Author Topic: hydro voltage control (Read 4334 times)

chainsaw · « **on:** July 06, 2006, 06:41:37 PM »

I have just completed a dual rotor hydro unit and need some advice on the utilizing the most output from this unit. My maximum(no load) out of this unit is 90 volts DC, amperage is unknown. I am 300 ft. from the hydro to an existing(solar) 24v battery bank. Do I need to use a separate MX60 or some type of dc to dc transformer at the battery bank so as to take advantage of the 90V output and reduce the wire size needed or should I hook direct to the battery bank and let the batteries regulate the output which would really load up the alternator(slow it down till it reached the 24V output speed) and of course drop my voltage to 24 and increase the wire size needed. Am I correct in thinking that the maximum output from a PMA would be at its highest speed and I should try to regulate this voltage at the battery bank for max output? Any thoughts and advice will be greatly appreciated.

DanG · « **Reply #1 on:** July 06, 2006, 03:20:46 PM »

The MX-60 goes open circuit a minimum of 4 times per hour, 'tastes' the qualities of input power and recalibrates itself - not a good thing for hydro or wind to allow the open circuit overspeed...

Nando · « **Reply #2 on:** July 06, 2006, 03:41:39 PM »

What you are trying to do is a NO, NO, Never to do !!

The Turbine needs to produce its peak power for maximum harvesting if you load it with 24 volts ( it is a clamp voltage) the turbine may produce 1/4 or less of its capacity, it depends on the head, water and Generator.

Since you have 90 Volt OPEN Circuit you may connected to the MX60 without any problem even when the MX60 stops charging and goes sniffing the voltage

It seems that your loaded voltage may go around 35 to 40 Volts and you may try to add both, the turbine and the solar via good isolating diodes; you may find what is best by taking readings of both sources when connected to the MX60.

It may be that the turbine may drop to the solar voltage

What is the expected power of the turbine, is it AC and 3 or single phase ?.

Nando

chainsaw · « **Reply #3 on:** July 06, 2006, 05:08:20 PM »

Thanks DanG. I am unclear on using a MX60 with the hydro unit. Since my maximum unloaded voltage is 90V, will the MX60 use this max voltage for its MPPT function all the time so that when it sniffs, the hydro speed will not change very much since it is already running at its max speed.

chainsaw · « **Reply #4 on:** July 06, 2006, 05:27:07 PM »

Thanks for the reply Nando. My existing MX60 is close to its maximum capacity on cold sunny days so I would have to use another MX60 for the hydro if this is the best way to go. Or use a DC to DC converter if available? My hydro resource is 25ft head, 4 one half inch nozzels,70 -110 gpm, a homemade turgo type runner, three phase permanent magnet alternator.

QUAZ HOLT · « **Reply #5 on:** July 06, 2006, 07:37:33 PM »

Chainsaw, if your voltage is constant at 90v dc you could try some switching supplies from old equipment. I have found some of these that can efficiently convert from 90v to 24 volt. this is also dependent on the current at 90v. By using an adjustable output dc to dc converter you can regulate the current to the batteries. Bill

Countryboy · « **Reply #6 on:** July 06, 2006, 08:24:36 PM »

25 feet of head with 70-110 gpm is roughly 175 to 275 watts. (A rule of thumb is 1 watt for every 10 gallons per foot of head.) 175 or 275 watts at 90 volts should be 1.9 to 3.1 amps respectively. As soon as you hook this up to the 24 volt battery bank, you should have 24 volts and 7.3 or 11.5 amps roughly.

You stated you have a dual rotor. Doesn't this produce AC, instead of the DC you mentioned, or do you have 90 VDC after the bridge rectifiers?

It won't slow down the alternator until it is at 24 volts. The battery bank will hold the voltage down to 24 volts, but the amps will increase a proportional amount to the voltage change so that your total watts remains the same.

Once again, an alternator doesn't produce DC. It alternates the current, which is why they call it alternating current.

Nando · « **Reply #7 on:** July 06, 2006, 10:31:21 PM »

If your MX60 is at about maximum capacity then a new charger may be needed.

You have 90 Volts OCV = Open Circuit Voltage because the Generator is at twice of the RPM when loaded.

So around 40 to 45 volts when loaded .

At 70 GPM the power is around 200 watts for a current of 200 w / 28.4 volts = 7 amps to 11 amps when 110 GPM

There are some PWM supplies that are rated to 100 volts in and 28 volts out, .

Before you make a decision of buying another charger, why don't you connect the hydro to the MX60 ( disconnecting any other power source it may have) to see how the hydro-MX60 operate together.

The MX60. I believe, it has a manual mode that disables the search function and still produces MPPT control -- I hope I am right !!

Nando

Flux · « **Reply #8 on:** July 07, 2006, 02:00:32 AM »

Nando is right, you need to convert from about 40v to 24v. The MX60 would be ideal for this, but you are not using much of its capacity or facilities.

If you have no electronic experience it may be the best way to go.

If you or someone you know can do it, you could get the result quite cheaply with a simple buck converter. You don't need mppt, just set the pwm to drag your alternator down to about half no load speed.

If you connect direct you will likely get about 50 to 60% of the power with a dc/dc converter.

Flux

chainsaw · « **Reply #9 on:** July 07, 2006, 05:07:02 AM »

Thanks to all for the excellent information for the hydro. The 90v unloaded output is after going through the bridge rectifiers.

