Solutions to the energy crisis / global warming problem

1. Feb 3, 2007

heusdens

We face an energy crisis, since gas and oil resources are diminishing this century. Oil and gas production follow a bell-curve, and around the middle of the depletion of a gas or oil field, the production of that field decreases yearly.

Apart from coal (for producing electricity) and nuclear energy, there aren't reasonable alternatives which can be utilized at this large scale and at the same costs. But both coal and nuclear power have their drawbacks.
[ Although energy from coal might be produced in a clean(er) way, in which the carbon-dioxide is not emitted in the atmosphere but stored under ground. ]

We have to take into account that the use of energy per capita is still significantly growing (for example: China, India), and also the population still grows enormously (doubles every 25 years).

So what to do?

There are of course alternatives. Utilizing sun energy, wind, tidal, geothermic and bio energy, which in principle are renewable.
The only problem is: in general they aren't available in the scale and concentration in which it is needed and/or are much more expensive.

However, the costs for (for instance) producing electricity is rising and might even rise more when we near peakoil scenario, and at the same time techniques for producing large scale wind or sun energy, are decreasing.

When wind and/or sun energy are produced at much larger scales, it becomes economically feasable, even when the energy has to be transported far away (as electricity or hydrogen).

For example, large parts of earth which are now uninhabited (the deserts) could become economic production centers for producing solar energy.
At a sufficient large scale, solar energy can become as cheap as other forms of energy. The extra costs for distribution for a long range (energy losses) also included. Also, energy could be distributed as hydrogen, for other uses.
Secondly, these deserts when sea water is desalinated could also become productive agricultural regions (in a long time, before the soil is improved, starting with plants that use little water and help other vegetation to survive), and hence, these kind of production facilities, on a sufficient large scale, could signicantly reduce green house gas emissions.

Of course, this could be only feasable in the long run, when price leves of conventional energy resources are significantly higher, and prices of large scale solar energy production systems are significantly lower.
But in some decades, this will most probably the case. And maybe even earlier, if we decide to boost this development (on an international/global level) with some inititial large scale investments.
What would be needed for that is creating some fund (in the form of some extra energy tax or CO2 emission tax, paid by the rich and energy consuming countries).
Extra benefits are: this will also help increase development of developing countries, for example, (sub) sahara countries, it would create many jobs and stabilize immigration levels to europe, etc. And most importantly: it will provide drinking water for millions of people in that region, who now face the problems of water shortages, which to them is a bigger problem then energy shortages.
Other regions which could be developed in this manner: large part of the middle east and arabian peninsula, large part of west china and surrounding regions, australian inlands, south east of united states, etc. and other dry regions with a lot of sunshine.

Last edited: Feb 3, 2007
2. Feb 3, 2007

joema

The "peak oil" scenario doesn't consider non-conventional hydrocarbon reserves. Three sources: tar sands: http://en.wikipedia.org/wiki/Tar_sands, oil shale: http://en.wikipedia.org/wiki/Oil_shale, and methane hydrates: http://pubs.usgs.gov/fs/fs021-01/fs021-01.pdf, http://news.thomasnet.com/IMT/archives/2005/03/mining_the_ocea_1.html?t=archive. Each may have double the equivalent barrels remaining in conventional petroleum.

So the apocalyptic peak oil scenarios likely won't happen because production will simply shift to non-conventional sources. The problem is they're still hydrocarbons, and extracting them is expensive and environmentally damaging. But it's already happening. Canada already gets 20% of their petroleum from tar sands: http://en.wikipedia.org/wiki/Athabasca_Tar_Sands By 2020, 50% of Canadian oil production is expected to come from there.

But that only solves the supply problem, it does nothing about greenhouse gas emissions, in fact makes it worse.

As you said, the problem is one of scale. The solution(s) must (a) Have adequate areal/yield and net energy efficiency, and (b) Must be scalable to the titanic levels required to make a difference, and within a meaningful time frame and achievable cost.

