Change Alley

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Posts Tagged ‘desalination

Green Light For London Desalination

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Boris Johnson paddling a coracleLondon’s new Mayor, Boris Johnson, has dropped a legal challenge to Thames Water’s proposed £200 million desalination plant in Beckton, East London. The High Court challenge was initiated by his predecessor, Ken Livingstone, on the grounds that the project was inefficient and bad for the environment.

Mr Livingstone said cleaner, cheaper and less wasteful alternatives should be found to avoid the “energy-guzzling and carbon-intensive” way the plant was run. According to Times Online, Boris Johnson withdrew the case after Thames Water “promised to introduce a series of environmentally-friendly measures”.

The plant will use reverse osmosis to remove salt from river water. Osmosis occurs between two solutions of different concentrations or strengths. A very fine membrane separating the solutions allows liquid (but not the dissolved solids) to pass from the weak solution to the strong solution.

Over time, the concentration of the two liquids will balance out but pressurising the stronger solution can stop the flow. If the pressure on the stronger solution is increased further the osmotic process is reversed and the liquid passes from the stronger solution making it more concentrated. This reverse osmosis process can be used to remove water from a saline solution (i.e. brackish water) thus providing a desalination technology.

The first reverse osmosis water treatment plant was built in California and started working in 1965. The nice thing about this technology is that it’s highly scalable, suitable for large projects like Beckton, producing enough water for 400,000 homes, right down to small-scale devices like Red Button Design’s ROSS (‘Innovate or Die‘)

According to Thames Water’s FAQ page, the process will be timed to extract water during the three hours leading up to low tide, minimising the salt content to less than one-third that of seawater. This means that the plant will use approximately half the energy required to treat pure sea water, and around 15% of that used by the most energy-intensive thermal desalination plants.

The plant “will use around 6.3MW a year over a 25-year lifespan”. Hmmm, not sure what that means, someone doesn’t know the difference between a megawatt and a megawatt-hour it seems. More work needed, must try harder. Thames Water have “given a legally binding commitment that 100% of the plant’s energy needs will be met from renewable energy”. Options being considered are wind power, and used cooking fat and oil. Initially, however, the plant will be powered by biodiesel, which raises the old questions, where will the biodiesel come from, and what environmental damage will be caused in producing it? I bet it’ll have some palm oil in it.

Interesting how the word ‘sustainable’ doesn’t show up in Thames Water’s information on the plant, it’s all about ‘renewable’ energy, which is more difficult for the green lobby to take exception to. They’re learning.

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Written by Pete Smith

May 13, 2008 at 10:12 am

Africa To Feed Europe’s Energy Appetite

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An article in last Sunday’s Observer (‘How Africa’s desert sun can bring Europe power‘) describes a £5bn plan to generate electricity in the deserts of North Africa and the Middle East, and export it to Europe. More than 100 solar installations, each equipped with an array of thousands of mirrors, would generate enough power to provide Europe with a sixth of its electricity needs.

The Trans-Mediterranean Renewable Energy Cooperation (TREC) is a joint initiative of the Club of Rome, the Hamburg Climate Protection Foundation and the National Energy Research Center of Jordan, campaigning for the transmission of clean power from deserts to Europe. TREC has researched and developed the DESERTEC concept in cooperation with the German Aerospace Center. In Brussels on November 28, former Club of Rome president Prince Hassan bin Talal of Jordan presented a White Paper “Clean Power from Deserts – The DESERTEC Concept for Energy, Water and Climate Security” to members of the European Parliament.

The project aims to exploit cheap desert land using a technique known as ‘Concentrating Solar thermal Power’ (CSP). A CSP installation consists of an array of adjustable mirrors covering around a square kilometre. The mirrors focus the sun’s rays onto a central pillar filled with water. Temperatures inside the pillar rise to 800C, causing the water to be vapourised into superheated steam which is channelled off and used to drive turbines which in turn generate electricity. The residual heat will then be used to power desalination processes to provide fresh water.

White Paper

I found it quite amusing that the Observer can’t tell the difference between CSP and photovoltaics. Or perhaps they just couldn’t find a picture of a CSP site in their archive and thought their readers would be too dumb to notice.

Afterword: Having published this post I went off to do something else, but found myself thinking some more about the TREC scheme. It has interesting political implications if it goes ahead. It seems the next logical step in the process of incorporating North Africa and the Middle East into some kind of Greater Europe. Where will Europe’s southern boundary be redrawn, and how will it be defended? And how will issues of energy supply security be addressed?

I just don’t know.

Written by Pete Smith

December 6, 2007 at 10:51 am