IMPROVED CONSTRUCTION OF THERMOELECTRIC BATTERIES
Year: 1886

page_text: Date of Application, 1st July, 1886.
Complete Left, 31st Mar., 1887.
Complete Accepted, 3rd May, 1887.
I, GEORGE EDENSOR DORMAN of Brook House, Stafford, in the county of Stafford,
Engineer, do hereby declare the nature of my invention for IMPROVED CONSTRUCTION
OF THERMOELECTRIC BATTERIES, to be as follows:-
My invention relates to the construction of thermoelectric batteries, or the apparatus
used in converting heat, directly into electricity, the objects of my invention being to
provide a thermoelectric battery, which may be efficiently used on a large and small
scale and which shall he convenient and compact in form, and at the same time easy
and economical in construction. My invention consists in arranging a number of
thin rectangular chambers, or thin hollow slabs of cast iron or other suitable
material, one slab above another, in a vertical pile, the slabs being alternately hot and
cold, between the slabs are arranged the metals known in thermoelectric batteries as
the elements, one side of, or set of junctions of the elements, being adjacent to and
pressing against a hot slab, and the other side of the elements pressing against a cold
slab, the sequence in the parts of the pile being, a cold slab, elements, hot slab,
elements, cold slab, elements, hot slab, clements, cold slab, the pile being thus built
up, to any convenient height, the whole pile being in a suitable frame, the slabs with
the elements between them being tightly pressed together, by means of bolts or
screws.
The surfaces of the slabs, are planed or rendered flat, and in order to prevent
electrical contact with the elements, the slabs are faced with a thin coating of enamel,
or a thin sheet of porcelain, terracotta, paper, mica, or asbestos or other suitable
material preferably a good heat conductor.
Each of the hot slabs has an inlet and outlet which allow of the passage through
the slab of a heated fluid, which may be oil, bring, or other suitable fluid, similarly
all the cold slabs are cooled by the passage through them, of cold water, or brine or
other suitable fluid.
When a battery of great power in small space is required, and where a little more
consumption of heat, is not of importance, the fluids may pass independently and
directly through each slab, at their greatest extremes of temperature, where however

page_text: a low consumption of fuel is desired, the hot fluid may pass through the hot slabs,
through one slab after another, entering at the top of the pile and leaving at the
bottom, similarly the cold fluid through the cold slabs, but entering at the bottom of
the pile and leaving at the top, thus the fluids circulate through the pile in opposite
directions, and the heat of the hot fluid is more nearly all absorbed.
After the hot fluid has passed through the pile it is returned to a heater, the cold
fluid being returned to a cooler or refrigerator. The elements between the slabs may
be similar to those used in the well known "Clamond "thermoelectric battery, being
of sheet iron and an antimony and zinc alloy, but I have found that the thickness of
the alloy, in the direction in which the current flows may be greatly reduced, a
thickness of foil being sufficient for a good result, and I prefer in practice to use
elements in which the alloy or galena or other suitable material is about one sixteenth
of an inch thick, by thus reducing the thickness of the alloy, the resistance to the
passage of the electric current of the whole pile or battery is greatly reduced, thus
securing a great increase of economy in consumption of heat, and in the amount of
expensive alloy required in the construction of the battery. According to the above
construction, the elements may be made in the form of strips about three sixteenths
of an inch thick, the sheet iron on either side of the alloy being one sixteenth of an
inch thick, the thickness of the iron will however, vary according to the area of the
element, and may be made thicker in some parts than others, the strips suitably
electrically connected at the ends, being placed between the slabs, a hot slab being
on one side of the strips, a cold slab being on the other. In place of the antimony
and zinc alloy, Lead, german silver, galena, nickel, or other suitable material may be
used. The elements may be cast, as in the Clamond battery, or electroplating may
be used in their construction.
The elements throughout the whole pile may be connected electrically, in parallel
arc, or in series, as the circumstances require, where a low potential current only is
needed, a few strips of elements only, but of great width may be used.
Dated this 30th day of June 1886.

