From Cell to System
Explore the equipment that turns a stack into a working hydrogen-production system.
Ready — press Start.
Process flow diagram (PFD). Equipment tags: P = pump; V = vessel; E = exchanger; D = dryer; K = compressor; EL = electrolyser; PS = power supply; WT = water treatment package. These tag prefixes are the convention used in this lesson.
● Water / liquid · ● Hydrogen · ● Oxygen · ● Electrical power · ● Warm coolant · ● Cooled coolant
Understand cell → stack → system
The flowsheet is conceptual, not a universal plant design. Gas circuits are separate; the drawing omits technology-specific valves, instruments, safeguards and treatment stages.
Are we considering only the electrolyser stack?
Or are we considering the complete system, including water treatment, pumps, cooling, gas separation and compression?
The chosen system boundary therefore affects quantities such as total electrical consumption, efficiency and cost.
Energy does more than drive the reaction
The stack uses electrical energy. Power electronics, pumps, cooling and optional compression can also consume energy. Heat may be removed, recovered or supplied, depending on the technology and operating point.
Balance of plant (BoP): supporting equipment outside the stack. System boundary: the equipment and processes included in a reported result. AC / DC: alternating / direct current. Conditioning: preparing hydrogen to meet its delivery specification.
Cell, stack or balance of plant?
Build a low-temperature electrolyser system
Select the core equipment for this teaching example. Compression depends on the delivery pressure.