See the Tabbed Pages for links to video tutorials, and a linked list of post titles grouped by topic.

This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.

Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".

Friday, July 8, 2011

President Obama Considers Increasing the Fuel Economy Standard for Cars

Summary:  The New York Times reports that President Obama is considering an increase in the average fuel economy standard for passenger cars and light trucks, for the period to 2025.  The standard could be raised to 56.2 miles per gallon, which represents a considerable increase from the standard of 35.5 miles per gallon to be reached by 2016.  Currently only about 13% of the total energy content in gasoline fuel reaches the drive wheels to propel the car forward.  This post summarizes various improvements, some already operational, others at various stages of development, that could be implemented in future auto products to help reach a standard such as that being considered.  Auto makers argue that putting such changes in place would not be economical and/or would not be accepted by consumers.  In balance, we conclude that both economically and from a policy perspective, increased fuel economy in the cars of the future would be beneficial.

Introduction.  Warming of the average temperature of the world, as measured over much of the earth’s surface over the time frame of years, is currently occurring, due to the release of ever-increasing amounts of greenhouse gases into the atmosphere.  This conclusion is broadly accepted among the scientific community based on collective scientific studies by almost 2,000 climate scientists around the world (the United Nations Intergovernmental Panel on Climate Change) , and understood by much of the American public at large (see the previous post on this blog).  Most emissions of greenhouse gases arise from mankind’s burning of fossil fuels for energy.  The increase in greenhouse gas emissions began with the industrial revolution in the nineteenth century.

According to Wikipedia, the U. S. was responsible for almost 20% of the world’s CO2 emissions in 2007, (using data collected by the Carbon Dioxide Information Analysis Center for the United Nations).  Yet, the U. S. has only 4.5% of the world’s population, showing that its energy consumption per capita is very high.  It had the seventh highest energy consumption per capita in the world as of 2005, after Canada and other nations with small population numbers.

The total amount of energy used in the U. S. in 2008 is given by major economic sector in the table below, in units of quadrillion (1015) Btu (British thermal units; the amount of energy needed to heat 1 pound of water by 1ºF, about 1,055 joules).

Pct (%)

Source: Summary, Real Prospects for Energy Efficiency in the United States,; citing U.S. Energy Information Agency Annual Energy Outlook 2008.

The table shows that of the total energy demand in the U. S. in 2008, 28% was devoted to transportation.  This category includes light cars and trucks, which serve individuals and families in their work and leisure lives, as well as heavy duty trucks and air travel.  As of 2003, excluding air travel, about 75% of vehicular transportation energy was consumed by cars and light trucks.

The U. S. Energy Information Agency (EIA) reports that CO2 emissions from the transportation sector in 2008 broke down as shown below:

2008 Million Metric Tons
2008 Percent
Jet Fuel
Diesel and related fuels

Higher Fuel Efficiency Standards for Cars.  The New York Times has reported that the administration of President Obama is likely to propose a large increase in average fuel efficiency for cars and light trucks to be effective by 2025.  The proposal is being contested by the auto industry. 

Currently the U. S. has a regulation in place requiring that the average gas mileage for the cars that a manufacturer produces must reach 35.5 miles per gallon (6.62 L per 100 km) by 2016. 

The new standard for the period leading up to 2025 is likely to be 56.2 miles per gallon (4.18 L per 100km).   According to the newspaper report, the fuel consumption standard in effect in Europe will reach about 60 miles per gallon by 2020, almost 7% higher and 5 years earlier than the new, more stringent standard being discussed in the U. S. American automakers are concerned that reaching this goal will make cars very expensive, so that sales will suffer, and that extensive research will be necessary to devise new technologies that will permit meeting the objective.  They further claim that, in order to meet the new criterion, cars will have to be significantly smaller, a feature they fear will turn American car buyers away.

Sources of energy losses in gasoline-powered cars.  The graphic below shows the losses that occur in operating a gasoline-powered car, using an internal combustion engine.  Of 100% of the energy potentially available in the fuel, only about 13% reaches the drive wheels to propel the car, and another 2% is used to operate accessories in the engine, and air conditioning, for example.  At the web site, clicking on any of the blue arrows explains the losses shown here. 

Attaining the new, higher goal for fuel economy being considered by the U. S. government relies on minimizing these sources of energy loss, converting the lost energy into useful energy propelling the car along its way.

In this post, we restrict consideration of fuel economy to cars with internal combustion engines.

Capturing waste heat.  Clearly, the largest energy loss occurs in the engine, where the heat of burning the fuel is deliberately disposed of in the radiator or other engine cooling mechanism.  Additional heat from burning the fuel, not shown in the diagram above, occurs in the catalytic converter, where the product of incomplete engine combustion, carbon monoxide, is burned with more oxygen to make the final combustion product, carbon dioxide.  Because of the large amounts of lost energy involved, capturing even a portion of the waste heat of combustion could make a significant contribution to improving fuel economy.

