Energy Storage is the Holy Grail for Smart Grid

Joao Batista Gomes | Dec 08, 2011

Storage energy is critical to developing the full potential of Smart Grid, without this tool some promises about a SMART GRID may not be met. The development of this technology is not only important for Electric Cars, but for other areas of the Grid.

The ability to store energy to the grid is an important part of making the grid smarter, stored electricity can be used to provide the load following reserves necessary to balance and integrate variable renewable energy onto the grid. The market is shifting toward renewable sources of energy such as wind and solar. The most desirable situation for a commercial producer of electrical energy is to supply energy at a constant rate. The reality requires utilities to respond to rapid changes in demand, and to have a reserve to meet increases in demand.

There are lots of potential solutions, all have significant drawbacks, they are not portable, they require expensive infrastructure and added transmission, and they are inefficient for addressing short-term sags. The more realistic way to address the short-term sag problem is with batteries, capacitors or a combination of the two.

As we move toward a green energy future, local production that uses renewable sources will go a long way to relieve stress on the grid infrastructure. Energy storage has always been inconvenient, matter in the form of the ideal storage is energy generated from renewable that sources are used at the same time they are generated. New technologies as Nanotechnology, will surely bring a new impetus to this area.

Its four main segments are:

  • Electric Car: With only one Electric Car the consumer will double its residential consumption, imagine the power consumption of a family with the need to have two or more Electric Cars. The current infrastructure of transmission and distribution is not designed to withstand this excess of consumption. Then we have to build numerous filling stations similar to gas stations, as we currently have, or stations where we can exchange a discharged battery for other charges. The batteries could have the appearance of a rack with several slots you only need to swap the modules of the slots; this system could be used for electric cars and also for other applications. But for the consumer is taken to replace your current car the electric car, it needs to make sure that the flexibility of supply current is the same for electric vehicles.

  • Renewable Energy: Renewable Energy bring constraints on resource availability, that the current Grid were not designed to address. Addressing these constraints will require new efforts at coordination of resources and capabilities within the electric grid, both to mitigate difficulties and to maximize benefits, and built to provide energy from different sources for various loads through a single large interconnected infrastructure.

    The system requires active control, in real time, the resolution of Control in Space and Time is limited by extant technology and design philosophy.

    Intermittent, what we still do not know...

    How much advance warning can we get before rapid variations in Solar and Wind output, and how we can use this information effectively. What is the point of intermittency of renewable energy that can cancel the high penetration levels, locally and around the system? How quickly will vary from aggregate production for large and diverse collections of resources for Renewable Energy.

    Without energy storage will have to maintain an expensive infrastructure for the supply of energy -- fossil fuel -- on standby to maintain safety and reliability of the GRID. The intermittency of renewable energy is well known, although the techniques of predictability are improving every day.

  • Distributed Generation - How Do We Integrate: Time and space make up the two main factors in the connection and disconnection of the distributed power generation. The storage of energy at certain point of the GRID can give us the confidence necessary to handle this new source of energy generation. Balance Load and Generation Distributed, there is blend individual Micro Grid requirements with Grid and market support: It is still common to hear comments about the instability that we can add to the GRID with this new topology of Generation Distributed, but Energy Storage can bring the reliability necessary to supply energy.

  • Micro Grid: In many countries we have isolated populations -- like islands -- in many regions that already use this topology distribution, energy storage will give comfort and security of these people. The independence part of your DNA and your goal -- without even knowing it -- it will be like trying to mop up the ice, the Nordic Countries could serve as an example. Geography, Culture and Renewable Energy characteristics are crucial for their development and maturation.

    New economic activities will be developed in these regions with the assurance of continuous supply of energy that will bring the energy storage. Whoever wants to control the Micro Grids may lose the battle and war. Its how to control the Internet, it is impossible! There are no rules, only exceptions are when we speak of Micro Grids, the regulatory standards have to be kept to a minimum. If not this way, it may not be advantageous for those who sell and the buyer. Do not believe the Micro Grids will connect the network of Utilities, their development and survival is in its independence.

