For the first time the generator was up, with a battery (home made 6V lead acid) and a load (12V CFL light). It works! Testing at first without the battery I blew the CFL light. Opening it up revealed a very blown 100microF 25V capacitor, which I could fortunately easily replace with a 63V 100microF I had lying around.
The home made battery is an ideal voltage regulator and speed control - when the voltage is below about 5.5V, there is no resistance, so the turbine speeds up easily. Above that voltage, current begin to flow into the battery, and the resulting braking effect slows down the turbine. It is a very gusty day (17 Oct 2006), and as the wind drops the current flows out of the battery to the light, and as it rises the current reverses, flowing from the generator and charging the battery as well as running the light.
The 6V battery seems to limit the speed too much, and it delivers a max of 2A, making about 10-15W. If I remove the load, the turbine begins to spin frightenly fast, and delivers 40V and more (open circuit). Reconnecting the load results in an impressive spark, and several amps flow until the turbine slows down again. I think a 12V battery will allow the turbine to settle at a higher rotational speed, and so deliver more power. Also, it seems the stator and rotors combination could work with much bigger blades.
I am worried about one of the loads failing, which would allow the turbine to spin very fast, possibly somehow just tearing itself to pieces. So when I go out, or sleep, I use a vice-clamp to keep the two ends of the cable from the generator firmly in contact. This keeps the rotational speed to a mimimum. The photo shows the two 50W bulbs in series I keep handy to dissapate energy if required.
I have read and been told that three blades work better than four, due to blade wake turbulence. However, I made the blades in pairs, and the second pair is lighter, so using three would make the hub out of balance. With two blades on the hub it doesn't seem to get turning very easiy in light winds.
Next step is to make a switch box, to make the connections neater and more reliable...
And viola! Here it is.
Latest configuration (21 Oct 2006) is a car battery plus the home made 6V battery in series, which of course runs at about 18V. This allows the turbine to spin faster and deliver more power as expected. I have just seen it deliver a burst of 4A at about 22V, making about 88W. I don't have a wind speed meter, but its about a medium windy gusty day for Cape Town. With a good steady South Easter I expect more power, and perhaps running at 24V would also improve things.
8 November 2006
I have purchased two small 7.2 Amp hour 12V batteries (for R100 each) from a very helpful Emil, and so now have a 24V test system. Two 12V CFL lights in series are used as a test load. These bulbs draw about 0.5A each, or a bit less once warmed up, so these batteries should give about 15 hours of light from a full charge. 24V allows the turbine to spin faster, and in a reasonable wind the charging current varies up to 3 or 4A. In a gust of wind I have seen over 10A flowing into the batteries, making 240W of power! With the batteries disconnected the power is very variable, and the bulbs flicker and sometimes go off. The batteries even out the power and also regulate the turbine speed.
I have also made a simple adjustable over voltage detector circuit, which sounds a buzzer and lights an LED if the voltage climbs above 27V. Circuit on request.
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