On the Road to Renewable Transportation

Nov. 6, 2007
The OECD estimates that replacing 10% of the country's motor fuels with bio-fuels would use one-third of all croplands.
By Béla Lipták

The coming third industrial revolution will convert the global economy from exhaustible sources of energy to renewable ones. We process control professionals will play a major role in this transition. My new book on renewable energy process automation, Post-Oil Energy Technology: After the Age of Fossil Fuels, describes the new control systems we will use.

Here I will discuss just one aspect of this future: transportation. The following trends are observable:

  1. pressure on car manufacturers to improve their fuel economy;
  2. pressure on manufacturers to develop gasoline and diesel engines that use ethanol-gasoline mixtures and bio-diesel fuels;
  3. pressure on manufacturers to introduce multi-fuel vehicles;
  4. pressure on manufacturers to introduce regular and plug-in hybrid cars;
  5. development of electric cars using new high- density batteries;
  6. development of electric cars with hydrogen fuel cells; and
  7. development of hydrogen combustion engines in cars.

The car manufacturers have not decided yet if the future belongs to the all-electric car, the hydrogen fuel cell, the hydrogen-burning internal combustion engine or some multi-fuel vehicle. Each has its advantages and disadvantages. The efficiencies of the various engines presently in use are gasoline, 25%; diesel, 35%; hydrogen IC, 38%; hydrogen fuel- cell, 45% to 60%.

Bio-Fuels and Multi-Fuel Vehicles

By 2020 the EU wants to replace 10% of its transportation fuel with ethanol. In China the number is 15%. In the U.S., the Senate is proposing a bio-fuel production target of 36 billion gallons by 2022, of which 21 billion would come from corn-based ethanol. At the same time the Organisation for Economic Cooperation and Development (OECD) estimates that the replacement of 10% of America’s motor fuels with bio-fuels would require about one- third of all the cropland, which today is devoted to the production of cereals, oilseeds and sugar crops.

The three main American car manufacturers are planning to have half of their fleets run on E85, a blend of 85% ethanol and 15% gasoline or on bio-diesel fuels. Ethanol is corrosive, can not be distributed through gasoline pipelines, trucks, railcars or barges. While the government subsidized ethanol production and in 2005 mandated its use, it did nothing about its distribution. Hence, corn prices doubled (from $1.65/bushel to $3.37/bushel), the number of ethanol plants nearly doubled (from 81 to 129) while only 1,000 out of the 179,000 gasoline stations can pump it and while nearly 40,000 ethanol rail cars are on back- order.

Consequently, during the last 12 months, the price of ethanol collapsed, dropping from $3.60 to $1.80/gallon.

Hybrid Cars

The GM Chevrolet Volt hybrid-electric car is estimated to give 150 miles per gallon and be available by 2010. Honda has dropped the hybrid versions of Insight and Accord and, in addition to its hybrid Civic, is working on a completely new hybrid car. Toyota, after the success of the Prius, is planning to have a hybrid version of all its models by 2010.

Toyota’s Prius is available in a version that has been converted to hydrogen by Quantum Fuel Systems. Conversion kits are also available to convert the Prius and Ford’s Escape into a plug-in-hybrid, which it says will get up to 75 mpg, by the addition of extra batteries.

It has been suggested to use the stored electricity in the batteries of plug-in hybrid cars on the utility’s grid to reduce peak demand. The contract between the owner and the utility would contemplate that at night—when electricity is inexpensive—the owner would  charge the batteries, and during peak periods, if the car is not in use, it would be left plugged in, and the charge in the batteries would be available to the utility, always leaving enough power to start the gasoline engine, until recharged.

Electric Cars

Electric Vehicles (EVs) are no longer just glorified golf carts. Today at least ten electric car designs are in production, and more are on the way.

Energy independence and operating cost are the main advantages of replacing internal combustion (IC) engines with batteries—energy independence, because electricity is made mostly from American coal and operating cost, because the price of a gallon of gasoline can pay for the electric energy used to drive 100 miles. Another advantage of the electric car is that its fuel distribution infrastructure already exists, since only an electric plug is needed to refill the batteries.