    Faced with such diversity and versatility, it is virtually impossible to map any topology distribution under the Micro Grid typical in terms of energy sources or settings, each one tended to have a different topology, especially remote systems. Barriers to implementation, in commercial, industrial or residential, do not rely so much on the topologies themselves, but on the commercial aspects of operations management. Micro Grids could create a black market in energy, and worse still, their power sources will not necessarily clean.

Energy Storage has always been inconvenient, no matter the form of storage the ideal is that energy generated from renewable sources are used at the same time they are generated.

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I'd add demand management or demand flexibility to this equation. There's quite a bit electricity use (esp. related to HVAC) that isn't needed at a precise second in time. It can also make use of opportunistic times when additional power is available. This all needs to be coordinated, of course, with some kind of real-time pricing mechanism (see Len Gould's IMEUC) but this would still all be less expensive than actual energy storage.

A related technology would be how some modern HVAC systems make ice at night (when electricity is cheap) to cool a building during the day. Again, no fancy batteries, etc. are needed. There is enough of this type of demand out there to absorb perhaps 15% of grid demand. That is, 15% or so of the grid could come from "unreliable" renewable sources. After that, you need to get fancier with Plug-In grid connects, etc. But we are nowhere close to that kind of penetration at this point.

Energy storage will have a key role in the distribution of energy in all segments, it adds flexibility in the use of energy, especially in the use of renewable energies.

Its development is still in its early stages, but in the future its use will be decisive for a stable and reliable grid.

All the “solutions" to the energy storage problem solve a problem over a time period of a few hours. Even hydro-pumped storage, the best of all technologies, can generate a full output for only 6 to 10 hours.

But with renewable energy we have to face up to the fact that it is sometimes calm for several days or weeks, that the sun shines most in the summer and does not shine all at nighttime. So, to be viable and large-scale, we need a technology that will store very large amounts of power for weeks or months. No such technology exists or is even on the horizon.

If you try to do with hydro pumped storage you need a site with 700 m or so of different and two seriously enormous lakes. Very few sites exist in the world. On top of that, you then have a problem with evaporation so the amount of make-up water needed will be very large indeed. And then you have the problem of the cycle efficiency at 75%, so there are high energy losses.

For this reason alone, there is no prospect that intermittent renewable energy technologies will ever provide a significant amount of electricity..

In the late 1800s hydro-power from a small pond could run 3 mills with separate work crews. Each had to plan the 30-minute event to its best advantage. My grandfather owned the saw-mill. It was third in position. Will the public and industry get used to this type of lifestyle all over again?

I think the future power supply will be somewhat constant and very much more localized. When there is more power than required for human activity, the excess load could make ice.......or hydrogen........or hot-water (swimming pool)......or charge the batteries in our cars.............or the batteries that power the city lights ......... or the coffee maker............and????

BTW.......why can't elevators generate power on the way down?

Energy storage may be the holy grail of the smart grid but how holy is largely dependent upon "Location." Pumped hydro locations are scarce especially in more populated areas and the require a lot of surface land. Aquifer Compressed Air Storage is essentially natural underground pumped hydro. Water is driven to a higher head (pressure instead of elevation). When the reservoir has a high permeability the compressed water in a halo around the air bubble rushes back in to force the air back out. In a good reservoir a relatively constant discharge pressure of the air can result. Aquifer reservoirs structures can sometimes be seen by the surface strata exposures but usually require subsurface exploration techniques. The efficiency of an aquifer CAES can be about equivalent to a pumped hydro but with the costs considerably less. The size can be up to a few thousand Mw and provide ancillary serviices.

Bryan, Alas, I agree with your conclusion. (that would maybe be 70 meters or so.)

