EquALLity wrote:
Perhaps, but then it's also unfair to contribute France's success to nuclear energy when there could be multiple factors.
France's success IS nuclear energy; it's about the percentage of energy they use coming from non-emitting sources.
The success has to be looked at in terms of the public policy and education that made nuclear successful.
Yes, we should also reduce usage, but it's not going to be able to drop much without affecting quality of life. We need to get on better energy sources.
EquALLity wrote:
brimstoneSalad wrote:Used together with nuclear which can kick on when the sun goes down or the wind stops blowing, and in certain situations, solar and wind can be useful. On their own, they're too unreliable.
So you agree that we should try to develop solar and wind energy in addition to nuclear?
I've never disagreed, but they have very limited applications. I don't agree with considering them a potential solution to the current problem; that's a red herring.
Solar is useful for non-grid energy. Like street lights that don't all have to be connected by miles and miles of copper wire. Or trash cans which alert the base when they're full and have to be collected, or even compact the trash in them to limit the number of trips needed.
When you think solar or wind, think non-intensive distributed operations. Stuff that only needs a tiny bit of power, and is all spread out so it'd be a waste to run power lines to all of them. Low wattage activities which can be supplied by an on-site solar panel which eliminates the need for power transmission.
It makes sense to run your home computer and led house lighting off solar and a small (cheap) battery. These are low wattage behaviors, AND they require DC power (make sure to know the difference between AC and DC).
It doesn't make sense to expect to run your heating, air conditioning, your refrigerator, your washing machine, etc. off these power sources. These are power hogs, and they draw too many watts to be reliably supplied by a small solar and battery system (one that could be easily and cheaply installed in most houses).
EquALLity wrote:
Estimates that nuclear energy is going to last a very long time are also based on theoretical future technology and findings.
You're misunderstanding,
The fissile material is there. Current supplies (at the current price) will last X years. Once that's used up, the price will rise a bit, and more supply (at the new price) will open up; like reprocessing fuel, and deeper mines and more anemic ores. At the new price, there will be supply to last for Y years. Then the price will go up a little more, and there will be new sources at that new price (like sea water extraction), and that supply will last for Z years.
Nuclear is currently economically viable. Solar is not.
Nuclear only requires a gradual development of technology to
stay viable. Solar requires an
instantaneous leap in technological development to
become viable.
It's the difference between the prospect of leaping directly to the top of a hundred story building (Solar), and being expected to climb the stairs to the top over the next few hundred years (Nuclear).
We have time to bring the price of technologies like fuel reprocessing and seawater extraction down. We have huge amounts of time to do this. And nuclear is already a viable source for the world's power today based on current supplies that will give us that time.
The same is not true of solar.
IF we had an immediate supply of elementally pure silicon, and it's doping elements, to produce solar panels cheaply and with virtually no energy input (a supply that will gradually run out), then the situation would be a little more similar.
Self-assembling satellites are launched into space, along with reflectors and a microwave or laser power transmitter. Reflectors or inflatable mirrors spread over a vast swath of space, directing solar radiation onto solar panels. These panels convert solar power into either a microwave or a laser, and beam uninterrupted power down to Earth. On Earth, power-receiving stations collect the beam and add it to the electric grid.
The two most commonly discussed designs for SBSP are a large, deeper space microwave transmitting satellite and a smaller, nearer laser transmitting satellite.
http://energy.gov/articles/space-based-solar-power
I'm familiar with the science fiction. I don't know who wrote that, but I guess I'll have to tear it to pieces.
Like solar power, lasers also don't work on a cloudy day, but it's much, MUCH more expensive.
Did you look at the pie in the sky price estimates? 1 to 10 MW for 500 million to a billion dollars? (these seem to be ridiculous low-ball estimates, by the way)
Residential systems today are around $5 per watt. So such a system is ten times more expensive (at the best case, if it delivers 10 MW for 500 million dollars) than just putting solar panels on rooftops. There's no reason or advantage to putting these things in space. I would say this was yellow journalism to sell copy, but this is a government web page... I think it's just an example of government waste coming from enthusiasm generated around a cool sounding idea with no practical viability. Or maybe NASA clamoring for funding and trying to stay relevant. This could very well be fueled by bias.
Remember Solar Freaking Roadways?
https://www.youtube.com/watch?v=H901KdXgHs4
Government bought into that nonsense too.
Microwave based systems are even more risky, and more expensive.
While they don't suffer as much from atmosphere, do you think the oil industry isn't going to launch the same fear mongering campaign against this that they did against nuclear?
Literal beams of radiation from space!
We have perfectly viable options for power here on Earth that are well within the scope of current technology and affordable today.
This is intriguing for science fiction, but appears to be far outside the scope of current technology, and may never be financially viable.