The main disadvantage is cost, namely the purchase price of the electric car, which today is still around $100,000. Other disadvantages include limited driving range, long charging time, short battery life and small cargo space, which is limited by the weight and size of the batteries. Some high-voltage charger designs (Altair Nanotechnologies), claim to reduce the several hours normally required to 10 minutes. Other ideas include the design of “filling stations” that would replace the block of batteries with already charged ones. These electric filling stations could also offer multiple fuels.

During the last 25 years, the cost of batteries has been reduced by a factor of 12, and according to the California Air Resources Board, if lithium-ion packs were mass-produced, their unit costs would drop to $3,000 to $4,000.

In yet another experimental design variation (by Solar Electric of California), solar collectors are added to the roof of the car and use the electricity generated to recharge the batteries.

Fuel Cells vs. Batteries

Unless new batteries are discovered that can safely provide much higher energy densities, fuel cells will continue to outperform today’s heavy and large storage batteries. Today’s batteries are less expensive than fuel cells, but their energy density is insufficient, and their weight and size are both too high to provide the required driving range. The final outcome of the battery versus fuel cell race cannot be predicted yet, because there are substantial developments in both fields.

The early electric cars used the old lead-acid batteries. Today’s hybrids are provided with more robust nickel-metal units. The EVs of the future are likely to be provided with lithium-ion batteries, found in today’s laptops and cellphones. In this area much work remains to be done to increase their safety and life to 100,000 miles of driving and to reduce their cost.

New battery developments include the ultra-capacitor hybrid barium-titanate powder design patented by EEStor, Austin, Texas. (The company is very publicity shy and has no operating website, but details about its system are available at www.technologyreview.com/Biztech/18086/?a=f.) These devices can absorb and release charges much faster than electrochemical batteries. They weigh less, and some projections suggest that in electric cars they might provide 500 miles of travel at a cost of $9 in electricity.

The direction of hybrid car design is also influenced by battery developments. Today, Toyota’s Prius uses the heavy and range-limited nickel-metal hydride battery, basically because it is safe. The Prius recaptures energy during breaking and runs on electric power in stop and start traffic, but its all-electric mode of operation is limited. GM plans to increase the electric mode of operation of the Chevrolet Volt, which is designed as a “plug-in hybrid” that can be recharged overnight. GM plans to use high-energy density lithium-ion batteries to obtain an all- electric range of 40 miles and hopes that these batteries will be safe and reliable by 2010. 
Another battery development involves high temperature and larger units. NGK Insulators Ltd. in Japan uses sodium sulfur batteries operating at 427 °C (800 °F) and have a capacity to deliver one mW for 7 hours from a battery unit, which is about the size of a bus. Such units could be used on filling stations that are not connected to the grid.

Hydrogen Fuel Cell Hybrids

In the cars with high-efficiency fuel cells, the fuel is hydrogen and the motor is electric. Fuel-cell efficiency is about 60%, while the efficiency of gasoline internal combustion engines is only 25%. This high efficiency of the fuel cells makes them prime candidates for use in the electric cars of the future. (Figure 1) 

“Gas” station of the future?

A hydrogen filling station in Japan consists of two 300-cubic meter tanks and five filling stations for dispensing hydrogen in both as high-pressure gas and as liquid.
Courtesy of Linde Kryotechnic

As to the storage of hydrogen, GM’s 100 HP Hydrogen3 model wagons can store hydrogen either in the gas or liquid forms, while the Mercedes F-Cell and Honda’s FCX models use gas storage. BMW’s Hydrogen 7 model burns hydrogen in its fuel cell up to a range of 200 kilometers, and when that range is exceeded, it can be switched to burn gasoline. DaimlerChrysler has some 100 fuel cell vehicles around the world, including its Mercedes-Benz F-Cel. 

GM’s “Volt” and Ford’s “Dayglo” and “Edge” fuel-cell hybrids are likely to operate with lithium-ion batteries and fuel tanks for high-pressure hydrogen gas containing 4.5 kg to 10 kg of hydrogen and get about 60 miles per kilogram of hydrogen.
One version of the hydrogen fuel tanks, Quantum Technologies’ TriShield composite cylinders can hold up to 3 kilograms of hydrogen at 5,000 PSIG, which is sufficient for a 200-kilometer journey in a standard sedan.