page_text: 1, GEORGE EDENSOR DORMAN, of Brook House, Stafford in the County of Stafford,
Engineer, 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:-
My invention relates to the construction of thermoelectric batteries, or the
apparatuses used in the conversion of heat directly into electricity such apparatusés
being also known as thermopiles.
The object of my invention is to provide a thermoelectric battery which may be
efficiently used on a large and small scale and which shall be easy and economical in
construction.
My invention consists in arranging a number of thin rectangular chambers or thin
hollow slabs of cast iron one slab above another the slabs being alternately hot and
cold, between the slabs being arranged or interposed the metals known in thermo-
electric batteries as the elements, one side of, or set of junctions of the elements being
adjacent to, or pressing against a hot slab, the other side or set of junctions of the
elements, pressing against a cold slab, the slabs with the elements between them being
tightly pressed together by means of bolts.
The surfaces of the slabs being planed or rendered flat, and in order to prevent
electrical contact with the elements, being faced with a sheet of paper.
Each of the hot slabs having an inlet and outlet allowing of the passage through
the slab of a heating fluid, each of the cooling slabs having an inlet and outlet allowing
of the passage of a cooling fluid.
Where efficiency in the transformation of the heat into electricity, and in the
utilization of the cooling fluid is not of importance, or when a battery of great power
with the least number of elements or occupying the least space is required, the
heating and cooling fluids may pass independently and directly through each slab
at their greatest extremes of temperature, the heating fluid having as many paths
through the pile as heating slabs, the cooling fluid as many paths as cooling slabs,
such mode of circulation may be known as parallel circulation, but where high
efficiency, or low consumption of heat, and the minimum amount of cooling water is
desired, the heating fluid should pass through the heating slabs of the pile, through
one slab after another or through the slabs in series, entering at the top or one
end of the pile, and leaving at the bottom or other end, the cooling fluid, through the
cooling slabs in series, but entering at the bottom of the pile and leaving at the top,
the heating and cooling fluids thus circulating through the pile in opposite directions,
such mode of circulation may be known as series circulation, by such circulation
the heat is nearly entirely absorbed from the heating fluid, so that, that fluid issues
from the pile cold or nearly approaching in temperature the initial temperature of the
cooling fluid, the cooling fluid issuing from the pile heated and utilized to its fullest
capacity.
In both arrangements of circulation the heating fluid after issuing from the pile
may be returned to a heater or may flow away, the cooling fluid being returned to a
cooler or flowing away.
In the accompanying drawings Figure 1. Sheet 1. represents a thermoelectric

page_text: battery constructed with parallel circulation, the slabs a. being heated slabs, b. cooling
slabs, c. clements, d. inlets, and E. outlets for the cooling fluid, F. being the pipe
conveying the cooling fluid to, and H being the pipe conveying the cooiing fluid
away from, the pile, similarly the pipes conveying the heating fluid to and away from
the pile are situated on the other side of the pile, the heating fluid inlets being as the
upper part of the slabs, the outlets at the lower.
Figure 2. is a plan of the battery shewn in Figure 1. H being the outlet pipe for
the cooling liquid, I the inlet pipe for the heating liquid, in both Figures K are the
bolts pressing the slabs and elements together.
In order to render clear the way in which the parallel circulation is less efficient
than the series circulation, in which the licating fluid issues from the pile cold,
I have appended Figure 3, in which A is a hot slab, B a cold slab, and which
represent a pair of the slabs of a pile with parallel circulation. If the slab A is
maintained by means of the heating fluid at a temperature of 120 degrees, the heating
fluid will issue from the slab at that temperature and in the flowing away of the
heating fluid, this heat will be wasted, if the heating fluid after issuing from the
slab A is returned to a heater to again act in heating the slab, the loss of heat will be
transfered to the heater, taking place in the escape of the gases of the furnace or
lamp heating the heater, the lowest temperature at which these gases, or the fluids of
any other heating medium heating the heater, can be caused to escape, being that
temperature at which the heating fluid issuing from the slab enters the heater, such
result being attained by the use of a heat economiser in connection with the heater,
so that where the heating fluid issues cold from the slab the gases or fluids heating
the heater may also escape cold.
