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The Electron Economy Part III: The Challenge of Mobile Energy Storage April 30, 2007

Posted by Michael Hoexter in Green Transport, Renewable Energy, Sustainable Thinking.
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In my previous two posts, I outlined Ulf Bossel’s Electron Economy concept and the importance of the electric grid as an energy transmission medium for now and the foreseeable future. If we are serious about reducing our carbon emissions, an electron economy, an economy in which most powered devices use electricity, is the only feasible alternative for the next several decades. Cheap, high-capacity, accessible storage of electrical energy has been one of the challenges in the development of the electron economy and again represents a turning point in growing a clean-energy economy in the 21st century. Energy storage in a wide variety of sizes and capacities allows for the convenience of being able to tap into an energy source on demand in any situation or physical location.

Energy storage can be divided into two categories: mobile and stationary storage. In the mobile storage category, moving more of our energy needs into electric-powered devices means finding more ways to use electricity when not connected to the grid or at least having to deal with an electric cord or active connection to the grid. In the stationary storage area, finding economical ways to store electric energy on a mass scale to power the grid or off-grid facilities when the supply of renewable energy dips below demand is also another area of development for a greener economy. I will deal with stationary storage challenges in a future post.

Energy storage or assumptions about energy storage influence decisions people make about which type of energy delivery they prefer, even if it is not often discussed in these terms. Currently, the electron economy is in partial competition for public, political, and investor attention with three other energy delivery systems that we can call the fossil fuel economy, the hydrogen economy, and the biofuel economy. For environmental reasons, the fossil fuel economy is not desirable but from every other perspective it is the one to beat, especially in the area of portable energy storage. Fossil fuels, in particular petroleum derivatives, have a high energy content per unit weight (called “energy density”), have been fairly plentiful, stored as they are underneath the ground, and we have already built a huge industrial and transport infrastructure around them. There are also reserves of petroleum, natural gas, and coal that can be more or less measured, so we can project their presence or absence into the future and can therefore make business or other plans based on them.

Two hopefully greener alternatives, the hydrogen and biofuel economies, are modeled on the fossil fuel economy with regard to the potential for both stationary and portable storage. Hydrogen and biofuels can potentially be stockpiled, though currently they are not produced cleanly in surplus amounts that could allow for their accumulation. Also they have high energy content per unit weight, though hydrogen needs to be compressed into a liquid to have a reasonable energy content per unit volume. They also are liquids or can be made into liquids, so can be dispensed and metered out in a way not unlike the fossil fuel economy.

Bottling Lightning

Electricity is an energy flow or alternatively a state of electrostatic charge, not a substance that can normally be contained or stored. Technically, electric current, the type of electricity that does work is the movement of electric charge along a gradient of electric potential, capitalizing on the characteristics of physical substances called conductors. Storing electricity means storing it as a physical and/or chemical potential that can be rapidly converted to an electric current on demand. The most important areas of energy storage for the growth of the electron economy are battery and ultracapacitor storage but many other forms of energy storage may come into play as technology advances and economic conditions favor carbon neutral solutions.


Batteries store electricity by utilizing the difference in electric potential between two chemical reactions, one at the positive electrode and the other at the negative electrode of each of the constituent cells that together make up the battery. The chemistry and design of batteries determines their energy and power per unit weight and volume. Battery performance continues to progress under pressure primarily from the demands of the portable electronics industry but, increasingly from hybrid electric and now electric-propulsion vehicles.

For portable electricity storage devices one of the greatest challenges is the energy content per unit weight/volume, technically “energy density.” In the early 20th century prior to the systematic exploitation of oil resources, battery electric vehicles and petroleum fueled vehicles were competing on equal footing, as electric vehicles were easier to use and quieter. The electric starter motor, ironically, helped hasten the demise of early battery electric vehicles as internal combustion engines could now be started without a hand crank. Once easily started and with a growing petroleum infrastructure, the higher energy density of petroleum-based fuels allowed drivers a much extended range and convenient fueling.

