US20200208886A1

US20200208886A1 - Device for storing temperature-controlled fluids

Info

Publication number: US20200208886A1
Application number: US16/615,931
Authority: US
Inventors: Peter Adelmann
Original assignee: Nexol Photovoltermic AG
Current assignee: Nexol Photovoltermic AG
Priority date: 2017-05-24
Filing date: 2018-05-23
Publication date: 2020-07-02
Also published as: EP3491301B1; DE102017111492A1; EP3491301A1; WO2018215510A1; DE102017111492B4

Abstract

The invention relates to a device for storing temperature-controlled fluids, comprising at least one container (20), a Peltier element (30), the hot side (301) of which is in contact with at least one wall (201) of the container (209), at least one device (40) for delivering ambient air to the cold side (302) of the Peltier element (30), and at least one electrical energy source (50, 501, 502) for supplying the Peltier element (30) and the device (40) for delivering the ambient air. For low-loss storage of the fluid in the container (20), the device (40) for delivering ambient air can be operated according to the temperature of the ambient air and the heating capacity of the Peltier element (30) can be controlled according to the currently produced electrical energy of a photovoltaic solar generator (501) forming an electrical energy source. Preferably, times and/or durations of the heat energy emitted from the Peltier element (30) and/or from an accumulator (502) to the fluid can be controlled by a control appliance (6) on the basis of at least one requirements specification stored in the control appliance (60).

