The Clean Vehicle Research Initiative, launched in 2005, is a public-private effort that aims to produce more fuel-efficient automobiles and eventually introduce hydrogen as a transportation fuel.

The promise, potential and overriding objective of the Clean Vehicle Research Initiative is to produce propulsion systems for vehicles (personal, utility, mass transit, and military) that will:

• Use less fossil fuels;
• Produce lower quantities of greenhouse gas and carbon emissions;
• Lower the overall cost of driving.

From a consumer viewpoint the primary interest is in lower-cost driving options. The motivation to consider options other than the standard internal combustion engine grew significantly as the price of oil spiked to more than US$150 per barrel, and gas prices in the USA exceeded US$4/gallon during the summer and early autumn of 2008. Though gas prices have fallen back into the low US$2 range, the current economic climate is pressuring consumers to continue the search for lower cost solutions.

In addition to the cost issue, a growing number of consumers in developed nations across the world seek to lower their individual carbon footprints and are willing to support clean vehicle technologies with their individual buying habits.

The other major push for cleaner vehicles comes from Government initiatives across the globe. With stricter standards for lower carbon emissions, higher standards for engine efficiencies (in terms of miles per gallon), and tax credit incentives for both owners and manufactures of clean vehicles, Governments are encouraging the development of cleaner technologies.

Governments are also funding research and development of clean technologies through military development contracts, and more directly with outright grants, loans, partnerships and project funding.

For example, the proposed Obama stimulus package for the US economy includes upwards of US$7.5 billion in clean tech spending with significant amounts dedicated to battery research and development.

Alternatives to petrol – near term

Together these factors are working to bring more and varied alternative/clean technology vehicles to the market place. One well-known example is Toyota, which has been selling the Prius since 1997, and other manufactures now have similar hybrid vehicles as part of their individual product lines.

A number of smaller, independent companies such as ZAP, Miles Motors, Aptera, Tesla and Phoenix Motors have, or are expected to have, available for sale in the USA an all-electric highway speed vehicle this year.

At the recent Detroit Auto Show, most of the ‘buzz’ surrounded the various offerings of new electric vehicles. Of particular interest was the production model of the Karma from Fisker Automotive. This luxury plug-in hybrid is slated for delivery in autumn 2009. The car is expected to travel 50 miles on the battery alone, with a top speed of 125 miles per hour and acceleration performance that allows for 0 to 60 in less than 6 seconds.

Another hybrid that attracted considerable attention in Detroit is the widely-anticipated Chevy Volt. The Volt was recently honored with Green Car Journal's 2009 Green Car Vision Award at the Washington Auto Show.

Future moves

Looking to the future, the above-stated goals of less carbon-fuel use (economics) and lower emissions (environmental impact) while allowing consumers to maintain current driving habits can be met in two primary ways. Firstly, improvements on the current/traditional internal combustion engines.

This has been the primary focus of the major car manufacturers for the past couple of decades and has been accomplished mostly by technological improvements to the engine itself. The average car sold in the USA is now capable of travelling about 23 miles to the gallon, and this metric has been slowly climbing throughout the 1980s and into the current century.

According to the Bureau of Transportation Statistics, the average passenger car on the road in 1980 averaged 16 miles to the gallon.

The other method of ‘greening’ the current internal combustion engine is to change the fuel to cheaper, more renewable options. Alternative fuels being used include biodiesel, ethanol derivatives, natural gas and hydrogen. Of these, the cleanest fuel option – and the one that is garnering the most attention – is hydrogen. Burning hydrogen produces heat and water, with absolutely no carbon emissions. The problem is how to source/store the hydrogen on board a vehicle.

Alternative technologies for vehicle power sources

The alternative power technologies have all been centred on the use of electric power, either replacing or complementing the internal combustion engine. Car manufacturers today are selling/developing three versions of an electric powered vehicle. These include all-electrics (such as the Aptera), hybrids (the Prius) and plug-in hybrids (the Karma, or the Chevy Volt).

