Interesting post, Chuck. But the need for grid storage and the requisite infrastructure to support it seems to me to have the same limitations and issues as the charging infrastructure dilemma you've been writing about lately with EVs. Building out the grid storage will take money and physical space, correct? I'm imaging it like giant data centers all over the place, so please set me straight. Will this be funded by private industry, the government? And without it, what happens to the use of renewable energy--it hits a brick wall.
Beth, it's not as bad as all that. By using grid storage utilities can avoid building or upgrading other generation capacity. Thus, it may not be a big extra expense in the long run. In addition, this technology offers a way to make the grid more reliable. I have seen plans for batteries at the substation level. We'll have to see how the battery technology pans out.
Beth, I should have been more emphatic in stating that this is about the demand, not about what will actually happen. Lux's study is looking at plans, such as those in California (which wants to boost its renewables over 30%) and saying, "here's what will be needed." You're correct on all counts: yes, construction of these facilities will take money (public or private) and, yes, these storage centers will be very large. As for whether renewables will hit a brick wall without it: Yes, they will. The question is, when? Today, wind and solar generate about 4-6% of our electrical capacity. Experts at Argonne National Laboratory say that we will need storage when we reach a point between 10% and 20%.
Thanks for clarifying, Chuck. So we have some time to build out the grid storage and Naperlou talks about how it can be accomplished pretty effectively. I am by no means trying to poke holes in this development. As with all of this alternative fuel and renewable energy technology, it's a process and it's going to take time, money, and innovations in order to pull us over the goal line.
Rob, pumped hydro (i.e., the lake on the hill) is still our biggest source of storage today. But as commenter ehunt has so succinctly stated below, pumped hydro "has not seen wider implementation due to geological, environmental and capital constraints."
I can understand that, Chuck. I'm curious, though, as to the economic feasibility of pumped hydro compared with alternatives. I would think that once the lake is in place, the system for pumping and retrieving power via that downhill stream would be relatively inexpensive. As for the lake -- seems every community could stand an extra lake.
I don't know about the economic feasibility of pumped hydro versus batteries, Rob, largely because so much of pumped hydro's cost is dependent on the price of the land. In terms of system technology, pumped hydro has a big advantage over the acres of batteries that would otherwise be used (and would later need to be replaced). But for pumped hydro, it's always going to come back to land availability and cost.
As correctly stated, pumped storage has been the number one option for large-scale storage. It remains the number one option. There are today 75 applications for new pumped storage projects in the United States, most concentrated in the west but some in the east. Only the best of these are developable, and those best represent quite a few thousands of megawatts. The scale of these projects - from 280 MW to over 1,000 MW - is large, but so is the scale of renewable energy and the need for new firm capacity toward the end of the decade. Cost per kW varies widely from site to site, but the best will be under $2,000/kW, and some under $1,200/kW. That, combined with storage durations exceeding 12 hours and lifetimes of 75+ years, give pumped storage the lowest capital cost per kWh (with the exception of conventional CAES - see below).
As for the article's note on siting difficulty - that is not a new issue; quite a few pumped storage projects from the olden days never got built due to poor siting choices, environmental concerns, etc. Today, however, a new generation of closed-loop projects are under development, many of which avoid similar issues.
On Mr. Murray's comment - the cost of pumped hydro is not much related to the price of land because its footprint is pretty small.
As for Compressed Air Energy Storage - the only rival to pumped storage at large scale. More modular (generally, units of 135 MW); no FERC licensing required; and somewhat lower capex. CAES also has the lowest cost per kWh of duration of any storage technology - if using salt caverns. Where such geology is available, it's relatively easy to expand storage capacity to levels allowing for semi-weekly storage. The newer CAES technologies have only marginal advantages over existing CAES in areas of suitable geology. While they would eliminate the natural gas component, fuel use for existing CAES is already extremely low, and the round-trip electrical efficiency would be about the same. Using pipes for storage will also certainly be more expensive than using caverns, so while pipes would allow for wider geographic siting options, the advantage of long duration storage would likely be compromised. CAES without natural gas also shifts the economics such that it becomes more dependent on off-peak/peak price spread, which has been shrinking, rather than on moderate amount of natural gas, which will be inexpensive for some time.
