What are disadvantages of nuclear fusion?

[Tex_NL]

Only disadvadvantage i know of is that you need a constant input of energy to keep the fusion running. So if something happens and the fusion power plant has to shut down it will need some initial energy input to get things running again. So you need some backup energy source to restart the reactor. Also the costs running such a plant are probably much higher then other conventional power plants. At the current stage of development they still get no more energy out of the fusion process then they have to input to start it.

The constant power input is actually a build-in safety feature. Stopping the reaction is as simple as pulling the plug.

You underestimate how much deuterium there is on the planet. One in every 6400 hydrogen atoms is a deuterium isotope. This means that if you filter an olympic swimming pool for heavy water you can extract a large bathtub full of the stuff. That's enough to keep a nuclear fusion reactor running for months. The oceans contain enough deuterium to keep us running for millions of years, even if we take into account the exponential power increases of the past centuries. Furthermore, unlike uranium it is very easy to separate deuterium from hydrogen thanks to the large weight difference.

A single bathtub of seawater contains enough deuterium to provide a life time of energy for a single person. Transportation, light, heat, entertainment, everything.

The biggest problem with fusion power is that we can't do it yet. As soon as we have unlimited energy practically free of charge pretty much every world problem can and will be solved. Food and water can be transported all over the globe with ease as it won't cost a dime to get it where it's needed.

[Idobox]

The biggest problem with fusion power is that we can't do it yet. As soon as we have unlimited energy practically free of charge pretty much every world problem can and will be solved. Food and water can be transported all over the globe with ease as it won't cost a dime to get it where it's needed.

Fusion power will not be free at all. Even if the fuel costs are negligible, building and maintaining the power plants will be horrendously expensive, and it's not even sure they will ever be able to compete with fission for cost.

[rtxoff]

As soon as we have unlimited energy practically free of charge pretty much every world problem can and will be solved. Food and water can be transported all over the globe with ease as it won't cost a dime to get it where it's needed.

You are seeing this too optimistic. For such a world fusion is not the key, the people are. Also we have already a huge fusion reactor delivering all the power we need already (look at my avatar pic). We also have the technology to harness it but we lack the mentality to do it.

[Tex_NL]

Fusion power will not be free at all. Even if the fuel costs are negligible, building and maintaining the power plants will be horrendously expensive, and it's not even sure they will ever be able to compete with fission for cost.

You are seeing this too optimistic. For such a world fusion is not the key, the people are. Also we have already a huge fusion reactor delivering all the power we need already (look at my avatar pic). We also have the technology to harness it but we lack the mentality to do it.

I believe it will. Yes reactors have to be build and maintained. And this takes up raw materials that have to be refined and manufactured. But since the energy is nearly free it won't cost much any more to actualy get the materials we need. The only real cost is manpower. And even manpower will become cheaper since people won't need much money anymore as pretty much everything they want will be dirt cheap.

I am indeed very optimistic in this case, unlimited energy for free is the key. Once the domino's start falling even money could become obsolete.

[rtxoff]

I believe it will. Yes reactors have to be build and maintained. And this takes up raw materials that have to be refined and manufactured. But since the energy is nearly free it won't cost much any more to actualy get the materials we need. The only real cost is manpower. And even manpower will become cheaper since people won't need much money anymore as pretty much everything they want will be dirt cheap.

I am indeed very optimistic in this case, unlimited energy for free is the key. Once the domino's start falling even money could become obsolete.

Well i tell you again, we have already free energy, just look in the sky, our sun. We have the tech to use it. We have also the manpower. Are we going to do it because of that? Why do you think if they manage to make usable fusion reactors the world will change? I tell you, nobody is going to built a fusion power plant if he won't earn money with it.

Do you know how the law in my country is? It is forbidden for me to have my own solar plant on the roof if i am not feeding in the power that MY plant produces into the official grid.

Just check the law you folks have in your countries and you know from which direction the wind blows.

