Life Cycle Analysis of Bio Foods

A few blogs ago,  I wrote about the life cycle analysis (LCA) of Compact Fluorescence Lamps (CFL’s,)[1]. CFL’s do “consume” during their life indeed about 5 times less electricity than incandescent light bulbs (and CFL’s live about 4 times longer). However, the manufacturing of CFL’s is much more complicated and therefore environmentally more demanding than classical bulbs and rightfully the question was raised that when you sum it all up would the environmental advantage still hold? After a careful and detailed LCA, a team of Australian researchers came with the answer: a big yes!

However,  it was pointed out by the researchers at the University of Ghent[2], Belgium, that one needs to look not just at the environmental impact (for  factors such as global warming, ozone depletion, toxics emission, acidification, etc.) of a certain product but also need to take into account  resources such as organic and inorganic, fuel and feedstock, renewable and non-renewable, energy and materials. It is here where thermodynamics kicks in using the concept of entropy[3] (as already suggested by Nicholas Georgescu-Roegen[4] quite a while ago). Entropy, can be used to describe the degradation of resources during the manufacturing and actually usage of products. One can say, very roughly, that the faster and further away from equilibrium a certain production process is done, the more energy is degraded and made not-available anymore to do further work. This is described by an increase in entropy and is non-reversible, i.o.w. high quality energy (such as energy contained in fossil fuels for that matter) is turned into low quality energy (heat).

This sort of analysis is then used to study the environmental impact of bio-foods versus large scale agriculture produced foods. And sure enough you can find situations where bio-foods (because of their poor yields or their transport over large distances) have more negative impact on the environment than have traditional produced foods. It was found[5] that if bio-beans are locally produced they are environmentally better than conventional produced beans. But when the beans needed to get transported from other areas to make it to our stores the balance can easily change and even reverse the situation! Bio-potatoes are always worse than conventional potatoes because they have such a lower yield per surface area land[6].

Therefore, before drawing conclusions on the impact of a given process or product on the environment or resources a careful evaluation (LCA) needs to be done. Such an evaluation is not a trivial matter at all and can only be done by qualified people.

 

© Copyright 2009, John Schmitz

 

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[1] https://secondlawoflife.wordpress.com/2008/10/05/compact-fluorescence-lamps/

[2] http://pubs.acs.org/doi/abs/10.1021/es071719a

[3] As a matter of fact a concept of « exergy » is used but it has a very close relationship to entropy

[4] https://secondlawoflife.wordpress.com/2007/04/28/nicholas-georgescu-roegen/

[5] http://www.standaard.be/Artikel/Detail.aspx?artikelId=4I2B40SO

[6] See also: https://secondlawoflife.wordpress.com/2007/07/28/entropy-and-the-food-chain-part-i/ and https://secondlawoflife.wordpress.com/2007/08/22/entropy-and-the-foodchain-part-ii/

 

http://libproject.net/science/the-second-law-of-life.html

Nice review on www.libproject.net:

It is thought that of all the animals on planet earth, there is only one that can build a fire and has developed a realization of itself so that it can ask and answer the questions: Who am I? What is this fire that burns within me and before me? Why does the flame rise, and why am I warmed before this fire of time? John Schmitz’s book on thermodynamics is designed for the mature general science reader who has developed a general knowledge of the physical science literature that does not require mathematics beyond the arithmetic of writing a bank check. The overall objective of this short book is to introduce the reader to the thermodynamic concept of entropy and its many ramifications ranging from the micro-quantum world to the gross dynamic relativity construction of the universe. To prepare the reader for this entropy concept he lays down a foundation which closely follows the early historic development of thermodynamics. In preparations for reading this book one should first carefully read through the two-page table of contents. Dr. Schmitz makes statements and/or asks questions which he then answers in the text of the book drawing the reader into his web of understanding which demonstrates the beauty and his love of thermodynamics. One very quickly realizes that in writing this book the author has given quality time in considering carefully the answers to his questions. There are footnotes that are well worth reading which amplify selected points including historic events with specific dates. You will find yourself going back to the table of contents and index pages to pick up action items in your reading. Indeed, before you start reading this book you should browse the table of contents to determine the extent and usages of entropy.

