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

2. 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.

3. 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

4. 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

5. 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

6. LIMITATIONS 3000GW tidal energy available <3% suitable areas
The World Offshore Renewable Energy Report :
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.

7. 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

8. 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