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What about Kaya equation applied to automotive?

Gregory Launay - Last update: January 20th, 2013


What do we talk about?

The Kaya equation is a very simple equation proposed by a Japanese professor of the same name. It breaks down the carbon emissions of a given geographical area (a country, the planet, etc.). Products in very simple terms and talking. It is written like this:

Terms thus obtained are real and statistically known. Let us pause a moment on each of them.

  • the world's population: demographic prospects are, in order of magnitude, fairly well known; talking about 8-9000000000 in 2050
  • GDP per capita is measured in most countries, the increase is the main goal of most economic policies
  • energy intensity of GDP corresponds to the energy efficiency of the economy is the answer to the question "how much should we eat tons of oil to produce one point of gross domestic product? '
  • the carbon content of energy is a physical quantity known for all energies used

The benefit of this type of equation is to confront a global constraint (reducing CO2 emissions) and how to get it.
In this equation we see for example that all forecasts indicate increases for the terms "population" and "GDP per person" ... that does not go too in the sense of respect for the global constraint. But the equation allows us to set goals for other parameters "energy intensity" and "carbon content of energy."

You have understood the explanation text, we now turn to practical work in applying it to the domain that interests us most here know the car.


CO2 emissions related to the automobile

Posing an equation of the same type centered on the automobile that we can write:

Begin by explaining each term. The carbon content of the energy within the field of energy companies. This parameter is known to fossil fuels for oil is 250 grams of CO2 per kWh. For electricity it will depend on the means of production used for biofuels it will depend on the sector, etc.. Car transport is now almost exclusively dependent on oil. This parameter is now known and constant.

Energy intensity per kilometer within the field of automobile manufacturers. It depends on the gross energy requirement (called energy wheel) which is the weight of the car, its aerodynamics, etc., and the overall energy efficiency of the vehicle. This parameter is the only one on which we have so far is really dramatically improving yields, increased energy needs crude partially masked the gains. This parameter is around 900 Wh.

We can combine these parameters into a single is "CO2 emissions per kilometer" with the world average is about 225 grams.

The last two parameters we are out of the realm of technology. The number of vehicles in circulation and the distances they determine the level of global mobility, which itself has a significant impact on our lifestyles on the world economy, etc.. It is clear that automakers do not have much control over these settings, but they have a vested interest that they continue to grow!

So basically we can now write:

The whole problem is then to enforce global constraints on CO2 emissions while allowing mobility to continue its development, that is to say to the two terms of the right to grow ...


What programs in 2020?

Begin by thinking in trend, that is to say, to describe a seamless high near future.

On the number of vehicles in circulation, trend projections give 1.3 billion in 2020.

For what is the average distance traveled annually, projections seem less simple to make. It is now about 15,000 km with many differences.

Evolution of the average distance per vehicle (LCV VP) for different countries from 1970 to 2000 - Source: International Energy Agency, 2004

This graph shows the evolution of the average annual distance for a number of OECD countries. One sees that the values ​​range from 10,000 kilometers to nearly 20,000 in Japan for the countries of North America and Denmark and Finland.

We also track this series statistical mean value seems fairly stable over the 30 years observed. There is indeed a more or less marked decline during the oil shocks but with little impact on the average. There are also variations that do not seem related to fuel prices as the sharp decline in Japan and the sharp rise in the United States.

Recent developments in the United States seems to show a slight inflection in connection with the rising price of oil, but with an elasticity actually quite low ... at least for now.

Evolution of the average distance per vehicle (VP) in the United States - Source: U.S. Energy Information Administration and Department of Transportation

In France, after going through a peak at 14,000 km in 2001, the average distance decreased gradually (about 1.3% per year) and is located in 2008 to 12,745 km.

The evolution of this variable is not easy to anticipate and probably depends on many factors: urbanization, transportation, fleet characteristics, etc.. The simple change in weight of different fleets (increase in the United States, decreased in Europe and Japan) will change the average.

That said, in view of changes recorded since 1970 and major non-crisis, it seems silly not to consider it as constant over the next 10 years.

The last term "CO2 emissions per kilometer" is calculated for regulatory purposes. Existing commitments by states could at best to reduce average emissions from 225 to 170 grams of CO2 per kilometer by 2020.

Evolution of consumption of global fleet by 2020 - Author's estimate

Such a scenario would provide for 2020 global CO2 emissions for cars is about 3.3 gigatons just near current emissions.

Clearly, this means that all efforts to reduce CO2 emissions from vehicles might just be able to compensate for the increase of the fleet. Certainly this is a much more optimistic than in the past or believed emissions very significantly but is it really up to the challenge? I remind you that to comply with the recommendations of the IPCC CO2 emissions should be divided by three in 2050 ...

What solutions for compliance with the IPCC in 2050?

Although this scenario allows a stabilization in 2020, a break is necessary to achieve the goal by 2050. Returning to our equation and look at the different scenarios that could allow us to meet the constraints of the IPCC.

The first scenario that I call "technology" is to think that the constraint is attainable only by technical progress and the growth pattern of mobility should not be put into question.

In this scenario, the park continues to grow to 2 billion vehicles in 2050 and the average distance traveled each year remains constant.

Enforce the constraint means then divide the IPCC CO2 emissions per kilometer by a factor of 6.

The current fleet average emits 225 grams of CO2 per kilometer. If we divide by 6 gives average emissions of 37.5 grams of CO2 per kilometer by 2050 (or about 1.6 liters per 100 kilometers, or 145 mpg). The average age of cars in the world is probably more than 10 years, it would require that the average CO2 emissions of new vehicles sold is about 40 grams of CO2 per kilometer by 2040. I recall that these emissions should hear "well to wheel" that is to say integrate CO2 emitted to produce electricity for future electric vehicles or hybrids!

Another way to meet this requirement would obviously reduce the overall mobility related to the automobile 3 .... This brings us back to the same level as in 1950 (before the thirty glorious years!).

Technological revolution or bankruptcy of the promise of mobility for all ... that is the challenge ahead.