A FRESH ASSESSMENT OF TIDAL RANGE PROJECTS
The purpose of this briefing is to provide up-to-date information on the potential benefits of tidal range energy generation and the rationale for a fresh assessment of its inclusion as an integral element of the UK’s future energy mix.
The government is committed to net zero emissions by 2050. The National Grid System Operator has estimated that generation capacity will have to double by 2050. Around two thirds of existing power stations are expected to close by 2030.
The Government proposed that the main components of this future low-carbon power generation will consist of off-shore wind, solar, nuclear power and gas-power used in combination with carbon capture and storage. “There is considerable risk that these technologies may not provide the generation capacity required.” The CCC Renewable Energy Review 2011 stated that tidal range “Should be triggered as an option if relative costs improve…”
This note provides an overview of recent developments in tidal range technology, energy output, environmental impacts, and unit energy costs to show that tidal range should be reconsidered as part of the UK’s future energy mix.
Scale and security
The UK is an island that is blessed with having the 2nd highest tidal range resources in the world. These should be harnessed to ensure that electricity supply meets future demand and profits from the predictability, reliability and system benefits offered by tidal range to support intermittent and less reliable energy from wind and solar.
Tidal range projects in development offer an achievable 10 GW installed capacity, delivering over 20TWh/y (~ 5% of UK energy use). There is scope to expand this capacity significantly, with Liverpool Bay alone having the potential for a further 5GW capacity and other tidal range project sites around the UK already identified.
Some of the tidal range projects currently in development are detailed below:
|Power (GW)||Energy (TWh/y)||Cost (£Bn)|
|Mersey||1 – 5||2 – 7||3 – 9|
This would mean that 20TWh/y could be available by 2030 or soon after.
“Indigenous generation has security of supply advantages over those which depend on imported fuel supplies. Where we rely on either imported power or imported fuel stocks, there is inevitably a greater risk of interruption than for domestic alternatives. Tidal power uses UK sources of generation.”
Following the power interruption at 5PM on 9th August 2019, which impacted hundreds of thousands of people, Andrea Leadsom, the then Secretary of State, stated that: “Friday’s incident does however demonstrate the need to have a diverse energy mix.”
Intermittency of supply from wind and solar is a challenge that the Government is seeking to address as increasing proportions of the UK’s supply comes from these sources. Although supply from individual tidal range projects is also intermittent, it is predictable. The time of high tide varies around the coast, providing the ability for two or more schemes in different parts of the country to generate at different times delivering near continuous supply.
A tidal range scheme can store and release energy – moving generation by up to an hour can match demand peaks more closely.
A sustainable, significant contribution to Net Zero
The Government is committed to Net Zero and plans to prioritise decarbonisation of energy, transport and heat to help mitigate the challenges of Climate Change for future generations.
Tidal range can offer a significant contribution towards regional, as well as national, Net Zero targets. In Liverpool City Region, for example, a Net Zero target of 2040 has been set which can only be achieved if the Mersey Tidal Power project were to be built, powering local transport, heavy industry, data centres and the hydrogen economy.
Tidal range projects are long term. They are designed with an operating life of at least 120 years and offer significant multi-generational benefits. Other forms of low-carbon energy typically need rebuilding every 25 to 40 years, as well as being expensive and challenging to decommission.
Employment and regeneration
From the Bristol Channel to the North West, tidal range projects under development are located in places where jobs are scarce.
Each tidal range project will provide direct employment in research, development, construction and operation. The availability of affordable energy will encourage the development of sectors such as hydrogen electrolysis and data storage, while sectors such as tourism, recreation, biodiversity and aquaculture will thrive.
The supply chain needed for each project will be extensive, providing long-term employment and business support in sectors such as steel production, turbine manufacturing, civil construction and engineering throughout the UK.
The design life of a tidal range scheme is typically about 120 years, with actual life possibly double that figure. Critically, the design proposed for many schemes allows for sea wall height increase (needed to combat rising sea levels) and technology/turbine overhauls and updates (every 25/30 years) to be carried out cost-effectively.
Any analysis of the value for money of a tidal range scheme needs to take into account its long operating life and benefits accrued long after its capital costs have been repaid.
Multi-functional – beyond energy alone
Unlike other renewables, tidal range projects offer significant non-energy benefits and a wide system analysis is required to determine the full value of their creation.