Description

The invention relates to a device for low-loss storage of temperature-controlled fluids, according to the preamble of claim 1.
A device for storing temperature-controlled fluids is known from German Utility Model DE 20 2009 015 549 U1. It is a device for heating water with the help of solar cells. The device comprises a photovoltaic solar generator, to which a Peltier element connected to a fluid container, for example by means of a DC/DC converter, is connected.
The object of the invention is to provide a device for highly efficient generation and low-loss storage of temperature-controlled fluids, such as water.
This object is achieved by a device having the features of claim 1. Advantageous embodiments of the invention are specified in the related dependent claims.
With the present invention, highly efficient production and low-loss storage of temperature-controlled fluids, such as water, is possible, depending on different requirement profiles. In particular, such phases, in which the photovoltaic solar generator generates no energy due to lack of sunlight, can be bridged by means of the device according to the invention, without significant cooling of the fluid. The device according to the invention allows for extremely high efficiency, in which the electrical power used is converted by the additional use of free available heat into a multiple of heat. By means of the invention, a coefficient of performance (COP) of 2.2 on average can be achieved, whereas with cold fluid in the container and a low electric power, even peak COP values of 5 to 6 are achieved and this does not fall, even under the most unfavorable conditions, under 1.5. The invention thus enables a very efficient conversion of a supplied electric power into a multiple of heat energy of the fluid to be heated.
As an application of the invention, energy self-sufficient dwellings without connection to regulated supra-local power grids may serve as an example.
The device for storing temperature-controlled fluids according to the invention comprises at least one container and a Peltier element. The hot side of the Peltier element is in contact with at least one wall of the container. In addition, at least one device is provided for delivering warm ambient air and/or a heated fluid to the cold side of the Peltier element and at least one electrical energy source for supplying the Peltier element and the device for delivering ambient air and/or a heated fluid. The fluid delivered for example by means of a pump to the cold side of the Peltier element can come, for example, as recovered heat from a waste heat exchanger, from a geothermal plant or from a solar thermal system, and thus, just as the ambient air, is delivered with a much lower energy use than that amount of thermal energy contained in the fluid.
The device for delivering ambient air and/or a heated fluid is operable for low-loss storage of the fluid in the container as a function of the temperature of the ambient air. This avoids the device for delivering ambient air to the cold side of the Peltier element being operated at times when no energy can be generated in the photovoltaic solar generator for applying to the Peltier element, for example at night. A blowing onto the Peltier element with cold air is thus avoided, because that would lead in these phases, by an unavoidable heat conduction from the cold side to the warm side of the Peltier element, to an undesirable cooling of the fluid temperature in the container.
The heating power of the Peltier element is controlled as a function of the currently generated energy of the electrical energy sources, which is designed in particular as a photovoltaic solar generator. In addition, the time and the duration of time and/or the heat energy delivered by the Peltier element to the fluid can also be controlled. This is done using at least one requirement profile, stored in a control appliance, for providing the temperature-controlled fluid. As reference times, for example, sunrise and sunset can be used, but also personal habits of the users of the device. For example, in a requirement profile it can be determined at what time of the day what amount of warm water should be available in which temperature range. For example, every morning at 7:00 am, 500 liters of warm water with a temperature of 40° C. should be available in the container.
In an advantageous development of the device according to the invention, a further energy source is formed by an accumulator. The accumulator is preferably chargeable by means of the photovoltaic solar generator. The accumulator buffers and smooths the energy generated by the photovoltaic solar generator and supplies the Peltier element regardless of the currently generated electrical power of the photovoltaic solar generator with the required electrical energy according to the respective requirement profile. With the help of the at least one requirement profile, for example, a time grid for the connection and disconnection of the accumulator for an actuation of the Peltier element can be generated.
In an advantageous embodiment, a DC/DC converter is connected downstream from the photovoltaic solar generator for adapting the voltage generated by the solar generator to the useful voltage required by the Peltier element or by the device for delivering ambient air. The photovoltaic solar generator is thereby adaptable to the Peltier element by means of the DC/DC converter regulated either for a constant solar generator voltage or to maximum solar generator power.
An incoming heat loss of the fluid in the container is compensated by supplying the Peltier element with a small amount of electrical energy. This is particularly necessary if the required warm air and/or sunlight is not possible—for example, during the night. By supplying the Peltier element with a low electrical power of, for example, 1 W, the heat losses of the fluid in the container, which otherwise occur due to heat conduction through the Peltier element, can be effectively and efficiently blocked off on the order of magnitude of approximately 5 to 6 W.
In a particularly advantageous development of the device, the cold side of the Peltier element is arranged in a vertically arranged channel for guiding the ambient air or forms part of a wall of this channel. In addition, a device for delivering ambient air is arranged in the channel. This channel has at least one ascending and one descending part and a transition from ascending to descending part, which is closed at the top.
At an inlet or outlet end, the channel particularly preferably has a grid and/or a plurality of pipes. By the air guide with a supply from below in the descending part and a downward discharge in the descending part, the heat loss in the device can be reduced. If the blower, which is arranged in particular in the ascending part of the duct, stands still, the cold side of the Peltier element is heated by its heat conduction to the temperature of the fluid in the tank. The air in the channel heats up and remains due to the low density, which is responsible for a buoyancy, in the channel, i.e. a standstill of the air results. This thus transforms from a heat conductor into an insulator. As a result, heat losses can be prevented by convection. The grid and/or the pipes are preferably formed from a poorly heat-conducting material and prevent a turbulence of the air in the channel, in particular by an arrangement in an input region of the channel. As a result, heat losses can be reduced by an external air movement.
According to a particularly advantageous development of the device and/or the channel, these have on at least one wall a heat-insulating layer of a plastic and/or of a natural material. As a result, the aforementioned possible heat loss can be additionally reduced. The heat-insulating layer can be formed, for example, from polyurethane foam, polystyrene plates or hemp plates.
In a further particularly advantageous embodiment of the entire apparatus for storing temperature-controlled fluids, the container can be arranged in a spatially separate position relative to the at least one electrical energy source. As a result, the device can also be used in cramped or difficult conditions, for example, when the container must be placed at a different altitude than the solar generator. In contrast to a thermal solar generator, it is completely uncritical if the container is higher than the photovoltaic solar generator, since only its electrical energy must be passed to the Peltier element and no hot water must be pumped using additional electrical energy to the container.
For a simple operation of the device, in a further development of the invention, the at least one requirement profile can be entered by programming the control appliance by a user. Alternatively, the at least one requirement profile can be established by measurements by means of sensors which record the withdrawals of the fluid from the container according to the time and the quantity. Advantageously, the control appliance can be controlled and/or programmed via a remote control. The remote control can be done via a mobile phone app.

