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One of the repeating solutions that comes up when talking about renewable energy power generation and the intermittency of it is battery power storage.

This has got me thinking, it takes hours or days for gas and coal fire plants (and I assume other fossil fuel options) to fire up and so you essentially have to keep these going as power backups for renewables for when the wind doesn't blow or the sun doesn't shine.

This got me thinking, why isn't anyone talking about using energy storage for all sources? Specifically utility-scale solutions that can hold weeks or months of energy? I would think that such a solution could vastly reduce inefficiencies in all power generation as my understanding our traditional sources are quite wasteful and the energy is use it or lose it.

Maybe my understanding is wrong and quite frankly I am not sure what happens with excess energy that doesn't get used (I assume it is dissipated into the environment in some way).

It just seems to me that we could reduce costs and combine energy generation sources and need less of all sources if we can store all the excess energy we don't immediately use.

Edit (additional info): There is a lot of confusion about what I mean and intend here. First, the type of battery is not relevant to my thought process here. It could be pumped air/fluid/whatever storage as much as it could be Tesla's utility scale batteries. The point would be to store excess generated and potential energy more readily to reduce raw energy waste throughout the system.

My thought process is that fossil fuel plants don't simply turn it off and on. The oil/gas/coal keeps burning and turning a turbine, whether or not it is connected to a generator at the time or not. It takes time to turn it on and off and thus there is a lot of time that these fuels are burning and generating pollutants when they could just throw that energy that goes to the turbines which goes to the generator (if you let it) into a secondary storage that can be more readily accessible.

As my thinking continues, I suspect there is a ton of potential energy waste throughout our power generation systems. Whether it be those generators that could be generating (but would overload a system that is fully powered) or excess heat not being utilized or electricity that is (I am guessing) somehow dumped and not used.

If I am correct in my thought process then we could be storing that energy in some way, shape, or form instead of losing it. If we can store it and access it readily then we can reduce the need for so much power generation in the first place. I could be totally off base with some or all of my thinking though.

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    \$\begingroup\$ Have you heard of a guy named Elon Musk? \$\endgroup\$ – John D Feb 13 '19 at 18:19
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    \$\begingroup\$ People have been thinking about this for decades. Why do you think they haven't? Add some basic energy calculations into your question and possible solutions: pumped storage, battery, inertial, etc. and do some costings and you might see why. \$\endgroup\$ – Transistor Feb 13 '19 at 18:20
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    \$\begingroup\$ You made me think of charging some batteries for home use during off-peak tariffs and use them on-peak. But damn Elon Musk did it again... \$\endgroup\$ – Eugene Sh. Feb 13 '19 at 18:35
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    \$\begingroup\$ non-renewable energy sources (ie, fossil fuels) are already a long-term stable form of chemical energy storage. why burn a barrel of oil (chemical storage) in order to charge up a big battery (other form of chemical storage), when you can just burn the oil on demand for actual customer use? \$\endgroup\$ – Chris Fernandez Feb 13 '19 at 18:48
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    \$\begingroup\$ Gas turbines can spin up and start making power in a few minutes. A combined cycle plant with the gas turbines as the front bit can be delivering power in 10 minutes. \$\endgroup\$ – zeta-band Feb 13 '19 at 20:16
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Taking, at random, Overland Park, Kansas, as an example:

  • Population 191,278 (2017).
  • Area 195 km2.
  • Annual energy demand (per capita) 13,500 kWh = 37 kWh/day. World Bank.
  • City demand = 191278 x 37 = 7 x 106 kWh/day = 7 x 109 Wh/day = 3600 x 7 x 109 = 25.5 TJ/day.

For pumped storage the formula for energy stored is \$ E = mg\Delta h \$. Assuming we could create a pair of lakes with a Δh of 100 m somewhere nearby then we would need to move \$ m = \frac{E}{m \Delta h} = \frac {25.5T}{9.81 \times 100} = 25.5 \$ million tonnes of water to the upper lake to store one day's worth of energy. That's 25.5 Mm3 in volume.

Making a lake the size of Overland Park we would fill it to a depth of \$ \frac {25.5M}{195 \times 1000 \times 1000} = 130 \ \text m \$ which is deeper than the 100 m we suggested raising the lake to.

The point is that the energy requirements are huge and any storage system would have to be equally huge. You can find battery energy densities on Wikipedia.

Last time I looked online battery storage was a little below US$200/kWh. That requires an investment of 37 x $200 $7400 just for you and $1,415,457,200 for your city for a one-day battery backup.

