To calculate how much alternative energy you need to build to replace fossil fuels, you need to know:
Fossil fuels supply 85% of the 100 quads of energy the United States consumes every year. Fossil fuels have been dominant for over 70 years. Our dependence on imported oil doubled between 1990 and 2007. The United States has only 2% of global oil reserves most of which are difficult and expensive to extract. the rest of the world can maintain its current production of conventional crude oil from known reserves some four times longer than the United States can (hence our gigantic military so we can be the “Last Man Standing”).
That all fossil fuels have peaked (oil), probably coal, and soon natural gas
Petroleum supplies 98% of the energy used in transportation (biofuels only provide 2%). The engines that do all of the actual work of society are combustion engines that burn fossil-fuels. “Our world is a giant machine with billions of moving parts. Its primary fuel is oil. Here in the United States, 98% of our 300 million cars and trucks run on gasoline. Nearly 100% of our farm vehicles and 99% of our railways run on diesel. All of our jet planes run on kerosene.” (Energy Collapse – Peak Oil, Painful Withdrawal)
These 300 million vehicles, container ships, oil and gas pipelines, refineries, and other infrastructure represent a such a huge investment that they can not quickly or easily be replaced. Ideally you’d keep it in place by replacing oil with liquefied coal or biofuels, but that can’t be done quick enough, nor is there enough coal, tar sands, or biomass liquid fuel to ever replace more than a small fraction of the oil we’re burning now.
The most important combustion engines — tractors to plant and harvest crops, trucks, ships, long-distance trains, and mining vehicles can’t run on batteries or fuel cells, can’t be electrified, can’t run on biodiesel or ethanol, and can’t be replaced with a (non-existing solution) as fast as the decline of fossil fuels. It takes decades to replace fleets of vehicles, which also suffer from the potential of a shortage of resources such as rare earth metals and the energy required to mine ore and fabricate the vehicle itself (Hirsch 2005).
Scale. We burn 1 cubic mile of oil a year. Here’s what you’d need to do to replace that energy 
Allowing fifty years to develop the requisite capacity, 1 CMO of energy per year could be produced by any one of these developments (source Joules, BTUs, Quads-Let’s Call the Whole Thing Off – IEEE Spectrum):
4 Three Gorges Dams,developed each year for 50 years (18 gigawatts), or
52 nuclear power plants, developed each year for 50 years (1.1 gigawatts, such as the Diablo Canyon Power Plant), or
104 coal-fired power plants,developed each year for 50 years (500 MegaWatts), or
32,850 wind turbines, developed each year for 50 years (large turbines with 70-100 meter blade span, rated at 1.65 MW, i.e. General Electric Wind Turbines), or
91,250,000 rooftop solar photovoltaic panels developed each year for 50 years (a typical 2.1 kW panel)
If you wanted to invent an ideal energy source from scratch, you’d make oil:
Oil is the most convenient form of energy ever discovered, second only to nuclear fuels in its energy density. As a liquid, it’s easily stored, transported, and used. It’s wonderfully combustible, but with a high enough flashpoint that it doesn’t explode easily. Its complex hydrocarbon chains are the basis of the petrochemical industry, which uses oil and natural gas as a feedstock in over half a million products, and each item is made with fossil fuel energy.
You’d need to understand how dependent alternative & renewable energy resources are on fossil fuels from start to finish and beyond (maintenance)
Oil is like a butter fried steak wrapped in bacon. Solar, Wind, and most other forms of alternative energy have about as much energy as a head of iceberg lettuce. The renewable lettuce was planted and harvested with a diesel tractor, sprayed with oil-based pesticides and natural-gas based fertilizer, harvested early in the morning and put into a refrigerated warehouse until diesel-powered trucks could haul it to your supermarket and put in a refrigerated area, and then you drove in a gasoline-fueled car to buy it, where it was run up on a cash register probably powered by either coal or natural-gas generated electricity.
Just like lettuce, alternative energy resources are dependent on fossil fuels from start to end, and therefore not truly renewable since they can’t make, or even come close to reproducing themselves, without tremendous amounts of fossil fuels.
At the heart of our dilemma is the fact that Oil is the MASTER RESOURCE that UNLOCKS ALL OTHER RESOURCES.
As long as you have oil, you have fresh water, because you can drill down and pump it up from 500 feet below. As long as you have oil, you can find the last remaining schools of fish with spotter planes and sonar in the most distant parts of the globe and scoop them all up. As long as there is oil, you can make cement, plastic, steel, computer chips, mine lithium, uranium, rare earth metals, and all the other essential components of alternative energy “solutions”. As long as there is oil, you can grow, harvest, distribute, shop for, and cook food. Try to think of anything you depend on to survive that doesn’t depend on oil at some point (to spark your imagination, see the antecedents of pencils, computer chips, toasters, soda cans).
