It’s probably safe to say that nearly everyone who talks or writes anything about energy and power has made the mistake – perhaps only as a typographical error – of writing or saying “gigawatt” in a situation where the correct term is “gigawatt-hour”.

Those of us who have real understanding of the topic, however, will either quickly correct the typo when it is pointed out, or we will think for a minute to recognize which of those two units is correct in the situation under discussion.

For some people who like to talk about energy, however, the problem is something more than just a typographical error. They really do not quite understand that a watt (whether modified by a prefix of nano, kilo, mega, or giga) is a unit of power while a watt-second (or gigawatt-hour) is a measure of energy.

They may not even recognize that power and energy are two very different and equally important items worth measuring correctly. They may even fail to understand the importance of using the correct units in any expression of a measured parameter.

The proper reaction a reader or a listener should have to anyone sharing an opinion about energy and power who stubbornly will not correct units or who can’t tell the difference between energy and power is to stop accepting that person’s words and work.

Aside Would you give any credibility to a financial advisor who casually confuses a weekly paycheck and a bank account total or who thinks that its just a typo to list say that your dividend will be 1000 dollars when it is actually 1000 yen? End Aside.

I came across a post this morning that stimulated the above musing. Titled Lying is Not Okay, it is a lengthy defense of Mark Z. Jacobson’s decision to file a lawsuit against the National Academy of Sciences and Christopher Clack.

Clack was the lead author – with 20 co-authors – of a peer reviewed paper that provided clear refutation of Jacobson’s influential paper.

That work, published in the Proceedings of the National Academy of Sciences. claimed to demonstrate via modeling that transitioning our energy supply system – not just our electricity supply system – from its current mix of sources to a new mix made up entirely of wind, water and solar power would be achievable at a cost that is close to or less than the cost of business as usual.

The paper’s title makes clear its ambitious intent and its conclusions Low-cost solution to the grid reliability problem with 100% penetration of intermittent wind, water, and solar for all purposes.

A full telling of the saga surrounding Jacobson’s original work, the work to refute that work in the same academic journal that hosted the original paper, and Jacobson’s reaction to the criticism is beyond the scope of this post.

However, after reading the defense of Jacobson referenced above, I felt the need to respond. This is what I wrote.

Brandon

The issue that MikeN raised illustrates that you share a GCE about electricity and basic physics with Mark Z. Jacobson. (GCE – Navy Nuclear Power School lingo for Gross Conceptual Error.)

The difference between power (measured in watts – aka joules/second) and energy (watt-seconds – more simply just joules) is fundamental and extremely important for understanding how the systems that enable us to function actually work.

By definition, power is an instantaneous measure of a system’s output – right now – and power capacity is a system limit of the MAXIMUM that the system can produce at any instant.

If a hydropower system has a capacity of 1000 GW, it can NEVER produce more power. Even for an instant. That capacity is a function of a complete system that has pipes, valves, dams, transformers, wires, turbines, riverbeds, etc with fixed dimensions. At the rated capacity, the water is moving as fast as that system will allow and the wires are carrying as much current as they can without exceeding physical limits.

Adding capacity to a hydroelectric system is thus a completely non trivial task whether it is a traditional dam with reservoir, a run of the river turbine system, or a pumped hydro system.

If anything, the Clack et al response to Jacobson’s stubborn defense of his CGE is too respectful and deferential. It is simply IMPOSSIBLE to produce valid results from a model that includes such a fundamental error as failing to constrain output of hydroelectric systems to their rated capacity. If the demand on the system requires the hydro components to produce significantly more than their capacity for even an instant, the grid being modeled should only be able to remain operational by abruptly cutting off loads.

Failing to constrain any power source output to its rated capacity in a model purporting to balance supply and demand at all moments is such a serious modeling error that I am completely befuddled about why it took so long for the academic community to reject the work as being wrong. Many of us who are not academics and have no incentive to participate in its “peer reviewed journal article” process have been saying for years that Jacobson’s 100% renewable solutions project is fundamentally flawed.

We’ve done our best to try to convince Jacobson to revise or retract it. For whatever reason, MZJ has refused all assistance. His frequent response to criticism has been to summarily block them on Twitter.

Rod Adams
Publisher, Atomic Insights
Resume available upon request

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Update: Posted November 8 at 0545

Brandon responded to my comment on his blog. Here’s what he wrote.

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Brandon Shollenberger
November 7, 2017 at 7:49 am

Rod Adams, if you’re going to use rhetoric to criticize other people’s understanding of things, you should try to refrain from making simple mistakes yourself. You say:

By definition, power is an instantaneous measure of a system’s output – right now – and power capacity is a system limit of the MAXIMUM that the system can produce at any instant.