Hydrogen Internal Combustion Engine

Because of its lower volumetric energy density, when liquid hydrogen is used as transportation fuel, the hydrogen fuel tanks need to be three times the size of today’s gasoline tanks to provide the same driving range. Today, a typical passenger car has a range of 575 miles and is provided with an 18-gallon tank, while an 18-wheeled semi-trailer has a 750-mile driving range and requires two 90 gallon tanks. Actually, the volume of the hydrogen tanks can be somewhat smaller, because hydrogen internal combustion (IC) and fuel cell engines are more efficient than the gasoline burning ones (gasoline: 25%, hydrogen IC: 38%, hydrogen fuel cell: 45% to 60%).

BMW, DaimlerChrysler, GM, Honda and Toyota are placing some 100 cars—both IC and fuel-cell units—into the hands of ordinary drivers to gain experience and to collect data. The prototype units cost about $1 million each. The manufacturers aim for a “pilot commercialization phase” by 2010-2012 at a unit cost of $250,000, full production by 2013 at a unit cost of $50,000. The cost will drop as the volume of production increases.

The list of vehicles that can run on hydrogen is constantly growing. Quantum Fuel Technologies Worldwide converted Toyota Priuses to hydrogen fuel. BMW is marketing its 7 Series, 12-cylinder, 260 horsepower car with an internal combustion (IC) engine that can burn liquid hydrogen or run on gasoline. The BMW-750 hl burns liquid hydrogen in an IC engine. The Ford E-450 shuttle bus burns 5,000 PSI hydrogen gas in an IC engine.

Iceland offers hydrogen-fueled rental cars via Hertz. In Japan, as part of its national hydrogen program, a 200,000 m3 tanker ship has been designed for transporting hydrogen. A hydrogen-fueled commuter train, using hydrogen at 35 mPa (5000 PSIG or 350 bars) operates in Japan, fueling a 125 kW ”Forza” PEM fuel cell by Nuvera (www.rtri.or.jp).

Hydrogen buses operate in Montreal and Bavaria; a hydrogen-powered passenger ship sails in Italy; and the 2008 Olympics in Beijing will feature hydrogen vehicles. Russia has flown a jet fueled partly by hydrogen. In the U.S., DARPA, NASA and the Air Force are jointly developing a hydrogen-fueled earth-orbit airplane. Two teams are converting light planes to hybrid fuel cell/battery electric engines.

Hydrogen Filling Stations

As of this writing, according to a survey by Fuel Cell Today, there are 160 hydrogen fuel stations world wide. In the U.S., there are 170,000 gas stations. During the transition from oil to hydrogen, 12,000 filling stations would be needed to supply 70% of the population.

High-pressure hydrogen tanks are made of carbon fiber. Cryogenic (liquid) hydrogen tanks are double-walled with the space between the walls evacuated to provide good thermal insulation.

Hydrogen filling stations are already in operation in Japan, Germany and in the U.S. in Vermont, Florida and California. Some of these  are gas-and-liquid dispensing stations, such as the one designed by Air Products at the University of California in Irvine. In Burlington, Vermont, the Department of Public Works’ hydrogen fuel station uses wind energy to produce 12 kg/day of hydrogen. Air Products and Chemicals participated in the design of this wind-to-hydrogen generator. Figure 1 illustrates a hydrogen tank farm.

In Orlando, Fla., Ford airport buses are served at a Chevron energy station, where 115 kg/day of hydrogen is generated by H2Gen Innovation units. In Munich, a fuel station designed by Linde can dispense hydrogen in both liquid and gaseous forms. At that fuel station, hydrogen is stored above ground in a 17,600 liter tank and is dispensed at a rate of 50 liters/minute. Gaseous hydrogen is produced from liquid hydrogen by evaporation followed by two steps of compression to 350 bars (5000 psig) at 15 °C.

Béla Lipták is a control consultant, editor of the Instrument Engineer’s Handbook and former adjunct professor at Yale University. He can be reached at [email protected].