Comment by hinkley | Hacker News Reader

Comment by hinkley | Hacker News Reader

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Climate change not solved. This is another in our long series of silver bullets.

Greenhouse gases retain heat. Sea level temperature is a function of ambient heat due to sunlight and other heat sources, minus the rate at which it dissipates into outer space, mediated by the insulation effect of the atmosphere.

Projects that try to reduce the carbon intensity of energy are focused on changing the denominator in the equation. The current aim of these projects is to produce a cheap and plentiful energy source, via a heat engine. What they are actually chasing, whether they admit it to themselves or not, is a cheap and plentiful heat source. If they succeed they change both the numerator and the denominator, which ends up partially cancelling each other.

Wind and solar are different because they tap into an existing heat engine, instead of trying to build a new one.

What we as a people need is a fusion plant that costs less per KWH than a fossil fuel power plant with tariffs to account for the cost of the carbon dioxide, but still about as expensive as a fossil fuel plant where the carbon is free. If we actually got a fusion plant that was 10x more cost efficient then we'll just introduce the concept of heat pollution to the conversation, swapping out the villain in the story but keeping the same outcome.

Heat pollution from power generation is a non-problem. We will run out of raw materials to build power plants out of long before this happens. This is what happens when people don't run the numbers.

Are you saying the heat output of a fusion generator would be so great that it would impact climate change?

If you give people a generator that produces "cheap and plentiful energy"? Absolutely. Total world power dissipation increases as fast as they can build the plants. If we never produce another molecule of CO2 again we might be okay in that situation, but things like that don't change overnight.

edit: conclusion

edit again: I'm extrapolating from https://en.wikipedia.org/wiki/Jevons_paradox but didn't remember what it was called

Hardly. The amount of energy trapped by the atmosphere is vastly greater than the heat capacity we would wish to be able to produce, and the corollary - the amount of energy irradiated by the earth into space is vastly greater than amount of heat we wish to produce.

And it was balanced, so it doesn’t matter if it’s fifty terrawatts or fifty million. What matters is:

> The growth in Earth's energy imbalance from satellite and in situ measurements (2005-2019). A rate of +1.0 W/m2 summed over the planet's surface equates to a continuous heat uptake of about 500 terawatts (~0.3% of the incident solar radiation).[2][35]

https://en.wikipedia.org/wiki/Earth's_energy_budget

I found a chart that says we’re producing about 25,000 TWh per year of power now, or 2.9 TW continuous to put it in the same units. But what is the efficiency of those plants? 35%? That’s 8.3 TW of heat, which is already 1.6% of our budget surplus. If we dogleg our energy production while thinking it virtue signaling, that quickly becomes 5% of a number that is slowly cooking us. That brings doomsday in by years.

We can’t endlessly dump heat into the atmosphere any more than we can continuously dump mercury into the oceans.

In your equation above. The sun produces so much more ambient heat I imagine everything else is a rounding error. I highly doubt any number of fusion plants would affect global temperature.

Please check my math here https://news.ycombinator.com/item?id=32760914

I’m getting 1.6% of our heat surplus at present power production rates, and I’m saying what if we triple our power production because it’s cheap and clean now?

Wind doesn’t increase this number. Nor does hydro. Solar only does if the albedo is lower than ambient. Tidal… I wouldn’t even know where to start calculating that. Heat engines increase it by something like 300% of the power that gets to your light switch.

Still negligible.

Fusion and fission are bad ideas on their own merits, regardless of heat they might produce.

Rough order of magnitude calculation, the Earth receives about 1000W/m^2, that's 6370km^2 * pi * 1000W/M2 ~ 1e17W, and according to Wikipedia the global energy use of humanity is 7050 millions tons of oil equivalent per year so 7050 * 11.63TWh / 1year ~ 1e13W. So we have about 4 orders of magnitude of difference here. Does the human heat output make any difference? Probably not.

Adding some invented constraints on to the problem of nuclear fusion is the most bikesheddy thing I've ever read.

What invented constraints? We've been chasing nuclear fusion since long before we really cared about greenhouse gas emissions. We want 'cheap and plentiful power'. Greenhouse gas intensity is a recent addition to the set of goals. It doesn't replace the existing motives, and to claim otherwise is greenwashing.

This one:

> What we as a people need is a fusion plant that costs less per KWH than a fossil fuel power plant with tariffs to account for the cost of the carbon dioxide, but still about as expensive as a fossil fuel plant where the carbon is free

That the fusion plant can't be too expensive, or too cheap.

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