You’d want to understand how long it would take to convert from fossil fuels to something else so you could start enough ahead of time to avoid war and social chaos over the remaining resources
It took us about 50 years for the world to switch from wood to coal, and another 50 years to switch from coal to oil. We have no time to try to switch to something else. Even if we did, nothing would be as good as oil or we’d already be using it.
The only transportation fuel a National Academy of Sciences report in 2009 could come up with to replace some of the oil we burn every day was a crash course to build liquified coal plants immediately and grow them at 20% per year so we could produce 3 million barrels a day by 2035, about 15% of what we burned in 2007. If we wanted to product 5 million barrels a day we’d need 700 million tons of coal a year — 70% more than we consumed in 2009. That in turn would require a huge investment and expansion of coal mines and transportation infrastructure to get coal to liquefaction plants and deliver the liquid coal to fueling stations. Meanwhile, many electric power plants depend on coal and would be competing for any coal produced (NAS 2009).
The NAS noted that we don’t have enough natural-gas hydrates to use as a feedstock for transportation-fuel production. So we’d have to import it and we don’t have the infrastructure to do that now. We also increasingly are using natural gas for electricity production and to keep the grid from blowing up from intermittent alternative energy like wind and solar with NGCC plants. At best we have enough NG to fuel 1/5 to 1/4 of transportation from our NG reserves, and it would take a tremendous amount of investment in a new distribution infrastructure and fleet of NG vehicles. Natural Gas vehicles aren’t a solution — there aren’t enough fueling stations, and the tanks take up most of the trunk space, their range is at best 100-150 miles, and the public thinks of natural gas as too explosive. Nor is GTL (gas to liquids) diesel or Compressed Natural Gas (CNG) possible unless an abundant and inexpensive source of natural gas were found (NAS 2009).
Dimethyl ether (DME) is not suitable for spark-ignition engines because of its high cetane number, but it can run a diesel engine with little modification. the primary challenge facing the use of DME is the lack of an infrastructure for distribution. Other disadvantages include low viscosity, poor lubricity, a propensity to swell rubber and cause leaks, and lower heating value compared with conventional diesel (NAS 2009).
The Department of Energy paid Robert Hirsch to do a Peak Oil study in 2005. Hirsch concluded you’d want to start at least 10, or better yet, 20 years ahead of time before peak oil to prepare for the transition to other energy resources.
Since there is no time left to make a transition, the energy source any expensive, large-scale project pursues must be able to be used in combustion engines. So solar, wind, nuclear and other sources of electricity are simply not of interest near-term, because they can not possibly replace the fleets of trucks, tractors, trains, ships, barges, mining equipment, and other combustion engines that do the work of society.
The infrastructure supporting oil use is huge, and not easily replaced. Trillions of dollars have been spent to build refineries, oil vessels, drilling rigs, the military air and naval fleets we use to ensure the oil keeps flowing, and the distribution system (i.e. pipelines, oil-delivery trucks, gas stations, etc). Not to mention the billions of cars, trucks, airplanes, and other combustion engine machines that use oil.
The energy to create all these combustion engine-driven machines — from the mining of metallic ores to fabrication — is monumental in scale as well. You can’t suddenly build a new fleet of solar, wind, coal, or nuclear driven tractors, trucks, and cars and billions of batteries, especially at a time when energy is growing more scarce and expensive.
There are many other factors besides energy to consider
The problems with energy resources are listed below. While it may not seem fair that the bright side is left out, that’s all most people ever see – after all, there’s fame and fortune (in higher stock prices and research grants) to be made from positive press releases. Negative results aren’t news, and across all fields of science, negative results are far less often published than positive results.
There’s been a lot of debate about the technical hurdles to overcome – is there enough uranium, do biofuels have a positive net energy, etc., but there’s been very little discussion of the other hurdles.
Oil can’t be relied on in the future because
1) It’s declining worldwide
2) It’s concentrated in just a few countries
3) Oil supplies are vulnerable to terrorism, supply chain disruptions, and unavailable or too expensive if exporters withhold oil to use at home or drive prices up
Population
Declining energy is only the tip of the iceberg. Population growth is at the heart of the converging issues that the Club of Rome models show bringing ecological collapse between 2020 and 2030. The convergence of global warming, depletion of fresh water, forests, soils, and fisheries; desertification, loss of biodiversity, and contamination of our air, water, and soil with toxins will overwhelm the ability of governments to cope.
There is no energy solution that can support the world’s current population, let alone a population that’s increasing.
Energy is the tipping point. We have already far overshot the carrying capacity of the planet, but cheap and plentiful energy has allowed us to work around many of these issues, for example, by pumping large amounts of clean water from 500 feet.