There's lots of talk about alternatives, but few people apparently do the simple math using real world numbers to sanity check whether the solutions are scalable.

In 2004 the world used 446 quadrillion BTU of energy, equivalent to 1.3E17 watt hours: (.xls file) http://www.eia.doe.gov/pub/international/iealf/table18.xls. About 85% of that was from hydrocarbon sources. World energy consumption increases at about 1.5-2% per year. By 2020 (only 13 yrs away), the EIA projects world consumption will increase to 607 quadrillion BTU (1.78E17 watt hrs).

Simple math shows replacing a sizeable fraction of this with alternative, non-hydrocarbon renewable sources is staggeringly difficult.

If you started a massive global project today, it would take a decade or more to implement. Say by 2020, you want to replace 1/2 of then-world energy consumption (8.9E16 watt hrs) with wind power. What area is required?

A typical wind power density per acre is 50 acres per megawatt, realistic capacity factor is 23% (meaning they produce on average 23% of rated power). So to equal the output of a single conventional 1 GW fossil or nuclear plant requires (50 * 1,000)/0.23 = 217,000 acres. Each 217,000 acres would produce 1GW on average or 8.76E12 watt-hrs/yr/217,000 acres, or 40E6 watt-hrs/yr/acre.

So to produce 1/2 the world's energy by 2020, you'd need: 8.9E16 watt-hrs/yr / 40E6 watt-hrs/yr/acre = 2.2 billion acres (8.9E12 square meters), roughly the entire land area of the continental U.S.

Breaking down the problem to multiple sources (solar, corn ethanol, etc) doesn't help, if the aggregate areal and net energy efficiency of those sources aren't dramatically better. But if they are better, you'd just use them in the 1st place.

3. Feb 5, 2007

joema

According to the IPCC, to control global warming requires reducing global CO2 emissions by about 75% over the 21st century. Even this would only limit atmospheric CO2 levels to 450 ppm, significantly above today's level. Since 85-87% of global energy consumption is from hydrocarbon sources, this means a reduction of 75% of this 85% fraction. By 2020 world energy consumption will be about 607 quadrillion BTU. At that point, the amount of alternate source energy required would be

.75 * .85 * 607E15 BTU = 3.86E17 BTU or 1.13E17 watt hours.

Solar PV is out, as it can't be scaled to the gigantic industrial levels (many thousands of square miles) required. Thermal Concentrating Solar Power (CSP) is much cheaper and has better areal efficiency than wind power. Would this be viable?

Actual large-scale production solar generation in southern California give real-world statistics of what's possible: (1 MB .pdf): http://www.p2pays.org/ref/18/17986.pdf

SEGS solar plants III through VII use parabolic troughs and total about 870 acres occupied land area. Actual AC power output (inc'l all loses) is about 350,000 MWh per year. That's about 402E6 watt hrs per year per acre, or about 100,000 watt hrs/m^2/yr. Average solar insolation in that zone is 7,600 watt hrs/m^2/day or 2.8E6 watt hrs/m^2/yr. Thus the end-to-end solar/electric efficiency is 100,000/2.8E6 = 3.6%. It's likely so low because of various real-world losses, plus the actual collector area is only about 1/2 of the occupied real estate. E.g, "overhead" acreage is required for structure, maintenance pathways, etc. That's unavoidable.

Thus to produce the needed global power would require 1.13E17 watt hrs/yr / 402E6 watt hrs/yr/acre = 281 million acres or 439,000 square miles, or roughly 3x the land area of California. So while the areal efficiency of solar is better than wind, if scaled up to the titanic levels required to make a real difference, it still may require more land area than is available. That also doesn't consider the inevitable need for energy growth (about 1.5-2% per year). E.g, within 35 yrs, you'd need double that land area (6x California), in 35 more years 4x that (12x California), etc.

So while solar power is useful for a small fraction of world energy need, to supply the energy in sufficient quantities to limit atmospheric CO2 to 450 ppm, a more scalable solution is needed. Don't know what that is, but the answer isn't building wind turbines and solar panels, at least with current technology.

