Solar Economy

[Threadkiller]

In the past in this forum there have been a few threads on solar energy. The two that jump out are:
Whatever happened to Solar Power? (http://boards.straightdope.com/sdmb/showthread.php?threadid=40310)
Whatever happened to affordable solar electrical power? (http://boards.straightdope.com/sdmb/showthread.php?threadid=34401)

The consensus of these threads was that currently solar just doesn't cut it as a viable power source-the production costs are too high and the power density of sunlight is too low for reasonable generation.

Recently the Green Party (http://www.greenparty.org) has been making news by calling for drastic reductions in greenhouse gas emissions. On their website they post their energy objectives: (http://www.greenparty.org/program/envirestore.html)

Phase Out of Fossil Fuels in 50 Years…Phase In 100% Renewable Energy Sources in 50 Years: Solar energy income from the sun can provide all the energy we need for a decent standard of living using technologies we already have. Development of renewable energy sources should receive massive public investment…Reject Nuclear Power

Everyone seems to say that solar isn't viable yet. What are the Greens talking about when they mention the "technologies we already have?" Of course the statement above contains the "decent standard of living" caveat. What would be the standard of living be with a solar economy? Even with massive conservation (which heaven knows we certainly can do better) I have a hard time seeing the Green Party as being more than a bit pie-in-the-sky on this one.

[Lumpy]

I agree with your doubts. Consider solar cells for example. They supply electricity at a greater cost than fossil fuels. But the solar-cell factory itself is run on energy supplied by coal and oil plants. If the solar-cell factory itself had to run on solar cells, how much would they cost? A bundle, I'd imagine.

I strongly suspect that the Greens have in mind something that might be disparagingly called "eco-Socialism"; no private automobiles, high density urban centers with no suburbs, a rollback of America's consumer culture, etc.

[Una Persson]

Originally posted by Lumpy
I strongly suspect that the Greens have in mind something that might be disparagingly called "eco-Socialism"; no private automobiles, high density urban centers with no suburbs, a rollback of America's consumer culture, etc.

Ding ding ding! We have a winner, folks!

Not referring directly to the Green Party's official platform, many members of the Party who I have contact with see the following scenario:

Arcologies of high-tech "ultra green" businesses (I suppose they mean Starbuck's and Apple PCs), limited shopping, hydroponics and greenhouses, and housing units for the droids (err...people) within them. Square footage of space limited to 300 square feet per person (no, I am serious). Banning of lawns and all private greenspaces. Passing of draconian laws to monitor people for environmental and energy compliance at all times. Nationalization of farms, by military force if necessary. Banning of all biotech research (which is so ironic I don't even need to discuss it). Elimination of the Space program, the military, airlines. Yes, that's right - banning of all airlines. Dynamiting coal mines, oil and gas wells, etc. Banning possesion of all internal combustion engines of any sort. Banning of animals as pets. Population controls that require applying for a permit to have children, a limit of 1 to 2 children per lifetime, and mandatory sterilization for anyone who does not get a permit by age 21.

The future that they talk about is chilling and frightening to me. One person I went to school with gave a terrifying little speech once about how he dreams of the day when people are forced from their homes by Federal troops, relocated into nice, safe, clean apartment housing units, and their lawns and homes are razed to make new growth forest. And all cars are collected by those same Federal troops, and crushed and landfilled so that we "never make that mistake again."

Of course, this is two different things. Will going 100% solar and renewable force people into this sort of existance? Not at all. But the people who clamor for one often are the same who have the other items in mind, IME. They don't understand, or can't fathom, what a reduced standard of living actually means.

I would hazard that something like the Green Party proposes (not what I mentioned above, BTW) would result in a fundamental, catastrophic change in our society, and may result in destabilization and violent revolution. Anyone in the US who thinks they can easily deal with a reduced standard of living without too many problems - visit a third world country for a few weeks. One where electricity and energy is a luxury. Get used to not having a car, McDonalds, running water, air conditioning or heat, cold beer, hot water, toilet paper, etc - like rural Pakistan.

