Status on alternative energy

Factual Questions
1

Mrs Cad and I were discussing alternate energy sources. It started out that for the price of 5 wind turbines suplimented by solar and flywheel storage and a self-installed geothermal heatsink and heatpump, our family of 3 could be completely off the grid.

Then the discussion started about the national level. I advocated having wind farms 3 miles off shore along with nuclear plants and opening up Yucca Mountain. She pointed out that nuclear waste is horrible and that we should look at solar power in the Sonoran Desert. I told her that solar panels are poisonous in their own right and inefficient at producing electricity.

Truth be told, I’m not really sure how alternative method would impact our national energy needs. I don’t want this to degrade into a debate but rather facts like:
10 square miles of solar panels would contribute 1% of our energy needs. It would cost about $1.5 billion to build but would produce 6 lbs of cadmium to dispose of in 20-30 years. Minimal carbon footprint. (I just made up those numbers)
Of course there wll be a little debate on the unintended consequences (like Yucca Mtn.) but let’s try to keep this out of GD as long as we can.

For alternative energy sources, I guess anything other than coal/oil or hydroelectric is eligible, so biofuels, nuclear, geothermal, wind, anything else we can think of is open for discussion.

2

At present, solar just plain Doesn’t Work as a power source, no matter how many square miles of desert you cover. It costs a lot of energy to make a solar panel, enough that it would take over a decade for the panel to get that energy back. The problem is that most solar panels don’t last that long. They’re good for satellites, since a panel weighs a lot less than the equivalent battery (and in space engineering, weight is everything), but they’re still basically doing a battery’s job (you spend energy to make it, and then get energy out of it). There’s nothing inherent to the laws of physics that says that solar can’t work: Companies are continually working on how to make them cheaper, longer-lasting, and more efficient. Eventually, they will be worthwhile. If you buy them now (when they aren’t yet cost-effective), you’re effectively subsidizing the R&D to make that happen.

3

[QUOTE=Chronos]
At present, solar just plain Doesn’t Work as a power source, no matter how many square miles of desert you cover. It costs a lot of energy to make a solar panel, enough that it would take over a decade for the panel to get that energy back.
[/QUOTE]

These guys say as little as 12 months.

4

[QUOTE=Chronos]
It costs a lot of energy to make a solar panel, enough that it would take over a decade for the panel to get that energy back.
[/QUOTE]
Cite? I’m not saying it is not true, I would just like to see the math on how much fossil fuel energy it takes to make a solar panel, and how much energy it could capture in 10 years.

5

Wikipedia says olde skool cells had a payback period of about 8-11 years, fresh skool ones about 1.5-3.5 years, and new kid ones about 1-1.5 years.

6

Here are some figures I came up with. Feel free to correct them, I only offer them because it is a calculation I did some time ago. Using state of the art photovoltaic cells the power production is 0.315 KW / 17.5 sqft. cite

In 2006 power consumption in the United States was 4,000,000,000 megawatt hours. cite

There are 8760 hours in a year so that comes out to 456621 megawatts.

That is 456621000 kW, so we need 25367833333 sq ft or 909 sq miles of state of the art solar panels to supply the US with all of it’s power needs. That is slightly less than the size of the state of Rhode Island.

Those figures are very favorable to solar power, since it assumes maximum power production at all times including at night. Also it doesn’t take into account the fact that solar panels lose efficiency as they age.

Anybody want to calculate how much this project would cost?

7

Of course ‘photovoltaic’ isn’t the only kind of ‘solar’.

I think there are large arrays of parabolic reflectors that superheat tubes of (?)oil, and convert the heat to electricity.

After some quick googling:
link 1
link 2

8

[QUOTE=WarmNPrickly]
Here are some figures I came up with. Feel free to correct them, I only offer them because it is a calculation I did some time ago. Using state of the art photovoltaic cells the power production is 0.315 KW / 17.5 sqft. cite

In 2006 power consumption in the United States was 4,000,000,000 megawatt hours. cite

There are 8760 hours in a year so that comes out to 456621 megawatts.

That is 456621000 kW, so we need 25367833333 sq ft or 909 sq miles of state of the art solar panels to supply the US with all of it’s power needs. That is slightly less than the size of the state of Rhode Island.

Those figures are very favorable to solar power, since it assumes maximum power production at all times including at night. Also it doesn’t take into account the fact that solar panels lose efficiency as they age.

Anybody want to calculate how much this project would cost?
[/QUOTE]

That’s all very fine and good, as long as you are willing to use electricity only when the sun shines. Electricity has to be used as soon as it’s generated, or you have to have some sort of storage system. Energy is lost when you put it in storage, and more is lost when you take it out. And you also have some efficiency losses when you transport that electricity from the former state of Rhode Island to wherever it is you live and work. In terms of area, there would need to be some sort of access between panels, so it’s not unreasonable to assume that you would need road access between rows of panels that would take up as much space as the panels themselves.

So the actual land required would be somewhat greater than the 909 sq mi, but probably not excessively so. The big problem is transmission and storage, and those costs also need to be considered.

