15 Aug 2017
Tidal developers need to maintain consistent production even in ‘grid-constrained locations’
Market research company New Energy Update has published a whitepaper investigating the nascent field of energy storage technologies for tidal energy projects.
So, what energy storage technologies are currently under development? And what are the challenges facing this emerging sector?
BARRIERS TO INTEGRATION
The Energy Storage Solutions to Support Tidal Projects report provides a detailed outline of an expert panel session held in November last year at the International Tidal Energy Summit 2016. Before the session, conference delegates heard that energy storage is gradually emerging as a viable technology to help tidal developers maintain consistent production even in ‘grid-constrained locations’ – but that a number of barriers to effective storage integration in tidal markets such as the UK remain, largely related to issues associated with ‘regulation and a lack of clear business models.’
To illustrate this point, the reports’ authors point out that last years’ UK National Grid enhanced frequency response (EFR) tender – which saw the award of funding for 201MW worth of battery storage projects – ‘represented the first time battery storage won contracts in ancillary services tenders.’ However, despite the fact that EFR has resulted in ‘lots of new entrants entering the storage market,’ Jonathan Cohen, Head of Energy Storage at international law firm Eversheds Sutherland, observed that most of the EFR storage projects will not be financed through traditional project finance and that ‘a number of challenges’ still remain.
One of these challenges relates to how storage interfaces with current renewables projects. For example, under recent government proposals for the UK Contract for Difference (CfD) programme, Cohen pointed out that the import or export of energy from storage ‘might not be eligible for CfDs, which would only apply to generating unit output.’
Cohen also urged developers to be aware that the proposals stated that ‘storage should be implemented in a separate balancing mechanism unit to any underlying generation facility’ – primarily so that they can avoid ‘jeopardizing’ their renewable incentives by putting storage on site. In his view, the business model required for energy storage is also ‘more complex than renewable energy,’ mainly because it has ‘multiple revenue sources’ that are difficult to model. Moreover, he observed that, at least at present, energy storage contracts being offered with the UK National Grid are very short term, a situation he believed ‘could discourage investors.’
Despite this relatively downbeat assessment, the whitepaper reports that a few tidal energy developers have begun experimenting with storage technologies – and singles out a European Marine Energy Centre (EMEC) hosted scheme that seeks to use excess tidal power to generate hydrogen, which can then be stored and used as a fuel for marine transportation, as a ‘significant project.’
According to Neil Kermode, Managing Director at EMEC, the Centre was ‘forced’ to investigate storage options when rising demand for EMEC services put a ‘strain on the local grid,’ which he revealed was never designed for the renewables tested at the facility and was ‘starting to become stressed.’
Following a review of the suitability of various technologies for tidal energy production, Kermode explains that EMEC chose to focus on hydrogen storage – largely driven by the fact that the Centre’s activities ‘have a six-hour period, in the multi-megawatt department.’
Since them, EMEC has installed a 500 kW electrolyzer to collect excess energy from the tidal arrays on site, as well as a local wind turbine, and convert it to hydrogen. The hydrogen is then exported to Kirkwall, on mainland Orkney, where Kermode says it will be used to power a fuel cell to run ferries tied up over-night – and eventually for ferry propulsion and auxiliary power units.
At this stage EMEC is using what Kermode describes as an ‘industry-standard’ polymer electrolyte membrane electrolyzer to produce hydrogen from tidal turbine energy. However, as the project is ramped up he expects the Centre to install alkali electrolyzers with ‘lower-cost electrode materials.’
The report also highlights another interesting initiative by US-based company Water Wall Turbine, which is currently commercializing barge-based tidal turbine technology hooked up to a land-based microgrid with 500 kWh of energy storage, using Tesla lithium-ion batteries. According to Marek Sredzki, CEO of Water Wall Turbine (WWT), the storage system can also receive energy from solar and wind power – and he reveals that the company is seeking to integrate all three sources at a facility on Dent Island in Canada.
Sredzki also told delegates that WWT eventually plans to establish a ‘permanent, fully operational demonstration centre’ of the Microgrid technology on the coast of British Columbia utilising ‘concurrent tidal, solar and wind’ to deliver ‘firm power to both remote and on-grid applications.’
The whitepaper also reports that other experts have confirmed tidal projects ‘could benefit from storage as a way of evening out production to deal with limited grid capacity.’ One such expert, John Fitzgerald, Chief Engineer for Sustainable Energy Systems at Black & Veatch alerted conference attendees to the potential for storage to mitigate local constraints, but warned of the difficultly of monetizing such benefits ‘in the current market.’
Fitzgerald also pointed to an analysis of tidal production in Orkney that has shown that ‘even with storage there may have to be curtailment around spring tides.’ Even so, Cohen stressed that the technology remains a ‘bankable market’ that is likely to witness ‘lots of movement’ once the regulatory framework has improved.
Summing up the findings of the report, Paul Soskin, Director at New Energy Update, points out that it is currently a ‘very exciting time for the tidal energy sector,’ with pioneering projects by MeyGen, Scotrenewables and OpenHydro ‘demonstrating tidal’s potential to produce reliable electricity.’
“Also, when compared to solar and wind, tidal power is completely predictable. This could allow it to have a stronger synergy when partnered with energy storage in order to support the energy demands for both the national grid as well as remote micro grids,” he adds.
By Andrew Williams