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Thu Feb 9, 2017, 11:23 AM

The Net Carbon Dioxide Penalty Associated With Large Scale Energy Storage Systems.

A paper published in the most recent issue of Environmental Science and Technology, the premier scientific journal on environmental science published by the American Chemical Society discusses the environmental cost of large scale energy storage systems, in particular, batteries.

The link to the paper is here: Emissions and Economics of Behind-the-Meter Electricity Storage (Environ. Sci. Technol., 2017, 51 (3), pp 1094–1101)

For many people - those without access to university library systems or subscriptions - the full text will be behind a firewall, but the abstract gives a decent summary of what's inside the full paper:

Here, we characterize the economic payoff and regional emission consequences of BTM storage without colocated generation under different tariff conditions, battery characteristics, and ownership scenarios using metered loads for several hundred commercial and industrial customers. Net emissions are calculated as increased system emissions from charging minus avoided emissions from discharging. Net CO2 emissions range from 75 to 270 kg/MWh of delivered energy depending on location and ownership perspective, though in New York, these emissions can be reduced with careful tariff design.

The nice graphic also accessible from the abstract alone, shows the broader case.

Some excerpts from the text of the full paper:

Stationary electrochemical (battery) storage has seen significant improvements in cost in the past decade and is a promising way to perform many electric-grid functions.1,2 Battery storage is being installed both on the utility side of the customer meter at the transmission and distribution level (“grid-scale”), and “behind-the-meter” (BTM) for individual facilities. Grid-scale storage can be used to delay infrastructure upgrades, perform wholesale market transactions including energy price arbitrage and frequency regulation, and absorb over generation by distributed generation resources, among other services. BTM batteries can reduce retail electricity costs by shifting the timing of utility purchases while also performing grid-scale services via aggregation or proper tariff structures. BTM storage is being adopted in areas that have high retail electricity prices and generous battery subsidies…

…Policy makers are now implementing rules and subsidies that encourage large scale deployments of electric storage. California has set a storage procurement target of 1.3GW by 20204 and provided an incentive of $1300/kW.5 New York City has an incentive of $2100/kW.6 At the federal level, FERC Order 7557 instructed grid operators to compensate fast-responding resources like storage for their speed and accuracy in frequency regulation markets. The emissions consequences of deploying a storage technology depends in part on how it is operated; in turn, the operating policies depend on who owns the storage. Previous research has focused on grid-scale storage. Investor owned grid-scale batteries will be operated to maximize profit from wholesale market transactions, resulting in homogeneous battery behavior across a grid region. A number of studies have shown that grid-scale storage will increase total power system emissions under the grid’s current fuel mix when operated for energy arbitrage,8−12 …

The text includes also a description of the limits owing to the physics of batteries:

...The simulated battery faces three main types of physical and market constraints.

1. Battery state of charge (SOC): Expressed as a fraction of total energy capacity, SOC is restricted to 20−100%, with a penalty function above 90%, to prevent increased degradation from high and low voltages. These restrictions are also found on electric vehicle batteries.28

2. Total capacity: The capacity used to charge and discharge the battery and held for ancillary services cannot be greater than the capacity of the battery.

3. Frequency regulation capacity: We assume that the frequency regulation signal is energy neutral (no net charging or discharging), similar to the dynamic regulation signal implemented in the PJM Interconnection(PJM).29 However, during any given time period, the battery will gain and lose charge as it follows the regulation signal. Therefore, we place a constraint on capacity used for frequency regulation to ensure Solicits are not violated. One year of regulation signal from PJM30 was used to estimate the amount of charging and discharging possible during a single period..

The paper conclusively makes what should be an obvious outcome, but somehow isn't. Large scale energy systems waste energy, and therefore, since the overwhelming majority of energy on this planet is provided by dangerous fossil fuels, increases emissions.

It is said that Albert Einstein once remarked that the laws of thermodynamics are the only laws of science that he thought would never be over turned.

The first law is the law of energy/mass conservation and can be stated as dU[sub]universe[/sub] = 0 where the energy, U, includes but is not limited to the energy associated with mass. If we ignore the energy trapped as mass (which is accessible only with nuclear reactions) this law is a simple statement of the fact that energy is conserved, it can never be lost although it can change form, notably, and most importantly to forms that cannot be converted to useful work, usually, in a practical sense, low grade heat.

The second law, the one that "efficiency will save us" types generally like to ignore, can be stated as dS > 0. This means that the entropy of the universe, disorder, which may be expressed mathematically as a number of states available to a system, is always increasing. This law states that any energy conversion from one form to another will lose exergy, the ability to convert it into useful work, almost always in the form of heat (although in practice this loss can be as radiation).

The third law, which is somewhat esoteric, and not really relevant to the environmental crisis before us is that dS -> 0 as T -> 0.

There is also a zeroth law, which is important in an environmental when one shuts down a coal plant or gas plant because the wind is blowing or the sun is shining for what may be a short period. This law states that any two systems experiencing a temperature gradient - different temperatures - will eventually reach the same temperature. One therefore needs to waste energy to restart the coal or gas (or diesel) plant if one has shut it down.