And to think - I get bothered by just not having Diet Coke.

I would do things a bit differently. I would encourage conservation by any way possible to reduce energy needs by 20% from the current 2001 levels in 20 years. I would raise the CAFE to 35 mpg, but not place bans on any type of car or engine. Reduce what I consider to be the exhorbitant amount of street and public area lighting that is in place right now. Pass Federal Laws exempting homeowners from Homes Association and zoning restrictions if they wish to let their lawns grow higher - say to 5 or 6 inches (we did a study once that concluded an enormous savings of gasoline and reduction of hydrocarbons if everyone in the US could have a 5-inch lawn, rather than a 3 or even 4-inch lawn), or if they wish to plant trees and shrubs. Remove restrictions in place to allow more biomass and nuclear power production. Put some cubic buttloads of tax money into research (not subsidies) of fusion, solar, wind, and super-high yield genetically engineered biomass fuel crops.

But then, I'm not running for any office. Sigh.

[Britt]

Anthracite says

we did a study once that concluded an enormous savings of gasoline and reduction of hydrocarbons if everyone in the US could have a 5-inch lawn, rather than a 3 or even 4-inch lawn

An enormous saving in gasoline from an extra few inches of lawn (due to less mowing?), this rather surprises me I would be very interested in any publicly available studies on this.

Put some cubic buttloads of tax money into research (not subsidies) of fusion, solar, wind, and super-high yield genetically engineered biomass fuel crops.

Genetically engineered biomass fuel crops, are really another form of solar generation, with a couple of extra steeps involved to loss energy in, not to mention that it still leaves you requiring a CO2 fixing solution to balance the carbon cycle. I must admit our current solar energy collection systems are not exactly efficient when scaled up, but I personally would rather avoid further issues with the carbon cycle if we can.
Wind power is primarily, another conversion system for solar energy but at least it avoids the chemical conversions required in biomass systems and while it is a very inefficient harness for the energy, the scale would be hard to replicate.
I would also point out that hydro-electrical systems are also a solar powered conversion system. Although these systems have already been heavily researched and implemented, work on the long-term effects of water levels and the management of this, could allow for a further expansion in this type of power generation.
Slightly off topic there is also tidal energy as another possible alternative for the renewable generation of energy that could do with some extra funding to improve its economic viability.

In the mean time conservation is defiantly the best bet.
[Public Notice]
Remember that most devices with a display (e.g. video recorders, TVs, set top boxes, etc) draw power continuously unless disconnected from a power source.
[/Public Notice]


Arcologies of high-tech "ultra green" businesses ...

I like most Utopians rely on being in power and thus less inhibited by the rules set in place for the common good. How else can we effectively monitor everyone if we can't get from place to place quickly? Its all for your own good really! :)

[Una Persson]

Originally posted by Britt
Anthracite says

we did a study once that concluded an enormous savings of gasoline and reduction of hydrocarbons if everyone in the US could have a 5-inch lawn, rather than a 3 or even 4-inch lawn

An enormous saving in gasoline from an extra few inches of lawn (due to less mowing?), this rather surprises me I would be very interested in any publicly available studies on this.

Well, the only one I know of was the one I was given to read, and it was proprietary.

The real problem is my definition of "enormous", which I see was misleading in this context. It made the following assumptions of:

- A baseline of all corporate and residential lawns being trimmed to a 3 inch height upon reaching a 5 inch height (4 inch average height).

- A new standard of being trimmed to a 3 inch height upon reaching a 7 inch height (5 inch average height)

- Assumed a baseline 2.5 mows per lawn in April and May, 2/month in June - September, and one in October and one in March.

- Assumed a new value of 1.5 mows per lawn in April and Maw, 1/month in June - September, none in October and March.

(net savings - 8 mows/year)

- Assumed average homeowner has 0.7 gallon used per mow.

- Assumed 50 million lawns mowed in this fashion (lawn equivalents - included corporate frontage)

Thus, ended up with a savings of 8*0.7*50,000,000 = 280,000,000 gallons of gasoline a year - more than a quarter billion a year.

