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Around 1991 a trades foreman in Longview, Washington, asked me seriously if I believed in global warming. Lots of folks don't, or say they don't, especially political conservatives in the US these days. I didn't have much of an answer for him at the time, but I've been reading and thinking about it ever since. For whatever it's worth, here's what I think.
What we know for sure: we are definitely increasing the concentration of carbon dioxide in the air, well beyond anything that's happened in the past. CO2 data here is from the Carbon Dioxide Information Analysis Center, part of Oak Ridge National Laboratory. The direct measurements at Mauna Loa started in 1958.
For some years now we've known the prehistoric CO2 concentration back to about a hundred thousand years ago, from deep ice cores from Antarctica; they have trapped air bubbles, and the deeper the core, the longer ago the air was trapped. There have been oscillations, but they range between around 180 ppm and 300 ppm, with an average of about 230 ppm. As you can see, we were already well above 300 ppm in 1958. The Wikipedia article Climate change mitigation has lots of good graphs too.
We also know for sure that carbon dioxide is a greenhouse gas: more CO2 in the air tends to trap more heat. That's basic physics.
It's become clear that polar ice sheets and pack ice, boreal permafrost, and glaciers everywhere are all in accelerating decline.
Now for the big question:
| Q. A. |
What happens next? Nobody knows. |
Some people think we are still in the middle of an ice age, that the eighteen thousand years or so since the last glaciation is just a sort of geologic-time coffee break. Others have suggested that ice ages might have been triggered by the collision of the Indian subcontinent with Asia, and the resulting uplift of the Himalayas and Tibet. Mountain-building tends to produce an increase in chemical weathering of rocks, which among other things tends to remove CO2 from the air and deposit it in the sea floor as carbonates. The Himalayas are still getting pushed up, slowly. The Andes of South America, almost five thousand miles long, are going up faster, driven by the Ring of Fire, and may even surpass the Himalayas in altitude above sea level eventually.
One dire possibility is the collapse and melting of the West Antarctic ice sheet. It's grounded on bedrock that's below sea level, and therefore potentially unstable. It's known that it's been gone before in geologic time. If it happens it could produce a 30-foot rise in sea level. This would require massive rebuilding of all seaports with major economic impact. It would also wipe out every ocean beach in the world. If the Greenland ice cap goes that could raise sea level 20 feet; or they could both go. I'd advise against investing in real estate anywhere within fifty feet elevation or so of sea level: it may end up underwater.
Global dimming is a more recently discovered effect due to soot and other atmospheric particulates, from things like coal power plants, wood cooking fires in Africa, volcanic eruptions, and even combustion products from cruising airliners. These particulates block some sunlight and produce a cooling effect, that tends to offset warming to some extent. For example, during the few days after 9/11 when US air traffic was grounded, an increase in average temperatures was observed. As countries like India and China industrialize and raise their standard of living, they will want to adopt pollution controls for health reasons, similar to those already in place in America and Europe, and this may tend to exacerbate global warming.
Bottom line: we still don't understand how the Earth's climate works very well at all, including how and why there are variations, and we are basically conducting a sort of giant middle-school science project on our whole planet, without any clear idea of the results.
I think we need to substantially reduce our CO2 emissions.
Two top-priority things I think we should do:
It looks like relevant technology is at hand. My picks:
Geoengineering is the term for various brute-force approaches to combating global warming, sort of in the same spirit as combating summertime warming of your house by cranking up the air conditioning. Proposed schemes include physical sunshades in space (probably at the Sun-Earth L2 Lagrangian point, between the Earth and the Sun but about four times farther away than the Moon) distributing artificial sulfur particulates in the upper atmosphere, fertilizing ocean algae with tons of iron particles, and multiple massive industrial plants to extract CO2 from the atmosphere and sequester it, perhaps by pumping it underground. All such schemes tend to be extremely expensive. We may end up having to do some of that stuff.
Fast-neutron reactors could extract much more energy from recycled nuclear fuel, minimize the risks of weapons proliferation, and markedly reduce the time nuclear waste must be isolated. ("Smarter Use of Nuclear Waste," Scientific American magazine, December 2005)
The article Smarter Use of Nuclear Waste in the December 2005 Scientific American proposes generating power with large fast-neutron reactors, and recycling spent fuel using pyrometallurgical processing. This system would produce about sixty times (60×) as much energy from available fissionable materials such as uranium and plutonium, compared to the thermal (moderated) reactors now in use, and would turn most of what we now categorize as nuclear waste into fuel. "Spent" fuel removed from current thermal reactors actually still contains about 95% of its energy potential. The article says that if existing thermal reactors are replaced with fast reactors as they reach the end of their lifetimes "there would be no need to mine any more uranium ore for centuries."