Embodiments of the device according to the invention will be explained in more detail with reference to the drawings. In the drawings:

FIG. 1 is a schematic overall view of the device for storage of temperature-controlled fluids,

FIG. 2 is a schematic representation of the operation of the device in a first exemplary embodiment,

FIG. 3 is a schematic representation of the operation of the device in a second exemplary embodiment and

FIG. 4 is a schematic representation of the operation of the device in a third exemplary embodiment.

In a schematic representation of the device 10 in FIG. 1, a hot side 301 of a Peltier element 30, due to its good thermal conductivity, abuts a wall 201 of a container 20, which is filled with a heat-controlled fluid, such as water. A cold side 302 of the Peltier element 30, opposite of the hot side 301 thereof, abuts a heat sink 92. Alternatively to an abutment of the hot side 301 against the wall 201 of the container 20 or an abutment of the cold side 302 against a heat sink 92, the hot side 301 and/or the cold side 302 may also be integrally formed with the wall 201 and the heat sink 92.
The Peltier element 30 is connected to a photovoltaic solar generator 501. The connection is made in this embodiment via a DC/DC converter 70. In an alternative embodiment, instead of the photovoltaic solar generator 501, another electrical source 50 (not shown) may also be used.
The heat sink 92 resting against the cold side 302 of the Peltier element 30 or integrally formed therewith is heated by the temperature of the ambient air. In order to support this heating, a fan 807, which may be configured as a fan, is arranged on the cold side 302 of the Peltier element 30.
For heating the cold side 302 of the Peltier element 30, the supply of a heated fluid can additionally or alternatively be provided for the purpose of delivering ambient air. This fluid delivered example by means of a pump (not shown) to the cold side 302 of the Peltier element 30 can come, for example, as recovered heat from a waste heat exchanger, from a geothermal plant or from a solar thermal system, and thus just as the ambient air, be delivered with a significantly lower use of energy be to the cold side 302 of the Peltier element 30, as this corresponds to the heat energy contained in the fluid additionally usable in the system. The efficiency of the entire system of container 20 and Peltier element 30 is substantially improved by this additional use of free available heat on the cold side 302 of the Peltier element 30.
In order to be able to remove as much electrical energy as possible from the photovoltaic solar generator 501, the DC/DC converter 70 is regulated via a control appliance 60. Thus, the photovoltaic solar generator 501 can either be maintained at a constant solar generator voltage or at the point of maximum solar generator power (“MPP tracking”). The controller 60 is controlled by a remote control 62 and/or is programmable.
In the event that the required warm air and/or sunlight is not available, which is usually the case, for example, at night, the fluid in the container 20 could be cooled by the thermal bridge formed by the Peltier element 30 and the heat sink 92. To prevent this, the Peltier element 30 can be operated via an accumulator 502 even in these times with a low electrical power. With this small electrical power supplied to the Peltier element 30 of, for example, 1 W, a much greater thermal power loss, for example, 5 to 6 W is prevented.
In FIG. 2, a first exemplary embodiment of the device 10 is shown with a device 40 having a heat sink 92 for delivering ambient air with a channel 80 having an ascending part 801 and a descending part 802. The two parts 801 and 802 of the channel 80 are interconnected by a transition 803 which is closed at the top. In this case, the tubular housing part of the descending part 802 has a smaller diameter than the ascending part 801. In this first exemplary embodiment, the descending portion 802 of the channel 80 is arranged laterally on the container 20.
The device 40 comprises a side wall 42 enclosing the device, a partition wall 46 arranged between the ascending part 801 and the descending part 802, and a cover 44 which delimits the transition 803 from the ascending part 801 to the descending part 802 upwards.
