Comment from a reader:
Minesto, a Swedish firm, has developed a new method--a sea kite--for harnessing the energy of tidal currents. Go to:
http://www.robaid.com/tech/minestos-underwater-kite-could-harness-tidal-energy.htm;http://minesto.com/
There are currently two tidal energy systems being employed around the world. One is tidal barrages, which use technology similar to that found in hydropower stations, and the other is tidal stream systems, which use the motion of the tide and work like wind turbines.
The sea kite--called "Deep Green"--consists of a 3-foot-long turbine attached to a rudder and 39-foot wingspan tethered to the ocean floor with a 330 foot cable. Compared to other tidal energy designs, this sea kite is small, which means its turbine rotates fast and functions better in greater depths. Anchoring and steering the sea kite allows it to capture much more energy. The kite travels 10 times faster then the water it operates in, resulting in 1000 times more energy.
While the tide forces the kite to move, an automatic rudder system controls the device's trajectory. The control system also monitors for depth, turbulence, and large objects nearby. To avoid interference with ship traffic, and for environmental concerns, Minesto says the kites would also "fly" at least 65 feet below the surface.
Once operational, each Deep Green kite is expected to generate 500 KW of power while it glides with the tide.
Deep Green requires a minimum depth of water of 60 meters. It just so happens that 63 meters is the depth of the water directly off
Macmany Point at the mouth of Subic Bay. If an array 12 sea kites were installed on the ocean floor at that location, their output would equal that of the 600 KW coal fired power plant, but without the air pollution.
How to accomplish this? The National Government should enact a law granting the operators of the new coal fired plant a credit against their tax liabilities in the amount of all expenditures made by the operators for the installation, maintenance, and repair of an array of these sea kites at the mouth of Subic Bay. To replace the revenues lost, the National Government should impose a tax on the new power plant which would be due if minimum emissions levels are exceeded, commencing when the new coal fired plant goes on line. This will provide an incentive to the operators of the coal plant to install the sea kites. Once the sea kites start generating power, the tax on emissions will encourage the operator of the plant strive to generate power using the sea kites, instead of coal, reducing emissions. However, it can be expected that the sea kites will experience some teething problems. Moreover, power from the sea kites will fall, but predictably so, during periods of 'slack water'. The coal fired plant can serve as a backup, assuring reliability of the power supply to customers.
The National Renewable Energy Board already has a petition pending before the Energy Regulatory Commission seeking approval of a tariff of 17.65 Php/kWh for electricity from ocean sources. Go to: http://www.evc.gov.ph?pdf/NREBPetition-FIT).pdf
For a description of how circulating fluidized bed coal fired plants can be "cycled" to take into account fluctuations in power provided by renewable sources, go to: http://www.johnkengineering.com/techinfo.htm#_Cycling_Operation_of