It's tempting to say "we don't need a single solution, just a bunch of little ones". That just pushes the problem elsewhere, which still must be solved. Regardless of how the problem is partitioned, the alternative sources will still occupy an aggregate acreage and supply an aggregate power output. If the aggregate net energy output/acre, net energy balance (energy in vs energy out), and deployment costs and timeframe don't fit the available real estate or environmentally-dictated deadlines, whether the solutions work on a small scale is meaningless.

Edit/add: OTOH a massively-scaled up solar thermal plant can still produce a lot of power, even if insufficient to materially affect global warming. E.g, using the same technology as in the current SEGS plants in California's Mojave Desert, capital construction costs are about $2500/kw. A 175km x 75 km solar plant in the Mojave would cost about$224 billion, and would produce about 1.3E15 watt hrs per year, or roughly equivalent to the combined annual generation capacity of the approx. 103 U.S. nuclear plants. That also includes a 50% overhead for efficiency loss from using molten salt thermal storage for load shifting to periods of peak demand.

Last edited: Feb 5, 2007
4. Feb 5, 2007

ray b

birth control
more people more polution
less people less polution

5. Feb 5, 2007

heusdens

Global warming is not the only and maybe not even the most important problem. Staggering prices levels will most probably cause many more victims.

I would not say that, based on your figures, nothing can be done. The problems is however, the political will is not there to do anything significant.

The US govt. simply refuses to adjust their economy and standard of living.
This is the most important problem.

With a budget of about 1-5% of the money currently spent on military, I am convinced a lot can be done.

Any change / adaptation in the way we use energy has to start from the way we use energy. You can adapt to using significantly less energy, without decreasing one's standard of living.

You have to start with more economical useage of energy and stop waisting energy.

Transportation is much more efficient when you use public transport and trains and ships, instead of airplanes, SUV's / automobiles, etc.

Houses and buidings can be built in such a way that the energy needs drastically decreases (for instance extra thermic-isolation and passive use of the sun), and the energy can be suppied with sustainable techniques, which practical makes any outside energy need obsolete. For example a combination of a heat-pump (using a cold and warm thermal bassin under the building) and solar panels (the new solar-film produced by nanosolar, may become a very cost effective solution, the pay-back period is about 1 month!) and maybe a small wind turbine, can make the building self sustainable on average.

About 15% of energy is used in and around house (heating, cooling, light, washing, equipment, etc), so we could in principle eliminate that energy usage in the long run.

In transportation, I guess when the necessary shifts are made, one can reduce 20-50% of energy needs. Which means: most cargo must either be shipped or transported by trains and for cities, in electric cars. For human transportation: use electric cars for short range (personal or rent-a-car system), and good public transport for the long range.

If we put everything together internationally to beat the energy problem, a lot can be done in 10-20 years. For example current dry and sunlike regions can be made productive using solar production plants, which could produce electricity and water (from salt water, pumped from sea) and/or hydrogen (or other energy storage for long distance distribution).
Current most cost effective solar power is from concentrated solar power plants, which have the advantage that you can also desalinate water for producing drinking water.
But maybe in the near future even more cost effective solar power can be developed, or building costs can decrease when increasing the scale.

These solar power plants could be combined with producing bio fuels, for example the jathropa plant, which delivers bio oil, and can grow on very dry and poor soils, actualy improving the soil.
Unlike other biofuels, jathropa plants don't conquer with food, the plant is uneatable, and nothing else would grow on the soil.

If we realy want to, an area the size of france in solar power could provide the amount of energy the world needs.

There is a lot of area on earth that could be used:
SW USA, Australia inlands, Pakistan, India, Gobi dessert in China, Sahara, Middle east/arabian penninsula....

I don't know what size this adds up to, but is much more then 20 times the size of California.
It would be more then sufficient area for the world needs in hundreds or more years.

These regions, currently (mostly) uninhabited, could become habited again and self sustainable. People from poor countries, living near cost lines that might drown from rising sea levels, could be invited to migrate and work there.

