Global Warming Is It Real?

We all know the facts: the earth is warming up. Al Gore has put quite some convincing facts together in his book “An Inconvenient Truth”. Right?

Mmmmmm…… sometimes you can find some counter arguments from credible scientists[1]. In an article from Salomon Kroonenberg[2], a geologist,  he argues for instance that for the last 10 years the average temperature on earth has not increased. It peaked in 1998, most probably because of an overactive El Nino. However, the CO₂ levels did increase in that period but at the same time the activity of the sun was changing as well. And the activity level of the sun is known to have an impact on the temperature of earth. In the period between 1945 and 1975 the average temperature decreased while the concentration of green house gases increased. He brings forward several other examples where there is no correlation between the climate change and the greenhouse gases. For instance he points out periods in history where there have been dramatic changes in climate while the atmosphere did not change. Kroonenberg’s point is that there are many other mechanisms that have changed the climate in the past and at speeds much larger than what we observe now. His advise is therefore that we better adapt to the changing climate and find ways to cope with that.

But what about the average temperature of the earth?  How sure can we be about that crucial parameter? In fact it appears not to be such a trivial job to monitor the average temperature of earth and certainly not when you want to see one degree of difference over a long period. Temperature monitoring of the oceans was done for quit a while from ships. American ships typically measured the temperature of the water sucked into the inlet of the cooling funnels of the ship whereas English ships simply would use buckets to take a sample of the water and stick a thermometer in it. It proved that the American method gave a too high of a value (about 0.3°C ) whereas the English method gave a too low of a value. Temperatures that are measured at the surface of earth can have many flaws such as changing environment (urbanization) or changing station locations. See for more details on this reference.

There are also measurements taken by satellites. Satellite data have the advantage that they are truly covering the entire globe but do span a relatively short period, something like only 30 years. One of the institutes that generates satellites temperature data is the University of  Alabama of Huntsville.[4] In the figure below you can find the temperature recorded at globe level since 1979, I have averaged the monthly numbers per year. The year 1998 looks indeed, as mentioned above, as a maverick year, but let’s for this discussion not spent time on that observation. I believe that it is more important to note that there appears to be two periods of different behavior. The period from 1979 till 1997 seem to be a stable period with an average temperature of -0.027°C and the period from 1999 till 2007 seem to show a still increasing trend with an average temperature in that period of 0.216°C (substantially higher than the previous period). So the claims found in the press today that the temperature of the globe did not increase within the last 10 years is perhaps true but on average the average temperature in the last 10 years is substantially higher then in the previous 20 years. But let’s not forget, the time span we are discussing here is still awfully short at geological timescales.  So be careful drawing conclusions one way or the other would be my advise.

 

 

Average Global anual temperature. Data taken from the University of Alabama at Huntsville

Copyright © 2008 John Schmitz
 

[1] http://www.telegraph.co.uk/opinion/main.jhtml?xml=/opinion/2006/04/09/do0907.xml

[2] http://www.politicsinfo.net/forum/about47859.html

[3] http://www.theregister.co.uk/2008/05/02/a_tale_of_two_thermometers/

[4]http://climate.uah.edu/

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Bright Future for Solar Photovoltaic Electricity?

Almost every week you can read about efficiency improvements of solar cells. For example on February 25, 2008 the Belgium research organization IMEC announced that they had taken up the efficiency of a single junction GaAs solar cell to a record 24.7 percent conversion rate. As a comparison, mono-crystalline silicon based solar cells (still the mainstream material for PV generated electricity) run at an efficiency of about 20%.

On March 24, 2008 the US Department of Energy’s National Renewable Energy Laboratory reported an efficiency of 19.9 % for a thin film solar cell based on copper-indium-gallium-diselenide material[2]. This comes close  the efficiency silicon solar cells. On April 1, 2008 there was a statement by the Swiss Federal Institute of Technology that the efficiency of so-called Gratzel cells could be improved to 7.2%[3]. That seems to be a low number compared to the ones quoted above. But Gratzel cells are very cheap cells, compared to mono-crystaline silicon and GaAs semiconductors, because they are based on thin film semiconductor materials deposited on low cost glass substrates.

