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Senin, 10 Januari 2011

Tips dan Trik Memilih Baju Pesta Muslimah

Tips dan Trik Memilih Baju Pesta Muslimah

Busana muslimah identik dengan baju gamis bukan hanya milik mereka yang ingin pergi ke pengajian atau ke masjid. Kini dengan perkembangan busana muslim tidak hanya sebatas baju gamis, Anda juga bisa tampil bergaya dengan model produk busana muslim yang tetap sederhana namun mewah.
Busana seperti apakah yang harus Anda kenakan untuk menghadiri pesta formal ?
Sebenarnya simple saja, busana muslimah yang simple pun bisa Anda kenakan untuk ke acara pesta yang formal. Namun dengan tambahan kreasi pastinya.
Berikut tips nya :


1. Jika Anda menghadiri acara pesta di siang hari, kenakan baju muslimah dengan warna terang, namun pilihlah bahan pakaian yang mudah menyerap keringat dan tidak mudah kusut. Sebaiknya, kenakanlah pakaian potongan bukan gamis. Dan untuk Anda yang tidak banyak aktivitas di sana, mengenakan rok panjang bisa menjadi pilihan, dan akan terlihat lebih anggun. Tempat jual busana muslim dan baju gamis biasanya menyediakan aneka pilihan.

2. Jika Anda menghadiri acara pesta sore hari yang santai, Anda dapat mengenakan padanan warna yang segar, seperti hijau muda atau biru muda. Dengan tambahan bordiran, payet atau tunik jepang, disertai dengan variasi warna bahan yang lebih muda. Anda bisa memakai selendang agar penampilan Anda tidak monoton, Anda pun akan lebih terlihat gaya namun tetap formal.

3. Jika acara pesta berlangsung malam hari, produk busana muslim gaya glamour bisa menjadi pilihan Anda. Namun tidak perlu mengenakan yang bertabur kristal atau payet. Anda bisa menggunakan kaftan dengan embroidery emas atau perak. Alternatif lain, gunakan baju gamis bercorak floral dengan teknik lukisan atau tunik panjang bergaris kebaya yang dipadukan bersama kain.

4. Jika ingin tampil muda, tidak ada salahnya Anda mengenakan batik. Saat ini sudah banyak kain batik yang dikemas dengan gaya kontemporer. Pilih saja yang bermodel Jackie-O atau bergaris babydoll dan dipadu dengan denim atau celana pipa. Kunjungilah fashion shop muslimah langganan Anda.

5. Jika Anda ingin tampil lebih mewah, mengenakan stola atau pashmina bisa membantu. Atau selendang dari bahan organdi yang serasi. Carilah butik fashion ataupun butik pakaian yang menyediakan pakaian muslima dan baju gamis kebutuhan Anda.


6. jangan lupa kunjungi toko toko online untuk melakukan perbandingan harga dan kualitas mngkin salah satunya bisa mengunjungi toko online aneka baju takwa, batik, jilbab seperti www.dfashionku.com


sumber : olah dan http://dunia-wirausaha.com

Jumat, 15 Oktober 2010

The Hagestein Weir in the Netherlands


Completed in about 1960, the Hagestein Weir is one of three movable weirs, or dams, along the Rhine River in the Netherlands. The Hagestein Weir has two enormous arch gates to control water and generate power on the Lek River near the village of Hagestein. Spanning 54 meters, the hinged gates are connected to concrete abutments. The gates are stored in the up position. They rotate down to close the channel.

Dams and water barriers like Hagestein Weir have become models for water control engineers around the world.

Rabu, 13 Oktober 2010

ANALISA KESEIMBANGAN LINTASAN DAN EVALUASI CONTINOUS LOOP CONVEYOR UNTUK MENGURANGI DELIVERY TIME DENGAN PENDEKATAN SIMULASI

ANALISA KESEIMBANGAN LINTASAN DAN EVALUASI CONTINOUS LOOP CONVEYOR UNTUK MENGURANGI DELIVERY TIME DENGAN PENDEKATAN SIMULASI

(Studi Kasus : PT Indoprima Gemilang Gresik)

Danil Setiawan
Jurusan Teknik Industri Fakultas Teknik Universitas Muhammadiyah Gresik
Jl Sumatra 101 GKB, Gresik 61121, E mail ; khamamah@gmail.com

Said Salim Dahda., ST.,MT.
Program Pasca Sarjana Jurusan Teknik Industri Institut Teknologi Sepuluh Nopember, Surabaya

ABSTRAK
Keseimbangan lintasan ( line balancing ) produksi merupakan suatu hal yang penting dalam suatu perusahaan. Keseimbangan lintasan tersebut diperlukan agar memiliki pembebanan yang berimbang sehingga aliran produk dapat berjalan dengan lancar. Dengan metode Rank Positional Weight perusahaan wiring harness PT Indoprima Gemilang mendapatkan effisiensi sistem 93.89 % dan balance delay 6.11 %, melalui penentuan presedence diagram, presedence matrik, serta proses peta kerja, dan menggunakan evaluasi continous loop conveyor sebagai acuan untuk menentukan delivery time dan waktu baku yang dibutuhkan sebagai acuan untuk setting kecepatan optimal konveyor yaitu 333 mm/det sehingga menghasilkan output 1375 set perbulan.
Dari model tersebut kemudian dimodelkan kedalam software arena untuk mendapatkan gambaran umum, khususnya untuk melihat output yang ada dari kondisi awal 6 operasi menjadi 5 stasiun operasi
Kata Kunci : keseimbangan lintasan, konveyor, simulasi


