By Rud Istvan
Got to thinking about WUWT 2.0, and some of the fact ammo climate skeptics here might need if/when Kerry becomes Biden’s climate guru. So here is a bit more WUWT fact ammo for the maybe coming renewed climate war.
One of the BIG problems with renewables is their intermittency. Another is their lack of grid inertia. (See my recent guest post on Grid Stability for details.) Innumerates like Kerry persistently claim both issues can be/will eventually be overcome by more grid interconnectivity or by better grid battery storage. Those hopes/beliefs are almost certainly wrong. My last post, referenced above, challenged the interconnectivity belief. This hopefully not too technical complementary post explains why their rechargeable grid battery hope is also wrong. It does so in a simplified yet easily researchable way. It provides all the key words for anyone seeking deeper grid battery storage understanding.
There are basically only three non-kinetic electrical storage mechanisms: electrochemical, pseudocapacitive, and capacitive. We deliberately exclude indirectly kinetic pumped hydro, for which there are two big expansion problems: insufficient remaining suitable terrain, and California having rejected it, period.
Electrochemical batteries involve some chemical species change (lead acid aka PbA is discussed following, chemically oversimplifying, the lead anode goes to lead sulfate then back to lead thanks to the sulfuric acid electrolyte). The general nature of such reactions is that they are faradic (involving electron exchanges, named in honor of Michael Faraday, also honored by the Farad of capacitive charge). The original faradic battery discovery was by Volta centuries ago (the volt, unit of DC electromotive force–EMF, is named in his honor). He used zinc, copper, a paper separator, and saltwater electrolyte to twitch frog’s legs with electricity from his ‘battery pile’. The same ‘electrochemical erosion’ principle is used today by sacrificial zinc anodes to prevent hull corrosion in saltwater.
You can build a modern ‘Volta Pile’ replica sufficient to light a single mini Christmas bulb (for a while) just using two US pennies and a lemon. Sand one of the pennies to remove its copper plating (copper is now so valuable, pennies are only copper plated zinc, yet the US treasury still loses money on each one minted). That gives you Volta’s zinc and copper electrodes. Insert both mostly into deep paring knifed slits about ¼ inch (max 1 cm) apart in an unpeeled lemon (pulp is separator, acidic juice is electrolyte). Attach two wire clips to the protruding penny edges and then to the single mini-bulb leads (completing a DC circuit where polarity does not matter). A low voltage DC current flows sufficient to light the resistively heated mini-bulb, until the copper plating on the unsanded penny is electrochemically eroded. Makes a great entry-level high school science fair experiment. This easy home experiment also illustrates one of the many ways all batteries, rechargeable or not (as here), have limited lifetimes much shorter than grid lifetimes.
Pseudocapacitance is rare and complicated. We mostly skip it. There were some DARPA funded ruthenium hydroxide based efforts a decade ago, all failed. Evans Capacitor has sort of one based on tantalum, but Dave’s expensive high power military device for single side band fighter aircraft radar power pulsing is actually an electrolytic cap (defined below) with pseudocapacitive ‘overtones’.
Capacitive storage comes in two flavors: all ‘solid state’, or across some ‘Helmholtz’ layer. All ‘solid state’ is most of electronics billions of little ‘chip caps’ today, just two metallic conductors separated by a ceramic dielectric. The Leyden jar was their progenitor. Even ‘wet’ aluminum electrolytic capacitors susceptible to electrolyte drying failure are technically still in this ‘solid state’ flavor. Very fast, almost infinite cycle life (except for wet dielectrics), but very faradic low charge storage. Dave Evans’ brilliant tantalum military stuff is still just a very high power density version of the wet form of ‘solid state’. All caps of this ‘flavor’ have grossly insufficient energy storage to complement grid renewables.
