Best energy alternatives to stop global warming

[shynung]

Well if we are talking about fusion, why not talk about collect the Sun energy in space? Something that I see promissing if Skylon becomes a reality in the next 10 years.

Uhh, Dyson spheres? That's a really long way away, probably centuries if we're lucky.

[AngelLestat]

duuh.. I am not talking of all the sun energy!! lol.. why people need to be so extreme.

[SargeRho]

I don't think he's talking about Dyson Spheres, rather Geostationary Solar Powerplants that beam the power down via Microwaves.

[shynung]

Looks interesting. But there is still the problem of bringing a solar-power satellite into GEO; bigger and more fragile than the ISS, but in much a farther orbit. That'll be the SLS' problem, I suppose.

Though, I just thought: why not leave the PV panels on the ground, and launch mirrors to GEO instead? The mirrors would simply reflect and focus sunlight into the ground receiving station, where the actual PV panels are.

[SargeRho]

That would also increase Earth's irradiance, contributing to global warming - by how much I don't know. Microwave beamed power wouldn't really contribute to GW.

The mirrors are also the most expensive parts to send up since mirrors are really heavy. Asteroid Mining could make it viable.

[Nibb31]

Well if we are talking about fusion, why not talk about collect the Sun energy in space? Something that I see promissing if Skylon becomes a reality in the next 10 years.

First, Skylon isn't going anywhere in the next 10 years.

Second, if it did work as advertised (which it won't), its payload to LEO is about 7 tons. Its payload to GEO would be abysmal.

Third, even with Skylon and with a lower efficiency rate, it will be cheaper to collect Sun energy on the ground. Trucks are cheaper than SSTO spaceplanes.

Fourth, microwave beaming at that scale is unproven and untested. We don't know anything about the side-effects on wildlife, radio interference, or ionization of the upper atmosphere.

[shynung]

That would also increase Earth's irradiance, contributing to global warming - by how much I don't know. Microwave beamed power wouldn't really contribute to GW.

The mirrors are also the most expensive parts to send up since mirrors are really heavy. Asteroid Mining could make it viable.

I was thinking of a silver-coated polymer material rather than a typical glass mirror. It would have problems holding a consistent focal point, though, if it weren't being held in tension.

^{Also, gigantic GEO mirrors could be used as energy weapons, similar to burning ants with a magnifying glass. Not exactly a good idea, politically speaking.}

[Red Iron Crown]

I was thinking of a silver-coated polymer material rather than a typical glass mirror. It would have problems holding a consistent focal point, though, if it weren't being held in tension.

I'm thinking an array of independently controlled small flat mirrors would work well enough.

[shynung]

I'm thinking an array of independently controlled small flat mirrors would work well enough.

If they're made with glass, it'd still be heavy. Of course, being arrays of small mirrors, building it with more launches seemed more practical.

[Red Iron Crown]

If they're made with glass, it'd still be heavy. Of course, being arrays of small mirrors, building it with more launches seemed more practical.

The coated polymers are great for mass reduction, I was thinking more about the focal point problem.

[AngelLestat]

Yeah, something in that scale is what I would talking about.. but not with mirrors.

PV technology is growing fast, also graphene is the material where all the biggest development budgets are going.

I think that in 10 or 15 years for sure, we can have very thin, very light graphene composite PV sheets with an efficiency of at least 25%

We can carry some rolls of this material (with hundreds of m2 becouse it will be very thin), deploy them in a radial shape configuration so a little spin keep them flat by centrifugal force.

Up there we dont need to worry by day/night cycles (well sometimes would be ecplised by earth), we have 5 times more power/m2.

Then we need to chose how to transmit the power. With a Maser or Laser. The amount of energy that the atmosphere absorb is minimun. Then add the cost of the receiver at earth.

But with skylon + graphene, this will become in a great alternative.

Plus is a lot more compact than the normal PV approach, and we can focus the energy wherever we need it in earth.

[shynung]

Up there we dont need to worry by day/night cycles (well sometimes would be ecplised by earth), we have 5 times more power/m2.