In the long run (50-100 years), through carefull land usage, these areas could be turned from desserts into farmlands or vegetation zones, thereby contributing in both ways to decreasing greenhouse gasses and also reducing the deserts.

If we realy want to, this can be done. That is, it could be done on the time scale from 20-80 years.

The money, currently spent on military means, is there. If only 10% of the global military spendings were used, this would be enough to provide for the initial investments. And they would pay-off in the long run, just that one has to invest a lot initially before this kind of energy becomes cost effective, perhaps only after 10-20 year. But then: military costs are a waste of money. They cost the tax payer money, but there is no return on that money spended. The money spent on large scale solar power plants, will pay itself off, will make solar power cheaper, the technology better, etc.

It would provide much more safety and prosperity as the current military usage, since such projects would need to be undertaken on a global scale, demanding large scale peacefull international cooperation.

Projects this scale are not just targeting for solving the energy problems, but could also contribute to prosperity in poor countries (for example sub-saharan countries) that suffer from underdevelopment. You would need a large work force to produce such large scale solar power plants and maintain them. Part of the land under the collectors could be used for agricultural usage. Worldwide millions of workers could be employed in this areas in a period of decades.

But of course, what is realy needed is that such collosal funds are being put into projects like these. The political will must be there to do that. It would mean, for example, for the US to realy change their domestic energy politics and also their PNAC plan (project for a new american century, which boils down to "solving" the energy related problems with military means, which realy solves nothing), and instead try to establish the political will to cooperate on a large scale with other countries and nations and actually solve some problems (instead of creating new ones, like they do in Iraq).

And of course... birth control would also be a good thing.

Last edited: Feb 5, 2007
6. Feb 5, 2007

grant9076

You brought up some valid points. However, there are other solutions, that our society is currently ignoring. One example is thermal depolymerization which can be used to turn garbage into oil and solve two major problems (polution and energy) simultaneously. In addition, only about 15% of the energy contained in garbage gets wasted (to run the conversion process) and the plant is fully scalable. Also, because it uses carbon that is already in the ecosystem, no new carbon is introduced into the ecosystem. The test plant that is built in Carthage, Missouri was only recently able to turn a profit because they had to buy their garbage at a premium.

7. Feb 5, 2007

joema

The thread is global warming and there's a lot of recent attention on that, so that was my emphasis. Energy prices won't become staggering for a long time. There is at least a century of coal left, and lots of petroleum in non-conventional sources such as tar sands and oil shale.

Thus the near-term problem isn't one of supply or one of prices, but of environmental cost in harvesting and using these.

It's a very common misconception, but the problem isn't the US economy or standard of living. This can be seen from this analysis done by the Federal Reserve: http://www.dallasfed.org/news/educate/2004/04ecsummit-brown.pdf Look closely at the graphs on page 2 and study them a long time. They are very important.

The key is not energy use per capita but energy use per GDP unit. If 1/2 of workers were replaced with automation, the energy use per capita would skyrocket. Yet that wouldn't be bad (from an energy standpoint), but good. You're producing more GDP with less workers; productivity is higher.

Likewise the main reason energy use in the US is so high is the economy is so large. It takes energy to produce GDP. In general the US uses no more energy per GDP unit than other industrialized nations, as shown in above-listed graphs.

