What is water specifications for Enapter AEM Electrolysers?

Detailed Water Specifications for Enapter AEM Electrolysers can be found here.

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.

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.

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.

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.

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.

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.

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

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

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.

What’s the electrode’s material and the exchange current density of the catalyst layer?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

What’s the surface, thickness, ion conductivity, water absorption and pressure resistance of the MEA?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

What’s the electrical resistance and thermal conductivity of the gas diffusion layer and the current collector and what are their materials, porosity, thickness, geometry, and diameter?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

What’s the electrical resistance and thermal conductivity, the length, width, height, geometry of the flow channels?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

What’s the structure, material, length, width, height, and geometry of the bipolar plates?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

What’s the heat transmission coefficient of the stack?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

Where can I find the pressure and temperature dependant polarisation curve?

Our stack always works at the most efficient pressure and temperature. Therefore, the polarisation curve is only dependent on the production rate. It can be found in the chapter “The electrolyser in general” above.

How many cells are within one stack?

There are 23 cells in each stack.

What’s the overall weight, dimensions (length, width, hight) an geometry of the stack?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property. But the stack looks very similar like the own visible in our marketing material.

Which membrane is used for the stack?

Enapter only uses its own developed Anion-Exchange-Membrane (AEM).

Are the stack air cooled or liquid cooled?

The stacks in the Multicore are always liquid cooled.

Can the Multicore be operated continuously if the input power is changing?

The production range can be adjusted between 3% and 105% depending on the available energy.

What is included in the Multicore? What’s the difference between the hydrogen output purity?

The Multicore contains 420 electrolysis stacks. With optional dryers, the purity raises to 99,999%. A water purification system is needed to provide purified water to the Multicore.

Do the electrolysers have built-in conductivity sensors? Can they provide measurement values of the absolute water conductivity value?

The electrolyser does not have a built-in conductivity sensor. Therefore, it is the responsibility of the operator to ensure that the water quality reaches the requirements which can be found in the datasheet. However, the Enapter Water Tank Module has a built-in conductivity sensor which shows a warning and stops the water supply to the electrolysers if the conductivity rises.

When does it make sense to not shut down the devices?

It is also possible to leave the devices in standby. Especially during colder temperatures this keeps the internal heater running if no hydrogen is produced. Please consider, that the devices are operated and stored according to the temperature ranges stated in the datasheets.

What’s the power consumption during the start up and what’s the difference between the internal hydrogen pressure and the outlet pressure?

The following diagram shows how the pressure and power consumption increases during start up until it reaches the maximum pressure at the outlet. The values can be adapted to the operator’s preferences.

This is the diagram for the 8 barg version:

Is the electrolyte that Enapter uses for its electrolysers environmental-friendly?

Enapter uses a 1% KOH solution for the electrolysis. It is a clear, soapy liquid which is easily produced by dissolving KOH pallets in purified water. The KOH can be purchased from companies which use green energy for the chemical extraction.

How green the KOH is produced and deposited depends on the manufacturing as well as the disposal management company that you chose. The disposal conditions depend on the company’s health and safety policies as well as the national and local laws and regulations.

However, Enapter electrolysers are not using noble metals which could dissolve in the electrolyte, nor high concentrated chemicals. So, the electrolyte can be disposed of in a more environmental-friendly, easier, and cheaper way compared to other technologies.

Is it possible to use Enapter’s electrolysers for heating/powering my home?

Yes. However, Enapter specializes on the AEM electrolyser and auxiliary equipment related to the hydrogen production. Enapter does not offer turnkey solutions with tanks, fuel cells, and other equipment preassembled on site. The good news is, our partners do and you can find them in this document.

The Enapter EMS, can provide overview and control of a complete hydrogen production, storage and usage system, including third-party fuel cells and other sensors/inputs/outputs.

Doing rough calculations and assuming 4 months of summer with a total exposure of 2 MWh, that would result in about 500kWh per month and about 16,6kWh per day. Each Enapter electrolyser module could run about 7 h a day, using 2,4kW each and generating 3,5 Nm³ of hydrogen gas daily (~300g).

Over the summer period, an energy content of roughly 1200 kWh could be accumulated.