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  • \$\begingroup\$ Also the average price for the consumer is 0.12$/kWh ( US Average ). So on cloudy windless days they should expect their electricity bill to go up by a factor of 1666 (At least). \$\endgroup\$ – a1s2d3f4 Feb 13 '19 at 19:29
  • \$\begingroup\$ Here's a list of the existing pumped storage installations. en.wikipedia.org/wiki/… Dinorwig, in Wales (the only one I'm familiar with) has a storage capacity of 11GWh or 4TJ - good for about 6 hours output. \$\endgroup\$ – Phil G Feb 13 '19 at 21:02
  • \$\begingroup\$ Pumped storage has the lowest energy density of anything in current use -- around 1 kJ per kilogram per 100 meters. Even notoriously-inefficient lead-acid batteries have around 170 times the density, while lithium-ion batteries are around a thousand times more efficient. \$\endgroup\$ – Mark Feb 14 '19 at 3:18
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    \$\begingroup\$ @Patrick As others have said, your basic premise is incorrect. Electric grids are actively managed to keep supply and demand balanced; if there was an imbalance between supply and demand, you wouldn't see any potential energy waste. Instead, you'd see the frequency of the grid rise or drop (in the US, the frequency kept at 60 Hz). Pumped storage is viable because they're not trying to maintain a city; they're trying to make money. They pump water up when electricity prices are cheap, and generate when prices are high. This arbitrage has the effect of decreasing prices for everyone. \$\endgroup\$ – Josh Eller Feb 14 '19 at 16:08
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    \$\begingroup\$ @Josh: There may be a problem as Patrick suggests if, for example, a substantial part of the grid is steam powered. If demand drops quickly the excess heat has to be vented as steam to atmosphere as far as I know. It can't be stored and if run through the turbines the grid frequency would rise. \$\endgroup\$ – Transistor Feb 14 '19 at 18:17
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I am not sure exactly what you are expecting as an answer, but storage has already started to be used to supplement all energy sources. Utility-connected battery banks have already proved superior to any alternative peaker plant.

This report on the Australian 129MWh Tesla battery installation's first year of operation could shed some light on it. In just one year it has pretty much recouped more than 75% of its costs (33% to the owner and the rest in savings due to its reducing FCAS market pricing by nearly 90%).

Conclusions from the report include that the battery system has contributed to the withdraw of the requirement for a 35 MW local Frequency Control Ancillary Service (FCAS), decreased the South Australian regulation FCAS price by 75%, helped connect South Australia to the National Electricity Market, among various other contributions.

That means that 35MW of fossil-fuel-powered peaker plants can be removed from the market. Given its near instantaneous response to demand, it also means that utility energy markets might start pricing speed of response differently, which will further benefit these types of storage.

Just adding enough storage capacity to sustain the grid while a fossil-fuel plant is being wound-up, is enough to provide some CO2 savings. Extrapolating from the Australia installation, savings could be at the very least on the order of 30% of the installed battery generating capacity.

Replacing peaker plants is an explicit market focus for Tesla, which as of this writing has installed more than 1GWh of utility-connected battery banks worldwide.

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    \$\begingroup\$ That's awsome but as with the cars... problems arise when you want to mass produce for the entire world. One pilot project is fine. Using it everywhere and building thousands of them is another thing. \$\endgroup\$ – Fredled Feb 13 '19 at 22:19
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    \$\begingroup\$ @Fredled a 2000km trip always starts with the first step. This is a 129MWh project out of 1GWh installed, by a single supplier, as of mid 2018. They have competition, which were already claiming more than 500MWh as of mid 2018. And, with just 2% of the grid capacity this single project had taken over more than 50% of the local peaking plant market. \$\endgroup\$ – Edgar Brown Feb 13 '19 at 22:28
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    \$\begingroup\$ @Fredled having too much demand in a market, is only a problem for you if your competitors jump in ahead of you. But it is never a problem for the market. Quite the opposite, this means that more and more battery production capacity, research, and development will take place due to the econimics. This also means that less and less conventional power plants will be built, as they have to plan for a 20yr profitability curve to recoup their costs. Those plans don't look too good if a battery system can enter the market in 10yrs. \$\endgroup\$ – Edgar Brown Feb 13 '19 at 23:03
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    \$\begingroup\$ "it has pretty much recouped more than 75% of its costs." Does the report actually state that? The quote relates to the cost that the market operator (AEMO) pays for FCAS. The cost to AEMO has lowered by 75% because there is a new provider that can supply FCAS for a lower cost. This doesn't mean that battery's owners recouped their costs by 75%. \$\endgroup\$ – Ben T Feb 14 '19 at 5:06
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    \$\begingroup\$ @blt what I am trying to say, in as few words as possible, is that if you add the ~22M$ in generated income to the owner, to the ~30M$ in utility operator savings due to the FCAS market (estimated from actual costs incurred 2006 and 2007), that alone (without further considerations such as the avoidance of load shedding and blackouts or environmental cost reduction) adds up to ~52M$ which is almost 80% of the 66M$ the battery system cost. \$\endgroup\$ – Edgar Brown Feb 14 '19 at 18:24
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Part of your basic premise is false: gas turbines can go from zero to full power in a matter of minutes. They've been used to provide peaking power for decades, since it's rare for power demand to vary so rapidly that they can't handle it. Because traditional generation capacity can be changed so quickly, there's no need to store electricity on more than a trivial scale.

