Improvements in or relating to Thermo-electric Generators.
Year: 1895

page_text: Date of Application, 12th Dec., 1895-Accepted, 23rd May, 1896
COMPLETE SPECIFICATION.
Improvements in or relating to Thermo-electric Generators.
A cominunication from ALFRED WUNDERLICH, Engineer, of 35 Rue Henri Maus,
Brussels, in the Kingdom of Belgium.
I, ALFRED JULIUS BOULT, of 323 High Holborn, in the County of Middlesex
Chartered Patent Agent, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :—
The process and apparatus forming the subject of the present invention have for
their object the realization on a commercial scale of the theoretical data and
conditions for the direct transformation of heat into electricity by means of a
thermo-electric pile; where a body with large surfaces aud which is a bad conductor
of heat is heated on one of its surfaces, and cooled immediately on the other in
order to obtain maximum efficiency of electricity.
In order to get inaximum efficiency of electricity it is important to re luce the
internal resistance of the transformation system (that is to say of the thermo-electric
pile) to a minimum, therefore the problein is to reduce to a minimum for the same
bodies, the distance between the heated and cooled surfaces.
The solution of this problem has been arrived at by combining a thermo-
electric pile with a steam boiler with cooling water hereinafter referred to as a
"thermo-boiler."
In this thermo-boiler, the gases from the fire box traverse heating tubes which
form "thermo furnaces," the outer cylindrical surfaces of which are closely
surrounded by refrigerating tubes, concentric to the former (see Figs. 5, 6, and 7
of the accompanying drawings).
The principles of the invention consist on the one hand in the reduction to a
minimum of the electrical resistance of the thermo-pile in order to get the highest
efficiency, and on the other hand in the recovery of such heat as comes out at the
cold junctions of the pipes by means of a supply of air, which carries it back to
the firebox.
By means of a given source of heat uniform heating of a metallic surface a a of
some heat-conductor can be obtained in a unit of time. See Fig. 8.
Let a a represent a cross section of a thin plate of high conductivity, bb a section
of a thicker plate made of some material of feeble conductivity and c c a section of
a thin plate identical with a a.
Let the arrows a¹ a¹ (full lines) indicate the rays of a source of heat, the
arrows cc (dotted) the rays of a source of cold.
It is proved that the quantity of heat which is transformed into electricity during
the transmission from the plate a to the plate c is in proportion to the difference in
temperature of a and c, but the intensity of the electric current, resulting from this
transformation is in inverse ratio to the thickness of the plate b. So it has been
found that in both Figures 8 and 9, with equal conditions the quantity of electrical
energy remains the same in proportion to the heat employed, although in Fig. 9 the
thickness of the plate bis double that in Fig. 8, but on the contrary the intensity of
the current is diminished by half, in inverse ratio to the double increase of the
electrical resistance.
It has moreover been found that the production of the electrical energy remains
the same when the plates a, b and c are divided into parts by sections normal to
their surface, and insulated from each other by intermediate layers.

page_text: The total result remains the same, when the effects of the separate parts are
added together, by connecting the hot joint of one section to the cold joint of the
following.
The transformation of heat is not affected, if the plates a b c (supposed to be
planes in Figures 8 and 9 are rolled into the form of a cylinder (see Figs. 11
and 12).
In order to connect electrically different parts or sections of a cylinder, formed as
in Figs. 11 and 12 so as to serve as a thermo-pile, that is to say, in order to fulfil
for a commercial apparatus the conditions of transmission of heat and cold, which
conditions were supposed to be existing in the diagrammatic Figures 8 and 10, the
apparatus illustrated in Figs. 1 to 7 is employed.
Figs. 1 and 2 represent a section of a thermo-electric element, formed by an inner
ring m and outer ring m³ of a good conductor of heat, as for instance, copper-and
by a ring m of some material which is a bad conductor of heat, for instance-iron
or German silver. In order to form a communication by means of a conductor m¹
from the hot inner ring m¹ of one element, to the outer cold ring m² of the next
element, the rings m³ and m³ of each element are cut out on one side and the end
of the conductor m is placed in a recess m made on the outer side of the
ring m³, so that when the different discs of the element are put together, that is
to say, when they are put one on the other and between them are introduced
insulating layers F, there will be neither recess nor projection, on the outer circum-
ference of the cylinder, which after putting the elements together might lead to the
formation, between the outer ring m³ and the refrigerating jacket of the tubes of
layers of air, which is a bad conductor of radiating heat.