ABSTRACT
Line balancing is importantproplem in the line production. Line balancing necessary in order that line production is smooth. With Rank Positional Weight methodh pt Indoprima Gemilang company get efficiency system 93.89 % and balance delay 6.11 %through step presedence diagram, presedence matrik,and standard operational production and use continous loop conveyor evaluation for determined delivery time nd time standard for use setting delivery optimum conveyor is 333 mm/det and than provide output 1375 set per month.
From this model and than in put to arena software, give general research in the system, specifically for be found output product the first condition with 6 operation to 5 station operation.
Keyword : line balancing, conveyor, simulation

skripsi teknik industri, industrial engineering




Senin, 11 Oktober 2010

Memorandum by the Severn Tidal Power Group (CC 21)

Memorandum by the Severn Tidal Power Group (CC 21)



THE UK CLIMATE CHANGE PROGRAMME
INTRODUCTION

  1. The Severn Tidal Power Group (STPG) is a joint venture between six of the UK's leading power engineering and construction companies.[19] It was formed in 1984 following publication of the favourable report of the Severn Barrage Committee[20] which identified the viability of an electricity generating barrage in the Severn Estuary to capture the energy form the world's second highest tidal range. STPG has been entrusted with the development of the Severn Barrage project ever since.

  2. The Severn Barrage Committee was set up by government following the oil price crisis of the late 1970's to examine the engineering options and technical feasibility for the project, its contribution to the security of electricity supplies and the wider regional benefits that would ensue. The miners' strike and the Chernobyl catastrophe raised further concerns in regard to security of UK electricity supplies, and in 1986 a definitive £4.2 million study of the Severn Barrage was commissioned by the Secretary of State for Energy, funded jointly by the Government, the CEGB and STPG.

  3. This study, reported in Energy Paper 57,[21] confirmed the technical feasibly of the project and included discussion of the environmental effects, regional implications and estuary management issues. Detailed reports have also been published by ETSU between 1989 and 1994, including further studies on environmental and regional issues.

  4. As a consequence of the privatisation of the electricity industry in 1990, a study of how the Severn Barrage Project may be financed was postponed until the new market conditions stabilised. In 1993, STPG proposed that a full financing study should be undertaken to examine how the project could be taken forward as a joint venture between the public and private sectors in the spirit of the recently announced Private Finance Initiative. Unfortunately, the decision by government to cease the funding of further research as tidal power appeared uneconomic precluded the implementation of this essential study.

  5. A new proposal by STPG to examine how the project could be taken forward was submitted to the DTI in September 1997. In February 1998, STPG was invited by the President of the Board of Trade, the Rt Hon Margaret Beckett MP, and the Energy Minister, John Battle MP, to discuss the project in the light of the Government's targets for sustainable development and renewable energy. It was concluded that because of the very long term nature of the project it was doubtful that the Severn Barrage could be financed solely in the private sector. The priority was therefore identified as a new appraisal of the project to take into account the changes in the electricity market, the different attitudes to environmental issues, and the PFI experience of public sector/private sector joint ventures which value the wider regional, economic and environmental benefits. STPG has sought the Government's support for this essential new research and eagerly awaits a response.


THE SEVERN BARRAGE PROJECT

  6. An electricity generating barrage across the Severn Estuary, to capture the energy from the second highest tidal range in the world, will produce, on average, 17,000 million kWh each year, or some 6 per cent of the annual electricity demand of England and Wales. If it were to replace coal fired generation, it would enable the UK to reduce its total annual CO2 emissions by 16 million tonnes, approximately 3 per cent of the UK's carbon emissions from all sources. If detailed development of the project is commenced now, power would be available from around 2012, throughout the next century, and beyond.

  7. The Severn Barrage is therefore the largest single renewable energy project able to make a significant contribution to UK electricity supplies in a reasonable time scale. When fully commissioned it would make a major contribution towards the Government long-term targets for renewable energy and the reduction of emissions of greenhouse gases.

  8. The project will cost some £10 billion and require 200,000 man years of employment, representing 35,000 jobs at peak, many of which will be away from the barrage site in the manufacturing regions of the UK. The project will also bring significant regional benefits through the more benign conditions that will be created in the basin above the barrage and from a fourth crossing of the estuary. Substantial growth is anticipated in the Severnside region with an estimated 40,000 jobs being created.

  9. In the light of the recent discussions at the Kyoto and Buenos Aires conferences, pollution free electricity from the Severn Barrage will be a valuable asset in regard to internal emissions trading, particularly if new coal fired stations are to be considered.

  10. Unlike most other renewables, tidal power is predictable and with reasonable maintenance the Severn Barrage will have virtually indefinite life. Its contribution can therefore be planned within a comprehensive long-term energy policy.

RESPONSE TO ISSUES IDENTIFIED IN THE ETRA COMMITTEE'S PRESS NOTICE 82/97-98 (19 NOVEMBER 1998)

The desirability of the options contained in the UK Climate Change Strategy in the light of non EU countries' commitments

  11. World population is predicted to grow such that by 2020 nearly 85 per cent will be in the emerging nations. These people will demand the services that energy can provide: heating; cooling; cooking; lighting; mobility and motive power.

  12. The demand for energy is therefore expected to double by 2020 in comparison with 1990 levels requiring that, if greenhouse gas emissions are to be stabilised, either this increase in energy must come from non-fossil fuel sources, or that carbon sequestration techniques are developed in conjunction with fossil fuel energy conversion technologies.


