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US-20260125807-A1 - ELECTROLYZER SYSTEM INCLUDING A HEAT PUMP AND METHOD OF OPERATING THEREOF

US20260125807A1US 20260125807 A1US20260125807 A1US 20260125807A1US-20260125807-A1

Abstract

An electrolyzer system includes stacks of electrolyzer cells configured receive steam and air, and output a hydrogen product stream and an oxygen exhaust stream, and a first heat pump configured to extract heat from the oxygen exhaust stream to generate a first portion of the steam provided to the stacks.

Inventors

  • Ravi Prasher
  • K.R. Sridhar
  • Michael Petrucha
  • David Weingaertner

Assignees

  • BLOOM ENERGY CORPORATION

Dates

Publication Date
20260507
Application Date
20260105

Claims (20)

  1. 1 . An electrolyzer system, comprising: stacks of electrolyzer cells configured receive steam and air, and output a hydrogen product stream and an oxygen exhaust stream; and a first heat pump configured to extract heat from the oxygen exhaust stream to generate a first portion of the steam provided to the stacks.
  2. 2 . The electrolyzer system of claim 1 , further comprising a heat exchanger configured to extract heat from the oxygen exhaust stream to generate a second portion of the steam provided to the stacks.
  3. 3 . The electrolyzer system of claim 2 , further comprising: a steam conduit fluidly connected to a steam outlet of the heat exchanger and to a steam inlet of the stacks, and configured to provide the steam to the stacks; and an exhaust conduit fluidly connecting an oxygen outlet of the stacks in series to oxygen inlets of the heat exchanger and the first heat pump, and configured to receive the oxygen exhaust stream from the stacks.
  4. 4 . The electrolyzer system of claim 3 , further comprising a water conduit fluidly connecting a water source to an inlet of the first heat pump.
  5. 5 . The electrolyzer system of claim 4 , further comprising a first connecting conduit fluidly connecting a steam outlet of the first heat pump to a water inlet of the heat exchanger, wherein heat exchanger is configured to receive liquid water and the first portion of the steam from the first heat pump via the first connecting conduit and to generate the second portion of the steam provided to the stacks.
  6. 6 . The electrolyzer system of claim 4 , wherein the water conduit fluidly connects the water source to the inlet of the first heat pump and to an inlet of the heat exchanger in parallel.
  7. 7 . The electrolyzer system of claim 3 , further comprising: a hydrogen processor configured to compress the hydrogen product stream; a product conduit fluidly connecting the hydrogen processor to the stacks, and configured to transfer the hydrogen product stream from the stacks to the hydrogen processor; and a steam generator configured to generate a third portion of the steam provided to the steam conduit.
  8. 8 . The electrolyzer system of claim 1 , wherein the stacks comprise solid oxide electrolyzer cell stacks.
  9. 9 . The electrolyzer system of claim 1 , further comprising a plurality of electrolyzer modules that each comprise a hotbox housing at least one of the stacks.
  10. 10 . The electrolyzer system of claim 1 , wherein the first heat pump comprises: a compressor configured to compress a working fluid; a condenser configured to condense the compressed working fluid; an expansion value configured to lower a pressure of the condensed working fluid; and an evaporator configured to evaporate the lowered pressure working fluid.
  11. 11 . A method of operating an electrolyzer system, comprising: providing steam and air to stacks of electrolyzer cells to generate a hydrogen product steam and an oxygen exhaust stream; providing the oxygen exhaust stream and liquid water to a first heat pump; and extracting heat from the oxygen exhaust stream in the first heat pump to generate a first portion of the steam provided to the stacks.
  12. 12 . The method of claim 11 , further comprising: providing the oxygen exhaust stream to a heat exchanger; and extracting heat from the oxygen exhaust stream in the heat exchanger to generate a second portion of the steam provided to the stacks, wherein the step of providing the oxygen exhaust stream to the first heat pump comprises providing the oxygen exhaust stream from the heat exchanger to the first heat pump.
  13. 13 . The method of claim 12 , further comprising: providing the oxygen exhaust stream from the first heat pump to a second heat pump; providing the liquid water to the second heat pump; preheating the liquid water in the second heat pump, wherein the step of providing the liquid water to the first heat pump comprises providing the preheated liquid water from the second heat pump to the first heat pump; and providing a portion of the preheated liquid water and the first portion of the steam from the first heat pump to the heat exchanger.
  14. 14 . The method of claim 13 , wherein: the oxygen exhaust stream provided to the heat exchanger has a temperature ranging from about 200° C. to about 250° C.; the oxygen exhaust stream provided from the heat exchanger to the first heat pump has a temperature ranging from about 110° C. to about 130° C.; and the oxygen exhaust stream provided from the first heat pump to the second heat pump has a temperature ranging from about 70° C. to about 90° C.
  15. 15 . The method of claim 14 , wherein: the liquid water provided to the second heat pump has a temperature below 80° C.; the preheated liquid water provided from the second heat pump to the first heat pump has a temperature ranging from about 80° C. to about 100° C.; and the preheated liquid water and the first portion of the steam provided from the first heat pump to the heat exchanger has a temperature ranging from about 110° C. to about 130° C.
  16. 16 . The method of claim 14 , further comprising providing the liquid water to the heat exchanger to generate the second portion of the steam in parallel with the providing the liquid water to first heat pump.
  17. 17 . The method of claim 14 , further comprising providing the liquid water to a steam generator to generate a third portion of the steam in parallel with the providing the liquid water to first heat pump.
  18. 18 . The method of claim 18 , wherein more of the liquid water is provided to the first heat pump during a steady state operating mode of the stacks than during a startup mode of the stacks.
  19. 19 . The method of claim 11 , wherein: the electrolyzer system further comprises a plurality of electrolyzer modules that each comprise a hotbox housing at least one of the stacks; and the stacks comprise solid oxide electrolyzer cell stacks.
  20. 20 . The method of claim 19 , wherein: the steam is provided from the first heat pump to the plurality of the electrolyzer modules; and the oxygen exhaust stream is provided from the plurality of the electrolyzer modules to the first heat pump.