Taken from: http://libproject.net/science/the-second-law-of-life.html

 

Energy and the Internet

Recently a Harvard University scientist, Alex Wissner-Gross, was quoted in TimesOnLine  that each computer search of the internet could produce as much as 7 gram of CO2 (the journalists of TimesOnLine compared that to boiling a kettle of water that would produce about 15 gram of CO2).[1] Google responded that the calculation was not right as an average search would only last about 0.2 second and that that would then equate to about 0.2 gram of CO2.[2] Clarifications later on revealed that Google referred to a one time search hit whereas Wissner-Gross referred to a complete search that encompasses several hits. Further more Google pointed out that the company has several environmental footprint reducing initiatives underway.

But it remains of course interesting to know how much energy the ICT infrastructure needs. It has been suggested[3] that this could be up to 2% of the world’s total greenhouse emissions (comparable to the amount produced by air transportation).

Closer to ourselves: who knows how much energy your PC at home takes up? Well I did not know the answer and I have monitored my PC  for a week. I simply hooked up a kWh meter between the outlet and the PC/printer/external HD/scanner assembly. The lucky number is: 6.3 kWh per week. At night I switch the PC off and during day time I put the PC in standby after 20 minutes of idle time. I also compared this figure with my freezer/fridge combination:

1.             PC                                 6.3     kWh/week              327 kWh/year
2.             Freezer/Fridge       38.1   kWh/week           1981  kWh/year

Then also good to know is that the electricity need of an average Belgian family is about 3500kWh per year.[4]

What we conclude from this that indeed PC’s and accessories do require a substantial amount of energy that is not small compared to other household appliances. A critical look at standby regimes and shutting down overnight seems to be wise.

© Copyright John Schmitz

 

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[1] http://technology.timesonline.co.uk/tol/news/tech_and_web/article5489134.ece

[2] http://googleblog.blogspot.com/2009_01_01_googleblog_archive.html

[3] Recent Gartner report, see reference 1

[4] http://www.vreg.be/nl/04_prive/05_meteropneming/04_verbruik.asp

 

What Max Planck Thought About Thermodynamics

 

Around 1900, Planck was an expert in classical thermodynamics and wrote many articles and books about that theory. The concept of entropy especially held his interest, but he published also in the fields of dilute solutions and thermoelectricity. Of course, being a time-oriented fellow, he was familiar with the results of Boltzmann’s works. However, being a physicist of the “old school,” he was raised without having the concept of atoms in his scientific toolkit. In 1891, for instance, he and Ostwald had a discussion with Boltzmann at a conference where Planck stated that thermodynamic methods without the incorporation of atomistic models were sufficient to explain those days’ physical observations. Also, Planck was not very pleased with the statistical approach of Boltzmann [1]. His main objection was that Boltzmann’s statistical approach allowed that the change of entropy for spontaneous processes could become negative (i.e., an entropy decrease), although at an extremely low probability (see Chapter 3 for more details on this topic).

But Planck was wrestling at the turn of the century with understanding black body radiation behavior. Since 1861, when Kirchhoff[2] first described a black body, the radiation behavior was studied and described by a slew of well-known physicists such as Wien, Stefan, and Boltzmann. However, all these attempts led only to a radiation law that had very limited applicability. The breakthrough in Planck’s understanding came when he started to use Boltzmann’s statistical approach. In fact, it was Planck who wrote the current well-known form of the Boltzmann equation, S = k lnW, in his famous 1901 article[3] . It was in this text that Planck proposed that the radiation might consist of small packets (quanten) of size hv. This was the beginning of quantum mechanical theory. Planck struggled a long time with his own thoughts, since they were so in contrast with the classical belief of continuous energy. For some time he saw his quanten approach merely as a mathematical trick, but slowly became convinced that energy in nature was indeed discrete, rather than a continuum. It also took some time before his ideas were accepted in the scientific community[4]. It was no less than Einstein who used the quanta principle to explain the photoelectronic effect, as we will see shortly.

