Independent studies carried out in the UK have predicted that conservatively about 7% of the UK's present electricity usage could be produced from tidal stream energy sources. Evopod has been developed to extract energy from the deeper water sites where the water depth is greater than 35m to 40m.

ROGER COX - THE EVOPOD

Roger Cox

EarthToys Renewable Energy Article
Independent studies carried out in the UK have predicted that conservatively about 7% of the UK’s present electricity usage could be produced from tidal stream energy sources. Evopod has been developed to extract energy from the deeper water sites where the water depth is greater than 35m to 40m.
EarthToys Interview – Tidal Power and The Evopod

Roger Cox, Development Engineer


Q: Approximately how many sites around the world are appropriate for this technology to be implemented? Is it hundreds, thousands, tens of thousands or is it even more common than that?

The number of economically viable sites depends on the price of electricity, as power can be produced mere cheaply in sites with stronger tides. We estimate that tidal power from the Pentland Firth in Orkney where the peak spring tide flow rate can be as high as 5m/s would cost about 12 to 15 cents (US) per kWh. There are enough good sites for tidal farms around the UK to deploy between 6 to 9 GW of installed capacity which would equate to between 5000 to 7500 1.2MW Evopod units.

Q: Are certain geographic areas of the world more suited than others for this technology? If so, where?

The UK is particularly well served with fast flowing tidal streams caused by the rise and fall of the tides on the Atlantic Ocean side of Britain and Ireland passing through relatively narrow channels to fill and empty the North Sea and Irish Sea. There are also good areas of tidal stream energy off the east and west coasts of America. Another major source of kinetic energy is the Florida Current which, while not having the same peak flow rates as a tidal stream, is a more consistent source of energy as the current speeds is near constant for much of the year.

Q: What are the main technical problems to be overcome with the project?

Each site needs to be well surveyed so that the power in the water can be estimated. It’s also important to know about the seabed conditions and grid connections. Eddies in the water will need to be handled but, in comparison with wind and wave energy devices, while wind gusts can be very much higher than the average wind speed and storm wave heights can be much bigger than the average wave height, current eddies won’t be much stronger than the steady current.

Q: How big would a 1 MW Evopod be and how much clearance would be needed for safety around the installation?

One MW of kinetic energy is equivalent to 10 square meters of water at 5.8m/s or 100 square meters at 2.7m/s so the size of an Evopod rated at a certain power would depend on the site. Typically a one square kilometer site in an area such as the Pentand Firth to the north of Scotland would support about 40 one megawatt units which would supply about 120GWh per year.

Q: Have you done any economic studies that would show the feasibility of the technology and the proportion of energy load that could be generated using Evopod?

Independent studies carried out in the UK have predicted that conservatively about 7% of the UK’s present electricity usage could be produced from tidal stream energy sources. Evopod has been developed to extract energy from the deeper water sites where the water depth is greater than 35m to 40m. This accounts for over 70% of the sites in the UK and 90% of the more economically attractive sites where the faster flowing waters allow costs of generation from Evopod to be comparable with offshore wind. Ocean current sites are also in deep water (over 250m) where only tethered device like Evopod can be sensibly deployed.

Q: What is the status of Evopod development now and, with funding, how long would it take to get a large scale prototype in place?

It would only take a few months to build a large device but it would be sensible to build something medium sized first. We are currently testing our 1kW unit and have started to develop the design of a 500kW unit for deploying in 2010


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