Saturday, March 15, 2008

Alternative energy sources

The outlook on energy alternatives to fossil fuels is looking a little bleak.

There have been several recent studies or reports casting significant doubt on the economic and/or environmental viability, at least for the near and intermediate future, of some of the leading contenders to supplant fossil fuels.

First up: nuclear power. Of course, environmentalists and others have had grave doubts about nuclear for decades, because of problems with safe disposal of spent nuclear fuel and the dangers of diversion of enriched uranium to manufacture of weapons. On top of that, there is the argument that replacing generation of power from burning fossil fuels with generation from nuclear sources may well contribute more to release of CO2 into the atmosphere than continuing to use fossil fuels. This comes about because so much power (generated from burning of fossil fuels) will need to be expended simply to build from scratch many new nuclear power plants and sharply increase the mining and purification of uranium:

Nuclear Power Not Efficient Enough To Replace Fossil Fuels, Study Finds
Nuclear energy production must increase by more than 10 percent each year from 2010 to 2050 to meet all future energy demands and replace fossil fuels, but this is an unsustainable prospect. According to a report published in Inderscience's International Journal of Nuclear Governance, Economy and Ecology such a large growth rate will require a major improvement in nuclear power efficiency otherwise each new power plant will simply cannibalize the energy produced by earlier nuclear power plants.

Here's another way to look at this. If you consider just the marginal costs of producing a kW of energy from nuclear fuel vs. fossil fuel – counting (if you can) both direct economic costs and costs due to release of CO2 into the atmosphere – nuclear energy might be superior. However, if you also consider the capital expense (both direct and indirect) required to build enough new nuclear facilities to replace existing conventional facilities and also meet increased demand, then (according to the study) nuclear loses.

So what about using other energy sources as alternatives to fossil fuels, in order to significantly reduce dependency on fossil fuels and release of CO2? Like hydrogen, for example. Of course, this depends on further developing a lot of technology that's either not cost-competitive yet (fuel cells) or not even available yet (practical and safe means of storing and transporting hydrogen). To say nothing of the capital costs (as above) needed to build hydrogen infrastructure if and when the technology is available.

Even if technology can solve the difficult problems of storing and transporting hydrogen, there's another fundamental problem. Hydrogen itself is more of a form of energy suitable for transport and storage than it is a readily available source of energy (like sunlight or fossil fuels) that can be acquired or extracted (relatively) cheaply. There's no hydrogen just sitting around (like natural gas) waiting to be mined and distributed. Energy has to be consumed in order to separate hydrogen from oxygen, which together make up H2O. This energy has to come from some other source, as input to the electrical/chemical process that separates out hydrogen (or recombines it to make another fuel such as methane). This energy is regained later – but always with some percentage loss – when hydrogen is chemically recombined with oxygen (as in a fuel cell).

There really isn't any energy advantage to hydrogen at all, except for the (presumed) advantage over batteries in storage and transport. Of course, energy in a storable form is required for use in vehicles like cars and airplanes, in spite of the unavoidable losses along the way. The following essay goes into all of this in more detail.

The Hydrogen Economy
Skeptics scoff at perpetual motion, free energy, and cold fusion, but what about energy from hydrogen? Before we invest trillions of dollars in a hydrogen economy, we should examine the science and pseudoscience behind the hydrogen hype.

There are some problems with the essay. First, one does not "make" hydrogen. It is extracted from chemical compounds like water, hydrocarbons (fossil fuels except coal), or biomass (carbohydrates, cellulose, etc.). Energy has to be input to the process in order to break the chemical bonds between hydrogen and other elements (carbon or oxygen). You get the energy back out when hydrogen recombines with oxygen or carbon (in a fuel cell, combustion chamber, etc.) – but always at some loss.

Second, the essay mostly assumes hydrogen will be stored and transported in liquid form, which is difficult and expensive, since liquid hydrogen boils at an ultracold -253°C. There is some hope that technology can be developed to store gaseous hydrogen in exotic solid materials at reasonable temperatures and pressures. (Recent examples: here, here.) However, at this point that's still conjectural. The larger point is that a practical "hydrogen economy" is still, at best, not in the near future.

So hydrogen is not an energy source, and it is even very problematical as a way to store energy in a portable form for use in cars and airplanes. Fortunately, there are other ways to make energy portable, such as batteries. A Toyota Prius uses nickel metal hydride batteries to store energy from the regenerative braking system, and it seems to be an economically successful product. Lithium ion batteries, such as are used in laptop computers, have a higher energy density than the nickel metal hydride type. They have problems of their own, but significant improvements are being made. (See here, here, here.)

That still leaves the problem of developing additional actual sources of energy, that are alternatives to fossil fuels. Ethanol (grain alcohol) is getting a lot of publicity these days. It's politically popular with the agricultural industry, for obvious reasons. Ethanol partially solves one problem with fossil hydrocarbon fuels – by removing some dependence on politically unstable areas as a fuel source. But ethanol does nothing for the problem of CO2 emissions.

And it creates serious problems of its own, such as driving up the cost of agricultural products needed to feed people. Further, as with hydrogen, it takes a lot of energy to extract ethanol (or other energy carriers such as other biofuels or methane) from agricultural crops or biomass. Critiques of ethanol and other biofuels are not new, though they don't seem to get the attention they deserve. (See here, here, here, for example.)

