As ESRU preps its turbine technology for sea trials, which begin next week, Grant acknowledges that a number of questions remain. The researchers have not determined whether they need to float a buoy above to further stabilize or secure the turbine (addressing Taylor's concern about the turbine moving up and down too much). It is also unclear how the turbine will behave when there is no strong tide, and how the turbine's motion may affect an electric power cable attached to it. (For example, will the cable become twisted if the turbine moves around too much?)
ESRU scientists do not believe their technology will harm marine life, but admit they do not know whether the tethered turbines will attract or scare off fish. "The turbines turn slowly, so we're not talking about chopping up fish," Grant says, noting the installation of the mooring may initially disrupt the seabed but likely will not have to be touched once it is set in place. Verdant has spent about $9 million thus far on its East River project; one third of the funds were spent on studies to gauge the potential impact of the turbines on vessel navigation, aquatic life and fish migration.
Grant acknowledges that tidal-derived power has a long way to go before it can be used as a mainstream source of energy. "There are big barriers to making money out of this," he says. "There's a lot of technical risk, so there's a lot of financial risk, too." He expects it will be a decade or more before ESRU's turbines are ready to be used in earnest in the sea—much more testing must be done, in addition to the environmental impact studies and garnering of support from utility companies.
Renewable energy has always suffered from the fact that the best places to capture sunlight, wind, waves and tides are also the most remote locations, which means an infrastructure is required to send the power where it is needed. "In the U.K., it's quite difficult to get the power utilities interested in this," Grant says. "To get to this energy, you would have to run power lines across the country, which creates environmental concerns."
This has not stopped Verdant and other companies from trying. Lunar Energy, a U.K. tidal power company, in March began working with Korean Midland Power Company to create a giant 300-turbine field in the Wando Hoenggan Waterway off the South Korean coast. The plant is expected to provide 300 megawatts of renewable energy to Korean Midland Power by December 2015.
Utilities interested in tapping into tidal power will have to spend money to create the energy-delivery infrastructure, or at least convince government to pay for it. One thing working in favor of new energy sources: the cost of oil is not getting any cheaper.