  13. Development of appropriate technologies and strategies to meet the UK's own targets will enable British industry to export these technologies in the growing world markets, especially those of the emerging nations.

  14. Significant reductions in the UK's own emissions will enable it to play a leading role in emissions trading.

The role of the climate change strategy as the first step towards greater reductions in the longer term, i.e., beyond 2010, with particular reference to behavioural change.

  15. The three most important elements of the climate change strategy are:


    —  to place greater emphasis on energy saving through improved efficiency and better energy management;


    —  to introduce controls to reduce the use of energy for transport, particularly the use of fossil fuels;


    —  to place greater reliance on the use of renewable energy for electricity generation.
  16. People will continue to demand the services that energy can provide and government should not seek to restrict or regulate access to these services. Government's aim should be to educate and encourage people to moderate the way they use the services energy provides and to avoid unnecessary use, using price differentials, where appropriate. The main drive, however, should be towards research to seek ways whereby the services can be provided more efficiently and without waste.

  17. The climate change strategy has three apparent weaknesses.

  18. Firstly, it places too great an emphasis on the contribution that combined heat and power (CHP) installations may make. CHP can only show greater efficiency in energy conversion compared with individual heat and electricity generation when the heat and electricity loads are matched. This state does not normally occur continuously throughout the diurnal cycle and CHP is much less efficient than individual generation when generating with one mode dominant.

  19. Secondly, the climate change strategy does not recognize properly the significance of the development of fuel cells which make use of the hydrogen cycle. These are now well advanced and by 2010 should be able to make a real contribution, particularly in the transport sector. The economic production of hydrogen by electrolysis will increase the demand for carbon-free electricity either from the renewables or from nuclear power.

  20. Thirdly, the climate change strategy does not address the time scale for replacing the UK's ageing generating capacity (coal, oil and nuclear) much of which will be reaching the end of its economic life post 2010. Realistically, the only technologies capable of replacing this plant, in addition to gas, are the large scale renewables (e.g., off-shore wind and tidal power from the Severn), nuclear and "clean" coal. All but gas require some 10 to 15 years for design development, the UK planning process, construction and commissioning.

  21. Gas-fired generating plant will produce electricity at about half the cost of these other options, although for the Severn Barrage, the cost of electricity generated following payment of the development and construction debt will about half that of gas.

  22. Insufficient certainty in market prices, and thus also in rate of return for these high capital cost projects, suggests that the private sector may be unwilling to make the necessary investment and that intervention by government in the market will therefore be required.


  23. Replacing generating capacity also requires consideration of environmental questions other than lower emissions of the greenhouse gases. Unless existing power station sites are used, as would be possible with nuclear power or coal, substantial infrastructure development is necessary. Moving from the present sites would also lead to loss of jobs, although new jobs would be associated with new locations. In the case of the Severn Barrage, the regional development opportunities associated with the more benign conditions in the barrage basin are estimated as creating an additional 40,000 jobs.

The Government's timetable for producing and implementing the Climate Change Strategy

  24. See comments in paragraph 20 above.

  25. Further research to establish which renewables can realistically make a significant contribution, taking into account the wider social, economic and environmental effects, is essential for long term planning and to generate business confidence to ensure the necessary investment is made.

  26. For example, we understand that a study is being undertaken by the University of Liverpool's Centre for Marine and Coastal Studies to compare the environmental impact of tidal power from a single site in the Severn Estuary with the impact from the 15 or so off-shore wind power station sites that would be necessary to provide an equivalent installed capacity.

The role of different sectors of the economy in meeting the emissions reductions targets and the merits of sectoral targets

  27. Tidal power from the Severn Estuary could provide some 6 per cent of the annual electricity requirements of England and Wales with no emissions of greenhouse gases, thereby saving some 3 per cent of the UK's annual carbon emissions from all sources by comparison with coal. It is the only predictable renewable energy source able to make a significant contribution to the Government's targets within a reasonable time scale.

The policies from the consultation paper on Climate Change Strategy which will be required to meet the UK's legally binding target for the basket of six greenhouse gases and the domestic target for carbon dioxide emissions

  28. See comments in paragraph 15 above.

The uncertainties involved in emissions projections and the impact of policies upon those projections

  29. No comment.

The mechanisms required to monitor the effectiveness of policies in reducing emissions

  30. No comment.

The extent to which "flexible mechanisms" should be used in achieving the legally binding target

  31. Internal emissions trading would allow the carbon free electricity from the Severn Barrage to be matched with re-planted coal-fired stations, thus enabling some 15 per cent of the UK's annual electricity requirements to be generated with a net saving in carbon emissions of 3 per cent. Similar trading between replacement nuclear power and coal/gas would ensure that the targets are no more onerous to achieve when existing nuclear stations reach the end of their economic lives.


The economic and other costs of the options in the Climate Change Strategy

  32. In paragraph 22 we suggest that intervention by the Government in the electricity market may be necessary to ensure that the best investments are made in regard to a long-term electricity generating policy. The necessary data on which to base informed decisions does not exist for many of the renewables, in particular, how renewable energy may be traded in a liberalised market and what is the full environmental impact of conversion for different energy sources.

  33. If the wider social, economic and environmental benefits are to be valued, mechanisms must be established which properly reflect the long-term nature of these benefits and the "value for money" that accrues from them.

