Electrolyzer

Electrical load for the electrolyzer.

blockType: AcausalElectricPowerSystems.Sources.Electrolyzer

Path in the library:

/Physical Modeling/Electrical/Sources/Electrolyzer

Description

Block Electrolyzer It represents an electrical load connected to an electrolyzer. The electrolyzer consists of an anode and a cathode separated by an electrolyte. The unit calculates the amount of hydrogen produced based on the electrical energy provided and the temperature of the water in the tank.

In polymer electrolyte membrane (PEM) electrolysis cells, these chemical reactions determine the anodic and cathodic transformations.:

The electrolyzer consists of several sequentially connected individual cells-electrolyzers. Use the Assumption pH parameter to model the dependence on or with a permanent .

The equations

Block Electrolyzer calculates electrical power using:

where — tension, eh — full resistance. Total resistance, , is defined as:

where

— external resistance;
— this value is a resistive term derived from the cross-sectional area of the hole , the distance between the anode and the cathode and the electrical resistivity of the solution .

The molar energy stored in the electrical load provides the process of water electrolysis and is calculated using this equation:

The electrolyzer requires a minimum amount of energy to perform electrolysis.:

where

— enthalpy of water;
— entropy of the reaction;
— water temperature;
— reference temperature.

If there is not enough electrical energy to dissociate water, the electrolyzer does not produce hydrogen. Therefore, in the block Electrolyzer The molar velocity of an electron is calculated, , and the molar velocity of hydrogen, :

where

— Avogadro’s constant;
— the energy of the electron;
— number of cells;
— temperature-dependent electrolysis efficiency.

The current flowing through the electrolyzer tank is calculated as:

where — Faraday’s constant.

Block Electrolyzer calculates the mass fractions of water consumed and hydrogen produced using these equations:

where — the molar mass of water, and — molar mass of hydrogen.

To calculate water in the tank, the unit uses

where

captures the hydrons floating in the solution ( );
— the number of moles of water;
— volume;
— the density of the water in the tank.

The residual protons in the solution inside the electrolyzer naturally increase over time. and the electrical conductivity of the water in the tank. An increase in electrical conductivity leads to the appearance of runaway electrons. To prevent this phenomenon, it is necessary to purify the water in the tank by removing the entire volume from it and filling it with clean water.

Variables

Use the Initial Targets parameter group to set the priority and initial target values for the block parameter variables before modeling. For more information, see Configuring physical blocks using target values.

Ports

Conserving

# + — positive
electricity

Details

A non-directional port connected to the anode of the electrolyzer tank.

Program usage name

p

# – — negative
electricity

Details

A non-directional port connected to the cathode of the electrolyzer tank.

Program usage name

n

Input

# purge — purge entrance
scalar

Details

The input port associated with the purge is dimensionless. This signal allows you to replace the water in the tank.

Data types	`Float64`
Complex numbers support	No

# vol — volume of water, m3^
scalar

Details

The input port is connected to the volume of water in the electrolyzer tank, in m³.

Data types	`Float64`
Complex numbers support	No

# T — water temperature, K
scalar

Details

The input port related to the water temperature is in K.

Data types	`Float64`
Complex numbers support	No

Output

# volPurging — volume of purified water, m3^
scalar

Details

The outlet port associated with the volume of water used for purging, in m3^.

Data types	`Float64`
Complex numbers support	No

# pH — pH of water
scalar

Details

The output port associated with water in the electrolyzer tank, dimensionless value.

Data types	`Float64`
Complex numbers support	No

# mdotH2 — mass consumption of hydrogen, g/s
scalar

Details

The output port associated with the mass flow rate of hydrogen, in g/s.

Data types	`Float64`
Complex numbers support	No

# mdotH2O — mass consumption of consumed water, g/s
scalar

Details

The outlet port associated with the mass flow of consumed water, in g/s.

Data types	`Float64`
Complex numbers support	No

Parameters

Main

# Assumption pH — permanent or dynamic pH
Constant | Dynamic

Details

Specify whether it is permanent or dynamic in the electrolyzer tank.

Values	`Constant` \| `Dynamic`
Default value	`Constant`
Program usage name	`pH_model`
Evaluatable	No

# Resistance — external resistance
Ohm | mOhm | kOhm | MOhm | GOhm

Details

The amount of external resistance.

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`10.0 Ohm`
Program usage name	`R_external`
Evaluatable	Yes

# Cross-sectional transport area — the cross-sectional area of the hole
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The area of the cross-section perpendicular to the vector connecting the anode and cathode. Positively charged ions move through this region from the anode to the cathode, where they are reduced and hydrogen is formed.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.04 m^2`
Program usage name	`area`
Evaluatable	Yes

# Distance anode-cathode — the distance between the anode and the cathode
m | um | mm | cm | km | in | ft | yd | mi | nmi

Details

The distance between the anode and the cathode immersed in an electrolytic solution.

Units	`m` \| `um` \| `mm` \| `cm` \| `km` \| `in` \| `ft` \| `yd` \| `mi` \| `nmi`
Default value	`0.01 m`
Program usage name	`distance`
Evaluatable	Yes

# Number of cells — number of cells

Details

The number of cells in the electrolyzer.

Default value	`50`
Program usage name	`cell_count`
Evaluatable	Yes

# Initial pH — initial pH

Details

Initial value water in the tank.

Default value	`0.0`
Program usage name	`pH_start`
Evaluatable	Yes

# Constant pH — permanent pH

Details

Constant value water in the tank.

Dependencies

To use this parameter, set the Assumption pH parameter to Constant.

Default value	`6.0`
Program usage name	`pH_const`
Evaluatable	Yes

# pH vector, pH_vec — The pH vector

Details

Vector of values . This parameter must have the same number of elements as the value vector of the parameter Electrical resistivity vector, rho_vec.

Dependencies

To use this parameter, set the Assumption pH parameter to Dynamic.

Default value	`[5.0, 5.5, 6.0, 6.5, 7.0]`
Program usage name	`pH_vector`
Evaluatable	Yes

# Electrical resistivity vector, rho_vec — vector of electrical resistance values
m/S | m/mS | m/nS | m/uS | MOhm*cm

Details

A vector of electrical resistance values. This parameter must have the same number of elements as the vector of parameter values pH vector, pH_vec.

Dependencies

To use this parameter, set the Assumption pH parameter to Dynamic.

Units	`m/S` \| `m/mS` \| `m/nS` \| `m/uS` \| `MOhm*cm`
Default value	`[0.2, 0.75, 2.5, 8.0, 18.2] MOhm*cm`
Program usage name	`resistivity_vector`
Evaluatable	Yes

Details

Temperature vector for determining the efficiency of electrolysis. This parameter must have the same number of elements as the parameter Electrolysis efficiency vector, efficiency(T).

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`[273.0, 298.0, 323.0, 348.0, 373.0] K`
Program usage name	`T_efficiency_vector`
Evaluatable	Yes

# Electrolysis efficiency vector, efficiency(T) — the efficiency vector of electrolysis

Details

The vector of electrolysis efficiency values. This parameter must have the same number of elements as the Temperature vector for efficiency, T_vec parameter.

Default value	`ones(5)`
Program usage name	`efficiency_vector`
Evaluatable	Yes