LECTURE NO. 17
THE MAGIC OF MIRRORS
TEC II
Copyright © Harold Aspden, 1998
INTRODUCTION
Professors will tell you that "In nature heat
is never found to flow up a temperature gradient of its own accord". From this,
they and the textbooks on which they rely advance to the statement of a law
according to which it is impossible for any machine to abstract heat from the
coldest body of its surroundings and convert this into useful work, surplus to
that needed to power the machine. The law thus justified is known as "The Second
Law of Thermodynamics".
If you are a student of physics or engineering
you are thereby indoctrinated and become committed to the belief that if
someone, in your later life, whether in academia or in industry, comes to you
with a bright idea or proposition about designing a machine that does not keep
within the bounds of that particular law, then you are justified in giving vent
to your scorn and ridiculing that person for being ill-educated.
So it is
that our world, in which we are so anxious to catch a glimpse of a ray of hope
that we may one day inhabit a pollution-free environment, is left in darkness,
thanks to the 'good' education that we physicists and engineers have received in
our university years.
I am now too old to think that I can put right the
damage done by all those professors, but I can suggest that any student who
listens to such teaching in the future should pay close attention to the
argument used. Now read again the opening paragraphs above and ask yourself two
questions: "Where in nature does one ever see a 'machine', as such?", and: "What
is the point of building a machine, said to be a heat engine, if all it does is
to allow heat to flow 'of its own accord'?" Surely, the very fact that man has
intervened by providing a machine which deploys heat energy in some way, is an
intrusion upon that territory of something doing something of its own
accord!
Search the whole spectrum of physics and ask yourself whether you
see 'order' or chaos' in nature. Surely you can see both. There is 'order' in
the behaviour of electrons in atoms. There is order in the way atoms fit
together in a crystalline structure. There is order provided by the magnetic
domain structure inside ferromagnetic materials. All that order is governed by
energy finding its optimized state. Seemingly, however, there is disorder in the
energy activity we refer to as 'heat', and those professors of yours will
delight in introducing you to the mysterious word 'entropy'. They do not know
what 'entropy' means, other than saying it is the quantity of heat as divided by
its temperature and that it can only increase. That is because they have the
conviction that heat can only 'go downhill' and degrade in quality, meaning that
its temperature has to fall inexorably as the heat energy passes on into the
oblivion of outer space.
But suppose there is, in the system we call
'space', something that can be said to be a 'machine'. Then your professors will
smile at your suggestion and come back to that Second Law of Thermodynamics. The
heat can only go 'downhill' in temperature and entropy can only
increase!
It is here that I step in and refer to something of mine that
was published in the science journal 'Nature', 1990h
in these Web pages. In fact, I have already introduced this subject in the first
chapter TEC
I of the sequence of commentaries I am putting on the Web as my account of
'Thermodynamic Energy Conversion'. In this Lecture No. 17 I wish to delve into
some simple physics, rather than technological detail, just to ease the path for
those who are still under the spell of their professorial teachings.
The Magic of Mirrors
Imagine that a thin nylon cord supports
two metal spheres, each at a different focus of a concave mirror. Now ask
yourself whether the temperatures of those two metal spheres must be the
same?
To answer this question refresh your memory of what you may have
learnt in your physics lessons. I quote from a 1957 textbook on 'Geometrical
and Physical Optics' by R.S. Longhurst:
Suppose there is a source of light inside a sphere then ....
(by the analysis here presented .... the flux reflected from each part
of the sphere is equally distributed over the other part, or the flux received
by an element after reflection at other points is everywhere the same. For a
given sphere it can therefore only depend upon the total flux radiated by the
enclosed source.
In your lessons on heat radiation you also
learn about black body radiation and how uniformity of temperature prevails
within a spherical cavity so that inspection through a small aperture in the
cavity allows you to perceive the nature of that 'black body radiation'. Indeed
you are taught that the radiation is very similar to that of a perfect black
body at the same temperature as prevails within that spherical cavity. The
cavity, moreover, need not be of spherical form, given that equilibrium
conditions will prevail anyway and the result of all this is enshrined in what
is called The Law of Cavity Radiation.