The different discs forming a "thermo-element," are placed one over the other so
that a disc having a recess on the left hand side (as in Fig. 1) for the passage of
the conductor m' alternates with a disc having that recess on the right hand side,
as shown in Fig. 2.
Fig. 3 shows the way in which the discs are fitted together; the parts which are
shown here as not connected, are then brazed together.
Fig. 4 gives a longitudinal section through a refrigerating tube L, giving the
thermo-element in elevation.
The cylindrical surface of the outer rings m³ is placed against the inner glazed
surface L'of the refrigerating tube L made of iron or steel.
The thermo-elements, fitted together in this way are introduced in the refrigerating
tubes L, traversing the boiler from one end to another, and the outer wall of which,
made of sheet iron, is surrounded on all sides by water in the boiler, whereas the
inner wall is glazed and forms an insulator.
Fig. 5 shows a cross section of a vertical boiler.
Fig. 6 shows a horizontal section of the same boiler.
Fig. 7 shows in vertical section a similar arrangement of thermo-elements in a
horizontal boiler.
In all these three figures only one thermo-element is shown; but it is clear that
the arrangement is the same in the other tubes.
In the vertical boiler the steam is collected by several separate tubes R,
in order to get at the top of the water chamber a free space for introducing and
removing the thermo-elements for the purposes of fitting up and detaching. In
the horizontal boiler it is unnecessary to provide this space. The heating gases S
pass from the fire box through the heating tubes E and escape through the
chimney E (Fig. 5).
It must be mentioned that the thermo-elements are fitted in one column by means
of insulated bolts G passing through them, which facilitates their introduction into
the tubes L, as well as their removal.
These bolts G are insulated from the thermo-elements.
In Figs. 1 to 94 of the accompanying drawings are represented arrangements for
utilising the heat of the combustion gases and of the steam of the boiler for heating
the air supplied to the firebox in case of the use of solid fuel, as coal, coke, etc. but the

page_text: same principles apply also to liquid or gaseous fuel, as for instance, gas, petroleum,
benzine, alcohol or the like.
Figs. 1 to 6 show a vertical boiler and Figs. 7 to 9 show the application of the
same arrangements to a horizontal boiler.
Fig. 1 represents a vertical section through the axis of the firebox and of the
smoke box.
Fig. 2 is a horizontal section on the line of Fig. 14.
Fig. 3 is a horizontal section on the line X" X" of Fig. 1.
Fig. 4 is a horizontal section on the line X X Fig. 1ª.
Fig. 5 is a horizontal section on the line XI XIV of Fig. 1^.
Fig. 64 is a horizontal section on the line X XV of Fig. 1^.
The hot gases produced by combustion in the furnace rise to the openings N, enter
the pipes S, pass through the refractory tubes E inside the thermo-elements, rise in
the tubes E serving as chimneys and arrive in the smoke box Q and escape by the
common chimney Q'.
The heat, which passed from the hot junctions to the cold junctions, that is to say
from the walls of the refractory tubes E and through the body of the columus of
thermo-electric plates A, arrives at the wall of the tubes Land is absorbed by the
cooling water of the boiler.
The air supplied to the firebox comes in from underneath in an annular space H,
formed by a jacket, surrounding the thermo-apparatus, gets the radiating heat of the
brickwork of the fire-box, rises to H', absorbs the radiating heat of the cylindrical
wall of the boiler, enters the chamber H2, placed on the top of the boiler and is
heated by the contact with the chimneys E' and with the steam-pipes R.
The air is heated in that chamber in a uniform manner and led down into the
firebox by means of a forced draught, it descends first through the pipes H³, of
which there are a certain number in the boiler, passing through it vertically like
the tubes L, from these the air passes round the tubes S in the space H', is drawn
into the annular space H³, from which it enters into the canals He under the furnace.
The drawing-in of the air under the furnace is effected by means of jets of steam
coming out for that purpose through the holes W of a pipe T' which is arranged in
a circle round the ashpit.
The water, heated by the tubes L, is transformed into steam, which rises in pipes R
of which there are a certain number; these pipes lead into the smoke-box Q, where
they are connected by a circular pipe R' which is connected by two branches with
the central pipe R³, which ends in the chimney and lets out the jet of steam
producing the draught.
