# US 10,246,787 B2 · Control of a high temperature electrolyzer

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- Number: US 10,246,787 B2
- Document ID: US10246787B2
- Status: Granted
- Kind: B2
- Application number: 15/031,778
- Filed: 2014-10-22
- Published: 2016-08-25
- Granted: 2019-04-02
- Earliest claimed: 2013-10-25
- Assignees: Electricite de France
- Applicants: Electricite De France
- Inventors: Floriane Petipas; Annabelle Brisse; Chakib Bouallou
- Web page: https://patentgrep.com/patent/US10246787B2

## CPC

- C25B 15/02: Process control or regulation
- C25B 1/04: by electrolysis of water
- C25B 1/23: Carbon monoxide or syngas
- C25B 9/00: Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B 9/73: of the filter-press type
- C25B 15/023: Measuring, analysing or testing during electrolytic production
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- Y02P 20/133: Renewable energy sources, e.g. sunlight
- C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A process for controlling a high temperature electrolyzer in which the one or more stacks of cells are arranged in an enclosure pre-heated to a high temperature and thermally insulated, where the electrolyzer is connected to an electric energy source for its power supply in order to implement an electrolytic reaction and where the process includes: monitoring of the power supplied by the energy source; redirecting upstream of the electrolyzer a portion of the power supplied by the energy source in order to heat the one or more stacks of cells when the value of the power supplied becomes lower than a previously set limit value; otherwise, no redirecting. A process for production of hydrogen or syngas incorporating the above driving process, where a driving system implements the above driving process and a hydrogen production system implements the corresponding hydrogen production process.

## Claims

### Claim 1

A method for driving a high temperature electrolyzer comprising one or more stacks of cells, where the one or more stacks of cells are arranged in an enclosure pre-heated to a high temperature and thermally insulated, where the electrolyzer is connected to an electric energy source for its power supply in order to implement an electrolytic reaction and where the method comprises:
monitoring of the power supplied by the energy source;
redirecting upstream of the electrolyzer a portion of the power supplied by the energy source in order to heat the one or more stacks of cells when the value of the power supplied becomes lower than a previously set limit value;
otherwise, no redirecting,
wherein the previously set limit value is chosen as the value of the power at which thermal gradients greater in absolute value than 50° C./cm appear inside the enclosure.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the electrolyzer cells have a surface area S and the distance between the inlet of the gases and the outlet of the gases in a cell is L, the limit value Pmin per cell is chosen equal to:
P
min
=
E
⁡
(
T
min
)
·
j
⁡
(
T
min
)
·
S
;
with
⁢
:
T
min
=
T
water
-
L
·
Δ
⁢
⁢
T
2
;
E
⁡
(
T
)
=
E
N
⁡
(
T
)
+
j
⁡
(
T
)
·
ASR
;
E
N
⁡
(
T
)
=
Δ
r
⁢
G
0
⁡
(
T
)
2
·
F
+
R
·
T
2
·
F
·
ln
⁡
(
SC
/
2
1
-
SC
/
2
)
;
j
⁡
(
T
)
=
A
⁡
(
T
)
2
·
F
·
ASR
-
E
N
⁡
(
T
)
ASR
;
A
⁡
(
T
)
=
L
·
Δ
⁢
⁢
T
2
·
(
c
p
H
⁢
⁢
2
⁡
(
2
⁢
T
-
T
water
)
+
c
p
O
⁢
⁢
2
⁡
(
2
⁢
T
-
T
water
)
2
-
c
p
H
⁢
⁢
2
⁢
O
⁡
(
T
water
)
SC
)
+
Δ
r
⁢
H
⁡
(
T
)
;
where Twater is the temperature of the steam entering near the cathode; ΔT is the maximum tolerable temperature gradient;
c
p
H
2
is the thermal capacity of the hydrogen at constant pressure;
c
p
O
2
is the thermal capacity of the oxygen at constant pressure;
c
p
H
2
⁢
O
is the thermal capacity of the water at constant pressure; ΔrH is the enthalpy of reaction of the electrolysis of water; ΔrG is the free enthalpy of reaction of the electrolysis of water; SC is the rate of conversion of water into hydrogen; ASR is the resistivity of the surface of one or more stacks of cells; F is the Faraday constant; and R is the ideal gas constant.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the redirected power is obtained by iteration of the following equations until convergence by taking Pred,0=0 and P0=Psource as initial values:
P
red
,
m
+
1
=
A
⁡
(
T
min
)
·
n
.
m
⁡
(
T
min
)
-
P
m
;
with
⁢
:
n
.
m
⁡
(
T
)
=
S
2
·
F
·
(
-
E
N
⁡
(
T
)
2
·
ASR
+
P
m
S
·
ASR
+
(
E
N
⁡
(
T
)
2
·
ASR
)
2
)
;
P
m
=
P
source
-
P
red
,
m
;
with m≥0 greater than or equal to 0; m indicating the order of the iteration.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the L is the distance between the inlet and the outlet of the gases in a cell, where the steam entering from the side of the cathodes is at a temperature Twater and ΔT represents the maximum tolerable temperature gradient, then the limit value of the power below which the redirect is implemented is equal to the power for which the temperature Toutlet of the gases at the outlet of the one or more stacks is equal to:
Toutlet=Twater−ΔT·L.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the energy source is an intermittent and/or fluctuating energy source.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the energy source is a renewable energy source.

### Claim 7 (depends on 1)

The method for production of hydrogen or syngas comprising the steps of:
preheating a thermally insulated enclosure, in which the one or more stacks of a high temperature electrolyzer are arranged, to a high temperature;
supplying the electrolyzer with power from an energy source;
circulating water to the cathodes of the electrolyzer to implement an electrolytic reaction;
driving the electrolyzer according to the driving method of claim 1;
recovering near the anodes the oxygen generated by the electrolytic reaction;
recovering near the cathodes the hydrogen generated by the electrolytic reactions and possibly the carbon monoxide in the case of syngas production.

### Claim 8 (depends on 7)

The method according to claim 7, wherein the high temperature is included between 300° C. and 1000° C.

### Claim 9

A system for driving a high temperature electrolyzer comprising one or more stacks of cells arranged in an enclosure pre-heated to a high temperature and thermally insulated, where the electrolyzer is supplied by an energy source, comprising:
a heater to be connected to the energy source for supplying it with power and to be arranged near the one or more stacks of cells for heating thereof;
a switch to be arranged between the energy source and the heater for cutting or adjusting the supply thereto when the value of the power supplied becomes lower than a previously set limit value;
a controller to be connected to the energy source in order to monitor the power provided thereby and connected to the switch for the control thereof,
wherein the previously set limit value is chosen as the value of the power at which thermal gradients greater in absolute value than 50° C./cm appear inside the enclosure.

### Claim 10 (depends on 9)

The system according to claim 9, wherein the heater comprises one or more electrical resistance is arranged inside of the one or more stacks of cells or around the stacks.

### Claim 11 (depends on 9)

A system for production of hydrogen or syngas comprising:
a high temperature electrolyzer;
an energy source connected to the electrolyzer for supplying the electrolyzer with power;
a thermally insulated enclosure in which the one or more stacks of cells of the electrolyzer are arranged; and
the system for driving a high temperature electrolyzer according to claim 9 for driving the electrolyzer supplied by the energy source.