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[1] Flamm, Dieter, “Einführung zu Ludwig Boltzmanns Entropy und Wahrscheinlichkeit”, this is an introduction of Entropie und Warscheinlichkeit, 1872-1905 von Ludwig Boltzman in Ostwalds Klassiker der Exakten Wissenschaften, Band 286, Verlag Harri Deutsch, Frankfurt am Main (2000). This book is contains a nice compilation of the most important articles from Boltzmann in original version.

[2] It’s likely that Planck got his interest in black body radiation from Kirchhoff, who was his teacher. In 1889, he succeeded Kirchhoff as professor at the University of Berlin.

[3] Planck, Annalen der Physik 1901

[4] Interestingly, Planck once remarked that a new theory gets accepted not because its opponents become convinced, but because they eventually die and new generations of scientists, unhindered by historic baggage, simply assume the theory is true (provided that it is still supported by experimental facts)!

© Copyright 2009 John Schmitz

 

Green Cars

In an earlier blog I wrote that, short term, the best way to contribute to the planet’s energy issues is by reducing our energy “consumption”. We saw also that road transportation claims about 20% of the total energy bill. In addition we know that a substantial amount (about 70%) of the energy liberated from the car fuel is wasted mainly in the form of heat to the environment.[1] The power required  to move the car is substantially. Let’s take as a quite familiar reference: an incandescent lamp of 100 Watts. Only a small fraction of the 100Watts is actually converted into light (ca 10%) the rest is converted into heat. From experience everybody has a sense of how much heat a 100W bulb generates. After a few minutes the bulb is very hot and you could burn your fingers when you touch it. To compare, cars have engines of say between 50 and 150 horse power (hp). In the table below I have converted the hp’s into kW:

 

            50 hp   =          36 kW

            100 hp =          74 kW

            150 hp =          110 kW

 

Thus a 50 hp car consumes 360 times as much energy as our light bulb! And a 150 hp car even more than 1000 times. It is therefore clear that if we could save only a little bit on this waste, that we are talking immediately about large amounts of energy savings.

On top of the heat waste, cars propelled by internal combustion engines produce per km also an amount of CO₂. And we all know what the impact is of CO₂ on the earth ecosystem. To give you some feeling: one liter of petrol produces 2400 grams of CO₂. At room temperature and one atmosphere that is about 50 liters. A typical car will burn about one liter of petrol per 20 km. Therefore, reducing CO₂ will then directly reduce the energy consumption.

The European Commission and governments have from that point of view put quite strict regulations in place for CO₂ emissions of cars. These regulations have a two prong approach: tax reduction for the buyer of clean cars and penalties for the car producer if the car does not meet minimum emission criteria. The criteria for the car manufacturer are: an average CO₂ emission in 2012 if less than 130 gr/km. The penalty to pay by the car manufacturer is 20 E/gr in 2012 but increasing to 95 E/gr in 2015. On the other hand  car buyers can get an appreciable tax (up to 5000 Euro’s) cut when buying a new car that has a low CO₂ emission rating.

Sensible measures I would say.

 ©  Copyright 2009 John Schmitz

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[1] Actually less than 20% of the energy from the fuel becomes available to deliver mechanical traction of the car! Other losses are fiction, idling, standby, accessories and AC.