[Tex_NL]

Why I am more confident in fusion than solar? Solar (and wind) is clean and cheap but unreliable. You won't get full power in bad weather and nothing at night. Higher latitudes simply receive less energy than lower latitudes but placing solar parks ij the most efficient locations could create a power stranglehold similar to what we have now with oil. Fusion power can run at full power anywhere and at any time. Even at the local level.

[rtxoff]

Why I am more confident in fusion than solar? Solar (and wind) is clean and cheap but unreliable. You won't get full power in bad weather and nothing at night. Higher latitudes simply receive less energy than lower latitudes but placing solar parks ij the most efficient locations could create a power stranglehold similar to what we have now with oil. Fusion power can run at full power anywhere and at any time. Even at the local level.

You heard about an invention named battery right? You know also that there are many other forms of storing electric power right?

And don't come now with some efficiency or expense issues, because they are also true for fusion. And because the initial energy harvested is free i do not care about how efficient my battery is.

It is just a matter of will to do it, nothing else. Even if they manage to build fusion reactors, i highly doubt they gonna let us have our own fusion powered cars/homes.

[Winter Man]

You heard about an invention named battery right? You know also that there are many other forms of storing electric power right?

And don't come now with some efficiency or expense issues, because they are also true for fusion. And because the initial energy harvested is free i do not care about how efficient my battery is.

It is just a matter of will to do it, nothing else. Even if they manage to build fusion reactors, i highly doubt they gonna let us have our own fusion powered cars/homes.

Try to be so optimistic about solar after living above 60 degrees latitude. Also, who's this mystical 'they' who are going to invent and control fusion devices?

[Kryten]

Also, who's this mystical 'they' who are going to invent and control fusion devices?

Given 'they' are the persons preventing people having fusion reactors in their cars, I'm going to guess it's 'everybody with the slightest lick of sense'.

[Guest]

Try to be so optimistic about solar after living above 60 degrees latitude. Also, who's this mystical 'they' who are going to invent and control fusion devices?

That, and check out the solar panel efficiency. This isn't KSP, solar panels are ridiculously inefficient, and solar thermal is only a little better. If you plated the roof of a single, modern house with solar panels, you couldn't supply enough power to sustain it. Solar panels can be small and light, but produce little power per surface area and are expensive. Which is why they're good for calculators, garden lights and spacecraft. Just take a look at ISS solar wings, they're the largest, most prominent part of the station, yet the crew is just 6 people. Most houses have that many inhabitants, but don't have nearly the surface area the ISS has. Also, ISS is well insulated by vacuum, power loses in a normal house are a few orders of magnitude greater. Solar power on Earth is a road to ruin, there simply isn't enough surface area available to power the entire planet.

[m4v]

Try to be so optimistic about solar after living above 60 degrees latitude.

Solar isn't the only renewable energy source, there's wind, geothermal, etc. Even so you still can use solar panels, you will have to put them in a more vertical angle and a lot more of them, so unless you really don't have any land to spare is not much of an issue as solar panels are only getting cheaper and most of the cost goes to the inverter and batteries. IMO a much more practical and realistic idea than waiting for the mythical fusion unicorn.

That, and check out the solar panel efficiency. This isn't KSP, solar panels are ridiculously inefficient.

What do you mean by efficiency? because cars and nuclear power plants aren't terribly efficient either (courtesy of the Carnot cycle) and they're widely used. Solar panel's efficiency isn't an issue when you can put as many as you want, besides cells that are 40% efficient in laboratory already exist, try to find an efficient fusion reactor.

Edited May 21, 2014 by m4v

[rtxoff]

That, and check out the solar panel efficiency. This isn't KSP, solar panels are ridiculously inefficient, and solar thermal is only a little better. If you plated the roof of a single, modern house with solar panels, you couldn't supply enough power to sustain it. Solar panels can be small and light, but produce little power per surface area and are expensive. Which is why they're good for calculators, garden lights and spacecraft. Just take a look at ISS solar wings, they're the largest, most prominent part of the station, yet the crew is just 6 people. Most houses have that many inhabitants, but don't have nearly the surface area the ISS has. Also, ISS is well insulated by vacuum, power loses in a normal house are a few orders of magnitude greater. Solar power on Earth is a road to ruin, there simply isn't enough surface area available to power the entire planet.

