# 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) at less than 55°C (depending on the room temperature). 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 or the dryer itself does not have any sensors to measure the amounts of oxygen or water contamination. To produce a highly purified hydrogen right after the start-up, the electrolyser purges the first few litres of hydrogen via the H₂ vent line.

# 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. A solenoid valve controls the internal working pressure of the electrolyser to at least 29 barg. During operation, the pressure on the electrolyser hydrogen output increases slowly until the tank is filled and the electrolyser enters a “standby - max pressure” state, which is 35 barg by default. This value can be freely set by the operator between 0-35 barg, so if the attached tank can only safely hold up to 7 barg, it is possible to set a reduced electrolyser stop pressure of 7 barg or less. 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 uses about 20NL for each ramp down and once a day if it is running continuously.

The dryer uses 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 vent/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 at less than 55°C (depending on the room temperature). As it is not meant for further usage, there might be small amounts of H₂ and traces of KOH/K₂CO₃. Normal H₂ concentration at the oxygen vent is under 3%, in the production range 60%÷100%, up to 30barg (at the beginning of life). In transient conditions (such as ramp-up and ramp-down) and in the event of stack failure, a flammable mixture shall be expected and managed accordingly (venting to a safe area without ignition sources along/around the vent system). 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.

# What type of water trap is suitable for the O₂ vent line? Can I use the same type of water trap for the H₂ vent line as well?

Using water traps is recommended to avoid any blockage of the outlet pipes: One for the O₂ vent line and an additional one for the H₂ vent line. We recommend float type water traps which have an automatic drain system. Make sure that both water traps are compatible with KOH

# Can the oxygen be used?

Theoretically yes, but it is neither pressurised (<0,5 barg) nor purified. If it shall be used anyway, it is the operator’s responsibility that the pressure never falls below 0 barg (normal pressure) or exceeds 0,5 barg as this will lead to errors and may damage the device.

# 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

# Is there a P&ID (Piping & Instrumentation Diagram) to see the interfaces of the electrolyser and the dryer and how to connect it to other components?

Yes, the P&ID can be found here and in the owner’s manual of the electrolyser. The H₂O In can be connected to the WTM (Water Tank Module) while the H2 Out can be connected to the Dryer.

EL40 Simplified PID

The P&ID for the DR21 can be found here:

DRY21 Simplified PID

# 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. Empty the devices completely, when not used for several days. Please contact the Enapter customer support team if the devices will be stored for more than one month. Make sure to follow the operation temperature requirements before switching it on to avoid damages.

# Can I mount the devices in an inclined position?

The devices must be mounted in a horizontal position and as described in the product documentation. However, very small inclines up to 10° does not negatively affect the functionality or performance of Enapter devices. Please check the product manual for further information.

# Can I mount the devices in a corrosive environment e.g. near the sea or in very humid environments?

Corrosive environments will mean a decreased lifetime of the devices. Therefore, it is always recommended to keep them in a room or container with controlled humidity and temperatures if the requirements cannot be fulfilled otherwise.

# What is the best possibility to stack Enapter’s electrolysers and other products like the dryer and the water tank module?

Electrolysers, dryers and water tank modules can be stacked in 19” cabinets as they all have the same width and similar depths. Several cabinets can be combined to produce even higher amounts of hydrogen.

# 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 10-20 seconds. This allows 30 electrolysers to be refilled at the same time if the water in the WT is accordingly refilled. While the WT can supply even more electrolysers in one stacked system, for redundancy purposes it is suggested not to supply more than 30 electrolysers. (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 barg, 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.

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

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

# How does the water quality affect the stack degradation and the efficiency of the system?

Deionized water has a low conductivity because most mineral ions have been removed. Using non purified water will allow ions to get stuck in the stack membrane with negative effects on the stack lifetime. The stack performance can also be affected over time due to constant impurities passing through.

# Does switching on and off the electrolyser affect the overall lifetime?

As with all electrochemical devices, our AEM electrolyser stack’s lifetime is shortened with frequent start/stops. With increasing experience in the field and operational data, we can now recommend our customers to limit the electrolyser’s operative cycles to a maximum of five on/off cycles per day, and one on/off cycle per hour. This helps to ensure the longevity of the electrolyser.

The electrolyser works most efficiently and is most durable when operating continuously. However, our modular design and the Enapter Energy Management System are perfectly suited to accommodate for changing renewable energy supply or fluctuating demand. Individual ELs can be ramped from 60-100%, and the combination of many ELs will allow you to achieve any flowrate needed. If hydrogen demand is intermittent during the day, the addition of an appropriately sized buffer tank can minimise on/off cycles of the electrolyser.

# 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.