Of course, I may be misremembering numbers here...but the amount of fuel used for lawn mowing is pretty substantial in some cities. Here in Johnson County, it is not unusual at all to find most of my co-workers mowing once/week from April-June, and twice/month until nearly Winter. This does not account for gas weedeater usage either.

[Una Persson]

Originally posted by Britt
[Public Notice]
Remember that most devices with a display (e.g. video recorders, TVs, set top boxes, etc) draw power continuously unless disconnected from a power source.
[/Public Notice]

Don't forget any transformers left plugged into the outlets, even if the device being powered is completely off. You can test this by plugging your Walkman into the outlet while off, then feeling the heat after an hour or so coming from the power converter. That heat is from the losses of the AC current in the transformer coils - even with the device completely off.

These losses are small, but there are a lot of them. I know of no "official" estimates on a National scale, only a WAG that they may amount to "1 to 3 percent" of the overall electrical usage of the US.

How much is 1 to 3 percent worth? Ask California, where a 1.5% margin triggers a Stage 3 alert...

[LateComer]

Good info, Anthracite. I'm a new home owner (September, 2000) and will try letting my lawn go a little higher next summer. I may need to, as the previous owner didn't do a good job at upkeep. I know not to get it too high. When we bought the house it took me 3 evenings to mow the first time the grass had been let go so long. It was too long to mulch and the bag would fill up after maybe 200 linear feet of mowing.

Question: I once saw a guy on C-Span talking about his book "Hard Green" which was a defense of fossil fuels mostly. (He did advocate Nuclear, the irony of the demonification of which by many environmental groups is surely self-evident). His whole argument centered around the idea of preserving Green space. This is what environmentalists want, is it not? He argued that drilling for oil and mining coal are 3-dimensional resources (You drill a relatively small hole, destroying a relatively small piece of land and get a relatively large amount of oil) whereas solar is 2-dimensional and therefore requiring much more land to operate.

One stat that stood out in my mind was something like this: "Even with a 10 times improvement in solar efficiency, it would take an array of solar cells 7 times the area of Manhattan to power Manhattan."

Whadda ya think of those numbers? (The 10 times may be wrong, but I distinctly remember the 7 times number. Give me a break! It's on my reading list!)

[Britt]

Thanks for the clarification, now for a my next project all I have to do is convince two random populations to follow my directions when it comes to mowing lawns and then measure the relative fuel usage. Now where did those grant application forms go? Oh well in the meantime you could always look into our solution and use sheep.

[manhattan]

Heck, just get one group to use those old push-mowers. It's not too bad as long as the yard is under 1/4 acre or so, and it provides a good workout in addition to saving a lot of gas (and the accompanying emissions, not inconsiderable when one thinks about how inefficient those lawn mower engines are).

Just don't give the 5" idea to the golf courses! I can barely get out of the rough now! If they go to championship length on the roughs for normal play, it'll be war I tell you!

[hibernicus]

Originally posted by Britt
Genetically engineered biomass fuel crops, are really another form of solar generation, with a couple of extra steeps involved to loss energy in, not to mention that it still leaves you requiring a CO2 fixing solution to balance the carbon cycle. I must admit our current solar energy collection systems are not exactly efficient when scaled up, but I personally would rather avoid further issues with the carbon cycle if we can.


Why does biomass fuel introduce a need to "balance the carbon cycle"? If you grow a crop and burn it, it releases the same amount of carbon during combustion as was fixed during growth. A little less, if there are roots and stumps left behind. Are you referring to CO2 emissions from transport of the fuel, or other secondary effects?

On the subject of lawns, another big climate change issue is anaerobic decomposition of lawn cuttings; methane is a much more potent greenhouse gas than CO2.

[Britt]

hibernicus says

Why does biomass fuel introduce a need to "balance the carbon cycle"? If you grow a crop and burn it, it releases the same amount of carbon during combustion as was fixed during growth.

