Store Your Own Juice

sfeinstein writes "Power companies using dynamic pricing models to charge more for electricity during hours of peak usage is nothing new. Now, however, one company has decided to take advantage of this by using technology to buy (and store) capacity when rates are low and use that capacity when rates are at their highest." From the article: "The device, called GridPoint Protect, is the size of a small file cabinet and connects to the circuitbreaker panel. (The company also offers a lower-capacity version designed for homes, which costs $10,000.) A built-in computer powered by a Pentium chip will make intelligent purchase decisions, buying when prices are low, then storing the electricity for later use. That will make it possible to run your company during the workday with cheaper electricity that you purchased at 3 A.M."

How does it know?

[the linux geek]

How does it know when prices are "low"? Does it have a hardcoded database that will be inaccurate in a few months, or does it observe-and-compare prices?

Re:With intel inside

[Carnildo]

Just think about this thing for a moment... $10K for a home unit. How much power are you using to make that worthwile?

Assuming it cuts my electric bill to nothing, the $10000 home model will pay for itself in...just under 25 years.

No thanks.

Why bother? Pump power BACK into the grid instead

[tfurrows]

Why even bother offering a home product at $10k?

Besides, people should be thinking about generating their own power and pumping the surplus back into the grid, running their meters backwards (a legally protected action in most states) at a cost to the power company.

These are called intertie systems, and power companies are federally mandated to allow them:

http://www.google.com/search?hl=en&q=solar+interti e [google.com]

I wonder how that'd work up here

[digitalsushi]

Here in NH, our power company, PSNH.com, is overburden by its customer base. Lately they have been doing free energy audits to locate places people are losing money on heating and cooling. Both my residence, a 200 year old mill building, and my employer, a large interoperability lab, were audited by PSNH for heating and cooling, and in the case of the lab, other weird places we waste power. At my residence, they paid 80% of the replacement costs for new windows, in an effort to avoid new infrastructure. They simply can't afford to build anything new that generates power. And the overages that they have to supply all come from Canada, which costs them enough that it isn't worth it for them. So I would have to suspect that they would love it if people in their customer base were to install these, as it would just put their peak output down and give them some breathing room. I have to admit I don't know what it's like elsewhere in the world, but maybe some other people would share too.

Great, now please talk to me about those gel cells

[HiyaPower]

Real good for the environment. The impact on digging up the lead is real small and the problem with disposing of them afterwards is real low. (Yeah, right) Oh, by the way, you gotta use a lot of lead in a deep cycle battery like that. This is not something that you float along and do backup off of every once in a while. This is the kind of stuff you have to use in a golf cart. Better known as marine batteries, these things need real thick plates or they warp under the charge/discharge cycles. And while you are at it, please remember that your number of charge/discharge cycles even on a wet cell (and a gel cell is a wet cell in the end) is reasonably limited.

Not exactly a friendly way to deal with things. A better usage of the money would be to put up some solar panels and do a little cogen.

Re:With intel inside

[tomhudson]

The other problem being that if enough people go to this, then there suddenly IS no off-peak period, and no slack in the system that can absorb a jump in demand.

End result - a more fragile power net for everyone.

This post brought to you by the law of unintended consequences - just like almost everything else in life.

Re:Mass Usage issue?

[linuxwrangler]

It's worse than that. My former roommate used to work for a company that built high-tech meters that would report use, outages, etc. in near-real-time and, conversely, the spot rates could be reported back to the meter.

Now imagine what happens when big industrial users start up and shut down based on spot pricing. Demand increases -> rates increase -> plants shut down -> demand drops -> rates drop -> plants start up.... Rinse, lather, repeat.

Each customer will have different profiles of price sensitivity, startup/shutdown delays, costs of production pauses and such. It's impossible to quick start/stop a refinery or chemical plant, hard to switch your manufacturing plant on and off, but if your building air conditioning uses an ice storage system (make ice when rates are cheap, melt it when costs are high) then you can flip on and off pretty much at will.

Managing the effect on the grid turns out to be a difficult problem.

But at $10,000/home, this thing isn't going into mass usage.

just saw this a Universal Studios Orlando

[ScrewTivo]

I chaperoned my daughter's 5th grade class field trip there. The HULK roller coaster uses 2 15,000lb flywheels to store energy and then blasts out electricty when a coaster is launched. This keeps their peak value lower than it would be otherwise. Best part is we got to go to the front of the line after the back lot tour.

I also read that the NYC subways were testing flywheels for breaking energy storage. The flywheels are to be located at the stations, this way the trains didn't have to carry the flywheels.

It is way past time we made flywheels do more work.