Enapter’s electrolysers produce hydrogen at 35 barg, which is the maximum storage pressure which could be achieved without a compressor. A steel tank or an array of bottles with an internal volume of 12m³ to hold the 35kg would then be sufficient. A standard fuel cell for stationary applications can turn the hydrogen back into electricity.

Typical fuel cells have an electrical efficiency of around 50%. If the generated heat could be used as well, co-generation fuel cells can reach efficiencies of up to 90%.

What is the electrolytic cell rated operating temperature in degree Celsius and degree Fahrenheit?

The rated operating temperature is 55 °C / 131 °F.


1: Command Line Interface

2: Atmospheres Explosibles

How is the pressure controlled for H₂? Is it using a pressure switch and valve?

Enapter utilises a proportional relief valve to pressurise the system and several pressure transmitters to control and monitor stack and outlet pressures. A solenoid valve opens and closes to return the system to a safe state if an error occurs.

What is the electrolyser cell’s voltage and current range?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

What is the surface area of the membrane?

Unfortunately, we cannot provide this information as it is part of Enapter’s intellectual property.

Is Nitrogen used during the process?

Enapter’s electrolysers do not use Nitrogen.

What are the differences between the air-cooled and the liquid cooled electrolyser?

The air-cooled and liquid-cooled electrolyser are nearly identical devices. The only difference is in the heat exchanger subassembly, which has the primary function to maintain a stable electrolyte temperature for the electrolyser operation.


The air-cooled electrolysers use a fan to blow ambient air to keep the electrolyte at the nominal operating temperature of 55°C. Air with a maximum allowed temperature of 45 °C is taken in at the front of the device and blown out hotter at the back. The operator must ensure distances at the front and the back of the device to allow sufficient air flow.

Pros: uses ambient air, therefore easy and fast to set up

Cons: higher requirements on HVAC and installation space in small rooms or containers


The liquid-cooled electrolysers have a liquid-liquid heat exchanger and use a valve to allow/interrupt the cooling liquid flow. The liquid-cooled version of the electrolyser has minimal air flow requirements for safety purposes and to cool the electronics. Therefore the installation space for the air flow can be reduced depending on the room temperature. It has an additional cooling liquid inlet and outlet on the front panel. The operator must supply pressurized cooling liquid at the inlet, and the device will release the cooling liquid at a higher temperature from the outlet. The temperature increase depends on the supplied pressure and flow rate. The waste heat amount can be found in the datasheet.

Pros: more compact setup as air flow requirements is reduced

Pros: reduced requirements on the HVAC system for indoor installations

Cons: requires the installation of a cooling liquid circuit

Using waste heat

In both the air-cooled and liquid-cooled cases, the total waste heat energy from the electrolysis process is the same. This waste heat, while of relatively “low quality”, could potentially be used by integrators in some specific applications to increase overall efficiency of their energy systems. In most cases however, it is just released to the environment.

What are the maintenance and operational costs for an Enapter electrolyser (EL), dryer (DR) and water tank (WT)?

The electrolyser requires a yearly change of electrolyte, which can be performed by the customer in an easy 20 minutes process.

The dryer is maintenance free.

The water tank is maintenance free if in use. If water is stagnant in the tank for a longer period, it may be necessary to wash the tank before continued usage.

What are the WiFi connection requirements?

The WiFi must fulfil the following specifications:

– Connection minimum speed: 1Mbps

– Security: None, WPA or WPA2 Personal

– Routing and proxy: if proxy server to be used then it should be HTTP proxy with support of CONNECT feature

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

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

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.

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 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.

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.

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 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.

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

No. Changing the production rate does not influence the 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.

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.

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 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 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.

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))

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) 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.

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.

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.

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.

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

A table of the meanings can be found here.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

Which countermeasures are necessary to prevent the creation of an ATEX area around the electrolyser?

Technical rooms where Enapter electrolysers are installed, shall be maintained Safe (i.e. Non-hazardous) according to IEC60079-10-1, by proper ventilation systems (i. e. with adequate dilution rate). Hydrogen sensor installation is highly recommended to detect any potential leaks and immediately stop H2 production. Enapter Electrolysers are technically leak-tight by design, nevertheless acc. to IEC60079-10-1, they shall be considered a potential source of secondary release grade (i.e. not expected during normal operation of the equipment) for assessment of the ventilation.


