2. Direct Drive Linear Generator Point Absorber Wave Machine
So, for example:
if the desired power from the wave machine was 25kw then if the voltage in our example generator at 24 RPM was 100 volts, then the number of amps would be 250
(25,000 watts / 100 V = 250 amps)
which would require a tripple aught wire (000 or 3/0) gauge which would be impractable to work with in the generator.
Here are some other wire sizes related to 25 kw at different RPM for the example generator:
RPM Volts AMPs W. Gauge
24 100 250 000
48 200 125 0
96 400 62.5 4
192 800 31.3 7
384 1600 15.6 16
Off the shelf "Stamford" generators typically require 1,200 to 1,800 RPM to operate efficiently.
In wind machines, the RPM of a wind rotor is in the range of 40 to 400 RPM. In order to make then spin the generator at 1,200 to 1,800 RPM wind turbines usually have a gear-box transmission to increase the rotation of the generator to the speeds necessary for efficient electricity production.
So how does one put a gear box on a linear generator for a wave machine? This is difficult to impossible. One may think you could trun the plunger into a rack shaft and let it rotate a pinion back and forth and use a reversing rotational generator.
But practice has shown that while a rack and pinion works well when the pinion moves the rack, it does work very well in reverse.
Of course increasing the RPM is only one way to increase voltage in a generator. By Faraday's Law the voltage is proportional to the number of windings and the rate of the change in the magnetic field. So you can add windings, move the magnet faster or use a stronger magnet at the same rate to increase the voltage.
For more information go to: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html
http://www.electronics-tutorials.ws/electromagnetism/electromagnetic-induction.html for an explanation of Faraday's Law.
Finally, for the slow stroke cycle (7-30 RPM) of the wave powered direct drive linear generator there are two options:
1. design a custom linear generator that optimizes
the windings and the magnet force; and,
2. devise a way to increase the speed of the stroke
We utilized both of these options and designed a Hybrid Linear Generator see Second Design.