From the pipe R¹ a branch pipe T leads steam to the pipe T' under the
furnace.
The heights of the boiler and of the chamber for heating the air supply, which
chamber is between the smoke-box and the boiler, are arranged so as to allow for
conveniently removing the thermo-elements out of the tubes L.
In the drawings all the other parts and accessories for the working and control of
the boiler are omitted, as well as the firing apparatus, as they do not offer any special
features.
The horizontal boiler shown in Fig. 7 consists of three distinct parts, which can
be fitted or detached separately; namely the firebox, the boiler, and the smoke-box,
or the collecting box for the escaping gases.
The hot gases, produced on the furnace rise as in the previous arrangement,
pass through N, S, E, S', and escape into the smoke-box Q and from there enter
the common chimney Q
In order to draw the air supply a different arrangement of the thermo-electric
elements from that in the vertical boiler has here been employed. A free annular
space M is provided in each cooling tube between the wall of this tube and the
circumference of the thermo-electric elements.
The air is drawn at the back end of the boiler from two sides into the space P,
enters through U into each of the annular spaces M, comes out of them through U¹;

page_text: collected in the space H, descends, passes through H' and from there enters the
ashpit and passes through the furnace.
In this case the doors hg and d' are shut. The steam generated in the
boiler is taken at one side on the left (see Fig. 7) through a pipe R, which pipe
enters the smoke box Q, descends there in the centre (see Fig. 9A) is divided
at the bottom into two branches R' and rises at the sides by those two branches
entering the chimney and forming the steam jets forcing the draught in the common
chimney.
At the other side on the right hand, the steam is taken by a pipe T (see Fig. 7)
which descends in two branches to the space H, enters through H' under the furnace
and ends in a pipe W (see Fig. 84) provided with numerous small holes in order to
let in fine jets of steam under the furnace, producing thereby energetical combustion
of fuel and complete oxidation of smoke.
In the Figs. 1 to 14B are shown modified forms of arrangements described above
but founded on the same principles.
Figs. 1 to 4 show an arrangement of thermo-boiler in which the columns
of thermo-electric elements are placed directly in the chambers for water and
steam.
For that purpose the discs of the elements A. (see Figs. 3º and 4B) have projecting
cooling ribs at the end of which is the contact for cold junctions.
Fig. 1 shows a front elevation of such a boiler, which can have a great number
of heating tubes E; Fig. 2B shows a longitudinal vertical section, showing the
plates in elevation. Fig. 4B shows a plate element A in front elevation with a cross
section of the heating tube E, and Fig. 3 shows a vertical section through the
axis of the tube E showing the way the elements A are fitted together round oue
of the tubes E.
The plates A. are continued downwards to form prismatic ribs, and their
thickness is a little reduced in order to get free spaces between where the cooling
water may circulate.
These plates can be made of metal, of some alloy or of some other substance; in
the following description, iron is employed by way of example. In the cylindrical
opening of each of the plates is screwed or pressel in a contact ring B of red
copper, or of another metal, which is a good conductor, which ring is slightly
conical, then the remaining circular junctions at both front sides are soldered or
flattened with an iron.
From this contact ring B goes a metallic conductor in the shape of a wire or
strip C to the lower extremity of the next plate A, to which is soldered in front a
flat ribbon of copper D in such a way that all the section of the iron plate A is
carried to the hot pole. Into the hollow space, formed by the contact rings B, is
then introduced an interchangeable tube E made of refractory material, whereby
the copper rings are protected against direct attack by the heating gases. The
piles fitted in this way are supported by insulating bars J and are arranged side by
side.
Each thermo-pile has on the right side a heating pipe S (see Fig. 2B) for the
admission of the heating gases, and on the other side an exhaust pipe Q, which
pipes are insulated from the iron parts of the pile.
In the drawing the boiler is represented surrounded up to a certain height by
brickwork; instead of this, as indicated for the upper part, formed an empty
space could be arranged round the wall of the boiler, by means of a jacket N.
This empty space N serves for recovering the radiating heat of the surface of
the body of the pile, by heating the air before it reaches the smoke box.
The air passes, as indicated by arrows in Fig. 2B from left to right, passes through
the holes U and enters into the tube conveying the heating gases.