In all these cases the main aim is that the cost of the electricity generated by the PV cells will be lowered and to bring it at parity with fossil based generated electricity. This is quite in line with the discussion in my blog from March 24; where it was argued that PV electricity would reach grid parity around 2015.  The cost per generated kWh is determined by the cost of the PV installation itself and its operational costs. To give you some impression of what makes up the costs of a PV system have a look at the breakdown below.

 

More than 40% of the total system price is caused by the costs of the PV cells. It is therefore important to have research aiming at improving the efficiency and to look for solar cells that cost much less than the silicon based systems. Today the price of PV electricity in the US is, depending on the solar cell technology used, about 3-4 times as high as the average grid electricity[4]. It is therefore that in some parts of the world governments subsidize solar energy. The best example is perhaps Germany[5]. One of the subsidy measures taken in this country is that of a “feed in tariff”. Owners of roof mounted PV systems can sell their surplus of electricity back to the bulk producers for a generous price that is fixed for 20 (!) years. These kind of measures and others have made Germany the leading country in the world in terms of absolute installed renewable energy capacity (in 2006: 25 gigawatts of which wind is 20 gigawatts and solar about 3 gigawatts). In 2007 6.7% of the total energy need was supplied by renewable sources.

However, there are also critics of PV ever becoming mature (see for instance reference [6]). Main concerns are that PV electricity will never reach grid parity and that as soon as government subsidies stop the PV industry will disappear. Another concern is that the daily rhythm of solar electricity will prevent it from ever providing a substantial part in the overall electricity production.

 Copyright © 2008 John Schmitz

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[1]http://www.eetimes.eu/germany/206801636

[2]http://www.pv-tech.org/r_and_d/article/nrel_boosts_cigs_thin_film_solar_cell_efficiency_to_record_199_percent

[3]http://isic.epfl.ch

[4]Steve O’Rourke, Peter Kim, Hari Polavarapu, Solar Photovoltaics, July 2007, Deutsche Bank

[5]http://www.economist.com/business/displaystory.cfm?story_id=10961890

[6]http://www.semiconductor.net/blog/920000492/post/600024460.html

 

The Law of Conservation of Energy

Hermann von Helmholtz is a famous name in thermodynamics[1] although he also made famous inventions in the fields of ophthalmology, electrochemistry and acoustics. It was Helmholtz who formulated very clearly, using conclusions reached by Kelvin, Joule and Clausius earlier,  the existence of the law of conservation of energy or of “force” (as energy was called at that time) around 1850. In the winter of 1862, he delivered a series of lectures at Carlsruhe on the topic of the “Conservation of Force”. He started with an introduction in which he managed to elaborate on this theme without using any mathematical formula[2]. Below I will give a brief summary of the main points of this introduction (which can be found on numerous web sites[3]).

He starts of by showing that gravity, the most fundamental of all forces,  can be used to do work[4]. For instance a weight can drive a clock by sinking. Although the weight will have lost it capability to perform work when it reaches the floor, it will not loose its weight: gravity remains. The amount of work can then be determined by the weight times the distance travelled.

Heat can also produce work such as occurs in a steam engine. Here he recalls the point that heat must not be considered as a substance but merely as an movement of internal particles (realize that we are still about 50 years before atoms become widely accepted!). For quite a while it was considered that the amount of heat was constant (for instance, the required amount of heat required to melt a piece of ice is the same amount that one needs to extract when the resulting water is converted to ice again). However, he explains that as soon as heat is converted into work, that an equivalent amount of heat is destroyed. The relationship between heat and work was established by the work of Clausius and Joule. Many other examples exist where work is generated at the cost of something:

• a raised weight can do work but while doing that it must sink and no longer do work
• a stretched spring can do work but will become loose
• the velocity of a mass can do work but will eventually come to rest
• chemical forces (=energy) can do work but they will get exhausted
• electrical force can do work but will consume chemical or mechanical forces

Helmholtz concluded that all natural forces (energy) can do work but they are at the same time exhausted to the degree of work performed. He then formulated that the total quantity of all forces capable of doing work in the whole universe remains constant. He compared this with the laws of constant mass or constant chemical elements (both were of course to be found less constant after the theory of relativity and the discovery of radioactivity!!).