Many tidal range schemes are planned in areas such as North & South Wales, Somerset and the North West where the coast is liable to the impact of storms, waves and tidal surges – a threat that is increasing due the effects of climate change.
Only small, wind driven waves will build up behind the impoundment, greatly reducing potential coastal erosion. Tidal surges can be controlled by the wall and sluices ensuring, on the rare occasions when external storm surges do occur, that the basin water level is controlled, allowing river waters to void into the lagoon basin and reducing storm impact on the coast.
Tidal projects will have benign impact on property insurance for houses and businesses affected by flooding and liberating extensive acreage for development (eg. 500 Ha freed up by the North Wales Tidal Lagoon).
Barrages can also provide a structure for new transport links, such as that proposed in Hull and the Morecambe Bay and Duddon tidal energy schemes.
Suitable for Regulated Asset Base finance
For energy sources that have a very high capital cost and long construction period, such as tidal range schemes, “The cost of capital is so dominant that it can explain as much as almost half the costs of a project.”
The Department for Business, Energy, and Industrial Strategy (BEIS) has issued a consultation paper on using the Regulated Asset Base (RAB) method for funding nuclear development and has raised the possibility of applying the RAB method to other energy generation systems; “We are also considering whether a RAB model could be applied to other firm low carbon technologies such as transport and storage infrastructure for carbon dioxide.”
A comparison of the key features of the Nuclear, Thames Tideway, and large tidal range schemes demonstrates the suitability of tidal range for RAB funding:
|Cost (£Bn)||Construction Period (years)||Design Life (years)|
Current schemes are focused on mitigating any loss of intertidal habitat that had been seen with previous schemes such as the Severn. The adoption of triple regulated turbines, which can pump and generate efficiently in both directions means that natural tidal amplitudes can be replicated. In addition, these larger, slower turbines also have fewer blades with rounder profiles for low impact on fish passage through them.
Tidal range projects that protect coastal communities also shield the natural world from the damages caused by storm surges and rising sea levels. Protected waters, nesting sites and
sand dunes will be defended, while migration routes for birds and fish will be carefully safeguarded.
Improvements since last assessment
There have been significant advances in tidal range power generation technology since the last full assessment in 2011, providing an uplift of approximately 30% extra output, substantially enhancing the industry’s financial model and value for money:
- Net benefit of pumping, depending on allowable tidal range – 10% increased output
- Artificial Intelligence (AI) optimisation of turbine start and finish heads for each tide – 7% increased output.
- Triple regulated turbines with non-synchronous generators – 10% increased output.
- Traditional tidal range operation, such as for the Severn Barrage in the DECC 2010 feasibility study, was based on ebb only generation, ie two pulses of power each day. This resulted in about 7 hours power gap. Operation now proposed is ebb/flood generation which provides four power pulses each day with power gaps of about 2 hours for spring tides and about 4 hours for neap tides. This also reduces peak power and tidal range generation which is more even and more acceptable to the grid.
Construction methodologies and techniques have also changed. The widespread adoption of floating caissons for deeper water in tandem with traditional embankments offers faster (reducing finance costs) and cheaper lagoon and barrage wall build costs (estimated at 10%).
In addition, the imposition of a Treasury optimism bias of 30% in previous assessments (a standard addition on public sector procurement cost estimates) needs removing. Tidal range schemes are projected to be driven by the private sector scheme with assessed contingencies so little or no optimism bias should be applied.
Compared to the DECC 2010 Severn report, energy output improvements are estimated to be 25% higher with potential cost reductions of over 20%.
These improvements make previous assessments in 2010 and 2011, upon which much government policy is based, no longer accurate.
 National Infrastructure Commission. Smart Power 2016 page 5
 House of Commons Science and Technology Committee. Clean Growth: Technologies for meeting the UK’s emissions reduction targets. HC1454 August 2019 para 48.
 Ibid para 54.
 Committee on Climate Change. The Renewable Energy Review, May 2011 Table 1 page 23
 Northern Tidal Power Gateway. Strategic Outline Business Case September 2019. page 58
 Infrastructure Intelligence 15/8/2019
 Dieter Helm The Nuclear RAB model. June 2018 page 3
 Department for Business, Energy, and Industrial strategy, RAB Model for nuclear, July 2019
 BEIS RAB model for nuclear . Consultation. July 2019 para 20.