Letters to the Editor
To the Editor:
David Hafemeister (Physics and Society, v.38, No.2, pp 17–18) presents figures and costs for electric cars. Conspicuously absent is the amount of electrical energy that would have to be generated for powering the electric cars in the U.S.
How much energy would be needed to power all 160 million automobiles in the United States? On average each automobile uses 500 gallons per year (assuming 10,000 miles driven and 20 miles per gallon). This is roughly 500x40 kWh. At an efficiency of 25%, this is 5,000 kWh per car (0.5 kWh/ mile) or 0.8 x 1012 kWh energy required to move them.
Total electric energy generation in the United States in 2004 was 3.97 x 1012 kWh. (U.S. Statistical Abstracts). In other words, to power personal automobiles alone the electric power generating plant would have to be increased by at least 20%. Electrical energy does not, after all, simply come from the wall in which the electric plug is installed.
As for the batteries, there is not enough lead produced to equip all the automobiles in the United States with lead-acid batteries. It would be interesting to find out whether there is sufficient lithium or other materials for so many batteries. No one seems to address such mundane questions. In addition, researchers at Carnegie-Mellon University (L.B. Leave, C.T. Hendrikson and F.C. Michael, Science 268, 993, May 1995) have shown that lead pollution from lead-acid batteries for this many automobiles (160 million) would be about the same as it was prior to the removal of tetraethyl lead from gasoline.
Electric energy requirements for electric cars are treated at some length in the Encyclopedia of Environmental Analysis and Remediation, J. Wiley & Sons, New York 1998. By now most people realize that the electric car is a dead duck.
Synergy Institute, P.O.Box 561, San Ramon, CA 94583
925 683 9254
David Hafemeister and Peter Schwartz respond:
Mr. Bevc brings up important points, which when considered further endorse the electric car as the most beneficial technology to develop for individual transportation. The bottom line is that the lithium battery, if successful, will lead us to the electric car of the future. Different sources quote somewhat different numbers, so we break our analysis into a number of issues:
kWh/mile and vehicle miles per year: The industry standard is 0.35 kWh/mile as quoted from the 2009 APS study (pg. 37); Mr. Bevc used 0.5 kWh/mile. The Federal Highway Administration gives 3.029 x 1012 miles driven per year for 2007. We will use 3 x 1012 miles/year, which agrees with APS (Fig. 10, p. 34). Not all of these vehicle miles can be converted to electricity because larger vehicles will be too costly to convert. About 80% of these vehicle miles are "residential vehicle miles" so we reduce 3 x 1012 to 2.4 x 1012 .
kWh/year needed: The U.S. produced 4.115 x 1012 kWh/ yr in 2008. Using the numbers above, the electric fleet would need (2.4 x 1012 miles/yr) (0.35 kWh/mile) = 0.84 x 1012 kWh/ year. This agrees closely with Mr. Bevc's projection of 0.8 x 1012 kWh/yr and his figure of 20% of total electricity use for electric cars. As we argue in the next paragraph, however, this by no means translates to requiring a 20% increase in generating capacity.
Power Plants needed: The adoption of the first 20% of the electric fleet will not need too many additional power plants since the base-load plants are not efficiently using night-time power when many facilities are idle. The Electric Power Research Institute (EPRI) examined this effect for California, which varied, typically, from a peak of 39 GW to a minimum of 23 GW. EPRI determined that the underutilized night-time power of 16 GW could fuel 5 million cars. Additional power plants would have to produce (0.8)(0.84 x 1012 ) = 0.67 x 1012 kWh. If the plants operated with a 100% duty factor this corresponds to 76 GWe. This could be fulfilled with 100 one-GWe traditional power plant with a duty factor of 0.8. These cars would use lithium batteries and not lead batteries, as suggested by Mr. Bevc. The world's estimated 10 million tons of lithium is sufficient to supply lithium ion batteries for more than 1 billion cars. As half of this lithium is in Bolivia, we are hopeful for President Obama's positive direction with Latin American diplomacy. Overall, it is highly likely that lithium batteries will be robust, safe, and economic when all factors are examined.
Finally, Mr. Bevc misses a crucial point in his dismissal of electric travel: We certainly do not at present need either enough electrical energy nor enough battery capacity for an entire fleet of electric cars because a transition to electric travel will not be fast, and it will not be complete. The average car remains in service for about 15 years. It is unreasonable to think that tomorrow 100% of the population will choose to buy electric cars over gasoline automobiles. Even a very ambitious market growth for the electric car will require at least 30 years for the majority of personal travel to be done with electric cars. What happens as far as charging infrastructure, energy storage, and public transportation is anyone's guess. For now, electric transportation is likely our best option.