This system of fast reactors and reprocessing would produce about 1% the quantity of waste current thermal reactors do for the same energy output, and what little waste is produced would require secure storage for a few hundred years, not tens of thousands as with current technology.
It's also stated in the article and other places that if an attempt were made to meet the world's emerging power needs by merely building more thermal reactors, because of their relative inefficiency, the world's entire finite supply of uranium could be exhausted, in thermal-reactor terms at least, in a few decades.
See also the Fast Neutron Reactors page on the informative World Nuclear Association site, the Wikipedia article Fast neutron reactor, and the Advanced Reactor Development and Technology pages at Argonne National Laboratory.
Criticism of this proposal seems to focus mostly on the reprocessing being potentially dangerous, and the bare fact that plutonium is produced. When reading such criticism, I think one should pay as much attention to the source as to the content.
Many industrial processes are potentially dangerous if design, construction, operation, and maintenance are not competently executed. Use of chlorine gas in paper mills to bleach wood pulp for white paper comes to mind (buy the brown coffee filters, not the white ones, please). In the 1984 Bhopal disaster in India, 42 tons of methyl isocyanate and other poisonous gases were released from a Union Carbide pesticide plant, with an eventual death toll on the order of 15,000. More than a thousand people were killed in chemical plant accidents in the US in the second half of the 20th century. Nobody has ever been injured or killed in the US in a nuclear accident involving radiation exposure.
Apparently plutonium for nuclear fission weapons has to be essentially pure 239Pu (the isotope plutonium 239) but plutonium produced in breeder reactors will always be a mixture of several isotopes of plutonium, and the Carter administration decision not to reprocess nuclear fuel was based more on appearances and perception than reality. Other countries such as France, Japan, Russia, and the UK are already reprocessing nuclear fuel, and China and India have announced their intent to build fast-neutron reactors.
Traveling wave reactors are a variation on the fast-neutron theme which can also use so-called "depleted" uranium as fuel to generate power. In June 2010 CNET News reported that Bill Gates had invested significantly in TerraPower, a Seattle company developing designs for traveling wave reactors. The Wikipedia TWR article linked above cites a US stockpile of 700,000 metric tons of depleted uranium, and says that "wide deployment of TWRs could enable projected global stockpiles of depleted uranium to sustain 80% of the world’s population at US per capita energy usages for over a millennium."
University of Houston physicist David Criswell has a proposal to generate photovoltaic solar power on the Moon, and beam microwave power to rectennas on the Earth surface. This idea is somewhat similar to solar power satellites proposed in the 1970s by the L5 Society, except as Dr. Criswell puts it, we don't have to build the Moon. Ninety percent of the lunar bases would be built from lunar materials.
See also these links:
More content about lunar solar power can be found with searches on Google or other Internet search engines on "Lunar Solar Power" or "David R. Criswell."
An aspect some fail to consider when thinking about options for generating electric power is demand from emerging nations that were part of what used to be called the Third World. Obviously the two major national impacts in terms of population are China and India, but we have to expect this phenomenon everywhere at some point, including Africa, South America, the Middle East, and central Asia. This is a big reason why just building more thermal/moderated nuclear plants as we know them today is not a viable option. I believe one assumption Dr. Criswell used in his study of the lunar solar power scheme was generating two kilowatts for each of the 10 billion human beings expected to be alive in 2050, a total of 20 terawatts.
We Americans built lots of hydroelectric dam projects in the twentieth century, especially in my Pacific Northwest part of the country. We've benefited from the cheap power, but we've also learned that dams are a Faustian bargain.
Unfortunately, many countries are now ignoring our experience and repeating our mistakes.
America still has a lot of coal in the ground, and we built a lot of coal-fired power plants, which is why our Eastern forests, lakes, and streams have acid rain problems. In the US we still get about half our grid power from coal, and I think that needs to change. We used to heat our houses with it. China also has a lot of coal. So-called clean coal refers to efforts to design coal power plants that mitigate some or all of the pollution problems. Designing a really clean coal plant is not an easy proposition, because of the long list of bad stuff you get when you burn coal, either as combustion products or just released from the coal as it burns:
Many people would say there's no such thing as clean coal. It's certainly possible to reduce emissions of sulfur dioxide, nitrogen oxides, and particulates, and that's definitely worth doing, as long as we still have coal plants. Farther down that bullet list it gets harder to improve things. I think it's worth some experimentation, but I'm not optimistic.