Though lousy for our environment when burned, petroleum products have enviable energy density per volume or weight: approximately 10,000 Watt-hours/liter or 12,000 Watt-hours/kilogram for gasoline/petrol and slightly higher for diesel. By contrast, lead acid batteries have about 1/250th the energy density, coming in at 40 Watt-hours/liter or 25 Watt-hours/kilogram. Internal combustion engines have about 1/3 to ¼ the energy efficiency of electric motors, but this only makes up some of the difference. Early electric vehicles or for that matter any portable electronic device, that depended on lead acid batteries, would need to make many compromises in terms of range, weight, and internal storage. The pioneering battery electric vehicle, the GM EV-1, in its first generation carried 1200 lbs of lead acid batteries for a range of 80-100 miles. By contrast a full 20-gallon tank of gas weighs approximately 150 lbs.

Despite their weight and bulk per unit energy, rechargeable batteries are quite an efficient means of storing electrical energy with an efficiency of more than 70% and as much as 90%, meaning that less than 30% and more like 20 or 15% of the energy is lost in the round trip.

Modern and Future Rechargeable Batteries

The lead acid battery continues to be useful but in the last 10 years there has been rapid progress in battery chemistry and technology. Most important has been the shift away from lead acid to first nickel metal hydride and now various lithium chemistries. All innovations in rechargeable batteries for powering transport are focusing on safety, reliability and battery life, meaning the number of cycles of charge-recharge a battery can endure before it needs to be overhauled or replaced. Different strategies for increasing the energy content, power and speed of recharge as well as safety, reliability and battery life are the following:

Lithium-ion Batteries

Most notable in the increased battery life and slim size of some of our favorite portable electronic devices (cell phones, Ipods) are the new generation of lithium-ion batteries, which offer high energy densities (130-200 Watt hours/kilogram). This means that lithium batteries contain as much as 5 times the energy per unit weight of a conventional lead acid battery.

For the purposes of the electron economy and transport applications, lithium ion batteries are being used in a new generation of battery electric vehicles, though the expense of these batteries is still high. The Tesla Roadster ($92K MSRP), the first all-electric production vehicle to exceed 200 miles per charge, uses 6,831 lithium ion batteries not unlike those found in a laptop. Tesla has built a complex power management system to ensure the safety and reliability of its battery pack. Various boutique electric car conversion outfits are creating lithium ion versions of their vehicles.

Innovations in the structure of lithium ion batteries promise to increase their reliability and usefulness for electric vehicle and transport applications. Altairnano’s Nanosafe battery uses nanostructured electrodes among other features to lengthen the life of the battery, increase battery safety, widen the operating temperature range, and, the company claims, to recharge within a few minutes. A123 Systems have also developed a nanostructured lithium ion battery with similar benefits.

Lithium Ion Polymer Batteries

Lithium Ion Polymer batteries can be physically shaped and bent according to the requirements of the application and also can have high energy density. While the physical form factor is less important for massive vehicles as opposed to portable electronic devices, lithium ion polymer batteries have been shown to have a high energy density. Electrovaya, a battery manufacturer largely for electronic goods, claims an energy density of 470 Wh/l and 330 Wh/kg for its SuperPolymer batteries.

Nickel-Metal Hydride Batteries

Though now “old news”, nickel metal hydride batteries (NiMH) are still a viable alternative for powering electric vehicles and hybrids. NiMH batteries were used in the final generation of the EV1, increasing the car’s range to 100-130 miles. NiMH batteries have a range of energy densities from 30-80 Watt-hours/kilogram so are more energy dense than conventional lead acid batteries but are considered to have favorable power and durability (many discharge/charge cycles) suitable for hybrid and battery electric vehicle applications. The current Toyota Prius parallel hybrid vehicle, uses an NiMH battery pack that is recharged by its gasoline engine and regenerative braking.

Lead Acid Innovations

Firefly Energy claims to be on a path to raise the energy density of lead acid batteries closer to the their theoretical limit at 170 Watt-hours per kilogram, a 4 fold increase over conventional lead acid batteries. Firefly is using a foam technology to revolutionize the structure of electrodes used in conventional lead acid batteries. Firefly claims their technology will lead to much higher energy and power densities and longer battery life. The continuing advantage for lead acid is that it is the most established rechargeable battery technology and potentially still the cheapest.