So, when you come to
answer the above question your instincts should be to say that both metal
spheres must be at the same temperature.
Now consider the two metal
spheres as being at the focal points of an ellipsoidal mirror which constitutes
that radiation cavity, as depicted in Fig. 1.
FIG. 1
Here, if only by an argument based on symmetry, you
can assure yourself that the two metal spheres will tend to remain at the same
temperature. Now, however, ask yourself what happens if the sphere at A is
cooled by some internal means. Will it then merely absorb heat from the cavity
surface, whilst the metal sphere at B retains its equilibrium temperature as
that prevailing at the cavity surface?
The answer to this is known from
Pictet's experiment or that of Count Romford, which dates from 1800, as you may
see mentioned in the 'Background of the Invention' section of my U.S.
Patent No. 5,101,632. Metal sphere B will cool down to complement the
cooling of metal sphere A.
Now, although I say the answer is known from
such experiments, with regard to the details of such experiments, I only see
reference to the use of a concave mirror, so we need to look now at what is
shown in Figs. 2 and 3.
FIG. 2
FIG. 3
Here the mirror is not a complete ellipsoid but just
a concave portion of such a form. We have asymmetry in the apparatus and, yes,
we know from those experiments that, if one of A or B is at a temperature
different from the equilibrium temperature of the environmental surroundings, so
the other will adjust to a temperature that is also different from the ambient
temperature. However, what I now ask is whether, without any predetermination of
the temperature of A or B by some special heating or cooling means, A and B will
adopt the same temperature under normal conditions of equilibrium?
You
can answer this in two ways. You can declare that according to the Second Law of
Thermodynamics the temperatures of A and B must be the same, owing to it being
contrary to experience for 'heat to flow from a cooler body to a warmer body of
its own accord'. It must do that if A and B are to adopt different temperatures,
given that heat energy is conserved. Alternatively you could say that you do not
know the answer to the question but that you surmise that, since in Fig. 2 the
portion of the cavity housing surface radiating heat to sphere B is larger than
that in Fig. 1 radiating heat to sphere A, it seems likely that B will get
hotter than A. You can further argue that if the two spheres have the same size,
then more heat will be radiated from A to B than is radiated from B to A. So B
should become hotter than A.
You do this by discussing the role of the
mirror in capturing radiation from B over a small solid angle of radiation, and
reflecting it to A, whereas, as is evident from Fig. 3, the mirror captures a
large solid angle of radiation from A and reflects it to B. Inevitably you
should be in a quandary as to whether you can trust that Second Law of
Thermodynamics or whether, in fact, if you build such a device and eliminate air
convection you will actually witness A and B developing a temperature
difference.
Think about it! Ask yourself what this means. I know myself
that, if I can get heat to flow through a thermoelectric device from one metal
heat sink to another, then I can generate electricity. However, if I can
generate electricity by merely building a thermoelectric device combined with a
mirror and without doing anything to feed in any other form of energy, then I
have either worked a miracle, performed a feat of magic or, perhaps, found an
alternative to imitating one of Mother Nature's more subtle energy regenerative
processes.
This process does not in any way breach the First Law of
Thermodynamics, namely the need to conserve energy, because all it does is to
take heat energy from our ambient surroundings and convert it into electricity.
Now, and I say this with emphasis, why do we persist in trying to solve our
future energy problems by attempting to replicate the imaginary hot fusion
processes occurring in the Sun when here we can see a possible way forward using
the simple 'magic of mirrors'?
In fact, all this amounts to is the
harnessing of Maxwell's Demon, except we do let the mirror perform the task
effortlessly. We do not need a demon sitting at the toll gates where passage of
heat energy is allowed or not allowed, according a selection of the particles
that convey heat. Maxwell's hypothetical demon opens and shuts a gate, to admit
and confine the more energetic particles in one heat chamber, whilst obstructing
entry of the least energetic particles and allowing egress from the chamber by
the least energetic particles. By the simple labour of opening and shutting a
gate, heat is thereby transferred to that chamber to elevate its temperature.