In the parallel circulation by using slabs constructed as described with reference to
Figure S. sheet 3. and by making the deflectors shown in that Figure very numerous
and by circulating the heating and cooling fluids extremely slowly the heating fluid
might be caused to issue from the slabs cold, the cooling fluid at the same time issuing
heated, the circulation then becoming similar in result to the series circulation, but the
series circulation where the slabs are numerous affords the advantage of a single path
only being required to each fluid through the pile.
Figures 5 and 6 sheet 2. shew a battery constructed with series circulation, which
will be more readily understood on reference to Figure 4, which shows a diagram-
matic view of a pile with series circulation, and in which A are heating slabs,
B cooling slabs, C. elements, the full black lines tracing the pipe connections for the
cooling Huid, the dotted lines those for the heating fluid, the heating fluid entering
at D and leaving at E, the cooling fluid entering at F and leaving at E. the heating
fluid in circulating through the heating slabs, always entering at the upper part of
the slab and leaving at the lower, the cooling fluid through the cooling slabs entering
at the lower part of the slab, leaving at the upper.
In practice a pile may be arranged and worked as is indicated in Figure 4,
but it will be observed that a cooling or B slab, acts on either side of each heating
or A slab, and as the temperature of each cooling slab is different, one of the
cooling slabs may be cooling the heating slab, while the other from the way in
which the fluids are circulated, in certain parts of the slab, may not be very different
in temperature, I therefore replace the clements between some of the slabs by a
sheet of heat nonconducting material, so as to isolate the slabs of the pile into
pairs, the elements thus replaced being shown at o, the heat nonconducting material
being a sheet of asbestos millboard, it will be observed that the last cooling or B slab
being adjacent only to the nonconducting material would be now ineffective, if this
slab was now taken away it would leave the neighbouring A or heating slab exposed
to the cooling action of the air, it being always preferable to arrange the slabs so that
the end slabs may be cooling slabs. It is also now desirable that the slabs on either
side of the nonconducting material, should be as little different in temperature as
possible I therefore arrange the slabs so that the nonconducting material comes
between two cooling slabs, or two heating slabs, a thermoelectric battery so arranged,
being shewn in Figure 5, in which A are hot slabs, B cooling slabs, C clements,

page_text: D nonconducting material, the cooling fluid entering the pile at F, the pipes shewn,
being the cooling fluid connections and leaving at H, the heating fluid entering at K,
and leaving at E, the dotted lines tracing the pipe connections. Figure 6 shews a
plan of the battery in Figure 5, the cooling fluid entering at R, issuing at V, the
heating fluid entering at T, issuing at S, in both Figures the bolts pressing the slabs
and elements together are shewn at o.
The end and cooling slabs form at the same time, end plates being ribbed at the
back as shown in Figure 7. sheet 3. and which is an end view of the battery shewn in
Figures 5 and 6. Thermoelectric batteries thus constructed with parallel or series
circulation, may for convenience when being built be disposed vertically and may also
be worked vertically, but are preferably worked horizontally, as when the slabs lie
horizontally as when the pile is disposed vertically air or gases are liable to accumulate
in the upper part of the slabs keeping the fluids out of contact with the slab at
that part.
Figure 8 shews the construction of the slabs which may be used in both the parallel
and series circulations, both for the heating and cooling fluids, A are lugs through
which the bolts pass, B are deflectors or ribs for lengthening the circuits of tho
fluids. C and D are passages for the heating and cooling fluids, when the slab is a
heating slab is the inlet, D the outlet for the heating fluid, but when a cooling
slab, is the outlet and D the inlet for the cooling liquid. For convenience in
making the pipe connections the heating slabs are arranged in the piles shewn in
Figures 1, 2, 5 and 6 with the inlets and outlets on one side of the pile, the cooling
slabs with the inlets and outlets on the other side of the pile. The inlets and outlets
may be wrought iron pipe screwed into the side of the slab as shewn. Figure 9,
shews the lid of the slab, which may be screwed on to the slab, the heads of the.
screws being countersunk, a water tight joint being made between the lid and slab
with suitable jointing materials. The total thickness of the slab including the lid may
be about two inches.