Dennis, they do. The weights go down as the elevator goes up. The motor only supplies the difference. If you could get one guy on a shift to walk up then the guys coming down could hoist all but that one going up. The only supply of energy woud be to the walkup guy's diet..

Gravity Power offers pumped storage hydro performance that does not require an elevation difference, is low cost projected to be under $1000/kW for 1200 MW with 4 hours of storage that can be installed on less than three acres and does not consume water. The problem is ... there is no running project. The physics is straight forward and unchallenged. This technology offers more promise to the storage solution than anything else available.

Thomas Mason, your post males no sense to me. Could you explain?

Page 54 of my compilation of energy inventions suppression cases (see or has this:

"Most of the high-end conventional automobile batteries of the lead-acid variety operate at an energy density rate of between 20-25 watt-hours per kilogram. The best NASA sodium-hydride batteries operate at 48-50 watt hours per kilogram. The energy accumulator devices which have been tested at the Idaho National Electronic Laboratories have demonstrated energy densities of between 850 and 1050 watt-hours per kilogram.

What does this mean in practical terms? It means, for one thing, that for the first time in the history of science an energy storage device has been created with an energy density which is greater than gasoline or any other refined fossil fuel. It means that devices which rely on these energy storage technologies can theoretically be designed to store and deliver clean electrical power at higher rates of efficiency than any fossil fuel ever discovered.

(End of excerpt)

Could these IPMS-developed energy storage/battery devices achieve the Holy Grail of the Smart Grid to a useful degree?

Gary Vesperman

Well I think this article really states the obvious. The inability to store electrical energy on a large scale is the very reason why we have a grid system in the first place. The problem is that after over one hundred years or more the best we can come up with is the lead acid battery. We do indeed know how to store electricity on a SMALL scale. Every portable device we use today has that technology. The problem is storing it on a LARGE scale. Gary posts some interesting data but it is not the number of watt hours per Kg that matters (except for mobile applications) it is the total number of MEGAWATT Hours that can be stored.
Most people, including some that post here have little comprehension of the size of grid systems in developed world or its ability to deliver exactly the right amount to meet the demand every second of every day.
Sure energy storage is the holy grail - of course it is - but like the chalice it is very elusive and storage technologies are a long long way from making any meaningful contribution. I do assure you that if there was ANY promising device or technology out there the grid companies would be all over it. The costs savings to them would be enormous as it would enable all generators to be operated at base load and of course there would be no requirement for peaking generation of any sort.
The number of generating plants required could probably be cut in half.
So while I never say never the likelihood of such storage being developed and available to the grid on a large scale in the next thirty years is small.

Like Don I do not comprehend what Thomas Mason is talking about either. Pumped storage is using gravity to provide the potential energy to convert into kinetic energy in the turbine. Instead of the Sun lifting the water up into the air to form clouds that produce rain electric pumps push the water against gravity using off peak power so that the peaks can be readily met simply by opening a valve in a pipe. No idea what other methods there are that use gravity.

Gary, When I see such words as “Most of the high-end conventional automobile batteries of the lead-acid variety operate at an energy density rate of between 20-25 watt-hours per kilogram” I suspect a charlatan. Car batteries are not Gucci handbags. There are no “high end “lead acid batteries. I must ignore what you say.

If you want knowlegible people to pay attention don’t’ insult them.

Jim Beyer-------" I'd add demand management or demand flexibility to this equation. "------

That can be as simple as a $5 outlet timer switch. Load your washing machine or dishwasher to go, set the switch to come on will you are in bed asleep.

oppps----WHILE you are in bed asleep

Malcolm R.-------" We do indeed know how to store electricity on a SMALL scale. "----

Power storage, not electricity storage.

A 20 MW CSP plant has opened in Spain that generates 20 MW 24/7. It uses molten salt technology to store up to 15 hours of thermal energy that allows the generation of solar sourced electricity 24/7.

Thomas Mason is referring to Gravity Power's approach to storage, building a couple of huge underground shafts as a sort of vertical reservoir for pumped storage. A promising concept.