However, we use mirrors instead. Energy seeking entry to that chamber is direct
to a mirror focus located at the point of entry through a small aperture,
whereas energy coming the other way from within the chamber has to find its own
way through the small aperture leading through that passage and so has some
difficulty escaping, at least until its temperature raises sufficiently to give
it the necessary impetus.
Practical Considerations
This sounds interesting, doesn't it,
but is it practical? Well it helps if the source of radiation is not simply a
black body surface at room temperature, but rather one at an elevated
temperature. The practical aspect could well just be one of scale and a
consideration of economic factors, weight and volume to power ratio as well as
capital cost to power ratio.
If you think we might never be able to power
an automobile by such a method then I will not argue with you on that point.
After all, one hundred years ago there were those who could never see technology
developing that could power the flight of a Boeing 747. Nor could they imagine
the technology that we now see in the fabrication of electronics microstructure
in the computer industry. All I can say is that my calculations, as summarized
towards the end of that U.S.
Patent No. 5,101,632 indicate the prospect of generating 15 kW in a
structure the size of a cubic metre. One can, presumably, contemplate the
development of automobiles using this new technology, given one hundred years of
onward development!
In such research so much does depends upon how we
convert that heat at the elevated temperature into useful work, as by generating
electricity. However, I have allowed for that in those calculations and
suggested a way forward. There is the question of whether our mirror engine is
subject to the Carnot efficiency. In fact, it cannot depend upon the Carnot
criteria, because we are not losing any energy. We have no exhaust gases that
carry away the degraded heat from which our engine has extracted its power.
However, if we use a conventional heat engine, such as a steam engine or hot air
engine to convert the heat our mirrors have produced at an elevated temperature
then, sadly, we suffer from the Carnot efficiency limitation. What is also sad
about this is the fact that we could well be considering using a reverse heat
engine to increase the temperature of ambient heat intake as a kind of pre-heat
stage in our engine. That offers the advantages of the Carnot criteria as a gain
factor of the heat pump process. If only we can convert heat into electricity
with an efficiency well in esxcess of the Carnot efficiency, then we can work
the necessary miracle!
The Magic of Magnetism
Physicists will smile at the above
suggestion, thinking, as they do, in terms of photons and such like. They
believe that the energy carried by radiation of light and heat is transported by
those so-called 'photons' which travel at the speed of light. Photons, if they
exist as something that really does travel at that high speed, really can give
physicists reason for having a headache, if they avoid being blinded by
mathematical symbols and try to make sense of this photon notion. There is, for
example, something called the 'Langevin Paradox'. According to one expert on
Einstein's Theory of Relativity, writing as recently as in the September 15
issue of Physics Letters, vol. 234A (1997) pp. 75-85, to get Einstein's
theory to be consistent with photons as carriers of light energy, one needs to
say that the photon has a finite mass. Now, Einstein's theory is sacrosanct, not
to the engineer, but to the physicist, so the world of physics must be losing
its grip on reality. Can we afford to wait until physicists put their house in
order?
We all know that a particle travelling at the speed of light will
acquire infinite mass, at least that is consistent with experiments on
electrically charged particles that can be accelerated to speeds close to that
of light. That was all known before Einstein tried to build on the fact as
support for his theory. However, there is another fact that needs to be
remembered, the fact that the Earth's rotation can be sensed by optical
interference techniques using a rotating system of mirrors (The Sagnac Effect).
This fact known for most of the 20th century, still has to be reconciled with
Einstein's theory or the idea of photons as particles or both have to be
rejected. Take note also that there is evidence that the west-east motion of our
laboratories on body Earth can be sensed owing to the fact that it intrudes to
upset the precision of measurements of the Michelson-Morley type. The latter is
the famous experiment which disproved the notion that the aether had certain
properties previously assumed. It did not disprove anything about the ability of
the aether to store energy, it being a universal energy 'bank' in which we can
deposit energy by magnetic induction and recover that energy on
demand!
