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TIDAL RANGE POWER A future reliable renewable energy resource Introduction

The British Hydropower Association [BHA] is the only trade membership organisation dedicated to representing the best interests of the UK hydropower community. Hydropower, or water power, is one of the most reliable, predictable and least environmentally 2 intrusive of all the renewable energy technologies and the BHA strives to ensure that the full potential and associated economic and community benefits are fully realised.

The BHA continues to promote and support the development of tidal range power projects as it provides predictable and secure generation capacity. Current research into a number of tidal range technologies and offshore hydropower is proceeding at a number of sites around the UK. Need for renewable energy > 3 The target for the country is to have net-zero carbon emissions by 2050. This is a real challenge as no currently renewable resources are available all the time - the not shining at night and the wind not always blowing. However the UK, with the second highest in the world, has good tidal range resources which have not yet been developed. 4 The time of high water varies around the coast, so it should be possible to stagger generation and provide reliable, predictable, and almost continuous power. >

The proposed Swansea Bay tidal lagoon wall. The length of 854 London buses parked in a row.

Explanation Tidal range power utilises the difference The tidal range system is different to tidal in head between the and a basin. stream which generates energy solely by 5 The basin is usually formed by a barrage the flow of tidal water through a turbine/ of tidal range across an estuary or bay or by a lagoon generator in a high tidal velocity location, power > wall. As the ebbs and rises it creates like a windmill under the water. a difference in the water level between the sea and the basin. Water then Tidal stream generally requires multiple flows through turbines which in turn 1MW to 2MW turbines operating in high drive generators to provide renewable water velocity areas, often around remote electricity. headlands. Such devices may also be suspended from surface vessels or Most schemes generate on both the sea-bed mounted. flood and ebb tides and some use the generators as pumps to replicate the natural water levels and increase the amount of energy generated. “A diversity of energy sources is Proven a good way, and the best way, technology of delivering secure supply.”

Predictable, reliable, and near 6 continuous output

The French medium sized 240MW Since the energy source depends on the In contrast to other renewable energy La Rance tidal range scheme has been tides, and these are predictable decades sources, there is only a short gap of about operating in Brittany for over 50 years ahead, output is predictable, both for 2 to 3 hours between each phase of with only minimal maintenance, thus timing and amount. generation. However the time of high tide demonstrating that the technology varies around the UK coast and much of Tidal range technology is robust with is proven to work and to last. 1MW for the time two schemes, one in the Bristol very little maintenance required and example is sufficient to power Channel and one off the North is therefore very reliable. Power output 750-1000 homes. coast, or in that region, could provide would vary somewhere between spring near continuous power. Like hydropower, following capital and neap tides but pumping can easily investment write off, this scheme reduce the difference. With the ability to move the time of continues to produce some of the lowest generation by up to an hour, tidal range cost energy anywhere in Europe. provides consistent flexibility in meeting those changes in demand. <

The 240MW La Rance opened in 1966 as the world’s first station.

Diversity Size of output Grid support Tidal range power will add diversity to the Many of the more economical tidal range With the large turbines and non- 7 energy mix, giving the UK another form schemes would be large, over 1,000MW. synchronous supply, tidal range will aid of renewable energy generation and so Estimates of power and annual energy grid stability and frequency control. ensuring that the UK is less prone to ‘no output vary from a theoretical maximum wind’ periods, or fuel price increases. of 37,000 MW generating 55 TWh/year. Employment

The construction of tidal range schemes Indigenous resource Using lagoons only would mean 18,000 MW providing 30 TWh/year. If included, would require the employment of several The UK has the second highest tides in the would mean there thousand workers for several years. These the world. Tidal power is an indigenous could be 5 schemes with a total capacity sites are coastal with many in areas of resource so it would not be affected by of 21,000 MW producing about 40 significant deprivation. political changes in other countries or TWh/y. This would be about 10% of UK other international events. annual energy requirements in 2040. The tidal basin walls would mean Tourists would be attracted to see tidal waves would not enter the basin and, range schemes. The La Rance scheme in away from the turbine and sluice outlets, France attracts around 70,000 tourists the water velocity would be low. Because each year. The potential UK tidal range of this, water conditions in the basin sites are generally in areas which would would be benign and ideal for sailing generate significant tourism activity. and other types of water sport activity. This would be particularly welcome in the where the high tidal range means most harbours dry out at low tide. 8 Recreation & tourism The basin walls means that the existing The impact of climate change induced Sea defence and sea defences would no longer be rise could be mitigated by vulnerable to ocean waves or tidal surges. controlling the water level in the basin. road link > This would greatly reduce the potential Tidal range barrage schemes across for coastal erosion and provides flood estuaries can also provide useful road and protection from coastal storms. This could infrastructure links. reduce insurance premiums in some areas and release flood risk land for future development.

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Natural Energy Wyre plan to build a tidal barrage across the river Wyre in Lancashire between 9 Fleetwood and Knott End.

