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July 27, 2007

Mythbusters: What about Liquid Coal?

Category: Mythbusters – Dan 5:47 pm

Wow. There’s been so much press lately about liquid coal. Between “liquid coal” and “clean coal”, there’s almost a buzz, especially among non-technical people. Gee, this stuff sounds great.

OK, my analogy for “clean coal” is it’s as if you referred to sewage that’s had 90% of the feces removed as “clean water”. I suppose it would be legitimate to call it “cleaner“, but I can’t see anyone wanting to drink it.

Liquid coal, is in almost every way even worse. In the August 2007 issue of Scientific American, there’s an article that dispassionately goes down the many reasons.

  • One ton of coal produces only two barrels of fuel
  • Besides the CO2 produced while using the fuel, the production process creates almost a ton of CO2 per barrel.
  • MIT researchers estimate it will cost $70B to buile enough plants to replace 10% of US gasoline consumption.

The article concludes as follows:

The country would be spending billinos in loans, tax incentives, and price guarantees to lock in a technology that produces more greenhouse gases than gasoline does. This is unacceptable at a time when leading scientists from all over the world are warning that greenhouse gases must be cut by at last 60 percent over the next half a century to avert the worst consequences of global warming. Instead of spending billions to subsidize a massively polluting industry, we should be investing in efficiency and in renewable energy technologies that can help us constrain global warming today.

What’s the deal? Isn’t this obvious? Unfortunately, too many senators come from states where coal production is a major economic force, and a major campaign contributor. These members of congress talk (generally not understanding the technical details) about both “clean coal” and “liquid coal” being solutions. Know the facts here, folks. Not clean. Not smart. Liquid coal? Consider that the title of the SciAm article is “Worse Than Gasoline”…

April 3, 2007

Mythbusters – Hydrogen will fuel our cars?

Category: Hydrogen,Mythbusters – Dan 4:02 pm

I guess my blog entry on hydrogen for transmission and storage created a bit of confusion regarding the most common “talk”, that is hydrogen to power cars. To wit:

Hydrogen Can Provide Long-Term Energy Security Through Use Of Diverse Domestic Resources. The President’s Hydrogen Fuel Initiative and the FreedomCAR partnership will reduce America’s need for imported oil and help clean the air by aiding the development of hydrogen fuel cells and affordable hydrogen-powered cars. Together, these two initiatives constitute a commitment of $1.7 billion over five years.[1]

This was directly off the whitehouse.gov website. I suppose the good news here is that, in more recent white house documents[2] the President isn’t talking so much about hydrogen and cars.

So let me go on record as saying that, in terms of an automotive fuel, hydrogen is a dumb idea. This is a myth that needs to be dispelled. There are better alternatives, both for the near and long term.

Hydrogen – The Perfect Fuel?

But wait? Isn’t hydrogen the perfect fuel? Consider:

  • Abundant – Hydrogen is the most abundant element in the universe
  • Clean – Hydrogen burns clean – no carbon dioxide will come out of your tailpipe
  • Easy electricity – Feed hydrogen into a fuel-cell stack and you get clean electricity
  • Powerful – Pound for pound, hydrogen has three times the energy of gasoline

What’s not to like?

Major technical hurdles for automobiles

Technology review just did an article on the BMW “Hydrogen 7”, a prototype hydrogen vehicle. Their conclusion:

In the context of the overall energy economy, a car like the Hydrogen 7 would proba­bly produce far more carbon dioxide emissions than gasoline-powered cars available today. And changing this calculation would take multiple breakthroughs–which study after study has predicted will take decades, if they arrive at all. In fact, the Hydrogen 7 and its hydrogen-fuel-cell cousins are, in many ways, simply flashy distractions produced by automakers who should be taking stronger immediate action to reduce the greenhouse-gas emissions of their cars.[3]

BMW's Hydrogen 7 Sedan
“BMW’s Hydrogen 7 Sedan”

Why such a negative quote? Let’s consider the current technical realities:

The “hydrogen tank”

We take filling up the tank with gas for granted. Don’t smoke, leave your phone in the car, try not to spill any, and don’t top off. Otherwise, you end up with 10 to 20 gallons of fuel that, at normal temperatures, can sit in your tank for months, propel your car for 300 miles or so, and is relatively unlikely to leak or blow up.