Please inform yourself regarding this matter, 20% efficiency is nothing unusual for a solar cell nowadays. 30% cells are already in production but expensive. Scientists already developed 45% and more cells which are already proofed to work.86% is the theorethical limit. On an area of 1m² sun is radiating 1000W of energy. If u have 1m² with 20%efficiency you can produce 200W with that. If your roof is 10mx10m you can have 100m² of cells producing 20.000W. And this is not enough for operating a normal household? I get it that you do not have sunshine the whole day. But cut this number to 1/4 you still come to 5000W which is still enough for the average household. And this is only calculated if u use 5000W all the time which most people don't. I get it also that the citys won't be able to produce enough from the roofs, but companys can do that for them by building solar power plants somewhere else. At least it won't be worse than it is right now with fossil fuels. Sorry where there is a will there is also an way. But we humans are what we are, doomed to destroy our selves. At least let's stop excusing things and face reality. We can do it, but we won't.

Also someone calculated that a solar power plant big as the desert Sahara could produce enough energy for the whole planet. So the argument there is not enough surface area does not count too.

[phoenix_ca]

Fusion power still has some hope. Maybe these guys are on to something. Maybe they aren't. But if they are, people would build those reactors. The cost savings on fuel and maintenance would be massive compared to a fission reactor. They are genuinely close to making it work. And a few hundred thousand dollars per reactor isn't a lot to pay for energy independence.

Edited May 21, 2014 by phoenix_ca

[KNSA Scientist]

Also someone calculated that a solar power plant big as the desert Sahara could produce enough energy for the whole planet. So the argument there is not enough surface area does not count too.

And who is going to work at that power plant? And what about the fact that the Sahara isn't flat? What about the fact that it isn't practical to build a gigantic solar array that can power the whole world if it is crazily expensive, unreliable, and inefficient? We would be better off making a gigantic nuclear plant, which could be a lot smaller and more reliable. (Also, I mean weather and night-time when I say reliable.)

[SargeRho]

"Still has some hope"? There has never been MORE hope for Fusion Reactors than today. Specially with ITER being built.

[m4v]

And who is going to work at that power plant? And what about the fact that the Sahara isn't flat? What about the fact that it isn't practical to build a gigantic solar array that can power the whole world if it is crazily expensive, unreliable, and inefficient? We would be better off making a gigantic nuclear plant, which could be a lot smaller and more reliable. (Also, I mean weather and night-time when I say reliable.)

What about the fact that the sahara power plant was just an illustrative example and not really the only place where you can build one.

[rtxoff]

Fusion power still has some hope. Maybe these guys are on to something. Maybe they aren't. But if they are, people would build those reactors. The cost savings on fuel and maintenance would be massive compared to a fission reactor. They are genuinely close to making it work. And a few hundred thousand dollars per reactor isn't a lot to pay for energy independence.

looks interesting, will have a closer look tomorow

maybe they are really on to something

[lajoswinkler]

Well i tell you again, we have already free energy, just look in the sky, our sun. We have the tech to use it. We have also the manpower. Are we going to do it because of that? Why do you think if they manage to make usable fusion reactors the world will change? I tell you, nobody is going to built a fusion power plant if he won't earn money with it.

Do you know how the law in my country is? It is forbidden for me to have my own solar plant on the roof if i am not feeding in the power that MY plant produces into the official grid.

Just check the law you folks have in your countries and you know from which direction the wind blows.

I don't get you "solar people". You think the Sun is "free"? Nothing is free. Panels cost. A lot. In most cases they're not economically viable because of unreliable weather, and they can not be used as a base load. Whatever you hear, it's a myth. They can not be used as a base load. Period.

Additionaly, photovoltaic energy is expensive, pretty dirty (considering total life cycle - panel production is extremely messy per yielded kWh) and unreliable.

One of the reasons why there are restrictive laws about it is to avoid destabilizing the grid. This is not a simple battery circuit we're talking about. National power systems are a mess that has to be monitored 24/7. You need a stable base load and systems for smooth and rough oscillations. People study these things hard. It's not some dumbass pressing two buttons.