Quick-Charge and Energy Density in Battery-powered Transport

Many of the innovations in battery design are currently focused on quick charge, as this area seems to be more tractable to engineering solutions than extending the overall energy content of the battery through the discovery of new fundamental battery chemistries. Redesigning the physical structure of electrodes on a microscopic level, it seems, will lift some of the traditional limitations in energy flow, power and battery life that traditional electrode structures maintained.

If one can recharge a 60 kWh battery pack in 5-10 minutes with a suitably powerful electricity source, this would allow travelers to approach the convenience of fossil fuel powered vehicles that require a similar amount of time to refuel. And, if energy densities remain at or near the 200 Wh/kg level for a lithium ion battery pack, this leads to an approximate 200-250 miles per charge range for a moderately sized vehicle with an 800 to 1000 lb battery pack. While 1000 lbs is heavier than the 200 lbs that a full 20 gallon gas tank weighs, the much smaller size and weight of most electric motors over internal combustion engines will partly compensate for the difference in weight. So a long-distance trip in a purely battery powered vehicle with these newer quick charge batteries would mean approximately 3 hours driving with 10 minute breaks to recharge, as opposed to 6 hours with a similar break for most petroleum powered vehicles.

For the quick charge scenario to work, it would require the development of a new quick charge infrastructure to grow out of or alongside our current or a modernized electric grid. Quick charge would require high voltage fueling stations that can transfer as much as 80 kWh to a vehicle in the period of 5-10 minutes safely and reliably, whether at peak electric power usage times (middle of the day) or at night. This type of power is now available to certain industrial power customers and is therefore it is technically feasible to offer to a broader set of customers. Utilities or their partners would need to build roadside charge depots that would become the fueling stations of the 21st century. These charge stations would have to charge a premium over regular power rates to make it worth their while to build the charge infrastructure as well as perhaps, clean or cleaner electric generation facilities to supply the station with power, especially during the peak usage times.

Quick-charge may leap one hurdle but increases in energy density of batteries will eventually boost electric vehicle range between charges. There are unconfirmed announcements of future rechargeable batteries that use aluminum, which would have an energy density of as much as 1300 Wh/Kg. A theoretical 150 lb battery pack with these characteristics would yield ranges of easily over 500 miles per charge. This remains marketing hype until working prototypes can be demonstrated.


Ultracapacitors or supercapacitors, like regular capacitors, can store electricity as electrostatic charge because of the physical composition and design of the capacitor. Ultracapacitors have much higher charge and discharge rates than electrochemical batteries and are used most frequently now in hybrid electric vehicles to capture the energy of braking and recharge the batteries. Working in tandem with the vehicle’s batteries, ultracapacitors are now used in regenerative braking in hybrid-electric and fully electric vehicles, including the Toyota Prius and the Tesla Roadster.

Currently most existing ultracapacitors have per unit weight much less energy capacity than electrochemical batteries though they have greater power (rate of energy discharge). A number of research labs and at least one private company have been targeting a substantial increase in the energy density of ultracapacitors so they might replace batteries as the primary energy store of electric vehicles. Most prominent and well-funded among the ultracapacitor makers is the secretive Texas company EEStor, backed by the venture capital firm Kleiner Perkins, which claims to be able to deliver this year a Electrical Energy Storage Unit (EESU) that will weigh 100 lbs and store 15 kWh of energy, an energy density of approximately 340 Wh/Kg. The composition of their ultracapacitor is complex but is based on a ceramic made with barium titanate. EEStor is rumored to be making a 52 kWh EESU that would weigh 336 lbs. The EESU is rumored to be able to charge very rapidly, within a few minutes with a sufficiently powerful charging sourced if the cables and connections are cooled. The EESU is also rumored, under mass production conditions, to able to cost a fraction of what lithium ion batteries do, with EEStor claiming from 1/8 to ¼ the price.