Description

FIELD The present disclosure is directed to electrolyzer cell systems including at least one heat pump for thermal energy recovery and method of operating thereof. BACKGROUND In a solid oxide electrolyzer cell (SOEC), a cathode electrode is separated from an anode electrode by a solid oxide electrolyte. When a SOEC is used to produce hydrogen through electrolysis, a positive potential is applied to the air side of the SOEC and oxygen ions are transported from the fuel (e.g., steam) side to the air side. Throughout this specification, the SOEC anode will be referred to as the air electrode, and the SOEC cathode will be referred to as the fuel electrode. During SOEC operation, water (e.g., steam) in the fuel stream is reduced (H2O+2e−→O2−+H2) to form H2 gas and O2− ions, the O2− ions are transported through the solid electrolyte, and then oxidized (e.g., by an air inlet stream) on the air side (O2− to O2) to produce molecular oxygen (e.g., oxygen enriched air). SUMMARY In various embodiments, an electrolyzer system includes stacks of electrolyzer cells configured receive steam and air, and output a hydrogen product stream and an oxygen exhaust stream. The electrolyzer system also includes a first heat pump configured to extract heat from the oxygen exhaust stream to generate a first portion of the steam provided to the stacks. In various embodiments, a method of operating an electrolyzer system comprises providing steam and air to stacks of electrolyzer cells to generate a hydrogen product steam and an oxygen exhaust stream; providing the oxygen exhaust stream and liquid water to a first heat pump; and extracting heat from the oxygen exhaust stream in the first heat pump to generate a first portion of the steam provided to the stacks. FIGURES FIG. 1A is a perspective view of a solid oxide electrolyzer cell (SOEC) stack, and FIG. 1B is a side cross-sectional view of a portion of the stack of FIG. 1A. FIG. 2A is a schematic view of an electrolyzer system, according to various embodiments of the present disclosure, FIG. 2B is a schematic view showing an electrolyzer module of the system of FIG. 2A, and FIG. 2C is a schematic view of a heat pump that may be included in the electrolyzer system of FIG. 2A. FIG. 3 is a schematic view of an electrolyzer system, according to an alternative embodiment of the present disclosure. DETAILED DESCRIPTION The various embodiments will be described in detail with reference to the accompanying drawings. The drawings are not necessarily to scale and are intended to illustrate various features of the invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes and are not intended to limit the scope of the invention or the claims. Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about” or “substantially” it will be understood that the particular value forms another aspect. In some embodiments, a value of “about X” may include values of +/−1% X. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. FIG. 1A is a perspective view of an electrolyzer cell stack 100, such as a solid oxide electrolyzer cell (SOEC) stack, and FIG. 1B is a side cross-sectional view of a portion of the stack 100 of FIG. 1A. Referring to FIGS. 1A and 1B, the stack 100 includes multiple electrolyzer cells 1 that are separated by interconnects 10, which may also be referred to as gas flow separator plates or bipolar plates. Each electrolyzer cell 1 includes an air electrode 3, an electrolyte 5, such as a solid oxide electrolyte for a SOEC, and a fuel electrode 7. The stack 100 also includes internal fuel riser channels 22. Various materials may be used for the air electrode 3, electrolyte 5, and fuel electrode 7. For example, the air electrode 3 may comprise an electrically conductive material, such as an electrically conductive perovskite material, such as lanthanum strontium manganite (LSM). Other conductive perovskites, such as LSCo, etc., or metals, such as Pt, may also be used. The electrolyte 5 may comprise a stabilized zirconia, such as scandia stabilized zirconia (SSZ) or yttria stabilized zirconia (YSZ), yttria-ceria-stabilized zirconia (YCSZ), ytterbia-ceria-scandia-stabilized zirconia (YbCSSZ) or blends thereof. In YbCSSZ, scandia may be present in an amount equal to 9 to 11 mol %, such as 10 mol %, ceria may present in amount greater than 0 and equal to or less than 3 mol %, for example 0.5 mol % to 2.5 mol %, such as 1 mol %, and ytterbia may be present in an amount greate