Please Note: Blog posts are not selected, edited or screened by Seeking Alpha editors.

Life Cycle Assessment Of A Tesla Compared To A Luxury Sedan

Abbreviated Life-Cycle Assessment Comparing a Typical Luxury Sedan to an Electric SedanLife cycle assessments have been used to evaluate and compare different products and processes to determine which product has the least environmental impact. These lifecycle assessments can be a full life cycle assessment which concerns every piece of material in a given product, or for comparison purposes, only the differences between the products can be considered. Cars have been analyzed and compared from both an environmental and economic perspective [5]. Life cycle assessments have also been conducted for individual cars [4]. This paper uses a life cycle assessment to compare a Tesla Model S car to a comparable four door luxury sedan. This paper considers the normal usage of a car and the expected lifetime of the car of 145,000 miles along with the dealer recommended maintenance. This amount of mileage and using the federal US standard of 15,000 miles per year, the car will last 9.67 years. It is assumed after the life of the car all the recyclable metals and plastics are sent for recycling. The mileage could be between 93,000 to 240,000 miles as per literature and as such in accordance with life cycle standards, the extreme points are not to be used an acceptable center point should be chosen.

Scope

This paper quantifies the amount of energy needed to manufacture and use a Tesla Model S and a similar luxury sedan. The efficiency of refineries and electrical generation plants were not considered for this paper since the source of both electricity and crude oil vary widely. This paper only considers the manufacturers suggested schedule for maintenance. Any maintenance above and beyond the minimum manufacturers maintenance and one-off maintenance are not considered. Only legal and correct disposal of wear parts and change parts such as batteries, brake pads, windshield wipers, oil, oil filters, and fuel filters were considered. Infrastructure upgrades to the electrical grids along with construction of new refinery capacities were out of the scope of this paper. Theft, vandalism, and accidental destruction of the cars were also out of the scope of this paper.

Similarities between the cars

Both the Tesla and the luxury sedan have many interior and exterior similarities. The interiors of both cars are going to be made of the same materials. Many of the exterior components are also going to be similar. The wheels, rotors, axle, suspension, base paint coating, hood, and tires will not vary significantly between these two types of cars. The coolant, HVAC, wiring and computer systems in the car do not vary significantly in terms of materials. The transmissions for the cars were also considered to be similar enough since the Tesla uses a simplified gearbox while the sedan uses a typical automotive transmission.

Differences

The luxury sedan has quite a number of manufacturing differences. The first difference is that most of the car panels are steel. For the specific luxury sedan studied, only the hood was aluminum. The car also has an engine block and associated parts. For the car for this analysis, the engine block was made of aluminum. The car also has an exhaust system which is comprised of steel and very minute amounts of precious metals in the catalytic converter. The luxury sedan also has a lead battery which has a projected prorated battery life of 8.33 years [3], and would have to be replaced prior to car retirement .

The Tesla Model S has different components when compared to the luxury sedan. During manufacturing there are differences from a traditional car. The differences in paint testing, leak testing, and other testing was found to be negligible and were not included.

The lithium ion battery cell is the significant difference between the cars. This battery mainly consists of lithium nickel cobalt aluminum oxide, carbon, plastics, and steel. A rechargeable lithium battery was taken apart and the components weighed in order to obtain scale up weights. The car is also made of aluminum. The other component to the Tesla is the electric motor which is made of copper and steel.

Maintenance

There are similarities between the two cars in this study such as transmission flushes, tires, brakes, and coolant flushes. The luxury sedan has more projected maintenance associated with it. With regards to the sedan, 145 quarts of oil must be added along with 29 oil filters, five engine air filters, five fuel filters, 16 spark plugs, and a PCV valve. Besides the oil these parts are not going to be recycled or refurbished. The other consideration is vehicle inspection. On average this corresponds to 3 inspections over the life of the car. Between the oil changes and the inspection, this is 315 miles or 17 gallons avoided in the case of the Tesla.