The biggest problem with this is time scales, it takes a lot long for a plant to fix the CO2 from the air than it does for combustion to re-introduce it.
This means that to balance the cycle you need a total crop size of approximately biomass combusted*(the time taken to grow the biomass/time taken to combust the biomass), in order for the CO2 absorbed per hour to equal the CO2 produced per hour.
This is still a very simplistic picture of the carbon cycle and there are several other factors that affect it. However the total amount of carbon fixing biomass would always need to be much larger than the production biomass to balance the system, and even then there are a couple of other pollutants that tend to arise from the combustion of biomass that need to be taken care of.
See Anthracites post in here (http://boards.straightdope.com/sdmb/showthread.php?threadid=40310) to see what the experts say on this.

[Chronos]

To return to the OP, the claims made by the Green Party are correct, but very misleading. Yes, we could supply all of the nation's current power needs with current solar technology... Just cover all of Arizona with solar panels. Of course, making that many solar panels would itself require significant energy, far over and beyond our current usage levels.

With efficient collectors, solar power would, in fact, be viable, but we don't have them yet. If the Greens want more research money to go towards developing efficient collectors, well, I'm all for that, but until then, it's a bit premature to be setting deadlines for adoption of such techniques.

[pantom]

Fuel cells, anyone? They're on the way...

[Balance]

As much as I love fuel cells, pantom, they're not an answer to this problem. They just rearrange the variables, and improve efficiency in a few places. You still have to make fuel for them somehow, which requires energy from some other source--be it fossil, nuclear, solar, biomass, or what-have-you. Then you have to transport the fuel, which cuts into your efficiency gains a bit.

Barring major advancements in solar or (local) fusion power, I suspect that we're going to be forced to use more fission power. I don't like the idea much, as it produces such nasty by-products, but the fossil fuel supply is limited, and we don't have any other technology efficient enough to take up the slack when the supply dwindles.

[pantom]

I'm not sure I get you. Fuel cells use chemical reactions to create energy, and their main byproduct is water, with a little bit of maybe something else thrown in (I think). So, for solving global warming, I would think they'd be quite useful, as they throw off no CO2. Their much higher efficiency means you're transporting way less fuel than you would otherwise be, meanwhile.
Also, let's not forget rechargeable batteries. Advances are being made every day here as well, and this too will increase the efficiency of the things we use.

[honkytonkwillie]

Originally posted by pantom
...Fuel cells use chemical reactions to create energy, and their main byproduct is water, with a little bit of maybe something else thrown in (I think). So, for solving global warming, I would think they'd be quite useful, as they throw off no CO2.


True, for fuel cells that are fed pure hydrogen, which is way expensive. Most of the fuel used in fuel cells is hydrocarbon in nature; be it propane, natural gas, kerosene, diesel fuel, and sometimes methanol or ethanol.

These things all contain carbon, which result in COX emissions.

The largest operational fuel cell in my vicinity powers the very large US Postal Service facility in my city. It came on line last fall, produces 0.8MW IIRC, and is fueled with diesel.

[honkytonkwillie]

Originally posted by manhattan
Heck, just get one group to use those old push-mowers. It's not too bad as long as the yard is under 1/4 acre or so, and it provides a good workout in addition to saving a lot of gas (and the accompanying emissions, not inconsiderable when one thinks about how inefficient those lawn mower engines are).

I do this. My house is on a 14,000 square foot lot, and it takes about an hour.

[justwannano]

Quote pantom
Also, let's not forget rechargeable batteries. Advances are being made every day here as well, and this too will increase the efficiency of the things we use.

Rechargeable batteries still take power to recharge. There is always some loss so it takes more power to charge them than you receive .
Here is where solar chargers come into use. They do not draw power from the grid.

[Una Persson]

Originally posted by pantom
I'm not sure I get you. Fuel cells use chemical reactions to create energy, and their main byproduct is water, with a little bit of maybe something else thrown in (I think).

As was said before - you are thinking of hydrogen fuel cells only. And where does the hydrogen come from? And how much does it cost?

So, for solving global warming, I would think they'd be quite useful, as they throw off no CO2. Their much higher efficiency means you're transporting way less fuel than you would otherwise be, meanwhile.