Is the piping system in accordance with a certification?

Yes. Enapter designs all hydrogen piping in accordance with ASME B31.12. All European guidelines refer to the ASME, which are very high standards for hydrogen piping and pipelines.

Is the electrolyser ATEXcertified?

Our products are not designed to be installed in an ATEX area. The output gases are only released from the designated interfaces (H₂ outlet, O₂ vent, and H₂ purge). These have to be correctly managed during the on-site installation. It is the operators responsibility to ensure that the area where the electrolysers are installed, are maintained Safe (i.e. Non-hazardous) according to IEC60079-10-1, by proper ventilation systems (i. e. with adequate dilution rate). An appropriate safety concept must be implemented to mitigate the risks of any failures and consequences of leakages of flammable gases. Hydrogen sensor installation is highly recommended to detect any potential leaks and immediately stop H2 production.

Is the electrolyser CE certified?

The EL2.1 is CE certified.

What is Modbus TCP/IP and how can I use it to control the Enapter devices?

Modbus TCP/IP is a protocol which can be used to access registers of the electrolyser via the Ethernet port. This can be used to read statuses and sensor data as well as to write commands like start, stop, reboot. A description of all available registers can be found here.

Are there updates available for the Enapter devices?

Yes. They can be downloaded and installed via the mobile phone app or the cloud.

Can the electrolyser be managed without the Enapter mobile phone application or Cloud?

Yes. However, the most convenient and simple way to manage and monitor the electrolyser is via the Enapter Cloud or mobile phone app.

When using the Modbus TCP interface all required data and functionality for the integration with third party management software is possible. Enapter provides a full Modbus register table (here for the EL 2.1) together with samples of programming scripts in python to get started. The scripts are hosted on a github page and help to understand the flows of monitoring, control and commissioning of the device.

Can the electrolyser be switched off in case of an emergency? How long does it take to switch the electrolyser on again?

Yes, of course, in case of an emergency, the power to the electrolyser can just be cut off. When the emergency is resolved, the electrolyser can be powered on and restarted again within a few minutes.

What are the advantages of the Enapter mobile phone app?

Enapter’s mobile phone application is an interface for system integrators and end-users who want to connect their devices such as electrolysers, dryers, communication modules and extensions. The Enapter mobile phone app allows an easy and secure system setup using QR codes to manage and monitor devices all over the world. It is available for Android and iOS.

Is there a possibility to smart regulate the production?

Yes. Due to the rule based control, the system can be programmed to be as versatile as needed. In that way, weather and time depending control and other sensor driven actions can be realized by a simple CLI if-then-else logic. For an extended functionality and more complex situations, the scripting language Lua can be used. Generally, for rule based control, the Enapter Gateway is needed.

Is it possible to use a PLC to send commands to the equipment?

Yes. Individual electrolyser can be interfaced to a PLC using Modbus TCP/IP and the electrolyser’s Ethernet port. A group of devices set up on a site with an Enapter Gateway can be interfaced to a PLC via an MQTT connection to the Enapter Gateway.

Is it possible to switch the system on and off and controlling the hydrogen pressure, flow regulation, etc. remotely?

Yes. The Energy Management System allows full monitoring and control via a website or mobile phone app. It also allows for efficient support and service.

Is it possible to monitor the water inlet?

The water quality is not analysed. Depending on the supplied water, suitable maintenance intervals can prevent a decreasing water quality and damage of the electrolyser.

However, a sensor at the electrolyser’s inlet ensures that the pressure is between 1 barg and 4 barg. If it does not detect water for a longer time, the electrolyser will stop the hydrogen production and wait for a higher water input pressure. Warnings and water pressure can be monitored via the Enapter Management System (EMS).

Can I adapt the Enapter Management System (EMS) to an individual setup?

Yes. The EMS can be adapted to read and write data from all common communication standards of micro-grid systems and analogue inputs. If you would like to integrate a new system (inverters/power meters/fuel cells) into the EMS ecosystem, feel free to contact us!