EEStor has initially developed an exclusive relationship with ZENN Motor Company, a Toronto company that makes so-called neighborhood electric vehicles that are limited to speeds of 25mph/40kph. They will be delivering their 15 kWh EESU to ZENN later in 2007.

So much controversy and secrecy shrouds EEStor currently that it is difficult to evaluate its claims. If its claims can be substantiated and proven in real world applications, its EESU will revolutionize portable energy storage.

The potential of the EESU would also depend on a quick-charge infrastructure and economy similar to that outlined above under “Batteries”. The demand for high electric power to charge such a large capacity energy storage unit quickly would lead to high voltage/amperage outlets/charging stations along the roadways and in parking facilities as well as potentially at the level of individual households.


Flywheels can capture energy as angular momentum around a fixed axis. Modern flywheels can spin at speeds as high as 100,000 rpm depending on the strength of the materials used. Flywheels are very efficient at capturing energy but tend to bulky as compared to batteries due to the strong containment vessels required to protect people from the potential effects if the flywheel should break. Flywheels have been considered as energy storage devices in hybrid electric vehicles but as yet there are no working prototypes.

Biofuels as Storage in the Electron Economy

Of course biofuels store the sun’s energy and can be converted to electricity using a variety of fuel cells or be combusted to drive a steam turbine that generates electricity. Ulf Bossel in his outline of the electron economy highlights how biofuels will play a role in a largely electric-driven economy. It in fact their ability to be stockpiled as well as the relative low cost and current availability of the infrastructure (agriculture) that makes them attractive. They do however rely on the relatively inefficient use of land and the sun which wind and solar use much more effectively to capture energy. Algal and cellulosic biofuel production may make them more attractive but these are still unproven solutions to our new energy crisis.

Hydrogen as Storage in the Electron Economy

The much-vaunted Hydrogen Economy, in the ideal version at least, relies on renewably generated electricity to split water into hydrogen and oxygen gas, the hydrogen is stored, and, at the point of use, converted into electricity by a Proton Exchange Membrane (PEM) fuel cell. In the favored scenario for hydrogen as a clean energy solution, Hydrogen should be considered as an electric energy storage medium rather than an energy source in itself. Unfortunately the round trip efficiency of this cycle is approx. 25%, so 75% of the energy is lost as compared to approximately 20% losses in recharging and discharging a battery, a technology that is readily available to us. In a future of superabundant renewable energy, hydrogen may very well become the storage medium of choice but currently it falls short in important ways to batteries and, perhaps, ultracapacitors.

To move beyond our current crisis and to pay attention to the actual technological facts at hand, hydrogen is over-hyped and the much more workable solutions encapsulated in the Electron Economy idea need to be brought home to investors, government and consumers.

Future posts will highlight how innovations in energy storage will lead to new economic models and opportunities.



1. Tom Geist - May 1, 2007


Good article and good summary of the state of energy storage.

Here is some additional info on EEStor. Their patent number 7,033,406 describes the system and the fifteenth claim includes the text: “The method of claim 1 wherein the method provides a EESU which can be safely charged to 3500 V and store at least 52.22 kWh of electrical energy.”

I believe their plan is to charge the capacitor to 3500 V, which takes advantage of the voltage squared characteristic of capacitive storage (Energy = 1/2 * Capacitance * Voltage squared).
This has been thought of before and begs the question; do you really want a 3500V battery within a vehicle? Car manufacturers can’t even make the change from 12V to 42V let alone 3500 V! Moreover, the stored energy is not in a useful form and must be converted to a level compatible with other necessary equipment (the motor, braking system, air conditioning system). This conversion is expensive and inefficient. I haven’t run all the numbers, but experience makes me very skeptical. Remember also that not all of the 52 kWHr will be available. Typical conversion system are only practical down to 1/2 voltage, which already reduces the stored energy to two thirds of the original value (approx. 30 kWhr).

