System and method for storing and releasing energy

Abstract

A system for storing energy includes a hydrogen production unit for producing hydrogen, a hydrogen storage device for storing hydrogen, with a loading unit for loading a carrier medium with the hydrogen produced in the hydrogen production unit and with an unloading unit for unloading the hydrogen from the loaded carrier medium, a heat generation unit for generating heat and a heat storage unit for storing the heat generated by the heat generation unit, with the heat storage unit connected with the unloading unit in order to supply heat.

Claims

1. A system for releasing energy in a form of hydrogen comprising: an unloading unit for unloading hydrogen from a loaded carrier medium; a heat generation unit for generating heat; a heat storage unit for storing the heat generated by means of the heat generation unit, wherein the heat storage unit is connected with the unloading unit in order to supply heat; a power generation unit for generating electric power, wherein the power generation unit is connected with the heat generation unit in order to supply electric power for heat generation, wherein the heat from the heat storage unit is delivered directly to the unloading unit.

2. The system according to claim 1, wherein the power generation unit is connected with a hydrogen production unit in order to supply electric power for hydrogen production, wherein the power generation unit enables the generation of power from renewable energy sources, wherein the electric power is delivered from the power generation unit directly to the heat generation unit.

3. The system according to claim 1, further comprising: a hydrogen oxidation unit for generating electric power, wherein the hydrogen oxidation unit is connected with a power supply network for delivering the electric power.

4. The system according to claim 1, wherein the unloading unit for conveying unloaded carrier medium is connected with a loading unit, wherein a carrier medium temporary storage unit for storing the unloaded carrier medium is placed between the unloading unit and the loading unit and a carrier medium storage unit for storing the loaded carrier medium is placed between the loading unit and the unloading unit.

5. The system according to claim 1, further comprising: a hydrogen production unit for producing hydrogen.

6. The system according to claim 1, wherein the hydrogen is bound with the carrier medium in the loading unit.

7. The system according to claim 1, wherein the carrier medium storage unit is built into the loading unit.

8. The system according to claim 1, wherein the carrier medium storage unit is a tank and the carrier medium storage unit has at least one tank pipe for connection to an external pipeline system.

9. A system for releasing energy in a form of hydrogen comprising: an unloading unit for unloading hydrogen from a loaded carrier medium; a heat generation unit for generating heat; a heat storage unit for storing the heat generated by means of the heat generation unit, wherein the heat storage unit is connected with the unloading unit in order to supply heat; a power generation unit for generating electric power, wherein the power generation unit is connected with the heat generation unit in order to supply electric power for heat generation; and a control unit, which has a bidirectional signal link with the heat generating unit and the unloading unit.

10. The system according to claim 1, wherein the power generation unit is at least one of a photovoltaic unit, a wind farm and a hydroelectric power station.

11. The system according to claim 1, wherein the hydrogen production unit is a solid oxide electrolysis cell, wherein the solid oxide electrolysis cell is connected with the heat storage unit in order to absorb water vapor.

12. The system according to claim 1, wherein the hydrogen is chemically bound with the carrier medium in the loading unit.

13. The system according to claim 5, wherein the hydrogen production unit is an electrolyzer.

14. The system according to claim 5, further comprising: a loading unit for loading the carrier medium with the hydrogen produced in the hydrogen production unit.

15. The system according to claim 1, wherein the hydrogen is bound by physisorption with the carrier medium in the loading unit.

16. A system for releasing energy in a form of hydrogen, the system comprising: an unloading unit for unloading hydrogen from a loaded carrier medium; a heat generation unit for generating heat; a heat storage unit for storing the heat generated by the heat generation unit, wherein the heat storage unit is connected with the unloading unit in order to supply heat; and a control unit comprising a bidirectional signal link with the heat generation unit and the unloading unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic diagram of the system for storing energy according to the invention in accordance with a first embodiment example;

(3) FIG. 2 is a schematic diagram corresponding to FIG. 1 of a system for storing energy in accordance with a second embodiment example; and

(4) FIG. 3 is a schematic diagram corresponding to FIG. 1 of a system for storing energy in accordance with a third embodiment example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) Referring to the drawings in particular, the system for storing energy schematically illustrated in FIG. 1 and designated 1 as a whole comprises a power generation unit 2 in the form of a photovoltaic system. Power generation unit 2 is capable of using energy supplied by renewable energy sources 3 to generate electric power. Energy sources 3 represent renewable, in particular, erratic energy forms. In addition to the photovoltaic unit, a wind farm and/or a hydroelectric power station come into question as power generation unit 2.