Many people assume that energy storage will somehow be an important cog in reducing carbon dioxide emissions, since they like to fantasize that someday, somehow, that so called "renewable energy," in particular, wind and solar energy will become significant forms of energy, even though they have never been a significant form of energy, are not a significant form of energy, and will never become a significant form of energy no matter how much money is thrown at them.

Nevertheless, as the internal costs - the costs paid for the manufacture, delivery and operation - of batteries fall, even as the external costs - the costs to the environment, human and ecosystem health, and the future are not falling at all, and are possibly, owing to the toxicological and resource depletion issues associated with their manufacture and use, are rising.

Large scale commercial battery systems are now known, even if their overall capacity is not really huge, and the materials required for their manufacture make them unsustainable over long periods of time.

The second law of thermodynamics dictates that the use of batteries will always waste energy. Most people can see this experimentally themselves when they feel a computer battery, or any kind of rechargeable battery, during the charging process. It always feels warm to the touch. This is waste heat, the energy, or more properly the exergy lost.

Consider a nuclear reactor. A nuclear reactor takes potential energy expressed as mass and converts it to heat. In a fission reactor, this heat is generated on an atomic/molecular scale by the very high speed of the fission products of uranium, neptunium, plutonium, americium or curium when an atom of one of these elements is split by a neutron. The nuclear energy which is potential energy associated with the fact that whichever of the aforementioned atoms will weigh slightly more than the sum of the fission products (and neutrons) released in the fission event is converted to thermal energy. A small fraction of the energy is carried away by neutrons which induce more fissions, or collide with reactor components or coolants to produce heat. Some of the energy is also released as radiation, and some of it is lost immediately as neutrinos, which do not react with matter in a way that makes the energy recoverable. (Neutrinos represent about 5% of the energy lost in a nuclear fission reactor). Now the energy is in the form of heat, and the heat is converted to mechanical energy by using it to boil a working fluid - almost always water - to drive a turbine as vapor. In order for this to happen, the opposite side of the turbine must always be cooler than the hot side; this conversion is the energy lost as heat in the cooling towers. In addition some of the heat will be lost to the materials of which the boiler is constructed, and other heat leaks, including the turbine housing, steam lines, etc. The turbine converts the mechanical energy to electrical energy by use of a generator. The armature of the generator loses small amounts of energy to friction with the air in which it moves, more is lost by eddy diffusion currents in the materials as well as electrical resistance and the slow (but real) degradation of the materials in the magnets. The electricity is then shipped - where energy is lost to resistance in the wires - and finally used in the system where it is required, a computer, a refrigerator, electric heaters, etc.

If however we choose to store the energy in a battery, we need to convert electrical energy to chemical energy, which is always an inefficient process which releases resistive heat. Now to the above changes to forms of energy we need to add two more, the conversion of electrical energy, including a shift of alternating current to direct current – itself an energy losing proposition – and the conversion of direct current to chemical energy (in the battery), the storage of this chemical energy which is subject to (generally small) losses owing to diffusive effects, and the reconversion of chemical energy to electrical energy as direct current, followed by conversion of the direct current (via an inverter) to alternating current to supply the grid, with transmission losses occurring on both sides, the charging and discharging of the battery.

If the power is used to charge an electric car, the situation is even worse.

In the nuclear case, no carbon dioxide penalty is observed, but for the standard grid electricity supplies in most of the world, France excepted, a carbon penalty for this profligate waste of energy is observed, since regrettably most of the world's energy systems do not rely on nuclear energy; the overwhelming bulk of the electricity generated on earth relies on burning fossil fuels.

Occasionally, after decades of failure, we still hear a lot of silly cheering about hydrogen “energy.” Hydrogen is not energy, since it does not occur in free form in the natural environment except in extremely dilute concentrations which are of no practical use. Hydrogen is just another energy storage system, subject to all the thermodynamic laws described above. The situation for hydrogen for a purely thermodynamic sense is even worse, although, truth be told, there are thermochemical (high temperature) water splitting processes that can improve the thermodynamics of hydrogen use somewhat, but no matter what, manufacturing hydrogen gas will always waste energy.

The point of the paper, which should be obvious to anyone with a knowledge of the physical sciences is that energy storage, wastes energy, and therefore increases emissions.

The fantasy that underlies the opposite impression is the fantasy that solar and wind energy will someday become significant and even dominant forms of energy. This has not happened. It is not happening. It will not happen. The massive investment world wide in so called "renewable energy" has not lead to a decrease in the use of fossil fuels. The reverse is true. We are now burning more fossil fuels than at any point in history, and the accelerating rate of the accumulation of the dangerous fossil fuel waste in the earth's favorite waste dump, its atmosphere, demonstrates this fact conclusively and irrefutably.

The reality is that careful examination of scientific principles can explode popular myths, and a little science can help if the goal is really to save the environment, as opposed to wallowing in dogma.

Have a nice day today.

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