Economic and emissions impacts of electric vehicles

By Ulrich Decher, Ph.D.

President Obama during his 2011 State of the Union address stated that we should have one million electric vehicles (EV) in the United States by 2015. The benefits of that would be to to reduce our dependence on foreign oil and to reduce emissions. These are worthy goals. This article will take look at the economic impact of using electric cars, their emissions, and their impact on the electric grid.

Nissan Leaf

As an example of a currently available electric car, I have chosen the Nissan Leaf since it is all electric.

The car has the following pertinent specifications:

• Price $32 780
• 100 miles per electric charge
• 24 kWh lithium-ion battery

Operating economics

The Leaf might be used primarily as a second car for commuting on a daily round trip of say, 50 miles, requiring a daily charge of 12 kWh. A typical home currently uses 25 kWh each day, so this represent about a 50-percent increase in the electricity use. The cost of that electricity varies, depending on where you live, but if we use an average residential rate of 11.3 ¢/kWh, we get a daily cost of $1.35, or a monthly cost of about $40.

This cost needs to be compared with the cost savings of not using the required gasoline. If we assume that a typical equivalent gasoline-powered car would get 25 miles per gallon; and if we assume $3 per gallon, we get the monthly cost of $180 (50 miles/day x 30 days/month x $3 per g/25 miles/g).

For a complete examination of the economics, we would have to consider the incremental cost of the batteries. The added expense would have to be properly amortized over their effective lifetime. Both the cost and the lifetime are presently difficult to determine because the cost of batteries is not listed in the specification and because experience on the lifetime is limited. A very rough estimate might be that the batteries cost $10 000 and last for five years. This implies that the amortization cost of $166/month, neglecting any interest charge ($10 000/60 months)

Also to be considered is the cost of maintenance, which may be less expensive for an electric vehicle because of fewer moving parts. So the cost of electric vehicle ownership may be about the same as owning a gasoline-powered car.

Impact on the grid

The next question that needs to be asked is whether the power to charge the batteries of the one million electric cars is available on the grid. The answer to this question is a definite yes, since the charging would be done at night when the electricity demand is low. As a matter of fact, there is power available to charge many millions more.

According to the U.S. Bureau of Transit Statistics, for 2006 there were 250,844,644 registered passenger vehicles in the United States, with 135,399,945 of them classified as automobiles (excluding SUVs and pick-up trucks). In the future, one might expect that half (68 million) of those cars could be electric and used for commuting, in which case the extra power requirement during the night to charge them for six hours would be 136 000 MW (12kWh x 68 x 106/6 hr).

In 2009, the U.S. electrical grid generated 400 000 MW of electricity. Depending on the nighttime power requirement to meet other loads on the grid, the current grid could accommodate much of that extra load. For example, if a typical nighttime load reduction is 20 percent without charging EVs, then one could accommodate the charging of 40 million EVs without reducing power (68 million x 400 x 0.2/136).

If smart chargers are used that would allow timing control by grid operators, the load on the grid could be flattened, thus making maximum use of the baseload generators, which have the lowest cost.

Emissions impact

Finally, the question of whether the use of electric cars leads to reduced emissions needs to be addressed.

The use of electric cars in metropolitan areas would definitely reduce emissions locally, which is beneficial because that is where people live and work. The emissions are transferred to whatever emissions are created at the power plant location (which may be a distance away from the metropolitan area). Transferring the emissions to power plants would eliminate the unhealthy emissions of hydrocarbons, nitrogen oxides, and carbon monoxides from automobiles. The EPA states that “the personal automobile is the single greatest polluter, as emissions from millions of vehicles on the road add up”.

If electric cars are to be charged at night when they are not used, the emissions are created by the mix of power plants connected to the grid at that time (coal, natural gas, nuclear, hydro, solar, wind, etc.) Only nuclear, hydro, solar, and wind are emission free.

Solar photovoltaic array

Solar photovoltaic can make no contribution to charging electric cars, unless extra batteries are used for charging during the day. This may require several $10 000 batteries and many times that cost for the solar power system. That is a very high cost for the benefit of generating $1.35 worth of electricity each day.