(6) The direct energy effect from renewable energy source 3 on power generation unit 2 and a heat generation unit 4 is symbolically shown by an arrow 5. Heat generation unit 4 has a liquid heat carrier, which is heated by energy effect 5, in particular by direct solar radiation. Heat generation unit 4 is connected via a pipe 6 to a heat storage unit 7. Pipe 6 is capable of conveying the heat carrier. Pipe 6 is designed in particular as a so-called heat pipe. Such a heat pipe is a heat transmitter, in which a high heat flow density is made possible by using evaporation heat from the heat carrier. This means that with a smaller cross sectional area of pipe 6, large quantities of heat can be transported from heat generation unit 4 to heat storage unit 7. Effective and reduced loss heat transport is thereby possible.

(7) The heat storage unit is designed in particular as a salt store, which can be heated, for example, to a temperature of about 500 C.

(8) Power generation unit 2 is connected via a power cable 8 to heat generation unit 4. This makes it possible to deliver energy in the form of electric power from power generation unit 2 to heat generation unit 4.

(9) A further power cable 9 is provided to connect power generation unit 2 to a hydrogen production unit 10. The hydrogen production unit is designed as an electrolyzer. Electrolyzer 10 is connected via a pipe 11 to a water store 12. Water store 12 can represent a storage container or a connection to a public water supply. Water from water store 12 can be delivered to hydrogen production unit 10 via pipe 11. Hydrogen, produced in gaseous form as H.sub.2 in hydrogen production unit 10, can be delivered via a pipe 13 to a loading unit 14 of a hydrogen storage device 15. A pipe 16 is furthermore coupled to hydrogen production unit 10 for connection to an oxygen consumer 17. It is also possible not to provide oxygen consumer 17, and directly to emit oxygen into the environment through pipe 16.

(10) Hydrogen storage device 15 is used to store hydrogen and comprises loading unit 14 for loading a carrier medium with the hydrogen that has been produced in hydrogen production unit 10. According to the embodiment example shown, a liquid carrier medium comprising the dibenzyltoluene/perhydro-dibenzyltoluene system as disclosed by Bruckner and Colleagues, ChemSusChem, 2013, DOI: 10.1002/cssc.201300426 serves as the carrier medium. Hydrogen storage device 15 further comprises a carrier medium storage unit 18 for storing the carrier medium loaded in the loading unit. Hydrogen storage device 15 further comprises an unloading unit 19 for unloading the hydrogen from the loaded carrier medium and a carrier medium temporary storage unit 20 for storing the unloaded carrier medium. Loading unit 14, carrier medium storage unit 18, unloading unit 19 and carrier medium temporary storage unit 20 are respectively connected together by pipes 21. In this case, these can be conventional pipes such as can also be used to convey diesel fuel or heating oil. The carrier medium can circulate through pipes 21 in a circulation direction 22 in the hydrogen storage device.

(11) Unloading unit 19 is connected to heat storage unit 7 via a pipe 23. Heated heat carrier, therefore heat, can be transferred directly through pipe 23 from heat storage unit 7 to unloading unit 19. Unloading unit 19 is connected to a hydrogen oxidation unit 25 via a pipe 24. According to the shown embodiment example, the hydrogen oxidation unit is designed as a PEM fuel cell. Hydrogen oxidation unit 25 is connected to an oxygen source and/or to an air source 26. Hydrogen oxidation unit 25 is furthermore connected to a power supply network 28 via a power cable 27. A single power consumer can also be provided in place of power supply network 28. Power supply network 28 serves to supply several, in particular a plurality of up to 1,000 or 10,000 or more single power consumers. The power supply network can for example be a local power supply network, used to supply power to an industrial estate with one or more industrial companies and/or one or more private households. Power supply network 28 can also be part of the public power supply network. It is therefore possible for electric power that has been generated in hydrogen oxidation unit 25 to be delivered via power cable 27 and power supply network 28.

(12) System 1 furthermore comprises a control unit for controlling the operation of system 1. Control unit 29 has in particular a birectional signal link respectively with heat storage unit 7 and unloading unit 19. It is therefore possible for the control unit to record the thermal loading state of heat storage unit 7 on one hand and the current process parameters in unloading unit 19 on the other. The control unit thus guarantees that, for example when unloading is to take place, heat from heat storage unit 7 is supplied via pipe 23 to unloading unit 19. In the event that a heat requirement exists for unloading, and a thermal loading state would not be sufficient in heat storage unit 7, further thermal loading can also be initiated through control unit 29, wherein for example power generation unit 2 enables electric power via power cable 8 for electric heating of the heat carrier in heat generation unit 4. To do this, control unit 29 also has a bidirectional signal link with heat generation unit 4 and with power generation unit 2.

(13) The method according to the invention for storing energy is described in more detail below on the basis of the functioning of system 1. The sun as a renewable energy source 3 emits solar radiation, which can be used as an energy effect 5 through a photovoltaic system as power generation unit 2 for generating power. At the same time, the solar radiation as energy effect 5 can also be used to heat a, in particular liquid, heat carrier in heat generation unit 4. If energy effect 5 due to solar radiation would not be sufficient or would not lead to any desired heating of the heat carrier in the time scheduled for this, electric power can additionally be supplied via power cable 8 from power generation unit 2 to heat generation unit 4. Heating the heat carrier, which is also described as thermal loading, therefore takes place due to energy effect 5 through renewable energy and/or electric power that has been generated in particular from renewable energy.