Figure 10, shews the arrangement of elements on the slabs A and B being
terminals, C being end connections of the strips of elements being shewn diagram-
matically and should be of sufficient cross section not to be heated by the current, the
strips or chains of elements may be insulated from one another by strips of asbestos
paper and are shewn joined in series, but may be joined in parallel as is well
unlerstood.
The paper with which the slabs are faced may be asbestos paper, which may be
cemented to the slabs with gum or paste or otherwise.
The heating fluid may be hot water or oil, or other liquids such as are suited to
withstand a high temperature may be used.
Steam may be applied directly as the heating fluid or to a heater in a battery with
parallel circulation but in the series circulation unless its pressure is sufficient to
expell the condensed water, it is preferably applied to a heater, to heat water or other
liquid, the hot water or liquid then being used in the battery, the heating apparatus
then used may be such as is used for heating the feed water of steam boilers by
steam, and should be such that the condensed water flows away at the temperature at
which the water or other liquid forming the heating fluid of the pile enters the
heating apparatus. Where a furnace or lamp is used as the heat source an ordinary
boiler or water heating apparatus may be used, a heat economiser being used in
connection therewith, for reducing as described with reference to Figure 3. the
temperature of the escaping gases, to that of the water or heating fluid issuing from
the pile.
The cooling fluid may be water or where a low temperature is used may be brine
or other fluid not easily congealable. Where the same cooling fluid is used con-
tinuously, the cooler may be any apparatus such as is at present used in cooling warm
liquids by the action of the air or otherwise.
Where there is a large quantity of cooling water at hand the cooling water may
be sent through the pile in parallel, while the heating fluid is passed in the series
circulation, a slightly smaller pile being thus required than where both fluids circulate

page_text: in series. Both the heating and cooling fluids may be circulated where necessary by
centrifugal or other pumps worked by electro motors actuated by the current from the
pile or otherwise.
The number and size of the slabs will vary according to the current the battery is
required to give, a few slabs of large size, or a number of slabs of small size may be
used as desired. As it is preferable to have cold slabs as end slabs, the least number
of slabs that it is desirable to use in the parallel circulation is three, a hot slab being
between two cooling slabs, the least number in the series circulation being four, two
heating slabs, being between two cooling slabs.
Thermoelectric batteries thus constructed and with the elements hereafter described,
may be worked at very low temperatures, a difference of a few degrees in temperature
between the heating and cooling slabs, generating a current, the highest temperature
at which the pile may be worked by means of highly heated fluids, is limited to that
which the elements will endure continuously without injury a safe temperature for
elements constructed as herein described of antimony and zinc alloy and sheet iron
or copper, being a heat just below that which will singe paper.
The elements disposed between the slabs may be constructed of sheet iron and
antimony and zinc alloy as described in Sudre's specification numbered 5011 and
dated 9th December, A.D. 1878, but I have found that the thickness of the antimony
and zinc alloy or equivalent metal, may be greatly reduced in the direction in
which the current flows, and that for all differences of temperature at which the
pile may be worked, the alloy should to attain the most advantageous results be
made of extreme tenuity a thickness of foil being sufficient. I have found in practice
that thermoelectric elements may be constructed in which, with antimony and zinc
alloy the alloy is about one sixteenth of an inch thick, in some cases the alloy might
be made thicker up to one eighth of an inch, still experiencing considerable advantage
as compared with elements heretofor constructed, but in all cases the alloy or equivalent
metal should be of the ultimate thinness the construction and material of the element
permit.
By reducing in this manner, the thickness of the alloy the economical manufacture
or construction of thermopiles in which the thermoelectric elements are present in
very large quantities is rendered possible, and the resistance to the passage of the
current of each element and of the whole battery being reduced gives a corresponding
increase of efficiency in the conversion of the heat into electricity.