Then we need to chose how to transmit the power. With a Maser or Laser. The amount of energy that the atmosphere absorb is minimun. Then add the cost of the receiver at earth.

I fail to see why would placing a PV panel in GEO would magically increase their power generation density by a factor of 5. Is the atmospheric absorption really that much?

[the_bT]

That would also increase Earth's irradiance, contributing to global warming - by how much I don't know. Microwave beamed power wouldn't really contribute to GW.

The mirrors are also the most expensive parts to send up since mirrors are really heavy. Asteroid Mining could make it viable.

Hm, I have trouble believing that any human made object can reflect enough additional sunlight onto the earth that it would make much of a difference. After all, isn't using a mirror to redirect light onto earth pretty much the same as enlarging the area that is hit by sunlight. Half the surface area of earth is in sunlight at any given time. Even if you pretend the earth was a flat disk and not a sphere you get an area of about 1.28*10^14 m². What kind of mirror can compare to that?

Another thing: Regarding global warming, is it of concern how the energy is beamed down? In the end the energy will be released mostly as heat anyways, will it not?

[SargeRho]

Yes and no. If you reflect sunlight down directly onto PV cells, you get what, 30% efficiency at most? The rest is radiated as heat. But Microwave recievers can convert the vast majority of the beam into electricity.

[Guest]

Nuclear, nuclear, nuclear. And then fusion. The one and only way to actually make a dent in fossil fuel consumption. Neither of the alternative energy sources is particularly efficient, and wind power has a nasty side effect of killing birds and spoiling the landscape. It's also not cheap. In contrast, nuclear is clean and safe. It had what, two failures? One of them was a borderline criminal case of human error combined with this being Soviet Union (in any normal country, the test would've been delayed, not handed off to a bunch of rookies), the other was a natural disaster, which are a problem regardless of what you're running on. Not to mention it was handled quite well, actually, and did less damage than commonly thought. Going nuclear is our only chance of both keeping up with increasing power demands and stopping global warming (as well as plain ol' air pollution). None of the renewables have the power output that we need. If all the money that goes into them went into making safer reactors (and building new ones), we'd probably be much better off by now.

I don't believe orbital solar platforms are ever going to beat nuclear. Really, even with Skylon, the cost is probably going to be rather large. Not to mention the problems of the receiver being obscured by clouds, or the platform going into Earth's shadow. Also, lasers lose coherence over a distance, it'd be though to focus such energy from GEO (and the platform needs to be at GEO for it to work). That's not even mentioning Skylon not being GEO-capable in the first place. This kind of energy is simply too unreliable. So no, solar is good for space stations, not terrestrial power plants.

[AngelLestat]

First, Skylon isn't going anywhere in the next 10 years.

Second, if it did work as advertised (which it won't), its payload to LEO is about 7 tons. Its payload to GEO would be abysmal.

Fourth, microwave beaming at that scale is unproven and untested. We don't know anything about the side-effects on wildlife, radio interference, or ionization of the upper atmosphere.

The first skylon prototype (from what I hear) it would be build in 5 or 6 years. So if that is true, is safe to said that (no manned) comercial use will start in 10 years.

About the payload is not important. As I said, you can have 3000m2 (150x20 roll) in graphene composite PV which would weight no more than 2 or 3 tons.

The long wavelength of the microwave requires a long antenna, and allows power to be beamed through the Earth’s atmosphere, rain or shine, at safe, low intensity levels hardly stronger than the midday sun. Birds and planes wouldn’t notice much of anything flying across their paths.

I fail to see why would placing a PV panel in GEO would magically increase their power generation density by a factor of 5. Is the atmospheric absorption really that much?

Yes and no.

The sun irradiance is 1360W/m2 in space. If you are in geo orbit you would get an anual average of 13000w/m2 (75 min of shadow by day in geo orbit).

But in the surface you had other problems, first due that you have 12hrs of sun you get half of that number, then depending the angle of how irradiance go through the atmosphere, is reduced from 100 to 500 w/m2.