(14) The heated heat carrier is conveyed via line 6, which is in particular a pipe, to heat storage unit 7, where it is stored. The electric power generated in power generation unit 2 is supplied via power cable 9 to hydrogen production unit 10. Water from water store 12 is furthermore supplied via pipe 11 to hydrogen production unit 10. The water in hydrogen production unit 10 is separated by electrolysis into hydrogen and oxygen. The oxygen is supplied via pipe 16 to oxygen consumer 17. The hydrogen is supplied via pipe 13 to loading unit 14 of the hydrogen storage device 15. Unloaded carrier medium in loading unit 14 is provided in the form of dibenzyltoluene. Hydrogenation into perhydro-dibenzyltoluene takes place due to the supply of hydrogen. The carrier medium is now in a loaded state. The loaded carrier medium is conveyed from loading unit 14 via pipe 21 to carrier medium storage unit 18 and can be stored there if required. The loaded carrier medium is conveyed from carrier medium storage unit 18 via pipe 21 to unloading unit 19. Unloading of the perhydro-dibenzyltoluene takes place in unloading unit 19, wherein hydrogen is released from the carrier medium. Heat is needed to release the hydrogen, and is supplied to unloading unit 19 from heat storage unit 7 via pipe 23. The carrier medium unloaded in the unloading unit, which is available following dehydrogenation as dibenzyltoluene, is supplied via pipe 21 to carrier medium temporary storage unit 20. The carrier medium in the unloaded state in carrier medium temporary storage unit 20 is temporarily stored until a need for carrier medium exists in loading unit 14. The carrier medium is then conveyed from carrier medium temporary storage unit 20 via pipe 21 to loading unit 14.

(15) The hydrogen released in unloading unit 19 is supplied to hydrogen oxidation unit 25 via pipe 24 and is combined with oxygen in a pure form or with atmospheric oxygen coming from oxygen source 26. This results in electric power, which is supplied via power cable 27 to power supply network 28. Water forms at the same time, and is discharged to a water store 30.

(16) A second embodiment example of the invention is described below with reference to FIG. 2. Constructively identical parts are given the same reference characters as for the first embodiment example, to whose description reference is hereby made. Constructively different, but functionally similar parts are given the same reference characters followed by an a.

(17) System 1a corresponds essentially to system 1 according to the first embodiment example. The main difference is the design of hydrogen production unit 10a, which is a SOEC according to the embodiment example shown. The SOEC enables the electrolysis of water vapor, which is supplied from heat storage unit 7a via an additional pipe 31. The energy needed to produce hydrogen is reduced by the fact that water vapor is already supplied to the SOEC. In particular, electrical energy for evaporating the water is reduced or not needed at all. The use of heat storage unit 7a combined with SOEC 10a is therefore particularly advantageous. Heat storage unit 7a according to the second embodiment example is characterized in that water vapor is released during thermal loading. This already released water vapor can now be used directly for electrolysis in SOEC 10a. During thermal unloading of heat storage unit 7a, water vapor coming in particular directly from hydrogen oxidation unit 25 can be absorbed, with hydrogen oxidation unit 25 being connected directly to heat storage unit 7a via a further pipe 32. This means that heat storage unit 7a serves at the same time as a water storage unit.

(18) The functioning of system 1a according to the second embodiment example corresponds to that of the first embodiment example. During an energy-rich period, an energy quantity of 10 kWh of electrical energy is supplied to SOEC 10a from power generation unit 2 via power cable 9. This energy quantity is used in SOEC 4 to produce hydrogen with an efficiency of 80%. This improved efficiency results from the use of water in the vapor state from heat storage unit 7a. The quantity of hydrogen produced is used in loading unit 14 to hydrogenate dibenzyltoluene to perhydro-dibenzyltoluene, whereby the hydrogenation efficiency is 98%. This means that from the original quantity of electrical energy used, a quantity of hydrogen in a storable, liquid state is bound in the hydrogen storage device, whereby this quantity corresponds to a heat energy of about 7.84 kWh. The heat from heat storage unit 7a is used to release all of the hydrogen in hydrogen storage device 15, so that the entire quantity of released gaseous hydrogen can be converted to heat energy amounting to 7.84 kWh. This hydrogen is streamed into hydrogen oxidation unit 25 in the form of the PEM fuel cell with an efficiency of 55%. This results in an electrical energy quantity of 4.31 kWh. The power-to-power efficiency therefore amounts to 43.1%. Compared with a comparison arrangement with a power-to-power efficiency of 25%, system 1a according to the invention has a power-to-power efficiency increase of about 73%.

(19) FIG. 3 shows the carrier medium storage unit 18 is built into the loading unit 14.

(20) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.