What's the biggest off-grid/backup system you've seen?

techntrek · August 2011

With the impending fun times of Irene, as she readies to mow down the East Coast over the next few days, I got to thinking about the backup system they have here at work (after making sure my system at home is ready). Which got me curious about awe-inspiring residential and commercial systems that any of you have seen. PV/battery/genset, whatever. Stuff that would be overkill 99% of the time but due to deep pockets, business needs, a big home, etc., its out there and is ready to crank out some electrons if needed, or does every day.

A little "PV porn" if you will.

My system at home doesn't fall in this category by any means, but the one at work is nuts. It takes "n+1 redundancy" to the limit. First, they've paid the local electric company $$$ to bring two separate trunk lines here, coming from two different substations. Only one is needed at any time and if one goes down they can switch to the other instantly.

If the power does go out they have a huge room full of batteries and commercial-grade inverters which can carry all 20,000+ computers for a minute or two until the gensets power up.

Which consist of three jet powered gensets (not kidding), any one of which can carry the entire campus including the computers, lights, environmental, etc. During an outage or possible outage (they will probably move the campus to this system by tomorrow morning and run it most of the weekend) they'll have two of them running, one with the load and the other on hot standby. The third will be in cold standby. You can always tell when they are doing their monthly system test because there will be the smell of jet exhaust in the air and the whine of the turbines in the distance - like being at the airport but without the baggage.

Like I said, n+1 to the max. < drool > So tell me about the 30kw PV system at the mansion down the street, or the cousin that bought a 30kw diesel to power their trailer.

Ralph Day · August 2011

Re: What's the biggest off-grid/backup system you've seen?

My home system is 2.1kw pv, 1kw wind turbine, 10kw diesel genset. Normally I don't even know the utility is down until someone tells me...we run as if still off grid (see signature). Enough fuel in storage to last for years at usual consumption rates, months at severe consumption rate (solar/wind/batteries down).

Your work scenario sounds interesting, military or government I'd suspect. If Irene causes major problems are the drones going to be sitting at the 20,000 computers? Will they be able to get to work? Someone really scared with a really big budget must have implemented that backup system:D

Ralph

RandomJoe · August 2011

Re: What's the biggest off-grid/backup system you've seen?

I work on commercial HVAC systems, and have gotten to see a variety of backup systems over the years. Mostly just generators, of course. Hospitals are often done as you (OP) describe. Two feeds from different directions on different feeders, big set of generators to power the buildings.

What shocked me at one hospital, talking with the maintenance staff about uptime, is their utter reliance on some level of infrastructure should a disaster occur. If they lose all power, they will have to have a tanker truck arrive every day or two to refill the diesel tanks! Really, if it's bad enough to take the grid down for multiple days, I'm going to bet it's hard to get a tanker into the area as well... Granted, that's a pretty extreme event here in the center of the country, but still...

(Wandering OT a bit...) That hospital also provided a great example of how many things there are to think about in a disaster. The water main broke near the hospital. City was working on it, but it took most of a day. Not only was that a real problem inside the hospital, for obvious reasons, they were also scrambling to keep the AC online! (This was the middle of summer.) Thing is, the chillers use water - and evaporative cooling - to expel the heat. So they again had to have tanker trucks of WATER pulling up every few HOURS to keep the towers filled with water and the chillers online!

The most fascinated I've been with backup systems was during an interview fresh out of college. The company designed and installed factory-scale UPS systems. We're talking enough batteries / inverters / infrastructure to keep entire factories full-time "on battery"! They also did the more mundane generator backup, but their specialty was for places that didn't even want the few-seconds "blip" during transfer to generator. All power into the building went through the battery bank, and in an outage that kept things going long enough for the gensets to get running and feed power in.

That's also where I learned a bit more about REAL power - "have you worked with high voltage before?" I'm about to say yes, thinking of the 480V systems I'd worked on during school, when he added "first let me ask what you think 'high voltage' is?"

No. I have NEVER gotten ANYWHERE NEAR their definition of "high voltage"!

nsaspook · August 2011

Re: What's the biggest off-grid/backup system you've seen?

Check any semiconductor plants backup/ups generator system. You just can't lose all power for even a fraction of a second or really bad things happen (like months to restart the plant). The UPS powered critical system might be several hundred kW with generator backup of at least 1 mW with a weeks supply of fuel.

http://blog.vdcresearch.com/industrial_automation/2010/12/a-few-thoughts-on-the-recent-toshiba-power-outage.html

westbranch · August 2011

Re: What's the biggest off-grid/backup system you've seen?

look at page 9 of this doc for a really impressive battery bank....

http://www.sandia.gov/ess/docs/pr_conferences/2001/ChristopherJohn.pdf

2 strings x 378 modules x 3 cells per module x 1600 Ah per cell (8 hr) x 6 V =

21,772.800 KWh

chevenstein · August 2011

Re: What's the biggest off-grid/backup system you've seen?

It was never built, but a firm I worked for some years ago had bid a cogen plant (combined heat and power from a single large gas turbine) that had a black start requirement, meaning it had to be able to start up without grid power then run islanded from the grid. Normally not a big deal...but this was a 50MW plant. Our proposal included a 2MW diesel genset for black starting, which was the minimum capacity required to both run the balance of plant equipment (mostly pumps), start the turbine, and provide a frequency reference for the turbine once running.

The biggest blunder with one of these larger installations I know of was a smaller outdoor diesel backup genset (200kW, if I remember) with an outdoor fuel tank that had been filled with fuel in the summer and was needed in the winter. The facility had not been exercising the genset, so when they needed it they learned that it was full of summer blend diesel, which was not treated with an anti-gel additive. Woops!

stephendv · August 2011

Re: What's the biggest off-grid/backup system you've seen?

This one's not small either: http://www.windandsun.co.uk/Projects/eigg.htm
12 x 5kW inverters clustered for 60kW of battery power. Nice mix of different energy sources too.

nsaspook · August 2011

Re: What's the biggest off-grid/backup system you've seen?

A historical example of backup:

http://conflicthealth.com/when-uss-lexington-powered-a-city/

http://www.researcheratlarge.com/Ships/CV2/Tacoma/CV2_rep1.html

techntrek · August 2011

Re: What's the biggest off-grid/backup system you've seen?

Ralph Day wrote: »

Your work scenario sounds interesting, military or government I'd suspect. If Irene causes major problems are the drones going to be sitting at the 20,000 computers? Will they be able to get to work? Someone really scared with a really big budget must have implemented that backup system

Government, yes. We're all here today, and I didn't smell any jet exhaust when I pulled up so I guess we're on the grid. Answer to the last question - yes!

techntrek · August 2011

Re: What's the biggest off-grid/backup system you've seen?

RandomJoe wrote: »

If they lose all power, they will have to have a tanker truck arrive every day or two to refill the diesel tanks!

Similar problem here - they have a contract with the fuel supplier at the local airport to bring in tankers with jet fuel if the worst happens.

techntrek · August 2011

Re: What's the biggest off-grid/backup system you've seen?

westbranch wrote: »

21,772.800 KWh

Now that is a backup system!

Wow, from 100% to 67% SOC in 45 minutes, supporting a 2.4 GW load (page 11).

techntrek · August 2011

Re: What's the biggest off-grid/backup system you've seen?

nsaspook - just finished reading both links, that's very interesting. I'm a little surprised that an 1800 rpm limit wasn't part of the design specs in case the ship ever had to do exactly what it did, but I see the 45 rpm over-rev didn't do any damage in the end.

What's the biggest off-grid/backup system you've seen?

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