Jornal Socialista, Democrático e Independente dirigido por Dieter Dellinger, Diogo Sotto Maior e outros colaboradores.
Domingo, 21 de Setembro de 2008
Pelamis Snakes


These extraordinary metal snakes, the length of football pitches, are making up the world's first commercial wave farm in a little town just north of Porto.


Portuguese surfers keeping an eye on the weather will be joined this month by engineers and businessmen, but they will be hoping for very different reports. The men and women behind the latest renewable energy project will be looking for a flat, calm sea.

Portugal is poised to open what will be the world's first commercial wavefarm, and while the coastline's formidable surf will be a source of electricity, the engineers need a decent "weather window" to be able to get their machinery out to sea.

The Pelamis machines, named after the Latin for sea snake and developed by a Scottish company that leads the world in one of the newest renewable energy fields, are a series of red tubes, each about the size of a small commuter train, linked together, and pointed in the direction of the waves. The waves travel down the tubes, causing them to bob up and down, and a hydraulic system harnesses this movement to generate electricity.

The three "sea snakes" will soon be towed out to a spot some three miles from the coast of northern Portugal at Agucadoura, from where the electricity they produce will be pumped into the national grid.

But the hi-tech venture has not been without its problems. The latest date for inauguration of the wavefarm was to be Wednesday, but a combination of bad weather, bad luck and the pitfalls of developing any new technology has meant the machines are still on dry land, awaiting the next calm spell to be taken out to sea.

The machines were designed and built in Scotland by Pelamis Wave Power (PWP), but it took the intervention of the Portuguese to give the project real impetus. The renewable energy company Enersis ordered the wavefarm, recognising that it would not initially be profitable, and the Portuguese government has set tariffs for wave energy well into the future, ensuring that profitability is not the key question. "What we are assembling here is the first wavefarm in the world," says Antonio Sa da Costa of Enersis, and that is not without risk. But Portugal is the ideal testing ground: it has a long coast compared with its size of population and resources, and, with the government's support, developers are keen to invest.

Enersis had planned to expand the Agucadora wavefarm to 30 machines next year, but the setbacks forced it to scale back its aims. If progress in production, development and installation can match its ambitious plans, Enersis would like eventually to have several hundred machines floating off the coast to produce 500MW of electricity. That would be enough to light up 350,000 homes and, Enersis claims, for the whole project to become profitable.

Max Carcas, PWP's business development director, says the company expects to improve efficiency once the system is operating: "Typically costs fall by some 15% for each doubling in installed capacity."

But Teresa Pontes, of the National Institute of Energy, Technology and Innovation in Lisbon, believes it is too early to be sure that these systems will work and be taken up around the world. She is positive about the potential for wave power in Portugal because of its geography, but compares the current state of the technology with that of wind power a decade ago. "Wind energy is a simpler technology than wave power - and it took many years for that to mature.

"Research needs to be continued. Maybe the best system has not been deployed yet - if you think of the first aeroplanes, they are very different from what we use now."

As PWP struggles to get its machines into the water, competitors are springing up. While PWP has signed deals to provide sea snakes for projects off the coasts of Cornwall and Orkney, other models are being developed. A Canadian company is assembling a project based on buoys that it hopes will harness waves off the coast of Oregon. In Australia, a system of buoys tethered to the sea floor has been undergoing tests for years.

But Portugal's enthusiasm for renewable energy has given impetus to wave power. The Socialist prime minister, Jose Socrates, recently increased the country's renewable energy target for 2010 from 39% to 45%. Until now Portugal has relied mainly on wind power, but it will eventually run out of land for the windmills and needs the sea if it is to meet its target.

EU current account Top generators

This year the EU set a target of increasing the share of electricity produced by renewables from 6.5% to 20% by 2020. European commission figures show that only 2% of Britain's energy use came from renewables in 2004. Germany has 200 times as much installed solar power and 10 times as much wind power as Britain.

Wind power set records in 2006, the European Wind Energy Association reported, as 7,588 MW of capacity was installed, a 23% rise on 2005. Germany, the world's wind-power leader, had 20,000MW of installed capacity; Spain was second. The UK has 40% of Europe's wind resource but is only seventh in the world in installed capacity.

Marine power One of the world's largest tidal projects was recently unveiled off Orkney. A wave hub off the coast of Cornwall this month gained planning approval and could generate electricity for 14,000 homes.

Solar In March the first commercial concentrating solar power plant in Europe was inaugurated in Seville. When completed in 2013 it will produce enough energy for 180,000 homes. According to industry estimates only 20,000 homes in the UK have solar panels.

Biomass The EU meets about 4% of its total energy needs with biomass. Its share the energy mix varies from 1.3% in the UK to 29.8% in Latvia.

Made in Scotland, but it's a Portuguese consortium, led by Enersis, who are to build the world's first commercial wave farm off the north coast of Portugal. The initial phase will consist of three Pelamis P-750 (750 kW) machines, giving a total installed capacity of 2.25MW at a cost of £8 million. If all goes well, the number will be boosted to 30 or 40 machines.

The Pelamis prototype has been operating at the Orkney test centre since August 2004. No major issues of durability or corrosion were found during the staged test programme over the year. The US Electric Power Research Institute (EPRI) have given it a positive independent assessment, considering that it's the closest to commercial delivery of current wave energy machines. Read the EPRI report here

The EPRI assessment for the US government envisages tens of GW wave energy off shore for Massachusetts and other states. Wave energy has the potential to become one of the lower cost forms of generation in the longer term, it is believed. Ocean Power Delivery who have developed Pelamis say the power from the Portuguese installation will be a quarter the current cost of solar photovoltaic power and half the cost of the first wind power machines.

Each Pelamis 'snake' is made of four segments, hinged both horizontally and vertically, to permit sideways and up-and-down movement. Each segment in the P-750 will be similar in size and length to a train carriage. When it's bent and twisted by the waves, pistons force oil through hydraulic chambers connected via valves to give a smoothed flow that drives a dynamo generator.

The Pelamis snake is moored to keep it head-on into the waves. Survivability is vital so the design allows Pelamis to dive through storm waves that are ten times higher than the average waves (100 times more power). Efficiency is quite low, under 10%, but that is not so important when the waves off Atlantic facing coasts carry some 60kW per metre.


Picture from Ocean Power Delivery, whose website gives further information.


publicado por DD às 22:23
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