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.
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.
Publisher, Atomic Insights
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