FRANCES CARR 24th February 2005 TIDAL ENERGY FRANCES CARR 24th February 2005

TIDAL TECHNOLOGY AVAILABLE ENERGY depends on location & time - but is highly predictable. ENERGY = (TIDAL RANGE)2 EBB GENERATION: Amplitude of tides increased towards estuary by shelving of sea bed and funnelling of water by estuary. Barrage construction: usually with caissons (concrete or steel blocks), towed to barrage site and sunk into prepared foundations. Each caisson element would house group of turbine generators/sluices, or be blank to make up remainder of barrage. sluicing on flood tide, fill basin, hold water until tide recedes, electricity generation as water passes through turbines to sea. Possible construction of diaphragm walls of reinforced concrete within temporary sand island. But no cost advantage, could increase construction time by 2yrs.

ADVANTAGES LIFETIME of barrages unlimited – turbine generators replaced every 40yrs NON-POLLUTING TECHNOLOGY Provide PROTECTION against coastal flooding RELIABLE energy production No production cost Lifetime ~ 120 yrs design life No emissions Protection – as storm surge barrier. Reliable energy – predictable in terms of amount/time compared to others sources

DISADVANTAGES CHANGES TO: Affects a wide ranging area Ecology Hydrodynamics of estuary Water quality Recreational activities within estuary Affects a wide ranging area Long construction times Only produces energy for 10 hrs per day Energy production when the tide is moving in or out. peak generation varies though day with the tidal maxima, this could be accommodated times are known in advance, storage can be incorporated, and barrages at different geographical locations have tidal maxima at different times during any 24-hour period

TIDAL ENERGY SCHEMES Tidal energy scheme Build time yrs Capacity MW Load factor % Cost £/kW (1992) Generation cost p/kWh 8% DR 15% DR Severn barrage 10 8640 23 1250 7.2 16.2 Mersey barrage 5 700 1280 7.1 14.3 Wyre barrage 2 63.6 24 1470 6.8 12.4 Conway barrage 33.4 21 1610 8.7 15.7 Costs senstiive to discount rates and method of financing – double DR severn – double cost of energy at 1992 prices. SEVERN BARRAGE: could provide up to 7% of total UK energy demand – mersey 0.5% Larger schemes would connect directly into the national transmission system. Smaller schemes could be connected into local distribution systems. Severn – 16km barrage - £10.8 bn 1992 prices + £4.2 m development study. Severn - 0.5p/kWh after the debt had been paid off. Mersey - £900 m 1992 prices + £7.2 m study

LIMITATIONS 3000GW tidal energy available <3% suitable areas The World Offshore Renewable Energy Report 2002-2007: 3000GW tidal energy available <3% suitable areas for power generation Site specific High capital cost in relation to output – reflected in generation costs. Uk – favourable conditions for generating electricity - half of total tidal energy resources within EU Due to high tidal range across west coast – multiple estuaries/inlets Lead time- Severn, lead-time of at least 14 years before full generation (five years for environmental monitoring plus nine years for construction) Financers institutions may find the long leadtimes to completion, combined with the underlying risk of political uncertainty, unattractive from an investment point of view.

ASSUMPTIONS Assume tidemill devices not advanced enough technology and no EU funding to contribute – base projections entirely on barrage schemes Tidemills - turbine mounted on a steel pile driven into the sea bed

PROJECTIONS CURRENTLY: NO INSTALLED CAPACITY 2020: possible range 30 MW to total 9.5 GW if 4 schemes implemented, but too expensive – therefore unlikely 2030: Energy Technology Support Unit - total potential at 50 TWh - 3 PJ per year, if all potential sites are developed – including Solway Firth, Dee, Thames, Wash and Humber barrages – again unikely