David Hafemeister & Peter Schwartz
Physics Department, Cal Poly University
To the Editor:
In the January 2009 edition of Physics & Society, Robert Levine wrote a thoughtful letter objecting to the statement on climate change adopted by the APS Council on November 18, 2007. As an APS member I also strongly object to this statement. It is written below:
Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate. Greenhouse gases include carbon dioxide as well as methane, nitrous oxide and other gases. They are emitted from fossil fuel combustion and a range of industrial and agricultural processes.
The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth's physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.
Because the complexity of the climate makes accurate prediction difficult, the APS urges an enhanced effort to understand the effects of human activity on the Earth's climate, and to provide the technological options for meeting the climate challenge in the near and longer terms. The APS also urges governments, universities, national laboratories and its membership to support policies and actions that will reduce the emission of greenhouse gases.
It is mostly the second paragraph that I object to. Certainly for the past ten years, the assertion is demonstrably false; the earth's average temperature has remained about constant after a 30-year period during which the average temperature increased by about three quarters of a degree Fahrenheit. Secondly, the disruptions APS considers 'likely' are based almost entirely on models, simulations, and speculations, but are nearly devoid of any experimental justification. Can the APS really point to any existing trend, occurring today, which extrapolates to the sort of doom and gloom the second paragraph implies? The population of polar bears is increasing. Glaciers have been receding for at least the past 200 years. Ice in Greenland and the Antarctic is melting in some places and thickening in others. Humans are getting healthier, lifespan is increasing, and social systems persist (at least in the democracies). In fact, over the millennia of human civilization, warm periods have been beneficial, cold periods, harmful. Shouldn't we physicists consider today's empirical evidence as well as projections?
The paragraph then goes on to say "we must reduce the emission of greenhouse gases beginning now." Does the APS seriously believe that we can just give up carbon the way a smoker can just give up cigarettes? Civilization takes energy and lots of it. Right now, we get 85% of our energy from carbon-based sources. What does the APS propose to replace it with: solar panels, windmills, nuclear reactors? Can it make the case that this is scientifically and technically possible? Unquestionably, to eliminate carbon fuels and not replace them with equivalent energy is to end civilization as we know it. The APS statement completely ignores this vital truth.
As a middle ground between the APS statement and other statements which deny manmade contributions to global warming and climate change, I propose this statement:
The issue of increased CO2 in the atmosphere and its effect on climate is an issue of increasing concern. A great deal of this CO2 comes from energy production. As physicists we realize that 85% of the world's energy comes from carbon-based fuel. We recognize that there is no economical substitute for this fuel on the scale required, and most likely will not be one for decades. While the APS certainly advocates conservation and improved efficiency, we recognize that as the world develops, it will need more energy, not less. We recognize the inextricable link between affordable energy and human well-being, good health, education and a clean environment. Finally we recognize that eliminating carbon-based fuel before a replacement fuel is ready on the required scale, at about the same price, constitutes at least as grave a threat to human civilization as global warming.
As physicists we understand the greenhouse effect. However, we also know that the earth's climate is extremely complicated and there is much more to it than the greenhouse effect. Other scientists understand this better than we do. The American Meteorological Society has come out with two statements of concern, in 2003 and 2007. Each statement emphasizes risks of increasing CO2 accumulation in the atmosphere, but each also mentions that there are great uncertainties. Each points out that much more is needed in theory, simulation and measurement. The 2007 statement even mentions that there could be benefits to global warming, and points out that while ice is melting in some parts of Greenland and Antarctica, it is thickening in other parts.
In 2005 the presidents of the Academies of Science of 11 countries jointly signed a letter expressing concern over CO2 accumulation in the atmosphere and global warming . However, they emphasized adaptation as well as prevention. Also, unlike the more dire predictions, they foresee a sea level rise of 10-90 cm during the 21st century.
As regards the science of global warming, APS supports the 2003 and 2007 statements of the American Meteorological Society and the statement of the 11 academy presidents.
I hope that Robert Levine's letter, and this letter stimulate much-needed discussion in the APS as to what our appropriate role in this issue should be. Most of all, I hope the APS puts out a new statement more scientifically defensible and more balanced in its conclusions and recommendations.Wallace Manheimer
retired from U.S. Naval Research laboratory
These contributions have not been peer-refereed. They represent solely the view(s) of the author(s) and not necessarily the views of APS.