The other flavor uses the Helmholtz ‘electrolytic double layer’ capacitance effect. The most familiar example is thunderstorm lightning, which Helmholtz first explained (the ‘electrodes’ can be vapor to water, or water to ice—probably both in any big Tstorm cloud). The commercial example is a supercapacitor (aka EDLC). Cycle life is a couple of million full discharges. Used in power dense applications (think Navy rail guns), but at best only about 1/10 the energy density of a high power LiIon battery. They are used in grids as ‘statcoms’ up to about 4 MW, primarily for power factor correction and related grid frequency support. Not nearly enough EDLC energy density for renewable intermittency grid support.
Green woke Formula 1 racing tried, then dropped, both high power LiIon and EDLC hybrid designs. Too many car battery fires thanks to lack of sufficient LiIon power density, while EDLC were (prior to my issued carbon materials patents) physically too big to easily fit the car racing chassis at F1 horsepower. F1 finally dropped their woke green hybrid racing experiment totally—bad for business. Real world intruded. Below is a hybrid Mercedes F1 in Singapore, after a practice lap, after its high power LiIon blew up with the driver sitting on top of it.
As a potentially complicating (and hopeful future) side note, a speculative post over at Judith Curry’s Climate Etc some years ago concerned Henrik Fisker’s second electric car venture. There is a hybrid half battery/half EDLC device variant (one electrode of each type) melding attractive properties of both (high energy and power density, 20000 cycle life). It is in limited production for things like large inductive motor power factor correction. Invented then sold by Subaru since not good enough then for hybrid EVs. As yet not commercialized for EV’s save for Fisker, and even he deferred to LiIon for his first ‘Fisker2’ vehicles.
All energy storage devices are characterized by three basic physical parameters ignoring cost: (1) energy density (how much charge they hold, aka how long they take to discharge, in Wh), more is better, (2) power density (how many charge/discharge Amps per second), higher is better, and (3) rechargeable battery cycle life, where higher is always better.
It is fairly easy to get 2 of 3 of these in any commercial rechargeable battery system. Getting all three in one device is REALLY hard.
For example, PbA (2+3) are car starter batteries. PbA (1+3) are golf cart batteries. ALAS, they are NOT interchangeable. The former uses thin electrodes for power. The latter uses thick electrodes for energy. The cycle life of the former is about 2x greater than the latter since the former (by definition) do NOT normally discharge nearly as deeply as the second. Deep discharge always chemically deforms the PbA electrodes more rapidly via (large crystals) sulfation and thus shortens cycle life. A starter battery is dead from sulfation after about four full discharges. Is also why older starter batteries usually die in winter.
The degree and rate of discharge/recharge has a profound impact on battery cycle life for several reasons. Simply put, ‘full’ charge/discharge EV batteries of the same chemistry will last much less than hybrid EV batteries like in my Ford Hybrid Escape, MY 2007, NiMH chemistry, now 13 years old and still going mostly strong (engine start exception after sitting a week due to slowly increasing leakage current, which Ford foresaw by providing a ‘jump start’ [not really] button to use as the battery ages and the car sits more), because the hybrid traction battery charge always floats only between about 45% and 55% of full charge.
BTW, my hybrid Escape made imminent economic ‘green’ sense. It is a small but sturdy I beam SUV, AWD with class one tow hitch, total HP ~210 (comparable to the 3 liter V6 variant). The HP comes from a downsized 1.4 liter Atkinson cycle I4 at 140 HP, and about 70 HP equivalent from the electric machine. (Atkinson cycle sacrifices torque for about 15% fuel efficiency over the Otto cycle—but it doesn’t matter because the electric machine more than makes up any torque deficit). The MY2007 V6 got about 22mpg highway and about 18mpg city. Our hybrid version still gets about 32 city and 28 highway (well, 27 at our usual 75 mph with summer AC on). The hybrid premium over the V6 was almost exactly $3000; in 2007 the hybrid federal income tax credit was about $3000 (not a coincidence, a Ford pricing strategy). So we were making money from fuel savings on the day we drove the car home from the dealer. Best part is, our I4 Atkinson uses regular gas; the equivalent Otto V6 needed premium. Where we are, the octane difference is over a dollar a gallon. Fewer yet cheaper gallons.
