Need Diversion Load - smaller and cooler??

[DogBonz]

Hello all,

I am installing a wind power system on my sailboat. This isn't so far off topic, this is my home it's where I live 365 days a year, and it's definitely off-grid! The systems may be a little small compared to land based homes but here goes...

I've mounted 2 windmills each rated for 480 Watts, with a max potential of 600 watts each, in 12 volts.

The system looks like this:

6. GL16 6 volt batteries with 1100ah total. Wired in Series/Parallel to delivery 12v.
   
2. x Morningstar Tristar T-60 controllers used in Diversion mode
   
4. x Sunpower 90 Watt solar panels connected to an Outback MX60
   
   

The windmills are wired direct to the batteries using 25' each of 4AWG wire.

A couple problems present themselves:

1. We only have a 5.5 gallon water heater and can use a 12 volt water heater element but due to the limited size of the tank, it will only use a limited amount of the diversion load
   
2. Limited space for a edgewound or other diversion load
   
   

I've kicked around lots of ideas but nothing really seems to fit the bill. Thought of a Peltier device but that needs a huge cooling fan, lots of area and are relatively $$. I found a stainless steel diversion plate made by a company in Italy, but again they need to be pretty big to divert a max potential of 50 Amps each.

Here's my questions/thoughts:

1. Can/should I wire the 2 Tristars to supply a single diversion load or run them independant of each other?

- my thought in this regard was to have one T-60 wired to a diversion load and the other T-60 wired to the 12v water heater element. The water heater will be fitted with an aquastat that would trigger a solenoid/relay when the tank is up to temperature. This would then divert the full load from windmill #2 to another diversion load.

Perhaps there is a better way than an aquastat for the water heater?

2. Any ideas on the smallest physical size diversion load that can be used without creating a minature oven?

Thanks for any & all thoughts suggestions & ideas.

DogBonz

[pepa]

an interesting problem. if i lived on a boat on salt water i would be looking for some way to turn all that extra energy into making pottable water or dumped over the side if storage is exceeded. pepa

[SamoaPower]

DogBonz,

"Can/should I wire the 2 Tristars to supply a single diversion load or run them independant of each other?"

It seems that many think that charge controllers can be run in parallel, whether it be with a common or separate diversion loads.

If you care about your batteries, I suggest that you don't. The primary purpose of the controller is to provide a suitable charge algorithm for the batteries. When run in parallel, without synchronization, the algorithm becomes confused resulting in less than optimum charge to the batteries.

I understand the need of higher current capacity in the controller and this issue has come up numerous times on the board. One possibility is to build a high current FET switch that would be driven by a single controller. This is my choice.

Another possibility is to split your system into two separate ones. Unfortunately, with 6 batteries, they wouldn't split evenly.

"Thought of a Peltier device but that needs a huge cooling fan, lots of area and are relatively $$."

This is what I use. Being in the tropics, any additional cooling is welcome. I use a water cooled heatsink on the hot side to also heat a water supply so all diversion energy is utilized. No hot side fan, but it does need a small pump. It handles about 45 Amps of diversion current. Cost about $65 but the junk box supplied the heat sinks. Size is about 6"x8"x3".

[ghurd]

That sounds like a good idea pepa!  A couple hundred watts could be quite a still.

My first thought was to heat sea water. Maybe a water heater element hung over the back? There must be a better way than that, but that's how I was thinking. Salt water on the element probably isn't good.

G-

[Capt Slog]

Rather than use a still, how about a desalinator.

I think most of these work by reverse osmosis (RO).

Here's one link I found

http://www.seafresh.co.uk/index.html

But I think you can expect to pay quite a bit for these.

[DogBonz]

Thanks for the input so far, we do have a watermaker (desalinator) already installed. We opted for a low power version, producing about 1 gallon of water per 15 watts of power. However desalinators need to run on a cycle and don't run very well on potentially interruptible power (such as wind dying, etc)

SamoaPower, you mentioned about problems running two Controllers. I was planning the following (don't know if the thought process is entirely on track or not):

1. The 6x 6 volt batteries are set up in 3 sets of 2 (making 3x 12 volt batteries for this discussion)
   
2. I was planning on having the power from the mills come in on battery #1
   
3. TS-60 #1 would be connected on battery #2 with it's own diversion load
   
4. TS-60 #2 would be connected on battery #3 with it's own diversion load
   
   

... or at least that's what I was thinking.