Finally he touches briefly on the topic of perpetual motion and states that force cannot be produced from nothing: something must be consumed. I strongly recommend reading Helmholtz’ introduction.

Copyright © 2008 John Schmitz

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[1] Hermann von Helmholtz (1821-188 reported on July 23 in 1847 on the principle of conservation of energy and showed that he had acquired a deep understanding of this principle. He was, together with Rudolf Clausius, the founder of what was called the Berlin School of Thermodynamics where he succeeded Magnus as the director of the Physical Institute. The influence of this school on the development of thermodynamics was crucial. It is almost unbelievable how many famous scientists were connected to this school. To name a few: Walter Nernst, Max Planck, Albert Einstein, Erwin Schrödinger and Leo Szilard.

[2] Although Helmholtz himself had a very good knowledge of mathematics

[3] See for instance: http://www.bartleby.com/30/125.html

[4] Work is simply defined here as lifting a weight.

 

Solar Photovoltaic Electricity to hit the Power Grid?

The generation of electricity from solar energy could not have been possible without the discovery of the photoelectric effect in 1839 by Becquerel (described by Einstein in his 1905 paper for which he later received the Nobel price). In 1954 the first silicon based solar cell was invented at Bell Labs and subsequently applied in the Vanguard I space satellite in 1958 where solar cells generated 1Watt of electrical power to drive the radios of the satellite. Since the Bell solar cell, that achieved 4% efficiency, the photovoltaic (PV) research focus has been on improving the efficiency of the conversion as well as lowering the costs of  the device. Recently Stephen O’Rourke, a research analyst from Deutsche Bank,[1] as well as others[2]have put statements forward such as in what year electricity generated by solar panels would achieve “grid parity”. Grid parity is reached when the cost price of PV generated electricity starts to compete with the local retail price of the centrally generated grid electricity. Of course this would be without any (government) incentives. Important economic parameters solar systems are:

• - cost per Watt at module level (depends very strongly on the technology used and on the efficiency)
• - cost per Watt at system level (depends on the cost at module level and the costs of the downstream equipment, can be as high as $7/Watt for a residential system)
• - cost per kWh produced (depends on the two line items above and in addition on the lifetime of the entire system, i.e. how many kWh will be cumulatively be produced)

Module refers to the actual solar panel and system refers to the solar panel plus all the downstream equipment needed, such as a DC-AC inverter. On average the retail price of grid electricity in the USA is about 0.09 $/kWh,  whereas the PV electricity cost price ran in 2006 at about 0.3 $/kWh. The question is now of course how the price of grid and PV electricity will change in the coming years. Grid electricity is expected to rise to about 0.20 $/kWh by 2020. O’Rourke and his team[3] developed  models to predict how the price of  PV electricity would come down in that same period.  In the figure below the results of that analysis are made clear.

         

(Figure reprinted with permission of Stephen O’Rourke, Deutsche Bank)

We see that over the period of 2006 till 2020 the grid electricity price will continue to increase, the price of fossil fuels will be an important driver for that trend. In that same period we see the price of PV electricity coming down. Important contributors to that trend are cheaper PV technologies, a better economy of scale and improved manufacturing methods. Depending on which scenario is followed we see that at around 2015 grid parity is reached. However, O’Rourke noted that even at grid parity (depends also strongly on in which part of the world you are because of the amount of sunlight received), PV electricity would merely be used as a peak power supplement and not so much as a base load supplement, but nevertheless it starts to looks attractive.