Similarly, wind cannot be relied on to charge electric cars because it is intermittent. One could contemplate having several spare electric cars in one’s driveway waiting to be charged, with only one of them being available on any one day. The expense of that would be prohibitive.

For grids with ample hydro such as the Bonneville Power Administration, the charging of electric cars can easily be accommodated. The hydro power is reduced significantly at night, which is just when the power is needed to charge the electric cars. This is a very good fit. It is also very inexpensive since the extra water that would otherwise be wasted would be used to produce the extra power at night.

For grids with less hydro, it is likely that the maximum hydro power is used continuously, as it is a low-cost generator. For that situation, the peaking generators are likely to be fossil generators that need to operate longer during the night. Thus, the emission impact of charging EVs at night is the difference between the extra emission at the power plant (likely to be natural gas) and the emission from gasoline-powered cars. There is likely to be a net carbon emission benefit, but not a complete elimination of carbon emissions.

Brunswick Nuclear Energy Facility

Thus electric vehicle can have a significant impact on the reduction of unhealthy automobile emissions, but in order to decrease the emissions from the production of electricity in general, nuclear power plants are the only emission-free power generators that can have a significant impact. Currently, they produce 20 percent of the electricity in the United States, with coal’s share being 50 percent. That ratio needs to change in favor of nuclear plants by building more of them.

Decher

Ulrich Decher holds a PhD in nuclear engineering. He is a member of the ANS Public Information Committee and a contributor to the ANS Nuclear Cafe.

9 Responses to Economic and emissions impacts of electric vehicles

  1. Dear Ulrich, I enjoyed reading your economic analysis of EVs. I think your statement that wind cannot be used to charge EVs needs expanding concerning the difficulties that would be created by trying to do so. Let’s say that a smart grid could be used to link charging rates to EVs on the grid. Wouldn’t that work? If you think that model might not work, please explain why. Thanks, Gene Preston, http://egpreston.com

  2. Gene: That is a good question. A smart rid would enable grid controllers to time delay some loads which are not time sensitive. This is generally a good thing and it would tend to flatten the daily load variation. However, the charging of EVs is time sensitive. It must occur at night. If we accept that even a smart grid cannot store electricity, then the wind must blow every night to charge EVs. The idea that there will always be wind energy available from some far away place is not reasonable because of line looses.
    When the wind is blowing, there still needs to be spinning reserve on the grid in case it doesn’t. So the result is that wind cannot be counted on to add capacity to the grid to charge EV’s. It can only save fuel in other generators which need to be avalable regardless of whether there are windmills or not. For further information, I refer you to a recent article that I wrote on “Fitting Wind onto the Grid”.

    http://ansnuclearcafe.org/2010/12/09/fitting-wind-onto-the-grid/?like=1

  3. I think you are correct Ulidech. My background in modeling the reliability of power systems includes hourly simulations over one or more years. If I wanted to simulate wind plus a smart grid charging EVs, I would do it hourly using actual historical hourly wind data plus models of customer usage of their EV to see how smoothly of badly it worked. I suspect that at times the EVs would not be adequately charged up leaving the driver of the EV frustrated. Quantifying this would take quite a bit of study effort.

  4. “The hydro power is reduced significantly at night, which is just when the power is needed to charge the electric cars. This is a very good fit. It is also very inexpensive since the extra water that would otherwise be wasted would be used to produce the extra power at night.”

    Wrong!!

    At night the dam fills storing the power to be sold at daytime peak rates. Water is only ever dumped in the spring freshette or when required for fish habitat.

  5. Denis Beller

    We should keep in mind that everyone doesn’t work from 8 to 5. Many people work odd shifts, swing shifts, or midnight shifts, with many (most) of our factories running 24 hrs a day. In addition, many people don’t go home at the end of their shifts, sometimes being home less than 5 or 6 hours a day or night. Thus, to make this workable and widespread, we’re probably going to need some extra capacity and some workplace chargers (eventually for a fee of course). Let the market determine what’s required as the electric vehicles slowly assimilate into our ways of life.