The footprint will vary from project to project. Almost the entirety of the footprint consists of the reservoirs; everything else, except transmission, is below ground. For some of our typical sites, reservoirs are typically 60-120 acres each in surface area. So let's say 250 total acres, compact. Tanks with volumes of thousands of acre-feet, required to match the scale of a pumped storage plant and provide 8+ hours of storage, using normally available heads, would be too expensive and generally not necessary. There was one such project proposed in California, some time ago. Ideally one finds sites with topography that minimizes the construction involved in reservoir creation. Occasionally there are unusual opportunites like the newly proposed Maysville Pumped Storage project in Kentucky, which would use existing excavated mine space 1,000' below the surface as the lower reservoir. This dramatically lowers the cost of the project.
Thanks for the info, Matthew. I would think pumped hydro would lend itself to public/private projects, since lakes provide recreational opportunities for cities. Any city could use an extra lake. Have you seen public/private projects?
Well, sometimes pumped storage reservoirs (the really big ones) can be used for recreation. Others may not be, as the fluctuations and currents as the project drains and then re-fills don't make the best environments for fish. Plus most new pumped storage sites are quite far from urban areas.
Good discussion thread. Obviously there are lots of storage options. It will take a bit of business and risk analysis to sort it all out. The issue is that no one entity has the overall view and each industry has their personal agenda. It will take a consortium of many disciplines to steer the correct path. In the meantime, what an exciting time to live. We are at the start of a whole new way of looking at the world's power needs.
As this need grows, and it looks like it certainly will with advances in alternative energies, I would imagine there could be public/private pumped hydro projects. Certainly a lake would serve the public in many ways.
In regard to Pumped Hydro, in situations where there is constant river flow with spare energy it is agreat idea, but where the energy is all coming from the renewable source just to be stored, efficiencies can be a bit low, - the Pump will not be much beter than 80% and the Generator also, particularly adding pipe losses etc. so suddenly the cost of the renewable energy jumps alarmingly due to the wastage.
With Batteries, particularly lead acid, - preferably Tubular Positive plates, efficiency of 98% and large Inverter efficiencies also of 98% are achievable so most of your power is still there. Cheers, Geoff Thomas.
In response to Geoff, the figure for pumped storage total round-trip efficiency today is about 80%, although it will vary some from site to site. I think it's also important to point out that you wouldn't have reason to put all of your renewable energy into storage, but strategically use the minimum ratio of storage capacity to renewable capacity to create the greatest benefit.
When we run wind-storage integration models using pumped storage to create a firm, intermediate-level capacity product between the two, only about 20% to 33% of renewable output goes through storage; the rest goes straight to the grid, with the storage release following flexibly up and down.
In summary, you don't need to add 1 MW storage per 1 MW renewable, nor do you lose 20% of all renewable; you lose 20% x 25% or 30% or about 5% to 6%.
Also, in partial response to Jerry, while wind does have the most to gain from storage, solar PV also is surprisingly intermittent and can stand to gain a great deal of firm capacity value from storage. One can also shift morning output to the afternoon, when peak is generally highest (at least in the summer).
Charles - succintly put. Pumped hydro energy storage is great - but most geographically viable locations have already been built. Also, the environmental impact and large amount of water (and replacement due to evaporation) will be increasingly large barriers. Water shortages are another brewing issue like our energy problems. Compressed air storage is even MORE tied to specific geographical features (large salt caverns)...a niche at best, and efficiency and ease of energy conversion is not that good.
I've come to the conclusion after much study and thought that there are only a few likely vectors to success in grid-scale energy storage. Of course, always open to unexpected breakthroughs!
1. Solar Thermal - these powerplants store solar energy as heat (in molten salt or even large stores of sand or concrete). For short-term energy storage this is a pretty good system, since the power plant already is designed to run on solar heat. Also, this approach allows a "backup mode" using natural gas (or other fuel) if the heat storage runs out. We need to be building more of these plants NOW. However, note that heat is not the most best way to store ELECTRIC energy (such as from wind turbines), since round-trip efficiency will be only ~30%.
