Power Burst = Mini Grid

[justsomeguy]

This subject quickly came out of a "Anyone tried propane"? question I posted in the Alternative Fuels area, that, by the way, no one answered.  It did evolve in to all sorts of other discussion though. So I'm moving it over here in an attempt to stay on topic.

I'll be brief:

Have a 6/1 Lister?  Off grid?  Wish you were on grid every time you plug in the air compressor so that 4HP motor would start a little easier, and not blink out the lights?  Wouldn't it be great if your inverter and Lister could "gang up" and give a burst of energy to start large loads?  Wish you didn't have to have a precisely controlled governor?  Wish you could use an induction motor as your generator head, and not worry about RPM, or voltage?

Have your cake and eat it to.  All the benefits of being grid tied, combined with all the benefits of being out in the middle of nowhere, miles from the grid.  Use a Sunny Island to build your own little mini grid.  With a little creativity, (means: Hacking)  an auto-start Lister could be built and hooked up to the Sunny boy controller, and start/stop as the batteries/inverter command without human intervention.

http://www.solarsales.com.au/sunny_island.html

There's a picture, (worth a few thousand words) at the bottom of the page.

Discuss!     

[cujet]

What is the cost of that thing!

Chris

[justsomeguy]

Cost?  Don't know.  I'd assume it to be close to other "smart grid tie" inverters, but I have no real idea.  Just thought I'd toss it out there for others to explore.  It might be wonderfull. It might suck.  I don't know, because I've never dealt with one. But I have read quite a bit about them.

An inverter that keeps a mini-grid supplied with power, and can instantly inject or absorb KW from mini-grid to a battery bank to maintain frequency stability, while providing voltage support... welll.... It seems like it would solve a few problems all at once!

Rather than trying to deal with generating AC power with a Lister and having tight frequency and voltage control, plus surge ratings to handle large loads, and dealing with battery charging, then switching to inverter power when the Lister is turned off, and having surge capacity in the inverter, this kind of is the best of all worlds, is it not?

I do know that they're used in remote off grid places though.  I've read many such articles in various renewable energy trade magazines where they've been used as the corner stone of "the grid" to provide stable 24/7/365 power to/from battery banks, and various 'grid tie' solar inverters and 'grid tie' engine generators and 'grid tie' wind generators, and/or micro hydro supply the energy. 

All of the loads were typical grid loads, and all of the generation was grid tie.  But instead of the grid being "everything on the utility side of the meter" the grid was actually a pile of inverters and a large battery bank.

-Jerry

[GerryH]

Hi justsomeguy,
I am planning to retire in 5 years, or less and this is exactly what I have planned to do.
This is not cheap. "free"energy is not free, and hydrogen won't run the world til we find free electricity to make it.

However, this is my way of looking at it.
If I go and buy a new Dodge diesel pickup in Canada, I can spent $45000. As soon as I take ownership I have lost 20% in Value, in 5 years I have lost 50% in value and it goes downhill from there. BTW, thousands of people do this every year.

If I take the same dollars, and invest in a combined solar, wind, and diesel system to charge a battery bank, in 10 years it will have paid back $16800, (or else I will pay this, in todays prices, to the utility.) that is discounting the possiblity of a rate increase. Do you think power will stay at this rate?
The sum of $45000 will build you one Jesus honking big system. $20,000 will build you a deluxe system. The batteries, if you are going to do this right, are going to be one of the biggest costs out there.
If I do this now, befor I retire on a fixed income, it will pay me in my later years, instead of me paying them.
That's why I bought a Lister, and thats why I am building a wind plant.

Gerry

[Tom]

Hello Gerry,

Actually the batteries are rather cheap. Unless you want something fancy like sealed ones. I'm in the process of building an off-grid home and here is a general break down of the costs 3.2kw of PV modules $15K, complete power panel with 2 5.5kw inverters $9K and 40 350 amp hour batteries at $8K.

The Xantrex inverters will do almost every thing the above mention system does except for the 3 phase power. In addition it when when the gennie is running it will power the loads and charge batteries at the same time.

[Procrustes]

Hello Gerry,

Actually the batteries are rather cheap. Unless you want something fancy like sealed ones. I'm in the process of building an off-grid home and here is a general break down of the costs 3.2kw of PV modules $15K, complete power panel with 2 5.5kw inverters $9K and 40 350 amp hour batteries at $8K.

The Xantrex inverters will do almost every thing the above mention system does except for the 3 phase power. In addition it when when the gennie is running it will power the loads and charge batteries at the same time.

Tom,

I'm considering a system almost exactly like that.  Did you study the longetivy of inverters?  This was one concern I had.  The other was battery maintenance and hazards.  I'm on the grid so it's hard to justify the cost of solar, but I'd very much like to do it.  Do you mean the power panel is a separate component from the inverters?  If so, which power panel did you choose?

Thanks.

[Procrustes]

However, this is my way of looking at it....

I agree.  I think a practical engineering project will suit me, and it's an insurance policy against grid failure like what we saw in the NE US a few years ago.  Events like that are sure to occur again, and the real and indirect costs can be high.