2. Michael - May 3, 2007

Thanks for your reply and the well-thought-out case you make, based on the patent application. I am not clear how exactly EEStor has designed their EESU, but if it is as you surmise, they will have had to solve a whole slew of very difficult engineering challenges to deliver what they claim. I am not able to evaluate the likelihood of their being able to solve all these issues but it seems like a stretch given that no one has built a ultracapacitor with anything remotely close to the energy density claimed by EEStor. I don’t want to count them out…I’d like to keep my “wait and see” attitude but the scenario you suggest seems very plausible.

3. Garry - May 4, 2007


Well presented post… and I like the framing of the electron economy. The advances in storage are exciting. But I disagree with the narrow framing of ‘electron’ energy as pure battery/capacitor and electrons- without including hydrogen as a critical piece.

These energy conversations can get ruined over emotion- that is not my intention.

I just believe there is a certain logic to H2’s role in this electron economy concept that is being prematurely discarded. I am pro-battery, pro-capacitor and love the advances there- but we cannot rule out the real potential of micro fuel cells and solid state H2 storage.

IMHO – Ulf’s framing is inaccurate when put up against current day breakthroughs in nanoscale designs of catalysts, membranes and high surface area materials that are re-writing the efficiencies to convert, capture and store hydrogen. Ulf, Romm and other leading skeptics paint hydrogen’s role in a world standing still… their assumption of the future is that H2 production/storage will never change. I believe we are only at the beginning of understanding the dynamics of electrons/hydrogen.

I do not see H2 as a cure all. I am not a true believer. I see it as a way to clean up hydrocarbons. And a reasonable way to deliver the highest amount of energy in portable packets – up against issues of safety, performance and market distribution channels.

Reinventing the energy industry is a marathon not a sprint. H2 skeptics are trying to win the sprint- and forgetting that we live in a hydrocarbon economy- with most electrons locked up in those chains.

Coal is expected to power 60% of global electricity production by 2030 and beyond. If we do nothing it will be combustion based conversion. The Electron battery vision does nothing to change this future. Bringing hydrogen (as an electron energy source) into the marketplace equation gives support to gasification systems that can leverage electrochemical (not combustion) conversion. Batteries – regardless of incremental improvements- do not change the way we convert hydrocarbons.

I keep close tabs on latest stage developments at my blog— http://www.garrygolden.net
(see ‘Research Notes’) The pace of change in materials science is healthy – and I am confident that we will soon exit the Hype Cycles ‘trough of disillusionment’ for hydrogen fuel cells. I am patient. And believe there are real market drivers for hydrocarbon incumbents to embrace an electron world with hydrogen as the primary energy carrier.

Imagine if someone would have said – you cannot fly a metal plane with 200 passengers b/c the propellers would have to be too big. They cannot imagine a jet engine. Or if an ‘expert’ in the 1950s said that computers wouldn’t be affordable b/c the vacuum transistors were too expensive and fragile. Not seeing the disruption of silicon chips.

Hydrogen’s disruptive enablers are being built today. H-clusters are being mapped, modeled and reproduced. So I cannot buy into the misleading statements that ‘it’s too hard to produce/convert’ or ‘too difficult to store’. And as much as I love the framing of the ‘Electron Economy’ – to disregard H2’s role in a hydrocarbon economy falls short.

So – all love here. No flaming! I really enjoy your insights! Just trying to challenge the assumptions about the future and the role of hydrogen in this vision!!

Best, Garry
Blog ‘Dark enough to see the stars’

4. Michael - May 6, 2007

Thank you for your thoughtful reply and praise. I also take to heart your request for a civil exchange about this issue that has become emotional for some justifiable and some less than justifiable reasons.

You have in the way you have presented your argument, reversed the current power and influence of the advocates of hydrogen storage and the advocates of the electron economy (i.e. using electricity directly). For a number of reasons, hydrogen advocates have gained a role at the table in discussion of sustainable energy solutions for transport that far outweighs the sustainable potential of hydrogen, at least in the next decade or so. See, for instance, Tesla CEO Martin Eberhard’s recent comments on his testimony before the Senate, where a hydrogen advocate from Shell was given the privileged last place to spread more pro-hydrogen hype. The New York Times, also just spent considerable space in a 3-part article about hydrogen that nowhere mentions the main arguments against hydrogen, therefore functioning, temporarily, as an organ of hydrogen hype.

