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Comment by sfifs | Hacker News Reader

There's significant power loss in transmission on grid and to avoid power loss, you need fairly expensive equipment to convert to and from high voltage. If you are adding wind to the mix and working on an AC grid as normal, phase sync is also tricky. Electricity supply on grid has to be very closely matched to demand and the problem will likely become fairly complex with lots variable sources. A lot of problems potentially go away if you push renewable to significant battery storage first and you also get a much more resilient grid to natural disasters (see Puerto Rico's situation)

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For an interesting graphic along these lines see [0].

The parent of this comment is talking about increasing the efficiency (reducing rejected energy) and the gp is talking about just increasing the total amount of energy. Both are solutions. But I wouldn't say it is a good thing we reject more than half the energy we create.

[0] https://flowcharts.llnl.gov/content/assets/images/energy/us/...

As an addendum - explanation of the electricity distribution losses on grid:

https://electrical-engineering-portal.com/total-losses-in-po...

Because there's confusion I'm adding an addendum to the addendum. Here's an LLNL scientist explaining the graph. Which he does talk about the rejected energy [0]

[0] https://www.youtube.com/watch?v=G6dlvECRfcI

> But I wouldn't say it is a good thing we reject more than half the energy we create.

The meaning of "Rejected Energy" in that graphic is obscure but it certainly doesn't relate to energy which has been created and rejected. It may relate to excess capacity of fossil fuel plants (how much more they could produce if ordered to burn more fuel).

The US is thankfully not "rejecting" twice as much energy as it is producing as those figures of 68.5 vs 32.7 lead you to believe. Curtailment of wind and solar generation in the US is recently around 2-4%

[1] https://blog.ucsusa.org/mark-specht/renewable-energy-curtail...

Sfifs has an accurate link. But your comment really isn't correct. You suggest it is solely to fossil fuels. There is inherent waste to any electrical system as some of the energy produced goes into heating the wires (unless they are super conductors, but as far as I'm aware solar panels and wind farms don't use ultra high temperature super conductors. Don't even know any that exist tbh). Heat is just the simplest example, but Sfifs liked more information.

> There is inherent waste to ..

What has inherent waste to do with your reference to "Rejected Energy" ? What do you now understand of that graphic ? Transmission losses are generally in the range 5-10% for modern grids. Your interpretation of that ambiguous reference wrongly indicated 66% losses. Thats not reasonable and doesn't support your advice on energy storage. I suggest gaining more familiarity with the general subject before judging it.

The graphic's term for rejected energy includes a multitude of things. Thermodynamic loss is part of it but not all. It was mentioned because it is one of the easiest for people to understand. There has been another link provided that I have already referred you to that includes a more comprehensive breakdown.

But yeah you can act all knowledgeable, or you can listen to the group leader of the LLNL staff that put this chart together using the same exact example I used.[0]

I, again, will say that this is only a portion of the rejected energy. But thermodynamic loss (i.e. heating wires, heating your ICE engine, etc) is part of that rejected energy.

[0] https://www.youtube.com/watch?v=G6dlvECRfcI

I watched the explanation of the chart and it is still ambiguous both what it is, and its purpose. That narrator explains: "Rejected energy is the portion of energy that goes into a process and comes out generally as waste heat" - waste heat is not just as you wrote: "part" of it, it is explained to be "generally" (all of) it. Really neither of us should need to clarify the difference between "part of" and "generally all"

So then "rejected energy/waste heat" can not be used or as we are saying here -"accepted" by better battery storage, which was the opinion that you brought this ambiguous chart and presentation to explain. This chart is irrelevant to battery storage.

Also, most of the energy in the chart is thermo-electric derived from fossil fuel and nuclear plant. Wind turbines and solar "reject" heat energy in completely different manner and lesser degree than thermo-electric plants - it is truly nonsensical to mix the two together under the vague heading of "rejected". It makes so little sense, I do wonder about the credentials or motivation of this LLNL to educate on energy issues.

I think that most rejected energy is on the majority from thermodynamic losses. At least for electric power production. Converting heat to work has large theoretical losses (See Carnot Cycle) and loses due to engineering limits (Turbines aren't 100% efficient). Losses end up as waste heat.

Rejection is an action - whatever it means in that graphic its not a thermodynamic factor. My bet is the figures shown relate to capacity factor, they have no connection to what they have been presented as - a potentially reclaimable amount. Of course the proof should lie in the article which the graphic comes from - its a very messy idea to link and debate graphics which have no clear sense without their article.

Personally I'm not really very happy with that graph since it combines energy inputs into black boxes instead of groupings. Take natural gas, solar, wind, nuclear, and hydro and combine those into an electric power generation' 'fruit basket.' It makes you think you know something, but at the same time makes sure you don't know enough.

Succinctly put, thanks.

Energy loss in the grid is not that dramatic. Average losses are typically well below 10%.

Matching demand to supply is not that hard. If you have oversupply you run pumped hydro, batteries, and power-to-gas plants and store the extra energy. If you have even worse oversupply you disconnect your solar panels, or your wind turbines. If you have undersupply you use the energy you stored previously.

Conventional power plants fail first because they are big and centralized. When a plant goes down temporarily you have a huge gap to fill. With renewables 100 turbines stopping out of 1000 is not a big deal because they don't all fail at the same time.

The problem is that if you have a completely renewable grid (note I'm not saying a zero or low carbon grid) you can't provide large parts of the world (even the US) with that energy unless you direct it from some big hub. An easy to see example of this is that certain parts of America aren't very sunny and/or windy throughout the year (PNW, NE, Midwest, Alaska). Other parts are very sunny and very windy (think desert areas like CA and southwest). This leads to centralization even with renewables. It isn't an easy problem to solve and that's why people suggest things like nuclear, to fill in the gaps. Hydro has been a great filler in many places, but not all of these regions have access to large enough rivers, so again we get some centralization (see Tennessee Valley Authority, who also still use a lot of nuclear).

The problem is 100% solvable, but that doesn't mean it is currently solved or what's left is trivial. We're almost there, but it is hard to finish fixing things when you slap a sticker on it saying "done" and stop addressing the remaining issues.

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