Which data can be monitored?

The Enapter Management System (EMS) allows tracking of warning and error messages, inlet and outlet pressures, production volume and more. It can be accessed by any standard internet browser, such as Google Chrome and Firefox. Specific data sets can be downloaded in CSV format with a few clicks on the exports page.

When using Modbus, the same data can be read out via scripts and the same commands available in the EMS are also available via Modbus.

Can I use Enapter products also without WiFi?

Yes. The electrolyser, dryer and water tank also work without WiFi. However, for the initial setup it is mandatory to connect them to a network and add them to a virtual customer site. Please note that not all functionalities may be available without WiFi.

Where can I look up the meaning of an error code or warning that is displayed in the app or cloud?

A table of error codes and their meaning can be found here. Please look up the firmware version of your device before searching for the error or warning as those might change depending on the firmware version.

What is the Enapter Energy Management System?

Enapter is constantly expanding its Energy Management System Toolkit, which it provides to all customers. The EMS Toolkit allows integrators to create a comprehensive Energy Management System (EMS), connecting any hydrogen or energy device into a unified energy network via simple hardware and software integrations. It thus enables monitoring and control of energy systems of any size and shape. Its tools include Universal Communication Modules (UCM), the Enapter Telemetry Platform, the Enapter Cloud and our Mobile App. The EMS Toolkit also offers developer tools like Web IDE and Enapter Blueprints, as well as documentation to help system integrators and component manufacturers add our solutions to their products.

What safety features are integrated in Enapter’s electrolyser?

Enapter’s electrolyser is designed to be intrinsically safe. It self-pressurises the hydrogen side and performs leak test routines at regular intervals. Electrolysers from generation EL2.1 on are CE certified, which allows straightforward integrations into existing safety concepts. In some cases, it might be necessary to install additional safety devices (e.g. hydrogen detectors on the top of the cabinet) to satisfy local regulations and safety concepts. These hydrogen detectors can be connected with the dry contact on the front panel. It is recommended to define two safety levels (e.g. at 10% and 25% of the lower explosive limit):

What happens in case of hydrogen leakages or a pressure drop?

Enapter’s electrolysers have various sensors to ensure a safe operation at all times. If a leak is detected or the pressure unexpectedly falls, the electrolyser will shut itself down and send an error message via the Enapter Management System (EMS). The maximum amount of hydrogen gas inside one electrolyser is around 18 NL. An internal ventilation system dilutes any possible leakages below the hydrogen lower explosive limits (LEL).

Is the dry contact certified according to SIL 1 or SIL 2?

No, it should only be used to shut down the electrolyser as a preliminary measure, before a real safety risk occurs. To realize a true safety shutdown, please use a certified safety circuit and simply cut off the power to the electrolyser.

For example, in the case of a hydrogen leak, a H₂ safety sensor could ring an alarm and trigger the dry contact at a warning threshold of 10% of LEL to shut down the EL. If a safety threshold of 25% LEL is reached, it could trigger a certified safety circuit to cut the power to the entire system.

How does the use rate affect the cost-effectiveness of the electrolyser?

Enapter believes that all hydrogen production must be green, therefore Enapter electrolysers are intended to be run from renewable energies, which by nature are decentralized and intermittent. If electricity is available at the right cost for 24 hours, it will result in a faster return of invest of the electrolyser. However, that is a rare occurrence and so Enapter’s devices are designed to be started, stopped, and production rates adjusted as needed.

Is there financing available to buy the Enapter electrolyser?

Please get in touch with us.

Why is AEM the lowest cost electrolyser technology compared to PEM systems and traditional alkaline systems?

AEM is the most promising technology for bringing down the cost of electrolysis, because it combines low stack material cost and low BOP (Balance Of Plant) complexity and cost. The AEM technology allows compact, scalable devices which produce pre-compressed, highly purity hydrogen to be stacked to any flowrate needed.

What is the overall efficiency of Enapter’s electrolyser?

