Two postings from the August and September edition's of IEC's e-tech newsletter by Jeanne Erdmann:

From Portugal to Scotland to the United Kingdom to the United States, countries all over the world are using the pull of the tides and the rhythm of the waves to generate power. In fact, marine energy technology has shown so much recent growth that the IEC is enlisting energy experts worldwide to begin developing standards for wave and tidal energy systems. The IEC’s new Technical Committee, 114, Marine Energy – Wave and Tidal Energy Converters, will facilitate efforts by the International Energy Agency to develop best practices for marine energy. Standards will also help integrate wave and tidal energy converters into the International marketplace, especially as more and more governments mandate efforts for sustainable energy.

Sustainable energy source
World energy demand shows no signs of slowing. Humans now use huge amounts of energy every year. Developing economies continue to grow and thus require more energy. Meeting these energy demands by burning fossil fuels already accounts for most of the human-generated carbon dioxide in Earth’s atmosphere and the worst damage from greenhouse gases. Although clean, renewable energy sources, such as ocean energy technology, won’t clear carbon already in the atmosphere, technology of this sort is more environmentally friendly.

The need for sustainable energy has spurred recent growth in wave and tidal energy systems, explains Ken Street, Business Manager of offshore energy systems for Converteam Group SAS, a company headquartered in France. Converteam supplies electrical system solutions for wave and tidal generation devices of all types. Harnessing the forces of nature for energy is nothing new; windmills have been around for a long time. Using the predictability of waves and tides helps turn those forces into energy grid requirements. “First, wind alone cannot satisfy the targets set by international governments, and second, wind, because of its fickle nature, cannot be allowed to become more than 10 - 15% of the grids' supply. Waves are much more predictable than wind, they are more constant compared to wind. Tidal power is obviously even more predictable than wave and will provide a sizable contribution of the power generated by the sea but wave will dominate - there is just so much more of it,” comments Street.

Oh, buoy. Power!
In general, wave systems have many different devices with different shapes. The movement of the waves causes a design in the device to drive an electrical generator, which then transmits power to shore via a cable. Device designs fall into several categories, explains Street:

1. Oscillating water columns, which are floating or shore based. These columns use wave movement like pistons to push air through a turbine to drive the generator.

2. Point absorbers either float above or below the surface; these represent a popular type of device. Wave motion causes point absorbers to reciprocate, which in turn operates a linear generator that directly converts motion to energy or uses a similar method, such as hydraulics.

3. Overtopping devices can be floating or shore based. For overtopping, waves crash over a ledge and are trapped and return to the sea via a turbine driving a generator.

The amount of ocean real estate taken up by wave devices relates to the amount of power needed. “Like any fuel source, such as coal or oil, which have a certain energy value, waves are no different. So to capture a meaningful amount of power you need to absorb that from an area of sea,” explains Street. Waves have a certain kW/metre, explains Street. For California’s north coast that power translates to 30 - 40kW/m. To extract say 500kW, you need a device around 40m in diameter. The area taken up by the device is also a factor of its anchoring system. How different designs are moored determines how much space they need. Also, spacing needs to account for boat access and to avoid creating an energy shadow for the device behind the craft.

“Yes wave devices are large - they need to be,” comments Street. Although wave power, compared with a fossil fuel, provides low levels of energy, this energy is “free”, self-sustaining and comes in unlimited quantities.

Wave generation systems capture the ocean's
energy and convert it into electricity.

Ocean Power Technologies (OPT), a company based in the United Kingdom, designed the PowerBuoy®, a wave generation system. A 10MW power station needs about 30 acres of ocean area, which accounts for the spacing between the buoys, explains John Baylouny, OPT’s senior vice president of engineering. To determine how many PowerBouys are needed, OPT figures an average worldwide household usage at about 1kW. The 10MW of installed capacity will provide a yearly average of about 3 to 3.5MW of power, he says, so 10MW of ocean power can provide energy for 3 000 to 3 500 homes.

Banking on the tides
On most shorelines the tides go in and out twice a day, and tidal power stations can capture energy from this movement. Initially, the costs of tidal power plants run relatively high compared with other types of power plants but the benefits include low operating and maintenance costs, and, since no fuel is necessary, they do not generate emissions.

Many countries today want to increase spending on alternative energy sources. Korea is looking to the tides for those sources by constructing a tidal power plant at Lake Sihwa, one of several such efforts around the world. A dam built in 1994, secured agricultural water for the region around the lake, helped develop industrial and agricultural lands near the metropolitan area, and secured irrigation water. Unfortunately the dam blocked tidal currents. The rapid increase of population and industrial waste loads from factories in the neighborhood caused the water quality of Lake Sihwa to deteriorate. This pollution though, brought an opportunity. Because of rapid socio-environmental changes and the lowering of water quality in Lake Sihwa, government officials opened the lake to seawater. The Sihwa Tidal Power Station, which is currently under construction, will capture the power of nearby tides by taking advantage of the differing tide water levels between the sea and the artificial lake.

Capturing a world market
The market for wave and tidal power is expected to continue growing. For now, Street explains that the wind market is already mature with many players, growing rapidly with demand outstripping supply. “Wave and tidal power have a long way to go before they achieve a similar position. There are very few devices actually deployed at full-scale and even fewer who can claim to have a fully proven system both technically and from a survival aspect.” Securing funding to bring prototypes to market proves difficult and wind and tidal power are still seen as risky for venture capital. “Those who did manage to raise capital on the share market have had, understandably, an unexciting/disappointing performance, and where government funding is available it is insufficient and too thinly spread to be effective. The enormous pressure for sustainable power will eventually allow more developers to get devices in the water and over the next 5 - 7 years we will see more and more,” says Street.

"Still, wave and energy technologies do have the potential for a large market size — $150 billion a year", says Baylouny.

Photo Credits: OPT, ORECon

Marine sources to meet energy challenges

The IEC recently began recruiting experts worldwide to develop International Standards for its new Technical Committee 114, Marine Energy – Wave and Tidal Energy Converters. The new standards will also help establish marine energy as a competitive form of sustainable electrical energy production and help companies meet government directives for renewable energy.

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 within undersea power collection and distribution modules on wave farms and 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 as 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.

Limpet diagram

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 on the seabed submerged containing 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 of what they are involved with 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.

Pelamis

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".

Archimedes Wave Swing

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 it this particular field.

How will standards support marine technology?
Standards do form an essential part of many of our systems – certainly in the marine and offshore markets. When the standard is written for a specific purpose, for example the International Maritime Organization’s Convention on Safety of Life at Sea, they ensure that all suppliers to that market provide equipment that is fit for that purpose. However, it is just as important to ensure that the standards are suitable and concise. If a classification standard is developed without full consideration of all its implications, then it is possible that it may impose too much of a burden on the design of the equipment to make it technically and economically viable. For marine renewables this will be covered by IEC TC 114.