With regards to the Tesla, the projected half life of the battery far exceeds the life of the car. It is currently unknown what will be done with the batteries after the useful life of the car is unknown. Recycling, disposal, and use for other purposes was not considered. This will be covered as a recycling rate, but, it can vary significantly and this number may change based on post car usage of the battery, if applicable and is an unknown which could drastically reduce the energy attributed to the car.

This maintenance number can vary dependent on the familiarity of the individual with changing various car components and local regulations. If E85 is used for the luxury sedan, the recommended oil change is every 3,000 miles instead of every 5000 miles, which would significantly raise the amount of oil changes and the amount of gasoline used [3]. The amount of extra maintenance, type of maintenance, and improper disposal of materials were not considered and was out of the scope of this paper.

Daily usage

The EPA mpg estimate for the luxury sedan was 18 mpg. Experimentally, the luxury sedan has a mpg of 17.8 mpg, which corresponds to 8100 gallons of gasoline. A gallon of gasoline contains 1.3 x 10^8 joules. Experimentally, measuring the draw from the wall, for the 85 kwhr Tesla, it takes 32 kwhr per 100 miles, this is 0.115 GJ per 100 miles, this coincided with the EPA rating. In order to compare the two figures, both were converted to energy. In terms of energy, the luxury sedan consumes 1069 gigajoules (factoring in the full life cycle) over its lifetime and the Tesla Model S consumes 166 gigajoules.

Fueling

There are other fueling factors when comparing both these cars. For the Tesla Model S, a person trained as an electrician is needed in order to install a 220 V outlet in a house. For this case, it was assumed that an electrician was sourced locally (15 miles away) and the average mpg for the truck was assumed to be 15 mpg. From these numbers, the Tesla Model S requires 2 gallons of gasoline. This is avoided in the case of the luxury sedan. This number was subtracted from the gasoline used for the luxury sedan. This was negligible.

With regards to the luxury sedan, on average, the gas tank is filled when the tank is ¾ empty. This corresponds to 571 fueling trips. Using a best case scenario, where no gasoline pumps are empty, this requires an attendant at an 8-pump station to work 5.93 hrs over the cars lifetime. This corresponds to 0.25 gallons of gasoline which is avoided in the case of the Tesla Model S. Found to be negligible.

Analysis

The table below shows a summary of the differences in materials and energy that are needed to produce each car. For the luxury sedan, the parts of the car were listed and all the weights of the various parts were obtained from auto supply dealers, from taking apart various components, or from subtraction for the frame once all the other parts were obtained. The amount of materials were subtracted from each other to simplify the LCA. As an example, in the case of aluminum, the Tesla is made of aluminum, but the engine block and the hood of the luxury car are made of aluminum. The following information was also used in the analysis to correct for recycled components. This table also provides the amount of recycled materials used in the cars. Converted Back calculate to convert to energy.

For the case of aluminum, previous works showed the aluminum energy input as 96 GJ based on 1848 lbs of aluminum.

http://www.aluminum.org/Content/ContentFolders/LCA/LCA_REPORT.pdf

In the case of steel, the amount of energy was 27.5 GJ

http://calculatelca.com/wp-content/themes/athena/images/LCA%20Reports/Steel_Production.pdf

Copper was found to be 1.25 MJ

http://intec.com.au/wp-content/uploads/2013/01/csiro-life-cycle-assessment1.pdf

Table 1: Differences in the Amount of Materials Used in the Cars

*Note: Positive numbers mean the Tesla has more of an input, the negative numbers mean the luxury sedan has more input.

In order to make a valid comparison, all the materials were back calculated based on the amount of energy needed in order to make each material or in the case of the petrochemicals, the amount of energy inside the material that could be used for combustion. In the case of the aluminum, plastics and the steel, this was back-calculated based on the avoided energy needed due to recycling. The copper was negligible due to the price, and ease of recycling.