The container 20 is arranged in a region immediately following the side wall 42. The Peltier element 30 is arranged in a partial area between the side wall 42 and the container 20. In addition, a connecting line 22 is formed near the side of the container 20 facing the device 40. When the Peltier element 30 is heated by the warm fluid rising in it, the connecting line 22 ensures circulation of the fluid in the container 20.
To reduce heat losses, the device 40 and the container 20 are provided with a heat-insulating layer 806. This may consist of a plastic or of natural materials such as polyurethane foam, polystyrene plates or hemp plates.
A nighttime cooling of the fluid in the container 20 can also be prevented or reduced by a reflector (not shown) being mounted around the heat sink 92 on the cold side 302 of the Peltier element 30, which reflector reflects the heat radiation.
The heat loss can be additionally reduced by introducing an ambient air L40 into the ascending part 801 for air guidance and returning it as an air L through the descending part 802 again. In an outlet opening A and/or in an inlet opening E of the channel 80, a grid 804 and/or pipes 805 are provided. The grid 804 and/or the pipes 805 in the ascending part 801 of the channel 80 are adjoined by a fan 807 as part of the device 40 for delivering ambient air.
In this first embodiment, the device 40 for delivering ambient air and the container 20 are formed from two separate and interconnectable components. The connection is preferably by means of a non-positive connection such as screw or by means of a cohesive connection such as welding or bonding.
In the second embodiment according to FIG. 3, the ascending part 801 of the channel 40 is arranged on the container 20. Grid 804 and/or pipes 805 and the fan 807 are arranged analogously to FIG. 2. The same applies to the side walls 42, the partition 46 and the cover 44. The ambient air L40 is introduced into the ascending part 801 through the inlet opening E, and leaves the outlet port A of the descending part 802 as air L.
The Peltier element 30 is arranged between the side wall 42 of the device 40 facing toward the container 20 and forming the cold side 302 of the Peltier element 30 and a heat exchanger 94 arranged in the container 20 forming the hot side 301 of the Peltier element 30. In the heat exchanger 94, the temperature-controlled fluid undergoes a circulating circulation process in which colder fluid F1 is sucked from the container 20 at the bottom thereof and heated fluid F2 is discharged again to the container 20 at the top thereof.
FIG. 4 shows a third exemplary embodiment of the device 10 in which the container 20 is arranged above the device 40. The supply of the ambient air L40 is also realized via the inlet opening E of the ascending part 801 of the channel 80, which is provided with a grid 804 and/or pipes 805, which are formed as air channels, which is followed by a fan 807. The air L is passed through a heat sink 92, which is formed as a flow-through pipe and is preferably arranged at the partition 46 perpendicular to the side walls 42. The Peltier element 30 is arranged in the container 20 between the heat sink 92 forming the cold side 302 in the device 40 and the heat exchanger 94 forming the hot side 301. The heat sink 92 and/or the heat exchanger 94 may be formed according to an advantageous embodiment of the invention as a so-called heat pipe (“heat pipe”).
The container 20 and the device 40 are formed in this exemplary embodiment as a one-piece component, for example as a cast or produced by a coating method block.
In a further embodiment (not shown), a pipe, which has openings at defined intervals, is arranged in the container 20 on the side facing the hot side 301 of the Peltier element 30. Due to the difference in density of the fluid in the container 20 due to the different temperatures in the container 20, a circulation of the fluid takes place, which is based on the density difference of water with a different temperature. In addition, the heated water is then charged in a corresponding temperature zone of the container 20 (“layer charge” container 20).
The photovoltaic solar generator 501 charges the accumulator 502 shown in FIG. 1 with excess electrical energy which is temporarily not required for operating the Peltier element 30 and the blower 807 during intense solar irradiation (operating mode: “Charging mode of the accumulator 502”). The accumulator 502 then energizes the Peltier element 30 in times when heat losses in the container 20 must be prevented (typically at night) or in which the photovoltaic solar generator 501 alone cannot generate enough energy to produce the required amount of heated fluid (e.g. at or before sunrise; operating mode: “Heating by accumulator”).