 

“Saving” Energy

Can we “save” energy? Of course not. We cannot “save” energy as the first law of thermodynamics explains: energy is conserved no matter what we do. The only thing we can do to help solve the planet’s energy problem is to reduce the speed with which we degrade the quality of the energy sources available to us. And indeed the best way to accomplish that is to “use” as less as possible of this high quality energy. Examples of high quality energy are fossil fuels, nuclear fuel, solar or PV energy, wind energy etc. The common factor in all these different sources is that the energy is concentrated in a relatively small volume. A typical example of low quality energy is heat (most of the times at least). Why? Heat is difficult to maintain and tends to leak away and thus disperses over a large volume. One joule of heat remains one joule of energy regardless whether the volume in which it is contained is one cubic cm or the entire galaxy. So where is the problem? Here is where the Second Law of thermodynamics kicks in. High quality energy conditions have a low entropy value whereas low quality energy has a high entropy value. The entropy law teaches us that with each “use” of energy the entropy increases (and thus the quality is decreasing) and that there is no recovery back from that. In other words quite a fundamental limitation and no technology can help you overcome that Second Law!

There are two ways how we can help ourselves to slow down the ever ongoing energy quality degradation.

1) The quickest one is simple: reduce the need for energy as much as you can! Let’s have a look at the energy ‘consumption” breakdown (IEA 2008):

Category	Relative energy usage (%)
Industry	32
Road transportation	20
Air/sea transportation	6
Agriculture	3
Services	7.8
Buildings	28
Fertilizers	5

For example, as long as the fuel “consumption” in the USA per km is still about 40% higher than that in Europe it is clear where the focus needs to be. Also, note that about 20% of the total energy needs goes into road transportation. Thus if we would start to drive energy efficient cars, it would cut 10% of the US total national energy bill! No needs for new inventions, just take what exist already today!

 Because of the high fuel prices there have been proposals from politicians and governments to reduce taxes on fuels. This is precisely the wrong measure to implement. What should be done is to lower the tax or subsidize more measures that will result in less energy needs such as home insulation, fuel efficient cars and fuel efficient heating units. The best way to solve the energy problems of the planet in short term is reducing the need for energy in the first place!

 2) The other way to mitigate the energy problems of the planet, but then more long term, is the use of renewable energy sources, basically all based on the solar energy that reaches the earth. The sun is such a rich source. Realize that the energy influx is many times higher than the world energy need. There are massive problems to overcome such as costs price and, more importantly, the capacity of our power grid that can accommodate these variable energy sources. This will ask for clever storage means that must come along with the renewable sources.

© Copyright 2009 John Schmitz

 

Non-Equilibrium Thermodynamics

Classical thermodynamics, the dynamics of Carnot, Clausius, Boltzmann, Gibbs, Joule, Kelvin and Helmholtz, is often also called equilibrium thermodynamics. Indeed, frequently we are alerted that classical thermodynamics holds only for systems that are in equilibrium (or at least close to equilibrium). But why is that? For instance, the First Law of thermodynamics, the conservation of energy, holds for any system you could argue. Certainly this is true. But how about the Second Law, the law of ever increasing entropy? Well here it becomes already a bit trickier since the change in entropy for a given change in the system parameters is defined as:

ΔS = ΔQrev / T

where Q_rev stands for the reversible exchanged heat and T is the absolute temperature. Thus the change in entropy between start and end state of a system can only be calculated when designing a reversible path from the beginning to the end. The result of all this is that calculations, as they are done by engineers to determine efficiencies, result is upper limits and actual performances are lower.

 However, there are ways to overcome the entropy problem described above. Important  to realize here is that the system properties that we use to describe a system in thermodynamic terms have some peculiarities. Whereas properties such as volume, mass and energy can easily be calculated for any system regardless whether it is in equilibrium or not, parameters such as pressure, temperature, and as we saw above, entropy, are not so straightforward to define for systems that are not at equilibrium. For example if we take two heat reservoirs at different temperatures and we connect them with a heat conducting rod, heat will flow from the hot reservoir to the cooler one. But the temperature in the rod is not so easily defined and for the system as a whole certainly not. The same is true for liquids where we have a thermal gradient established or where we have a pressure gradient because there is a mass transport going on.

 These kind of problems where already noticed in the early days of thermodynamics. Just in the beginning of the second half of the last century a new chapter was added to thermodynamic theory, namely that of non-equilibrium thermodynamics. Important names connected to this are Prigogine and Onsager, both earned the Nobel price for their work. Key assumption done is that the system is broken down in subsystems such that in the subsystems a condition called “local equilibrium” can be assumed. In such a subsystem the internal states can relax much faster to equilibrium than the change in parameters such as pressure and temperature. In general this approach worked well when the systems were not too far from equilibrium.

