Thermoelectric system

Details Thermoelectric system Thermoelectric system

1999-06-30

2001-05-15

Gorgos, Kathryn (Department: 1741)

Batteries: thermoelectric and photoelectric

Thermoelectric

Adjuncts

C136S205000, C136S203000

Reexamination Certificate

active

06232543

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoelectric system to supply power (electric energy) generated by a thermoelectric power generator which generates electricity by utilizing an outside temperature difference to a load so as to operate the load. The present invention especially relates to a thermoelectric system which provides a function to adequately control power supply from a thermoelectric power generator to a load, compensating for an influence of the Peltier effect peculiar to the thermoelectric power generator.
2. Description of the Related Art
There exists a thermoelectric system which generates electric power from heat energy caused by an outside temperature difference using a thermocouple and drives electronic equipment such as an electronic timepiece and the like utilizing electric energy obtained from the power generation.
An electronic timepiece driven by generated power from a thermoelectric power generator shown in
FIG. 6
can be cited as a conventional example, which applies such a thermoelectric system to a small portable electronic device.
The electronic timepiece has a configuration in which a load means
20
is connected to the thermoelectric power generator
10
and power generated by the thermoelectric power generator
10
can be used with the load means
20
.
The load means
20
is configured with a voltage-up converter
23
, a timekeeping means
21
and an accumulator
22
. The voltage-up converter
23
is connected to the thermoelectric power generator
10
and raises the voltage to twice that of the voltage generated by the thermoelectric power generator
10
.
The timekeeping means
21
having a time-clock function and the accumulator
22
which is a second battery are connected in parallel to an output side of the voltage-up converter
23
, and the accumulator
22
is charged by a voltage-up output of the voltage-up converter
23
to supply the charged power to the timekeeping means
21
.
Furthermore, the electronic timepiece is provided with a generated voltage detector
35
using an amplifier circuit to detect the generated voltage of the thermoelectric power generator
10
, and a controller
36
to control operation of the voltage-up converter
23
in accordance with the detected voltage.
The thermoelectric power generator
10
is configured to connect plural thermocouples in series. In the case that the electronic timepiece in this example is a wrist watch, the thermoelectric power generator
10
is disposed so that a warm junction side is contacted with a case back of the wrist watch and a cold junction side is contacted with the case which is insulated against heat from the case back. Heat energy created by a temperature difference between the case back which closely contacts an arm of the person who carries the wrist watch and the case exposed to the outside air, is converted to electric energy.
In an electronic time piece utilizing such a conventional thermoelectric system, generated voltage by the thermoelectric power generator
10
is raised by means of the voltage-up converter
23
after being charged to the accumulator
22
and then used to operate hand-driving of the timekeeping means
21
and the like with the charged electric energy.
At this time, when the generated voltage of the thermoelectric power generator
10
detected by the generated voltage detector
35
exceeds a predetermined value, the controller
36
considers that the generated power of the thermoelectric power generator
10
is applicable and outputs a signal to operate the voltage-up converter
23
. Through this process, the voltage-up converter
23
starts voltage-up operation to raise the generated voltage of the thermoelectric power generator
10
to charge the accumulator
22
. On the other hand, when the generated voltage of the thermoelectric power generator
10
detected by the generated voltage detector
35
is less than a predetermined value, the controller
36
stops the voltage-up operation of the voltage-up converter
23
to stop power supply to the load means
20
from the thermoelectric power generator
10
. At the same time, the controller
36
prevents electric energy charged in the accumulator
22
from discharging to the thermoelectric power generator
10
side.
In the conventional thermoelectric system, when the thermoelectric power generator
10
used for a power generating device is given a higher range of temperatures on the warm junction side and a lower range of temperatures on the cold junction side, the thermoelectric power generator
10
generates electricity through the Seebeck effect and outputs generated voltage (incidentally, the generated voltage caused by Seebeck effect is called thermal electromotive force). Especially, when the thermoelectric power generator
10
has no load, generated voltage proportional to the temperature difference existing between its own warm and cold junctions can be obtained from the thermoelectric power generator
10
.
However, when a load is connected to take out power from the thermoelectric power generator
10
, current flows from the thermoelectric power generator
10
to the load. The current causes the Peltier effect which is a reaction of the Seebeck effect and a phenomenon which reduces the temperature difference given to the thermoelectric power generator
10
. That is, when current flows from the thermoelectric power generator
10
to the load, an exothermic reaction occurs on the cold junction side and an endothermic reaction takes place on the warm junction side. Through this Peltier effect, the temperature difference existing in the thermoelectric power generator is reduced, such that the generated voltage which is a thermal electromotive force is also reduced.
However, in the conventional thermoelectric system, temporary reduction of the thermal electromotive force caused by the Peltier effect is not considered, and the temporary reduction of the thermal electromotive force is merely considered to be the result of a temperature change in the outside circumstances.
Therefore, if the thermoelectric system is configured to switch between operation and suspension of the voltage-up converter in accordance with the magnitude of the generated voltage of the thermal power generating device as above, there exists a disadvantage that the voltage-up converter repeatedly performs the operation and the suspension when the value of the generated voltage is close to the detection threshold value.
That is, when a thermoelectric system is configured to switch between supply and suspension of power to a connected load in accordance with the value of generated power from a thermoelectric power generator, it becomes impossible to precisely measure the thermal electromotive force while the load is in operation. As a result, there may be cases where generated power from the thermoelectric power generator can not be used effectively.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-described disadvantages in a thermoelectric system, to facilitate effective utilization of generated power energy from the thermoelectric power generator while compensating for the influence of the Peltier effect on the generated voltage of the thermoelectric power generator, even when the Peltier effect occurs as a result of power supply from the thermoelectric power generator to a load means.
In order to achieve the above-described object, the thermoelectric system according to the present invention comprises: a thermoelectric power generator provided therein with a plurality of thermocouples electrically in series, a load means for utilizing generated power from the thermoelectric power generator, and a controller for controlling power supply and suspension of the power supply to the load means in accordance with the generated voltage, wherein the controller is provided with a compensating means, when power is continuously supplied to the load means from the thermoelectric power generator for more than a predetermined period of time, which measu

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