If it turns out that an alternative energy resource can exist without any fossil fuel inputs, and has a high enough energy content to do significant work, then that energy resource could sustain a certain population, but it will be a much lower number than the current fossil fuel-based civilization. Whatever this energy resource is, it would need to be composed of common metals (rare metals essential to making electronic and solar cells are running out faster than oil), and not much cement, which is highly energy intensive.
Garrett Hardin, in “The Ostrich Factor”, details how a state-level society could keep its population in check without the usual war, starvation, and disease.
The higher the population of a region when the “Limits to Growth” are reached, the harder the fall, and the more environmental damage done.
The environmental and scientific community has been shamefully silent on the issue of population. It’s way past time to speak out.
Economic
Even if a crisis strikes and democracy goes out the window while our government focuses on energy Manhattan projects, it’s not certain that enough public funding and private capital can be raised.
The people with real money aren’t going to invest in alternative energy. They wouldn’t be wealthy if they threw their money away on non-viable projects. Even if they’ve inherited their wealth and believe in perpetual motion, they have advisers who keep them out of trouble. They have viewpoints similar to Peter Huber’s: “For the next several decades at least, alternative energy sources aren’t serious choices; they are pork barrels, delusions, demonstration plants and daydreams. (Huber)
Global trade and just-in-time delivery have too many inter-dependencies which will be easily interrupted by wars, oil shocks, hurricanes, and other disruptions to build new power plants of any kind quickly. Time is critical. As Hirsch pointed out in his 2005 Peak oil study for the Department of Energy, you’d want to start preparing for Peak Oil at least twenty years ahead of time.
Political
Politically, it will be hard to devote money and energy to new projects when people are freezing and hungry. The existing energy is likely to be diverted to agriculture and essential services, the way blood flows to your body’s core if you plunge into icy water.
All of these projects must be done in a time of increasing hardship, which means increasing crime, and the risk that key engineers will be hijacked or kidnapped, requiring local governments to divert increasing amounts of energy to maintaining order.
If wars are being fought over the remaining oil fields, and large naval fleets patrol the seas to prevent piracy and ensure the continued flow of oil, the military will use an increasingly large percentage of the available oil (Bucknell).
Social
There’s a great deal of local opposition to building the following types of power facilities: LNG (Liquid Natural Gas), windmills, dams (hydropower), coal, and nuclear power.
If an enormous project to build new power plants were begun, there wouldn’t be enough engineers and other technical people to staff the projects. This is already a problem in oil and natural gas fields. The existing engineers will be busy keeping infrastructure like water and sewage treatment running.
Psychological
Back in 1981, Commander Howard Bucknell III wrote that the public’s understanding of the energy situation was far removed from reality, because when given uncertain and contradictory information, the public believes what they want to believe.
The public and politicians have always blamed energy shortages on oil company conspiracies or outside enemies, which lessens the urgency to adapt.
Ninety percent of the public is scientifically illiterate, and when you combine that with the psychobabble of the Self-Help and Positive Thinking movements, the public is more likely to think of Peak Oil proponents as pessimists.
Scientists and engineers are paid to solve problems, so they tend to see energy problems as challenges that can be solved.
Denial, techno-optimism
Finally, the implications are so depressing that very few people are willing to contemplate them, or they assume the problems will be solved by someone because human beings are so very clever.
Renewable Energy Sources
Renewable energy depends on non-renewable resources such as (rare) metals, wood, topsoil, and other non-renewable stuff that (topsoil takes 500 years or more to recover from agriculture). This stuff has to be mined, fabricated, and taken to the installation site. Desert solar and geothermal plants use more non-renewable groundwater than nature replenishes. The electricity generated is no longer renewable if it’s delivered across wilderness cut asunder with roads and clear-cut corridors for power-lines.
Nor is the life expectancy of solar panels or wind turbines very long — they don’t last close to as long as a conventional power plant. Dams silt up and use staggering amounts of concrete and steel to build.
The most important reason renewable energy sources will never be able to replace fossil fuels: the energy to build windmills, solar panels, and so on, takes more energy than what is delivered.
Take windmills for instance. When all of the oil is gone, windmills must make more windmills solely on windmill power. Windmill power must be stored to concentrate the power enough to do useful work. So right off the bat, windmills must not only be able to generate enough power to build mining equipment and factories to mine iron ore to make more windmills out of steel with, the windmill is also making batteries from start to finish. Plus all of the components of the electrical grid to deliver the windmill power to customers. All of the components need to be delivered, the people who make the components need to use windmill energy to get to work, and the windmills have of course, made all of the tractors, trains, trucks, and other components of agriculture so the windmill workers don’t go hungry. Now finally, if there’s any extra energy after all this energy expended to make more windmills, finally other people outside of the windmill industry can have some power.