With the AEM electrolyser we need 4.8 kWh to produce 1 Nm³ of hydrogen. That means it takes 53.3 kWh to produce 1kg of hydrogen (compressed at 35 barg and with a purity of ~99.9%). 1 kg of hydrogen contains 33.33 kWh/kg (lower heating value), i.e. our electrolyser already has an efficiency of 62.5%. It is important to compare apples with apples: power input, hydrogen production, pressure and purity. These are very different for different manufacturers. System efficiencies (not stack efficiencies) need to be compared.

Is there a warranty for Enapter products?

In addition to the general warranty for our products as set forth in our general terms and conditions, we also provide for an additional voluntary commercial warranty under which Enapter warrants that any product purchased from Enapter will be free from defects in materials and/or workmanship for a period of at least 1-year from shipment. Enapter extends this warranty for single-core electrolysers operating with an active Enapter Monitoring Subscription Agreement (EMSA), the two years commencing from the date of shipment.

Where can I find information about upcoming products?

As soon as information about new devices and products are available, they can be found on the Enapter website. Stay in the loop and sign up for our newsletter.

Can CO₂ contamination negatively affect the lifetime of the electrolyser?

CO2 contamination in the air is not a problem for the electrolyser, as the system design avoids potential interaction with the surrounding air. However, CO2 in the electrolyte (e.g. by refilling with carbonised water) reduces the pH value and requires a more frequent electrolyte exchange. When maintained regularly (exchanging the electrolyte), this is reversible and does not contribute to explicit degradation of the electrochemical system.

What is the water input quality requirement for the electrolyser?

The electrolyser is highly resilient to water input and can be fed with purified rainwater or tap water. Simple and cheap reverse osmosis processes with resin filters can provide the required water quality. The water input to the electrolyser needs to be desalinated and have a low conductivity. The lower the conductivity, the better. For details, please see the datasheet. It is not possible to use saltwater in the electrolyser.

How is the water in the electrolyser filled up?

The AEM electrolyser has an internal tank of approximately 3.5 litres. To produce hydrogen, clean water must be provided to the electrolyser via a refilling pipe at a pressure between 1 barg and 4 barg. The electrolyser refills about 1.5 litres of water every 3 hours.

How to shut down the system?

Shutting down the system is rather easy: either manually by pressing/clicking the stop-button or automatically when the maximum pressure setpoint is reached at the outlet. One thing to note is that after every shutdown, the system will release the internal working pressure and purge a small amount of hydrogen gas from the purge line.

Do frequent start/stop cycles and ramping affect the electrolyser's longevity or performance?

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 is the duration of starting the electrolyser until it is fully functional? How long is the warm-up/ramp-up time?

The ramp up time of the electrolyser depends on the electrolyte temperature (the ramp-up is slower at cooler temperatures and quicker at warm temperatures). In most cases, the system will start with a hydration period of 60 seconds, and then ramp up to the nominal production rate with the following values:

• Warm-up time (time taken for the electrolyser to heat up): The electrolyte working temperature in the electrolyser is 55°C. The electrolyser reaches a heating ratio of about 1 °C/min and reaches maximum efficiency at 55°C. That means, if the machine is started with an electrolyte temperature of 25°C, it will take about 30 min to be fully operational and perform at its maximum efficiency.

• Ramp up time (time to reach nominal production rate): Usually, the 500 NL/h production rate is reached after about 2/3 of the total warm-up time (the warm-up time is 30 min, so if starting at 25°C, it will need 20 min to reach the maximum production rate).

• Build pressure time: When the system starts, and the electrolyser starts to heat up, the hydrogen production begins immediately, and the maximum production rate is reached later. With standard setpoints, the pressure is built up completely in 1/6 of the total warm-up time (if you start at 25 °C, then the warm-up time is 30 min, so 5 min to build up pressure are needed).

What is the lowest production rate? How much hydrogen is produced on the lowest production rate and how is the efficiency changing at partial load? How does the polarization curve look like for the stack?

The lowest production rate of the EL2.1 is 60% of the 500 NL/h, meaning 300 NL/h. The lowest production limit was set to 60% to ensure the devices’ safety. The amount of hydrogen in the vent line is then still well below the flammable limits. The energy consumption decreases roughly linearly with the production rate setpoint. The power consumption at a given production rate can be seen in the graph below. Also, the water consumption depends on the hydrogen production.

