WAVE POWER TEST

Star of the waves

Just off Denmark’s windswept North Sea coast, a giant robot-like structure towers above the waves. It is the latest addition to Danish wave power development

By Annemarie Zinck

Since 2006, Wave Star Energy’s 1:10 scale wave power machine has been under test in the coastal waters of Nissum Bredning in northern Denmark. It has survived 15 storms, a unique achievement in international wave energy research. But the storms in Nissum Bredning are not severe enough for the ultimate test of Wave Star Energy’s machine.

So in September 2009, a 1:2 scale research section of the wave power machine was installed outside the fishing port of Hanstholm on one of the stormiest stretches of Denmark’s west coast. Followed with great zeal by both the press and the local population, the machine’s four supporting pillars were set in concrete at a water depth of seven metres.

The building of the machine at a shipyard in Poland began in April 2008 with a view to installing it by August 2009, before the autumn storms set in. But building was delayed. And strange as it may seem, the giant machine which needs waves to produce electricity can only be installed in completely calm weather.

Doubts as to whether the installation would succeed were so acute that Wave Star Energy tried to escape press attention, because as the technical director Laurent Marquis expresses it:

”We didn’t want pictures of a capsized machine circulating around the world.”

But on the day itself the sea was mirror calm and the installation passed off without a hitch.

Hanstholm’s new icon arrives in calm conditions on 18 September 2009.

Photo: Wave Star Energy

The Wave Star machine awaits connection to the mainland. A section of the gangway is complete.

Photo: Wave Star Energy

Well protected against storms

Focus Denmark’s visit to the machine takes place on an autumn day when conditions are anything but mirror calm. The sea is grey and turbulent, clouds race across the sky, and not even the pier leading out to the machine is a safe area. So there is no opportunity to see the interesting machine up close.

But there is lots of activity on the beach by the pier. Sparks are flying around a couple of welders who are building a gangway, which when completed will be raised several metres above the tallest waves to enable visitors to get to the machine even in windy weather. Part of the gangway is completed, but it ends suddenly, some height above the pier.

Despite the lack of access to the machine, the welders are not alone on the beach. Windswept tourists are snapping away with their cameras and mobiles.

The Wave Star machine has been developed by two yachting enthusiasts. Their interest in both the sea and renewable energy gave them the idea for the machine, which slightly resembles a centipede. Each leg is a float that moves up and down with the waves. The movements drive pistons which force oil through
a hydraulic system, which runs a pump, which in turn drives a generator. The power output from the machine increases with the size of floats and wave height.

Photos: Annemarie Zinck

In stormy weather, the entire machine is lifted 10 metres above the surface of the sea, so that only the supporting pillars take the force of the waves. The machine is thus well protected against the destructive power of the sea. The floats were raised during Focus Denmark’s visit. Not because the waves were too high,
but because the concrete that the pillars are set in needs to be completely cured before the floats are lowered into the waves.

Towards the optimal machine

The 1:2 scale machine at Hanstholm has been built as a full section of the final machine, but has only two floats. The first commercial machine, expected to be ready in 2011, will be 70 metres long with 20 floats – 10 on each side – each float being 5 metres in diameter.

The primary test areas for the research section are mechanical reliability, including whether the machine can withstand severe storms, and energy production per float. In addition, various types of paint are being tested on the floats. It is important that the paint does not attract algae and crustaceans, and that the floats are easy to clean. The materials used for the construction of the machine itself are also being tested for weather resistance.

The path to creating the optimal machine is long, expensive and full of tests. The optimal Wave Star machine, i.e. the full scale version, will be 140 metres long and will have 20 floats, each 10 metres in diameter. Wave Star Energy hopes that a test section of this machine can be ready by 2015. This will be placed far out at sea; so it is now, while tests are being carried out close to land, that one has the chance to enjoy the sight of the machine from the beach.

The greatest challenges are to produce sufficient electricity to bring the price per kWh below the price for wind power, and to produce enough machines to get production costs as low as possible. Wave Star Energy’s objective is to tackle these challenges within 10 or 15 years.

Aalborg University in Denmark has been involved in several Danish wave energy projects. One of the university’s experts in wave energy is Peter Frigaard, who heads the Department of Civil Engineering.

”Wave Star Energy is today one of the most serious players worldwide in wave energy. The Wave Star machine is a solid product which will definitely have major potential if and when the breakthrough for the wave energy sector comes,” he comments.

According to Peter Frigaard, further development will however require political support, as was the case for Danish wind turbine development.

Wind and waves in harmony

In the lyme grass by the beach, three wind turbines are whirring. Today, power comes from wind rather than waves, but the hope is that in the future, both can produce energy side by side. Wind and wave power supplement each other well, with wave power machines being physically suited to being placed between large offshore wind turbines.

Wind turbines and wave power machines can share many functions such as cabling, foundations, transformer stations and servicing, so there is money to be saved by taking a comprehensive approach to the two energy forms.

Wave Star Energy is collaborating with Denmark’s largest energy company, DONG Energy, on placing a further demonstration machine in one of the large offshore wind farms off Denmark’s west coast. The machine will be a complete 1:2 scale version (70 metres long with 10 floats on each side) and is expected to be ready in 2011.

Do you remember the windmill family?

In the June 2009 issue we brought an article about the Jeppesen family and their windmill. Now you can see the machine and hear an interview with Hans Christian Jeppesen on (LINK will be put it when I get it from Sophie)

In the family’s back garden stands a wind turbine – a Danish produced household wind turbine – which generates almost twice as much electricity as the whole family needs. And quite a lot is needed because in addition to Hans Christian Jeppesen, the family consists of his wife and five children. The wind turbine was installed in autumn 2008 and cost the family a total of DKK 310,000 (EUR 42,000), which they reckon will be recovered in seven or eight years. The wind turbine has a service life of 20 years. The family has calculated that it will save the environment about 20 tons of CO2 annually.

Watch the video: fd.denmark.dk

Photo: Suna Borgaard