BTW we already use a lot of solar energy. Agriculture. Gigajoules of energy converted into chemical energy of the organic compounds. Drying stuff. Evaporating. Sterilization. Synthesis of vitamin D. Heating and lightning homes. Powering hydroelectric plants (Sun causes rain).

Edited May 22, 2014 by lajoswinkler

[m4v]

I don't get the "fusion people", solar energy is working now, fusion will not for the next 50 years (if you are optimistic, with alcohol-induced optimism).

I don't get you "solar people". You think the Sun is "free"? Nothing is free. Panels cost. A lot.

A solar panel will recover the energy that was needed to produce it in one or two years, depending of where you install it, and will have an expected lifespan of 40 years and possibly more, warranties are usually for 20-25 years. Honestly I don't know from where you get that they are dirty and expensive.

[phoenix_ca]

Solar power is not economically viable in areas that are at high latitudes. In some areas where rain is common (e.g. the UK or British Columbia's southern mainland), solar power is patently absurd. Building the power plant a long distance away (e.g. hundreds and hundreds of miles) only makes sense if you can produce absolutely ludicrous amounts of power, or you've got room-temperature superconductors handy. Solar power can't really produce the former with any sort of ease, and the latter doesn't exist (yet).

It has niche uses, sure. But there is no getting around the problem that it shuts-down for half the day or more, and is subject to the whims of the weather, just as wind power (unless it's placed at sea).

And as for fusion, not really. If you read the paper from the group I linked earlier, you'd see that it really might just be around the corner.

[robertsteinhaus]

There is a practical form of inertial confinement fusion that could be built today that requires no additional engineering or physics breakthroughs and produces net energy. It is not necessary to wait ~50 years for commercial tokamaks or Laser Fusion power plants to become commercial reality.

It may be worthwhile remembering that, at the dawn of the nuclear age in 1952, an inertial confinement fusion experiment that used nuclear fission to produce the conditions for nuclear fusion called Ivy Mike not only produced net energy (more energy out of the fusion experiment than the energy required to operate the fusion experiment) but achieved a fusion gain factor of Q>=100,000.

Ivy Mike achieved net energy and Q>=100,000 using the D-D fusion reaction.

Note: No other non-military pure fusion experiment in the world has achieved a fusion gain factor Q>1 at any time, even for milliseconds, in the last 60 years.

Inertial Confinement Fusion reactors that use nuclear fission to reliably create the conditions for Deuterium-Deuterium (D-D) fusion can be built today. The nuclear waste produced from Deuterium-Deuterium fusion is ultimately just non-radioactive helium (D-D fusion also produces Tritium which is a fusion fuel that is relatively short half-life [12.32 years] and is moderately radioactive. A D-D fusion reactor can burn in place the Tritium it generates, producing additional energy via a D-T fusion reaction, and end up only producing non-radioactive helium, as its nuclear waste). This system is currently being evaluated for development and funding by the California Energy Commission (proposal CEC TN-72616).

The current pure fusion CEC TN-72616 proposal is a lot like classic two stage thermonuclear weapon designs that enjoyed early success in military applications. To produce practical fusion technology that can have an impact in less than 10 years, it is important to try to stay close to ideas that have a track record and have shown their value. The current (CEC TN-72616) pure inertial confinement hybrid D-T/D-D fusion design uses a staged design target that allows a minimum amount of Tritium in a D-T capsule to ignite a much larger amount of pressurized deuterium cryo-liquid held in a long thin pressurized cylinder. The D-T initiator or "sparkplug" is tiny: only 170 microgram of D-T in a spherical fusion capsule which is ignited by the fusion driver. The D-T initiator in turn is used to initiate a detonation wave of in the long thin pressurized cylinder of cryogenic liquid Deuterium (D-D fusion). The majority of the energy produced by the hybrid staged small fusion device is from cheap, sustainable, deuterium D-D fusion. The two stage CEC TN-72616 minimizes both the amount of tritium that has to be produced and stored to make fusion targets and also makes possible a tunable yield – conveniently adjusted to best economic size just by changing the length of the pressurized cryo-deuterium cylinder. The current CEC TN-72616 concept should sustainably produce the tritium needed shot to shot by collecting unburned tritium left in the reactor cavity from the last fusion mini-explosion. Inexpensive operation should be obtainable without requiring Lithium to breed tritium: using instead the recovered unburned tritium remnants of D-D fusion available after each shot to provide the tritium needed for future shots as the fusion reactor operates.