By means of the invention, a COP (“coefficient of performance”) of on average 2.2 can be achieved, with cold fluid in the container 20 and a low electric power even a peak COP of 5 to 6 is achieved and this, even under the most unfavorable conditions, does not fall below 1.5. The invention thus enables a very efficient conversion of a supplied electric power into a multiple of heat energy of the fluid to be heated.
It is particularly advantageous if a clock in a microcontroller in the control appliance 60 receives at least one reference point by measuring the energy generated by the solar generator 501. This point of reference arises from the sunrise and the sunset, both of which result in a significant change in the generated electrical energy at the solar generator. In this case, the microcontroller can be additionally connected to a GPS receiver and a memory with a database on the local seasonal sunrises and sunsets. These reference points ensure that deviations of the clock, such as occur almost unavoidably over a relatively long period of time, can be corrected by the control appliance 60. As a result, the user can always remove the desired amount of tempered fluid from the container 20 at the time he/she desires.
The accumulator 502 is also preferably used for a smoothing function by intercepting and storing peak powers of the solar generator 501, such as may occur in cloud gaps, for example, so that the electrical energy supplied to the Peltier element 30 is always kept as evenly as possible at a rather low level where the efficiency of the overall system is highest.
The accumulator 502 is particularly preferably designed as a hybrid storage, with a lead-acid battery, which is preferably always charged as fully as possible and with a lithium-ion battery, which stores the remaining energy generated by the solar generator 501 and currently not required by the Peltier element 30. However, the accumulator 502 may also be formed only by a lithium-ion battery. Due to the advantageous control by means of the control appliance 60, the Peltier element 30 is always charged with the lowest possible power, which allows a high COP of 4 to 5, and the excess electrical energy stored in the accumulator 502.
In order to make the system less sensitive to partial shading, additional bypass diodes are installed in the solar generator 501. One bypass diode is preferably installed parallel to each twelve solar cells or to an even smaller number of solar cells.
An added benefit of the invention is to utilize the heat sink created on the cold side 302 of the Peltier element 30 to cool a room. The heat can be removed from the room air by a suitable air flow or through a suitable fluid circuit.
It would also be possible to cool the solar cells of the solar generator 501 itself and thereby enable a higher power production.
For reasons of efficiency, solar cells have so far rarely been used for hot water production. By the described device, the heat output compared to pure electric solar cell power can be significantly increased. By the Peltier element 30 and the heat sink 92, heat is extracted from the environment, which is supplied to the container 20 together with the electrical supply energy for the Peltier element 30. As a result, a total amount of energy is supplied to the container 20, which is significantly above the amount of energy that would be supplied only by the electrical energy.
Compared to solar thermal water heaters, there is the advantage that the energy which is conducted to the container 20 acting as a hot water tank is transported in easy-to-install cables in the form of electrical energy and not by means of pipes in the form of warm water. By the energy transport via electrical energy, the container 20 can also be relatively far away and placed independent of the altitude of the solar generator 501. If the container 20 is arranged lower than the solar generator 501, one does not need—as usual with solar thermal water heaters—a pump for energy transport.
If the water outside the container 20 is additionally heated by a heat source and supplied to the container 20 via pipes or hoses, this cycle can be interrupted during the night by, for example, a device formed as a resistance valve device and heat losses in the container 20 can thereby be reduced.
Another advantage is that a photovoltaic water heater generates warm water even at low ambient temperatures and low radiation power.

