# Technical Integration

# Outputs

# Hydrogen Production

# What is the purity of hydrogen at the outlet?

The hydrogen outlet contains more than 99,9% pure hydrogen (H₂). There are small amounts of water (~1000ppm H₂O) and even smaller amounts of oxygen (O₂). Those amounts can be further decreased with a hydrogen dryer to reach up to 99,999% pure hydrogen. Please see the datasheet for more information. The electrolyser itself does not have any sensors to measure the amounts of oxygen or water contamination.

# Is the hydrogen pressure at the outlet constant?

Yes. The hydrogen is produced at adjustable constant pressure and will flow into an external tank or pipeline until the pressure at the outlet reaches the threshold. Please see the datasheet for details.

# Is it possible to fill a tank up to 7 bar only with Enapter’s electrolyser. Can this be done safely?

Yes. The internal working pressure of the electrolyser is always at least 29 bar when it is operating and can increase to a maximum allowable pressure of 35 bar. The internal pressure is controlled by a pressure regulating valve, and it is usually independent of the hydrogen output pressure. The pressure on the electrolyser hydrogen output depends on the storage volume and the amount of hydrogen produced. The maximum electrolyser outlet pressure, which determines the pressure where the electrolyser stops working and enters a “standby - max pressure” state, is 35 bar by default. This value can be freely set by the operator between 0-35 bar, so if the attached tank can only safely hold up to 7 bar, it is possible to set a reduced electrolyser stop pressure of 7 bar. Important note: To ensure the safety of your system, you must install appropriate overpressure protection devices on your hydrogen storage system connected to the electrolyser outlet.

# Is it possible to produce oxyhydrogen gas?

Hydrogen and oxygen should always be kept separately to avoid explosions and fire! To avoid a dangerous situation, you should never mix the oxygen and hydrogen outputs from the electrolyser. Please always follow the instructions in the manual and apply safe engineering practices.

# How much hydrogen is consumed by the electrolyser and the dryer which cannot be stored?

The electrolyser purges about 20NL/h for each ramp down and once a day if it is running continuously. The dryer purges about 15NL/h of hydrogen to drag away the humidity. These amounts are not part of the produced amount at the hydrogen outlet, so they do not lower the production rate.

# What is the H₂ purge outlet for?

The purge line is used during ramp ups and ramp downs as well as every 12h during operation to remove water inside the electrolyser and increase the quality of the hydrogen at the hydrogen outlet. The purge line of the dryer can be connected with the one of the electrolyser and contains the water which has been extracted during the drying process.

# Oxygen Outlet

# What are the contents of the oxygen outlet?

The oxygen outlet primarily contains oxygen (O₂) and a little amount of water steam. As it is not meant for further usage, there might be small amounts of H₂ and traces of KOH/K₂CO₂. For safety reasons, the H₂ concentration at the oxygen vent is always kept below a safe limit of 4% at around 2%. A water trap is recommended to separate the water from the oxygen at the vent outlet. Ensure that the oxygen vent and hydrogen purge line outlets are led to safe areas and not close to each other.

# Can the oxygen be used?

Theoretically yes, but it is neither pressurized (<0,5 bar) nor purified.

# Other Outlets

# Are there any other substances, gases or liquids that need to be considered?

No. There are no other substances released beside H₂, O₂, H₂O (steam) and KOH (when drained). During each purge 1-10ml of water (mostly liquid) is released. The O₂ vent line contains 250 NL/h of oxygen saturated with water vapor.

# Setup

# General

# Where can I find more information about the products?

The datasheets contain an overview of the different products. The owner’s manuals include more precise information about setting up devices, connecting them and starting the hydrogen production.

# What needs to be considered when storing an Enapter product?

Enapter products may contain small amounts of liquids when they leave Enapter. Therefore, Enapter products shall always be stored between +1°C and +45°C. Make sure to follow the operation temperature requirements before switching it on to avoid damages.

# Can I mount the electrolyser in an inclined position?

Unfortunately, the electrolyser must be mounted in a horizontal position and as described in the product documentation. Please check the product manual for further information.

# What does the red, orange, and green LED on the device mean?

A table of the meanings can be found here (opens new window).

# How can the electrolyser be started and stopped?

The electrolyser can be easily started and stopped via the Energy Management System (EMS) in standby-mode, via Modbus TCP or the front panel button. Please see the software chapter for more information.

# Does the electrolyser need an uninterrupted power supply?

No. But it is recommended to keep the power supply as stable as possible to preserve the internal components.

# Dry Contact

# How quick does the dry contact shut down the system?

An interruption at the dry contact will immediately trigger a shutdown of the electrolyser system. The electrolyser will then go into error mode, and the hydrogen production will stop. The valve at the purge line will open as well to release the internal pressure.