Won't compete with PV

[linuxwrangler]

For $10,000 they offer a marginal reduction in rates. (Hell, if borrowing money were free and this thing saved 100% and needed no maintenance and was 100% efficient it would still take me a decade to recover the cost.)

If I had $10,000 to throw at the problem I'd install $10,000 of photovoltaics. No batteries, just run the meter backwards during the day when power is needed most anyway. And I'd be contributing to production not just shifting my consumption.

Re:With intel inside

[ackthpt]

This is something that I believe is probably for businesses, not really a home-use thing. Plus, ya'll didn't have Enron fucking you over on your powerbill for a few years. California got ass raped....

Ah, how I remember the rolling blackouts. Our plant diesel generator would kick in shortly after we got a phone call telling us it was us on the next blackout.

Yes, I do live in California and I was working in San Jose when it was happening. You could tell the president of the US didn't give a rat's ass about the technology sector.

Re:Mass Usage issue?

[evilviper]

Because of efficiency losses, using such devices will necessarily increase total energy usage;

The more energy you're pushing through the transmission lines at once, the higher the line-losses, so that works in your favor.

so in the limit case they increase overall prices and eliminate price fluctuations.

Electricity would be cheaper if plants could be kept running at a constant level all day and night. When you have to build a couple power-plants that only need to be operated during peak demand, that's wastes a lot of money.

I'd expect the energy companies themselves to build storage systems and use them to store energy when demand was low and deliver it when it was high.

It's entirely possible that this is something which will only work in a distributed fashion, and can't be centralized very well. Again, line-losses may be a factor.

Re:How does it know?

[superdoo]

Why wouldn't it check an online service like http://www.theimo.com/imoweb/marketdata/marketToda y.asp [theimo.com]

?

This device would be easy on the grid

[nixon]

I work at a company which manages the power grid for all or parts of thirteen states. This device would work to even out the load curve. I know the dispatchers in the control room wouldn't mind a flatter load curve during traditionally high load periods. That said, I don't see this being very useful for single family homes at the price points mentioned. Multi-tenant units could benefit if they would be willing to aggregate their metering.

Re:Storing juice?

[Anonymous Coward]

Besides the cost, I see this being a huge benefit to reducing power load on the grid. I suppose the real question is, why don't power companies do this further up the pipe, at the generating stations?

They do -- but batteries don't scale well into the megawatts or gigawatts, so they have to do things like fill water-reservoirs high in the mountains during the night and drain the water through a turbine-generator during the peak time. There are lots of other ways to do this, but none of them are trivial.

Power storage technology?

[sshore]

I scanned through the article, but didn't see this mentioned:

What kind of power storage technology is used for the $10k "filing cabinet" model? How much capacity does it have? What's the round-trip efficiency?

If it uses batteries, what is the lifetime of the batteries? Many battery technologies have a severely limited charge-discharge cycle lifetime.

I answered some of my questions from Gridpoint's site:
- Gridpoint sells these in 7kw and 10kw capacity
- Price is between $9k and $19k MSRP. The 7kw model is likely the $9k model
- The batteries are VRLA (Valve Regulated Lead Acid)
- Rated capacity is 10 hours at 1kW AC Avg Load. That's 1000/120 ~= 8A load, about half of a single 15A household circuit. This unit isn't rated high enough to run a typical hair dryer.

I couldn't find details on what kind of lifetime to expect out of the batteries.

Re:Well, there's a good chance he's right

[Anonymous Coward]

Currently, I'm designing software for a welder for a client. 99% of the time - all you do push a single button, and off she goes.

I did the same thing for an automated welder in the 80's. You would enter the weld type code on a keypad and it displayed various status on an LCD, adjusted the feed rate for autofed welding rod and flow-rate of the gasses, had a temp sensor and even auto-ignited.

68HC05 @ ~2MHz (IIRC), no o/s or kernel, about 50 k of ram.

The OP's sentiment is right.

Cringely's essay from years ago

[ssuchter]

PBS pundit Robert X. Cringely wrote [pbs.org] about such devices years ago and presented a reasonable argument that they are a solution to the California energy crisis, but that it won't happen. Basically, he said that the cost to California to equip 10x more houses than the rolling blackouts consume would be less than the cost of building new powerplants. I haven't checked his math, but it seems reasonable that last-mile caching (this is effectively similiar to other caching-type solutions) would really help solve this problem.

I wonder if there are appropriate points in the traditional power grid system where power-storage systems could be used to buffer enough stuff over 24 hours to solve this problem. Gigantic flywheels [wikipedia.org] near your block, poised to clobber through the neighborhood, anyone? I suppose this problem has already been studied. [wikipedia.org]

Re:Nice idea, but the cost...

[tomhudson]

Not only is the summary wrong - so is the friggin article.