The reason we're looking at battery storage (and flywheel storage, and pumped-hydropower storage, and a whole lot of other things) for renewables is that they can't be used to generate power on demand. If the grid operator sees that the Superbowl halftime show is coming up, they can instruct a gas turbine or two to start up to deal with everyone microwaving their snacks at the same time. But they can't turn the Sun on at night, or order the winds to blow harder. Hence the need for large-scale storage of renewable power.

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    \$\begingroup\$ I understand the need for renewables. The inconsistency is the obvious reasoning for it. I did not know that gas turbines could be up within minutes. I always hear about these long startup times for fossil fuel energy sources. They have to heat up the medium to produce steam to turn the turbine. The heating takes time. So it seemed to me that the problem is that the intermediate time it is burning the fuel, but not generating electricity. Or it overproduces and has to either spin down, disengage from the generator or dump the energy. \$\endgroup\$ – Patrick Feb 14 '19 at 3:49
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    \$\begingroup\$ That is the description of a steam turbine: energy source > boiler > steam > turbine. In a gas turbine, the burned gas combustion gasses go directly to the turbine blades; no intermediate conversion processes, no mechanical linkages, nuttin. One thing limiting the startup time is keeping the internal temperature rise down to a rate that does not overstress the components. \$\endgroup\$ – AnalogKid Feb 14 '19 at 5:33
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    \$\begingroup\$ @Patrick It's not just gas turbines. All kinds of conventional plants can vary their power output (it takes longer, but with the exception of nuclear plants, it's in the tens-of-minutes up to a couple of hours). They simply have to, because an unloaded steam turbine isn't a magical energy sink. It still needs to be spinning at the same RPM (given by grid frequency), so you need to feed just enough power into it or it will spin out of control and disintegrate. Conservation of energy then dictates that you need to throttle down the boiler to match the load. \$\endgroup\$ – TooTea Feb 14 '19 at 13:28
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    \$\begingroup\$ @Patrick And the startup time of several days only applies to starting a cold plant. Throttling several coal boilers up by a percent can be done much faster and will handle most of the load fluctuations. It's not like the load on the grid jumps up and down like crazy, it can be predicted very well. \$\endgroup\$ – TooTea Feb 14 '19 at 13:30
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    \$\begingroup\$ @Patrick And to address the last misconception: There isn't a pile of coal in the boiler that will just keep burning no matter what. The coal is fed into the burners as coal dust mixed with air, so if you just turn the feed fan down, less fuel will be coming in and the heat production will drop immediately. It'll then take a while before the steam production drops due to the thermal inertia of the system, but that doesn't mean that there's any unnecessary burning and pollution in the meantime. \$\endgroup\$ – TooTea Feb 14 '19 at 13:42
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One thing about batteries is that they cost energy and materials to build them. The more storage capacity you need, the more it costs.

As things are now, energy is stored in the fuel - huge oil tanks, train wagons full of coal. The fuel consumption rate is matched to the output power.

The coal and the oil come from the ground though. The ground is like a huge storage bin for all the fuel, and we extract the fuel as we need it.

So, we already have massive scale, high energy density, storage of energy in the form of the raw fuels.

Even the sun can be viewed as a gigantic storage of energy.

Solar/wind power is commonly paired with batteries because of the intermittent source of energy. Night, clouds/weather can reduce the amount of available power. But if we had a worldwide network of solar panels/wind turbines, we wouldn't necessarily need those batteries - it's gotta be sunny/windy somewhere.

One advantage of battery storage is the capability of having a higher power output than from the generator charging the batteries. For example, a generator which can produce 1 kW charges a 1kW*hr battery. If that is all the generator is doing, it takes 1 hour to charge the battery, or maybe it takes several hours and the generator powers a few other things. Once the battery is charged though, it can provide more than 1kW of power. It could provide 2kW for half an hour, or 4kW for 15 min. Or maybe it powers a laser for a brief moment.

Grid scale storage is done with dams and hydroelectric. If more power is needed, generators come online. Are batteries necessary? Are they the best form of storage? It's debatable - are they the most cost efficient? what is their max power output? how long do they last? how much additional infrastructure would be necessary to incorporate battery facilities into the grid?

