Water Power 200 Generator

[Apple_Jack]

You can download the schematic within this thread... scroll up to post #8

[seandepagnier]

To efficiently use a wind or hydro turbine there needs to be a controller to convert voltage. You cannot just run it to the battery through diodes or something and expect good results.

The battery voltage is relatively constant, but the turbine needs to run at a voltage related to the speed of the flow. So with twice the wind, the voltage output doubles, and the current is 4 times. The regulator must convert this double voltage to 8 times the current. If you force the turbine to run at the battery, the blades won't extract as much energy since they will be overloaded and you end up with less than 8 times the current.

If the generator is connected directly to the battery, it will be efficient at only one specific speed. Otherwise it is like sailing with the sail too tight or too loose.

I have designed my mppt controllers for solar, a syncronous rectifier for wind/hydro (to avoid rectifier diode losses) and I'm working on a new mppt for wind/hydro that can brake, buck and even boost the voltage to ensure the load (drag) on the turbine is optimal and I can easily charge both 12 and 48 v batteries. The algorithm compared to wind is completely different as it deals with much larger input voltage (and therefore duty cycle) variations. Some wind turbines use wind speed/direction sensors, and some farms even network the data to anticipate gusts felt by nearby turbines.


Since overloading the turbine slows it down, and the blades are no longer as efficient, it is possible with an intelligent controller to brake the turbine without a dump load, slowing it down and extracting less power. If the controller is near enough to the motor it can generally stop the blades from spinning completely if needed. The output power will gradually decrease with wind speeds increasing over say 30 knots (depending on design and settings) unlike some turbines (like air-x) which stop and restart in high winds and continuing to output some power.

[Jim Cate]

You cannot just run it to the battery through diodes or something and expect good results.

Shucks, Sean, I sure wish you had told me this back in the late 80s when I started using my drag generator with just a blocking diode between the PM dc generator and the battery bank. I thought that it was doing pretty well at keeping my batteries charged for thousands of miles and a decade and a half.

Could it have been better? Perhaps, but it was adequate and simple and never failed electrically, never fried a battery. I was happy...

Jim

[seandepagnier]

Originally Posted by Jim Cate

Shucks, Sean, I sure wish you had told me this back in the late 80s when I started using my drag generator with just a blocking diode between the PM dc generator and the battery bank. I thought that it was doing pretty well at keeping my batteries charged for thousands of miles and a decade and a half.

Could it have been better? Perhaps, but it was adequate and simple and never failed electrically, never fried a battery. I was happy...

Jim

Thanks for redefining what "good" is Sometimes simpler is more reliable.

Regardless, this can only be optimal at a single speed for a given turbine. So you probably just didn't reach the full potential except at a specific speed. This is also very significant for craft that vary over a wide range of speeds, I cruise from 3-15 knots and want to make power by 5 knots. For wind power also important, and the mppt needs a different algorithm than solar.