With the electrolyser control system algorithm, ramping up the production rate by 10% takes about 21sec. Ramping down by 10% takes less than 1sec.

Where are the electrolysers manufactured? Where is Enapter producing its electrolysers?

Currently, all production takes place in Crespina, Italy, close to Pisa. Enapter is presently preparing a mass production site in Saerbeck, Germany.

What is the difference between the traditional alkaline and AEM technology, and what are the advantages of AEM?

Traditional liquid alkaline electrolysers have been on the market for quite a while and are relatively cheap. However, they are comparatively slow at responding to a fluctuating power supply, so it is difficult and costly to pair them with renewable energy sources efficiently. Traditional liquid alkaline electrolysers operate with highly concentrated electrolyte solutions and at low pressure. They require additional purification and compression steps to produce high-quality gas at a higher output pressure. This is only cost-effective for centralised and monolithic multi-MW projects.

The AEM electrolyser builds on advantages from traditional alkaline electrolysers, but avoids its weaknesses:

AEM electrolysis works in a highly diluted alkaline environment and is therefore much safer to handle.

The AEM electrolyser can use similarly cost-efficient materials while making much purer hydrogen at higher efficiency.

The AEM electrolyser is fully scalable and is ideal for linking up with variable renewable energy sources.

What is the difference between the Proton Exchange Membrane (PEM) technology and the Anion Exchange Membrane (AEM) technology, and what are the advantages of AEM?

Proton exchange membrane electrolysers (PEM) use a semipermeable membrane made from a solid polymer and designed to conduct protons. While PEM electrolysers provide flexibility, fast response time, and high current density, the widespread commercialisation remains a challenge primarily due to the cost of the materials required to achieve long lifetimes and performance. Specifically, the highly acidic and corrosive operating environment of the PEM electrolyser cells calls for expensive noble metal catalyst materials (iridium, platinum) and large amounts of costly titanium. This poses a challenge to the scalability of PEM electrolysers.

The anion exchange membrane electrolysers use a semipermeable membrane designed to conduct anions. They are a viable alternative to PEM with all the same strengths and several key advantages that lead to lower cost. Due to the less corrosive nature of the environment, steel can be used instead of titanium for the bipolar plates. Furthermore, AEM electrolysers can tolerate a lower degree of water purity, which reduces the input water system’s complexity and allows filtered rain and tap water.

What is Enapter's AEM technology, and how does it work?

Enapter’s core product is the standardised and stackable anion exchange membrane (AEM) electrolyser. Electrolysers use electricity to split water (H2O) into hydrogen (H2) and oxygen (O2) through an electrochemical reaction. The stack is the electrolyser’s heart and comprises multiple cells connected in series in a bipolar design. Enapter’s unique technology is the design and operation of these cells, consisting of a membrane electrode assemble (MEA), made from a polymeric AEM and specially designed low-cost electrodes. The anodic half-cell is filled with dilute KOH (alkaline) electrolyte solution; the cathodic half-cell has no liquid and produces hydrogen from water permeating the membrane from the anodic half-cell. Oxygen is evolved from the anodic side and transported out from the stack through the circulating electrolyte. The hydrogen is produced under pressure (typically 35 barg) and already extremely dry and pure (about 99.9%). Using Enapter’s ancillary dryer module, hydrogen is delivered at 99.999% purity.

How much hydrogen can be produced by Enapter’s electrolyser and how long does it take to fill a 500 L tank?

Enapter’s electrolysers produce 0.5 Nm³/h (500 NL/h) or 0.04494 kg/h. One electrolyser module produces 12 Nm³ of hydrogen gas in 24 hours, weighting >1 kg (1.0785 kg). At the normal output pressure of the electrolyser with 35 barg, 1.0785 kg of hydrogen occupies a volume of 0.343 m³ (343 L).

A full tank of hydrogen for a passenger vehicle contains about 5 kg of hydrogen gas (stored at 700 barg) and can drive for over 500 km.

Filling up a 500 L tank with one EL running at 100% and at 35 barg takes about 500 L * 35 / 500 NL/h = 35 h until it is full.