DanG · « **Reply #10 on:** July 07, 2006, 08:53:22 AM »

The Outback Forums have a lot of info waiting to be mined

Hydro Application

http://www.outbackpower.com/forum/viewtopic.php?t=709

http://www.outbackpower.com/forum/viewtopic.php?t=434

http://www.outbackpower.com/forum/viewtopic.php?t=505

Disabling re-calibration : importance of mini-sweeps (set to zero interval!)

http://www.outbackpower.com/forum/viewtopic.php?t=137

Also -

And out of curiosity, how and where are your phases rectified?

~

hydrosun · « **Reply #11 on:** July 07, 2006, 09:51:47 AM »

A hydro will put out it's maximum power at 46% of it's unloaded speed. So if you have a 90 volt unloaded output, then the maximum output would be at at 40 volts. I've used the MX-60 with hydro. the biggest problem is keeping the voltage from going too high and destroying the MX-60. I've hooked the MX-60 to the hydro and solar panels together and the solar panels clamps the voltage when the MX-60 goes open circuit once an hour. As far as overloading the Mx-60 on cold days when the solar panels are producing more, the MX-60 will just reject some power and allow the input voltage to rise out of the maximum voltage range to protect itself.

The problem with using the MX-60 with both solar and hydro in your case is getting the maximum power out of both. The hydro max. power point is about 40 volts but the output won't change much from 35 to 45 volts. Your solar panel panel max will vary with the temperature from about 30 to 36 volts. In practice the MX-60 will be somewhere in between the two peak power points, with the voltage closer to the peak voltage of the source that is putting out the most power. So during sunny days the voltage will be around 34 volts and cloudy days the voltage will be around 38 volts. You'll still be getting more power than without the MX-60 but you might get a few percent more power with two units. In my opinion it's not worth the cost of the second MX-60.

Chris

chainsaw · « **Reply #12 on:** July 07, 2006, 10:09:37 AM »

DanG, Thanks for good links. My 3 bridge rectifiers are located at the hydro unit at the present time and could easily be located at the batteries since I have not run the 300ft. of wire(still testing & trying to determine best procedure). I had assumed that it would be cheaper to run 2 dc wires rather than 3 of the wild ac but please realize that the only thing that I know for sure is how little I know(one of the only benefits of age that I have found so far)

chainsaw · « **Reply #13 on:** July 07, 2006, 12:00:24 PM »

Hydrosun, My existing solar is wired with 48v strings going to 24v bank, so my normal panel voltage varies from the 48 to 80+ with about 60v being the average for most of the day. How do you think the hydro and the solar would behave if wired to the same mx60? What happens or which source would the mx look at during the day when the solar is going up & down and the hydro voltage would be constant?

Nando · « **Reply #14 on:** July 08, 2006, 09:15:58 AM »

ONE needs to think how a parallel connection is made and how both power sources react to the load.

48 panels into 24 Volts bank means that the panel bank may have a Vmp of at least 68 volts and Voc of around 92+ volts.

The Hydro with 90 Voc may be at the same conditions that the panel and under load the panel or the hydro may set the input voltage as loaded by the MX60, this setting is defined by the internal impedance of both sources, having priority the one with lowest impedance and highest voltage.

So when the MX60 "looks", one with lowest impedance and highest voltage will dominate.

This way one source may feed higher power than the other.

For maximum efficiency the ideal case would be 2 charge controllers to maximize the power fed to the batteries.

By the way, if you have 24 volts bank fed by a 48 Volts panel, it would be best to separate the panels into 2 - 24 volts for emergency purposes in case the charge controller goes bad, paralleling the panels to produce 24 volts feeding directly to the battery bank without a controller ( 2 -24 volts panels in series or 2 - 24 Volts panels in parallel).

Nando

chainsaw · « **Reply #15 on:** July 08, 2006, 10:52:34 AM »

Thanks Nando for all the above information, it has been very helpful to a neophyte who is still on the bottom side of the learning curve.

Nando · « **Reply #16 on:** July 08, 2006, 12:39:24 PM »

By the way, it would best if you place the rectifiers by the load and not by the generator.

This way one can make easier modifications to the system

What type generator do you have that produces 90 VDC (after rectification) and what is the RPM of the generator and of the Turbine.

Nando

chainsaw · « **Reply #17 on:** July 08, 2006, 02:18:52 PM »

Nando, I have built a dual rotor PMA on the Hugh Piggot design and use 4, 1/2 inch nozzels, the turgo type runner consist of a modified cooling fan from a Briggs engine. I do not know the RPM only the maximum unloaded voltage(90v dc). I'm sure that I am losing some potential with the homemade runner but can be easily changed once I get the charge control figured out and see how feasible the unit will be.

Nando · « **Reply #18 on:** July 08, 2006, 02:28:45 PM »

Why don't you send to me the water parameters and if you have a photo or picture of the Nozzles,

Normally the Banki type or close to it, needs a peripheral nozzle coverage which means to have a long lip,covering at least 45 degrees of the turbine, it may be that you may be able to get more power by increasing the efficiency.

Like I said, connect the hydro to the MX60 alone power source and see the results.

Nando

Nando · « **Reply #19 on:** July 08, 2006, 02:51:57 PM »

Heck I wrote Banki when I read Turgo and my mind operated on Banki bases.

Sorry for the message, my mind was out of lock, or really ON lock because I have been assisting another fellow in Center America with a Banki for the last 2 hours.

Still, I would like to see the Turbine and the nozzles to see what you are doing.

Nando

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Author Topic: hydro voltage control (Read 4334 times)