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Dealing with irregular electricty supplies

Dealing with irregular electricty supplies

Dealing with irregular electricty supplies

(OP)
Almost all forms of electricity generation that extract energy from environmental sources are highly variable in their output, depending on the weather, and in the case of solar, the time of day. As these sources of energy provide a higher proportion of total requirements, either massive storage capacity and/or massive back-up capacity will be required to ensure a reliable supply. For some reason this isn't discussed much, and when it is the focus is usually centralised battery parks and pumped hydro, but it seems to me that there are two sources of distributed storage that could provide a large part of the required storage at much lower additional cost:

1) Facilities such as hospitals require very reliable backup power supplies. It makes sense for energy intensive manufacturing, computing and commercial facilities to also have reliable backup. If every one of these facilities installed additional backup capacity, that could be fed back into the grid when required this could provide a large backup capacity for the whole community.

2) When hybrid electric cars become common the great majority of them at any one time will be sitting either next to their owners' homes, or in public parking facilities at offices, shops, or public transport parking. If the cars could be set to provide short-term supply from their batteries, as well as longer term charging, this would provide a huge short-term backup for supply fluctuations, at little additional cost. For longer term backup the cars' petrol/gas engines could be used to supply the users' home supplies, or even supply the grid.

Is there anything that would make these forms of supply backup impracticable?

If not, what needs to be done to get these systems in place?

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

RE: Dealing with irregular electricty supplies

Backup power is, I think, typically provided by diesel generators. Are you proposing more diesel generation?

RE: Dealing with irregular electricty supplies

(OP)

Quote:

Backup power is, I think, typically provided by diesel generators. Are you proposing more diesel generation?

I'm proposing whatever would provide a high level of supply security with minimum GHG emissions.

I'd guess batteries for short term, with a fueled backup for long term, but I haven't done the numbers.

Why do you ask?

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

RE: Dealing with irregular electricty supplies

Just trying to understand your question. But I'll leave it alone.

RE: Dealing with irregular electricty supplies

https://www.sciencedirect.com/science/article/pii/... seems relevant. Batteries alone is unfeasible, you'd need hundreds of Tesla gigafactories working for centuries, WAG. (say tesla is 1% of vehicle market in USA, *10 for worldwide, *10 for vehicles as a proportion of total energy needed=10^4 factories), say 10 year lifespan=10^3 factories

IF hydrogen generation via electrolysis becomes cost efficient then despite its many problems it also solves an awful lot of problems. Efficiency in an engineering sense is not the criterion needed, it's more of the cost of infrastructure.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Dealing with irregular electricty supplies

I don't remember if it was Lovins, Rivkin or some other futurist, but the thinking was that all the fuel-cell cars provide power to generate hydrogen when parked. Attractive idea, really.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Dealing with irregular electricty supplies

You will have to explain how that would work, SnTMan.

RE: Dealing with irregular electricty supplies

Poorly stated on my part, but as I recall the idea was to connect the cars to the grid when parked. The fuel cells would / could provide power as needed, such as to offset the variability of renewables, etc. Don't really recall more than that. Of course this would come at the cost of hydrogen consumed. I don't think the Futurist said who pays. Net metering perhaps. :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Dealing with irregular electricty supplies

IDS -

I love your line of thinking. Looking at one of the issues with the power grid that could arise from switching over to more eco-friendly power supplies. My thoughts on this:

1) This is one of the really good things about roof top solar. Most of the time, it provides power to the home-owner at times:
a) when the owner isn't using it (because they're at work)
b) when power demand is at a peak (during the day when AC is on).

2) I wonder in what parts of the US this is of greatest concern right now?

3) My impression is that we may be kind of far away from this being a large consideration. Meaning that our grid is so fossil fuel dependent that this doesn't seem to be one of the big issues right now.

RE: Dealing with irregular electricty supplies

Quote (JoshPlum)

My impression is that we may be kind of far away from this being a large consideration. Meaning that our grid is so fossil fuel dependent that this doesn't seem to be one of the big issues right now.

I don't think that's entirely correct. We are certainly fossil fuel dependent, but wind power is already creating major challenges for the grid:

Spinning reserve or quick-starting power plants must be available at all times to compensate. This makes for a lot of redundancy and waste in the power industry.

In many cases, when wind is high, peaker plants must still operate simply to help controls vars, i.e. phase issues. Wind power is often curtailed.

Converting our grid slowly to renewable sources is a worthwhile endeavor, but also a learning process and very costly. I'm glad we're moving that direction, but I think people need to understand we're talking about a several-decade process, if not centuries - and that's just in the US. I can't imagine the challenges in China and India.

As for energy storage, I don't think batteries are the answer. Pumped hydro and compressed air are candidates, but the scale will have to be extraordinary to have a significant impact. Maybe if Trump and the dems go for that $1,000,000,000,000 infrastructure bill, that would be an opportunity, but that will come with other sad implications for the future.

