Block’s Indicator of Sustainable Growth

by Ray Block

Back in 1799, two French inventors, the father and son Girard took out a patent to harness tidal power to produce energy. Nothing came from their dream, and it took a further 209 years to commercialise tidal power.

Enter three innovative researchers, Richard Yemm, Dave Pizer, and Chris Retzler, who in 1998  wanted to find a way. where wave energy could be harnessed to make electricity. After all, wave energy is essentially stored as concentrated wind energy, where the waves are being created by the progressive transfer of energy from the winds, as it blows over the surface of the water.

So they developed the Pelamis Wave Energy Converter, so named after the legendary yellow belly Pelamis of sea serpent fame. They eventually designed a semi-submerged articulated structure composed of cylindrical sections linked by hinged joints. The wave-induced motion of these joints is resisted by hydraulic rams, which pump high pressure fluid through hydraulic motors via smoothing accumulators.

The hydraulic motors drive electrical generators to produce electricity. Power from the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together, and linked to shore through a single seabed cable. The Pelamis structure is 140 m long and 3.5 m in diameter, with three power conversion modules per machine. Each machine is rated at 750kW, and provides sufficient power to meet the annual electricity demand of approximately 500 homes. 

Depending on the wave resource, machines will on average produce 25-40 per cent of the full rated output over the course of the year. And so was born an energy company with a difference. With almost 40 million pounds of venture capital, and after teaming up with infrastructure funds, what emerges is the Agucadoura electricity project in Portugal. 

In the first phase, Pelamis Wave Energy, with a total investment of about nine million euros has three Pelamis energy wave converters moored three miles off the Portuguese coast supplying electricity to Agucadoura. This is being supplemented with a further 25 Pelamis machines, which will increase electric generating capacity to 21 MW, enough to power a town of 15,000 households. In the total project, Pelamis Wave Power has a 23 per cent interest.

EDP, which is a partner with Pelamis Wave Power is the third energy supplier in Spain and Portugal, with a strong position in the Brazilian energy market. EDP is also the fourth largest wind energy producer world-wide after acquiring Horizon Wind Energy, which has 17 wind farms in the US.

The Pelamis wind project in Portugal benefits from a special feed in tariff, established by the Portuguese Government to subsidise the first wave energy installations. The tariff of  25c/kWh is higher than provided to wind energy, but below that provided to solar energy, now relatively mature technologies which have enjoyed significant cost reductions over time through volume production.

Pelamis Wave Power plans to start installing its machines in the UK, commencing off the coast of northwest Scotland, with 3MW of wave power and in the south, 5 MW off Cornwall. The Cornwall installation will be one of four wave power facilities plugged into a single 20 MW underwater transformer at a site called “Wave Hub.”

The leading US wave energy researcher, Roger Bedard, who heads ocean energy research at the US utility funded Electric Power Research Institute(EPRI) is very enthusiastic about the potential for wave power. An article in Yale University’s Yale Environment 360 by John Luoma quotes Bedard as saying “there’s plenty of reason for optimism about the future of wave power. Within a decade, the US could realistically meet as much of 10 per cent of its electricity needs from this source.” He expects wave power will go the same way as wind energy, which in the US after a substantial increase in installed capacity went from a price of 50 cents a kilowatt hour in the 1980s to 7 cents, about the same price as natural gas, and only about 3 cents dearer than coal-generated electricity.

Another wave energy company, Ocean Power Technologies (OCP) based in New Jersey has designed generators in its PowerBuoys, which works through  a stationary section of the mostly submerged 90-foot buoys anchored to the ocean floor, where a second section simply moves up and down with the movement of sea swells driving pistons, that in turn drives an electrical generator. OPT plans to install its machines off the coast of Oregon in the US north west in 2009.

Another competitor, Verdant Power has designed six turbines which function much like a stubby, submerged windmill, with the blades 16 feet in diameter turning at a peak rate of 32 revolutions per minute. Verdant has high hopes for its facility in New York’s East River, where it intends to have 300 of its turbines working. This is despite the company’s two previous attempts which broke down, because the tides in the East River, which connects Long Island Sound with the Atlantic Ocean were too strong for the blades of the turbines. Verdant also intends to set up an installation on the St Lawrence River.

Another US competitor, Free Flow Power is interested in a number of sites on the Mississippi, south of St Louis.