It's definitely correct that expenditures on the order of a large military operation could fund tremendous energy programs. E.g, it might be possible to to fuel the entire US vehicle fleet from a hydroponic biodiesel farm that would occupy 500,000 acres and cost about $300 billion to build: http://www.unh.edu/p2/biodiesel/article_alge.html While today's energy problems are often attributed to SUVs, etc, if every single gasoline car in the U.S. overnight became a Toyota Prius, it wouldn't make a huge difference in US or world energy consumption. Why? Gasoline consumption of all U.S. vehicles constitutes about 40% of U.S. petroleum use. The remaining 60% is used for heating oil, jet fuel, and the petrochemical-based products (plastics, fertilizer, etc) that make up everything around us. So every car becoming a Prius would roughly double the fuel economy of the U.S. gasoline vehicle fleet, which would decrease petroleum consumption by 50% * 40% or a total 20% reduction. Initially that looks like a big improvement. But since the U.S. imports 60% of its oil, it would only reduce the import fraction to 40%. U.S. road vehicles consume about 11% of world petroleum, so the above increase would reduce this by 20% * 11% or 2.2%. That's good, but since world petroleum consumption increases by about 1.5-2% per year, replacing every vehicle in the U.S. yielded the equivalent of 14 months of petroleum consumption. From a world energy standpoint (of which petroleum constitutes about 40%), it would yield 2.2% * 40% or 0.8% reduction world energy consumption -- that's if every single SUV and car were replaced overnight with a Toyota Prius. Conservation is good but you can't conserve your way out of the problem (either from an energy supply or GHG emissions standpoint). Even mind-boggling overnight steps (like replacing every vehicle with a hybrid)only make a relatively small difference. Those steps are good in the sense that any improvement is better than nothing. But the immutable math shows it clearly won't solve the underlying problem from either a supply or GHG emissions standpoint. E.g, the IPCC says an approx 75% reduction in carbon emissions is needed, and you can't achieve that by getting rid of SUVs, or even all vehicles on earth. 8. Feb 7, 2007 heusdens The problem is that the US spends so much energy (five times as much pro capita as the average of the world), since most of that energy isn't renewable. Which is to say, any energy used by the US now can't be used for other nations and future generations. So it adds up to the problem. You argue that "it is good" to have a high GDP. But for that same reason, this would be true for other countries and future generation, which however would increase the problem. If China's economy would be the same GDP per capita and the same energy use per capita, then the problem would be immense. Yet, are you to say we should deny the chinese (or other people) the same standard of living as the US citizins? That is what we need to solve. If there would not be a problem in producing all the energy we need from durable and renewable resources, then of course, this would not be an issue of consideration. Yet it is, because most energy comes from non renewable resources. Like you state, replacing SUV's with other cars is not enough. You don't need a car, what you need is the means of living, and which includes mobility, which can be provided in more economical ways. For local transport, cars can run on electricity, and the electricity can be made available from renewable resources. Long distance transport can take place by a public transport system, trains, busses, which can be very energy efficient. Now a good public transport system can bring you in many cases also where you want to be. And another thing, why drive 100 miles everyday to work, if you can live closer to your workplace? Reducing the need for mobility, bringing work and places to live closer together, also would reduce the problem. Driving that many miles does not increase your standard of living, instead it wastes much time which could be spent in much different way. You have to work very hard for affording that car, and then spent so much time in the car for driving home. Your standard of living would improve also when you don't have to work that hard, and would not need to drive that far. If you want to have the luxury that everyone has a personal vehicle, then of course there is a huge problem when you scale that worldwide. You have to realize that. Unless you show me how that can be solved on this scale, I don't think the economic level of the US is good, because it is untainable at a global scale. So the problem with the US economy being so large is that it could not be scaled to the whole world, it would make the problems related to energy immense and unsolvable. I am a supporter of drastic global measures. Some minimum level of standard of living (at least food, housing, health care, education, clean drinking water, etc.) for everybody, and not gigantic differences in standards of living. A great part of humanity has to live on a dollar or so day. I do think we have to consider that a great part of humanity does not profit at all from the current