Excess energy in off grid system

[chrisski]

Not necessarily. I have been using voltage sensing brakes as oppose to dump loads and they work 100%. While the brake is on (28.7v in my case) the turbine only shows you which way the wind is blowing but doesn't actually spin.

Maybe its not a dummy load, but the windmill still needs to be physically limited.

How good are these brakes in holding up year after year? I only have book knowledge of windmills, so any input would be nice.

 

[pollenface]

Maybe its not a dummy load, but the windmill still needs to be physically limited.

How good are these brakes in holding up year after year? I only have book knowledge of windmills, so any input would be nice.

The brake is only as good as the automotive relays (in my case) which short the phases.

Shorting the phases creates eddy current which physically inhibits the "spinning" of the blades. This can still be overcome by severely strong winds but will not generate power while doing so.

I prefer the brake idea as it is simple (for me) and does not create a voltage drop across the system as say a 300w dump load would.

 

[Don B. Cilly]

Actually, all windmills I know will "brake". Even a 30+ years old one I have.
If you physically short the phases (put the wire ends together), it will instantly slow down to a very slow spin.
All wind controllers I know have a brake function too.
It's never ben a problem.

 

[SolarPrep]

I'd look into products like the Midnite Solar Kid or Brat that has a circuit for running an outside load of some sort, like lighting. Haven't read up on that for a long time, so may be forgetting something. My recollection is that you can use it as a diversiobn load. I could be wrong.

 

[nativerobin]

My hybrid inverters on my off grid setup have a setting were you have it only draw from the panels what it needs to run the house and charge the batteries. My 2000 watt wind turbine has a charge controller and a small dump resistor bank for excess energy, if they didn't they could over charge your batteries.

 

[120vjohn]

Yes you can heat water or heat living place in winter as I do, if you install a heat pump you can do it better.
Diverter may be built in different ways i built it as a dc/dc that clamp battery bus at a preset voltage or pv array 1-2 precent above MPP voltage and divert power to dump resistors, as radiant heaters and water tanks, i presented it in this forum, but schematic has an error presented in that thread, probably i will reedit it.
This diverter no need any relay and can operate stand alone only with the solar array, it can operate both ongrid even during grid blackouts and offgrid.

If you need to adapt other voltage to your resistors diverter need two stages, buck converter to control and foreward open loop to adapt voltages, may be only a foreward pwm controlled, but my experience shows that tho stages is more robust, and stable, you need use use a single full protected stage (buck stage), is more simple and effective to protect it in compare with a pushpull or bridge foreward converter.

If you use a heat pump inverter driven motor you need an application to control that inverter to maintain a preset input voltage, if your battery or pv array meets with input voltage range o that inverter you need no other device, if not, the simplest is an open loop foreward converter that acts as a transformer
(dc).

 

[12VoltInstalls]

The brake is only as good as the automotive relays (in my case) which short the phases.

Shorting the phases creates eddy current which physically inhibits the "spinning" of the blades. This can still be overcome by severely strong winds but will not generate power while doing so.

I prefer the brake idea as it is simple (for me) and does not create a voltage drop across the system as say a 300w dump load would.

A learning question: I have been told (and read, and seen youTube vids) that braking a windmill - or less commonly, water wheel- by shorting the phases creates heat and eventually or sooner damages the windmill but a “heavy” load at the voltage-controller end does not have negative effects. And that some small windmills have ‘mechanical’ electrically actuated brakes to eliminate excessive speeds of the blades.

What is the real facts with that?

I wish wind power was more practical as I did love to try it but it isn’t consistent to be cost effective at my location- but I’d still
like to know the answers to the braking problem

 

[Smokin]

Shorting the Output on the windturbine redirects the output to 0 volts. So the wind turbine is charging at 0 volts. So it rotates real slow. The airfoil is in Stall. The windforce to spin it up in Stall is very high. Wind Turbine 101. There is no abundance of current because the blades are Stalled. There is little torque and so little current even at high wind speeds. There is little risk of high current damage. Tip speed is tuned for around 90 mph in trim and a true wind od 20-25 knots. Adding a long wire run will change the tip speed to well above this making the tip speed well over 90 mph. The blades will be under trimmed and will make alot of noise. Alot of tower installs have this problem as the windturbine is too far away fron the controller and load. These thing were originaly optimized for Yachts. With short Cable runs. Using a dummy load doesn't protect the windmill from overspin unless it has a low resistance and can bring the wind turbing into a stalled state.

 

[12VoltInstalls]

Using a dummy load doesn't protect the windmill from overspin unless it has a low resistance and can bring the wind turbing into a stalled state.

So dead shorting doesn’t burn the motor?!
Why do so many say it cooks it?

So something like a finned chunk of copper or aluminum on the pole, tower, or mast that can be remotely or automatically short circuited into is- or is not- necessary?

 

[Smokin]

A dead short away from the wind turbine uses the wire as an inductor to limit the surge at the windimill. Its like regen braking on a car.

 

[Hedges]

Windings in generator heat due to current.
Core heats due to AC fields.

With resistor, some voltage drop across resistor, some across windings. Less load, turbine spins faster and catches more power, delivers more current (unless such a light load it spins faster than optimum.)
With dead short, more load so turbine spins slower.

It would seem that dead short reduces heating of generator compared to resistive load.

 

[pollenface]

A learning question: I have been told (and read, and seen youTube vids) that braking a windmill - or less commonly, water wheel- by shorting the phases creates heat and eventually or sooner damages the windmill but a “heavy” load at the voltage-controller end does not have negative effects. And that some small windmills have ‘mechanical’ electrically actuated brakes to eliminate excessive speeds of the blades.

What is the real facts with that?

I wish wind power was more practical as I did love to try it but it isn’t consistent to be cost effective at my location- but I’d still
like to know the answers to the braking problem

You're probably right although in my case the wind is rarely strong enough to overcome the brake.

 

[OffGridEnclave]

I am planning to go off grid. I will had a tesla battery system. Do I have to do something with the excess energy if the batteries are full. Do I need some type of dummy load and how would I switch over to it.

if you have a gaming pc, running some crypto is legit way to convert excess energy into $$ ..