  34. In the case of the Severn Barrage Project, no proper financing studies have been undertaken to establish the nature and extent of the public sector support required to ensure the project can proceed. A new appraisal of the project is essential to separate the infrastructure and regional benefits, including coastal protection, from the power generation aspects of the project so that the cost of electricity can be properly compared with that from the other major UK energy sources.
S J Taylor
Chairman, Management Board
5 January 1999




19   Members of the Severn Tidal Power Group are: Sir Robert McAlpine Ltd. Balfour Beatty Major Projects Ltd. ALSTOM Hydro Ltd. Rolls Royce Power Engineering Ltd. Taylor Woodrow Construction Ltd. Tarmac Construction Ltd. Back

20   "Tidal power from the Severn Estuary"-Volume 1: Energy Paper 46; HMSO 1981. Back


21   "The Severn Barrage Project: General Report": Energy Paper 57; HMSO 1989. Back

http://www.publications.parliament.uk

Severn Estuary Tidal Power Consultation - Resource Page

Few people interested in the Severn estuary and the surrounding area can be unaware of the debate about harnessing the power of the tides. It is the biggest issue currently affecting the estuary and one which the Severn Estuary Partnership is keen to see properly debated.
The UK Government is committed to generating 20% of the nation's energy from renewable sources by 2020, while the Welsh Assembly Government target is for 4 terawatt hours of electricity to be generated from renewable sources by 2010. This latter target will require 800MW of additional installed capacity from onshore wind resources in Wales, and 200MW of additional capacity from offshore and other renewables. A tidal power project in the Severn estuary could also contribute to the UK’s commitment to meeting the European Union’s Renewable energy target along with domestic and international greenhouse gas targets. Developments in the Severn estuary, with a tidal range of 14 metres (the second largest tidal range in the world), could therefore make a major contribution to meeting both these ambitious targets, but any scheme is inevitably going to have a significant impact on habitats and wildlife. It is also claimed that some proposals could also limit the entry of shipping to the ports of Cardiff, Bristol, Gloucester, Newport and Sharpness.
A number of organisations have stressed the need for an open public debate in order to help identify the best way of capturing the enormous renewable energy resource of the Severn estuary whilst safeguarding its internationally important combination of species and habitats and bringing lasting benefits to local communities. The Government’s Severn Tidal Power Feasibility Study Consultation is therefore gathering and assessing evidence to enable Government to decide whether or not to support tidal power development in the Severn Estuary.
In July last year the Government published a list of ten possible schemes, including barrages, onshore and offshore lagoons, a tidal fence and a tidal reef. They then assessed, in high level terms, the costs, benefits and impact of potential schemes and how they might affect the environment and the region. Following this process Ministers have now recommended the following schemes for detailed analysis:
  • Shoots Barrage - located near the Severn road crossings, estimated to cost £3.2bn to construct and generate 2.7TWh/year or just under 1% of UK electricity
  • Beachley Barrage - slightly smaller and further upstream than the Shoots Barrage (and upstream of the Wye), estimated to cost £2.3bn and generate 1.6TWh/year
  • Fleming Lagoon - an impoundment on the Welsh shore of the Estuary between Newport and the Severn road crossings, estimated to cost £4bn and generate 2.3TWh/year
  • Bridgwater Bay Lagoon - an impoundment on the English shore of the Estuary between Hinkley Point and Weston Super Mare, estimated to cost £3.8bn and generate 2.6TWh/year
  • Cardiff-Weston Barrage - located between Brean Down and Lavernock Point, estimated to cost £20.9bn and generate 16.8TWh/year or some 4.4% of UK electricity.
New Scientist Map of short list
Original long list of options
Current shortlist of 5 Tidal Power options (Guardian Interactive Map)
Original list of 10 Tidal Power options (BERR)
It is important to note that the Government is not seeking views in this consultation on whether or not to build a Severn barrage or other scheme. They will be asking for views on this in a second public consultation, probably in 2010, once there is detailed information on the costs, benefits and impacts of the short-listed schemes.
The five projects selected are those that the government's engineering consultants, Parsons Brinckerhoff, deemed to be based on the most proven technology. Proposals for tidal reefs and tidal fences are not included. The former would involve a series of slow-moving, fish-friendly turbines over a purpose-built causeway in the estuary while the latter would involve building only a partial barrier between Cardiff and Weston-Super-Mare. Both these proposals are acknowledged as having minimal impact on the local environment.
There have been allegations that Parsons Brinckerhoff miscalculated the costs of a tidal lagoon project championed by Friends of the Earth. The report sent by the consultants to ministers stating the tidal lagoon option would be eight times more expensive than the barrage scheme and would not generate as much power, claims denied by the designers. David Elliott, of the energy and environment research unit at the Open University, has also stated that a single big barrage would be problematic in terms of harnessing energy since it would only provide two short bursts of power every day. He considers that several smaller tidal turbines around the coast, operating at different times, would be a better solution. Likewise the RSPB is disappointed that the Cardiff-Weston barrage option is on the short list, considering that the final scheme must be the one that generates as much clean energy as possible, while minimising harm to the estuary and its wildlife. They consider that the barrage would destroy huge areas of estuary marsh and mudflats used by 69,000 birds each winter and block the migration routes of countless fish.
The Partial Impact Assessment of Severn Tidal Power prepared for the Department of Energy and Climate Change compares the five projects against the “do nothing” option, which is considered to be the generation of electricity from Combined Cycle Gas Turbines and other options for meeting renewable energy and GHG targets. It also states that there may be a regional economic cost to ports and to local fishing, additional environmental costs from the loss/damage of habitats and species, reduced ‘ecosystem services’ including negative effects on biodiversity and harm to fish stocks.
Because of these issues and others, the Sustainable Development Commission, the UK Government’s independent watchdog on sustainable development, set out three ‘sustainability tests’ which a Severn tidal power scheme should pass:
  • It must be publicly led as a project and publicly owned as an asset, in order to avoid short-termist decisions and ensure the long-term public interest
  • It must go ahead in full compliance with EU Habitats and Birds Directives, which will require assessment of mitigation and compensation on a scale as yet unseen in Europe
  • Any tidal power scheme must not divert Government attention away from much wider action on climate change

