FAQs

How much does hydrogen weight?

The weight of hydrogen is 0.08988 g/L. Enapter’s electrolysers produce 0.5 Nm³/h (500 NL/h) or 0.04494 kg/h. One EL2.1 module produces 12 Nm³ of hydrogen gas in 24 hours, weighing > 1kg (1.0785 kg). At the normal output pressure of the EL2.1 with 35 bar, 1 kg of hydrogen occupies a volume of 0.343 m³ (343 L).

When stored in a tank, what are the losses over time through leakage? Does hydrogen, like for example diesel, have an "expiry date"?

When properly stored, there are no losses. While diesel and all other Hydrocarbon based fuels have an expiry date of around a year, hydrogen can be stored for years.

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. Oxygen is evolved from the anodic side and transported out from the stack through the circulating electrolyte. The hydrogen is produced under pressure (up to 35 bar) and already extremely dry and pure (about 99.9%). Using Enapter’s auxiliary dryer module, hydrogen is delivered at 99.999% purity.

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 commercialization 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.

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 centralized and monolithic multi-MW projects.

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 to monitor the state, temperatures and pressures.

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 lowest production rate? What is the hydrogen percentage while producing on the lowest production rate?

The lowest production rate is 60% of the 500 NL/h, meaning 300 NL/h. The lowest production limit was set to 60% to increase devices’ safety. The amount of hydrogen in the vent line is then still less than 2%. The energy consumption is roughly linear to the production rate (60% of the total power consumption at 60% production rate).
Ramping up the production rate by 10% takes about 21 sec. Ramping down by 10% takes less than 1 sec.

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 AEM 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:

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

The electrolyser is intended to be operated intermittently, as it can happen from renewable energy sources. However, like with most electrochemical systems, it is better to avoid cycling the system on and off very frequently, as this can accelerate the degradation of system performance. Meanwhile, regular use with several on-off cycles per day does not affect the system negatively.

Are there specific prescriptions related to the shutdown procedure of the system?

There are no specific prescriptions for the shutdown procedure; the system does this automatically. One thing to note is that after every shutdown, the system will release the internal working pressure (hydrogen at 30-35 bar) and purge a small amount of hydrogen gas from the purge line.

Can CO₂ contamination negatively affect the lifetime of the electrolyser?

CO₂ contamination is not a problem for the electrolyser, as the system design avoids potential interaction with the surrounding air. But, even if there would be CO₂, they would only reduce the AEM’s pH value, but this is reversible and would not contribute to explicit degradation of the membrane.

Is Nitrogen used during the process?

Enapter’s electrolysers do not use Nitrogen.

What is the surface area of the membrane?

This information is part of Enapter’s intellectual property.

What is the electrolyser cell DC voltage range?

This information is part of Enapter’s intellectual property.

What is the electrolyser cell minimum voltage?

This information is part of Enapter’s intellectual property.

What is the single electrolyser chamber voltage range?

This information is part of Enapter’s intellectual property.

What is the electrolytic cell DC current range?

This information is part of Enapter’s intellectual property.

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

Enapter utilizes a proportional relief valve to pressurize the system before the operation and several pressure transmitters to control and monitor stack and outlet pressures. A solenoid valve keeps the process gas contained which opens and returns the system to a safe state if an error is detected.

What is the current density?

This information is part of Enapter’s intellectual property.

What is the electrolytic cell rated operating temperature in degree Celsius and degree Fahrenheit?
What is the energy content of hydrogen?

The energy content of hydrogen is described in the (lower and higher) heating value. The lower heating value of hydrogen can be expressed as 33.33 kWh/kg or 2.78 kWh/Nm³. The higher heating value of hydrogen is 39.41 kWh/kg or 3.28 kWh/Nm³. That means roughly 3 kWh/Nm³.

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 (H₂O) and 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 produce oxyhydrogen gas?

Hydrogen and oxygen should always be kept separately to avoid explosions and fire! It is not possible to directly produce a combined gas without cleaning the oxygen and equalize pressures first.

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

The electrolyser purges about 20 NL/h for each ramp down and twice a day if is running continuously.
The dryer uses about 15 NL/h of hydrogen to drag away the humidity.

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?

Yes. But it is neither pressurized nor purified.

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.

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.

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.

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 uninterruptible power supply?

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

How quick is the dry safe shutting down the system?

An interruption at the dry safe will immediately shut down the system, similar to a power cut at the power supply. The electrolyser will then go into error mode, and the hydrogen production will stop. The Power Supply Unit (PSU) will also cut the power, and the valve at the purge line will open.

Is a buffer tank needed at the hydrogen outlet?

No. A buffer tank is not needed but recommended for all setups where the hydrogen outlet is not directly connected to a storage tank. In those cases, a 50 L buffer tank will keep the pressure at the output stable.

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 cannot be added.

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

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

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.

What maintenance is required for the AEM Electrolyser?

Almost none. The main regular maintenance needed is draining and refilling electrolyte once a year. 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 is it possible to detect the electrolyser’s end of life?