“Sea levels are projected to rise... meaning we can expect to see an increase in both the frequency and magnitude of extreme water levels around the UK coastline.” <

The latest tidal range schemes will be built in such a way as to provide net environmental benefit

Environmental impact Reduction in carbon emissions Life of energy sources

It is now proposed that all major schemes The Climate Change Commission has Tidal range schemes have a design life provide net environmental benefit. set a target of net zero by 2050. It has of about 120 years. Almost all other Previous ebb only schemes resulted in been assessed that tidal range would renewable energy resources, including 10 basin water levels seldom reducing much recover embedded carbon in four years. solar and off-shore wind have a life of below mid-tide level, affecting land Thereafter tidal range would do much to between 15 to 50 years, and nuclear drainage, and impacted on the marine achieve net zero carbon. 60 years, so these would need to environment. The latest schemes with decommissioned and rebuilt several times ebb/flood generation, with pumping, International opportunities during the entire lifetime of any tidal can result in no change in the range range scheme. There are a number of sites around of basin water levels, thus minimising the world where tidal range schemes environmental impact. Historical fixed would be appropriate, including France, speed double regulated turbines would Canada, India, Australia, Argentina, have resulted in potential fish impact. China, and Russia. With the use and Future turbines would be variable speed, further development of tidal range triple regulated and impact on fish would technologies more potential sites may be considerably reduced. Particular well be identified. beneficial elements would also need to be provided. “We recommend that government ensure that levelised cost of energy analysis reflects a fair appraisal of long-term cost and power generation, which takes into account the full lifecycle of projects.”

Tidal range schemes have high capital levelised cost estimates assume a 40 year Comparative cost cost with very low running costs. The “financial lifetime” for tidal range projects... current assessment of the cost of energy Based on the standard discount rate of 10% of energy > is that, in the short term, it would be used in DECC cost estimates, additional between the current cost of offshore wind income or costs accrued after the 40 year and Hinkley C which was granted a CfD “financial lifetime” would be discounted 11 for 35 years. Similarly tidal range would down to a minimal amount. Such analysis need a similar long-period CfD. may lead to a less favourable assessment of The normal method used by government projects with a long lifecycle compared to to make comparisons between those which have a lifecycle of 40 years alternative energy sources is to compare or less. the discounted costs and production of schemes. This adversely affects schemes Assessing the levelised cost of energy, the with high upfront costs and very long- total cost of a scheme throughout its lifetime term low cost operation. The House of divided by the total amount of energy Commons Energy and Climate Change produced during its life, results in tidal range Select Committee stated “DECC’s energy being probably the lowest available. Of the renewable energy resources at Overall the peak energy time of early evening on a cold winter’s day, solar would not considerations > be available for a dozen hours and offshore wind could well be subject to a Scandinavian high pressure condition which can last for several days, if not a week, resulting in minimal power output. In comparison two “out of sync” tidal range schemes can provide power with a high reliability.

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Tidal range does not need expensive and potentially dangerous facilities for the storage of unwanted waste. Currently there is no allocation of CfD Future full-size tidal range schemes will Governmental funds for tidal range. The main problem be significantly more cost effective, but for tidal range power at present is the are likely to take a similar time to develop restraint > perceived lack of government support. and require a similar high risk investment This is particularly so since Tidal Lagoon to obtain a DCO and CfD. Power spent about £20m over c4 years and obtained a conditional DCO What is needed is an appropriate (Development Consent Order) for the financing model such that financiers Swansea lagoon pathfinder scheme but would be prepared to provide the at risk was refused a government CfD. development funds.

13 Tidal Range, Wind and Solar >

8GW

6GW WSLPeakGW 2.5

NWTEPeakGW 2.5

4GW

Combined Tidal GW

2GW Wind

14 GW Solar

TUE WED THURS FRI SAT

2GW WSL GW 1GW

GW NWTL GW

TUE WED THURS FRI SAT

The wind and solar data are from National Grid and Elexon for the week beginning the 28th of May Compiled by [email protected]. The solar and wind 2018. The tidal range data are modelled by different academic groups and represent the West data is from the National Grid and Elexon. The NTWL tidal Somerset Lagoon scheme and the North Wales Tidal Energy scheme. They are both scaled to provide data is from [email protected] and the West Somerset a peak output of 2.5 GW. and have been plotted against wind and solar to provide a sense of scale Lagoon data is from [email protected] and the timing of two tidal range schemes. Without greater enthusiasm and government support, such high-risk investments are unlikely to be forthcoming and the UK will not enjoy the benefits of such a predictable, reliable, and competitive long-term energy source. Combined Tidal GW

Wind

Solar 15

The image to the left demonstrates The tidal energy output is based on Conclusion > a typical UK generation period from 0-D modelling but without pumping May 2018. It shows the output for solar, or generation time-shift, which could WSL GW offshore wind and a combination of two probably close the small ‘no generation’ out of sync tidal range schemes; one in gaps. In contrast solar – the orange line,

NWTL GW the Bristol Channel and one off the North has long gaps and wind - the green line, Wales coast with a time of high water of drops to almost zero. about 4 hours difference. Simon Hamlyn Chief Executive Officer

JUNE 2019 Mobile: 07788 278422 Email: [email protected] www.british-hydro.org

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