At this moment the global PV contribution to the total primary energy supply (TPES) is of the order of 0.1%, but is rapidly growing. The life cycle greenhouse gas emissions of PV electricity is 20 to 30 times less than fossil fuel fired power plants. Therefore, if PV electricity continues to increase at it current pace it will substantially contribute to a sustainable society in the years to come.

Two more important aspects need to be taken into account: will PV over its life cycle a) result in a net energy return versus energy invested and b) result in lower greenhouse gas emissions? The answers for both are positive, more about that in a future blog.

 Copyright © 2008  John Schmitz

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[1] Stephen O’Rourke, at the SEMI Industry Strategy Symposium, Jan 2008, California: www.semiconductor.net/article/CA6526670.html?nid=3664

[2]Paul Basore, Renewable Energy Group: There’s lots of silicon in photovoltaic cells, but is there any gold for the electronics industry? - Practical Chip Design - Blog on EDN - 1690000169

[3]Steve O’Rourke, Peter Kim, Hari Polavarapu, Solar Photovoltaics, July 2007, Deutsche Bank

 

World’s Greenhouse Emissions to Worsen in 2030 According to IEA’s 2007 World Energy Outlook Report

  The most recent energy outlook from the IEA is frightening[1]. If the world continues its current pace of growth of the economy, we will need 50% more energy in 2030 than today (for what is called a “Reference Scenario”). Since fossil fuels continue to play a dominant role in our economy, the level of CO2 emissions is expected to increase by at least 25% [2]. This will clearly put the world in an even more apocalyptic climate change scenario.

The main contributors to this increase are China and India. They account for 45% of the global increase. All developing countries together account for about 75% of the increase in energy demand. But it must be remarked that per capita the CO2 emissions of China in 2030 is still only 40% of that of the USA and India is even much less.[3] China and India’s energy demand will double from 2005 to 2030 [4].

The combined oil imports of China and India will increase by almost a factor of 4 from 2006 to 2030. China will already surpass the USA in 2010 as the world’s largest energy consumer. Not because that China is making no efforts to increase energy efficiency but it is simply not enough. Because China is a net producer of many goods, increasing its energy efficiency will have a direct impact on the world’s greenhouse balance. India’s energy reduction approaches are not well defined yet.

The IPPC’s scenario of about 2.5°C increase would call for a CO2 level not higher than 440 ppm. This implies that CO2 emission levels must fall somewhere between 50% to 80% of the 2000 levels by 2050. Obviously this will not come automatically and can only be accomplished when, at government level, swift and substantial actions are taken[5]. The main producers of CO2 are fossil power plants, therefore reduction of electricity demand is of prime importance here. In addition the IEA report also mentions nuclear power plants[6], renewable energy sources and clean coal technology[7] that can reduce CO2 emissions.

One recommendation found in the report is that the western nations must help China and India in order to develop sustainable energy power plants and to conduct research that will lead to less fossil fuel dependence for overall electricity generation.

 © Copyright 2008, John E.J. Schmitz

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[1]The distressing numbers in this blog come from the executive summary of the World Energy Outlook 2007 from the International Energy Agency.

[2] And this is of course where the real threat is. Even if we are able, by more efficient energy transformations, to lower the amount of kWh needed to generate a certain amount of GDP, the fact that the world’s GDP continues to increase will neutralizes the gain of better efficiencies. In other words, we must decrease the growth of the GDP such that it product of the growth in GDP times the gain in energy efficiency will decrease!

[3]It would have been better if the report had expressed the CO2 emission per capita and the GDP of these countries! See my blog on this topic of May 17, 2007: Energy “Consumption” and the GDP.

[4] And of course who are we that we can deny the people in these countries to improve their standard of living?

[5]This could be false hope, see my blog of May 5, 2007: Will Politicians Solve the Global Warming Problem?