GreenFuel wants to install algae farms at big coal, oil, and gas burning power plants. Flue gas output from the plant is bubbled through sunlit transparent tubes containing water and algae, and the algae consume CO2. Algae species are selected that don't accumulate heavy metals or other bad stuff, and consistent with the flue gas composition and desired products. The water is recirculated in a closed loop, and the algae are harvested daily. Lipids, carbohydrates, and protein in the dried algae can be used to produce biofuels or contribute to feed for livestock. The kicker: to remove a maximum of 40% of the CO2 from an average size 655MW power plant requires an algae farm of 3400 hectares or 13.1 square miles; or for a 5.2% reduction at the same plant size (a number from the 1992 UN Kyoto Protocol) 420 hectares or 1.6 square miles.
Terrestrial solar power is being worked on intensively, both photovoltaic solar panels and thermal solar power, in which sunlight concentrated by a parabolic reflector heats a circulating working fluid such as a synthetic oil, which is used to make steam and drive turbines. There are also thermal solar rooftop panels that can provide heat and hot water for houses and other buildings.
Ordinary solar cells only produce power from the red part of the sunlight spectrum. Multijunction cells use layers to convert several wavelength bands to electricity, but cost more to make. The very successful Mars rovers Spirit and Opportunity have multijunction solar arrays.
Concentrated photovoltaics use a reflector to focus sunlight on a solar cell, sometimes a multijunction cell. Depending on the level of concentration (measured in suns) sometimes the cell has to be liquid cooled. People are even trying to figure out how to combine photovoltaic and thermal generation in the same concentrator apparatus.
Single-layer full-spectrum cells may be possible, in which one layer produces power from the entire solar spectrum, infrared through ultraviolet. Dye-based technology may give us very inexpensive solar cells; another way to get lots of solar installed is to make it really cheap up front, even if it's maybe a bit less efficient.
Big wind turbines going up everywhere it's windy have become a familiar sight. Tidal power and wave power are getting their engineering worked out. Places like Iceland, the Philippines, and Chile that have suitable geology and economics are benefiting from geothermal, although the engineering tends to be troublesome. Anaerobic digestion in landfills produces methane gas, which definitely should be collected and burned to produce power, rather than released. (In this case we're better off releasing the CO2 than the methane.)
All these green alternatives are great, and should be encouraged with incentives. We should use them everywhere we can. But ultimately they are too thin, there isn't enough of this kind of power. It would be wonderful if we could run America exclusively on solar panels and windmills, but we can't.
If you do invest in your own power generation, on your house or on a commercial building, in many places you can benefit from net metering. When your power installation is producing electricity you're not using, maybe because you're in Hawaii at the moment, it gets put on the grid for others to use, and your utility pays you for it. In fact usually your electric meter just runs backwards.
SunEdison is an innovative energy company that contracts with owners of large flat roofs, such as supermarkets and distribution centers. SunEdison pays for the solar photovoltaic installation, and the customer contracts to buy the power at a fixed rate for 20 years. Large utilities often charge more for power during peak demand periods, hot sunny days when air conditioning demand spikes, which is also when on-site solar is producing the most power. They say that if all such flat roofs in a city were so equipped, it would probably cover 20-40% of the whole city's peak power needs.
Biofuels are produced from renewable plant sources. Because they're produced from plants, depending on process details, the carbon dioxide released when they are burned can be roughly equal to the CO2 taken up by the growing plants, and the whole cycle therefore carbon-neutral.
Ethanol (grain alcohol, C2H5OH) is a familiar first-generation biofuel already in use, typically produced from corn in the US and from sugarcane in Brazil, more or less the same way one makes vodka or whiskey. Ethanol can be used as fuel by itself, or more commonly in various blends with conventional gasoline. Ethanol for fuel is subsidized in the US, leading to political complications, but is controversial, partly because it's being produced on arable land from crops with sugar content, which could also be food for people or feed for livestock. To put it another way, this is diverting part of our finite food-producing capacity to produce fuel instead.
