Renewable Energy
Fossil fuels will not last forever and investment is still going into accessing tidal power, one of the most reliable and predictable of renewable energy sources.
While policies are retained that promote the installation of alternative power sources, either by raising feed-in tariffs or implementing schemes such as the Renewables Obligation scheme designed to reduce carbon emissions, then there is an incentive but no great market pull.
As the cost of mainstream energy rises, so tidal installations become more financially attractive, and while government policies are retained that promote the installation of alternative power sources, either by raising feed-in tariffs or implementing schemes such as the Renewables Obligation (RO) scheme designed to reduce carbon emissions, then there is an incentive, but still no great market pull. Progress is largely driven by the technological improvements of the device developers.
Tis is a medium- to long-term
investment for the utility companies, so it is falling to engineering companies to lead the way; projects such as the offshore technology initiative in Orkney, Scotland, certainly help. Altra has worked on several turbine brake-system designs, ultimately destined for early arrays that are being funded by utility companies, but they remain beta sites. Reliability and robustness are critical and, despite the advanced site modelling done before installation, many companies are finding that conditions out in the open sea are harsher than predicted.
of grid loss (and a subsequent drop in generator load). Although there is no dominant turbine technology at this early stage, a number of the furthest developed designs on test are similar in principle to wind turbines, employing a traditional nacelle and horizontal-axis rotor arrangement. Different configurations are being tested with twin or single rotors; some are fixed to the seabed, others attached to floating rigs. Methods of power transfer include pumped hydraulics and on-board generators with the generation equipment and gearing contained within the nacelle. Viability of an installation site is dependent on many factors, including the suitability of the water flow rates, sea depth, proximity to population centres, infrastructure support and transport to site and, crucially, installation costs. All of these factors add to a Levelised Cost of Energy model (‘LCOE’ – the price at which electricity is generated taking into account many of the contributory cost variables) against which viability of different devices may be compared. Te basic principles of most undersea turbine designs are relatively familiar, based as they are on proven technologies from within the wind turbine industry. Factor in the operating environment
Fig. 2. The typical products Altra supplies to this industry include torque-limiting clutches and safety brakes.
Te typical products Altra supplies to this industry, such as torque-limiting clutches and safety brakes, were designed with the primary requirements being to bring the turbine’s rotor to a controlled stop or hold it during installation or for maintenance
purposes.Additionally, they perform an emergency stop function preventing over-speed of the rotor should flow velocity exceed safe levels, or in the event
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and everything becomes an order of magnitude more complicated: installation requirements, accessibility, dynamic sealing, wet connection of power lines, the huge mechanical forces on the devices. Many of the leading developers have experienced blade failures of some kind in the development phase, so scale-up and full size testing are taking their time to progress into commercial size installations. For the associated brake systems, Altra can supply a range of dry and ‘wet’ solutions; Twiflex caliper disc brakes traditionally work in the dry environment of a sealed nacelle, but may be developed for use fully exposed to sea water. Wichita multi-plate clutch designs may be configured to act as torque-limiting devices, protecting the drivetrain from torque spikes induced by extreme weather while similar ‘wet’ brake designs use oil- in-shear technology to develop torque. Apart from being inherently fully sealed, the advantage afforded by these units is the avoidance of dry friction rubbing, so wear is negligible. Tis is
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