[6]See my blog of June 17, 2007 (The Impact of Nuclear and Hydro based Electricity Generation on CO2 Emissions)  that talks about the fact that nuclear plants not always produce less CO2 per kWh if compared with a fossil fuel fired power plant

[7]Because coal remains, because of price and plenty of stocks, an attractive fuel, research has looked to methods to mitigate the environmental issues (such as SO2, Nox and CO2 emissions). One of these methods is CCS: carbon capture and storage.

 

The Origin and Development of the Energy Principle

Today everybody knows that energy can not be created or destroyed. We know this principle as the law of conservation of energy  (or the First Law of thermodynamics). Today we use this law in many situations perhaps without always realizing this. However, there was a time that there was great confusion about what energy, work and heat exactly was and their relation. It was the German physician Mayer who first formulated in 1842 a statement that can be considered as the predecessor of today’s energy law. At the occasion of the 100th anniversary of Mayer’s discovery, a small (91 pages) book was published in 1943 by Prof. Jacob Clay, a physics professor at the university of Amsterdam, entitled: “Onstaan en ontwikkeling van het Energie Beginsel”[1] (the book is in Dutch and the title can be translated by “Origin and Development of the Energy Principle”). The book contains some interesting historical elaborations of how the energy law developed. Because the book is not so easy to get anymore, I will summarize the chapter where Clay describes how Mayer got to his energy law.

Julius Robert Mayer, born in 1814 in Heilbronn (Germany, not too far from the French border) who, after several world voyages, became a medical doctor in 1841 also in Heilbronn. He was probably driven to understand energy issues by the question how chemical energy was transformed in living beings to do things like work[2] and generate heat. Mayer got convinced that perpetual engines did not exist (”…. das mechanische Arbeit sich nicht aus Nichts erzeugen lasse.” translated as “mechanical work can not be created from nothing”). Also, while studying processes where changes happened (such as the decrease of velocity of moving bodies and the simultaneous appearance of heat) Mayer was searching for something that would be constant. His inspiration for the existence of a  constant factor came from his colleagues in chemistry who used the law of conservation of mass (formulated in 1789 by Antoine Lavoisier) quite successfully. Mayer observed that “lebende Kraft” (literally “living force” but nowadays what we call  that kinetic energy) could be transformed into heat[3]. In addition he noted that the amount of heat needed to warm a given quantity of gas was larger at constant volume (no work from the PDV term!) than when heated at constant pressure. This led him to formulate the equivalence of work (or energy) and heat and he made a first estimate of this equivalency factor (which today is known at 1 calorie = 4.184 Joule).

The contributions by Mayer were for quite some years neglected by the scientific community. One reason was that he did not very clearly present his thoughts[4]. In addition he had competition  from an English beer brewer: John Prescot Joule who arrived  -somewhat later though- to similar conclusions but who was better connected to institutes such as the French Scientific Academy[5].

However, from 1862 onwards Mayer’s work became more and more acknowledged and he won several prestigious awards underlining the importance of his contributions. In 1847 Hermann von  Helmholtz published his famous article entitled: “Ueber die Erhaltung der Kraft” (”On the conservation of energy”) and this can be seen as an important milestone of the development of the First Law of thermodynamics. I will come back to that article soon.

Copyright © 2008  John Schmitz

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[1] Prof. Dr. J. Clay, Onstaan en ontwikkeling van het energy-beginsel; N.V. Servire, The Hague (1943)

[2] With work we mean here the ability of a system to lift weights.

[3] This fact was actually already noted in 1798 by Count Rumford who observed that a lot of heat was generated in boring cannon barrels.

[4] He confused force and work for instance. Therefore, Johann Poggendorf, who was the editor of the Annalen der Physik, refused to place his article in 1841.

[5] The Academy published a letter from Joule on the energy topic in 1847 in their Comptes Rendus.

