|
|
| Fig. 1: In 2018, OpenHydro installed the first grid-connected tidal energy project. The installation took place at the EMEC test site in the Orkney Islands. (Source: Wikimedia Commons). |
The term tidal energy refers to drawing energy from Earth's tides and converting it into usable forms of power, predominantly electricity. [1] There are two forms of tidal energy, namely tidal stream energy and tidal range energy. Tidal range applications focus on exploiting the difference in the highs and lows of daily tides. On the other hand, tidal stream energy solutions generate power from the fast-flowing currents that result from these tides, usually through the use of large turbines. [1] This paper will focus exclusively on tidal stream energy.
Tidal stream energy is still a nascent industry, with only 3.5 MW of capacity installed worldwide as of 2016. [2] However, the industry is far more advanced than other marine energy solutions like wave energy, ocean thermal energy conversion, or tidal range energy. [1] Tidal stream energy has benefitted from strong parallels with the wind energy industry allowing them to draw on learning done in that field. [1] Illustrating the impact of this connection, the industry has largely converged around the horizontal-axis turbine solution, with 76% of all R&D funds committed to this one device. [2] Despite being a young industry, tidal stream energy offers a massive untapped renewable power source with minimal environmental footprint. [1] Additionally, in contrast to other renewable energy sources like wind and solar, tidal power is highly predictable, making it particularly valuable to grid balancing operators. [1]
Just off the northern coast of Scotland lies an archipelago of roughly 70 islands, known as the Orkney Islands. Because of its location, Orkney is exposed to both the Atlantic and the North Sea, resulting in some of the strongest tidal currents in the world. [1] Because of the presence of these currents, the site was chosen to house the European Marine Energy Centres (EMEC) tidal test site. [1] Tidal and wave energy companies pay EMEC to use their grid-connected test berths, giving them the opportunity to connect their prototype technologies to the national grid under professionally monitored and accredited conditions. [1] The site also assists in research and consultation on these projects. Funded initially with £36m in public money, EMEC has been self-sufficient since 2011, using their revenues from their client companies to pay their own operating costs. [1]
The EMEC site at Orkney has been a major catalyst for the tidal energy industry. In 2008, at the EMEC test site, OpenHydro became the first company to generate tidal energy into the UK grid. [1] The turbine launched by OpenHydro is pictured above in Fig. 1. In August of 2017, the MeyGen project generated a record-setting 700 MWh of energy using three 200-ton turbines powered by the tides at the Pentland Firth. These turbines produced enough energy to power 2,000 Scottish homes. [1] The site is currently testing the world's most powerful tidal turbine, the SR2000 produced by the Atlantis Resource Corporation. The SR2000 is a new type of floating turbine, capable of generating 2 MW of capacity. [1] The presence of the Orkney site serves as an invaluable incubator for tidal energy companies to develop their technologies and prove the progress of their industry to commercial investors and governments.
Despite showing promising growth over the last decade, the tidal stream energy industry faces significant challenges moving forward, both technologically and economically. In terms of technology, these companies have to build turbines that can withstand harsh undersea conditions, rapid tides, and intermittent storms. [1] To achieve this, they will need to make advances in blade technology to reduce erosion and increase durability. Additionally, the industry as a whole will need to improve blade design and testing practices. [2]
Economically, the industry faces a potential reduction in government financial support. Presently, the UK offers guaranteed energy pricing of £300 per megawatt hour for marine energy projects, which is about seven times the current wholesale price for power. [3] This guarantee has been a strong incentive for developers and has provided a hedge against the risk of launching new prototypical technologies. This incentive has been a significant motivator for the private sector investment in the industry to date, estimated to be well in excess of £500m. [1] However, this guaranteed market price for marine energy was recently ended, leaving the future of private investment in the industry in doubt. [1]
While still in its infancy, the tidal stream energy industry has made tremendous progress, in large part due to the EMEC test site at Orkney. In order to progress from infancy into commercial viability, the industry will need to continue demonstrating progress to maintain government and private sector financial support. Thankfully, tidal stream technologies will continue to benefit from learning taken from similar turbine technologies in the wind energy industry.
© Thomas Rogers. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] A. Coates, "Blue Energy: The Marine Renewables Sector Starts to Show Promise," The Independent, 11 Oct 17.
[2] "World Energy Resources: Marine Energy 2016," World Energy Council, 2016.
[3] S. Reed, "Going Under the Sea for Clean Energy," New York Times, 2 Apr 14.
[3] A. Blandino, "Tidal Power," Physics 240, Stanford University, Fall 2014.