So you end it with a irradiance average of 250w/2 here an earth vs 1300 w/m2.

This is 5,2 times more energy by m2.

So each m2 of PV that you make, worth 5.2 times more in space.

http://www.windows2universe.org/earth/climate/sun_radiation_at_earth.html

http://www.azimuthproject.org/azimuth/show/Solar+radiation

Yes and no. If you reflect sunlight down directly onto PV cells, you get what, 30% efficiency at most? The rest is radiated as heat. But Microwave recievers can convert the vast majority of the beam into electricity.

Yeah that.

------------------------------------------------------------------------

Now lets imagine another case.

Instead place the collector in geo orbit, what if we place them in solar polar orbit at 0,01 Au?

Here at earth the irradiance is 1360w/m2, in mercury we have 9500w/m2, but at 0,01 Au we have 10000 times more energy than in GEO (1au).

This mean 13600000 w/m2, If we have 10 rolls of 20x150=3000m2 x 10= 30000m2 x 13600000 = 408 GW, now lets take an efficiency of 25% = 100GW.

The problem is how we focus the enegy? :S Today laser technology is not enoght to keep the beam narrow, continous and aim. Then we have a security problem becouse it can be used as a weapon (which some countries would love to fund).

But is safe to said, that if some day we deal with those problems, we would have a 70% collector efficiency of 300Gw (full PV graphene to survive the heat with a brayton cycle plus extra radiator).

This can also protect us from any asteroids.

PD: Dragon01: You should read some pages before post. Nuclear is not so great as you think.

Edited June 24, 2014 by AngelLestat

[Seret]

The first skylon prototype (from what I hear) it would be build in 5 or 6 years.

Unlikely. REL themselves stated that their schedule had slipped out to 2021-2022 as of three years ago. So about seven years is the lower bound, with the actual time likely to be somewhat longer. These projects always take longer than anticipated.

So each m2 of PV that you make, worth 5.2 times more in space.

Unfortunately it costs thousands of times more to get it to space than it does to plonk it on the ground. You'll produce far more electricity by spending the same money on ground-mounted PV than shooting it into space. The economic case against space-based PV gets even worse as the price of PV cells comes down (which it has) and the cost of mass to orbit doesn't.

[AngelLestat]

Unlikely. REL themselves stated that their schedule had slipped out to 2021-2022 as of three years ago. So about seven years is the lower bound, with the actual time likely to be somewhat longer. These projects always take longer than anticipated.

We are in 2014, so this is mean 7 or 8 years.. Not very different from my 10 years estimation for the first commercial mission.

Unfortunately it costs thousands of times more to get it to space than it does to plonk it on the ground. You'll produce far more electricity by spending the same money on ground-mounted PV than shooting it into space. The economic case against space-based PV gets even worse as the price of PV cells comes down (which it has) and the cost of mass to orbit doesn't.

The launch cost would drop from £15,000/kg to £650/kg.

You know how much m2 of graphene composite you can have in 1 kg?

Using vapor deposition or other techniques, graphene based PV can be at lot lighter and cheaper (carbon based) than today PV cells.

You need to take into account that you need "rent" the land where you place your solar panels. Land value increase over years, those cost are included in the levelized cost that we saw before, but you need to discount them for space.

Receiver cost does not count either. Becouse it is equal or less to the cost that you would spent in transportation with PV surface.

Right now, it does not worth it.

But in 10 years is a different case.

[the_bT]

Yes and no. If you reflect sunlight down directly onto PV cells, you get what, 30% efficiency at most? The rest is radiated as heat. But Microwave recievers can convert the vast majority of the beam into electricity.

The electricity is then transmitted to some sort of appliance which turns it into heat + work of some sort. You can't get away from the heat. But that is not the driving factor behind global warming so I don't think it's of concern when discussing global warming.

The point is that we need to save emissions because our problem is that heat delivered by the sun is kept by the slightly changed atmosphere instead of being radiated into space. It should not matter in what way the energy is delivered to the surface, the problem is the same I think.

