Barrage versus Lagoon: Direct comparison is necessary
We understand that representations have been made that a barrage would not be an appropriate way to generate large amounts of power in the Severn, and tidal lagoons would be more effective. In the interests of balance we thought it might be helpful to provide the following.
The particular advantages of a barrage for the generation of renewable energy in the Severn Estuary are:
1. The amount of energy produced
The electricity generated by turbines is determined by the amount of water and the height through which it falls when passing through the generating turbines. So to capture the same amount of energy as a barrage, a tidal lagoon would have to cover the same area as the height is set by the tidal range in the Severn Estuary.
Such a lagoon, or series of lagoons would be very large indeed, and would be liable to obstruct shipping unless expensive measures are taken.
2. The cost of construction
A barrage makes use of the existing coastline for perhaps 90% of the perimeter of the basin in which the high tides are trapped. A tidal lagoon has to fund the entire perimeter, so must be more expensive to build. A big tidal lagoon would have to go into the deep water, so assumptions about low cost construction in shallow water would not apply.
3. Flood prevention and mitigation
A barrage can prevent any flooding from sea level rises or storm water surges (as occurred during hurricane Katrina in New Orleans) for the entire upstream coastline. For a Cardiff to Weston-super-Mare barrage this is 170 miles of coastline protected.
In addition, flooding in the lower River Severn can be reduced: at high tides the sea level overtops the weir near Gloucester which stops the river flowing freely. By shutting the barrage sluices just before high tide when the river is in spate the extent of river flooding can be reduced.
The best way to assess the merits of alternative ways of harnessing the power of the tides in the Severn Estuary is to carry out an Appraisal of all the alternatives on a common basis, with an independent steering committee to ensure objectivity.
Roger Hull
Severn Tidal Power Group
August 2007
Senior Counsellor
Chelgate Limited
One Tanner Street
London
SE1 3LE
Tel: 020 7939 7949
Fax: 020 7939 7938
Mobile: 07805 108458
Email: mst@...
Registered in England,
registered number - 226305
http://www.chelgate.com
-----Original Message-----
From: tidal_power_uk@... [mailto:tidal_power_uk@...] On Behalf Of Peter W. Ullman
Sent: 21 August 2007 16:58
To: 'Knight, Oliver (SDC)'
Cc: tidal_power_uk@...; Tim Lang; peter@...
Subject: [tidal_power_uk] Canadian Tidal Power
Hi Oliver,
Canada’s Bay of Fundy has the world’s highest tidal range and is the site of a demo project installed in 1984, a 16 mw straflo turbine.
The Canadian government and the Nova Scotia and New Brunswick provincial governments are working through how they will deal with permitting and supporting the various tidal technologies being proposed for the Bay of Fundy. They are holding a series of public meetings in Nova Scotia. Last week I attended one in Wolfville, Nova Scotia.
Nova Scotia is conducting a Strategic Environmental Assessment. First, they commissioned EPRI (Electrical Power Research Institute, based in Palo Alto, California) to study the resource for in-stream tidal (Canadian term for “tidal stream”). Result: about 2200mw of which about 300 mw appeared to be practically achievable. The tidal lagoon resource is about 5000 MW exclusive of pumping.
Given that in-stream tidal has numerous devices in the experimental stage, they have bifurcated the permitting process into “Test Sites” (in-stream) and “Commercial Sites” (tidal lagoons). There are appropriate differences between the test-technologies (includes proving the technology, track record, etc.) and tidal lagoons (commercial technology: no need for technical learning curve) and the process for permitting they must undergo.
Barrages are not being considered at all. Canada did extensive studies done in the 1970’s including consideration of 63 different barrage configurations and the use of barrages was subsequently dropped from consideration. Following is their (the Strategic Environmental Assessment team) statement:
“In the past, tidal energy technology involved installing turbines in barrages across estuaries or bays. The Nova Scotia Power Annapolis Royale Tidal Power Generating Station, commissioned in 1984 is an example of this approach. However, this technology is now considered unsuitable for broad-scale commercial use because of environmental and economic concerns.” [They go on to describe the technologies under consideration, in-stream and …] ”Another tidal technology is the tidal lagoon, which creates an offshore enclosure, but unlike a conventional barrage does not totally block tidal flow.” (OEER, Fundy Tidal Energy, 2007)
This leaves the SDC (i.e. the UK) as the only entity worldwide giving serious consideration to a barrage. Even EDF who own the world’s largest barrage have no interest in building another barrage. They recently invested in tidal stream.
I trust your Commissioners are aware of this fact and will weigh it when making their recommendations. There are a number of very highly-respected Commissioners whose reputations will be impacted by this report and it would be a shame to ask them to sign off on a report without them being fully informed by you, if you ask them to recommend spending yet more public money on the Severn Barrage and continue to delay the commercial installation of privately-funded tidal lagoons whose aggregated output would dwarf the output of the Severn Barrage and cost the public nothing.
Best wishes,
Peter Ullman
From: tidal_power_
uk@yahoogroups. co.uk [mailto:tidal_ power_uk@ yahoogroups. co.uk] On Behalf Of Knight, Oliver (SDC)
Sent: Tuesday, August 21, 2007 7:30 AM
To: tidal_power_uk@yahoogroups. co.uk
Subject: [tidal_power_uk] FW: Towards a Coherent Network of Marine Protected Areas, 2-4 October Scarborough
This conference may be of interest to people on this group.
Oliver Knight
From: Bob Earll [mailto:bob.
earll@coastms. co.uk]
Sent: 21 August 2007 12:18
Subject: Towards a Coherent Network of Marine Protected Areas, 2-4 October Scarborough
Towards a Coherent Network of Marine Protected Areas
Conference - BOOK NOW
2nd- 4th October 2007, Scarborough
Natural England
Dear colleagues
There are clear international goals for the UK to establish a national network of Marine Protected Areas and this is being supported by work on the Marine Bill and the concept of Marine Conservation Zones. This conference will highlight a wide range of thinking and work going towards this including the need to effectively engage stakeholders.
The Marine Protected Areas Conference aims is to bring together those involved in management, designation, science and policy development of MPAs. Delegates will be able to share information and learn about the latest MPA science, good practice and policies from speakers from the UK and overseas as we look towards achieving our MPA targets.
Would you:
- Please circulate this to colleagues that you think will be interested in this conference
The programme including the booking form is attached.
TO BOOK
You can book and pay online with a credit card at www.coastms.
co.uk or pay by credit card over the phone, BACs, cheque etc; we issue invoices and receipts. Please email or fax the booking form to bob.earll@coastms.co.uk or 01531 890415
Organised by CMS – Coastal Management for Sustainability
Please circulate this email to colleagues who may be interested
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