BMT Renewables, a subsidiary of BMT Ltd, is part of a consortium that has been awarded a grant of £878,000 from the Department of Trade and Industry (DTI) for a two-year, £1.7 million research, design and development project known as “Pulse Stream 100”. This project will demonstrate a highly innovative, grid connected, shallow water tidal stream power generator in the River Humber (England). Tidal stream energy is not yet as developed as other forms of renewable energy such as wind energy, but has the distinct advantages of being predictable due to the regularity of tides; devices installed to extract tidal energy do not have to be designed to withstand violent storms. They can also be unobtrusive with minimal visual impact.
The ‘Pulse Stream 100’ converter - a device that uses a pair of hydrofoils which will oscillate across the tidal flow - will enable the extraction of tidal energy from shallow water (10-30m mean sea water level), an area not yet exploitable. The Pulse Stream device is the first to target this resource and it will therefore increase the total exploitable tidal current power available in UK waters. Furthermore, this will increase the economic viability of tidal stream energy as such shallow water is typically closer to areas of high energy demand, resulting in lower capital and operational costs.
Pulse generators cause hydrofoils (shown in pale blue in the image) to oscillate up and down like a dolphin’s tail. The mechanical system is very efficient at taking energy from the flow, and transmitting this energy to a generator. The generator is held above the water. This means that wind turbine style generators can be used, and that they are always accessible for maintenance and inspection. The system takes energy from a rectangular cross section of water. This allows it to take full advantage of shallow flows. Changing the amplitude of oscillation of the foils, means the system can be adjusted for different flow depths. This means that extra water available at high tide can be exploited.
The Carbon Trust recently concluded that the UK had a significant tidal stream resource which could supply 6% of total UK energy demand, excluding any tidal energy that could be extracted from shallow water. However, it has been estimated that if energy from shallow water is included it could meet 14% of total UK energy demand.