Marine sources to meet energy challenges

By Jeanne Erdmann

This article originally appeared in the September 2007 issue of IEC e-tech.

Recently, iec e-tech discussed wind and tidal energy systems with Ken Street, business manager of offshore energy systems at Converteam Group SAS, a private company with 3 800 employees in 16 countries. Converteam began operating in 1889 as a General Electric Company (GEC) and in 2005 the company became a private company. It manufactures rotating machines, drives to control the speed of motors and automation and process controls. It works with device developers in undersea power collection and distribution modules on wave farms while offshore systems transform energy gathered from thousands of waves into grid compliant power. Converteam is now choosing people from its staff to participate in the work of Technical Committee 114.

How will marine energy contribute to helping reduce CO2 emissions?
A look at EU directives shows the enormous scale of establishing marine technology as a renewable energy source. The EU target for renewables is 20% of all energy by 2020. To clarify, this is not just electricity. The target includes bio diesel and hydrogen cars; so electricity represents 35% of this target. By the year 2030, power consumption is set to increase by 50%, by which time half of existing power stations (coal and nuclear) are scheduled for decommissioning. Currently in the UK about 5% of our electricity comes from wind and the target is 10% by 2010.

How did Converteam join the wave and tidal energy market?
The first project was OSPREY in 1995. This was an oscillating water column device rated at 2MW. It consisted of a steel structure with a false beach, the waves moved in and out of it and the piston effect forced air backwards and forwards through air turbines that spin in the same direction irrespective of airflow direction. The intention was that it would be towed to the site and ballasted down to sit on the seabed with the working parts above the surface. It worked well in all respects but sank during the towing operation.

In 2002, Archimedes Wave Swing (AWS) designed a unique wave device of the point absorber type. It sits, submerged, on the seabed and contains a linear generator that directly converts reciprocating wave motion into electricity. Converteam built the generator and power conversion system.

How are these devices funded?
It is very difficult to get funding to bring prototypes to market. Venture capital sees this as too risky; where government funding is available, it is insufficient and too thinly spread to be effective. Any quick web surf will pull up countless device developers. These range from people with a limited understanding of the basic physics with which they are involved and will not succeed, to those who have got a good idea and are struggling to make progress because of funding/resource problems and those lucky ones who have managed to get their idea recognized and have found money either privately, from government grants, or from flotation on the stock market and are starting to win small orders.

Early flotation devices some years ago, where perhaps investors' expectations were too high, made it more difficult for new developers to get interest in the city for new flotation devices. As a positive example, Ocean Power Technologies are an exception in that they have just successfully concluded a second round of funding from the markets. But they now have a track record of devices with running hours on them to boost confidence.

Of the three wave devices – oscillating water columns, point absorbers, and overtopping – which are still in R&D?
I think it’s fair to say that even with full-scale technologies operating, all devices are all still in the R&D stage. Yes it’s out of the lab but certainly not a commercial "off the shelf" product with all the implications inferred by that phrase. I can only comment as an outsider, actual results will be covered by confidentiality, but I think it would be true to say that the answer is likely mixed. Some problems have been solved but many still remain. Power performance expectations are now becoming more realistic.

How does Converteam work on the mechanics of the device with developers?
We try to find developers, or they find us, and we determine if what they are doing makes sense from a practical point of view. It’s easy to have an idea for a wave device that works well in the bath but you can see right away that it could never scale up and become practical. The main criterion for a wave or tidal device is that it has to survive extreme weather conditions. A device needs to be 100% efficient and survive winter. Other concerns are costs; if it won't scale up to a multi-megawatt farm then it's not going to make it. Our marine and mechanical engineers can fairly quickly assess the likely potential for a device to simply survive. They will also assess the likely maintenance issues. Maintenance on a device above or below the sea is very expensive. Electrically, we will evaluate the total system from the generator right through to the grid connection. This involves mathematical modeling both as a single unit and as a farm to making sure it can work as a "power park".

How do wave farms fit into the tidal energy picture? 
Wind is huge but wave and tidal will be a lot bigger – it has to be because there are simply not enough places to stick wind turbines up and wind’s intermittent nature makes the predictability of the tides and waves ideal for power generation. Wave farms are complex because of the nature of the raw energy. Small wave farms are also being built in Spain and others are planned for Portugal, France and the US. The UK’s first wave farm is being built off the Cornish coast, rated at 20MW this will allow wave developers to trial the operation of multiple devices working together to supply a meaningful amount of power into the grid.

How will Converteam contribute to marine energy both now and in the future?
We currently have about 10% of the world market for electrical systems in renewables, the majority being wind. We are the largest exporter of such systems in the UK and we want to gain a similar position with wets – we want to supply the electrical systems for individual devices as well as the infrastructure for farms. Our marine and electrical systems knowledge is world leading and we truly believe we have a great deal to contribute in this particular field.

Source: International Electrotechnical Commission (IEC).