The Severn Tidal Power Consultation phase closed on the 23rd of April. For the latest information on the second phase of the study, please visit the Department of Energy and Climate Change's Severn Tidal Power Feasibility page, or the Welsh Assembly Government's Severn Tidal Power page.
A second public consultation will be held, probably in 2010. This will still be before any final decision is made by the Government on whether to support a Severn tidal power scheme.

Severn Tidal Power

Severn Tidal Power

The huge 14-metre tidal range of the Severn Estuary is one of the highest in the world. It represents a renewable, predictable resource with the potential (through a tidal power scheme) to generate up to 5 percent of the UK's electricity needs, and so make an important contribution to the 2020 renewable target and wider climate change and energy goals.  However, much more work is needed to assess the pros and cons of a Severn tidal power scheme before making a decision on whether to go ahead with a scheme and if so, which scheme and on what terms.
 
This work is being done through the Severn Tidal Power feasibility study. The study is expected to run until sometime in 2010, at which point is expected to be a second public consultation before decisions are taken. The decision on whether or not to support a Severn tidal power scheme will be taken in the context of wider climate and energy goals and the alternative options for meeting these goals – and will be a question of the relative costs, benefits and impacts of a Severn tidal power scheme, as compared to other options.
 
If you cannot find the information you are looking for on these pages – or if you would like to sign up to receive the Severn Tidal Power e-newsletter, please contact: severntidalpowerunit@decc.gsi.gov.uk
 

News
 

18 October 2009

Information in Welsh

Information in Welsh is available from the Welsh Assembly Government: Severn Tidal Power [External link] web pages.

Gwybodaeth yn Gymraeg

Cewch wybodaeth yn Gymraeg drwy fynd i dudalennau Ynni'r Llanw ar Afon Hafren ar wefan Llywodraeth Cynulliad Cymru yn www.cymru.gov.uk/llanwarafonhafren

Severn Barrage

Severn Barrage

From Wikipedia, the free encyclopedia
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Barrage locations considered over the years. Black indicates lines of most interest, with associated peak power generation at that location.

The Severn Barrage is any of a number of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. Ideas for damming or barraging the Severn estuary (and Bristol Channel) have existed since the 19th century. The purposes of such a project has typically been one, or several of: transport links, flood protection, harbour creation, or tidal power generation. In recent decades it is the latter that has grown to be the primary focus for barrage ideas, and the others are now seen as useful side-effects. The UK Government is currently undertaking a Severn Tidal Power Feasibility Study which will consider all tidal range technologies (including barrages, lagoons and others) in the Severn estuary.
The building of such a barrage would be a huge engineering feat, comparable with some of the world's biggest construction projects. The huge size and cost of most of the ideas over the years are what have kept plans firmly on the drawing board.

Contents

[hide]

[edit] History

There have been numerous proposed projects over the years, initially to provide a safe harbour and more recently to generate electricity.

[edit] Early projects

Thomas Fulljames's own impression of his proposed Barrage
In 1849 Thomas Fulljames, a civil engineer and the county surveyor for Gloucestershire proposed a barrage from Beachley to Aust (now the site of the first Severn Bridge), a span of just over 1 mile (1.6 km). Since this was before serious electricity demand, the first proposals were based on the desire for a large shipping harbour in the Severn Estuary, and also road and railway transport and flood protection.[1]
Diagram of a plan to harness tidal power on the River Severn circa 1921. Caption from Popular Mechanics Magazine 1921
No action was taken on Fulljames's proposals and three quarters of a century later, in 1925, an official study group was commissioned. An awareness of the large tidal range of 14 metres (46 ft),[2] second only to Bay of Fundy in Eastern Canada,[3][4] led to a proposal to generate 800 Megawatt (MW) of electricity at English Stones and although considered technically possible, it was prevented on economic grounds (then costing £25 million).[5] The viability was tested a few years later in 1931 when Paul Shishkoff, a Russian immigrant, demonstrated a 300 horsepower (220 kW) prototype tidal generator at Avonmouth.[6] It included a novel mechanism for spreading the power output over 24 hours. The full barrage was estimated at £5 million at the time.
In 1933 the Severn Barrage Committee Report (HMSO) from a committee chaired by Lord Brabazon recommended that a 800 MW barrage across the English Stones area would be the best option.[7] The work was interrupted by World War II and then revived in 1945 when engineers predicted an output of 2.2 terawatt hours (TWh) per year.[8] A further government study looked at barrage options in 1948 and estimated the construction costs at £60 million.[6] By the time of the next study in 1953 the estimated cost had risen to £200 million.
In 1971 a report by Dr Tom Shaw, a tidal Power expert and advocate proposed a barrage from Brean Down to Lavernock Point. The scheme was estimated to cost £500 million.[9] In 1975 the Central Electricity Generating Board (CEGB), published a study with evidence from Bristol and Salford universities for the Secretary of State’s Advisory Council on Research and Development for Fuel and Power.[10] As this was the era of cheap oil, the council established that a barrage could not be economically viable unless the energy situation deteriorated significantly.