Vegetable oils can be used as fuel in diesel engines, including oils produced for use as fuel, and recycled vegetable oil previously used for deep-frying food. Obviously there's going to be a limited amount of used deep-fryer oil available, but if I owned a restaurant with a deep fryer I'd probably want to look into it. They say the exhaust smells like french fries.
Cellulosic ethanol second-generation biofuel is ethanol produced from materials containing cellulose rather than sugars, by means of engineered bacteria. Cellulose makes up the structure of the woody parts of plants; sources include grasses that can be grown on land not usable for food crops, and woody wastes from crops, things like corn shucks, corn cobs, wheat straw, and bagasse, the fibrous residue from sugarcane processing. Cellulosic materials can also be digested by ordinary bacteria to produce methanol (wood alcohol, CH3OH) which can be used as fuel but has low energy density. Methanol is also poisonous, which is why your windshield washer fluid usually has dire warnings on the jug.
Third-generation biofuels or algae fuels are based on lipids and carbohydrates from algae, rather than coming from ordinary plants grown in soil. Algae only requires sunlight, water, and some nutrients, not arable land, and treated wastewater or even seawater can be used. Since the source of fossil petroleum is ancient plankton and algae trapped underground, algae fuel can be viewed as just speeding up the process. The Algal Biomass Organization is a consortium formed by Boeing, several airlines, and some biotech companies, to promote development of algae-derived biofuel for aircraft, and there's already been a demonstration flight. If they can make it practical in quantity for jet fuel, they ought to be able to produce everything from gasoline and diesel fuel to butane for your lighter.
Some people advocate a total conversion to a hydrogen economy, with hydrogen fuel generated from renewable sources, and delivered among other things for use in hydrogen vehicles, internal combustion or fuel cell. Hydrogen vehicles emit only water vapor. Hydrogen in either an engine or fuel cells can provide the other power source in various hybrid car designs, as is proposed as an eventual option for the GM E-flex platform. Fuel cells have to be kept above freezing to work, which is obviously problematic for vehicle applications in cold climates. Critics also suggest that hydrogen fuel cell cars are actually less efficient than battery electric cars.
It looks like it may be possible to split water to produce hydrogen using sunlight, either by means of catalyst chemistry in a photoelectrochemical cell or by manipulating algae. Apparently some strains of algae can be made to produce hydrogen instead of oxygen just by making sure they have no sulfur in their environment. Hydrogen would be produced and stored during the day, and then used in fuel cells to produce power at night. This notion of distributed hydrogen generation is a lot more appealing than building a whole new US infrastructure for centrally generated hydrogen; estimates for that run from 20 billion dollars to as high as 500 billion.
Current experimental hydrogen fuel-cell and internal-combustion vehicle prototypes generally get their hydrogen from compressed-hydrogen tanks, but such tanks probably can't store enough energy for practical use. Even liquid hydrogen has energy-density problems, assuming you could cope with the engineering and safety problems; a gallon of gasoline actually contains more hydrogen than a gallon of liquid hydrogen. It may be possible to store hydrogen at higher densities absorbed or bonded to solids in the form of powdered metal hydrides or other solid materials.
Everyone thinks of the 1937 Hindenburg disaster whenever hydrogen is mentioned, and certainly hydrogen is easily ignited. When a gasoline vapor fire happens after a car crash, it tends to involve a horrible puddle of fuel incinerating the wreckage from underneath. Even if a hydrogen leak ignites, because of hydrogen's buoyancy the fire tends to stream up away from things. This effect is even visible in flim of the Hindenburg disaster. Hydrogen also presents potential engineering issues, but solutions are already in hand, and it's already been demonstrated that hydrogen can easily be used as fuel in either conventional internal combustion engines or in turbines.
An electric car uses an electric motor or motors for propulsion, instead of an internal combustion engine or something else. What we mostly think of as an electric car is more precisely a battery electric vehicle, in which the energy comes from a rechargable battery pack, rather than another source of electrical energy such as a flywheel or supercapacitors. Battery electric vehicles have been built using lead-acid, nickel metal hydride (NiMH) and lithium-ion batteries, in various designs with and without transmission gearing, and with different speed and range capabilities, including some with supercar-level performance. In some designs electric motors are built right into the wheels, increasing efficiency.