The cooling water washes round the whole surface of the thin ribs A which go
downwards from the pole and enter water in the boiler to a suitable depth O,
whereas in the upper part K steam collects, which according to the system of
heating can be used for blowing in the chimneys or exhaust pipes Q by means of

page_text: 11 TO 10comotives Of Can De red back to the me Qox at the entrance
of heating gases.
In the event of petroleum (or vapours of gazoline, alcohol etc.) being employed.
as fuel, the steam is allowed to blow into the flame of petroleum and in this way
get a long and economical flame.
In Fig. 5B the column of thermo-electric elements is placed, as in Fig. 5 in a
cooling tube with a glazed inner wall L' and traversed by a central tube L',
forming the heating canal E in which enter the gases from the fire-box or from a
gas burner S.
This tube L is surrounded by two concentric tubes L' and Lo, forming jackets
and leaving between them free spaces H¹ and H³.
The cooling of the outside of L' is effected by means of some system of water
sprays, for instance, a circular pipe D' from which the water comes out through
fine holes and is thrown against the walls of the tube L'.
The air comes in at the bottom of the annular space H goes up in the cylindrical
aunular space H₁, returns by the top, meets the descending water jets from the
sprayer D¹, gets mixed with the steam, descends in the space H³, gets heated
through contact with the wall L³, passes down through the holes H³, enters in the
channels H and goes up in the tube E in order to feed the heating flame of the
central interior canal E of the column of thermo-elements A.
Fig. 6B or 14 show a modified form of making discs or washers for thermo-electric
elements which form a column, being placed in the cooling tube. Fig. 6B shows an
oval section instead of a round one for the disc forming the thermo-electric
element.
The contact is produced without soldering by simple superposition of discs one
on the other, with the interruption of insulating washers, cut out in a suitable
manner as will be explained for the modified form shown in Figs. 7B to 14.
In the Figs. 6" to 14B the letters of reference indicate the following parts;
m the inner ring of the hot junction, m³ the bad conducting material, m³ the outer
ring of the cold junction' m' the conductor going from m¹ to m³ which makes
contact between each element and the ring m³ of the next element, and that at the
special place, me marked by a recess, notch or the like.
The place of the contact m of an element projects outside as much as the
corresponding place of contact of the next element is recessed out, so that by
superposition and compression of the elements in the direction of the axis of the
column the contacts become perfect, and in consequence of the expansion of
the metals produced by the increase of temperature the contact becomes still
better.
In Fig. 7B is shown a plan of a washer of a thermo-electric element, Fig. 8B
shows it in side elevation, Figs. 9 and 10 show the same views of the insulating
washer F, which is placed in a given position on the thermo-electric washer shown
in Fig. 7B so that of the latter only the two places of contact m which are
projecting are seen. Then a similar washer of an element is placed in the position
shown in Figs. 11 and 12B so that the recesses me of the upper washer comes on
the projections m' of the lower washer and that all the other points are insulated
from each other. Then an insulating washer F is again placed and in the position
shown in Figs. 13 and 14B and so on till a column of the desired number of
elements is formed.
Of course the thicknesses, the dimensions and the shapes of the washers or
discs of thermo-electric elements can vary according to the necessities and
according to the conditions of the system of heating.
The arrangements used allow every choice and every combination of metals,
alloys of metals or any compositions or substances suitable for production of a
thermo-electric current by heating and cooling.
In all the preceding arrangements the combustion air or air for feeding the fire
box is used also as a vehicle for bringing back to the fire box quantities of heat

page_text: emanating by radiations as a loss from the outer circumference of the thermo-
elements and from the chimneys. These quantities of heat are then used to
participate again in the transmission of heat through the hot and cold junctions,
instead of allowing them to escape, as was usual before, as pure loss into the
atmosphere after having accomplished the passage from the hot to the cold
junctions.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent, and in what manner the
same is to be performed, I declare that what I claim is :-
1. The construction of thermo-electric piles or batteries with recovering of heat,
by using cylindrical columns composed of washers with a hole in the centre
superposed one on the other with insulating layers interposed, each washer forming
a thermo electric element, the hot junction of which is formed by a cylindrical wall
of the outline of the central hole whereas the cold junction is formed by the
cylindrical wall of the external outline of the disc and where a conductor of the
current, coming from a piece with the mass constituting the hot junction (of a
material which is a good conductor of heat) starts from one of the points of the
circumference of the central hole of a disc in order to pass, insulated from the
mass confined between the two junctions of the disc formed of a bad heat
conducting material to the external outline of the same disc and to be connected
by a metallic contact with one of the points of the mass (of a material which is a
good conductor of heat) of which is composed the outer cylindrical outline of the
next disc substantially as described.