[edit] Bondi Committee – 1981

Proposed location of Bondi Committee Barrage
After just such a deterioration (due to the Iranian Revolution and 1979 energy crisis) the plans were reinvestigated by the Severn Barrage Committee in 1981. This committee was known as the "Bondi Committee" (after Professor Sir Hermann Bondi). The committee investigated 6 possible barrage locations, from English Stones at the top of the estuary, down to a location largely at sea in the Bristol Channel between Lynmouth in North Devon and Porthcawl in South Wales. It produced a major energy paper,[11] which recommended a 10 miles (16 km) long barrage of concrete powerhouse between Brean Down and Lavernock Point, sluice and plain caissons together with sand and rock-fill embankments. It would have generated 7,200 MW on the flow of the tides (the largest barrage considered could have produced double that power output). This set of plans was strongly built on a few years later by the Severn Tidal Power Group.
In 1984 Wimpey Atkins proposed a smaller barrage at English Stones, in the hope of creating a smaller more economically viable project that would avoid the environmental impact of a large barrage.[12]

[edit] Hooker or Shoots Barrage – 1987

Cross section of Shoots Barrage turbine housing
This Wimpey Atkins 1984 study was criticised because it did not tackle the issue of silting and in 1987 Arthur Hooker OBE (a former partner of WS Atkins) in conjunction with Parsons Brinckerhoff prepared a revised barrage proposed at English Stones to better tackle this issue.
Parsons Brinckerhoff further updated their earlier proposal in 2006 and current estimates for this barrage (now known as the "Shoots Barrage") would cost £1.4 to £1.8 billion to build, and generate 2.75 TWh of power per year.[13] At the highest tidal range, it would develop a peak output of 1,050 MW, and 313 MW output on average throughout the year.
Cross section of embankment
The barrage would be located just below the Second Severn Crossing – i.e. above Cardiff and Bristol on the estuary – and so much smaller locks would be needed for upstream access to Sharpness and Gloucester docks as the large ports of Portbury and Avonmouth would be unaffected.
Like the STPG proposal, Hooker generates only on the ebb tide. Construction time would be four years. It would be built of rock fill embankment at the coastal sides (more like the proposals for "Tidal Lagoons"), but like the STPG would be sluice caissons and turbines with powerhouse in the middle section.
In April 2009 the Liberal Democrats produced a report called "A Tidal Solution - The Way Forward" [14] that backed the Shoots Barrage along with a number of additional measures for power generation in the Severn Estuary. In September 2009 the report was adopted by the Lib Dem party conference as official party policy.[15]

[edit] Severn Tidal Power Group – 1989

The £4.2 million study by Severn Tidal Power Group (STPG) built on the work of the Severn Barrage Committee, but also examined other possible barrages, and produced another major energy paper.[16] They concluded that the 1981 plans were the best location for a barrage, but calculated that the power output could be larger, at 8,640 MW during flow, or 2,000 MW average power. This would provide 17 TWh of power per year (about 6% of UK consumption), equivalent to about 18 million tons of coal or 3 nuclear reactors. The cost in 1989 was calculated to be about £8 billion (£12 billion in 2006 money – about the same as six nuclear reactors, but different lifespan), and running costs would be £70 million per year (about the same as 1.5 nuclear reactors).[citation needed]
Diagram of the STPG Barrage
The barrage would use existing technology as used in the Rance tidal barrage in France, the Annapolis Royal Generating Station in Canada and the Netherlands sea barrages. Power would be most efficiently generated only in the flow direction, and this effect on tidal range would mean that the tidal extent would be halved by losing the low tide rather than the high tide. That is, that the tide would only go out as far as the current tidal mid-point, but high tides would be unaffected (unless the barrage was deliberately closed to prevent flooding).
Construction in prefab caissons
The barrage would contain 216 turbines each generating 40 MW for the 8,640 MW total. Arrays of sluices would let the tide in and then close to force it out through the turbines after the tide has gone out some distance outside the barrage. This deliberate building of a head on the water builds pressure that makes the turbines more efficient.[citation needed]
The barrage would contain a set of shipping locks, designed to handle the largest container vessels. Construction would take about eight years and would require 35,000 employees at peak build time. The minimum lifespan of the barrage would be 120 years (about three times that of a nuclear reactor), but could easily be 200 years if decent maintenance was performed.[citation needed]
Artist's impression of aerial view of STPG Barrage
The STPG appraisal concluded that the electricity generated from the barrage would make the scheme economically viable if given certain "green" advantages, and that the environmental impact was acceptable.[citation needed] Margaret Thatcher's government did not accept this, and shelved the plans. However, since then global warming has radically altered the public perception of environmental damage; and soaring oil, gas and energy costs have made the economics of the barrage much more favourable.
The advent of renewable energy discounts favours electricity generated from "green" sources; and in addition, much lower interest rates make the cost of loans much lower, and long-term financing of such massive projects is now more viable. Consequently, there have been renewed calls for these plans to be re-appraised.

