Innovations In Wave Power

Interview conducted by G.P. ThomasJul 8 2012

In this interview Dr. George Taylor, Executive Vice Chairman of Ocean Power Technologies, talks to AZoCleanTech about recent advancements in wave power and why it is such a beneficial renewable energy resource.

Could you please provide a brief introduction to the industry that Ocean Power Technologies, Inc. works within and outline the key drivers?

Ocean Power Technologies, Inc. is a wave power engineering company. We started operations in 1994 and we are convinced that ultimately wave energy has all the attributes that would allow it to be the most economical of all renewable energy sources. Because the energy is so concentrated in waves, the cost of energy compared to wind or solar will be ultimately less. When built in volume production, wave energy will be competitive with fossil fuels.

Could you please give a brief overview of Ocean Power Technologies, Inc.?

Our business plan is to build turn-key wave power stations and then to sell these power stations to utilities or to independent power producers. We are builders of stations that are based on our unique technology.

We have done several things that I believe put us ahead of our competitors. For example, we were the first wave power company to connect to the United States grid, which we did under a Navy contract in Hawaii at their marine base.

What are the benefits of using wave power over conventional energy sources?

It is renewable and non-polluting. You can use the argument about reducing climate change, which a large number of people believe is happening, but even if you take that out of consideration the pollution issues that one sees in the USA and in Europe are tremendous.

Health issues are ever increasing, with asthma very prevalent now compared to 30-40 years ago. The pollution of fossil energy and its effect on human health is almost as big an issue as climate change.

Beside this, an important advantage is that wave energy is predicable. You can tell hours ahead, or even weeks ahead what the wave energy is going to be before it reaches the wave power station.

The wave power station is typically built several miles offshore. The waves build up as they cross the oceans of the world. Using satellites and various types of sensors you can very easily monitor the wave energy. So it is completely predicable, you know exactly what you are going to get! This also means that the grid operator always knows what to expect. This cannot be done with wind or solar.

Another big advantage is that a large percentage of the world’s population live by the coast, meaning that along the coast there is a great need for energy.

So when you bring wave power ashore, you are immediately able to connect into the power grid and not need long transmission lines like you do in Texas for example, where the wind energy is very good, but not many people live in the vicinity.

How does a wave energy converter work?

There are 3-6 ideas currently being proposed for wave energy converters, but I will only describe the Ocean Power Technologies, Inc. system. Our PowerBuoy system is very similar to a navigation buoy, the buoys that bob up and down on the waves. There are two parts to the PowerBuoy: one part is a long 30 meter vertical tube, most of which is submerged below the surface. The second part is a doughnut-like float with a hole in the middle of it. That float slides up and down on the narrow diameter of the tube that I described.

The tube remains relatively stationary because on the bottom we have a heave plate that acts like a sea anchor. That relative motion is coupled by a bridge on the top which drives a drive shaft in and out of the tube. So a mechanical stroking occurs and that is how we capture the wave energy and convert it into a mechanical energy.

Inside the long cylinder the mechanical stroking is converted into a rotary motion, which turns a conventional 3-phase AC generator and produces the electricity.

A PowerBuoy wave energy converter in the ocean. Image Credit: Ocean Power Technologies

How is the Ocean Power Technologies, Inc. PowerBuoy system unique in the wave energy sector?

The unique part is that we can electrically tune the system to maximize the energy out of the waves which are random in both amplitude and frequency.

The tuning has been one of our major advances in making wave power efficient: it is achieved automatically in the buoys using a computer-controlled system.

The grid compatible electrical power from an array of PowerBuoys is fed into an underwater substation that is connected via an underwater armoured cable to the ground.

Does Ocean Power Technologies, Inc. receive independent test of their technology?

We had our system certified by Lloyds Register to make sure the system could withstand ‘100 year’ storm waves forces. Our utility scale systems were found to be able to stand a 24m wave, which is extremely powerful!

Furthermore, we’ve had systems in the water going back to 1997 which have survived hurricanes and even tsunamis.

Recently, we have been given a technical readiness level of 7/8 by the US Department of Energy, which is the last step before full commercialisation. We have several projects which we hope will demonstrate full-scale commercialisation very soon.

Will the PowerBuoy have any adverse effects on the local environment?

No. In Hawaii there was a full environmental permitting process done by the Navy. We found that the native Hawaiians used to bury their dead in the surf where we had to lay the cable, so there were special precautions taken so that we didn’t disturb any ancient burial sites. There was a finding of ‘no significant impact’ by the Navy, and we have also gone through the same process in Oregon.

Basically, the system is environmentally benign and in fact fish see the buoys as artificial reefs, and so it has become a fish haven!

Where are Ocean Power Technologies Inc. primary projects located?

Currently the main focus is in Oregon, where we have received a permit to put the first buoy in the ocean later this year, and we are about to receive a permit to expand this from 1 to 10 buoys, and connect to the grid.

Are there any new projects planned in the near future?

We have a 19 MW project planned in Victoria, Australia and a project in Spain. We also have a berth at the Wave Hub in Hale, Cornwall and a relationship in Japan.

How do you see the future of wave power progress over the next 10 years?

We believe that wave power will very soon be demonstrated at a commercial level by Ocean Power Technologies, Inc. For us, it a straight forward process to expand as we can mass produce PowerBuoys and continue to decrease the cost of electrical energy generated.

It creates industry building jobs, and the buoys can be easily transported. Deployment is much easier than, for example, offshore wind.

Wave power is expected to reach cost parity with wind in about 2-3 years and will soon thereafter become competitive with conventional energy sources.

The construction of a wave energy converter. Image Credit: Ocean Power Technologies.