In the case of the batteries, an average of other rechargeable car batteries were used to determine the energy required to manufacture [7] and [MIT paper]. It was found that the batteries in the require 65 GJ for the Model S 85 Kwhr battery. This is slightly lower than the Argonne study of 300 times the initial battery, but is 212 times, which is still in the same "ballpark". The Argonne study focused on all types of rechargeable lithium batteries and life cycle assessments are very sensitive to the mass of materials involved, so using a high energy dense material should give a lower ratio vs a less energy dense material. Since the lithium batteries do not have a disposable track record, but based on the current value of a replacement battery along with the size, and value of the metals inside, it can be assumed that these batteries will be recycled in some form.

The amount of energy required was calculated based on amount of each material used and the percentage of material recycled. Based on this analysis, the amount of energy required for the Tesla Model S is 215-280 GJ over the lifetime of the car. This range is due to the unknown recycling rate of the battery and how much energy would be required to recycle the battery. The luxury sedan has a total lifetime energy input of 1100 GJ. The luxury sedan requires approximately 4-5 times the energy for the Tesla Model S. Diagram 1 shows the differences in the manufacture, use and maintenance of both cars in terms of GJ of energy.

Diagram 1: Differences in the Two Cars

Conclusions

From the analysis, the usage phase was shown to be the most significant contributor to both cars in terms of energy requirements. If the energy requirement of the cars were removed, the next significant contributor to the life cycle analysis was the aluminum, not the batteries used to manufacture the Model S. The two cars in terms of manufacturing energy are close in terms of environmental impact. The area of interest is the "break even point". This was accomplished using goal seek. The break even point was approximately 15600 miles vs the base car.

Sensitivity analysis

The sensitivity analysis includes the production and efficiency of both power plants and refineries/drilling to determine the break-even point for both the Tesla and gasoline production

The production of gasoline varies between 16% to 30% so the ends were chosen as well as the centerpoint of 20.5%. Electricity generation also varies. 60% was chose as the highest, 40% was chosen as the center and 19% was chosen as the lowest. Transmission losses were also included for grid generation.

The table below shows the "break even" points in terms of mileage.

Electrical generation/ Gasoline production

85% efficiency for oil exploration, refinement and delivery

79.5% efficiency for oil exploration, refinement and delivery

70% efficiency for oil exploration, refinement and delivery

60.00% electrical generation efficiency

18400 miles

13500 miles

11500 miles

40.00% electrical gen efficiency

23600 miles

16100 miles

13200 miles

19.00% electrical generation efficiency

114,600 miles

35800 miles

24200 miles

The break even point for all of these falls within the typical life of a car. The high efficiency gasoline generation and the low efficiency electricity generation requires an low efficiency coal plant and a high efficiency, easy to extract, refine and transport crude oil. Current trends favor the opposite of that scenario. Current electrical generation technologies favor natural gas, and high efficiency power generation. Also new crude oil drilling, such as those of Canadian shale is on the lower efficiency end.

References

[1] European association of Metals, Eurometaux Position Paper on recycling, September 1999

[2] Development Associates Inc, MSDS Product SVP-2003, June 8, 2003

[3] 2006 Model Year Scheduled Maintenance Guide, 2004 Ford Motor Company, 2nd edition, March 2005

[4] Sullivan J.L. et al, "Lifecyle Inventory of a Generic U.S. Family Sedan Overview of Results USCAR AMP Project" Proceedings of 1998 Total Life Cycle Conference, Society of Automotive Engineers, Warrendale, PA, USA, 1988, 1-14

[5] Lave, Lester B. et al, An environmental-economic evaluation of hybrid electric vehicles: Toyota's Prius vs its conventional internal combustion engine Corolla, Transportation Research Part D: Transport and Environment, Volume 7, Issue 2 March 2002, Pages 115-162

[6] Steel a Foundation for a Sustainable Future, Sustainability Report of the World Steel Industry, 2005

[7]Gaines, Linda et al, Impacts of EV Battery Production and Recycling Technical Women's Symposium, April 29, 1996, Argonne Illinios

Disclosure: I am long TSLA.