2. Solar (or Wind / electric) generation of a synthetic liquid (or gas) fuel. This approach needs more development work, but has great potential because you can store as much "fuel" as you want, and could be high efficiency. The "obvious" fuel is hydrogen, but I've come to believe this is not the best choice due to so many practical issues. Ammonia (3 hydrogens bonded to a nitrogen) is my favorite but methane / methanol / ethanol are OK too (but would prefer to avoid carbon in the molecule). Also, if a synthetic fuel is created - this fuel can be transported and used for many things (cars, other transportation) in addition to grid-power storage. It should be added that biofuels have this advantage...but aren't actually a way to store the grid's ELECTRIC power.
3. Flow Batteries. Conventional batteries don't have enough capacity vs. cost. Flow batteries size the battery to the POWER RATE needed, then you store as much of the reagents as you need to provide the total ENERGY STORAGE you need. Redflow (mentioned by someone else) is one, but there are others. General Atomics is studying a lead-acid flow battery that uses conventional / low cost chemicals and has no semi-permeable membrane (the power-limiting and most "finicky" part of most flow batteries).
Flywheel energy storage has been tried and proven not cost-effective (eg: Beacon Power), Conventional batteries and also distributed EV batteries are not likely to be practical.
The opposite side of this is manipulating the demand side. Some utilities are now pushing 'smart' meters and appliances that will give the utility the option of reducing your consumption at peak load times. That may influence some customers to install small at-home back-up systems. Right now the savings are not enough for me to give the utility control over my appliances. And I don't think a UPS can be had for the saving offered either. Plus there would be the difficulty of how to wire / control such a system.
Lux and Pike don'tknow what they are talking about. Both write papers that most always are wrong. Same for the EIA, IEA which past data is good but can't predict worth a dam ;^P
Take this one. They left out the recent tech that makes GS at least by utilities moot. It's NG turbine Cogen units that can throttle to 50% eff reming the need for storage.
Next RE doesn't need storage on uility level because RE mostly happens when needed, solar or on call, hydro, CSP, biomass. The only truly intermitent RE is wind and only big wind far away has that.
So just where is this great demand other than armchair experts dreaming it up?
We already have batteries for under $1/kwhr and have for more than 10 yrs yet they haven't been deployed. Why?
Fact is no market because the utilities already handle massively changing demand and have for over 100 yrs and that in reality is the same as intermitant supply, both handled the same way rather easily.
The only extra cost was running enough equipment to handle expected surges but the changed with throttlable Gas turbines and retrofit kits for older ones.
That plus demand like controlling when EV charger charge, etc solves 99.9% of grid needs. Fact is you can't build enough capacity to make a real difference due to volume of power used.
Get a sub to Pennenergy newsletters of your choice is the actual utility experts info and utility people running the plants instead of those who talk about things they no little.
The Lux report does indeed reinforce the need for large-scale energy storage solutions as renewable energy deployments continue. Other researchers (Pike, Frost and Sullivan, EPRI) have reported much the same thing. The only two proven viable (efficient and economic) methods thus far for storing hundreds of MW for hours - pumped hydro and compressed air energy storage, or CAES - have not seen wider implementation due to geological, environmental and capital constraints. Indeed, no CAES system has been built for more than 20 years (and there are only two in the world).
A new method for compressing large volumes of air to store energy at low cost exists and is being developed by several companies, my own included. Isothermal CAES compresses air but does so in a way that maintains near-constant temperature, thus avoiding the inefficiencies of conventional CAES. ICAES also allows site-anywhere storage using pipes, rather than relying on caverns. Even better, because it retains most of the heat produced during compression, ICAES does not need a natural gas turbine to reheat the air during decompression, thus avoiding emissions and fossil fuel consumption. It's a truly sustainable solution that will be deployed on a MW scale in 2013.
One note about Lux's reference to flywheels: they are not considered a bulk storage technology and are not able to provide MWs for hours as is needed for diurnal renewable energy storage. Flywheels are fast-responding devices that are very good at delivering short bursts of energy for minutes (and absorbing the same), in order to provide grid ancillary services like frequency regulation. This is considered a power application, where the demands to inject or absorb energy are instantaneous and durations relatively brief, but with many cycles each day. As renewable use expands and brings all of its intermittencies with it, short-duration fast-response storage systems will also be needed to smooth out the irregularities and maintain stability. But they will not compete with ICAES, large battery systems, or other emerging methods of providing bulk storage.
Full disclosure: I work for SustainX, one of the ICAES developers.
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