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Energy Storage; Something Old, Something Old

By November 24, 2014November 7th, 2021Energy Efficiency, Energy Rant

Want a fast car?  How does a 1972 Datsun sedan sound?  These are related and not two back to back stupid questions.  This baby, the “White Zombie”, can burn from 0-60 in 1.8 seconds.  Per my calculations, this is about 1.5 Gs of acceleration; not quite aircraft carrier catapult (0-160 mph in the same ~2 seconds) acceleration but enough to thrash any “gasser” muscle car on the market.  The secret sauce?  Thirty-six humdrum 12 Volt batteries crammed in the back seat, plus two powerful electric motors, like those in a forklift.  This provides a good lesson and starting point to this post regarding energy storage for the grid.

This I had discovered in, you guessed it, The Wall Street Journal several years back, and I needed to look it up in response to a reader comment that was raving about the qualities of the modern Tesla S.  It has great acceleration!  Whoopty doo.  Refer to the Zombie, which would leave the Tesla (not even half as fast) in its sonic wake.

What makes the Zombie so fast is the incredible power-dissipation rate of electricity.  The only limiter is the power of the drive motors and the size of the conductors (cables).  Also, per my calculations, the 36 batteries each store about a half kWh of electricity.  Adding it all up and throwing in some conversions, there is enough stored energy in the batteries to equal about 1.5 gallons of gasoline that would be/could be burned in a conventional engine.  What makes the Zombie so fast is, for all practical purposes, no limit on the size of the would-be gasoline engine.

In fact, incredibly fast dissipation of energy is one thing that makes electricity so dangerous.  Arc flash due to a short circuit in which a massive flow of electricity is too great for whatever the flow path (metal) is, and not just melting it, but vaporizing it, like steam.  But it happens in a millisecond timeframe and for example, vaporizes copper which expands 7000x.  Rapid expansion = explosive pulse = injury, burns, possible death.  After Jeff set off a little fireball in a light-switch box because he didn’t know what he was doing, and he later learns about arc flash – he stops dinking around with electricity!


Along with smart grid, renewable energy, and demand response is the potential solution of energy storage.  There are various types of energy storage technologies under consideration and development.  I will leave that for another day.

A knee-jerk reaction to the under-informed person might be – “Wow!  This is fantastic!  We can add energy storage to pack away generating capacity in times of excess renewable energy generation and then tap that energy after the sun sets and the wind stops blowing!”

Sure.  It’s the same as every answer to a computing problem: “Is it possible to…”.  The answer is always yes.  The cure comes with nasty side effects, like cost, and unreliability.  But I do believe there is a place for energy storage of various types for various purposes – yes, there is more than one purpose – not just to shift loads to periods of non-renewable energy production.

In this recent article published in Forbes, Ken Silverstein, who writes for Public Utilities Fortnightly, reports that Duke Energy recently tested its “24 megawatt/hour” storage system, known as the “Notrees Energy Storage Project”.

I have a beef with Silverstein.  Exactly what is a megawatt/hour – a megawatt per hour.  That is a power ramp speed – like, I need to add 1800 MW of supply in the next hour as the sun sets, but I doubt that’s what he means here.  Does he mean megawatt-hour, as in 1000 kilowatt hours we are all familiar with?  Later he talks about California requiring its utilities to add 1325 megawatts of energy storage capacity.  What does that mean?  I have 1325 MW of capacity in my car battery, but it’s only available for 0.00000038 second.  I beat up our engineers for writing this nebulously.  C’mon.

I’m going to go out on a limb, because I have to, and guess Silverstein means megawatt-hours, which is totally different than a MW/hr or a MW.  In this case, the Texas storage project would store the electrical energy produced by about 16 wind turbines generating power at a relatively high load factor, for an hour.  Sixteen turbine-hours of energy. That is tiny.  Seen a wind farm lately? Hundreds of turbines.

This brings me to the first and primary benefit of energy storage. If you haven’t read this AESP strategies article, you should.  It sets the stage for the purpose of the Notrees Energy Storage Project.

Renewable sources of energy, namely photovoltaic, have very little frequency response.  That is, they produce power at 100% of their available capacity at any time, from nameplate capacity with sun high in the sky, to zero when the sun is shining on the other side of the planet.  Lack of frequency response adds instability to the grid because it loses ability to respond to either surges in demand or sudden losses of generation, like a steam turbine going down for some reason.

Since stored electricity, in the form of batteries, can dissipate power fast and almost instantly, viola, we have the number one benefit of stored electricity.  It isn’t the value of the stored energy that is worth squat in the general sense.  If my assumption on units above is right, it would be about $1900 per kWh for the storage – a might bit pricey.  However, this storage can have enormous value by stopping cascading blackouts due to inadequate frequency response.  This, apparently, is precisely the purpose of the $44 million Duke Energy Notrees project.

The bleeding edge storage technology: lead acid batteries – i.e., car batteries, only most likely larger ones.

Jeff Ihnen

Author Jeff Ihnen

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