In reply to William Lang's note on aquifer-based compressed air energy storage, the recently cancelled Iowa Stored Energy Project is an example of how difficult siting one of these actually is. After looking at 21 different sites, they thought they'd found one with the right characteristics and plans were made to develop it. Then it was concluded that this site, too, wouldn't work. I do hope that one aquifer-based CAES project gets developed to finally prove the concept. In the meantime, the emphasis will continue to be on salt-based caverns.

Thomas Mason is speaking of a pumped storage system that uses a large piston-and-cylinder arrangement in lieu of a lake on a mountain. His system does indeed pump against gravity to move a weighted piston over some amount of elevation difference, working just like a counter-weighted elevator. I do see some obvious advantages over traditional pumped storage such as lower land use, lower total volume of water, lower losses by evaporation and minimal environmental impacts, plus the ability to build in many more geographical areas.

One key difference however is the sustainability at full power of only 4 hours. In comparison, the relatively modern Raccoon Mountain unit at 1600 MW capacity can carry full output for some 22 hours, yielding 35,200 MW-hours of electricity (of course at the expense of 44,800 MW-hrs to run the pumps for a complete refill). In order to produce 35,200 MW-hours of electricity in a one-day timeframe, the weighted-piston system would require at least 6 additional 1200 MW units, thereby boosting the cost substantially for rough parity in output. The benefits of the piston system may still outweigh pumped storage, but I would just like to see a more thorough comparison. For comparison purposes, at Raccoon Mountain the losses due to friction alone over 20% and the size of the reservoir is over 100,000 acre-feet of water. If the piston system as suggested by Mr. Mason is much smaller these numbers should not be hard to beat.

For further comparison I would like to hear from battery advocates what the % losses are for 1600 MW in battery power over a similar time period (assuming 22-hour sustainability, or the maximum hours of sustainability possible). Also would like to know the cost and physical size of a 1600-MW / 35,200 MW-hr battery system and the tons of active material, e.g., lead-acid, NI-Cd, or other chemicals that it would take to produce one.

Fred the movement of electrons is power. You have to store the electrons first in order to allow them to flow out later.

A few posts here lead me to the conclusion that your solutions are simplistic and not credible. Of course one can shift the electrical demand on your dishwasher to the evening when you are asleep and the grid is under-utilized but all that does is move the minor amount of electricity required to run the dishwasher pump and ignores the really big energy use which is the hot water. If you heat your water by gas as many people do there is no electrical savings at all and I suggest that you would even have trouble making back the 5 bucks you spent on the timer. A better solution is just wash your dishes by hand then you can sell the dishwasher and use the funds to invest in Uranium stocks. :)


Fred, Interesting concept the 20 MW molten salt plant. This sort of investment likely explains why Spain is going broke. I would add that 20 Megawatts is a very very small plant. The standby generators at most nuclear plants are bigger than that. Twenty MW is a drop in the bucket. You would need to build 60 of these plants to replace just one PWR unit.

Matthew and Kent,

Thanks for the explanation of that. This is a new one. Lifting a weight by water pressure. Bit like a giant water piston. It is a very similar idea to the gasometers that I was used to seeing as a boy in London. Gas would be pumped into these storage devices overnight (coal gas at that time) and slowly released during the day to maintain system pressure. I have a feeling that the losses would be substantial but I can see one major advantage that most of the system could be placed underground and is independent of siting requirements which restrict the availability of pumped storage schemes.

Combined with base load nuclear this is one of the more sensible ideas I have seen. These could be built just about anywhere. In fact they could easily be constructed right at the nuclear sites. You would not need peaking generators at all. One idea would be to construct them in lakes or the sea. At off peak times water from the lake or sea is pumped into the cylinder and during peak times released back into the sea or lake through a generator. The piston weight could use depleted uranium since the potential energy is mgh where m is the mass of the piston, g is gravitational force and h is height. The larger the mass the greater the potential energy.