Figures 11, and 12, sheet 4, shew thermoelectric elements as used in the thermo-
electric battery known as the "Clamond," and as described in Sudre's specification
numbered 5041, dated 9th December, A.D. 1878, that in Figure 11, in which the
alloy A is about three eighths of an inch in thickness, being for use in thermopiles,
where the difference of temperature at which the pile is worked is ten degrees, that in
Figure 12, in which the alloy A is a little over an inch in thickness, where the
difference in temperature is three hundred degrees, in Figure 13, A shews the alloy
of the thickness I use when attainable for the construction of elements for all differ-
ences of temperature, the alloy or equivalent metal being of the thickness of foil or
thin writing paper, elements may be constructed of this thinness in practice, in which
the part A or alloy is thin sheet German silver, the parts B being of sheet iron, these
two parts being sweated or soldered on either side of the German silver.
Compound elements or those composed of three metals as shewn in Figure 14, in
which the part A is antimony and zinc alloy, B sheet iron or copper, C being
Bismuth, may be constructed with the alloy of reduced thickness, a chain of compound
elements thus made being shewn in Figure 15.
Compound elements are a little more efficient than the ordinary or simple elements,
but from the expense of the bismuth entering into their construction, simple elements
are preferable in practice.
Figure 16, shews a chain of elements such as I prefer to use, in which the antimony
and zinc alloy as shown at A is about one sixteenth of an inch thick, the parts
or strips B being of sheet copper or German silver or sheet iron, German silver
giving the highest power, and which may be economically used in elements thus

page_text: constructed, the parts or strips marked B in the Figures of elements shewn, not
requiring to be of such length as in elements in which the alloy is of great thickness.
The parts or strips B of German silver or copper or sheet iron should be about half
an inch in width, and the thickness of the strips B should be such as not to be heated
by opposing resistance to the current, and should be of little resistance as compared
with that of the alloy, the alloy may be about half an inch square in area, but where
conveniently constructed the elements may be of larger proportions excepting the
thickness of the alloy.
In manufacturing the elements as shewn in Figure 10 the parts B are first made
and bent into the form shewn, the strips being about or on those parts which will be
in contact with the alloy carefully tinned with solder, the parts B thus prepared are
then arranged between two iron strips CC shewn in Figure 17 and resting on an iron
plate D, at the same time strips E of asbestos millboard are placed against those parts
of the strips B, against which it is not required to cast the antimony and zinc
alloy, it will be observed that the ends of the strips B slightly overlap the strips
of asbestos E, belonging to the neighbouring B strip, the strips being arranged in
this manner so that when the strips Care screwed up by the bolts F, and with the
separating pieces H between, the strips B may be rigidly held, the melted alloy is
then poured into the recesses I thus formed, when the strip of elements is thus cast,
the strips of asbestos may be left in place, the overlapping parts of the strips B
retaining it. The alloy may be composed of one part by weight of zinc to two parts
of antimony, the alloy should be cast at as high a temperature as possible, and the
mould or strips C and plate D should be heated to a temperature slightly below the
temperature at which the solder with which the strips B are tinned begins to melt,
the solder used being such as is used in ordinarily soldering lead.
The mould may
be two feet or more in length and the strips C should be wide enough not to be easily
bent.
The alloy may be poured into the mould by means of a git shewn in Figure 18 in
section placed on the mould A being the git, C the iron strips or mould D the plate,
the slit K should be as narrow as the metal will pass through, so that when the
elements are cast, it may be easily broken off, the git may be about four or six inches
in length, after one part of the elements in the mould have been cast, it may be
moved further on, on the mould being so placed as to slightly overlap the elements
already cast. The git in being used should be raised to a dull red heat, so that the
alloy in being poured through it, may suffer as little reduction in temperature as
possible.
According to my present invention the efficiency of the series circulation is greater
than the parallel in the manner as described with reference to Figure 3 Sheet 1. but
I have found that the efficiency of the series circulation may be further increased in
other and different ways.
Having now particularly described and ascertained the nature of my said Invention,
and in what manner the same is to be performed I declare that what I claim is-
1st. In thermoelectric batteries of Slab construction, passing the heating and
cooling fluids through the slabs in series, or only the heating fluid through the slabs
in series as described.
2nd. In thermoelectric batteries of Slab construction or in which the elements are
disposed between slabs or similar heated and cooled surfaces, elements of the form
shewn in Figures 11, 12 and 14, constructed with the alloy or equivalent metal one
eighth of an inch or less in thickness as described with reference to Figures 13, 15
and 16.