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."

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.