 

Global Environment Outlook - GEO4

Recently the Global Environmental Outlook no 4 (GEO4) appeared, issued by the United Nations Environment Programme (UNEP). The report comes in two flavours: the full version of 164 pages and the “Summary for Decision Makers” (SDM), that counts only 32 pages and contains the main conclusions and recommendations. UNEP has published 3 earlier GEO assessments in 1997, 1999 and in 2002. Several other important reports that have been published in the past are:

Table 1 Other important environment documents

Report/Book	Year
Club van Rome: The limits to growth	1972
Our Common Future	1987
Entropy into the greenhouse world	1989
GEO-1 report	1997

The GEO4 assessment has been produced and sincerely scrutinized by government policy makers, funding partners, scientists and other parties and can be considered as an important piece of consensus.

Key message is that “there is evidence of unprecedented environmental change at global and regional levels” and “these unprecedented changes are due to human activities in an increasingly globalized, industrialized and interconnected world”. Many examples are given to underline the key messages such as:

• Availability of freshwater per capita is declining globally
• Ozone hole is the largest ever seen
• Poor people being the most vulnerable for environmental changes

The statement that the environmental change is due because of human action is important. Since, as pointed out by Al Gore, the fact that there is global warming is not so much disputed but that it is due to humans (and especially the developed world) is where the opponents of Gore disagree.

Then the report continues and expects the solution to come from “decision makers”: “decision-makers can promote timely action by integrating prevention, mitigation and adaptation efforts into the core of decision making”. I looked for a description of who the decision makers are but could not find one. I guess the report is referring to governments. There are many instruments that decision makers can use: property rights, market creation, fiscal measures, financial measures and liability systems. However, the total picture can be very complex as is illustrated by the GEO4 conceptual framework (see below).

GEO-4 Conceptual Framework

Copyright © 2007 John Schmitz

 

Understanding Entropy

Recently I got a few questions from Dr.  Wang who read my book. I believe that his questions are excellent and that the answers to his questions will help other readers of this blog site as well to understand entropy. I had some e-mail exchanges with Dr. Wang and I am happy that he agreed that I post parts of our conversation.

 Question: Is heat the ONLY energy form being of dispersion? In addition to heat, do we know one more energy form being of the ability to dispersion?

Answer: Heat, being fundamentally atomic or molecular in nature through vibrations, translations and rotations (remember the simple ideal gas result that 1/2 mv² = 3/2kT), is indeed a form of energy that is very abundant. Thus in many energy transformations it is difficult to prevent that some part of the energy is transformed in heat! Once heat is generated it is difficult to prevent that part of it leaks away into the environment.

The dispersion of energy refers to the tendency of energy to spread out in space. Indeed for heat this will happen because the atoms and molecules can propagate heat their movements to their neighbors: a bar of iron will conduct the heat from the hot end to the cold end till the temperature is even across the bar. Dispersion is not limited to heat only, for example electromagnetic radiation or magnetic fields will spread out as well.

Question: Is it possible to have entropy increase during the transformation of energies without the involvement of heat, for example, between two non-heat energies?

Answer: Yes, the best example I can come up with are fuel cells. In the cell you convert chemical energy directly in electrical while the entropy of the entire system will increase. But, and that is important, because no heat is directly involved the efficiency of a fuel cell in generating electricity can be much higher then conventional power plants.

Another example can be found in my book on page 173. There you can see how the expansion or mixing of a gas in an isolated system will lead indeed to a higher entropy. Thus the entropy of a system can increase without any change in energy of that system.

A related phenomenon in this respect is the Demon of Maxwell. I have spent a few words on that extremely unraveling thought experiment in the book as well.

Question: Is entropy more fundamental than energy?

Answer: This is a real interesting question, I never thought about that. I would say that energy represents a quantity that never changes and must be therefore quite fundamental. This is basically the First Law of thermodynamics. Entropy says something about the quality of that energy quantity. As long as entropy increases (or can increase) there are gradients (of energy of temperature or of species concentrations) present. As long as gradients are present, life is possible. Thus from that point of view entropy is perhaps the more fundamental one (at least from our planet’s viewpoint) because the presence of energy alone is not enough to enable life. Life needs energy gradients.