Kent, I don't think only having a 4 hour discharge time is a problem since peak periods do not last all that long and several could be staggered to meet the demand at peak times.

Good thinking whoever thought of that and one of the better ideas I have seen.



Malcom, I just put the Raccoon Mountain numbers out there for comparison in terms of size. It would seem that the smaller closed system of the gravity-piston system would have significantly less percentage of head loss if for no other reason than shorter pipes. Your idea of minimizing height by using maximum weight as in depleted uranium would also mean either shallower holes in the ground for channeling the water or a longer “hang time” for the weights, perhaps exceeding the 4 hours now rated. For use strictly as peakers I agree that 4 hours is plenty, but if stretched a bit longer they may be able to take up more of the daytime cyclic loads and reduce fossil burning even more.

The biggest contributor to peak load is air conditioning. Over 40% of the peak can be contributed to air conditioning. The HVAC design industry can get more efficient, buildings envelops can get more efficient but we are at the point were huge investments provide little return. Today's typical air conditioning systems are designed like big SUV's when a commuter vehicle will work.

Computer energy modeling and life cycle modeling leave a lot to be desired. The actual building energy consumption rarely coincides with the computer model. The relative differences might be helpful and provide clues to how an HVAC design will react with the building envelope and operation. Designs have safety factor capacity. Just in case its hot for a few days in a row, just in case the building is not built as modeled, just in case the building is used differently than the owner described. If the safety factor is 20% more cooling capacity, the ancillary equipment must also be larger increasing connected load. This safety factor equipment is an investment that is rarely used but must be purchased. Additionally these models cannot predict future real time energy prices or potential demand response program revenue.

Look at your large cities with all of these existing buildings. Almost all of existing stock have over-sized inefficient cooling systems. When it comes time to replace these systems, hybrid cooling systems with energy storage can lower peak connected load reducing summer demand while creating a nighttime load for renewable energy, like wind. The wind blows harder at night in West Texas for example. Let's capture it to relieve peak demand and fill in gaps when solar panels are not a peak output because of time of day or clouds.

It seems like we all want these huge storage systems when distributed thermal energy storage, which is affordable and reliable, can help now. How do you eat an elephant? One bit at a time. How do you make renewable energy viable and reduce peak demand? One building at a time!

No special regulation or special site is needed. People are using ice storage today. Check it out.

Paul V. says "No special regulation or special site is needed. People are using ice storage today." -- I would rephrase that to "No special regulation or special site is needed. A very few persons are using ice storage today." To get to useful numbers, a harsh real-time retail electricity market will be needed.

Malcom There actually is a new player in the storage game. Massive concrete domes are eminently suited for storing energy where vacuum is the storage medium. Operating in reverse from CAES potential energy is accumulated as air is displaced from the containment structure. A dome estimated to cost $3.1 million is calculated to store about 1500 kilowatt-hours. Too costly for general grid power storage (mass production could lower cost) this product could find a market now with high added value applications such as integration with wind turbines. Stay tuned.

Malcom R-----" Fred the movement of electrons is power. You have to store the electrons first in order to allow them to flow out later."-------

Have your never heard of a generator? Rotating wires in a magnetic field generate an electrical flow----that is why it is called a generator.

Molten phase change salts store solar thermal energy at 875*F-1,000*F---which then is used to power steam turbines to drive the electrical generators.

There is no storing of electrons involved. It works the same way as any combustion heat power plant works----except that the heat is solar, not from burning carbon.

-------" Of course one can shift the electrical demand on your dishwasher to the evening when you are asleep and the grid is under-utilized but all that does is move the minor amount of electricity required to run the dishwasher pump and ignores the really big energy use which is the hot water."-------

Any natural gas power that is used does not come from the electrical grid. It has no bearing on the subject of the discussion---electrical grid peak load and power storage. The power contained in the natural gas that might be used is in the form of chemical bonds----it is already stored energy.