Other alternatives? There's always solar (photovoltaic) energy. Of all new but currently available alternative energy sources to fossil fuels (whether oil, natural gas, or coal), solar seems to be the most economical, especially taking reduced CO2 emissions into account.

But of course, solar also has its problems too. These include capital costs for building infrastructure to capture solar energy and to store it (for peak or nighttime use) or transmit it from the sunniest areas with low land prices. It's these capital costs (initial construction and eventual replacement) that hurt, since the marginal cost of each kWh is almost nil.

However, making detailed economic comparisons with traditional energy sources is rather difficult, as this study argues: Cloudy Outlook For Solar Panels: Costs Substantially Eclipse Benefits.

It would seem that the real difficulty of economic analysis lies in predicting the future costs of conventional energy sources – fossil fuels, especially oil. Some of the problems:

  • How to estimate costs associated with CO2 emissions, given that the idea of global warming itself is so controversial (especially in the minds of economists and political officials, if not atmospheric scientists). To say nothing of estimating social costs of conjectural side effects, such as sea level rise, serious water shortages, detrimental impact on human and animal health, impact on agricultural production, etc.
  • How to estimate the foreseeable rise in price of fossil fuels (especially oil) due to political instability, rising extraction costs (deep ocean sources), depletion of supplies, and rapid increase in demand from developing parts of the world. (There are large uncertainties in all of these factors, and some cost has to be allocated to this uncertainty itself.)
  • How to handle the issue of proper pricing for energy at times of peak demand, as opposed to off-hours. (The report just mentioned discusses this.)

At present, the cost of solar energy, taking into account such things as installation costs, depreciation, etc., might well be two to four times the cost of energy from fossil fuels. But at least the cost of solar is pretty certain to decline, while the cost of energy from fossil fuels can only increase – and at a worrisomely unpredictable rate, in view of the uncertainties just listed.

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Blogger Pseudonym said...

The take-home message is that the future of energy will not be one-size-fits-all. There is no one answer, because no one technology can do the job by itself.

3/15/2008 06:14:00 PM  
Blogger Nikhil Rajwade said...

Craig Venter talks about fuel from synthetic life forms - check it out at

3/19/2008 06:58:00 AM  
Blogger Charles Daney said...

"Craig Venter talks about fuel from synthetic life forms"

I wonder how well this will actually work. There's no free lunch. Suppose the end result of the organism's metabolism is methane (CH4).

You get energy out of that by burning it, which is a chemical reaction that combines CH4 and oxygen (O2), yielding CO2 and water (H2O).

But the synthetic life forms essentially make methane by the reverse chemical reaction that makes CH4 and O2 from CO2 and H2O. That has to consume at least as much energy as could be released by burning CH4. Where does *that* energy come from?

Plants already do this sort of thing using photosynthesis, which is driven by energy from sunlight. If these synthetic life forms do the same, will they be more efficient than existing photovoltaic technology? Keep in mind that it takes energy and money to manufacture solar cells, and that will also be true of manufacturing the synthetic life forms. (Otherwise we'd already be getting "free" energy using solar cells.)

3/19/2008 11:44:00 AM  
Blogger Charles Daney said...

Here's another approach to producing a more manageable fuel than hydrogen from CO2: Synthetic Fuel Concept To Steal Carbon Dioxide From Air.

Like Venter's idea, this would yield a fuel in liquid form that could be easily used in cars and aircraft. Of course, cars can also run off batteries (if they get better than they are now), which in turn are charged (eventually) by solar-generated electric power.

Either way, it's necessary to get an efficient way to extract CO2 from the atmosphere.

What's best in the long run depends entirely on what process turns out to be most efficient, when all costs are considered.

3/19/2008 10:07:00 PM  
Blogger Keith said...

Your blanket statement "So hydrogen is not an energy source" shows a bit of bias. Hydrogen must be considered. It's abundance dictates that we must find ways to make it safe and practical. Even if that's not easy...

3/20/2008 09:25:00 AM  
Blogger Charles Daney said...

Your blanket statement "So hydrogen is not an energy source" shows a bit of bias.

Nope, not a bias. The idea that hydrogen isn't an energy source is explained in the article on the subject that I linked to. Did you read it?

In short, hydrogen isn't a source of energy, because more energy has to be expended in order to liberate hydrogen from water than can be recovered by burning it. This is a fact of chemistry and physics, not an opinion. The situation would be quite different if elemental hydrogen were sitting around where we could gather it relatively cheaply. This is the case with oil today, though the cost of extracting oil keeps increasing as we use up the most easily accessible reserves of it.

At some point, there will still be plenty of oil left, but trapped in deposits where more energy has to be expended extracting the oil (with known technology) than can be recovered by burning it.

It is this problem (along with CO2 emissions) that puts us in the serious bind we are in energy-wise.

Hydrogen must be considered. It's abundance dictates that we must find ways to make it safe and practical. Even if that's not easy...

Hydrogen should be considered, and it is being considered. However, there's nothing that guarantees it can be made "safe and practical" (compared to the alternatives), no matter how much we wish it to be so.

The principle of "fuel cells" was discovered in 1838, and the first working example was made in 1843. Fuel cells are the main way (though not the only one) envisioned for using hydrogen to make electicity. Yet after more than 160 years fuel cells still are not cost-competitive with batteries for most purposes (especially if hydrogen is the fuel).

3/20/2008 10:56:00 AM  

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