Whatever problems fossil fuels might have, they contain orders of magnitude more energy than renewable sources such as wind, solar, hydrogen, and biomass. Replacing them with renewable energy sources has several major challenges:
1) The main problem facing us is the need for a liquid transportation fuel that can be used in existing vehicles. Solar, nuclear, wind, geothermal, wave, and tidal power don’t address this need.
2) Natural gas made nitrogen fertilizers have allowed up to five times as much food to be grown as could grown otherwise, and that plus mechanization from planting to harvesting, to storing of grain in massive granaries, and oil-based distribution and processing has allowed an extra four to six billion people to exist on the planet than could otherwise be supported. There are no renewable energy sources that can fertilize plants, except for guano, and there are very finite amounts of that. Bat guano used to be so important to farmers that the U.S. Congress passed the Guano Islands Act in 1856. This allowed U.S. citizens to take possession of any guano island in the world not already claimed by another government and empowered the U.S. military to protect them.
3) Most renewable energy (except oils from plants) can’t replace the half million products made from the complex hydro-carbon chains contained in fossil fuels, such as plastic, medicine, paint, pesticide, etc.
4) Renewables such as wind and solar are very diffuse and need large collection areas to capture their energy in real time.
Emergy – Embodied Solar Energy
Bruce Thomson’s definition:
“A solar embodied joule (sej) is one joule of ancient sunshine falling on the earth millions of years ago. The concept enables us to compare different fuels in terms of sun fall needed to produce them in the future when our underground stores of energy have all run out.
We are particularly interested in discovering whether technologies like windmills, solar photovoltaic plants, or other energy generation technologies will actually, in the future, deliver more energy in their whole-of-life than they require to create, maintain, and dispose of them.
It takes 50,000 joules of sunshine falling on plant material in ancient times to create the fossil fuel that today delivers one joule of energy in your fireplace or your car.
When you use the same fossil fuel to create electricity, the efficiency is not 100%. It works out that 170,000 joules of original sunshine are needed to deliver one joule of fossil-fuel based electric heating in your fireplace.
That’s what we mean when we say that the fuel “quality” (that is, the particular type of fuel), is important when trying to determine whether a desired technology is in fact sustainable in a non-fossil fuel future.
When we are adding up the “energy inputs” to the desired technology, we have to use the 50,000 multiplier for each joule of oil or coal or natural gas, but we have to use the 170,000 multiplier for each joule of fossil-based electricity we consume.
Once we have calculated the embodied ancient sunshine joules correctly for each type of input energy, then we can compare that with the output energy to see if we truly get more out than what went into it.
The fatal mistake in almost all net energy calculations in today’s literature, is that people totally disregard the multipliers.
They simply assume there will be joules of fossil fuel available, and count them in as single joules, without any thought that it takes 50,000 joules of solar energy to actually produce those fossil fuels.”
This is also a reason why biofuels are so energy intensive to make – you’re trying to do the work of condensing the energy in plant matter quickly, it’s inherently energy intensive.
Energy Returned on Energy Invested (EROEI)
Do an internet search on this, so much has been written to explain it better than I care go to into. Basically the concept is simple: back when oil was first discovered, it took the equivalent of the energy in 1 barrel of oil to get 100 more barrels of oil. It’s as if you got $100 for every dollar you invested. Most of our infrastructure — clean water pipelines, energy oil and natural gas pipelines, dams, sewage treatment, roads, and so on where built when the EROEI of oil was very high. Now that we’re drilling in very deep offshore water and other remote places, the EROEI is reaching 10, when the price of oil is likely to skyrocket.
Energy Return on Time
Many psychology experiments have shown that people want less money now than more in the future, even if it’s only a 2 week wait. Investors in natural gas can get 70% of their money back in 2 years, versus having to wait 20 to 30 years to get their money back from wind power. No wonder there isn’t more wind power. Nate Hagens explains this in greater detail in Applying Time to Energy Analysis.
http://en.wikipedia.org/wiki/Emergy
The best books and articles to understand in detail the problems with the various kinds of energy are:
Martin Hoffert, et al 2002 Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet, Vol 298
Howard Hayden. 2005. The Solar Fraud: Why Solar Energy Won’t Run the World. Second Edition.
Ted Trainer. 2010. Renewable Energy Cannot Sustain a Consumer Society.
References
Bucknell III, Howard. 1981. Energy and the National Defense. University of Kentucky Press.
Huber, Peter. Nov 27, 2006. Love Uranium. Forbes.
NAS 2009. America’s Energy Future: Technology and Transformation. 2009. National Academy of Sciences, National Research Council, National Academy of Engineering.