Your patience with hydrogen, while a laudable personal characteristic in certain contexts, does not serve you well in this matter as we are being told by the IPCC among others that action NOW on climate change would be most desirable and most effective. Hydrogen is still a Maybe and a very costly one at that in both financial and energy terms. Batteries and ultracapacitors are out there right now doing the work for countless vehicles on the road in a way that even now is economically sustainable and can be scaled up with sufficient supply, market demand and factoring in the true costs of carbon emissions (carbon tax, cap and trade etc.).

As it did at California Air Resources Board a few years ago, when they killed the ZEV mandate, hydrogen advocacy too often functions as a distraction from what can be done now to mitigate the environmental damage of fossil fuel use. Historically, hydrogen advocacy encourages complacency and a “wait and see” attitude, where immediate action, guided by reason and science, is possible and desirable. Battery electric and other direct electric transport options are here right now or can be made available within the next 5 years. Hydrogen is a ways off and very expensive in terms of money and energy.

Like so many hydrogen advocates, you have, for reasons that are beyond my understanding, taken hydrogen to be an end in itself, something that is worth waiting for no matter what. It seems in places that you have lost sight of the purpose of our attempts to use hydrogen, among other technologies, to create a carbon-neutral, clean form of energy delivery. At the level of the vehicle, sure, you have a tank of hydrogen, a fuel cell or hydrogen combustion engine and you get water out of the tailpipe or drip-pipe as the case may be. But the efficiency of creating the fuel, the H2 or hydride energy storage, whether it be 25% or, as advocates claim 40% efficient, is still, at most, half as efficient as a rechargeable battery in storing electric energy. Do we have double or triple the amount of the renewable clean energy to use for the sake of using a hydrogen fueling/storage system? Now or in the next 10 years, I don’t think so. You or other hydrogen advocates, to my knowledge, have not yet come up with a conceptual model let alone a prototype that exceeds these efficiency numbers.

You also mentioned that hydrogen has a crucial role to play in using fossil fuels more wisely in the next few decades. Again, the use of non-PEM fuel cells (molten carbonate, etc.) or combined cycle power plants to directly convert hydrocarbons into electricity at around 50-70% efficiency is preferable to 25-40% efficiency fuel cycle with hydrogen extracted from the hydrocarbons. The generation of hydrogen from hydrocarbons, as you know, emits carbon, as do the more efficient alternatives, so why not go for the more efficient route?

Finally, you seem to be making a plea for patience as a virtue in the area of scientific and technological progress, that we need to usher in the “disruptive technology”. The thing about disruptive technologies is that they emerge and disrupt…they don’t really require patience on the part of bystanders. I would take a similar attitude to the makers of ultra-high energy density aluminum batteries; their technology is just too speculative right now for me to hold off on advocating the use of lower-energy density batteries. I am all for patience but a bird in the hand (batteries and ultracaps plus renewable electricity), seems to be far more valuable at this point in time than two in the bush (hydrogen in some form from 2-3 times as much renewable electricity). Building out the electron economy eventually may provide the basis for a hydrogen economy but, as I have said, and the Stuart Island folk (who have created a functioning hydrogen storage system for their solar arrays) concur, the hydrogen economy is not Task A or B.

Best regards,


5. Duquenne Leon - May 7, 2007

It looks to me so long we are not able to store the electric power from solar panel, we are not able to solve CO2 accumulation and weather changing
In nuclear reaction lost of mass give energy
I am not qualified but is it not thinkable to inverse the processus
In nanotechnology we work on atomic size can we not dream to increase the mass of some molecule?
We can so store energy !!!!

6. Idetrorce - December 15, 2007

very interesting, but I don’t agree with you

7. Business » The Electron Economy Part III: The Challenge of Mobile Energy Storage … - March 11, 2008

[…] Research more about this from here […]

8. John Carolin - November 12, 2008


You are correct E=mc2 is reversible. Particle accelerators convert energy to mass, but probably aren’t practical storage devices.


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