Staying pure fusion with no fission initiator should help reduce regulatory obstacles and allow this hybrid fusion concept to be potentially used even in the 13 states that now have laws against building new reactors until an NRC approved approach to waste handling and storage is identified.

A hybrid fusion reactor based on TN-72616 technology ignites on average one 250 GJ yield fusion device every minute - this does not leave a lot of time to pump down the reactor cavity (cylinder 11 meters diameter x 50 meters long) and prep the system for the next fusion burst.

ICF Fusion reactor (proposal TN-72616) – http://bit.ly/1fTRJWY

TN-72616 pure fusion MSR hybrid reactor proposal is based on concepts first proposed by Professor Friedwardt Winterberg and Dr. Ralph Moir -

“Inertial Confinement Fusion Using Only Deuteriumâ€Â

http://home.comcast.net/~aeropharoh/Winterberg_ICF_deuterium.pdf

Dr. Ralph Moir “PACER Revisited†- http://www.ralphmoir.com/pacer/

Energy Longer than the earth has existed or the Sun will shine - http://goo.gl/XL534

Documents relating to PACER fusion - http://goo.gl/ZKGuQ

[Seret]

Solar power is not economically viable in areas that are at high latitudes. In some areas where rain is common (e.g. the UK or British Columbia's southern mainland), solar power is patently absurd.

Well, this is getting quite OT, but you might be surprised how much output you get from PV in the UK. Typical output is about 800kWh per kWp for an off-the-shelf PV system here. At current electricity prices that means over a 25 year lifespan it'll earn about £2800 per kWp, which is less than what you're currently paying (I've assumed electricity prices rise and the discount rate about even out for simplicity). As panels and inverters come down that equation will tip even further into profit, and that's before you start adding in the money you get from Feed-In Tariffs, which is substantial. The fact that you're starting to see sizeable solar parks being constructed by energy businesses shows that they're definitely not uneconomic. They're actually currently at or near grid parity in the UK.

A solar panel will recover the energy that was needed to produce it in one or two years

That's a little optimistic. Electronics grade silicon pays back it's embodied energy in about 8-10 years. It doesn't really matter if it's poly- or mono-crystalline, the former has lower embodied energy but is also less efficient so it pretty much evens out.

You are however correct that lifetimes are very long and reliability is high. Failures of panels over 20-30 year timescales have been shown to be very low (around 5%) and your 40-year life isn't unreasonable. The weak part of a PV array is the power electronics, these last about 5-10 years, but these represent only a tiny fraction of the array's embodied energy anyway.

Edited May 22, 2014 by Seret

[Winter Man]

What about the fact that the sahara power plant was just an illustrative example and not really the only place where you can build one.

What about the fact that it's also the 'best case' scenario for a giant solar plant? It's the only equatorial desert, the best place for a solar plant, but it's still economically nonviable.

[peadar1987]

I went to crunch some numbers on solar power, but found this on wiki, which does a much better job of illustrating it:

It's a map of the area of solar farms that would be needed to produce all of earth's power (not just electrical), assuming current efficiencies (about 8%), and allowing for cloud cover/non-equatorial insolation.

http://en.wikipedia.org/wiki/File:Solar_land_area.png

Add wind, wave and tidal for higher latitudes, and geothermal where practical, smooth out the variation in production either by using pumped storage, flywheels, hydrogen production, or a power supply capable of smoothing out its own output, like solar thermal using a eutectic salt as its working fluid (this holds enough heat to actually keep generating power at a decent rate during the night, when demand is less anyway).

It's not impossible, or even that hard.

[Seret]

This one is really good for calculating the output of a single installation anywhere in Europe or Africa:

PVGIS