What’s the hydrogen tank alternative. The April’07 issue of Scientific American just did a comprehensive article on “Gassing Up with Hydrogen”[4] that looked at five different technologies for on-board hydrogen storage. The problem is that, although hydrogen, pound for pound has three times the energy content than gasoline, at normal temperatures and pressures hydrogen has only 1/3000 the energy density of gas: a 20 gallon tank of hydrogen would only propel your car about 500 feet!

The solution will fall into one of three categories:

  • Compressed hydrogen – Simple. If hydrogen has 1/3000 the energy density of gas, then compressing it 3000 times should solve the problem. Except that would require pressuring the tank to over 40,000 psi — 8 to 10 times the pressure of a good scuba tank. While theoretically possible, this requires both new advances in tank technology, special protection so the tank isn’t ruptured in an accident, and a means of providing ultra-high pressure hydrogen at the filling station.
  • Liquified hydrogen – To maximize density, you can liquify hydrogen. In liquid form, hydrogen has about 30% of the energy density of gasoline, so you’d need a tank that was roughly 3 times as big for the same fuel range. Hydrogen liquifies at -253°C (about -420°F). The challenge; you need lots of insulation, it takes lots of energy to cool hydrogen to this temperature, and you’ll constantly loose fuel as it slowly boils off. And there are additional challenges at the filling station. Spill gas on your hands and it smells bad. Spill liquid hydrogen on your hand, and you can snap off your fingers.
  • Chemical compaction – The third means of storing hydrogen is to leverage the fact that hydrogen, when bound to the right materials, packs even closer than with liquid hydrogen. There is intensive research in this area. One promising area, tmetal hydride’s, have attained hydrogen capacity of 2% of the total material weight. Unfortunately this still means that you’d need a 1,000 lb fuel storage system for a 300 mile driving range.

There is another option to have on-board hydrogen — you can generate it on board from natural gas or gasoline. While practical in many ways, this produces just as much CO2 as you would with a traditional natural gas or gasoline powered car.

The bottom line here: this is a big problem, and will remain so without some major technical breakthroughs.

Running your car on hydrogen

Once you’ve stored your fuel, you can consume it and drive around. There are two basic approaches here: burning the hydrogen in something resembling a conventional internal combustion engine, or converting the hydrogen to electricity in a fuel cell to drive electric motors.

The BMW Hydrogen 7 burns hydrogen in a fairly standard engine. Indeed Ford is now producing hydrogen internal combustion engines[5]. This technology is relatively feasible today. This approach can create better potential acceleration and a more thrilling ride, but it’s way less efficient than using fuel cells and electric motors.

The alternative is to create an electric car and include an on-board fuel-cell stack to convert the hydrogen to electricity. While elegant in concept, creating small fuel cells that work at normal temperatures without major compromises is a big challenge[6].

Hydrogen infrastructure

Hydrogen cars need to “fill up” at hydrogen fueling stations, which means we need infrastructure to generate hydrogen and distribute it on a widescale basis. Currently, the most inexpensive way to generate hydrogen on an industrial scale is to strip it from fossil fuels[3]. From the standpoint of global warming and carbon reduction, this of course makes no sense, as what remains from this process is CO2. The alternative is to split hydrogen from water, which requires electricity. At the point where we have extensive renewable wind or CSV generation capacity, this might be cost effective, but it’s certainly not today.

Distribution is another challenge. One proposal to solve this problem is to generate hydrogen from natural gas, which already has a distribution network. This however means that you’re creating CO2; if you’re going to do this, it would make more sense to run cars directly off the natural gas.