Another question I'll revisit for input here. When I originally started putting the system together I had planned on running each mill through the TS-60's and then to the battery. This I later found could cause problems with the TS-60's unable to handle the spikes and surges potentially coming from the mills. This led to the thought (and the explosion of complications) to using the Ts-60's as Diversion controllers instead. I'll contact the mill manufacturer and find out about their power generation system. If the mills created relatively clean power (without the wild voltage fluctuations) could the Ts-60's be used as Charge Controllers instead?

The mill manufacturer says the mills are designed to be able to run for several days without needing to dump their electric load. When talking with them I used the example of switching off the incoming breaker between the mill and the battery and what would the effect be on the mill if this breaker was accidentally forgotten turned off for a day or two. No problems was the answer.

With this in mind could the TS-60's be used as Charge Controllers instead of Diversion controllers? I would like to revisit the idea of using a diversion load, but maybe this is unneccesary for my application at this time.

Thanks again for everyone's thoughts and input.

DogBonz

[DogBonz]

Here's another "after post" thought.

One of the problems here is trying to figure out how to controll/divert two controllers. Is this possible:

1. Both mills are wired direct to the batteries
   
2. Only one controller is in the system in Diversion mode
   
3. Using a set point relay or a Morningstar Relay Driver, have one continuous duty solenoid on mill #1. When the batteries have received a full Bulk load, the relay trips and activates the Stop switch for mill #1, effectively turning it off.
   
4. Mill #2 continues to operate and delivery power to the battery, with the excess power being sent through controller #2 and off to the diversion load?
   
   

Does this make sense? Would it work as envisioned? Have I completely gone bonkers with this?

Thanks again,

DogBonz

[coldspot]

Well-



$0.02 !

"for some way to turn all that extra energy into making pottable water"

Something I've thought about a bit myself, and have this idea on a wayyy-back burner!

 Using a dehumidifier for just that but also a few mods to trap the water generated and save in a clean way.

 But being on a sailboat, you could run fans, pump water or many other things for just ways to use power.

[jim622]

Would this work?  

Low Voltage Heating Element

(4,000 Watts)

for $10

by Richard Lewis

Some of you have read my ebook Homemade Amp Meters.  In it I talk about using cheap metal such as zinc plated or stainless steel "all thread" or "ready rod" as a shunt for measuring amps.  You can run the current through this all thread and take a cheap multimeter and connect the two leads at a very precise distance apart, then the milivolt reading would equal the amps.  I include free software with the ebook that computes that distance among other things.

But, what I don't say in the book is that you can use stainless steel all thread as a heater element.   For instance, if you were to put in the calculator 1/4 inch stainless steel and you have the 1 milivolt (mv) setting, then it would show 1.027 inches as the result.  What that also means is that every 1.027 inches of 1/4 inch stainless steel all thread would be 0.001 ohms in resistance at room temperature.

If you take the equation Power = Voltage ^2 / Resistance, and took a 36 inch piece of all thread, then

12 volts ^2 / (36/1.027) * 0.001 = 4,108 watts.  After the stainless steel gets very hot, it increases the resistance and then puts out about 3,000 watts or so.  If you were to put cooling fins of some sort that were painted with flat black high temp paint, you could keep it at 3,500 to 4,000 watts or so.  Same is true if it were in water.

I know it sounds crazy, but people are spending lots of money on heating elements or some other load for their windmill (when the batteries are charged but the windmill is still spinning).  I've seen $25 to $80 per 12 volt heating element and they are only 600 watts.  You would have to buy 7 of these and spend $175 to $560 plus shipping just to get 4,000 watts of heating.  And those heating elements will burn up if they aren't exposed to water.  With the stainless steel, you can use it in the air for an air heater system or you can use it in water.  Coolest part is, you can go to the local building supply store to pick it up.  I found it at Home Depot.  But, make sure it is stainless, not galvanized.

I've also seen the use of light bulbs.  But remember, a 100 watt light bulb is meant for 120 volts.  If you put 12 volts through it, then you will only be at 1 watt.  So, that wouldn't work.  You could take car headlamps.  They are about 2 to 3 amps.  So, that would be 24 to 36 watts each.  You would need more than a hundred of them at $5 each.  Hmmm, still not a good solution.

You could try a 120 volt heater.  But, at 12 volts you would be at 1/10th the voltage and therefore 1/100th the power.  So, a 1500 watt space heater would put out 15 watts of heat at 12 volts.

Anyway, I hope you can see the merit of using a simple all thread stainless steel rod as a heating element.

Richard