LIST OF REFERENCE SIGNS

10 device
20 container
201 wall
202 connection line
30 Peltier element
301 hot side
302 cold side
40 device (for delivering ambient air)
42 side wall (of 40)
44 cover (of 40)
46 partition (of 40)
50 energy source
501 solar generator
502 accumulator
60 control appliance
62 remote control
70 DC/DC converter
80 channel (of 40)
801 ascending part (of 80)
802 descending part (of 80)
803 transition (between 801 and 802)
804 grid
805 pipe
806 layer (on 20 and 80)
807 blower
92 heat sink
94 heat exchanger
A outlet opening
E inlet opening
F1 fluid
F2 fluid
L air
L40 ambient air

Claims

1. Device (10) for storing temperature-controlled fluids with at least one container (20), having a Peltier element (30) whose hot side (301) is in contact with at least one wall (201) of the container (20), having at least one device (40) for delivering ambient air (L40) to the cold side (302) of the Peltier element (30) and having at least one electric power source (50) for supplying the Peltier element (30) and the device (40) with ambient air (L40), characterized in that for the low-loss storage of the fluid in the container (20), the device (40) for delivering ambient air (L40) is operable as a function of the temperature of the ambient air (L40), and the heating power of the Peltier element (30) can be controlled as a function of the currently generated electrical energy of a photovoltaic generator (501) forming the electric energy source (50).

2. Device (10) according to claim 1, characterized in that a further electrical energy source (50) is formed by an accumulator (502).

3. Device (10) according to claim 2, characterized in that the accumulator (502) of the photovoltaic solar generator (501) is chargeable.

4. Device (10) according to one of the preceding claims, characterized in that the photovoltaic solar generator (501) is connected to a DC/DC converter regulating the solar generator voltage (70).

5. Device (10) according to claim 4, characterized in that the solar generator (501) with a DC/DC converter regulated to constant solar generator voltage or maximum solar generator power (70) is adapted to the Peltier element (30).

6. Device (10) according to any one of the preceding claims, characterized in that the heat loss of the fluid in the container (20) can be compensated by supplying a small amount of electrical energy or by charging the Peltier element (30) with a low electric power.

7. Device (10) according to any one of the preceding claims, characterized in that the cold side (302) of the Peltier element (30) is arranged in a vertically disposed channel (80) for guiding the ambient air (L40).

8. Device (10) according to claim 7, characterized in that the channel (80) comprises at least one ascending part (801) and one descending part (802) and a transition (803) from the ascending part (801) to the descending part (802), which is closed at the top.

9. Device (10) according to claim 7 or 8, characterized in that the channel (80) comprises, at least in sections, at least one grid (804) and/or a plurality of pipes (805).

10. Device (10) according to at least one of the preceding claims, characterized in that at least one wall of the container (20) and/or the channel (80) is provided with a heat-insulating layer (806).

11. Device (10) according to at least one of the preceding claims, characterized in that the container (20) can be arranged in a spatially separate position from at least one electrical energy source (50; 501, 502).

12. Device (10) according to one of the preceding claims, characterized in that the cold side of the Peltier element (30) can be heated alternatively or additionally to the ambient air (L40) by means of a further fluid.

13. Device (10) according to one of the preceding claims, characterized in that the time and/or the time duration and/or the heat energy emitted to the fluid by the Peltier element (30) is controlled by a control appliance (60) based on at least one requirement profile for providing the temperature-controlled fluid stored in the control appliance (60), wherein the at least one requirement profile can be entered in the control appliance (60) by programming by a user or can be calculated by means of an algorithm stored in the control appliance with values determined by sensors, which measure the withdrawals from the container (20) by time and/or amount and/or measure temperature.

14. Device (10) according to claim 13, characterized in that the control appliance (60) is controlled and/or programmable via a remote control (62).

15. Device (10) according to claim 14, characterized in that the remote control (62) can take place via a mobile phone application.