As with the challenge of storing hydrogen on board, the hydrogen infrastructure is a big problem.

Smarter alternatives

Are there better alternatives to hydrogen powered vehicles? Absolutely. Let’s look at this from a rational engineering perspective:

First, what makes sense to maximize efficiency? While internal combustion engines have seen major improvements over the decades, they are still an inefficient power suource. The most efficient gasoline powered car ever made was perhaps the 1003 Honda Civic VX, EPA rated at 51 mpg, yielding an efficiency of 0.52km/MJ (MJ = megajoule, a quantity of energy)[6]. Compare this with the estimate for the soon-to-be-released Tesla Roadster (an all-electric car), which has an estimated efficiency of 2.18 km/MJ – over four times as efficient as the Honda. The point is that electric motors are far more efficient for powering vehicles than internal combustion engines.

Second, what’s the best way store energy on the vehicle? Note that “Best” is a subjective term, and it’s tied to infrastructure issues (it’s easy to buy a gallon of gas down the street; the same cannot be said for H2), the design question of consider how far you want to go before refuelling, and the engineering question of what form do you want the energy in? (Gas may be a great fuel, but you can’t run an efficient electric motor on gas). Gasoline and diesel are best in terms of energy density (12.2 KWh/kg and 13.7 KWh/kg)[7]. Ethanol is an acceptable liquid alternative at 7.8 KWh/kg. Batteries have much lower energy density, at best a bit over 0.1 KWh/kg.

Third, what’s the best source of the energy? This also has the subjective “best” issue. I’ll argue that best in this case includes flexible, and for that reason, electricity is the best energy source, because we can create it in a variety of ways, and there’s an infrastructure already in place to deliver it.

OK, too many words. What does this mean in terms of the best approach for automobiles. Given these three points, and wearing my engineering hat. I’ll argue that the best approach is:

  • Electric motors – They are the most efficient
  • A plug-in hybrid architecture – It’s allows the use of electricity for modest trips without the range and fast fueling limitations of an electric-only car
  • Ethanol as the on-board liquid fuel – Ethanol (especially over time) can be generated from non-fossil sources, it has a reasonably high fuel density, and the current fuel delivery infrastructure can evolve fairly smoothly to support this

Conclusions?

This was a mythbuster. This post has lots of data, and it may have some controversial points, but my bottom line is that hydrogen as an automotive fuel is a non-starter. Does anyone disagree?

March 30, 2007

Mythbusters – Hurdles remain for Plug-In Hybrids?

Category: Efficiency,Mythbusters – Dan 9:05 am

Argh. Yet another fountain of misinformation slowing adoption of what should be a no brainer technology. In this case, I’m referring to the forces aiming to divert attention on plug-in hybrids.

In an earlier post, I talked about why plug-in hybrids are a hot technology. Clearly I’m not the only one with this point of view. Look at what Austin Energy is doing in Texas.

Under the direction of the Austin City Council, the City of Austin and Austin Energy are leading Plug-In Partners, a national campaign to demonstrate to automakers that a market exists today for plug-in hybrids.

This initiative was recently written up in the Wall Street Journal (look here for a copy of the article where you don’t need a subscription to view). This is great news in terms of spreading the word, but the article is full of industry misinformation…to quote:

Big hurdles remain. The cars require expensive lithium-ion batteries that haven’t been perfected.

“Plug-ins will have a niche market,” says Red Cavaney, president of the American Petroleum Institute, which represents the oil industry. “They’re certainly not going to replace the family car.”

Critics of plug-in hybrid technology generally attack on three fronts:

  • The battery technology isn’t there
  • The costs will be too high
  • It shifts polution to dirty coal fired facilities

Let’s look at each of these in turn…

The battery techology isn’t there

I’ll start by arguing that, although the perfect solution isn’t here, there are good enough solutions in place. The real question is “how far do you want your plug-in hybrid to go before the engine comes on?”. Indeed, today’s Toyota Prius, running on battery alone, can go roughly 10 miles. Given that 50% of all U.S. vehicles travel less than 20 miles per day[3], if you tripled the size of the Prius’ battery you’d be at a good-enough point for half the US drivers. Today’s batteries really are adequate to the task.