economic conditions, but do face the (climat) problems. I think that the global economy should guarantee that everyone on earth now and in the future can have access to an accepted minimal standard of living. Including everything needed to live, that is without hunger, desperatedness, misery, etc. And when on economical and environemental and humanitarian conditions it is possible to raise that level for everyone, the better it is. But that would also mean the economic wellfare of some people, currently owning large parts of the economy, would have to reduced. It doesn't mean that everyone should be economically totally equal or something, of course some people do more intense work then others, but roughly said one should have economic and social guarantees on a minimum standard of living. Hard working people can perhaps earn twice that much, or three times as much, but that may be a reasonabe limit, because it is physical or mentally impossible to work like 10 times or 100 times harder then average. Most economic value which currently risis far above that level is not earned by own labour, but made from profits of other peoples labour, working in poor conditions. What this means is: the rich could not be so rich without the other people being so poor. There is no possible way in which this system could provide an outcome in which the same level of economic prosperity could be more evenly spread. The economic mechanisms necessarily produce wealth for a minority and poverty for a majority. So simply one should abolish private property (that is: large enterprises employing many people from which one makes a profit, not personal property, which you earned by own labour) and make profit out of that. Having your own firm, and earn a living on your own labour without exploiting others is of course no problem. Last edited: Feb 7, 2007 9. Feb 8, 2007 joema Energy use per capita is nearly meaningless. For the subject at hand (global warming) it is a red herring. What counts is energy use per GDP unit. High energy use per capita doesn't mean individuals are frivolously wasting energy. It's simply the quotient of dividing total national energy use (the majority of which is industrial) by population. If 1/2 the U.S. population died overnight and were replaced by equivalently-productive robots, energy use per capita would skyrocket. Why? Because the survivors used more energy? No, because you're dividing the same GDP by 1/2 the population. Likewise a highly productive workforce will often be associated with high energy use per capita, but that doesn't mean it's due to individual lifestyles. Understanding this is important because otherwise corrective efforts will target the wrong area and things won't improve. The key is how effectively products & services (GDP) are produced from a given amount of energy. U.S. energy efficiency has dramatically improved each decade since 1950. http://tonto.eia.doe.gov/FTPROOT/presentations/25thann/sld017.htm You're correct there is a huge looming problem, but it's not what you stated. The problem is large industrializing nations such as China have poor energy efficiency, thus consume more energy per unit GDP. China already consumes more coal than the U.S: http://www.nationmaster.com/graph/ene_coa_pro-energy-coal-production China may overtake the U.S. as the world's largest carbon emitter WITHIN TWO YEARS: http://www.theglobeandmail.com/serv...03.wclimatechina03/BNStory/ClimateChange/home This is DESPITE having a much smaller economy. It's caused by inefficiency. China consumes about 60% of the total energy consumed by the U.S: http://www.nationmaster.com/graph/e...equ-consumption-million-tonnes-oil-equivalent While producing only 14% of the GDP: http://www.nationmaster.com/graph/eco_gdp-economy-gdp-nominal The impact on global warming is most of the energy is hydrocarbon-based so CO2 emissions will scale upward with the increasing energy consumption. In the U.S. and other western nations, energy consumption increases slowly, roughly scaling with GDP output, minus gradual efficiency improvements. However with China, India, etc. energy consumption (hence CO2 emissions) will increase far more rapidly as industrialization moves forward with less energy efficiency per GDP. Mass transit is almost irrelevant to the problems at hand, for two specific reasons: (1) World transportation energy only constitutes about 25% of total world energy consumption: http://www.eia.doe.gov/oiaf/ieo/highlights.html If every car on earth disappeared overnight and was replaced by magic carpets, total energy consumption would only decrease by 25%. Since world energy consumption grows by about 2% per year, in about 14 years consumption (hence carbon emissions) would regain the same levels as before cars vanished (PDF): http://www.eia.doe.gov/oiaf/ieo/pdf/world.pdf (2) Society already exists in the current form. Roads, housing, population centers, etc are already there. You can't erase everything and start over. Increased mass transit cannot be incorporated on a scale and in a timeframe that materially affects the problem at hand. As shown by the above, the primary problem isn't energy consumption by the transportation sector, hence emphasizing changes in that area isn't the solution. The chance of mankind restructuring all human society on earth as you described is about equal to the chance a space alien will land at the U.N. and hand us a zero-point energy device that solves all energy problems. 