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Question from a total ignoramus here. TLDR: Despite recent progress, is it possible that fusion will reach efficiency where it is net positive in energy output

Question from a total ignoramus here. TLDR: Despite recent progress, is it possible that fusion will reach efficiency where it is net positive in energy output but still too expensive to be useful? Long Version: When I first heard about fusion, the idea was that this immense energy could be harvested taking advantage the the conversion of matter into energy. Everything I heard was that the quantities are so great that if we could just nail the sustained fusion reaction we could harvest potentially limitless energy. As I've come to understand it however, it is not so simple. The big question is in how long you can sustain the reaction and how much energy it costs to start it in the first place. It seems to me the strides that have been made over the last few decades are to bring the cost down enough and extend the reaction long enough that the net energy loss is lower, then break even and now possibly a net gain. I've seen some articles imply that this turn of events means fusion is definitely on the table as a near future abundant energy source. My question is this. Is it a forgone conclusion that the current trends will continue? Because if not, doesn't that mean fusion could still get stuck somewhere where there is a net energy gain but it's still too expensive to be useful?

spartanatreyu 5y ago
Yes and no. The first generation of fusion reactors will be expensive and monolithic, but we will learn a lot from them and it will prove their fundamental functionality. The second generation reactors will likely be using better fuels and squeezing plasma into different shapes to keep them running as long as possible. Even if other renewable energy sources continue to get cheaper and become prolific, they still have the problem of energy storage. Simply put, we don't have anywhere near the resources required to build all that storage. So what we need instead is a solid mainline energy source (nuclear and fusion). In the case of a massive breakthrough in energy storage, at best it will just delay fusion power. We will still need to use fusion off planet.
- hutzlibu 5y ago
  "we don't have anywhere near the resources required to build all that storage." Sources? There are lithiumfree batteries, made from cheap metals. Saltwater batteries for example. Airpressure as energy storage. Hydrogen or more processed into methanol .... Etc., etc. all working technology as of today. And sure, sure, storage comes with lower efficency, but there is no reason, we cannot transform the various deserts into big solarplants. Fusion would be awesome to have. But I see no indication, that it will be ready anytime soon, when we need it, to produce clean energy at scale. And if it is ready, we probably still need resources, like Helium-3. Ready to mine the moon?
twanvl 5y ago
I don't expect building a fusion power plant to become cheaper than a gas power plant. Both need steam turbines, cooling pipes, a big building, etc.. So that would be a lower bound on the construction cost. If solar+batteries can outcompete fossil fuel plants (while ignoring fuel costs), then fusion likely wouldn't be viable commercially. And if you look at [the data](https://en.wikipedia.org/wiki/Cost_of_electricity_by_source#Capital_costs https://en.wikipedia.org/wiki/Cost_of_electricity_by_source#...), we are already close to this point.
hutzlibu 5y ago
"Despite recent progress, is it possible that fusion will reach efficiency where it is net positive in energy output but still too expensive to be useful" This is very likely and expected. First we need that positive output - then we can improve and scale up .. and then it might be worth it.
- willis936 5y ago
  Keep an ear out for ITER doing exactly that in 10-15 years. First plasma in 5. ITER was designed with LTS coils and will cost in the range of 50 billion USD. HTS coils are a big deal for driving size and cost down. MCF is still the king in terms of fewest engineering hurdles to overcome. Mirrors and liquid metal pistons are certainly neat avenues and should be explored, but you won't see them in 1st generation plants.
  - DubiousPusher 5y ago
    Do you think some of the projects currently in development which are for teating but not useful efficiancy like ITER might later be retrofitted with bwtter technology which could make them efficient enough for utility?

spartanatreyu 5y ago

Yes and no. The first generation of fusion reactors will be expensive and monolithic, but we will learn a lot from them and it will prove their fundamental functionality. The second generation reactors will likely be using better fuels and squeezing plasma into different shapes to keep them running as long as possible. Even if other renewable energy sources continue to get cheaper and become prolific, they still have the problem of energy storage. Simply put, we don't have anywhere near the resources required to build all that storage. So what we need instead is a solid mainline energy source (nuclear and fusion). In the case of a massive breakthrough in energy storage, at best it will just delay fusion power. We will still need to use fusion off planet.

hutzlibu 5y ago
"we don't have anywhere near the resources required to build all that storage." Sources? There are lithiumfree batteries, made from cheap metals. Saltwater batteries for example. Airpressure as energy storage. Hydrogen or more processed into methanol .... Etc., etc. all working technology as of today. And sure, sure, storage comes with lower efficency, but there is no reason, we cannot transform the various deserts into big solarplants. Fusion would be awesome to have. But I see no indication, that it will be ready anytime soon, when we need it, to produce clean energy at scale. And if it is ready, we probably still need resources, like Helium-3. Ready to mine the moon?

twanvl 5y ago

I don't expect building a fusion power plant to become cheaper than a gas power plant. Both need steam turbines, cooling pipes, a big building, etc.. So that would be a lower bound on the construction cost. If solar+batteries can outcompete fossil fuel plants (while ignoring fuel costs), then fusion likely wouldn't be viable commercially. And if you look at [the data](https://en.wikipedia.org/wiki/Cost_of_electricity_by_source#Capital_costs https://en.wikipedia.org/wiki/Cost_of_electricity_by_source#...), we are already close to this point.

hutzlibu 5y ago

"Despite recent progress, is it possible that fusion will reach efficiency where it is net positive in energy output but still too expensive to be useful" This is very likely and expected. First we need that positive output - then we can improve and scale up .. and then it might be worth it.

willis936 5y ago
Keep an ear out for ITER doing exactly that in 10-15 years. First plasma in 5. ITER was designed with LTS coils and will cost in the range of 50 billion USD. HTS coils are a big deal for driving size and cost down. MCF is still the king in terms of fewest engineering hurdles to overcome. Mirrors and liquid metal pistons are certainly neat avenues and should be explored, but you won't see them in 1st generation plants.
- DubiousPusher 5y ago
  Do you think some of the projects currently in development which are for teating but not useful efficiancy like ITER might later be retrofitted with bwtter technology which could make them efficient enough for utility?