-------" A few posts here lead me to the conclusion that your solutions are simplistic and not credible."------

That statement leads me to the conclusion that you are an idiot.

The simplest solution to any problem is always the best solution.


As a 25 year Utility worker, I know that the USA runs on cheap reliable energy.
People also need to work. A project that combines both is the creation of 3, 20 foot diameter nominally 600 mile long tunnels running from Mississippi to Arizona. These tunnels would have state of the art high efficiency thermal cycle generating stations built at roughly 50 mile intervals. Power to pump the water westward would come from the normal plant cooling water pump operation, huge pumps that normally consume only about 1% of plant power output. The water traveling westward in the tunnels would provide for the plant steam-cycle cooling needs. The 50 mile intervals between stations provide a cool-down radiator between generating stations. So basically all power to move the water westward would come from the powerplant circulating water pumps, a normally operated piece of equipment. No extra pumping costs, and no water lost to evaporation as it is always enclosed within a pipe.

The Bureau of Reclamation estimated a tunnel project in California for reclamation of the Salton Sea. They estimated 10 Billion for a pair of 15 foot tunnels 100 miles in length. Extrapolating, that would be 60 billion for them to extend 600 miles, and doubling that to 120 Billion would probably get you near the price of a 3 tunnel system. The transport/cooling water tunnels would be a government sponsored multi-state public works project. Powerplant sites would be leased to industry, who would fund the individual powerplant construction and pumping costs.

Water would be pumped westward from the Mississippi to the western states; always a popular idea to create a new river in the West. Local aquafers such as the Ogalala could be allowed to recharge if alternative water was available for irrigation.

Excavated rock/dirt would be used to add to the Mississippi levee system and/or rebuild shoreline. Rail inside the tunnels during the construction phase could be used to this end.

All of the materials, equipment and labor would be sourced from within the USA. the money spent would RECIRCULATE within the US economy at the consumer/worker/homeowner level. This is supposed to be good for the middle class. Sales of concrete, steel etc. should give the U.S. based producers a shot in the arm too.

The tunnel right of way would give you a perfect opportunity to create a southern High Voltage DV transmission line (HVDC) between the West and South-east, enhancing grid stability. It is also an opportunity to wean power producers away from ageing infrastructure and old low efficiency powerplants.

There are ample low-head hydro opportunities along any possible route. It doesn't take a supergenius to figure out that off-peak renewable energies can be stored in such a project as pumped storage. Due to the size of such an endeavor, there would be considerable storage capacity available. If a low-line-loss HVDC grid-tie line were constructed as well, the pumped-storage locations would not have to be immediately adjacent to the tunnel project.

There are more possible angles to such a project, but that is the gist of it. The USA built the Panama canal nearly 150 years ago with black powder, sweat steamshovels and mules. This idea is intended to revitalize OUR electrical and water infrastructure, not some foreign nations. $120 Billion is chump change compared to what we lost in Iraq, Afghanistan, etc. and about 1/10 of what was gleefully handed over to financial corporations in 2008. Let's spend a little coin on helping the MIDDLE and LOWER CLASSES instead of entirely subsidizing the wealthy for a change. Let's actually HELP the industrial infrastructure of the U.S.A. instead of killing it off slowly with "smart meters". The last time I checked, my electric power didn't originate at my meter.

Mitch. I have no problem with the concept of a $120 billion public works project to assist economic recovery, and perhaps your favourite may even make sense, but I find it almost impossible to imagine, in the present US political climate, getting agreement from people in Florida, New York or Oregon to contribute financially to such as you propose.

The first step is to re-organize governemt to eliminate factionalism (party politics) by eliminating representatives. A straight-forward $90 billion investment in putting 100 mbps fiber-optic communication into every citizens residence, then hiring 1/2% of the population to moderate debates and maintain the system, gets you a GENUINE democracy instead of this corrupt representative oligarchy. Then one can start planning.