Most large-scale plans to use fuel cells are focusing on methane, alcohol, diesel, and gasoline as the fuels for the fuel cells - all of which will produce almost as much CO2 being burned in a fuel cell as being burned in a 1964 Dodge Dart.

Also, let's not forget rechargeable batteries. Advances are being made every day here as well, and this too will increase the efficiency of the things we use.

OK...first, what do rechargeable batteries have to do with anything? Are you referring to using solar chargers, or...?

Second - you would be surprised to find that many new appliances are already pretty darned efficient, relative to their maximum possible efficiency. The key is using less of these already pretty efficient devices.

The Ex-SO, for example, somehow needed to turn on and leave on 8 100-W lights, a heating blanket, a 200 W TV, and her computer before leaving for work today. Why? Because she is careless and of course does not pay the electric bill. She also is setting the furnace to 76 F, even though I want it now at 68 F ($600 in gas bills in two months made me do that). But, of course, she does not pay the gas bill either. If my water heater was electric, I'd take a wrench and shut the gas off to the whole damn house - that would show her.

I'm sorry...what were we talking about?

And honkeytonkwillie - COx? Shame on you! ;)

[hibernicus]

Originally posted by Britt
hibernicus says

Why does biomass fuel introduce a need to "balance the carbon cycle"? If you grow a crop and burn it, it releases the same amount of carbon during combustion as was fixed during growth.

The biggest problem with this is time scales, it takes a lot long for a plant to fix the CO2 from the air than it does for combustion to re-introduce it.
This means that to balance the cycle you need a total crop size of approximately biomass combusted*(the time taken to grow the biomass/time taken to combust the biomass), in order for the CO2 absorbed per hour to equal the CO2 produced per hour.

To "balance the cycle" you just need to grow the amount of biomass that you burn!

Think about it: you plant an area with a fuel crop such as willow, for example. After three years you can take your first harvest, and then you can coppice each year thereafter for chipping and burning. This is a more-or-less steady state situation, where the amount of carbon fixed each year is the same as the amount released in combustion.

Unless you're thinking of burning old-growth forest or something, the carbon economy of any fuel crop is going to be similar to what I have outlined. Better, in the case of annual crops.

[Britt]

hibernicus says

To "balance the cycle" you just need to grow the amount of biomass that you burn!

Think about it: you plant an area with a fuel crop such as willow, for example. After three years you can take your first harvest, and then you can coppice each year thereafter for chipping and burning. This is a more-or-less steady state situation, where the amount of carbon fixed each year is the same as the amount released in combustion.

Unless you're thinking of burning old-growth forest or something, the carbon economy of any fuel crop is going to be similar to what I have outlined. Better, in the case of annual crops.


No, for a three-year cycle you need biomass coverage of 4 times the yearly consumption rate. If you harvest X Kgs of Biomass (that took Y years to grow) containing Z Kgs of Carbon. X Kgs of this biomass will absorb Z/Y Carbon per year. Therefore in order for the remaining biomass to absorb the Carbon back in one year will require Y*X Kg of living biomass. This is the sustainable crop size but is quite different from the yearly crop size except in the case of a yearly growth/harvest cycle.
The post I pointed you to early states the experts estimate the greenhouse gas efficiency at approximately 93% (I assume this is for a sustaining crop size). It also gives you some figures on the size of crop hat is currently required for this process.
It has been my experience that we as a species are not very good at the long term planning required to insure the effective maintenance of a carbon cycle energy production system. The effects are just to disperse and long term for most people to concern themselves with. This means that 7% inefficiency will never be taken care of until it comes back to bite us.

[pantom]

Most large-scale plans to use fuel cells are focusing on methane, alcohol, diesel, and gasoline as the fuels for the fuel cells - all of which will produce almost as much CO2 being burned in a fuel cell as being burned in a 1964 Dodge Dart.