The Enapter devices can produce and dry hydrogen 24 hours a day and 7 days per week. They do not need recovery times.

How much does hydrogen weigh?

The weight of hydrogen is 0.08988 g/L or 0.08988 kg/Nm³.

What is the energy content of hydrogen?

The energy content of hydrogen is described by its (lower and higher) heating value. The lower heating value of hydrogen can be expressed as 33.33 kWh/kg or 3.00 kWh/Nm³. The higher heating value is 39.39 kWh/kg or 3.54 kWh/Nm³. The lower heating value of 3 kWh/Nm³ is usually used if the hydrogen is not burned directly. A practical medium value to keep in mind is roughly 3 kWh/Nm³. The energy content of 1 Nm³ (=1000 NL) hydrogen gas is equivalent to 0,36 L gasoline, 1 L liquid hydrogen is equivalent to 0,27 L gasoline and 1 kg hydrogen is equivalent to 3.3 kg gasoline (based on the lower heating value).

Is hydrogen safe?

Hydrogen is a flammable gas and like with any other gas, appropriate safety measures when handling it must be ensured at all times. Hydrogen’s properties make it safer to handle than commonly used fuels. It is non-toxic, and it is an element lighter than air, so, it will quickly disperse in case of a leak. When planning a hydrogen system installation, it is important to implement appropriate safety measures, such as ventilation and leak detection.

What are the losses over time through leakage when stored in a tank? Does hydrogen have an “expire date”?

When properly stored, there are no losses. Unlike diesel for example, hydrogen does not have an expiry date and can be stored for years.

Why does it make sense to couple hydrogen with intermittent renewable energy sources?

The world has reached a turning point in our understanding of energy. Solar and wind are the two fastest growing energy sources. While governments and industry increasingly understand that fossil fuels are a thing of the past, the challenge remains to make solar and wind useable when we need them. Variable renewables are competitive, and customers are increasingly demanding reliable, secure and independent energy supply from sustainable sources. On-site green hydrogen production allows for complete green energy independence and security. A burgeoning global industry is taking shape around hydrogen’s potential as a storable fuel or energy carrier and many advantages over battery-electric technology result in hydrogen gaining traction with industry, environmentalists and leading governments.

Why green hydrogen production?

The vast majority, around 99%, of hydrogen used globally is still produced from fossil fuels. Most of that is done by steam methane reforming of natural gas, a process which emits large amounts of greenhouse gases. We speak about green hydrogen when renewable energy sources are used in an electrolyser to make hydrogen from water. Hydrogen is the bridge between renewable power generation and other types of energy vectors and allows us to clean up more than just the electricity sector with fossil-free fuels.

Where is hydrogen currently used?

Hydrogen is an energy carrier and as such, a true multi talent. Today, hydrogen is directly used mainly in industrial processes of many kinds, such as ammonia fertilizer production, food processing purposes, the float glass industry, cooling for power plants and in the semiconductor and electronics industry, and many more.

Hydrogen also finds application as a fuel in transport often with water as the only by-product/emission. Vehicles with fuel cells on-board (cars, buses, trains, drones, planes) use hydrogen as the fuel to power their electric propulsion systems. But fuel cells are increasingly important in the power sector also. They can supply power to residential homes, commercial and industrial buildings, and remote locations. They can provide 24/7 power or serve as a backup power device. Hydrogen offers much greater energy storage density and longer autonomy than batteries.

Why do we talk about hydrogen?

We believe that hydrogen will play a central role for the design of modern energy systems to allow for complete green energy independence and security. A burgeoning global industry is taking shape around hydrogen’s potential as a storable fuel or energy carrier. The many advantages it has over battery-electric technology result in hydrogen gaining traction with industry, environmentalists and leading governments. With an abundance of variable renewable energy resources coming on-line, green hydrogen is the solution to power the green energy system of the future.

What is hydrogen?

Hydrogen is the first chemical element of the periodic system. Hydrogen is the most abundant element in the universe. It is the lightest and simplest element we know, one proton and one electron, yet it is high in energy. Hydrogen is an energy carrier and a great multi-talent: it can be transformed into electricity, used as a fuel for transport, used for heating and cooling purposes, as well as various other industrial applications.