[Tom]

Hi Procrustes,

I have not purchased these items yet, still have to pore the foundation yet! The complete power panel includes disconnects and fuses for the batteries and 120V out. The inverted power will then go into a standard household service panel. The inverters are built heavy duty for continuous service. I've had a Trace, now Xantrex, SW2512 inverter since '98 and have had no problems with it yet, but it was just used for backup power in our prior home. 

[Procrustes]

Hi Procrustes,

I have not purchased these items yet, still have to pore the foundation yet! The complete power panel includes disconnects and fuses for the batteries and 120V out. The inverted power will then go into a standard household service panel. The inverters are built heavy duty for continuous service. I've had a Trace, now Xantrex, SW2512 inverter since '98 and have had no problems with it yet, but it was just used for backup power in our prior home. 

Thanks Tom.  Best of luck with the new home.

[justsomeguy]

Ok, so I've read more than half of the Trace (Xantrex) 2512 and 4024 inverter manuals (big print, nice pictures, better than what was on TV     ).

There is a "Generator Support" option in those inverters that would do nearly the same thing (maybe even better than?) as the Sunny Boy Island.   It takes power from a gen set, up to a max amount, and charges batteries as power is available.  As loads are turned on, it decreases battery charge to to hold the generator output at a max value.  In the event of a large surge load (or even continuos) it will instantly switch to inverter mode, stop charging the batteries, and DISCHARGE the batteries to help the gen set start a large load.  The overload capability of a 4000 watt inverter is 8000 watts.  Combine it with a  4,000 watt generator head, and there's 8000 watts continuous surge (until the batts go dead) and 12,000 watts 5 second intermittent surge.

So with cool inverters like these, why on earth would anyone want to oversize a generator at all in an off-grid situation?  The only reason that comes to mind is a long term use of higher power for hours on end that a fair sized battery bank couldn't support; Air Conditioning. 

Plus, the Xantrex has relays available that can interface with a lightly modified Lister to activate an add on fuel solenoid valve (for run stop) and a starter motor for cranking, and automatically activate fuel, crank the starter, and disengage starter once the generator volts come up to a set point. It will watch battery voltage, and start and stop the generator, and even has a setting to prevent it from starting up at night.  That's pretty nice!

[Tom]

And that's not all with an electric start generator, it will exorcise it on a regular schedule, start the the generator when the batteries get low and start the generator to handle an overload. Quiet times can be programmed in so you don't disturb the neighbors with the beautiful sound of your lister at 1 am.

Now I'm going to have to work on the air powered auto start. 

[cujet]

has anyone actually tried a grid tie inverter with a lister? The uneven output of a lister (think light bulb flicker) may be an issue?

Chris

[trigzy]

Why oversize a generator when you can get an inverter like this?  Cost!!  Look at the price tag on one of those units and a couple of batteries.  My whole 25/2 & 20kW cost less than that.  However, they are a REAL nice product - and I want one.........bad..

Steve

[rgroves]

Cost is always an issue, no doubt.  The Xantrex SW series is still priced high compared to other inverters. But there are other capable inverters that may not have all the features but still do the job.

Using the Xantrex as an example, though .. the inverter can take the uneven output from your generator and continue to charge batteries with it.  The inverter itself has a very well regulated voltage and frequency output, so the power will be a lot cleaner. Xantrex inverters will automatically disconnect from the AC input if it gets too far out of spec. You could wire the house so your sensitive loads ran on inverter power and your resistive and induction motor loads ran from the generator or in combination with the inverter.

The advantages?  Redundancy, so if the Listeroid goes down you're not sitting in the dark. 
And you'll have the ability to shut down the Listeroid for the night.  An unattended inverter won't run away and throw cast iron shrapnel around. And it's silent.
Get a good set of batteries, sized to allow growth of your electrical demand, and you won't be replacing them for many years. Maintenance on lead/acid batteries is simple, just clean the contacts and keep them watered.

Why oversize a generator when you can get an inverter like this?  Cost!!  Look at the price tag on one of those units and a couple of batteries.  My whole 25/2 & 20kW cost less than that.  However, they are a REAL nice product - and I want one.........bad..

Steve

[GerryH]

Hi Tom,
   I am thinking of the 2200 amphour Surretes made in Canada here, 20 yr guarantee. I would need less of them to get what I want. I also want to have the MPPT type Xantrex, as they can convert varying voltage from wind and solar  to a charge voltage better. I'm sure this will open a can of worms, but heck, as long as it works.

Cujet
I contacted Mike Montieth reguarding the flicker and this was his comment:
   I'm using a military Generac 7.2 kw three phase generator. My lights don't flicker. I suspect this is a ST problem that could probably be remedied easily by adding a reactor to the circuit. A reactor stores and smooths the output  of the generator. A simple reactor would be to run the output through a transformer, with nothing attached to the transformer output. The 60 cycle would alternately charge and discharge the magnetic field of the transformer acting similar to a capacitor in a dc system.
 
   Reactors were used in arc welders to smooth current, and are available in various voltage and amperage configurations. All they are is a coil of wire on an iron core, but the coil must be heavy enough wire to carry the wattage of the gen.

Gerry