I must be missing something.
The whole selling point to fuel cells is supposed to be that they are much more efficient when used in, for instance, cars than an internal combustion engine. If a car on fuel cells can get twice or three times the mileage of a regular car, then it's releasing half to one-third the CO2, even if it's using a hydrocarbon for the fuel cell.
Right? Or am I being somehow dense?

[Una Persson]

Originally posted by pantom
If a car on fuel cells can get twice or three times the mileage of a regular car, then it's releasing half to one-third the CO2, even if it's using a hydrocarbon for the fuel cell.
Right? Or am I being somehow dense?

No, I was being dense. I misunderstood what you were saying; you are, of course, correct here.

[galen]

I think that too many people consider that alternatives to fossil fuels need to rely on one technology only. A sensible mix based on local conditions makes more sense. For example:

Coastal cities can use the ocean of heating and air conditioning. Water of the deep continental shelf can be a heat sink in the summer and a sorce of heat in the winter. This technology is pretty basic .In places which are not near the ocean, the earth can serve the same purpose, although its capacity is not as great.

Solar hot water heaters on rooftops can be both a source of space heat and hot water for domestic or industrial purposes. Very low tech and very cheap.

Geothermal. Anywhere there is volcanism like the Cascadia subduction zone.

Waves. Wave power can be harnassed by using devices which are basically two barges hinged together. As they flex, a piston between compresses air to drive a turbine.

Wind, more wind.

Tidal power. New technologies promise to be able to do it without all the environmental damage of places like the Bay of Fundy or St. Malo.

And of course, Photovoltaic, which everyone agrues is not cost effective. Perhaps, by conventional economic theory, but with a serious research effort and with rising fossil fuel generated electrictiy, it would eventually make sense for every rooftop to generate electricity. To me it is a nobrainer. It is just a question of time.

[Una Persson]

Originally posted by galen
I think that too many people consider that alternatives to fossil fuels need to rely on one technology only. A sensible mix based on local conditions makes more sense.

Yes, it certainly can.

Coastal cities can use the ocean of heating and air conditioning. Water of the deep continental shelf can be a heat sink in the summer and a sorce of heat in the winter. This technology is pretty basic .In places which are not near the ocean, the earth can serve the same purpose, although its capacity is not as great.

You forget that there are two things that are serious considerations here - first, the power of pumping water to and from deep from the continental shelf, and second there is both a high capital and maintenance cost involved, especially with something dealing with seawater.

But to your second point here - while the ground may not have much heat capacity, Seasonal Thermal Aquifer Storage has been explored and used by some institutions. This works on a cycle where cold water is pumped up in the Summer, used to chill a building, then sent through solar collectors, heated, and pumped back down into the aquifer - about a quarter mile away. Then in the Winter, the reverse happens. The warm water is pumped up, used either to heat the building or to supplement a heat pump, then chilled outside, and pumped back down into hole #1. It can work, but has a very low efficiency and serious maintenance problems sometimes.

Also, some local environmentalists will then get after you for "disturbing the environment" - damned if you try to save the Earth, damned if you don't (this actually happened at KU, when we did an analysis of using this sort of system to Heat and Cool the Foley Building on the West Campus. The environmentalist groups on campus, that we thought would be cheering us for being "clean green energy", instead howled in protest that heating and cooling the aquifer would somehow "disturb the balance of nature" - according to a laughably incorrect editorial.)

Solar hot water heaters on rooftops can be both a source of space heat and hot water for domestic or industrial purposes. Very low tech and very cheap.

I'll give you low-tech, but see some of the past posts by sailor about their cost effectiveness and maintenance problems.

Geothermal. Anywhere there is volcanism like the Cascadia subduction zone.

Well...you really do need some special circumstances to make geothermal power of any magnitude cost-effective. This is why this has not spread much further in use.

Waves. Wave power can be harnassed by using devices which are basically two barges hinged together. As they flex, a piston between compresses air to drive a turbine.

Inventive devices, but they are very low power output per $ of capital cost.

Wind, more wind.

Many issues here...best covered in some past threads.

Tidal power. New technologies promise to be able to do it without all the environmental damage of places like the Bay of Fundy or St. Malo.