2. In combination with arrangements such as set forth in Claim 1 the use of
columns and discs of any outline and with a central hole of any outline.
3. In combination with arrangements such as set forth in Claims 1 and 2
the form of discs or thermoelectric elements substantially as described and
illustrated in the accompanying drawing with reference to Figures 1 to 4 and
6B to 14B.
4. The construction of thermoelectric piles or batteries with recovering of heat
by employing arrangements such as set forth in the Claims 1 to 3 where a series
of discs-elements form by superposition a column, the outline of which comprises
all the cold junctions and the inner outline all the hot junctious: the arrangement
of each of those columns in a tube of suitable metal, which tubes cross a chamber
for water or steam of a boiler in such a way, that all the heat, emanating from the
outer surface of the column, that is to say from the surface of the cold junctions, is
transmitted directly or indirectly to the metallic tube, forming a jacket, may be
taken up by the steam or water of the boiler substantially as described.
5. The manner of constructing the tube, forming a jacket such as set forth in
the Claim 4 so that the inner wall covered with a layer of enamel to insulate it
from the pipe may join-without any intermediate free spaces-the outer wall of
the outline of the column of thermo-electric elements substantially as described
and illustrated in the accompanying drawings with reference to Figures 4 to 7.
6. The manner of constructing the tube forming a jacket such as set forth in
Claim 4 so that between the inner wall of it and the outer wall of the outline of
the column of thermoelectric elements there may be an open space through which
passes the air before entering the fire box, becoming in this way heated and
forming the means for bringing back to the fire box the heat radiated from the
cold junctions substantially as described and illustrated in the accompanying
drawings with reference to Figures 7 and 5.
7. The manner of constructing the discs of thermoelectric elements such as
claimed in the preceding claims, so that the columns composed of these elements
are placed directly in the chamber for water and steam of a horizontal boiler, the
heating tubes of which pass through central holes in the discs which are arranged
in the upper part and constitute the hot junctions whereas the ribs which are

page_text: continuations of the discs are in the lowest part of the boiler and constitute the
cold junctions substantially as described and illustrated in the accompanying
drawings with reference to Figures 1 to 4³.
8. In a vertical or horizontal thermoelectric boiler compose of elements such
as described in the preceding claims, recovering of the heat radiated from the
outside of the fire box of the boiler, of the steam pipes of the chimneys and of
the smoke box by forcing the air, before it enters the firebox, to pass through
hollow jackets formed by outer shells through a heating chamber, formed between
the smoke-box and the boiler, through the tubes in the boiler, through the .flues
and apertures, made in the brickwork so that none of the surfaces radiating part
of the heat absorbed directly or indirectly from the fire box heating or escaping
gases should be in direct contact with the atmospheric air that is to say that none
of the heat absorbed by parts of apparatus should be lost in the atmosphere except
through the chimney substantially as described.
9. The manner of applying the principles set forth in Claim 8 substantially as
described and illustrated in the accompanying drawings with reference to
Figures 1 to 64 for a vertical boiler and Figures 7 to 9 for a horizontal
boiler.
10. The combination with the principles and arrangements set forth in the
preceding claims of leading the steam pipes on one side into the smoke-box and
on the other side into the ash-pit in order to get the steam superheated by means
of heat which would be otherwise lost so as to force the draught and to draw the
air strongly in the fire-box substantially as described.
11. The manner of applying the principles and arrangements set forth in the
preceding claims and having for its purpose the recovering of the heat radiated
from the surface of the cold junctions and returning that heat to the fire-box
substantially as described and illustrated in Figure 5B the distinctive feature of
which is an arrangement of two concentric tubes at the outline of the column of
thermoelectric elements constituting regenerating jackets and forming free annular
spaces for the passage of air supply which going along the outline of the column
meets sprays of cooling water arranged in a ring and enters into the firebox mixed
with steam.
Dated this 12th day of December 1895.
BOULT & WADE,
Agents for the Applicant.