[edit] Severn Tidal Reef – 2007

Evans Engineering (Joseph Evans & Sons Limited) have released plans for what they call a Severn Tidal "Reef".[17] This is a novel structure which aims to overcome the environmental side-effects of a barrage, and can be conceptualised as being half-way between a barrage and a tidal "fence" (a linked string of tidal-stream turbines). The designer, Rupert Evans, had previously worked on a tidal fence proposal, but since dismissed it as unworkable. The reef reduces environmental impact by working with a much smaller "head" of water—just 2 metres (6.6 ft)—thereby reducing the impact of the structure on the estuary water and flow. The smaller head means that the water velocity is much lower and more lower power turbines are required. The load factor will be higher, partly because of the generation being both ebb and flow and the total energy output should (according to a recent report by W.S.Atkins commissioned by the RSPB) be significantly greater than for the Cardiff-Weston Barrage, and is in part a result of siting the structure at the "outer" Minehead to Aberthaw line, which roughly doubles the volume of tidal water available.[18]

[edit] Sustainable Development Commission – 2007

On 1 October 2007, the UK's Sustainable Development Commission (SDC) published a report looking at the potential of tidal power in the UK,[19][20] including proposals for a Severn barrage. The report draws on a series of five evidence-based reports, one of which summarises all the available evidence from previous studies on a number of Severn barrage options, but focusing on the Cardiff-Weston and the Shoots schemes. The SDC also commissioned a programme of public and stakeholder engagement, which included a national opinion poll and a series of local and regional workshops.[21]
The SDC gave its support to the building of a Severn barrage, providing a number of strict conditions were met. These include:
  • A Severn barrage should be publicly led as a project and publicly owned as an asset to avoid short-term decisions and ensure the long-term public interest
  • Full compliance with the EU Habitats and Birds Directives is vital, as is a long-term commitment to creating compensatory habitats on an unprecedented scale
  • Development of a Severn barrage must not divert Government attention away from much wider action on climate change
The SDC also raised the challenge of viewing the requirement for compensatory habitat as an "environmental opportunity", through the potential to combine a climate change mitigation project with the adaptation that will be required to respond to the effects of climate change. A publicly led project would enable the use of a low discount rate (2%), which would result in a competitive cost of electricity, and would limit the economic impact of even a very large-scale compensatory habitats package. Electricity production costs are not competitive if a commercial discount rate is applied.

[edit] UK Government study announced – 2007

A two year feasibility study was announced in late 2007,[22] a the terms of reference were announced on 22 January 2008,[23] following the publication of the Turning the Tide report from the Sustainable Development Commission. This study builds upon past studies and focuses on a variety of tidal range technologies including barrages and lagoons, and innovative designs such as a tidal fence and a tidal reef in the Severn estuary.
The study, previously lead by John Hutton, Secretary of State for Business, Enterprise and Regulatory Reform, is now being lead by Ed Miliband, Secretary of State for Energy and Climate Change.
The study aims to gather and assess evidence to enable the Government to decide whether it could support a tidal power scheme in the Severn Estuary and if so on what basis. Key work areas involved are:
  • The environmental impacts on biodiversity and wildlife; flood management; geomorphology; water quality; landscape and compensatory habitat;
  • Engineering and technical areas such as options appraisal; costs; energy yield, design and construction, links to the National Grid and supply chain;
  • Economic considerations – financing; ownership and energy market impacts;
  • The regional social, economic and business impacts;
  • Planning and consents – regulatory compliance; and
  • Stakeholder engagement and communication.
The feasibility study concluded its first phase when a public consultation was launched on 26 January 2009. The consultation covered a proposed short-list of potential tidal power project options from an initial list of 10 schemes, processes that were undertaken during shortlisting and the proposed scope of the Strategic Environmental Assessment (SEA). The SEA is a formal environmental assessment of plans or programmes which are likely to have significant effects on the environment.[24] A consortium led by Parsons Brinckerhoff (PB) has been appointed to manage this part of the project. The process is guided by a stakeholder steering group. The study will culminate in a full public consultation in 2010.[25]
In July 2009 the Government response to consultation confirmed detailed study would be carried out in the second phase on the 5 schemes that were proposed for short-listing in January. It also announced work to bring forward 3 further schemes that are in the very early stages of development. In September 2010, The Observer reported that the government intended to rule out the possibility of public funding for a complete barrage, while recommending that further feasibility studies be carried out on smaller projects.[26]

[edit] Economic impact

[edit] Power generation potential

The Severn Barrage plans would provide a predictable source of green energy during lifetime of the scheme, 5% of the UK's output from the 10-mile version.[27] This could reduce the cost of meeting UK’s renewable energy targets, and help the UK to meet such targets, including those to tackle climate change.[19] This is because of the few carbon emissions associated with the plan, because unlike conventional power generation, the Severn Barrage plans do not involve the combustion of fossil fuels. A consequence of this plan is that the carbon payback time—the time it takes for saved carbon emissions (those produced by generating the same amount of power in other ways) to outstrip those produced during construction— could be as little as four-and-a-half months, although likely to be around six.[28]
It could continue to operate for around 120 years,[19] compared with 30–40 years for nuclear power plants.[29] An additional benefit would be to improve energy security.[19]
However, although power supply is predictable, peaks in generation from the barrage do not necessarily coincide with peaks in demand. There are two major tidal cycles affecting power output:
  • semi-diurnal cycle: the familiar daily rise and fall of the sea with a full cycle every 24 hours and 50 minutes, with two high and low tides, giving maximum power generation opportunities a few hours after each of the two high tides;
  • spring-neap cycle: a 29.5 day tidal range cycle with the lowest power days producing about 25% of the power of the highest power days.[30]
Just under eight hours per day of generation time is expected.[30]
This cyclic power generation pattern could negatively affect economics and efficiency of other power generators and additional power transmission lines that will only be cyclically utilized.[citation needed]