We are doing what works, and will continue to do that because it works. Having fuel as energy storage is more energy efficient than making the electricity and storing it in batteries and then inverting it when it's needed. And because the fuel already exists deep in the ground, we don't have to build storage facilities for it, we just have to extract and transport it.

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  • \$\begingroup\$ You remind me of my pet peeve: our oil and gas production. Production? What did we make it out of? How did we produce it? A better word would be EXTRACTION. Once we extract it, it is gone forever and cannot ever be replaced. \$\endgroup\$ – richard1941 Feb 14 '19 at 18:15
  • \$\begingroup\$ It should be a law somewhere: any praise to fossil fuel, regardless of how well-reasoned it is, MUST be accompanied by the caveat that if we release all of that stored carbon into the atmosphere then humanity would cease to exist. \$\endgroup\$ – Edgar Brown Feb 14 '19 at 19:00
  • \$\begingroup\$ I was just trying to make the point that energy is already stored in a variety of ways and we just have to extract it. Why should we extract it just to store it again (in a battery)? Not just for fossil fuels either, we can continue to extract energy from the sun for a LONG time, it's like a gigantic compressed hydrogen storage tank, fusion reactor, and radiation energy transmitter all in one. With batteries there is loss here and there,with internal resistance, and first from rectifying to DC to charge them, then inverting from DC back to AC to use it. It was already energy stored as fuel! \$\endgroup\$ – jreese Feb 14 '19 at 19:17
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Because it's terribly expensive. The idea is there. Many ideas to store energy are in the cartons (spinning wheels, artificial lakes, weight lifts...) but none are commercially viable or enough efficient. Or as Tesla's pilot project in Australia (see answer from Edgar Brown), it's not realistic on a global scale. Batteries don't work eternally. After a few years you have to replace them. Raw material are scarce. Environment hazards. etc.

That being said, laboratories search for more efficient batteries. Fluoride batteries look promising. Unfortunately as always, these marvellous discoveries don't go beyond the newspaper report. 10 years later we are still with Li-ion. Let's hope one day we get them.

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    \$\begingroup\$ Nothing works eternally. Gas turbines need to be replaced every 20yrs, the total lifetime of a power plant is 30-40yrs. At least battery systems, with their briefcase-sized battery packs and modestly-sized units, are modular and easy to expand and upgrade. The Australia "experiment" is bound to recoup its costs to its owner within just 3yrs (it already has for Australian society, if you consider the savings of the 90% price drop it imposed in the peaker-plant power market). Compare that to the typical cost recuperation of a conventional plant that exceeds 20yrs. Expense is not the problem. \$\endgroup\$ – Edgar Brown Feb 13 '19 at 22:58
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    \$\begingroup\$ Pumped-storage hydro-electrical plants do exist and work (en.wikipedia.org/wiki/Pumped-storage_hydroelectricity ). In fact, some of them were built not to store energy from renewable continuous sources but from nuclear power plants. \$\endgroup\$ – Pere Feb 14 '19 at 16:53
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Co-generation and large UPS people have worked through most of the available alternatives. Batteries are the second worst way to store excess electrical energy (only capacitors are worse). In round numbers, the batteries to power the Empire State Building for one week would be the size of Central Park (all of Central Park) and 50 feet high.

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    \$\begingroup\$ Now that just ain't true. The Empire State uses 55 million kWh/year or 151,000 kWh per day. A big car battery is about 1 kWh. The ESB has 208,000 square meters of floor space. So it could be powered for a day by putting one battery in each square metre of each floor. Inconvenient but there would still be room to walk around. \$\endgroup\$ – tomnexus Feb 13 '19 at 21:09
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    \$\begingroup\$ Well, AnalogKid just means that these battery storage would be huge by size. How huge exactely is not important. \$\endgroup\$ – Fredled Feb 13 '19 at 22:34
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    \$\begingroup\$ That seems unlikely to need that much space. Given the abilities of existing utility scale batteries and the amount they serve. \$\endgroup\$ – Patrick Feb 14 '19 at 3:50
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    \$\begingroup\$ Blatantly false, a quick back of the envelope: The Australian Tesla "Megabattery" 129MW/h can fully power the Empire State building for more than a day, so you need less than 7 of those for one week. The whole megabattery occupies much less than 2000 \$m^2\$ and is shorter than a container @2.2m. So let's say \$20*10^3 m^2\$ for 7 days of storage with plenty to spare. Central Park is \$ 3.4*10^6 m^2\$ or 170 times bigger. So, you are more than two orders of magnitude off and that is completely ignoring the factor of 6 in height and all of the extra padding I put in the calculations. \$\endgroup\$ – Edgar Brown Feb 14 '19 at 18:55

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