10. Feb 8, 2007 heusdens The analyses is correct, if you just look at energy usage per gdp. I was making the analysis at the basis of the absolute energy usage per capita. They are two different analysis. Still, for the world energy problem, you must of course also look at how you replace the energy, when fossil fuel become less cheap. Which will happen. And another thing: the technological more advanced countries that already have more efficient energy usage and energy techniques, would need to see it as in their benefit to have less developed countries share that technology, since the pollution of the large and fast developing countries of India and China is in the near future the biggest problem. It would advocate that such technology transfer should be highly stimulated and not be limited too much by patents and so on. Partly that is true and this very fast growth rate in this way is a concern, but China is catching up, there are a lot of projects under development to produce renewable forms of energy. They have on the country side biogas installations, they build massive amounts of windmils and the solar tower (the same type as built in Mildura, Australia) is also gonna be built in China, and likely they gonna implement other forms of clean energy. Their only current alternative is use massive amounts of coal. Don't forget that China is still a developing nation, yet they develop far more quickly as other nations did. Partly they make the same environemental mistakes (huge polution, for instance), but there is a lot if focus on these kind of issues. I think they adapt to cleaner production techniques quite fast, hopefully fast enough to catch up with the economic growth rate. Still, there is a lot to do in an economy that grows as fast as the Chinese. Well 25% reduction is a LARGE reduction anyhow. You can not render that meaninglessly. It would take quite some time to reach that level of reduction. By the way one should not aim at reducing energy needs only in one sector, you have to have a more realistic and holistic picture of things. It isn't THE solution, but it is a part of it. I didn't state that that is the only problem. I was not thinking in wiping that all out today and start again tomorrow, if that is what you think. It is about changing the policy to make a change in the long run. It effects everything of course. Public transport systems and city planning must aim at reduced costs/energy usage. And a zero-point energy device doesn't exist (even if the vacuum has vaste amounts of energy, the energy principles on hand forbid that this can be used, because if there would be a lower vacuum state, the very use of that vacuum state would tunnel the whole universe directly into that lower vacuum state). So, we have to make adaptation that make a difference in the long run. Besides, you forget some aspects. When you can reduce the usage of cars (without, as said, limiting the mobility as such and in as far is needed, one can also reduce the need for physical transport without limiting one's freedom and standard of living), you also reduce the amount of industrial production (car production). Well partly it is changed to other activities (producing trains/railroads, busses), but the over-all effect is less production. And I already explained how in the long run all energy usage in and around the house may be reduced to zero (step wise of course, takes 40+ years at least), which is about 15% of all energy needed. New generation of cars could run on batteries which you can tank at home, using the output of excess solar or wind energy produced at home, or from the grid, which produces energy partly also from renewable resources. Or there could be an intermediate generation of cars running on different fuels (biofuels and fossil fuels). That kind of reductions DO count, since all energy not needed, means that energy does not need to be replaced. My point of view is that all these changes together makes it possible to have an economy which is independend of gas and oil within 50-100 years. Usage of coal could be technological advanced to very reduced level of emissions of carbon-dioxide. Perhaps in a 100 years time also fission nuclear technlogy is available. For the rest large scale solar projects and wind projects and bio-fuel usage, would provide a substantial part of the energy usage. I don't think this is too unrealistic, given the fact that rising oil prices and decreasing prices and increasing efficiency of renewables, will shift the interest to alternative energy anyhow (within 20 years, for sure!). A realistic time scale of 50-100 years can make such a scenario possible, that is replacing almost all fossil fuels. Besides: what is your alternative? Just wait till the oil price is staggering high (which causes a downfall of the economy and make it too late to deploy other energy resources) or just fight a war for oil? Last edited: Feb 8, 2007 11. Feb 9, 2007 joema China is NOT