By far the most numerically common rechargeable battery now is Lithium Ion (LiIon) aka the lithium rocking chair, invented more than 30 years ago. It is in a sense partly pseudocapacitive via its ‘rocking chair’. Lithium ions migrate on charging from their chemical home metal cathode, thru a Lithium Ion electrolyte, to intercalate into the carbon anode (the rocking chair). Intercalation involves no chemical change to the anode, just lithium ions ‘snuggling up’ to their ‘rocking chair electrons’ inside the carbon anode. Only the metallic cathode (where the cobalt is) changes chemically with charging/discharging.
LiIon energy/power limitations are similar to PbA. Making everything thinner gives more surface area per battery volume for maximum energy density. A Tesla EV battery is big enough for range that power density is not a primary consideration except in charging. Its cycle life limitations are different but still constraining. F1 LiIon made things thick for power density—just not enough.
There is a secondary relatively low power density consequence for Tesla. Rapid charging generates more heat than can be easily conducted away. The Nernst equation says that heat kills cycle life (above ~40C, about 2x per 10C). Something Tesla does NOT say about its rapid charge stations. You can rapid charge often for convenience, but doing so will also kill your car’s Tesla battery quite early. Perhaps an undisclosed Tesla financial warranty liability?
Of course, as the ‘stunt’ Tesla grid battery installation in South Australia shows (more about it follows), it is NOT economic and cannot hold up the grid for very long. And since Tesla introduced its home grid ‘Powerwall’ s few years ago, the price has increased (not decreased, per Gigafactory promises) about 35% while the warranty was cut by about 1/3. Not a good economic deal.
Future battery possibilities
These tend to come in three hopium flavors.
First, nanotech will come to the rescue. Except all the examples to now were either frauds (Silurgy, NanoOne), or failures like A123 Systems, or speculations without even lab proof of concept like a recent WUWT post about lithium sulfur.
Second, flow batteries for the grid (where the charge is stored in the liquid electrolyte rather than in the electrodes, so with sufficiently big electrolyte tanks energy density is theoretically unlimited). Except all these various flow chemistries have commercially failed to date despite California encouragement and much VC investment. Low cycle life and/or high cost (bulk vanadium isn’t cheap, and cheap rhubarb hasn’t cycle life). See essay California Dreaming in ebook Blowing Smoke for several (now a bit dated) specific illustrated examples.
Third, exotic chemistries like sodium sulfur work, but are expensive and very high temperature. Lithium sulfur (a recent WUWT post on new theories about how to solve the two problems that still exist) are without even yet even lab proof of concept because of the inherent engineering difficulties of making one.
Two final definitional climate warrior ‘ammo’ reminders
First, batteries live in a DC world. Grids live in an AC world. There is always the significant added cost and limited reliability of the necessary high voltage high power DC/AC interfaces. Quoting battery cost without the unavoidable interface cost is intellectually dishonest. Tesla Powerwall 2 came in either DC only, or DC/AC integrated. The price difference in 2017 was about $1500 on a 14KWh base DC battery then about $5500. So about plus 30% for grid interface costs.
Second, using batteries to solve renewable grid intermittency is something touted by Elon Musk, and ‘gifted’ by him to South Australia after their 2016 renewable induced disastrous grid blackout. But Elon used a simple marketing ‘con’, same as the California flow batteries exposed in essay California Dreaming.
It is perfectly possible to truthfully specify a grid battery installation in MW. After all, it has those. BUT the grid intermittency relevant value is MWh (how long the battery lasts providing those vital MW of backup electricity). When the MWh answer is minutes while the grid MWh need is hours, the installed grid MW battery capacity joke is on you while your grid goes dark.
Elon ‘conned’ South Australia (IMHO to gain free ‘advertising’), and Australia’s MSM never caught on. Tesla’s Hornsdale, SA facility (below, now expanded by 50%) delivered 150 MW! But only 189MWh. It can hold up the SA grid for little more than an hour. The South Australia blackout duration depended on where you were; metropolitan Adelaide was restored first. Central Adelaide was dark for at least three hours. More symbolic hopium that doesn’t work in the real world.