The concept of an all-electric vehicle is appealing in theory (due to the cost of operation), but the current drawback for the consumer is the reality that these cars currently offer (at the very top end) distances of just above 100 miles per charge. Alternatively, hybrids and plug-in hybrids have smaller batteries and will not travel as far on the battery alone, but offer an onboard engine that will power the vehicle and/or recharge the battery, allowing for much longer travelling distances.

Clean tech enthusiasts hope that electric vehicles will ultimately be charged at night or during other periods of off-peak grid use, with power derived from renewable power sources such as wind, solar and wave generation facilities. This scenario is truly the ‘Holy Grail’ for clean vehicles. Under such an ideal scenario the operating cost (for the power) would likely be about US$0.05 to US$0.06 per mile to the consumer, because this power would primarily come from power plants that are kept operating even though the electricity is not being used for more traditional needs. For the utility the cost to generate the power to charge electric vehicles off-peak would essentially be zero.

All in the battery

If these alternative vehicles are to be successful, the key will be the price/performance of the battery that provides the power, and hence replaces the conventional engine. In powering a vehicle, designers/engineers are concerned with a number of performance metrics. Chief among these metrics is energy density (watt hours per kilogram – Wh/kg). Figure 1 – provided by Nexergy – illustrates the energy to weight and volume of current battery technologies.

Other important performance metrics include discharge rates, distance per charge, recharge rate, cycle life, shape and size configurability, easy of maintenance, safety, and cost.

Today the industry is using and researching a number of battery technologies including:

• Lead-acid – by far the lowest-cost solution as this technology has been available since the mid 1880s. The issue with lead-acid batteries is the energy density. This type of battery is very heavy and the cycle life is low. However, meaningful advances are being made through the addition of activated carbon at the anode of the cell. The activated carbon appears to enhance the power potential and significantly extend the cycle life characteristics of the lead-acid cell. A major developer of this technology is a small Pennsylvania company, Axion Power;
• Nickel-metal hydride – this type of battery is in use today in the Toyota Prius hybrid, and other hybrids. This battery chemistry has an attractive cost profile and is very safe;
• Lithium-ion – this is the battery chemistry of the near future as it has excellent energy density characteristics, a long cycle life, and can be manufactured in nearly any shape or size. The early concerns about lithium-ion battery safety have been eliminated with current advances in lithium-ion chemistry. Though lithium-ion cells are currently somewhat expensive, the cost is predicted to fall as volume manufacturing comes on line. The number of entities (including collaborations) working on some form of a lithium-ion cell throughout the world is formidable. A few of the companies that have garnered a fair amount of media attention include A123, Ener1 Inc., AltairNano, BYD Auto, Valence, JCI-Shaft and Compact Power (a subsidiary of LG Chem);
• Zinc air – this battery chemistry is interesting, as the materials are very inexpensive and the energy density is quite high. To date, only a few companies are working with this technology. Leo Motors in Korea is the only car company I know of that has this chemistry in development for a vehicle application. The difficulty in using this technology lies in recharging the cell.

What about the fuel cell?

From the standpoint of renewable energy and zero emissions, the hydrogen fuel cell is the gold standard. Though there are myriad fuel cell models, the concept is basically to use a chemical reaction to generate hydrogen that can be burned directly, or use hydrogen in a cell to form H2O molecules and electrons. It is this last reaction that produces zero carbon emissions (again, see living with energy intermittency, page 30, for more details on fuel cells).

The issue (and the engineering challenge) is how and where to generate the hydrogen and how to store the hydrogen in a vehicle. In looking at the total picture, we also need to ask where the energy comes from to produce the hydrogen.

A number of car manufacturers are working on hydrogen fuel cell vehicles. For example, General Motors, with its Fuel Cell Development Center, is spending millions of dollars each year in an attempt to become the first company to sell one million fuel cell vehicles. To this end the organisation has under development a hydrogen fuel cell model of the Chevy Volt hybrid. Daimler-Benz is collaborating with Royal Dutch Shell, Ford Motor and Ballard Power Systems to advance the technology for use in vehicles. Additionally, Toyota Motors is spending an estimated US$800 million annually to develop fuel cell and other alternative-fuel cars. Though the technology is still early, the promise is significant as hydrogen is an abundant and renewable resource.