Driving Hybrids - A Scientific Justification

In the previous post, I introduced to you some background on the energy consumption by automobiles in US. In this article, I would like to focus on the one of the most discussed aspect on automobiles: the environmental impact. The environmental impact by automobiles can be categorized in several ways. Generally, the impact include air pollution, water pollution, noise pollution, land pollution, solid waste, and effects on wildlife.

Automobiles Impact on Environment

Among these the one that is most severe is the air pollution that most people live in the city know exactly how that affects their daily life. Technology has advanced in decades that the exhaust from the automobile engine contains much lower percentage of pollution-causing ingredients than it was when automobile was just invented at the beginning of the 20th century. However, according the findings from US Environmental Protection Agency [13], the identified chemical contents in the air that are major reasons for the air pollution are still contributed significantly by automobiles. This is illustrated by the following Table 1:

 According to [15], certain proof is already accepted that there are confirmed problems caused by air pollution, including respiratory problems as well as problems regarding what we eat. Respiratory problems are a very natural and scientifically established result of air pollution. While mild pollution is not awful for a healthy person in the prime of his or her life, polluting particles in the air can cause problems in children and in the elderly or the infirm. Additionally pollutants in the air can aggravate asthma symptoms and increase allergy symptoms. Another air pollution problem has to do with mercury. Mercury is a by product of many factories, and is present in the particles spewed from the tops of smokestacks. As the mercury gets into the earths atmospheric system, it mingles with rain, which then falls into water and is absorbed by fish. This is why doctors recommend not to eat fish too frequently and avoid eating large fish that may accumulate a higher concentrations of mercury, particularly for pregnant women and children

Other major noticeable environmental impacts include water pollution, noise pollution, land use, solid waste, as well as effects on wildlife [15]. The water pollution is caused by runoff of oil, brake dust, exhaust deposit, automobile fluids disposals [13]. The noise pollution is familiar to anyone who is surrounding by all kinds of vehicles where car and truck noise has become perhaps the primary source of noise pollution in urban environments. According to the Federal Highway Administration [14],  a typical pickup truck going by at 50 mph is four times as loud as an air conditioner an eight times as loud as a refrigerator. The Organization for Economic Cooperation and Development (OECD) estimated in 1980 that 37 percent of the US population was exposed to "annoying" levels of highway noise (greater than 55 decibels), while 7% was exposed to levels that made conversation difficult (> 65 dB) [17].

Environmental Benefits of Hybrids

While it is true that hybrid cars will not resolve all the negative environmental impacts listed in previous  section, the benefit is still too big to be ignored. As a fact of fact, the gain from hybrid makes it a perfect candidate for policy makes to consider to achieve true sustainability in the long run. Particularly on the air pollution [19] and gas consumption reduction [13, 14, 16], there are vast existing literature illustrating the benefits from hybrids, from both governmental agencies and academic research facilities, as well as industry research agencies.

In [1], the authors have used the mix of generating plants expected to be used for Plug-in Hybrid Electric Vehicle (PHEV) charging and find that while driving on battery power, PHEVs compared to their conventional hybrid  counterparts reduce CO2 emissions by 25% in the short term and as much as 50% in the long term. As shownin Table 1, 33% the air pollutant contributed by on-road vehicles is CO2. The 25% short reduction and 50% long term reduction implies a 8.25% drop of CO2 in the pollutant in short term, and a 16.5% drop in long term.  On the other hand, the green house gas (GHG) emissions are measured in [2] to evaluate the benefits from PHEV in GHG. As indicated by [2], plug-in hybrid electric vehicles could reduce greenhouse gas (GHG) emissions by 32% compared to conventional vehicles [20].

The national power grid could support 94 million vehicles (43% of the cars on the road) charging only during the evening, or 158 million vehicles (73%) if the charging is spread over a 24-hour period in an optimal fashion [10, 11].

On the other hand, a PHEV with 100km miles of range in electric vehicle mode is driven according to the US National Household Travel Survey (NPTS) [18] range schedule and charged nightly, the PHEV will result in an 84.1% reduction in gasoline consumption, relative to a conventional car [3, 4]. When charged nightly using real-world driving data, mid-sized sedan PHEVs with 40 miles of EV range result in a 71% reduction in gasoline consumption [5]. Conventional mid-sized sedan HEVs show a 40–45% reduction in gasoline consumption [6]. Compact cars and mid-sized SUVs show a 40-45% reduction in gasoline consumption [7]. In practice, demonstration vehicles show a very similar reduction in gasoline consumption. A 2000 Chevrolet suburban, converted to PHEV, was tested at General Motors in 2001. When charged nightly and driven with an average driving schedule, the PHEV suburban reduces gasoline consumption as compared to the baseline Suburban by 84% when driven an average driving schedule on the EPA city cycle (LA4) and 80% on the EPA highway cycle (HWFET) [8, 13]. A 2006 Toyota Prius converted to PHEV has achieved a 51% reduction in gasoline consumption, relative to the HEV Prius, during real-world testing [9].