 But science moves on and new situations were found where also the approach of Onsager and Prigogine no longer were valid. In a recent article in Scientific American and in other articles by J.M. Rubi it is argued that in many relevant systems such as molecular biology and in nanotechnology systems the conditions can be far from equilibrium and the question arises whether the Second Law will still hold up. It appears that if the description of the system under study is done in a multi-parameter space spun by all the relevant parameters in addition to the spatial coordinates that then non-equilibrium thermodynamics can be applied again. And indeed no reason to get worried, the Second Law still holds up.

 As I mentioned  in previous blogs, the discussion on the Second Law is also today still very lively even 150 years after its discovery and description.

 Further reading:

1. J.M. Rubi, The Long Arm of the Second Law, Scientific American, 41, Nov 2008
2. J.M.G. Vilar and J.M. Rubi, Thermodynamics “beyond” Local Equilibrium, Sept 2001 (http://arxiv.org/abs/cond-mat/0110614)
3. J.W. Moore, Physical Chemistry, pp 356, 1978, Longman Group Limited, London, ISBN 0 582 44234 6

 

Wasting Energy? Why?

There are many instances that we can see that in our attempts to transform energy into as much as possible usable work, we are always left with this “rest” amount of heat that we can not use anymore to generate even more work¹. Clear examples of these imperfect transformations are the coolant radiators in our cars and the cooling towers of many factories or power plants. In power plants that use fossil fuels we can have an efficiency as poor as 50% or often even lower, meaning that only 50% of the energy enclosed in the fuel is converted into electrical power, by means of burning fuel, heat generation that leads to steam and steam that will drive then turbines and generators. 50% or less is that not a shame? Of course the question arises why that is the case?

Why can we not convert for the full 100% the energy enclosed in the fuel into utile work? Well it is here that the Second Law of thermodynamics kicks in, also known as the entropy law. But before we go deeper into this entropy law first a bit more about the First Law of thermodynamics. The First Law is nothing more than the law of conservation of energy. Energy can be present in many forms (chemical, heat, work, electrical, nuclear etc etc) and the total amount of all this energy in the universe is constant. The First Law will not object to convert a given amount of energy fully into work. Unfortunately we never observe this attractive situation. The answer why that is so can be found from an analysis of the entropy law.

What is entropy? Entropy is a concept discovered while people were answering “simple” questions such as why heat only streams from warm to cold places. Another question that came up around 1800 was caused by the growing popularity of steam engines. Steam engines can also be called heat engines because they convert heat into work. Another example of a heat engines is a car engine. Steam engines where used in England to pump water out of the coal mines, a job that was done by many workers day and night before steam engines became available. To keep the steam engine running, fuel (such as wood or coal) was burned to generate the steam. While the steam engine was gaining ground, many improvements (for instance James Watt was able to improve efficiency with about 25%) were done that increased the efficiency of the steam engines considerably. Therefore much more work could be obtained from a given amount of fuel.

While this went on there was a young French military engineer, Sadi Carnot, who asked himself the question whether there was perhaps an upper limit to this efficiency. To answer that question he carried out a careful analysis around 1825 using a simplified model of a steam engine². The result of his analysis was that the upper limit of the efficiency was only determined by two factors: the temperature of the heat source (the steam) and the temperature of the heat sink (the location where the steam was condensed, for all practical matters the outside air). More precisely he found that the amount of heat, Q_h, taken from the heat source at temperature , T_h, is related to the amount of heat given up at the heat sink, Q_c, at temperature T_c, as: Q_h/T_h = Q_c/T_c. Although he did not coined the factor Q/T as entropy (that was done by Rudolph Clausius around 1850) he clearly laid the foundation for scientists such as Clausius who came to the conclusion that “something was missing” and was needed in addition to the First Law . That something became later the Second Law of thermodynamics.

