to be supplied to Windsor Castle, a pioneering 'first' in the south-east of England although many such projects have been undertaken in France and Germany.

Aerial view of the location

The location of Romney Weir, with the proposed location of the hydro-electric system.
Windsor Bridge is at the bottom of the picture, and Romney Lock Cut to the right

  The proposed project would feature a turbine in each of the last two weir bays. Each turbine would drive an electrical generator to produce 100kW of electricity, which will be fed through a buried cable up to Windsor Castle. The turbines would be enclosed in a small building and any noise produced by the machinery would be fully contained.
  This is a relatively small project for this size of river. The turbines will draw an average flow of 10 cubic meters per second (m3/s - cumecs) and a maximum of 14m3/s. The average flow in the Thames at this point is 56m3/s. Fine metal grills will be inserted at both the intake and outfall of the turbines so as to exclude fish and debris.

Flooding and other impacts of the scheme

All aspects of the scheme have been carefully considered to avoid any impact on residents or river users. More information is available at the Eton Town Council Offices, or by contacting RWE nPower.
  Romney Weir is one of the largest weirs on the Thames. Even though it has 10 sluice gates,
local residents may have noticed that the weir becomes flooded (so that the fall over the
weir disappears completely) when only 6 gates are open. This happens because the river
downstream of Romney is 'full' i.e. it cannot discharge flow any quicker. When this happens,
opening more gates at Romney Weir cannot release any greater flow from upstream to
  In very high flows, the water level will rise at Romney as it has always done, but if the weir
is fully flooded, opening more gates cannot reduce the water level. A flooded weir behaves
like any another part of the river channel. An analysis of gate openings at Romney in high
flow conditions clearly demonstrates that opening more than 6 gates at Romney has no
effect on water levels. In other words, Romney Weir has more sluice gates than it needs to
discharge even very high flows. Using 2 of the 4 surplus gates for hydro-generation enables
part of the unused section of the structure to be utilised for a positive benefit.

Boat-users and navigation

  • The upstream and downstream water levels will not be affected by the scheme.
  • Access to the weir by boat is forbidden and prevented by piles and cross-chains.
  • The intake to each turbine is protected by a grill, so anyone in the water cannot be drawn into the turbines.
  • The same amount of flow is approaching the weir as before, so the scheme will not cause any additional currents towards the weir.
  • The lock cut and the lock itself will not be affected in any way.
  • Flows taken down the Eton mill race, used occasionally as a canoeing course, will not be affected.

Fisheries and angling

  • Formal angling points will be unaffected by the scheme.
  • Fish screens upstream and downstream will ensure mature fish are not taken into the turbine. Additionally, an eel pipe will also be incorporated to ensure safe passage for eels.
  • The operation of the fish pass and side spillway will not be affected.
  • Juvenile fish such as coarse fish fry small enough to pass through the screen will pass through the turbine with minimal effect on mortality.
  • The Environment Agency has allocated three years of research funding in order to monitor the fisheries impacts of the scheme. This is expected to start in parallel with scheme commissioning in 2003.

Local ecology

  • Environmental studies have been undertaken to consider the potential impact of the scheme on the local terrestrial, aquatic and geomorphologic forms.
  • The scheme will utilise less than 20% of the Thames average flow.
  • The only change experienced by this flow is that it passes through the turbines rather than over the weir. A wetting flow will be maintained over the weir at all times.
  • Water Quality will remain unaffected, the operation of the turbines will not result in any
    additions to the water flowing through them. In the event of an accidental leakage, any oils used will be bio-degradable

Visual impact

The weir before construction looking upstream

The weir before construction looking upstream

An artist's impression of the weir following construction of the hydro-electric facility

A revised artist's impression of the weir following construction of the hydro-electric facility

View from Eton bank

An artist's impression of the installation from the Eton bank, looking downstream. This has since been revised and may now be rather smaller.


  • Acoustic measurements were taken around the site at Romney by a specialist team, and compared with measurements taken at an identical turbine operating in France.
  • Background noise levels outside nearby residences were found to be relatively high even at night over 50 decibels (dB(A)). Projected noise levels at 80 m distance (closest residential area at Eton Bank Court) are relatively low at 38 dB(A). In other words, no noise impact is expected.

Local disruption during construction

  • The time required to complete the in-river works has been estimated at 16 weeks including contingency. The total period of construction and commissioning of the plant will be approximately six months.
  • Access and transportation will primarily be via the upstream river using barges to Romney Island. Workmen will access the site by using the public footpath. It is estimated that only about six people are likely to be working at the site during the construction process at any one time.
  • The working area will be limited to a piece of fenced off land at the end of the weir on Romney Island, owned by the Environment Agency. It will not impinge upon public use of the towpath, nor prevent access to mooring points upstream of the weir and will not be accessible to the public.
  • Work will be limited to daytime periods only, pumps and generators will be fitted with appropriate silencers and acoustic hoods (in accordance with BS5228) as necessary.