One way of using the excess heat might be by developing heat-driven turbines, for example, that could either contribute directly to the drive train, or generate electricity for electric hybrid vehicle operation.  A second way of seeking to capture the heat is developing solid state thermoelectric converters that directly produce electricity using temperature differences between two points.  Research on new materials and processes for thermoelectric conversion potentially usable in cars is discussed here   U. S. Patent 4,753,682 issued June 28, 1988 describes a thermoelectric apparatus for use in generating electric current from the excess engine heat of an internal combustion engine. This modality also could be used in electric hybrid operation.

Rolling resistance.  As they roll along the road, tires deform and then regenerate their cross section; this continuous process dissipates energy within the material of the tire which is lost as heat.  The heat of deformation reduces the efficiency of moving the vehicle.  This is shown as Rolling Resistance in the diagram above.  New synthetic rubber materials known as solution-polymerized styrene-butadiene rubber (S-SBR) have been developed which have improved rolling characteristics with less deformation loss, while retaining traction.  Several Japanese companies and a German company are setting up new plants to make S-SBR tire material in Asia as reported in the May 30, 2011 issue of Chemical and Engineering News, a publication of the American Chemical Society (unfortunately the link requires a subscriber login).

Energy Efficiency Opportunities in Gasoline-Powered Cars.  The U. S. National Academy of Engineering, a component of the National Academies, issued the report “Real Prospects for Energy Efficiency in the United States” in 2010.  A free summary may be obtained here.  Chapter 3 of the report deals with transportation.  It summarizes various technologies available or under development that would enhance the efficiency of operation of internal combustion engines.  In the near term these include variable valve timing, variable valve lift, cylinder deactivation, direct injection turbocharging with engine downsizing, reduction of friction and smart cooling systems.  In the time frame for the new fuel economy standards that are being considered, additional improvements include camless valve actuation, continuously variable valve lift, and homogeneous-charge compression ignition.  The report estimates that implementing such improvements would result in 10-15% improvement in fuel economy in the period to 2020, and an additional 15-20% by 2030.

Diesel engines, which rely on compression for ignition of the fuel, are already 20-25% more fuel-efficient than spark-ignited engines.  Additional improvements are also envisioned for these engines.

In the drive train, improvements in automatic transmission may increase efficiency by perhaps 6-9%.  Further improvements can be obtained by reducing vehicle weight.  The report states that reducing the weight by 10% can lead to a 5-7% increase in fuel economy when the weight reduction is accompanied by reducing the power of the engine accordingly.

Costs of Improving Fuel Economy.  The Energy Efficiency report estimates the additional costs that may be expected from incorporating fuel-economizing improvements such as discussed here.  In considering separately a gasoline-driven car, a diesel-driven car and a hybrid electric car, the additional cost in each category (in 2007 currency) varies between being cheaper by US$400 and being more expensive by US$2,000 in 2035.  This writer estimates that with the fuel economy of 56.2 miles per gallon that might be imposed, compared to the standard of 35.5 miles per gallon to be in effect by 2016, if one drives 15,000 miles per year, such an additional cost would be recovered in the savings from using less fuel in only a few years.

Conclusion.  The Obama administration is likely to propose increasing an average measure of fuel economy for passenger cars and light trucks, possibly to 56.2 miles per gallon, to be attained by 2025.  There are many benefits that would result from such a standard.  The U. S. imports much of the petroleum used to make the gasoline for our cars.  Much of this imported oil originates in parts of the world that are politically unstable and whose agreement with American interests may be questionable.  This makes us vulnerable to fuel disruptions, affecting costs and availability.  The disruption in supply from Libya earlier this year is an example.  It would be useful to be less reliant on foreign sources for oil, which is foreseen as a result of increasing our fuel economy standards.

The research, development and manufacture of cars incorporating new technologies such as mentioned here would be beneficial for America’s continued economic development.  The auto industry is a major component in this country’s manufacturing sector.  It is important to maintain and promote the employment of its workers.

Using less fuel for motor transport is effective to reduce the emission of greenhouse gases, thus lowering the rate of adding greenhouse gases to the atmosphere.  Even if production of all new items and equipment that emit greenhouse gases were to cease, emission of greenhouse gases from equipment already in use would continue for another 20-40 years until that equipment was taken out of service.   The atmosphere is like a bathtub containing greenhouse gases, whose faucet keeps pouring in more but whose drain is essentially plugged so that practically none can escape.  Under these circumstances, our atmospheric CO2 bathtub fills up higher and higher.  The additional greenhouse gases result in an even higher average global temperature, with all its detrimental effects.  Therefore it is to our advantage to minimize the emission of greenhouse gases as much as possible.

The Energy Efficiency report shows that the cost of producing cars with the improvements giving greater fuel economy is absent or moderate.  The concern expressed by auto manufacturers that producing these cars would price them out of the market appears to be countered by this writer’s “back of the envelope” estimate that any increased cost would be recovered in at most a few years as a result of the use of less fuel.

The considerations discussed here show that President Obama’s intended increase in the average fuel economy of gas-powered cars for 2025 is largely attainable and overall would benefit American interests.

© 2011 Henry Auer

No comments:

Post a Comment