  6. Bill Rodgers

    Seth,

    Dams are not one-size-fits-all category. There are storage dams and there are run-of-the-river dams as well as conventional dams. There are high head dams and there low head dams (high potential energy versus low potential energy).

    In the run of the river situation the water can’t be held back. Part of the river is diverted to a powerhouse and then routed back or the entire river is run through the powerhouse. Run-of-the-river dams are also low head by their very nature. For example the Lower Granite on the Snake River is a run-of-the-river, low head facility generating a max of 810MW. Its storage pool operating level is 5ft from el. 733 ft to el. 738ft. So it can’t be used to store water for some future demand and it is a major dam on the Snake River.

    http://www.cbr.washington.edu/crisp/hydro/lwg.html

    There are many dams both large and small similar to the Lower Granite in the Pacific Northwest where water can’t be held back for long periods of time nor stored in large quantities. Chief Joseph is an even larger run-of-the river facility at about 2000MW.

    However, even though they can’t be used for storage, their operational profile can be timed to meet peak loads or increased loads if EV’s become commonplace on a daily basis. The BPA operates the Columbia basin more in a run-of-the-river mode instead of a storage mode so water is always flowing through the dams and powerhouses.

    There are also issues of FERC requirements that each dam must meet. Depending on the dam, location, design, safety factors, etc FERC will issue operational parameters that must be met. One of the main parameters is a flow range to ensure proper water delivery downstream from the dam facility.

    So water will always be flowing through dams. The issue is how much and if that water passing through the dam will be used to generate power or spilled as the daily load profile changes. If EV loads at night are sufficient then water that was spilled in the past may be run through the powerhouse to meet the grid loading profile.

  7. Alfred G. Schoenbrunn

    Dear Uli: Your article provides a welcome initial look at the potential economic and emissions benefits of the coming electric car age. Its conclusion that more nuclear plants are needed should find support in further detailed evaluations. Thanks for a straight-forward and comprehenbsive review of our current status. Al schoenbrunn

  8. Yes there is a relatively small amount of run of the river installations around. Most commercial ones use weirs or Alpine lakes to store water over the weekend and during the night in order to maximize profits.

    BCHydro has 15 TWH’s of storage available to it and it uses it to store at night and weekends and dump by day creating large trading profits.

  9. Seth,
    You bring out an important point that deserves discussion. That is the difference between “Pumped Hydro” and “Conventional Hydro”. It is true that pumped hydro is used to store excess power capacity at night in lakes that have been constructed for that purpose. The water is released during periods of high electricity demand to help meet the peak load on the grid.
    In New England we have pumped hydro available which is able to generate about 5% of the grid capacity. We have daily grid load swings which can be as high a 40%. Pumped Hydro helps to smooth out the load swings that must be accommodated by other generators.
    In conventional hydro, which is the case on the Bonneville Power Authority, there is no pumping, and there is very little storage available to defer the reduced power to a later time when the need for power is greater. The reduced power demand is accommodated by closing the valves to the hydro turbines and diverting the water over the spillway, so the energy in that diverted water is wasted.
    On the BPA website, they actually tabulate the graphed data that they show. Just for curiosity I looked at the amount of energy that was diverted over the spillway during the week of February 21, 2011. It turns out that the average diversion was 19,000MWh during the hours of 9:00PM and 3:00AM (That is relative to keeping the valves open and generating 14,200 MW).
    This is why I claim that for grids with ample hydro, there is a very good fit for the charging of EVs at night. These vehicles are essentially running on hydro power and the emissions are completely eliminated.
    How many EVs could have been charged by that amount of diverted energy at BPA? That number turns out to be 1,600,000 EVs (19,000,000kWh/12kWh). That is more than President Obama’s call for one million EVs by 2015. Unfortunately for those of us who don’t live in the Northwest, there is a slight logistic problem.

    Ulrich Decher