As the first such project on the Thames, Innogy is keen to set a good example of the potential that hydropower can play on the UK's lowland rivers, especially in built-up areas. Innogy would welcome feedback on the project and any questions or concerns on the scheme,
or any comments that may be able to improve the project, should be addressed to Alastair Gill at:

Innogy Plc.,
Innogy Hydro
Dolgarrog Power Station
Dolgarrog, Nr. Conwy
North Wales, LL32 8QE

Tel: 01492 660811

This project was initially co-funded by the European Commission.

First Green Light for Windsor Castle Clean Power Scheme

Planning permission has now been granted for this project to go ahead. On 12th February 2004 Innogy Plc., released the following:

Yesterday evening, a unique hydro scheme moved one step closer to providing clean electricity for Windsor Castle ­ all supplied by the power of the River Thames.
  RWE Innogy, through its hydro business, is delighted to have received outline planning consent to install a 200kW hydro-electric scheme at Romney Weir at Windsor.
  The project would be the first of its kind in the south of England and would generate environmentally friendly energy from the flow of water over an existing Thames weir.
  It is intended that the electricity generated would be exported to Windsor Castle. This would provide the Royal Household and tourist attraction with electricity generated without the production of carbon dioxide associated with global warming and climate change.
  The next stage of the project will be to finalise details of the design of the powerhouse which will enclose the turbine and associated equipment. RWE Innogy are currently completing the consultation process which has included incorporating feedback received from local residents and other interested parties such as the Environment Agency. Careful consideration is also being given to the materials and colours used to construct the turbine enclosure to enhance its appearance.
  The scheme would be adjacent to the bank of Romney Island but almost invisible from public footpaths on both Romney Island and Windsor Bank.
  Alastair Gill, Hydro Development Manager, RWE Innogy, commented that, "This is an exciting environmentally friendly project and will provide enough clean energy to meet around a third of the electricity needs of the castle. It will also offset approximately 600 tonnes of carbon dioxide every year which would otherwise have been released in to the atmosphere from the burning of conventional fossil fuels. Today's announcement brings the project one step closer to being a reality."
  RWE Innogy is a leading UK renewable energy developer. It develops and operates both wind and hydro-electric plants. RWE Innogy currently operates nine hydro-electric power stations in Scotland and Wales with a total combined capacity of 50MW

Schematic of the turbine house

1.  Arrow represents water flow through the scheme.

2.  Debris and fish screen to prevent upstream wildlife and rubbish from getting to the turbines. The screen is automatically cleaned to ensure clear a passage for water.

3.  Submerged hydro-electric propeller turbines, each generating around 50kw of electricity, transferred to Windsor Castle through insulated cables.

4.  Penstock gates to control the volume of water flowing through each turbine. Open when turbine is running, closed when turbine is shutdown.

5.  Draft tubes, designed to aid smooth water flow back into the Thames..

6.  Screens - prevent downstream wildlife from swimming up into the turbines.

7.  Existing weir gates, raised to allow water to reach the turbines.

8.  Extendable lifting gantry - used to lift equipment from barges in and out of weir bays.

9.  Existing walkway, authorised access only.

July 2005

Final permission has been given for a £1m, 200kw, hydro-electric power plant to supply Windsor Castle with around one third of its electricity needs. A Buckingham Palace spokesman said: "We're constantly looking at ways of saving energy such as energy efficient light bulbs."
  Four turbines are to be installed, built by Npower Renewables, in two bays of Romney Weir. The installation will be virtually invisible and very quiet and is expected to be completed and on-line before the end of 2006.
  Alastair Gill, Hydro Development Manager for Npower renewables, said, "This is great news. We have worked hard on the project to get it to this stage and its fantastic to receive the go-ahead. As well as being carefully designed to fit into the surroundings, by using the existing weir, the project will have little impact on the ecology, navigation and marine life of the river. With the weir shown to be more than adequate to cope with the flow of water along this stretch of the Thames, the hydro scheme will also have no effect on flood control measures."
  A spokesperson from the Royal Household said, "We have a policy of introducing and maintaining energy-efficient practices wherever possible. Consent for the Romney Weir Hydro Scheme is a major contribution."
  Tim Reeder, Climate Change Regional Project Manager (Thames) at the Environment Agency said, "We are always supportive of initiatives which can help reduce the impacts of climate change and have taken account of their local environment. The Environment Agency are keen to further investigate opportunities for hydropower, and are pleased to see this project finally come to fruition".
  The next step is to run a feasibility study to better understand how to build the scheme. All being well construction is expected to begin next year, with Windsor Castle due to receive green electricity before the end of 2006.

General information about Romney Weir Hydro scheme can be found on the npower renewables web site at

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