Surely therefore we need to reconsider the foundations on which
physicists rely when they express opinions on fundamental energy issues. Mirrors
can reflect light, meaning energy if light transports energy at the speed of
light, but it may well be that all that is transported is the ripple we
associate with an electromagnetic wave, a ripple of the sea of energy that is
everywhere in space. Now, I can deflect a moving electron by using a magnetic
field, without injecting energy into the magnet producing that field. I cannot
deflect an electromagnetic wave by using a magnet, at least not sufficiently for
it to have any practical consequence. I decline to comment on whether a magnet
can affect the motion of a photon, for the simple reason that I can only see the
'photon' as an 'event' that marks an energy-cum-momentum transaction as between
aether and matter and events can occur at points A and B without requiring all
the energy involved in those transactions to make the journey between A and B at
the speed of light.
Our Thermodynamic Energy Conversion project (TEC)
involves us, not with photons, but with energy and temperature and our next task
is to examine the physics of converting heat energy into electricity. We are
aiming at something close to 100% conversion efficiency, with no Carnot factor
to bother us. We cannot talk about photons, because photons do not have a
'temperature', even though they are deemed to represent a package of energy
relating energy with Planck's constant, h, times the frequency assigned to the
photon.
The Electron and Maxwell's Demon
Imagine that Maxwell demon
sitting patiently at a point inside a block of metal. You are sitting outside.
You connect that metal in an electrical circuit and you pass current through it.
The demon sees electrons migrating past his viewing station as the current flow.
Now we do not want our demon to exert himself by opening and closing a gate or
shutter, so we have provided a magnet for him to sit upon. The magnet produces a
field which acts on the electron and, as we all know from our basic physics
education that electron will be deflected sideways. See Fig. 4.
FIG. 4We can now, if we wish draw current from that metal at
right angles to its normal flow path. The stronger the magnet and the greater
the magnetic field H, the greater the EMF generated in the lateral direction,
the electric field E being proportional to H and also to the velocity v of the
electron e.
This process is known in physics as the Hall Effect. There is
no conversion of heat into electricity. The energy you supply in getting the
electrons to migrate at that velocity v is all deployed in developing that
electric field E and powering the current we might draw from the resulting EMF.
The magnet does no work. It merely sits there and forces those electrons to
change direction. The Hall Effect and the Carnot criteria of thermodynamic
engines have no ground in common so beware of becoming confused as we now extend
our Fig. 4 deliberations into the realm of heat energy conversion.
We are
only interested in heat and we want to equip our Maxwell demon with a whole
assembly of magnets positioned along that electron flow path, having now in mind
the fact that the flow of heat in metal is a flow of electrons! Our demon knows
only one temperature, that where he sits, and he pays no attention to what
physicists living outside that lump of metal might have to say about Carnot
efficiency. That is something that depends upon the specific absolute values of
two temperatures, whereas our demon knows that all that matters to him is the
flow of heat energy carried past his viewing station and that merely depends
upon a temperature gradient at his position.
So those electrons migrating
past him as heat are, as before, deflected to set up that transverse electric
field, but this time their energy is that of heat and the magnet puts order into
things and takes energy from that heat to feed it into the orderly state of an
electric field. In short, we have quite efficient conversion of heat into
electricity, because what is not converted moves on to be processed by the
demon's assistants further down the line, namely those other magnets.
If
we take electricity as output in that lateral direction, so we have cooled the
metal. That is what we require in our mirror engine system. Two metal heat sinks
at different temperatures T and T' powered by mirror magic and linked by a metal
path including our Maxwell demon, or rather his magnets. Let us just picture the
flow path of electrons that make the lateral detour. This is illustrated in Fig.
5.
FIG. 5When an electron flowing along the metal path is diverted
laterally to flow around an external loop circuit which includes a load device
(not shown) it returns on the opposite side of the metal to share the heat
latent in the metal at that point of return and moves on in the forward
direction conveying heat.
The electron does not need any extra power to
re-enter the main path of the metal conductor. Indeed, what has been described
is simply the conversion of heat into electricity, an energy conservation
process, but one which, thanks to the magnet and the established flow direction
of the heat, converts thermal chaos into electrical order. You may ask whether
this can really work. More to the point, you may ask what happens to the
electrons that reach the end of the main path and what is the source of those
that come from the beginning of the main path. Now, there is a mystery! Frankly,
I have yet to see this explained in a textbook and I wonder how I have missed
it. My textbooks tell me how electrons carry the heat flow but they do not say
quite how. One is left to wonder if it is a kind of 'knock-on' effect, owing to
collisions between faster-moving electrons coming from the left and slower
moving electrons coming from the right. In that case, since at any instant the
flow rate of electrons to the left must equal the flow rate to the right, given
no external closure circuit between the ends as heat sinks, there can be no net
field E generated at all!