Question: Will the increase in entropy SURELY lead to the transformation efficiency less than 100%?

Answer: Here we need to be careful how we phrase this. Since energy is constant, transformations from one form to the others must be 100%. However, if our objective is to transform a given quantity of energy fully into another single form (for instance heat into work) then the increase in entropy will certainly limit the transformation efficiency as an amount TΔS will be no longer “available” to us as that amount has become more “diffuse”.

Question: How about the transformation among energies without the involvement of heat?

Answer: See my remark above for the fuel cells.

 Copyright © 2007  John Schmitz

 

The Use of Sound to Convert Heat in Electricity

Of all forms of energy that of electricity is perhaps the most utile. One reason is the ease of transportation through a relative simple and vast infrastructure (power grid). Burning fossil fuels generates a large portion of the world’s electrical power. Heat applied in the boilers of power plants is used to generate steam and the steam drives subsequently turbines and the actual generator. The whole of this approach is particular geared towards mass volume electricity production. A typical size of a power plant these days is 2000 MW.

However, there are situations where it is beneficial to work at a much smaller scale to convert heat in electricity. For instance, the cooling of powerful processor chips in a computer. The microprocessor can dissipate up to and sometimes even more than 100 Watts of heat. The idea is now to turn that waste heat into electricity for re-use. There are several ways that that can be done for example through the use of Peltier[1] elements. But here I would like to focus on a method that is researched at the university of Utah. Professor Orest Symko studies methods to convert (waste) heat into electricity through an intermediate step namely through the generation of …… sound.

For this to work there are needed two types of devices. The first one is called a thermo-acoustic device. This device transforms heat into sound. A simple version is a tube in which there is a kind of a sieve or metal screen that can be heated by a flame or other heat sources such as the microprocessor chip. By air expansion in contact with hot parts and contractions when air comes in contact with cold parts a sound is generated in the pipe in a similar fashion as it is done in a flute or an organ pipe. Quite intense sound levels of 120 dB[2] or more can be generated in relatively small devices (dimensions a few cm’s). Once sound (basically pressure variations) is generated, it can be converted by an piezo-electric device[3]  in electricity. The situation has some similarity with that of the heat engines in power plants described above,  where heat is converted into steam under pressure and then used to generate electricity.

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[1] A Peltier element is a device that upon current passage will cool at one location and heat at the other location.[2] Sound intensity of a rock and roll concert or a plane at 100 m distance.[3] A material that has piezo-electrical properties converts mechanical pressure variations in electrical energy.

 

Perpetual Engines

Since the 11^th century, many people have tried to beat the First Law with ingenious machines. There are good reasons for trying: if you could build a machine that could work forever without needing energy, that would solve the world’s energy problem in one stroke. You would gain immeasurable wealth, fame, and surely the Nobel Prize as well. Remember the tremendous excitement that emerged when Pons, et al. wrote about “cold fusion” in 1980? And that did not even involve perpetual energy production, but only a claim that nuclear fusion could proceed at room temperature instead of 5000^oC - the temperature on the surface of the sun!              

There are basically two different aims for perpetual devices: to achieve perpetual motion, and to generate work. A perpetual motion machine is typically not very useful other than its allure as a kind of magic show that can attract big crowds and so generate income from admission fees. In contrast, perpetual motion engines claim to generate work. (We call them perpetual motion engines because even perpetual motion requires that a certain amount of work be generated to overcome the friction forces, however small, that are present in all engines.) The hundreds of proposals made over the years for perpetual motion engines use many different forces to keep the movement going - including purely mechanical forces (gravity, expanding fluids, or springs) as well as magnetic, electrical, or buoyancy forces.