The best possible efficiency of the steam engine was then shown by Carnot to be equal to (T_h-T_c)/T_h (an atmospheric steam engine efficiency is therefore limited to about (373-272)/373 = 25% efficiency).

The work of Carnot showed very clearly that in order for a heat engine to work you MUST have a heat source at high temperature and a heat sink at colder temperature and that the heat disposed at the heat sink can NEVER generate any work anymore unless you have another heat sink available at an even lower temperature. Also, from the fact that Q_h/T_h = Q_c/T_c, it becomes clear that in an heat engine you MUST give up an amount of heat, Q_c, to the cold sink no escape. That is the fundamental reason for having the efficiency of the heat engines less than 100%! We can also see now that the efficiency of heat engines will increase if we make the temperature difference between the heat source and heat sink as large as possible.

See for more background on this topic:

https://secondlawoflife.wordpress.com/2007/08/28/carnot-efficiencies/

https://secondlawoflife.wordpress.com/2007/05/25/can-we-recycle-energy-or-the-role-of-law-of-entropy/

 

© 2008 John Schmitz

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1. With work we mean here the ability to lift weights, or to to turn wheels which in turn can rotate shafts.

2. This model is well known as the Carnot cycle.

 

Compact Fluorescence Lamps

Lately the compact fluorescent lamp (CFL) is strongly recommended to replace the incandescent light bulbs (ILB). The main reason is because CFL’s can save a considerable amount of energy during their lifetime; at least that is what is claimed.

Before scrutenizing that claim closer, first a few facts about the lamps it self. The classical ILB, that has been with us basically since the invention of generating light out of electricity operates through a simple principle. A (tungsten) wire is heated through the passage of current to a temperature of about  3000 °C. At that temperature the wire (acting as a black body) emits almost white light. In contrast, the CFL is much more complicated and operates on the principle of a gas discharge. When a gas at lower pressure is subjected to the passage of a current a complex chain of events takes place that eventually results in the generation of UV radiation. When UV light hits a proper chosen phosphorous layer (coated on the inside of the glass tube) the UV light gets converted in visible light. The phosphorous layers are now so sophisticated that the color of the light of a CFL matches that of an ILB. CFL’s can live 4 times longer than ILB’s.

But there is more to tell. A CFL of  18W generates as much light as an ILB of 100W. Thus the amount of electricity needed to drive the lamp is a factor of 5 lower for the CFL and that is at first sight of course a big advantage. Certainly if you realize that about 25% of the electricity generated in the world is used for lighting purposes! However, if you hold an ILB in one hand and a CFL in the other hand you feel immediately a big difference in weight. This is because a CFL is much more complicated to operate than an ILB. A CFL needs an electronic circuit (called a ballast) to ignite and maintain the gas discharge in the tube. This ballast contains a substantial number of components. Thus the question arises if you take into account all the energy for manufacturing, shipping and dispose a CFL, will the energy balance then still be in favor of this lamp versus that of the ILB?

The answer to such a question can only be obtained by a careful Life Cycle Analysis (LCA). Several LCA’s have been done for CFL’s and ILB’s. A recent one is done by David Parsons[1] from the university of Southern Queensland, Australia. In the rest of this blog I quote a few of his conclusions. In an LCA many energy and environmental aspects of a given product are analyzed:

• Components, processes, materials and quantities used
• Manufacturing
• Packaging
• Transportation
• Energy used in retailing and wholesale
• Energy usage during usage
• Energy losses in transmission lines
• Impact assessment on environment
• Disposal

Parsons does then a careful analysis of the two lamps for the items listed above. His conclusion is straightforward: “CFL’s are a significant better source of light from an environmental point of view than ILB’s maily because of their much more efficient use of energy”. He also touches on the problem that CFL’s contain a bit of mercury (about 3 mg)[2] that may pose a problem during disposal. However, he compares that with the amount of mercury that is emitted to the atmosphere by coal fired power plants. Again he comes to the conclusion that also on this aspect CFL’s outperform IBL’s with a factor of 5 in terms of environmental impact: “This analysis serves to confirm that the claimed environmental benefits of CFL’s over IBL’s is largely true and further that it is true on almost any measure…”

That is good news for the planet I think.