If a hydropower system has a capacity of 1000 GW, it can NEVER produce more power. Even for an instant. That capacity is a function of a complete system that has pipes, valves, dams, transformers, wires, turbines, riverbeds, etc with fixed dimensions. At the rated capacity, the water is moving as fast as that system will allow and the wires are carrying as much current as they can without exceeding physical limits

Exactly what you are thinking is a bit opaque as the phrase “power capacity” is not a term which has any common meaning that I can find. Regardless, you’re wrong on even the most basic aspect of this. You say a facility “can NEVER produce more power” than its nameplate capacity, but that’s simply untrue. Nameplate capacity is the sustained load, over a long time, the facility is rated for. Nothing prevents a facility from going over that value for a period of time, except for the costs doing so would incur in things like repairs.

Beyond the fundamentals, what you describe is false as, again, nameplate capacity is about sustained loads. Facilities which store energy such as pumped hydropower stations, can store excess energy so they can tap into it when demand gets high. One can see the same behavior with capacitors. A circuit with capacitors can store energy in the capacitors then later discharge that energy to get a surge of power far exceeding the normal levels in the circuit.

You can jump up and down, throw around rhetoric and even insult people all you want, but waving your hands around and declaring things to be impossible doesn’t make them impossible. Facilities can have instantaneous discharge rates exceeding their nameplate capacity. There is nothing which prevents that.

Failing to constrain any power source output to its rated capacity in a model purporting to balance supply and demand at all moments is such a serious modeling error that I am completely befuddled about why it took so long for the academic community to reject the work as being wrong. Many of us who are not academics and have no incentive to participate in its “peer reviewed journal article” process have been saying for years that Jacobson’s 100% renewable solutions project is fundamentally flawed.

Anyone who shares your views has no idea what they are talking about. Nameplate capacity is a measure of the long-term, sustained electrical production of a facility. It is a long-term average. The instantaneous output of a facility is not a long-term average. It is the instantaneous discharge rate. The instantaneous discharge rate is in not bounded at the long-term average, or sustained, production rate.

If you wish to continue insisting it is impossible to have an instantaneous discharge rate exceeding the installed capacity of a facility, I suggest you do more than just demand everyone accept what you say as true. A simple step would be to try a small, hypothetical example. An obvious one is the one I alluded to above – capacitors in a system with a generator. Once the generator charges the capacitors. what will happen if the capacitors are discharged?

According to Jacobson, there will be an instantaneous discharge whose numbers could go higher than the “installed capacity” of the generator. According to you theory, there wouldn’t be.

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Several commenters have attempted to correct Brandon’s continuing GCE. I also responded.

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Rod Adams
November 8, 2017 at 5:27 am

Brandon

I was not using “power capacity” as a term. The nameplate capacity of a system is expressed in watts because that is the units by which power is measured. A watt is a derived unit, the root unit is joule/sec (energy/time).

When a system capacity is determined, it is the limit of energy per unit time that the system can deliver. As I noted in my original comment, it is a function of a number of system components that all have finite dimensions and can allow only so much fluid to flow or current to be moved.

Capacitors are components that can be connected to a power generation system to provide the capability of storing energy – up to a fixed amount determined by the physical design of the capacitor – that can then be nearly instantaneously discharged. The output of capacitors is generally not subject to any regulation, they are either in the mode of being charged, storing energy, or being discharged immediately.

Capacitors are not normally considered to be part of a power generation system. They are separate components that MAY be connected to the output of a given system.

Here’s an example that your readers might understand, even if you stubbornly defend your conception of how energy and power are related.

A Honda Civic might be sold with a 100 horsepower engine. Translating that limit into SI units, it has a capacity of ~ 75 kw. That number is the max power it can provide which governs parameters like acceleration and maximum velocity.

It can be sold with a 10 gallon gasoline tank. Since gasoline contains 40 kilowatt-hours per gallon, the tank can store 400 kilowatt-hours of chemical energy. The gasoline (Otto cycle) engine is roughly 25% efficient in converting chemical energy to rotational energy.

Running at rated capacity, a 75 kw (output) engine consumes 300 (75 kw/0.25) kw-hrs of chemical energy each hour. The system we are talking about could burn up the stored gasoline energy in about 1.33 hours if the operator had a place to run full throttle.

If the owner of that car wasn’t satisfied with the car’s acceleration and top end velocity, she could take action to increase the engine power by altering various physical components in the system to make fuel flow faster, add additional air, etc. There is not a fixed limit on how many such alterations are possible, but anyone suggesting that there is a low cost way to increase that Civic’s power by a factor of 13 to give it a 975 kw engine would not simply be laughed out of a garage.

They would be ignored, ridiculed or tossed out of the garage.

Rod Adams

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