RE: Dealing with irregular electricty supplies

Whilst wandering around Dartmoor trying to find an open pub I was mulling over my 1000 Gigafactories. One advantage of that approach is that it is scaleable, they don't need to all be built at once. Another is that you need one for every 7 million people, so suddenly a ludicrous number like 1000 becomes one per state in the USA, and 4 for Australia. You still need the mineral resources to build the batteries, but hopefully the recycling at the 10 year point means that's a one-off hit.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Dealing with irregular electricty supplies

In relation to electric cars: there are two approaches: the obvious "vehicle to grid" (V2G) approach where you try to use the car as a big UPS for the grid when it's parked, and another which is called opportunity charging.

Those who have solar panels on their roof and want to charge their EVs with them would need to switch to the night shift, or work from home- then what's the car for? Anyway- obviously you need chargers at work to make use of EV batteries in any meaningful fashion to store solar electricity. Most EV owners recharge at night when rates drop- here in Ontario that means nuclear and hydro power which would go to waste if it weren't used, because you can't modulate these sources quickly or easily to match demand.

Vehicle to grid schemes are attractive at first glance, and may be very helpful for true emergency back-up power- if you put me in charge, I'd mandate a basic 120 or 240 V inverter at say 15 A be part of every OEM EV for this purpose- extremely useful in emergencies and a really cheap thing for OEMs to do (but which they won't unless someone mandates it). However, no EV that you can buy today comes built-in with the bidirectional AC/DC conversion capacity necessary to back-feed the grid with power from the battery, nor are the EVSEs that you would normaly plug in to, designed to be back-fed. So what you'd need is a large number of expensive bidirectional DC/AC fast charger/inverter stations, located where people park during the day (i.e. at work)- and that's prohibitively expensive to imagine anyone paying for. Most importantly, the cycle life of lithium ion vehicle batteries is insufficiently high to make back-feeding the grid a paying proposition at reasonable retail prices of electricity- if it were, people would be building much cheaper (per kWh) stationary batteries to take advantage of this- they're starting to, but just starting.

Some V2G proponents are playing a shell game of saying that V2G schemes don't cause capacity loss or even reduce it- but they're all playing a game with the battery degradation model. Li ion batteries degrade fastest when they're a) hot and b) at a high state of charge (SOC)- so don't store your laptop or cellphone fully charged if you want your battery to last- 50% SOC is best. The V2G guys say that by cycling the battery at lower SOC and then topping up just before the driver has to drive away, they reduce capacity loss. Of course the better strategy as a vehicle owner is just to entirely avoid high SOC, stopping charge before you get there- that causes even LESS capacity loss. And EV batteries still aren't cheap- you certainly wouldn't want to replace one during the lifetime of your car.

The other option is opportunity charging. This requires no new hardware- just some software. It also doesn't needlessly cycle the EV's battery, so it won't cause any degradation nor will it waste the ~10-20% of energy lost in cycling. EVs generally already allow their onboard chargers to be controlled via a cellphone app. Connect that app to the grid system operator and have it run a mini-market. The user will punch in their desired SOC at the end of the day, and what price they're willing to pay for that electricity- and how much charge they'll take if they can get it for a lower price. The system operator then gets tons of instantaneously switchable demand- demand that is not only switchable, but which can be planned and delivered at the convenience of the grid rather than the user. All you need is some cheap level 2 EVSEs in work parking lots, and software. It's cheaper than the controls that my local utility put on my air conditioner so they can shed demand during peak periods- they paid me to install that!

RE: Dealing with irregular electricty supplies

A massive grid remake allowing power to flow from where it is available to where it is needed. By studying historical weather patterns a grid could possibly be constructed that guaranteed 99% service if paired with automatic cutoff of non critical loads. Yeah this would be a project that would dwarf any others. But it is the most certain solution. 1000 GW east west power corridor anyone.

RE: Dealing with irregular electricty supplies

All of that is a hard sell, IDS.

Quote (IDS)

1) Facilities such as hospitals require very reliable backup power supplies.
The backup power supply for a hospital or other emergency service is not likely to be adequate to support 100% of its normal energy needs - only a portion deemed as essential so there will be little to spare. With, say 1 hospital per 100,000 population in any north american city, that's a tiny drop in the bucket. And consuming the hospital's backup fuel supply because the energy grid has a shortfall in another city just reduces this hospital's endurance if the grid goes down.

Quote (IDS)

If every one of these facilities installed additional backup capacity...
You couldn't get them to pay for that on their own. If there needs to be a government incentive, or another fee for electric customers to pay, they it would make more sense for the electric company to install and manage the backup system itself, rather than foist it on hospitals, fire stations, internet providers, and phone companies, etc.

Quote (IDS)

If the cars could be set to provide short-term supply from their batteries, as well as longer term charging, this would provide a huge short-term backup for supply fluctuations...

I've heard that discussion before. I've given it some thought, too. Serious thought, in fact, because I intend my next daily-driver car to be an electric. Plug-in hybrid if necessary, or all-electric if possible. If it does seem plausible that my electric company could somehow withdraw charge from my electric car, however, I will respond in the following ways:
a) determine how to inform the electric company that doing so is not acceptable to me,
b) determine what steps are necessary to disable this from within the car, or, failing the above,
c) refuse to recharge my electric car from the utility grid by installing RE sources of my own (which I've already started doing).

Quote (IDS)

For longer term backup the cars' petrol/gas engines could be used to supply the users' home supplies, or even supply the grid
Having vehicles parked in garages starting their engines at random times without the owner's awareness is not a safe idea.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

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