There's also an important con the author left out of the graphic: thermodynamic efficiency of lasers is not very high, as is the thermodynamic efficiency of solar panels even lower, we also have to consider the thermodynamic efficiency of conversion on the ground.
THREE times you have to change the form of power.
Sun -> electricty: 25% efficiency (which is a margin above the current record holder, and may never be passed for all we know)
Electricity -> laser (let's say an infrared diode): 70% (again, above anything I've found by a large margin).
Laser -> Electricity: 50% (best case for a solar cell, which are more efficient for lasers)
That's 8.75% efficient for a laser.
For microwave it's slightly better, at 13.5% total.
What does inefficiency mean?
If you want to get 10,000 MW of electricity on the ground, that means you have 18,571 MW of waste heat in your laser in space.
That's 18,571,000,000 joules of heat building up every second.
If I calculated this correctly, that's the equivalent of four tons of TNT exploding every second.
Something kind of like this:
https://www.youtube.com/watch?v=FAYVMXYYAp4
Every second.
Where does that heat go? Remember that space is a vacuum; it's a perfect insulator (like a vacuum thermos). Things can only cool by radiative cooling, which is extremely slow and inefficient.
You could certainly build such a satellite, but trying to run it and generate a laser would melt it. Such a device would require an incredible cooling system, and I don't think these people have accounted for the difficulty of such an endeavor. Or they've ignored it or waved it off for political reasons because they don't want to argue themselves out of funding for superfluous technology.
To put this into perspective, check out the ISS:
https://en.wikipedia.org/wiki/Electrical_system_of_the_International_Space_Station
It maxes out at about 120 kW. A pretty trivial amount of power. And even that amount was a monumental challenge for cooling.
This is 154,758 times larger.
Let that sink in a little bit.
And that's not the half of it (literally). I didn't even get into the inefficiency of the solar panels themselves. That multiplies the amount of heat that needs to be dissipated by over four times (25% efficient), because they're talking about using mirrors to concentrate power on the solar cells (which means, unlike the ISS, the solar cells themselves aren't able to act as radiators of at least some of the excess heat).
You could operate at a higher temperature, but then you get into a negative feedback loop, because the higher temperature you operate at, the lower your efficiency, so the more heat you're producing for the same power output.
When you reach sizes like these, you start running into serious limitations of radiators and require larger and larger installations and active cooling systems. We'd probably be looking at something like a death-star. All for the sake of a measly 10,000 MW of power. You will need to build a small moon.
Bear in mind that these are just back of the envelope calculations, but I'm just trying to give you an understanding that unless you get into the physics of something and show where all of the energy is going, the efficiency of each step, AND where the waste heat is going, you can't really say something is "possible".
EquALLity wrote:
As for the shadow stuff, that's not true-
In space the sun is always shining, the tilt of the Earth doesn't prevent the collection of power and there’s no atmosphere to reduce the intensity of the sun’s rays.
This is also incorrect. The sun is not shining in the shadow of the Earth, which can be seen as far as the moon quite clearly. This is most relevant for a space elevator style solar collector.
The satellite has to be positioned to beam energy to the ground, night and day. This may not be trivial to avoid Earth's very large shadow.
EquALLity wrote:
Nuclear energy is apparently supported by most people, but over a third of Americans believe it is unsafe.
It's something we have to tackle. We have a similar problem with adoption of veganism. We have to use evidence against the myths and ignorance.
Our job is education foremost.
EquALLity wrote:
I agree, but I think we should also work to develop other forms of renewable technology.
Why?
I'm OK with continual research into fusion as an academic project, but that may never yield positive energy output, and may never be financially viable.
When we put money into these things it's a gamble, and nuclear is not. It's already a viable solution.
EquALLity wrote:
Because they're also useful to combating climate change, and they have more support than nuclear energy.
Eating Organic meat has more support than veganism, but it's not useful, and even counterproductive.
Talking about solar for grid power is a distraction. The technology we already have for solar (like rooftop solar, and solar water heaters) is great. You can buy and install these systems today, and they aren't going to improve much. We just need to adopt the currently available technology where we can, develop viable innovations with low power consumption (like solar trash cans and lighting that makes sense) and focus on nuclear for grid power.
EquALLity wrote:
Once they're built, they don't require any additional fossil fuel energy to be supported, and soon outweigh the fossil fuels used to produce them. It's a worthy investment.
Don't nuclear plants require fossil fuels to be built as well?
It's an issue of Energy Returned On Energy Invested.
EquALLity wrote:
IMO the problem isn't fossil fuels being used to produce solar and wind technology; it's that intermittency is supplemented with fossil fuels (primarily natural gas, apparently).
And the cost. And the environmental and health impacts.