In addition, the next generation of batteries is considerably better — to quote:

Advanced lithium-ion batteries now becoming available for automotive use are smaller and lighter than the metal-hydride cells we have so far employed, which will allow for lighter vehicles with the same electric range or ones that can go even farther before they begin to use gasoline. At the moment, the main roadblocks to lithium-ion cells are higher cost, reduced longevity and concerns about safety, but some battery makers claim to have solved these issues with their newest designs. … I fully expect that lithium-ion cells of one variety or another will eventually replace metal-hydride batteries in hybrid cars, offering a two- to threefold increase in energy storage for a pack of a given weight, along with a greater ability to absorb energy quickly during regenerative braking and, perhaps, with adequate durability to last for 15 years and 150,000 miles.[2]

As battery technology improves, and if plug-in hybrids are successful, the high-volume production of batteries could lower their price. This would make it affordable to increase battery-pack size in successive generations and rely even less on gasoline. Eventually, the internal combustion engine could be made smaller and be used exclusively to recharge the batteries on long trips in a configuration called a “series” hybrid.[1]

The costs will be too high

Purchase price of a plug-in hybrid will indeed be higher. Face it — the batteries will add to the cost. How much more?

The Electric Power Research Institute (EPRI) estimates that, with mass production, the cost of a PHEV battery will add $2,000 to $3,000 to the cost of a conventional hybrid. EPRI studies project that after considering the lower costs of fuel and maintenance, a mass-produced PHEV should provide better overall economics than either a conventional hybrid or a conventional vehicle. Battery costs are the primary reason for this incremental cost, and battery prices are likely to fall with increased production.[3]

I’ve also seen the number “add 10% to 20% to the cost of the vehicle”.

Is this too much to pay? I picked (at random) the Ford Explorer Hybrid to look at the cost of other options. the base price of this car is $25,740, so I’d presume the extra batteries will cost something on the order of $3,000. What do some other options cost? We see:

Option Cost
4WD $1,750
Navigation System & CD Changer $2,695
Leather Seats $695
Chrome Trim $195
Side step bars $345
Moonroof & satellite radio $995

So yes, the additional batteries would cost a bunch – but no more than adding say 4WD plus Leather Seats. And if your equivalent gas use goes from say 25MPG to 100MPG, at $3/gallon (less than I’m paying now) and you drive 15,000 miles/year, you’ll save over $1,000 year in fuel cost (even counting the electricity), which , by the way, is far more saving’s than you’ll get from having the moonroof!

It shifts polution to dirty coal fired facilities

Ok, this was what I first thought when considering electric cars and plug-in hybrids. But there’s scientific data on carbon emissions for plug-in hybrids this in the ASES Climate Change report[3]:

Technology> Per Mile
Gasoline Engine 0.22 lb
PHEV/Modern Coal-Fired Power Plant 0.19 lb.
PEHV/Gas Combined-Cycle Power Plant 0.08 lb.

So even in states with a predominance of coal-generated electricity, there’s some advantage in carbon emissions.

But the opportunity to reduce carbon here is huge. Why is Austin Texas so jazzed about plug-in hybrids? The wind blows like crazy in West Texas at night. What use is all this wind power at night? Well, it could be charging the batteries in a Texas-sized fleet of plug-in hybrid vehicles.

What’s more, Penney says, “if millions of these things were produced 20 years from now, it would really enable renewable energies like wind to take off.” Wind power requires ways of storing energy generated when demand for electricity is low, he says. The cost of the storage makes it hard for wind to compete with other sources of electricity. Millions of plug-in vehicles charging at night would essentially provide free storage.[1]

Bottom Line

The bottom line is that plug-in hybrids make sense today. I get angry when people try to dismiss this as some far out future technology that “someday might be practical and cost effective”. Do your part in helping dispell this myth!