As the OP mentioned, there are also other impacts from PV - they use cadmium and indium, but those can be controlled fairly easily during the manufacturing process. They might be a problem once you have to deal with end-of-life issues - disposal and at that scale, more likely recycling. It’s also unclear what would happen if you covered that much land area without accounting for how to capture precipitation. Presumably, this would actually be in some desert location, so the total rainfall would be minimal, but when it comes down, it comes down pretty hard. There is also the issue of cleaning up after dust and pigeon storms.

Other alternatives have other drawbacks. Wind turbines will require a lot of space, and have the same problem with storage requirements. Geothermal either requires heat close to the surface, which is often associated with earthquake prone areas, or will need some pretty deep wells to get to the necessary temperatures. And then how do you keep the stuff hot on its way to the surface? Biomass will also be able to contribute, but overall, it s merely an inefficient means of converting solar energy to chemical energy. Ignoring the corn ethanol debates, now we’re talking about massive agricultural programs to grow energy crops and harvest forests. When those become commodities like corn is now, then we’ll see the same sorts of pressures to overfertilize and run down soil quality. Nuclear has its own well-discussed problems with the waste fuel - storage of the stuff that can’t be recovered and the other issue of weapons proliferation. Wave and tidal energy will work in places, but it’s even more diffuse than straight solar, so it also has its limits in terms of how much can be gathered and concentrated for what we need.

On top of all that, most of these will require additional mining for metals, development and production of lots of batteries, the need to dispose of some interesting materials, and (for nuclear especially) lots of concrete. Systems that take up a lot of space (wind, solar, biomass) will result in some significant impacts on ecosystems, either for the collectors/turbines themselves, or for the transmission lines to get the power to where we need it. I should also mention that we could use hydrogen to store the electricity, but hydrogen is somewhat reactive (see “Hindenburg”) and is also thought to potentially cause problems with the ozone layer if atmospheric concentrations get too high.

Bottom line - you don’t get anything for free. We use lots of coal and oil and not these alternatives for some very good technical reasons, and it will take time and lots of money to move off of coal and oil.

9

You think that covering the state of Rhode Island with solar panels is fine and good? I also specifically stated that the numbers were very favorable to solar power.

All the more reason to get started ASAP, because we are totally screwed if we don’t.

10

[QUOTE=WarmNPrickly]
You think that covering the state of Rhode Island with solar panels is fine and good? I also specifically stated that the numbers were very favorable to solar power.
[/QUOTE]

I have nothing against Rhode Island. I was simply commenting on the back-of-the-envelope analysis. The land area required is substantial, but not overwhelming - that amount of solar panels would end up being distributed over a lot of different locations, so you probably wouldn’t end up with a handful of big solar energy “farms.” My main point is that there are a lot of issues with all the alternative energy sources that people usually don’t consider or realize.

11

I can absolutely guarantee that there is 909 square miles of land in Arizona, Nevada, and New Mexico that no one would mind if you covered with Solar cells. Have you ever driven from Las Vegas to Reno? Six hours of the most jaw-droppingly ugly, barren desert imaginable. I live in the desert, and I find it beautiful, and even I thought that stretch of road could be improved with a nice Solar power plant.

12

Where are you going to get the money materials and manufacturing capacity for such a project? That’s 909 square miles covered solid with state of the art electronics. It is absurd.

13

[QUOTE=WarmNPrickly]
Where are you going to get the money materials and manufacturing capacity for such a project? That’s 909 square miles covered solid with state of the art electronics. It is absurd.
[/QUOTE]

Oh, I don’t know about that. Just look around - how much of the US is paved over or built on? I could see generating that number of Solar modules in a few decades.

14

Your comparing blacktop and pavement to solar cell manufacturing? I’m gonna make a wild ass guess that one of them will scale up a lot easier than the other. You’ll have to work faster than a few decades, since by that time the first cells you made will be useless. Thank goodness they don’t have tornado’s, storms, falling trees in that part of the country. I’m sure there will still be some destructive force of nature requiring you to constantly replace damaged cells.

15

[QUOTE=Chronos]
At present, solar just plain Doesn’t Work as a power source, no matter how many square miles of desert you cover. It costs a lot of energy to make a solar panel, enough that it would take over a decade for the panel to get that energy back. The problem is that most solar panels don’t last that long. They’re good for satellites, since a panel weighs a lot less than the equivalent battery (and in space engineering, weight is everything), but they’re still basically doing a battery’s job (you spend energy to make it, and then get energy out of it). There’s nothing inherent to the laws of physics that says that solar can’t work: Companies are continually working on how to make them cheaper, longer-lasting, and more efficient. Eventually, they will be worthwhile. If you buy them now (when they aren’t yet cost-effective), you’re effectively subsidizing the R&D to make that happen.
[/QUOTE]

Wow, just wow. Cite Cite Cite!

16

I’m not sure the space issue is really the big drawback to solar panels - after all, most residential solar panel owners just stick 'em on their roof, which is otherwise pretty much wasted surface area. They could also be placed wherever awnings or other shade structures are used with no net loss of useable space for other functions - the solar panel’s just above wherever the other function of that space is going on.

