Post by malewithatail on Aug 26, 2023 13:52:48 GMT 10
On our other farm we ran a micro hydro turbine. Initially a modified 24 volt alternator, and later an induction alternator made from a 3 phase 2 kw induction motor, generating at 240 volts, 53 odd hz directly. (Running at positive slip, instead of negative slip as in a motor).
The motor is connected in the low voltage, delta connection and capacitors are used to provide field excitation.
They were connected in C : 2C configuration.
Originally the capacitors were connected at the terminals, but for some reason, I needed to relocate them to about 30 meters away. The effect of this was quite unexpected. With the capacitors installed at the terminals, if the turbine output was accidentally shorted, then the field would drop out, the runner would speed up to over 10,000 rpm from its usual 3,200 rpm and I needed to go down to the turbine, turn off the water, let it stop, then wait for a minute or two for the residual magnetism to reestablish itself, turn the water back on and away it went. Later on, I found I could just charge a capacitor up to several hundred volts with the megger, and connect it across the terminals in the power room, this would re-excite the motor and away it went. A quite spectacular process as it created a large splat.
For some reason, I had to relocate the capacitors about 30 meters from the turbine, and then after a accidental short, once the short was removed, I discovered the turbine re exited and away it went, automatically. This was due to the voltage drop across the 30 odd meters of cable that didn't quite totally kill the voltage on the capacitors.
Another puzzling aspect of the installation, was the need to add additional capacitance to the C side, to get maximum output. This was because I was using a homemade 24 volt, 100 amp charger that was just a 2 kw transformer, with a hand wound secondary and diodes (Big ones !), to charge the main 1,000 amp hour nickle iron battery pak directly from the 240 odd volts of the turbine. The inductance of the transformer robbed capacitance from the turbine and this needed to be added as extra capacitance. The switch mode type of efficient power supply hadn't been invented yet.
Obviously, once the battery's are charged, the hot water is hot, (as it could directly heat the hot water tank as well), and the thermostat is off, the turbine output to the battery's has to be reduced somehow. I used a homemade shunt regulator that could dissipate over 5 kw continuously and shunt the power away from the battery's as the turbine needed a load on at all times or it would gradually run away and end up spinning at over 10,000 rpm. Or would have if the capacitors didn't absorb the charge as the frequency (speed), rose, getting hot and eventually letting go very spectacularly !
Apart from the increased maintenance on the system caused by the filthy water coming out of the colliery above us, blocking the 50 mm pipe with mud, dead bacteria, and the occasional plastic bag every few days, a micro hydro turbine will out perform a solar installation almost every time. This was easily fixed by opening the bypass valve every few days and letting the 'mud' get forced out of the pipe, restoring the flow and head.
Figures for pressure was around 800 Kpa (80 meters), and flow around 4 Liters/second, giving a max theoretical power of over 3 kw, but from that has to be removed runner efficiency, nozzle efficiency and alternator efficiency, giving about 1.8 kw into the battery's. The formula for power, without losses, is P = 9.81 (acceleration due to gravity) X head (in meters) X flow (in liters/second). I ended up making some stainless steel nozzles as the water was very abrasive and wore out the commercial brass ones very quickly. I did try a spear jet type of nozzle, but the extra output wasn't worth the effort with the increased maintenance due to the dirty water.
1.8 kw at 24 volts is 75 amps, 24 hours a day. That's over 1,800 amp hours, or 43 Kwh per DAY ! That's equivalent to 20 off 400 watt solar panels, and you get that at night, and in bad weather as well.
Platypus Power in Victoria sell a range of turbines, from low voltage DC types, up to multi KW systems for small towns.
The above information is only for interest, induction alternators running at mains voltages are DANGEROUS and will KILL, especially as there is no earth leakage protection of it. DO NOT PLAY WITH THEM !!
Our model of reality is founded on some basic assumptions based upon limitations of our biological sensory apparatus. The mechanical sensory apparatus we build tend to be modeled on our biological sensory apparatus and the Basic Assumptions Which May Be Wrong which we make based on those apparatus. In other words, reality might not be what we think it is.