[edit] Construction costs

The estimated costs of the most recent plans are huge. Figures are as high as £23 billion.[31] Recent studies [32] have suggested that the smaller short-listed options could be privately financed, and so in effect the matter of cost and risk becomes a private one between the building consortium and their banks. Schemes of the scale of Cardiff-Weston are likely to require significant Government involvement. If the banks feel that a smaller project is viable and decide to lend the money at an acceptable cost of finance then the projects will go ahead (subject to planning and other approvals). None of this cost would directly fall on the tax-payer but any support mechanism for the tidal power would be likely to fall on consumers. There would though be secondary knock-on costs from the tidal power project that might be met by the tax-payer, such as modifying existing ports, provision of compensatory habitat and dealing with environmental change. However, these would be offset by the positive knock-on effects, such as flood protection - which would have otherwise also cost tax-payer money. Whether the parties actually decided to exchange money for these knock-on effects would be a matter for Government negotiation.

[edit] Local impact

Any large-scale barrage would create leisure-friendly water conditions behind it. Flood protection would be provided by the barrage, covering the vulnerable Severn estuary from storm surges from the sea. New road and/or rail transport links could be built across a barrage if demand rises in the future, as outlined below. Any barrage could provide a boost to the local economy — construction industry in the short term, tourism and infrastructure in the long term.[33]
However, shipping would have to navigate locks, and existing estuary industries, including fisheries, would be damaged and jobs lost. All industrial discharges into the River Severn (e.g. from Avonmouth) would have to be reassessed.[citation needed]

[edit] Environmental impact

The Severn Estuary is a Special Area of Conservation due to the European importance of its ecology. The inter-tidal area provides food for over 85,000 migratory and wintering water birds, and represents 7% of the UK's total estuaries.[34] There are nature reserves and Site of Special Scientific Interest (SSSI) on the islands of Flat Holm[35] and Steep Holm.[36]
The Barrage was not supported in the 2003 Energy Review due to "strong environmental concerns" (The same paper also described nuclear power as "an unattractive option").[37]
The RSPB opposes any Severn Barrage because of the effect it will have the feeding grounds 85,000 birds depend on, stating "The impact a barrage would have is huge. This is one of the most important sites in the UK for wild birds and the chances of them surviving if it went ahead are fairly slim. There wouldn't be enough room left for all the birds and there wouldn't be enough food for those that remained. The estuary is one of the UK's most important sites for water birds and its wildlife value must be taken fully into account."[38]
Possible effect of turbidity reductions in Severn Estuary
The present strong tidal currents in the estuary serve to lift up silt sediment and so keep the water thick with fine particles. This blocks light-penetration and means that the Severn Estuary marine environment is actually a relative desert, in terms of both plant and fish life.[39]
The barrage will not create a "lagoon" - as both opponents and supporters have sometimes claimed. Tidal power stations by definition require that the tide flows through the barrage, but the tidal range in the Severn would be halved.[38] There are claims that the migration of fish would be hampered, but these are contested. The Severn bore would also be weakened or eliminated. Any barrage would be likely to stimulate coastal erosion in some areas, and create a negative visual impact upon the landscape (subjective, similar to wind turbines). There would also be negative consequences of the huge amount of concrete (and other materials) needed, with the quarrying of stone likely to impact on other areas.[citation needed]
DEFRA claims that the environmental effects of the barrage still need more analysis before final conclusions can be drawn. The Sustainable Development Commission is investigating UK tidal resources, including tidal power in the Severn Estuary and its environmental impact, and should report mid-2007.[40]

[edit] Tidal lagoon alternative

Friends of the Earth support the idea of tidal power, but oppose barrages because of the environmental impact. They have proposed their own plans based on the concept of tidal lagoons,[41] whereby man-made lagoons in the estuary would fill and drain through turbines. Their proposals would include lagoons covering up to 60% of the area covered by the barrage, which in some smaller configurations would not impound water in the ecologically sensitive inter-tidal areas of the estuary. The lagoons could be sub-divided so power would be generated at more states of the tide than a barrage, with lower peak output, giving economic advantages to set against the higher construction cost of longer barriers. This idea is based on a prototype now being designed at Swansea bay. However leading figures in the construction industry are sceptical that the lagoons can be economic.[42][43]
A set of Tidal lagoons known as the "Russell Lagoon concept" were studied and dismissed by the 1981 Bondi Committee report, rejected on the grounds of both economics and environmental damage. Studies suggested that tidal currents around and between the lagoons would become extremely fierce and damaging.

[edit] Effects of different site locations

One of the complicating factors in assessing the impacts of a barrage is the large number of possible locations and sizes for the barrage. Generally, the larger the barrage the bigger its environmental impact, and the bigger the amount of energy it could create - and therefore the bigger carbon offset it could have by way of its renewable power generation.
The largest barrages (sited beyond Hinkley Point and towards Minehead on the English side and Aberthaw on the Welsh side) would significantly affect the entire Severn Estuary and much of the Bristol Channel, but could generate 15 GW peak power and protect the whole of the Somerset levels against flooding and sea-level rise caused by Global Warming. The smallest barrages (sited at Aust/Chepstow) would affect only the river and estuary in Gloucestershire, but would also only generate perhaps 0.75 GW peak power.

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