As said above, the First and Second Laws are postulates. This means no proof is possible, but it is merely based on many observations. Thus, in principle it could happen that tomorrow somebody builds an ingenious machine that can produce “free” energy. This would obviously be an enormous blow for the thermodynamic theory, but a blessing for humankind. Many such claims have been made, and many machines have been built either by people who intentionally produced frauds, or who were very serious about the matter and saw a mission to provide humanity with a useful tool. Also, many designs were made but never translated into real machines, and they are sometimes very difficult to prove wrong before they are actually built. Detailed mechanical analysis is often required before the flaw in the design can be found. The author knows no verified perpetual motion engine or machine has ever been built. Nevertheless, it’s fun to look at some of these concepts.

Before we do, though, it’s good to know that there are two kinds of perpetual motion engines, based on which of the two laws is being violated. Engines of the first kind typically claim that they can generate more energy (in the form of work) then the amount of energy that was put in, which clearly violates the principle of conservation of energy. Engines of the second kind are a bit trickier to describe. They try to convert heat into work without implementing any other change (achieving 100% efficiency), or purport to let heat flow from cold to warm, or attempt to convert heat into work without using two heat reservoirs at different temperatures. Simply put, second-kind perpetual motion engines draw energy from a heat reservoir and convert this heat into work without doing anything else.

Many perpetual motion engines of the first kind use the classic design of “overbalanced wheels.” An early example comes from the Indian mathematician and astronomer Bhaskara, whose design incorporates tubes filled with mercury. In the figure below, we see the operating principle of Bhaskara’s idea. He claimed that the wheel would continue to rotate with great power, because the mercury in the tubes is not at the same distance from the axis at opposite sides of the wheel. Bhaskara probably never built a real device, but similar ideas later were incorporated into the designs of other inventors’ engines, none of which ever worked. Fraudulent designs for perpetual-motion machines even made it to actual patents[1], which were later challenged in courtrooms. A famous example of a fraud was that made by Charles Redheffer in 1812 in Philadelphia. He claimed to have invented a work-generating perpetual motion engine, which seemed convincing until it was discovered that a man in an adjacent room was powering it.

Several famous names are connected to the idea of perpetual motion engines. Leonardo Da Vinci designed and built many devices and machines, including two devices to study the workings of perpetual motion. In his time, the principle of the conservation of energy was not known, but Leonardo had good insight into the working of machines and did not believe one could construct a perpetual engine. Simon Stevin, a Flemish scientist who lived from 1548 to 1620, actually showed that a purported perpetual engine based on a chain looped over a pair of asymmetric ramps would indeed not move without the addition of external energy.

An example of a perpetual motion engine of the second kind was provided by John Gamgee with his invention of the “Zeromotor” in 1880. His idea was to draw heat from the environment to let liquid ammonia boil; the ammonia vapor would expand and drive a piston. Afterward, the vapor was expected to cool down and condense, allowing the process to start again. Gamgee proposed this idea to the American Navy as an alternative to its coal-fueled steamships[2]. The problem, however, was that ammonia at atmospheric pressure condenses only at temperatures lower than -33^°C, and that temperature was not present in Gamgee’s system. Thus, we see here a violation of the Second Law: if you want to draw work from heat, you must have two different heat reservoirs, one at a high temperature, and the other at a low temperature. 

Perpetual engine after a design of Bhaskara.

© 2007 William Andrew Publishing. Reproduced with permission from the publisher William Andrew Publishing

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[1] Many patents can be found that claim to have invented a perpetual engine (for instance a patent for perpetual movement by Alexander Hirschberg in 1889, patent number GB 7421/1889). That these patents were granted was because in Great Britain patents filed before 1905 were not checked for whether the claims were realistic. This is unlike patents in the US where within a year a working prototype was required [van Dulken, 2000].[2] The American Navy was wrestling with the fact that their steamships were too limited in their routing because they could not get coal everywhere. Thus the Zeromotor was seen as a solution to this problem. The invention was even shown to President Garfield who was very positive about this approach.