GAME CHANGING ECONOMICS FOR TIDAL POWER
Economic viability is key to the acceptance and world-wide deployment of renewable energy. Tidal range power has always been relatively close to commercial viability, but the cost of the civil structure spirals out of control when using conventional methods to build long enclosures, especially in deep water. This is important because the civil structure typically accounts for 2/3 of the total project cost. Halcyon Tidal Power has developed an approach to the construction of the tidal range structure which is transformative in all aspects.
HALCYON CONSTRUCTION REDUCES THE COST OF THE CIVIL WORKS BY 50%
Conventional construction methods for tidal range power plants were originally developed for hydroelectric dams. Typical of these construction methodologies were earthen, concrete or other embankments with massive sloping seawalls or caissons consisting of large concrete boxes placed side by side on a heavily dredged seabed. Due to their geometry, the cost of both embankment and caisson construction increases by a factor of four each time the depth doubles. This renders this type of construction uneconomical for any structure other than short barrages or small shore-connected lagoons in shallow water. Truly massive tidal power plants required to address large scale power needs and climate change are unequivocally unfeasible using conventional construction methods.
Halcyon’s ‘Pile Supported’ Construction methodology replaces the foregoing conventional massive structural elements with a narrow (3 to 4 meter wide) marine enclosure, as well as reduces the length and mass of the powerhouse. Large diameter pilings set in sockets drilled in the seabed provide support for the marine enclosure, resulting in a light and narrow but extremely strong structure. Although pile support methods are now well understood and universally used for offshore oil and gas drilling platforms, their use in the construction of tidal range power plants is both novel and transformative.
Our pile supported construction methodology was favorably reviewed by the UK’s Department of Energy and Climate Change (DECC) in the course of the Severn Tidal Power Consultation (STPC). At a depth of 12 meters, it was found to reduce construction costs by 50% over the embankment methods, the least cost conventional option, and significantly less than caisson methods. Our cost advantage increases exponentially at greater depth and length.
REDUCING CONSTRUCTION TIME AND CONSTRUCTION FINANCING
Since construction financing costs are decidedly more significant for lengthy mega-projects, reduction in construction time yields major reductions in project cost. Tidal Power Plants built using conventional methods typically require 5 to 7 years to complete. Because Halcyon Pile Supported Construction is also modular, construction time can be reduced by more than half, significantly reducing construction costs.
Our pile supports are first anchored to undersea bedrock at equal intervals, and the Enclosure Sections secured between a pair of these supports. Likewise, our Powerhouse Caissons are similarly secured between support columns. Both the Enclosure Sections and Powerhouse Caissons are initially hollow for ease of transport, can be cast on shore, floated to the site, flooded, secured between the Support Columns, and finally ballasted. The casting and piling can occur simultaneously, allowing rapid assembly of the structure: under 3 years for a project of any length.
SCALABILITY OF HALCYON TIDAL POWER PLANTS – BIGGER IS BETTER
The energy produced by a tidal power plant is proportional to the area of the basin it encloses. When the radius of a shore connected lagoon is doubled, the length of the enclosure is doubled but the area of the basin is quadrupled. Doubling the length of the enclosure therefore quadruples the energy output.
If the cost of the enclosure is proportional to its length, then its cost will double each time its length is doubled, however its output will increase fourfold. The unit cost of energy will therefore fall rapidly with size. This is precisely what occurs for a Halcyon Marine Enclosure; they become more economic as they grow larger.
Since water depth typically increases linearly from the shore, as the radius of a tidal lagoon is doubled, the depth doubles. With embankment construction, as depth doubles, the base and volume of material required quadruples. Therefore, as the length of an enclosure is doubled to increase energy production, the cost of an embankment increases eightfold, raising the cost of energy produced to unsupportable levels.
SCALABILITY IS UNIQUE TO HALCYON MARINE ENCLOSURES
For a Halcyon Marine Enclosure, the economics are decidedly different. With the doubling of both depth and length, only the height of the Halcyon Marine Enclosure doubles – the width and the base configuration remain the same. Therefore, rather than quadrupling the construction cost of a Halcyon Marine Enclosure as depth and length each double, there is only a threefold increase in construction costs. With construction costs of the Halycon Marine Enclosure increasing threefold and energy output fourfold, building very large Halcyon tidal range facilities reduces the cost to produce power.
While turbines and powerhouse equipment generally double in quantity (and, therefore, cost) with a doubling of length, in a Halcyon Marine Enclosure such equipment is not impacted by the accompanying doubling in depth. Therefore, the doubling in radius, length, and depth of a Halcyon Marine Enclosure doubles the cost of the turbine and powerhouse equipment but, again, quadruples power output.
AFTER 30 YEARS, HALCYON TIDAL POWER PLANTS PRODUCE ELECTRICITY AT COSTS LOWER THAN ALL FOSSIL FUELS, AND LAST 120 YEARS
Halcyon vs other Marine + Hydro Chart: river hydro – US EIA Annual Energy Outlook 2013; offshore-wind – ibid; wave – NS Marine Renewable Energy Strategy 2012; NS FIT (6) – NSUARB; NS Target Cost – NS Marine Renewable Energy Strategy 2012; ORPC – FERC (“Combined” refers to prices which were not broken up in the source.) Levelized Costs Y1-30: all – US EIA Annual Energy Outlook 2013 Levelized Costs Y31-120: all – US EIA Annual Energy Outlook 2013