Tidal power can work too, but the power produced per dollar is very low. And the absolute value of the power is very low as well.

And of course, Photovoltaic, which everyone agrues is not cost effective. Perhaps, by conventional economic theory, but with a serious research effort and with rising fossil fuel generated electrictiy, it would eventually make sense for every rooftop to generate electricity. To me it is a nobrainer. It is just a question of time.

Well...you make my point. It is not cost effective with current technology and by current measures, but may be soon.

The approach to always keep looking, and doing what we can, is great and admirable. I just hope we can get fusion going sometime soon...

[Arjuna34]

Originally posted by Anthracite
I'll give you low-tech, but see some of the past posts by sailor about their cost effectiveness and maintenance problems.


Where is sailor, anyway??

Here's a previous GQ thread where sailor analyzes the economics of solar power, about half way down the first page:

Whatever happened to Solar Power? (http://boards.straightdope.com/sdmb/showthread.php?threadid=40310)

Arjuna34

[Threadkiller]

One argument I have heard against logging (from a biology teacher I once had) is that if material were left to decompose in the forest it would break down and help build up the quality of the (often poor) soil.

Doesn't biomass farming ultimately deplete the soil? The stuff that gets burned is composed of more than just carbon. Is a system of crop rotation needed to keep this more self-sustainable?

[Una Persson]

Originally posted by crc
Doesn't biomass farming ultimately deplete the soil? The stuff that gets burned is composed of more than just carbon. Is a system of crop rotation needed to keep this more self-sustainable?

It is indeed something you have to be careful about when planning a biomass crop. You do have to let a certain amount of the biomass fall back to the soil. This amount varies by crop, but is included in the "typical" 7% loss of CO2 reduction given for most biomass crops. Thus, you still will get a large amount of usable biomass.

You can look at current farm crop management to see how they do it as well. Some farms have been successfully using the same fields nearly continuously for 100 years here in Kansas.

[Collounsbury]

Addendum re biomass and cropping: answer will vary by underlying soil type.

[Sam Stone]

One point that often gets missed when talking about rooftop solar collectors is that they are very dangerous. Currently, falls are the second most common cause of accidental death, and the number of falls per year would go up exponentially if we had complex rooftop systems that had to be repaired, cleaned, etc. We're talking about thousands, maybe tens of thousands, of deaths and serious injuries per year, if rooftop collectors were in widespread use (say, by 20% of homes).

In my opinion, there will never be a form of energy that the greens will be happy with. Concentrated power is dangerous no matter how you collect it, and almost all forms of energy collection affect the environment in some way. You can bet that if we come up with a clean geothermal energy source, the same people protesting nuclear power will find some reason to protest that, especially after some accident kills a few people or does some damage to the environment.

Currently, hydo dams and wind power farms are both under attack by some environmentalists, and those two technologies were proclaimed as part of the future by those same people 20 years ago, when they were fighting nuclear power.

Anthracite, has anyone done a study on the effect of solar collectors on the environment? If we replaced all of our power needs with photovoltaic, how much mining of things like Gallium, Selenium, would be required? Would covering that much of our surface with solar collectors measurably affect the Albedo? How about the local environment that would be displaced by huge collector farms?

My thesis is that many environmentalists are always in favor of the NEXT power source, the one we don't have yet. But once it becomes viable, they'll find problems with it. If we wind up with millions of electric cars on the street, there will be screams about the environmental problems from battery disposal, and a few high-profile accidents that require an environmental cleanup will cause a new hue-and-cry from the same people now trying to make it law that a certain percentage of us be driving electric cars in the near future.

[Una Persson]

Originally posted by Sam Stone
Currently, falls are the second most common cause of accidental death, and the number of falls per year would go up exponentially if we had complex rooftop systems that had to be repaired, cleaned, etc. We're talking about thousands, maybe tens of thousands, of deaths and serious injuries per year, if rooftop collectors were in widespread use (say, by 20% of homes).

You know...I laughed at first, and then I thought about it some...you really do have a pretty good point there Sam!