I went to their home page and downloaded the pdf.

Here's the deal - BATTERIES NOT INCLUDED!!!

The ten grand buys you a switch. That's it. A switch controlled by a computer, and an inverter. You still need to buy batteries (that will give you a grand total of 1 kw for 10 hours, so forget about running more than a couple of computers off this).

They're trying to sell you on buying a bunch of solar cells (NOTE - NOT INCLUDED IN THE PRICE EITHER) that you connect to the switch, and depending on their output, you either suck off the sun or the power grid.

Their big marketing scam - TAX CREDIT of $500 - $2500 for Solar Power Systems.

In other words, you can do this yourself with off-the-shelf parts - buy one of these http://www.apcc.com/resource/include/techspec_inde x.cfm?base_sku=SU5000UXINET&tab=features&ISOCountr yCode=us [apcc.com]for under 2 grand, and with the other 8 grand, buy a sh*tload of batteries for it, and you're ahead of the game cost-wise. Heck, buy two, phase-lock them, and you can run your washer and electric dryer at the same time - something you can't do with their $10,000 system (which is really a lot more after you add the batteries).

Must not scale well.

[Kadin2048]

Maybe the technology doesn't scale well?

I'm not sure exactly myself, but it's not so wildly out-of-the-box an idea that nobody can have thought of it before. I assume there's something wrong with the economics of doing it at the generating station. Maybe it has to do with going down from typical generation voltages to something that can be stored and then back up again? (That would be the problem using batteries...) Other large-scale forms of energy storage, things that could store real MWh's, might be impractical.

Actually, when you think about how hydroelectric power plants work, they do this already: they build water up behind the dam when demand is low, then open the gates further and produce more energy when demand is high. I know it's not the kind of "storage" we're talking about here, but most power plants have some form of output regulation; it seems like the power companies are probably trying to match demand as closely as they can, from their "top down" perspective, but can only get so close.

By putting small storage devices out at the edge, close to the points of consumption and where voltages are low, you might get a lot more effect than taking the same amount of storage and putting it all upstream.

Re:How does it know?

[Matt Perry]

The companies where you buy your electric power from provide this data, usually as some kind of feed on a web page, and I'm sure in a machine readable format as well. I know that during the summer our energy manager person in facilities will be watching this number change about every 5 to 10 minutes and will shed load via some method like turning down the AC to avoid peak. During the summer we generate about 50% of our electricity via a cogeneration unit that's powered by natural gas. That heats water to steam to handle the generation and the steam is recaptured and used in our absorption chillers for cooling the building.

A better option for the near future

[Michael Woodhams]

It becomes much more economic if you already have the batteries sitting around for other purposes - i.e. in your hybrid car. Plug your car into the mains when you're at home, and let the computer decide when to charge and discharge the batteries. (This isn't an original idea - it is from a recent Scientific American article.)

Nothing big.

[dcapel]

This is nothing big -- the Swiss have been doing it for years. They simply buy power off the French grid at night from the nuclear plants, and then use it to pipe water up a mountain. Once the peak hits, they let it down to power hydroelectric plants, selling energy back to the French -- for profit.

Clever bastards those swiss ;)

Re:Savings? (and battery costs)

[Anonymous Coward]

Grid Point [gridpoint.com] describe their products as back-up power sources and renewable energy systems, i.e. a long run UPS system. The idea of saving money by buying off-peak power and using it during peak demand times requires a huge price differential to break even. Here's why.

Energy storage is a bank of "gel cells" (valve-regulated lead acid batteries). The bank is rated 310Ahr at 48V, which would sell for about US $1000-$1500 (based on 12 each 12V, 105Ahr batteries at $80-$125 each). The system capacity is 10kWhr. With proper charging and care, battery manufacturers claim they will last 700-1000 cycles at 70% depth-of-discharge; call that 2-3 years of daily use. So that's 7000-10000kWhr before buying a new battery bank. You will pay $0.10 to $0.20 per kWhr just for replacement batteries, excluding installation labor and disposal fees for the old ones. This is in addition to the costs of system inefficiencies that others have noted. If your peak/off-peak differential is less than the amortized battery replacement cost, you never break even--even if the unit is free and 100% efficient.

The article's claim of $375/month savings (15% of $2500) is not likely to occur for one 10kWhr unit. Thirty daily cycles would be 300kWhr per month, requiring peak/off-peak savings of $1.25/kWhr above and beyond the cost of internal power losses and battery replacement.

There are good reasons for using battery energy storage: avoiding down-time and having power at off-grid locations are two major ones. But actual cost savings are rare. The off-peak price discount seldom will pay for battery replacement and system power losses.

Posted anonymously, for professional reasons (I need to keep my job!)