That being said, saving emissions is hard to do if you start by launching several thousand tons into orbit. How much electricity do we have to generate until we get that initial emission investment back? Considering maintenance, do we make emission profit at all?

[Red Iron Crown]

All the talk of theoretical graphite solar panels launched in a theoretical spaceplane using a theoretical beamed power system is nice, but we don't have that kind of time. We need to start transitioning away from fossil fuels now, not in 10 or 20 years. Ground based renewable and nuclear fission are the developed, practical transitional sources of power. If the other stuff becomes practical later, fine, but for now we need proven technologies.

[AngelLestat]

That being said, saving emissions is hard to do if you start by launching several thousand tons into orbit. How much electricity do we have to generate until we get that initial emission investment back? Considering maintenance, do we make emission profit at all?

With my method there is not such thing as "several thousand tons". Maybe a few.

All the talk of theoretical graphite solar panels launched in a theoretical spaceplane using a theoretical beamed power system is nice, but we don't have that kind of time. We need to start transitioning away from fossil fuels now, not in 10 or 20 years. Ground based renewable and nuclear fission are the developed, practical transitional sources of power. If the other stuff becomes practical later, fine, but for now we need proven technologies.

My initial plan is just 10 years away for orbit collector. And I start to talk about this becouse people was discussing fusion which is +30 years away.

[peadar1987]

...and wind power has a nasty side effect of killing birds and spoiling the landscape. It's also not cheap...

Well, efficiency doesn't really matter when your fuel is free.

When you don't have to match your generation capacity with reserves (which is true for low grid penetrations), wind is competitive with pretty much any other form of generation.

And in terms of killing birds, here's an enlightening little graphic:

And an article here:

http://www.bloomberg.com/news/2013-12-06/u-s-eases-turbine-bird-death-rule-as-cats-kill-millions.html

So basically, the best thing for everyone would be to generate our energy by burning cats.

[phoenix_ca]

Maybe we can find a sufficiently plentyful Helium 3 source that doesn't involve processing 150 million tons of moon dust for a kilogram of Helium 3, or mining the Gas Giants. D-Helium 3 fusion produces even more energy, and is aneutronic. It produces 14.7 MeV protons, which can be used directly for power production.

It's not a bad idea, mining the gas giants, but it's certainly a long way off.

If we can make fusion or q-thrusters work as well as a sub-light Acubierre drive, then yeah, it might even become economically viable some day.

Afaik the waste produced by fusion powerplants decays much faster than fission products, so you have to store it for "only" about 100 years so it can be stored in castors like todays waste is, except that you can open it after a reasonable time...

Depends on what fuel you're talking about. If you mean aneutronic processes like p+B11, the time for all the side-reaction products to decay is more on the order of hours. Turn it off, wait eight hours, and enough of the C-13 will be gone that you can walk around and frolick inside the reactor...or you know, perform maintenance on it or something like that...

Eventually everybody will just have to bite the bullet and push through proper long-term storage facilities. I suspect most countries will have to build their own, I can't see many folks being keen to accept everybody else's waste.

Even though fusion plants won't generate the high-level wastes we're stuck with those generated by existing fission plants.

I vote for Canada. Have you seen how much room we have here!? We even have our own desert! And on top of that, we can stick pretty much all of that high-level "waste" from everyone else's reactors into our own, so we'd basically be getting free energy. As a Canadian, I'm totally down for that.

My initial plan is just 10 years away for orbit collector. And I start to talk about this becouse people was discussing fusion which is +30 years away.

That's a rather, misleading estimate. Maybe for a tokamak, sure. A more realistic one would peg it at a decade, assuming all goes well. At least for reaching net energy. Once that's done the rest is pretty much just an engineering issue using current technology.

[lajoswinkler]

Care to comment newest stupid and misleading articles on Germany's "50% power from solar"?

[Elthy]

Germany isnt getting 50% (of its renewables) from solar and will never do that, since wind power takes a much bigger role. So that articles are pointless...