catching up in terms of reducing dependence on hydrocarbon energy and the resultant carbon emissions. Despite some efforts to use renewable energy, China's hydrocarbon energy consumption is skyrocketing. China might achieve 10% renewable energy by 2020: http://www.renewableenergyaccess.com/rea/news/story?id=23531, while coal and oil consumption will increase far more. Although China already burns more coal than the U.S: http://www.nationmaster.com/graph/ene_coa_con-energy-coal-consumption, this is expected to double AGAIN by 2020: http://www.findarticles.com/p/articles/mi_m0EIN/is_2006_May_30/ai_n16419892 You mainly focused on transportation-related energy consumption. My point was that focus is misplaced and not the solution. This is illustrated by ALL transportation energy being only 25%. That includes trucks, jet planes, buses, etc. The fraction taken by automobiles is a subset of this, and the improvable fraction a further subset. If all transportation on earth was replaced with magic carpets, it would not prevent global warming (according to the latest IPCC numbers). It takes vastly greater reductions. Part of solving the problem (global warming) is understanding the relative contributions of each sector, what reductions are possible within a given period, and what it takes to achieve these. Even mind-boggling, miraculous changes to the transportation sector will not solve the problem. Actual real world, achievable changes are small relative to the problem. So the answer isn't talking about mass transit and electric cars. You mentioned greatly increased public transit, abolishing private property, forced redistribution of wealth, etc. For that to be meaningful within the available timeframe would essentially require wiping out existing society and starting over. According to the latest IPCC numbers, making gradual changes over the long run is insufficient. Simply changing laws so new construction is more centralized and gradually adopting more mass transit is insufficient. This can easily be seen by the IPCC numbers. The required target is 490 cumulative gigatons carbon emissions over the remaining 93 years of the 21st century. The baseline "no change" number is about 1900 gigatons: https://www.physicsforums.com/showpost.php?p=1231935&postcount=60. About 75% reduction over the remaining 21st century is needed. Since it takes decades to deploy massive changes, the initial period will still consume hydrocarbon energy in huge amounts. Hence the later decades of the 21st century must consume almost no hydrocarbon energy. You don't achieve those changes by taking the bus or driving an electric car. You can't reduce to zero energy consumption of existing housing within 40 years. You can devise new energy efficient housing, which has a small effect. As you stated the entire sector is 15% and you can only change a fraction of that. The collective improvement of all items you mentioned which are realistically achievable is far less than the IPCC limit of 490 gigatons carbon over the remaining 21st century. It is incredibly unrealistic, and is unlikely to happen. You can do the math yourself. The world will consume 613 quadrillion BTU (1.8E17 watt hours) of energy by 2020: http://www.eia.doe.gov/oiaf/ieo/world.html Using real-world numbers including all losses, calculate what alternate, renewable sources can provide 75% of this. The first step of the scientific method is "define the problem". If the problem isn't defined, you can't solve it. If the problem is how to reduce hydrocarbon energy consumption, many methods will work: electric cars, solar thermal plants, fission reactors, etc. However -- if the problem is reduce cumulative carbon emissions (roughly hydrocarbon energy consumption) by 75% over the remaining 21st century, none of the items you mentioned will work, separately or collectively. The topic title is global warming. To reach the IPCC goal of 490 GtC requires titanic changes. I don't have an easy alternative, nor is that necessary to discuss the problem. Problems exist for which there is no answer. It's important to think like a real scientist and look at the facts, no matter how unpleasant, and no matter how that differs from common perception. From an U.S. standpoint, there are possible solutions which could greatly reduce dependence on hydrocarbon energy. E.g, the entire U.S. vehicle fleet (if converted to diesel) could be fueled by a high-yield hydroponic biodiesel facility that would occupy about 15,000 square miles, and cost about$308 billion to build: http://www.unh.edu/p2/biodiesel/article_alge.html

Likewise about 20% of U.S. electrical energy could be provided with a 175km x 75 km solar thermal plant in the Mojave costing about \$224 billion (1 MB .pdf): http://www.solarpaces.org/STPP Final Report2.pdf

Gigantic projects like are physically achievable, and would greatly reduce dependence on foreign oil and modestly reduce world energy consumption. However even if every country did similar steps, it's insufficient to meet the IPCC goal.

This illustrates the difference between making a significant improvement and solving the global warming problem (at least as defined by the IPCC). Much bigger changes would be needed.