# Additional components and external devices

# What is the Enapter dryer? What is the technology behind it, and how can it be installed?

The Enapter dryer raises the output purity of hydrogen gas from the AEM electrolyser to >99.999% in molar fraction. It is a hybrid temperature/pressure swing adsorption system that comprises two cartridges filled with a highly adsorbent material. The system is fully integrated into the Enapter Energy Management Sytem (EMS) (opens new window) to monitor the state, temperatures, and pressures.

The dryer will be installed at the H₂ outlet of the electrolyser and extracts the water from the hydrogen stream by releasing about 15NL/h of strongly water vapor saturated hydrogen via the purge line.

# What is the Enapter Water Tank (WT)?

The water storage capacity of the Enapter WT is 35 litres. The pump of the WT offers a supply rate of up to 3.8 L/min. Depending on the length of the pipes to the electrolysers a single typical refilling can be accomplished in between 1-2 minutes. (WT2.1 data sheet (opens new window))

# Is a buffer tank needed at the hydrogen outlet?

No. A buffer tank is not needed but recommended for setups where the hydrogen outlet is not directly connected to a storage tank. In those cases, a buffer tank of 50 L per electrolyser keeps the pressure at the output stable and prevents the system from ramping up and down too often.

# Is an oxygen concentration sensor needed at the hydrogen outlet?

No. The pressure difference between the oxygen and hydrogen sides ensures that no significant oxygen concentration can arise at the hydrogen outlet.

# Is it possible to add manual regulators to change the stack current, voltage and circulation pump flow control?

These functions are automatically controlled by the electrolyser. The production rate can be set via the Energy Management System (EMS). Manual regulators are not necessary and cannot be added.

# Is a compressor needed for the electrolyser?

The electrolyser produces hydrogen gas pre-compressed at 35 bar, which is sufficient for most stationary storage projects. Only for very large amounts of hydrogen to be stored, or if hydrogen is produced for mobility (hydrogen vehicles), then a compressor is needed to reach higher pressures.

# Maintenance and Lifetime

# How is the end of lifetime of Enapter’s electrolysers defined?

Enapter has defined an end of life criteria for the electrochemical stack when an average cell voltage of 2.0V is exceeded (at nominal production rate, nominal operating temperature, and with fresh electrolyte solution). This means, roughly 15% of the stack degradation of a brand-new stack. Even after that point, the electrolyser will still be functional and can continue to produce hydrogen at a lower efficiency or production rate.

# What is the lifetime of the electrolyser and the dryer?

The expected lifetime of the electrolyser is more than 30.000h. Also, the dryer’s lifetime is at least 30.000h. Enapter expects those numbers to further increase in the future.

# Does varying the production rate of the electrolyser affect the overall lifetime?

No. Changing the production rate does not influence the lifetime.

# What maintenance is required for the AEM Electrolyser?

Almost none. The main regular maintenance needed is draining and refilling electrolyte once a year or if the electrolyte quality is degraded. The used electrolyte needs to be disposed according to the local regulations. It should be checked that the ventilation ports are free of dust and obstacles and that there are no leakages. Please see the user manual for more information.

# What maintenance is required for the dryer?

Almost none. But it should be checked that the ventilation ports are free of dust and obstacles and that there are no leakages.

# What maintenance is required for the Water Tank?

None. The Water Tank does not need any maintenance if the water inside meets the electrolyser’s purity requirements. However, it should be checked for leakages.

# How long does it take until the electrolyte (KOH solution) is used up?

The electrolyte is not used up. As the KOH is only circulating within the machine, it remains in the system and does not get diluted after several refillings. However, the electrolyte will accumulate impurities and degrade during operation and therefore needs to be exchanged once per year.

# How is it possible to detect the electrolyser’s end of life?

Once the stack end of life criteria is reached, even with fresh electrolyte and at nominal operating temperature the power supply within the electrolyser will not be able to reach the maximum production rate anymore.

A degraded electrolyte can result in a similar increase in the stack potential and can therefore be easily mistaken as a premature stack degradation. Please ensure to follow the maintenance instructions carefully to ensure longevity and performance of the electrolyser.

# How is it possible to detect the dryer’s end-of-life?

There is no simple mechanism to detect dryer end of life. When the adsorbent materials in the cartridges degrade too much, they will not be able to fully dry the hydrogen anymore, and the will water content in the output hydrogen stream will increase. This could be detected with a dew point measurement.

# Can the electrolyser, dryer, water tank and other devices be recycled?

Yes. Enapter will take back old hardware and reuse or recycle it.