So one can say that heat is still carried by
electrons in their 'knock-on' effects, thanks to a component of motion laterally
directed with respect to the magnetic field, but that would mean no overall heat
energy-to-electricity conversion. So, is the phenomenon described real? Well it
is, because it is known as the Nernst Effect and those EMFs induced by heat
flow, given the presence of a mutually orthogonal magnetic field, have been
measured. They are particularly high in nickel. It follows, therefore, that our
standard assumptions concerning the interaction of a magnetic field and an
electron in motion must be erroneous.
Now, I have long suspected this,
because I have wondered why it is that the magnetic field of a permanent magnet
can penetrate through a block of copper without the numerous free electrons in
motion within that copper reacting to screen such fields virtually in their
entirety. My answer, one I adopted long ago, is the following:
When an electron in motion reacts to a magnetic field it is a
quantum event, meaning that maybe it will and maybe it won't, this being
determined by whichever affords the optimum response from an energy
equilibrium viewpoint.
To picture what I mean here, note that an
applied magnetic field is an 'action' and the response of the electron in that
field is a 'reaction'. If the magnetic field increases then there is more
reaction opposing that field, but the reaction must allow the field to assume
the level at which it has stored the maximum amount of energy density in the
reacting electrons. Remember that kinetic energy absorbs potential energy and,
as potential energy minimizes, so kinetic energy increases. The energy density
in a magnetic field H is proportional to H2. So, if we are to store
such energy density in a system of reacting charge in motion, then we are
referring to the component of motion that acts to set up the opposing field. The
energy transferred to those charges, whether electrons or not, is a kind of
thermal energy and it is pooled with the thermal state of the absorbing medium.
It is dispersed as a result, apart from just that amount of energy that is
polarized by the need to sustain the field reaction.
When I worked all
this out, back in the mid 1950s, I discovered that what all this meant was that
the magnetic field set up by an electron in orbital motion is really double the
strength we have assigned to it in our standard electrical theory, but the
optimum field reaction of the charge that retains that energy in readiness for
its return when the electron's motion ceases will always set up a back-field
halving that primary action. It all made good sense and it explained what is
known as the gyromagnetic ratio, the anomalous factor-of-two observed, in the
ratio of magnetic moment to angular momentum, when the magnetic polarization of
pivotally-mounted ferromagnetic rods is reversed.
So what I am really
saying here is that the Nernst Effect is evidence of the selective or quantized
reaction of electrons when subject to a magnetic field. The Lorentz force law,
which says how an electron or other charge in motion will react in a magnetic
field, is not of universal applicability where the kinetic energy possessed by
the reacting charges is so great as to exceed the magnetic energy density of the
field in which they are present. There is also, it seems, a kind of pecking
order, as between charges of different mass and even between charges of similar
mass, such as electrons, if some have more energy than others.
Now I do
not want to dwell on this theme here, especially as it is further complicated by
that EMF produced by Nernst Effect having a different polarity coefficient for
some metals versus others. So, I will hide behind the facts of experiment and
say that the Nernst Effect is a real phenomenon, which is described in some of
the better physics textbooks. I will go further than this, as we develop these
'TEC' web pages and will describe two different technological consequences,
giving technical details of performance of the resulting heat to electricity
conversion.
My concluding message here is that, if you are a physicist or
student of physics and you are satisfied with what you have come to know about
quantum electrodynamics and the application of the Lorentz force, sufficiently
for you to think you can rely on that knowledge when judging the new energy
proposals that I am introducing in these Web pages, then you will surely be
missing opportunities for making a useful contribution to the energy technology
of the future.
Otherwise, if you wish to learn more, then I invite you to
progress to the next item TEC
III.
Harold Aspden