Better yet are solar water heaters or steam generators in locations where sunlight is sufficient to run them.

17

If you are thinking that space is the issue, you aren’t understanding the problem. If you go into any solar panel manufacturing facility and ask for 909 square miles of solar panels they will just laugh at you no matter how much money you offer. It can’t be done.

18

[QUOTE=WarmNPrickly]
Your comparing blacktop and pavement to solar cell manufacturing? I’m gonna make a wild ass guess that one of them will scale up a lot easier than the other. You’ll have to work faster than a few decades, since by that time the first cells you made will be useless. Thank goodness they don’t have tornado’s, storms, falling trees in that part of the country. I’m sure there will still be some destructive force of nature requiring you to constantly replace damaged cells.
[/QUOTE]

Firstly, solar cells are not a particularly high-tech product. Especially with thin-film devices, “roll-to-roll” technology is being developed that will make their manufacture much less expensive than current processes. Secondly, current modules are guaranteed for 20-25 years, which means there effective lifespan is much longer than that. This is confirmed by empirical evidence - cells produced in the 1980’s are still working at around 75% efficiency.

19

[QUOTE=WarmNPrickly]
If you are thinking that space is the issue, you aren’t understanding the problem. If you go into any solar panel manufacturing facility and ask for 909 square miles of solar panels they will just laugh at you no matter how much money you offer. It can’t be done.
[/QUOTE]

Wait another decade, there are some major advances underway as we sit at our computers and type. They are seperately developing much more efficient panels and much cheaper, much easier to produce though less efficient panels.

20

[QUOTE=Key Lime Guy]
Of course ‘photovoltaic’ isn’t the only kind of ‘solar’.

I think there are large arrays of parabolic reflectors that superheat tubes of (?)oil, and convert the heat to electricity.
[/QUOTE]
Synthetic mineral or petroleum oil, or molten salts, are typically used as the working fluid. Steam is also sometimes used, but the advantage of denser fluid mediums is they act to retain heat much longer, and can be used as in-loop energy storage rather than having to transfer energy to an independent storage system like a water reservoir or underground pressurized cavern with attendant mechanical loses. The overall thermodynamic efficiency of such a system is better than the losses in PV solar; however, efficacy in terms of footprint is generally lower, meaning that you have to cover more real estate to get as much energy.

[QUOTE=WarmNPrickly]
Where are you going to get the money materials and manufacturing capacity for such a project? That’s 909 square miles covered solid with state of the art electronics. It is absurd.
[/QUOTE]
I could only throw an off-hand guess at the manufacturing, installation, and maintenance cost for a system, but per per kilowatt PV solar compares favorably to nuclear fission if you consider the entire life-cycle cost, including disposal of nuclear fuel processing wastes, disposal or reprocessing of spent nuclear fuel elements, decommissioning and decontamination of nuclear plants, and other regulatory expenses of nuclear power; and this doesn’t even account for the liability costs of remediating a (hopefully) unlikely but catastrophic leak or failure which significantly contaiminates populated or ariable land. (One of the major expenses that brought the Soviet Union to its knees was cleaning up the Chernobyl facility; estimates of actual cost run into the tens of billions of dollars, and that on the limited basis and essentially zero personal liability. Such a catastrophy in a Western nation would have cost hundreds of billions of dollars to remediate.)

Nuclear fission power does have the advantage of having a very compact footprint and being able to produce a large amount of electrical power essentially on demand to meet peak energy needs, unlike solar which produces on an as-available basis. Nuclear plants can also be placed wherever one chooses, provided there is sufficient cooling capacity (i.e. a singificant river or lake) and no major NIMBY objections (good luck with that in any populated area), whereas solar plants are limited by geography and climate.

It should be noted that solar is not limited to reflected solar thermal, either; there are other forms of solar-derived energy, including wind, heated air, et cetera that can also capture a small fraction of the bounty of energy the Sun drenches upon the Earth. However, our ability to access most of this energy is limited by thermodynamics and the efficiency of machines on an everyday scale. Thermal capture mechanisms on a smaller scale may be better able to capture some of this energy but will probably be more efficient at converting it into local chemical potential energy than directly to electricity. Barring some kind of magical Maxwell’s Demon, most of the Sun’s energy is lost into the atmosphere (and eventually radiated away) as random heat.

The status on alternative (i.e. renewable) energy is that it is a very immature field, and in the current and foreseeable state is not ready to completely replace fossil fuel and nuclear fission, although it may provide significant supplement when used judiciously. Another prong of this approach is to reduce the amount of energy demanded for a given application or lifestyle; much of the energy used in heating and cooling, for instance, is applied very inefficiently. Better residential and commercial construction which utilizes passive heating and cooling and effective thermal storage could dramatically reduce energy demands in that venue, albeit at the cost of somewhat greater upfront construction costs and of course the significant effort to revise building codes to permit and encourage this type of construction.

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