2008 © Copyright John Schmitz

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[1] Parsons, David. “The Environmental Impact of Compact Fluorescent Lamps and Incandescent Lamps for Australian Conditions”, The Environmental Engineer 7(2): 8-14 (2006).

A link to this article: http://www.ecobulb.com/Files/Report_CFLLCADataSSEE_0706.pdf

[2] The mercury is needed to facilitate ignition of the gas.

 

Hybrid Electrical Vehicles

A hybrid car is a car that uses more than one power source in order to propel the vehicle. These sources can be combustion engines (of course), an electric motor, a sail or human power. In this blog we will focus on HEV’s (Hybrid Electrical Vehicle), vehicles where an electric motor and an internal combustion engine will do the work. Several configurations are possible with the electric motor and the combustion engine[1]. HEV’s are not just applied in cars but also in diesel locomotives or in city public bus transportation. The biggest limitation of a HEV is its action radius. However, from studies it is known that 80% of the car owners on average drive less than 40 km per day. It is in these situations that HEV’s can work out quite OK.

But why would we ride an HEV in the first place given the limitation in action radius? There can be several advantages of HEV over pure combustion engine propelled cars. These advantages are mainly visible in terms of reduced particles, nitrogen di-oxide and noise generation but then locally. That local impact should not be underestimated as cities are often struggling with the environmental quality and traffic plays an important role in this.

But of course an HEV needs electrical re-fueling. Here we can ask three important questions[2]:

• 1) Will a HEV generate less greenhouse gases than a traditional fossil fuel powered car? A middle size car will consume about 5 to 6 liter of Diesel per 100km. A similar size HEV needs about 20kWh/100km. Calculation show now that the electricity needed by the HEV and delivered by a coal fired power plant generates about the same amount of green house gases (770-840 gr/kWh) as the fossil fuel powered car per 100km. And of course, when the power plant is using renewable electricity generation then the balance will turn quickly more favorable for the HEV in terms of green house gas generation. This may turn out to be the biggest advantage of HEV’s, not only from an environmental point of view but also from a reduced dependency on oil imports point of view.
• 2) Can the power grid handle the extra load to charge the HEV’s? This question is answered for the situation in Germany. It is expected that it will take at least till 2020 before there will be one million HEV’s on the road. They will consume about 2 TWh/year[3] and that is only 0.3% of the total yearly electricity production in Germany.
• 3) Will the cost price of an electrical km be competitive with a fossil km? Actually yes. Again assuming a fuel consumption of 6 liter/km and a price of 1.2 Euro/liter, the fuel cost per kilometer is then 7.2 ct. The HEV needs 0.2 kWh/km, thus assuming that we pay the same amount per kilometer, the driver has a budget of 7.2/0.2 = 36 ct/kWh. Compare this with the actual price for electricity of about 18 ct/kWh and you have to conclude that electrical driving is indeed cost effective and can potentially be much cheaper than fossil fuel transportation.

Thus, all in all no roadblocks for HEV as long as it concerns the environment, the power grid and the economics.

 Copyright © 2008 John Schmitz

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[1] Such as a serial or a parallel configuration of the power sources, see for more details: Robert Bosch GmbH, “Autoelektrik, Autoelektronik, Friedrich Vieweg &Son Verlag/GWV Fachverlage GmbH, Wiesbaden (2007)

[2] Recently a German study that addresses these and many other questions appeared that is worth reading: Höpfner U., Merten F., Elektromobilität und erneuerbare Energien, IFEU Heidelberg und Wuppertal Institut, Wuppertal, Nov 2007. The data I mention under 1, 2 and 3 come from that study.

[3] Assumed here is 2000kWh/HEV and that is about 10000 km per year