Interprojects offshore wave energy converters (OWECs)
Abstract
The IPS-OWEC system was thoroughly studied and tested in the OWEC-1 project which was reported at the second european wave energy conference 1995. In the printed OWEC-1 report published in March 1996 the following unanimous recommendation was made: The slack moored IPS point absorber has been selected as the best suited device to act as both demonstration and test-bed for further R&D. Interproject is now having very interesting marketing discussions involving certain locations on the European Atlantic coast as well as the American west coast.
System specifications
The IPS - OWEC system is very flexible and can be adapted
to various locations and various wave climates and also to seasonal variations
in wave climate and power.
An IPS power station can be developed in steps and more units can be added
without interfering with the already working and producing units. A MI size
IPS power station could have more than 500 units linked together located to
fit into the coastal configuration and to the depth situation. A water depth
of about 40-50 metres is recommended.
Every individual unit can be built as a complete power station
but normally 10 units would be linked together to feed one central generating
unit, Such an arrangement is favourable from an investment cost point of view
and will also smoothen out variations in output from the individual units.
An IPS-OWEC unit consists of a buoy body or buoy hull plus
an acceleration tube and a pumping and conversion machinery including the
electric generator. The mooring arrangement is also important.
The buoy body is circular or oval. Diameter and weight depend
on the wave situation at the location. Normal buoy height is 6-8 metres. About
half of the buoy hull is under water.
The acceleration tube is vertical open in both ends and fastened to the buoy hull. The length of the tube can be up to 3 times of the diameter of the buoy hull. The working piston inside the acceleration tube has a restricted stroke length to prevent overloading of the system. The piston is connected to a hydraulic oil pumping cylinder or a hose pump system for pumping of hydraulic oil or water. The fluid will drive a hydraulic motor or a water turbine in their turn driving the generator.
The buoy hull as well as the acceleration tube should be
manufactured locally. Preferably close to a harbour with some service capacity
for transport deploying, mooring, etc.
The pumping and generation system, necessary instruments,
regulators, and other electronic units will be delivered by IPS or by well
known manufacturers/suppliers recommended by IPS. A great deal of those parts
is standardised and available worldwide.
The generated electrical power will be transferred with ordinary
sea cables to a land station on shore. To avoid too high investment cost for
the cable system a location not more than 500 meters off the coastline is
reconunended.
The land station has to be equipped with units for DC-AC
conversion, frequency adjustment metering, etc and connection to an existing
grid. The land station has to be designed and specified in accordance with
the local regulations and also depending on the size and strength of the existing
grid etc.
Under normal conditions an IPS OWEC station will produce
electric power on a yield level around 30 % calculated from the power of the
incoming waves to generator output.
At locations where the power content in the incoming waves
is high - for instance on the West Coast of Ireland - a medium size IPS OWEC
power station will be able to produce electric power at a cost of 0.25 - 0.30
SEK/kWh.
A time schedule for an in-vestment project 'including IO
IPS OWEC units will require about one year -including selection of site, arrangement
of service facilities, engineering, and manufacturing, assembly testing, mooring,
deployment and follow up.
Under favourable conditions the power station will be in full production after one year. See members.tripod.com/interproject for further information.