NiFe (aka Edison) Batteries and Renewable False Hopes
By Rud Istvan
This post was inspired yet again by another Charles email alerting me to a new BBC post. He referred it knowing that I have some expertise in energy storage systems and their related materials. So, I dug around, then called him and said, YUP, another possibly sardonic guest post. So here we go.
The new BBC article is yet another in an innumerable series of MSM attempts to ‘future’ solve one of two fundamental inherent deficiencies in renewable wind and solar—intermittency. (The other is grid inertia.) For a different set of intermittency battery ‘solutions’ see essay California Dreaming in my ebook Blowing Smoke. BBC now touts the “battrolyzer”, a nickel/iron battery invented by Junger in 1899 as a less toxic but similar electrochemistry to NiCad, (nickel/cadmium), adopted by Thomas Edison for electric vehicles in 1901, and now enhanced to maximize byproduct hydrogen, which together will solve the intermittency problem. This is NOT new electrochemistry news; rather, a completely ignorant MSM ‘GND’ piece based solely on Delft University puff PR. Bad reporting of bad reporting; the GND echo chamber remains very loud.
The Nickel(oxide/hydroxide)/Iron battery was invented by the Swede Junger about 120 years ago as an environmentally friendlier alternative (same electrochemistry) to NiCad (popular in the 1980’s to early 1990’s, now for all intents and purposes environmentally gone because cadmium IS toxic). Iron replaced Cadmium, with some ‘disadvantages’ noted below. Thomas Edison (TE) championed it for his electric vehicles in 1901; unfortunately for TE, gasoline soon won out for many reasons including energy density and cost. NiFe battery chemistry remained in US production until about 1975 for specialty applications like railroad signaling (performance details below), and it still remains in Chinese production (cost details below).
The reason BBC became excited about the new University of Delft PR was that NiFe not only stores electricity, on charging it also electrolyzes the water-based electrolyte and produces hydrogen. So do Lead Acid, (PbA), batteries but to a much lesser extent. For TE electric 1901 vehicles, explosive hydrogen was a problem. Per BBC, this is now a terrific advantage. So, we have to divvy up the new BBC article into two parts: grid storage batteries, and hydrogen.
NiFe as a grid battery
The basics are that Iron(Fe) is the anode, and Nickel(oxide/hydroxide) is the cathode. The electrochemical charge shuttle is like NiCad, a standard oxygen mediated redox. The typical electrolyte is aqueous potassium hydroxide (hence the hydrogen electrolysis). An advantage over lead acid (PbA) chemistry is tolerance of overcharge/overdischarge giving long life, about 20 years rather than maybe 4-5 in babied PbA (golf cart/trolling motor deep cycle batteries). Depth of Discharge (DoD) for 20 years NiFe cycle life is about 80%. All wonderful—BUT.
Battery details matter. The Ni/Fe charge/discharge rate is VERY slow, unlike PbA. A full charge from 80% DoD discharge takes about 7.5 hours (in energy storage terms, a slow C rate). So unlike TE’s hopes, could NEVER have been used as a car starter battery requiring high currents for a short period (a high discharge C rate). The charging efficiency is only about 65%, the discharge efficiency is only about 85%. Translation, NiFe is not only inefficient, it therefore heats up a lot in use both ways. Heat is a big problem with large grid scale batteries.
The nominal voltage of a single NiFe cell is 1.2V, so unlike a standard 12V 6 cell PbA, 12V NiFe requires 10 cells. That is why it is about 30% more expensive per 12V at any AH. More cells, more battery, so more cost for equivalent capacity.
Another problem. Unlike PbA or LiIon, the self-discharge of NiFe is a bit more than 1% per day, or 30-40% per month depending on details and ambient temperatures (that darned electrochemical Nernst equation again). So if it just sits finally charged waiting on the next UK grid wind outage, after a month UK can write off about a third of its previously stored capacity.
Another big problem is based on current Chinese NiFe production pricing. A simple industrial 24V effective 2.2KWh capacity battery presently costs $2107. So to get close to UK grid voltage (using Kip Hansen reasoning) by wiring two in series to get 48V (close enough for this example), it costs ($4214/2.2KWh amortized over ~20 years or ~$0.96/KWh ignoring interest. Even in super expensive Germany thanks to its renewable Energiewende, it is now ‘only’ about $0.30/KWh. That is about 3x higher cost than Germany for this ‘new’ BBC ‘solution’ in the best case.
NiFe as a hydrogen generator
There are many problems with hydrogen. See essay Hydrogen Hype in my aforementioned ebook for a vehicular take. One of the disadvantages of the 1901 Edison NiFe battery was its hydrogen generation. Delft now tries to turn that into a grid advantage by optimizing to coproduce H2 fuel from excess renewable electricity during NiFe charging. Hence Delft’s catchy new name ‘battrolyzer’.
There are a few very basic hydrogen problems. Foremost, electrolysis efficiency is at best ~70%. That may also explain Delft’s NiFe charging efficiency of only ~65%.
Bigger problems arise in storing any generated hydrogen. There is a very well-known problem in iron and steel containment (pipes, tanks) called hydrogen embrittlement. The first paper on it was published in 1875. Now, there are partial solutions using exotic coatings. The general class is called ‘hydrogen penetration barriers’. These are mostly top secret and cost insensitive, since developed mainly by Los Alamos to conserve tritium in (hopefully) inactive hydrogen bombs.
Storing hydrogen as a liquid is possible, but wastes incredible chilling electricity. To merely compress it loses ‘only’ about 10% (as we all know from bicycle tire pumps and high school chemistry where PV/T=k). Compressing a gas heats it up, and that heat is wasted.
IF we could somehow efficiently and safely store bulk hydrogen from grid scale renewable battrolyzers, we would still have major engineering problems. The BBC/MSM fad in the UK is to replace natgas with ‘clean’ hydrogen, somehow produced. That ignores the hydrogen embrittlement and hydrogen leak distribution pipe problems from chemistry’s smallest and most mobile/permeable atom.
So, two possible ‘tandem’ solutions are maybe present together. First, somehow safely store grid scale bulk hydrogen byproduct in situ. A new permeability coating non-H-bomb related. Then, either burn it in a gas turbine with just steam exhaust, or consume it in a fuel cell (see essay Hydrogen Hype for fuel cell considerable net thermodynamic difficulties). The only problems are, we dunno how to do the first except for H-bombs, and for the second the thermal regeneration efficiency is still at best about 60%.
So, BBC implicitly suggests we use a battrolyzer to compressively store green ~30% of wind nameplate capacity (its capacity factor) at a battrolyzer efficiency of maybe 65%, netting (0.3*0.65*0.9) ~18% energy storage efficiency. Then we use that at about at best ~60% efficiency to regenerate electricity for the grid, a net round trip efficiency of maybe (0.18*0.6) 0.11% from the originally subsidized renewable generation. What a great deal–NOT.
In the US, we have just learned from the Biden administration that such simple math as this, and then showing its homework, is racist. This post therefore also explains why that warped view is now the prevailing GND ‘wisdom’. According to the BBC battrolyzer math, 2+2=5–(or just for GND battrolyzers =3).
via Watts Up With That?
March 9, 2021 at 04:30PM
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