People tend to worry about the limited range of pure electric cars; this is sometimes called range anxiety. Once we have lots of electric cars around, there will be a simple piece of technology readily available called a genset trailer, perhaps even for rent. It's just a small trailer, containing a ten-gallon or so fuel tank, small efficient internal-combustion engine, and electric generator, with a fat cable you plug into the back of your electric car. You can think of it as a Honda generator on a dinky trailer chassis. Hitch one to your puny electric, and you've temporarily converted it into a gas-electric series plug-in hybrid, with unlimited range as long as you don't run out of gas stations.
A hybrid electric vehicle uses an electric motor in some combination with another type of engine, usually an internal combustion engine (hereafter engine). In parallel hybrids, currently the most common type of hybrid car, both the engine and the electric motor are connected to the transmission somehow. There are a lot of ways to design parallel hybrids. In a series hybrid the engine isn't directly connected to the transmission, but drives an electric generator. The generator can both charge the battery and provide power to the electric motor. Familiar diesel-electric locomotives are series hybrids; the GM E-flex platform is battery-dominant series hybrid. In series hybrids the engine always runs at its most efficient speed, and can be designed for that. There seems to be increasing interest in using turbine engines in series hybrids. See also the hybrid cars article at howstuffworks.com.
Plug-in hybrids are designed to have their battery recharged overnight, and operate as a pure electric vehicle most commute days, within a certain mileage range between charges. Beyond that range the engine starts and the vehicle switches to a hybrid mode. A disadvantage of plug-in hybrids is the engine and fuel tank are being hauled around at all times, including normal commute days when the hybrid mode isn't used. On the other hand, you're not going to leave them behind on a day when it turns out you shouldn't have, as is possible with a genset trailer.
A supercapacitor is an advanced type of capacitor with orders of magnitude higher energy density. Capacitors can charge and discharge much faster than chemical batteries, and should have a much longer service life. They can be used to facilitate collection of electrical energy from regenerative braking in electric vehicles and hybrids, and to provide extra power for quick acceleration, in circumstances like freeway on-ramps and passing. It might also be advantageous for genset trailer designs to include a supercapacitor. There's also some suggestion that it may be possible to reach energy densities that would allow supercapacitors to replace chemical batteries entirely. If that happens, we could have pure electric cars or plug-in hybrids that recharge about as fast as a gasoline car filling up at a pump.
Lightweight fiber-polymer composite-based car construction improves on conventional steel, regardless of power source, because the powerplant has less weight to move around and therefore requires less energy. Composites don't rust, can be stronger than steel and extremely tough, and composite panels can essentially snap together to form the car body. The Rocky Mountain Institute in Colorado had a Hypercar initiative that explored improved composite construction methods for car bodies, and RMI's composite techniques were spun off as Fiberforge. The Aptera 2e streamlined three-wheel two-seater electric car uses composite body construction and is nearing production. They're to be sold and serviced only in California initially; eventually they intend to also offer a plug-in series hybrid Aptera 2h. They have a great look, with a teardrop main body, separately faired wheels, and gullwing doors.
Hobbyists and companies do electric vehicle conversions, starting with a former internal combustion car, or with a conventional car supplied new without internal-combustion drivetrain components (called a glider) or sometimes based on kit cars designed for conventional drivetrains. It's quite possible to make electric muscle cars, and there's even electric drag racing under the auspices of the National Electric Drag Racing Association (NEDRA).
In the late nineteenth and early twentieth centuries, many cities in Europe and America had electric streetcars powered by overhead wires, and the Europeans wisely kept theirs. In America after WWII we shortsightedly did away with ours,* and many cities here are now building light rail at great expense. To be fair, modern light rail typically has higher capacity and speed than the old streetcars, and mostly runs on separate right-of-way rather than on the street, where collisions with other vehicles and pedestrians are possible.
Bus systems in some US cities, including King County Metro in the Seattle area, have overhead-wire electric buses running on tires, on certain routes. When I lived in Seattle in the 1980s, there was a particular very steep street on the south side of Queen Anne Hill that was run as an electrical funicular: an electric bus descending the hill would generate most of the power for another one going up at the same time.
Hydraulic hybrid vehicles (HHV) store energy in a hydraulic system rather than an electrical battery. Generally there's a steel cylinder partly filled with nitrogen gas, into which hydraulic fluid is pumped, compressing the nitrogen. Energy is recovered by valving the hydraulic fluid back out of the cylinder. Due to weight and bulk this system works better in somewhat larger vehicles; UPS is experimenting with HHV delivery vans. There have also been similar systems based on compressed air.
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