The power consumption may increase, which will eventually end in a decreased efficiency.

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

The amount of absorbed water might shrink, and therefore the hydrogen will be wetter. The electrolyser or the dryer does not measure the hydrogen’s purity.

Can the electrolyser be recycled?

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

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

It is not compliant with the IEC 61508 standard because the dry contact is not relevant for Enapter’s risk analysis. There are current double protection, safety check valve at 42,5 bar, and more safety measurements. The panel is labelled “dry contact” instead of “safety” to avoid confusion.

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

Enapter’s electrolysers have various sensors to ensure 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 of hydrogen gas inside one electrolyser is around 20 NL. An internal ventilation system dilutes any possible leakages below the hydrogen lower explosive limits (LEL).

What safety features are integrated?

Enapter’s electrolyser is designed to be intrinsically safe. It performs leak test routines at regular intervals. Electrolysers from generation EL2.1 and 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 reach 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 LEL):

How can the electrolyser and other devices be connected to the Wifi?

There are two possibilities: either connecting a device directly to the WiFi or connecting the Enapter Gateway and combining several devices at one place (including external devices like solar panels, fuel cells and storage tanks). For both options a smartphone with Bluetooth and WiFi as well as the Enapter app is needed. The app is necessary to set up the first connection.

Which data can be monitored?

The Enapter Management System (EMS) allows tracking 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.

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 for help!

Is it possible to monitor the water inlet?

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

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 use a PLC to send commands to the equipment?

Yes. Enapter’s electrolysers are either monitored and controlled by the Enapter Management System EMS or via the Enapter gateway (a Linux based PC such as Intel NUC). Enapter can provide an interface to a PLC using Modbus TCP/IP and the Ethernet port.

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 realised 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.

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.

How 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. The power can be cut off immediately by creating a safety chain using the Dry Con interface. Depending on the duration the electrolyser can be restarted again within a few minutes.

Can the EL2.1 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.

Are there updates available for the Enapter devices?

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

Is your system CE certified?

The EL2.1 is CE certified.

Is the electrolyser ATEX certified?

Unfortunately, our system is not designed to be installed in an ATEX area. However, the product 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 project developers/installers responsibility to ensure that the area where the electrolysers are installed must never contain any explosive atmospheres. An appropriate safety concept must be implemented to mitigate the risks of any failures and consequences of leakages of flammable gases. Such a safety concept could involve, for example, hydrogen sensors, forced ventilation, or natural 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.

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

The electrolyser has a standard ¼” Swagelok bite-type Stainless Steel connector for the hydrogen outlet piping. Internally it is protected by relief and check valves to prevent backflow of external tank/H₂ distribution lines. In some few cases, local rules or regulations require welding.

Is there a warranty for Enapter products?

Yes. Enapter products are shipped with a standard warranty of one year. By activating the Enapter Management System (EMS), it can be extended to two years. Enapter is happy to set up customized service agreements with customers and partners requiring longer warranties.

How much does it cost to produce hydrogen with Enapter’s AEM electrolysers? What is the price of a kg of hydrogen?

The cost of green hydrogen is a function of the volume of power needed, the cost of power supplied, the cost of the electrolyser and its system, and the operative system to run the system. We are suggesting to use these factors in a simple formula to transparently compare pricing.

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 small, scalable devices which produce pre-compressed, highly purity hydrogen.

What are the maintenance and operational costs for an Enapter electrolyser, Dryer, water tank and water purification module?

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

What is the cost for stack replacement?

Stack replacements are free within the warranty. Outside of the warranty, Enapter is happy to accept the units back in our factory for a diagnosis and refurbishment. The cost of a complete refurbishment of an EL2.1 has not been set yet, but is estimated to be roughly 50% of the cost of a new machine.

Is there financing available to buy the Enapter electrolyser?

Currently, Enapter does not provide any financing options to customers. Any orders for electrolysers require a prepayment at order confirmation and are typically fully paid at the time of shipment from the Enapter factory.

Is shipment included if customers want to return the product within warranty?

From the warranty conditions: Enapter will provide standard ground shipping. If expedited shipping is requested, the shipping costs will be billed to the customer. Enapter does not provide new replacement equipment to distributors or installers who exchange new equipment from their stock to customers in the field at their own discretion.

What is the cost for Enapter to send technicians on site?

The daily rate for engineers to go on the customer site for installation and training support depends on the location and the nature of the work to be undertaken.

Is there any consultation or service fee after warranty is expired?

Enapter provides free remote diagnosis and consultation even after the warranty is expired, as long as the Enapter Management System is active and collects monitoring data. After the warranty expires, a monthly/quarterly/yearly subscription is required to keep the remote monitoring system active.

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 electricity, which by nature is decentralized and intermittent. If you had electricity available at the right cost for 24 hours, of course that would result in a faster return of invest of your electrolyser. However, that is a rare occurrence and so our machines are designed to be able to start, stop, and adjust production rate as needed.