Conclusion

It is clear that hybrid cars bring huge environmental benefits. The reduction on environment pollution and gas consumption makes it most attractive as the most viable solution for sustainability. The further the technology advances, the further reduction we can get, where technology advancement creates more job opportunities as well as makes hybrids more affordable. This huge, and potentially ever growing opportunity in hybrid cars is exactly why every country in the world wants to establish its leading role in both research and development in hybrid cars, as well as every automobile company investing huge amount of money to secure their leadership in the industry. This is the future of automobile and we are not going anywhere without this.As pointed by [12], incentives to both car manufacturers and consumers must exist to produce a new culture of automobility through extensions of already existing legislation, taxation and penalties to reduce energy consumption and polluting emissions through design of smaller vehicles, use of fewer private vehicles, and curtailment of traffic proliferation and road building. It is then ultimately important for policy makes to have a clear understanding of the global picture of this issue, and make sure we are part of this trend.

References

[1] Stephan, Craig H   (2008). "Environmental and Energy Implications of Plug-In Hybrid-Electric Vehicles".  Environmental science & technology  (0013-936X), 42  (4), p.  1185.

[2] Samaras, Constantine   (2008). "Life Cycle Assessment of Greenhouse Gas Emissions from Plug-in Hybrid Vehicles: Implications for Policy".  Environmental science & technology  (0013-936X), 42  (9), p.  3170.

[3] Bradley, T H   (2009). "Design, demonstrations and sustainability impact assessments for plug-in hybrid electric vehicles".  Renewable & sustainable energy reviews  (1364-0321), 13  (1), p.  115.

[4] Electric Power Research Institute. Comparing the benefits andimpacts of hybrid electric vehicle options, Palo Alto, CA, 1000349; 2001.

[5] Markel T. Plug-in hybrid electric vehicles. In: clean cities congress and exposition, Phoenix, Arizona, 7–10 May, 2006.

[6] Simpson A. Cost-benefit analysis of plug-in hybrid electric vehicle technology. In: 22nd international battery, hybrid and fuel cell electric vehicle symposium and exposition (EVS-22), Yokohama, Japan, October 23–28, 2006.

[7] Electric Power Research Institute. Comparing the benefits and impacts of hybrid electric vehicle options for compact sedan and sport utility vehicles. Palo Alto, California, 1006892; 2002.

[8] Schurhoff RW. The development and evaluation of an optimal powertrain control strategy for a hybrid electric vehicle. Davis: Department of Mechanical and Aeronautical Engineering, University

of California; 2002.

[9] MacCurdy D. PHEV Prius test program by Sacramento Municipal Utility District. In: ZEV technology symposium, 25–27 Sacramento, CA, September, 2006.

[10] Pacific Northwest National Laboratory, US Department of Energy, http://www.pnl.gov

[11] Kintner-Meyer, M.; Schneider, K.; Pratt, R. Impact Assessment of Plug-In Hybrid Vehicles on Electric Utilities and Regional U.S. Power Grids, Part 1: Technical Analysis, 2007, Electric Utility Environmental Conference, Tucson, AZ, Jan. 21–24, 2007.

[12] Sheller, Mimi   (12/01/2000). "The City and the Car".  International journal of urban and regional research  (0309-1317), 24  (4), p.  737.

[13] United States Environmental Protection Agency, http://www.epa.gov

[14] Federal Highway Administration, United States Department of Transportation, http://www.fhwa.dot.go

[15] Health Problems Caused By Air Pollution, ArticleBase, http://www.articlesbase.com

[16] The United States Department of Energy, http://www.energy.gov

[17] Organization for Economic Cooperation and Development, http://www.oecd.org

[18] National Household Travel Survey, Federal Highway Administration, United States Department of Transportation, http://nhts.ornl.gov/introduction.shtml

[19] Environmental Assessment of Plug-In Hybrid Electric Vehicles, Volume 1: Nationwide Greenhouse Gas Emissions, Electric Power Research Institute Report 1015325. http://www.epri.org

[20] Carbon dioxide emissions from the generation of electric power in the United States; U.S. Dept. of Energy: Washington, DC, 2000.

By Can Mao