Want to do more? You can:

March 1, 2007

Mythbusters – Windmills vs. birds

Category: Mythbusters,Wind power – Dan 1:30 pm

A week ago, I caught the lead in to a conservative talk radio show. The commentator led in with an attack on windmills, and how “the environmentalists hate these things because they slaughter birds”. This business of windmills killing birds is repeated over and over as a reason why the nation, and especially the environmental community, should oppose windmills.

Since windmills are one of the most promising near-term renewable energy technologies, what’s the latest information on bird mortality? I want to approach this issue from two angles:

  • How bad is the problem?
  • Compared to what?

How bad is the problem?
The majority of controversy over bird mortality from windmills comes from early experiences at the Altamont Pass, a couple dozen miles east of San Francisco Bay. This was an early wind farm, and more than 5,000 turbines now dot the hillsides. These turbines are “believed to kill more birds of prey than any other wind farm in the world”[1].

It turns out that the Altamont Pass is a terrible place for a wind farm. After much study, reasearchers have concluded that Altamont Pass has a large bird population because of an abundance of prey:

The problem, many researchers say, begins with the abundance of small mammals in the area. “Altamont is a ground-squirrel refuge extraordinaire,” says Allen Fish, director of the Golden Gate Raptor Observatory. The plentiful mammals, combined with the mild California climate, attract large numbers of migrant and resident raptors; the area also has the highest density of wintering golden eagles observed anywhere in the world. Younger hawks and eagles, eager to hunt and build muscle and thus most enthusiastic about the fine dining available on the ground, seem especially prone to blunder into the moving turbine blades.[1]

All this said, there’s no controversy that windmills kill birds and bats. The solution to minimize the impact is careful siting studies, and avoiding areas where it will be a particular problem.

But there’s another dimension to this discussion…

As compared with what?

Yes, windmills kill birds. And as we build more windmills, the mortality rate will rise. But if we’re concerned about windmill caused bird mortality, we have to consider other man-made hazards to birds that we take for granted[2]:

  • Power lines are estimated to kill 130 to 174 million birds per year.
  • Collisions with cars and trucks are estimated to kill between 60 and 80 million birds per year.
  • Plate glass windows, especially in tall buildings and rural homes, are estimated to kill over 100 million birds per year.
  • Lighted communication towers are estimated to kill 40 to 50 million birds per year.
  • Pesticides are “conservatively estimated” to kill at least 67 million birds per year.
  • Cats kill millions of birds. A Wisconsin DNR study states that the “most reasonable” estimate is that cats kill about 39 million birds per year in Wisconsin alone.

These statistics are depressing, but my point is that windmills shouldn’t be singled out as a new and unique threat to birds. Indeed the article points out that the likely biggest man-made hazard are communication towers, and mentions one documented case where “a record 30,000 birds were estimated killed on one night” at a tower in Eau Claire, WI.

The bottom line. Yes, windmills kill birds. But the #1 threat to birds, and bats, and a host of other species, according to Birdlife International, is habitat destruction:

Habitat destruction and degradation threaten over 86% of GTBs and are currently the most serious pressures on the world’s birds. Over-exploitation and the effects of alien invasive species are also major threats and others – notably pollution and climate change – are of increasing concern. Some of these threats can be reversed, given enough resources, but others are difficult to combat and can become the final cause of extinction for species that are already reduced to tiny numbers.[3]

I’m not saying that the fact that windmills kill some birds is a good thing; we need to take measures to reduce the impact. But if committing to wind power reduces the impacts of global warming, strip mining, and air pollution, it’s the superior alternative by far.

For a more in-depth analysis of this overall topic, see the article on the Wind Energy Technical Info website titled Putting Wind Power’s Effect on Birds in perspective.