FAQs

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.

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 online, green hydrogen is the solution to power the green energy system of the future.

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 fertiliser 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 onboard (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 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.

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. Onsite 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.

What are the losses over time through leakage when stored in a tank? Does hydrogen have an “expiry 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.

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 time. 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 is the AEM technology?

Enapter’s core product is the standardized and stackable anion exchange membrane (AEM) electrolyser. Electrolysers use electricity to split water (H2O) into hydrogen (H2) and oxygen (O2) through an electrochemical reaction.

At the heart of the electrolyser sits the electrolytic stack. The stack is made up of multiple cells connected in series in a bipolar design. Enapter’s unique technology relates to the special design and operation of these cells, each comprising 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 bar) and already extremely dry and pure (about 99.9%). Using Enapter’s ancillary dryer module, hydrogen is delivered at 99.999% purity. As hydrogen is generated, the anodic half-cell side is topped up with distilled water or purified tap/rainwater.

What is the difference between the PEM and 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 largely due to the cost of the materials required to achieve good 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 an insurmountable 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.

  1. AEM electrolysis works in an alkaline environment, where less expensive non-PGM catalysts have high stability. Therefore, PGM catalysts are not required. Due to the less corrosive nature of the environment, stainless steel can be used instead of titanium for the bipolar plates.
  2. At the same time the hydrogen produced with AEM is of the same quality at higher efficiency than most PEM electrolysers.
  3. AEM electrolysers can tolerate a lower degree of water purity, which reduces the complexity of the input water system and allows for the use of filtered rain and tap water. Completely de-ionized water is not required.
What is the difference between the traditional alkaline and AEM electrolysers?

Traditional liquid alkaline electrolysers have been on the market for quite a while and are relatively cheap. However, they are comparatively poor at responding to fluctuating power supply, and so it is difficult and costly to efficiently pair them with renewable energy sources. 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. The AEM electrolyser builds on advantages from traditional alkaline electrolysers, but avoids weaknesses:

  1. AEM electrolysis works in a highly diluted alkaline environment and is therefore much safer to handle.
  2. The AEM electrolyser can use similarly cost-efficient materials while making much purer hydrogen at higher efficiency.
  3. The AEM electrolyser can fully ramp and is ideal to link up with variable renewable energy sources.
What is the advantage of AEM vs PEM vs traditional alkaline electrolysis?

AEM electrolysis combines the benefits of PEM and traditional alkaline:

  • Flexible operation, safe due to the separation of H2 and O2
  • Low stack material cost – low Balance of Plant (BOP) complexity and cost
  • High purity hydrogen production (highest efficiency compared to PEM and traditional alkaline)
What is the efficiency of the electrolyser?

With the current AEM electrolyser we need 4.4 kWh to produce 1 Nm³ of hydrogen. That means it takes 48.9 kWh to produce 1kg of hydrogen (compressed at 35 bar 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 68%. 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.

What is the hydrogen yield for the AEM electrolyser?

Enapter has standardized the AEM electrolyser into a fully stackable and flexible product: the EL 2.1. Each module yields 500 NL/hr or 0.5 Nm3/hr of hydrogen gas output at 35 bar and with a purity of ~99.9% (optional >99.999% with a dryer module). Multiple units of the EL2.1 electrolysers can be easily combined into one larger system.

(EL 2.1 data sheet)

What is the operative power consumption of the AEM electrolyser?

The operative power consumption at standard conditions is 2.2 kW. The peak power consumption (max power draw at any time) is 2.8 kW and should be considered for sizing of electrical safety devices and wiring. You can find the standard specifications in the datasheet.

How is hydrogen produced at pressure in the electrolyser?

Our cell allows for differential pressure – when hydrogen is produced, it accumulates on the cathode side and fills the space before the backpressure valve. Once the pressure reaches a setpoint (30 bar), hydrogen will start to flow from the hydrogen outlet of the electrolyser. The electrolyser will then continue to operate until the external pressure on the outlet reaches 35 bar, which is the point at which the electrolyser shuts down in “max pressure” mode.

What is the pressure of oxygen produced?

The pressure on the oxygen side is at atmosphere (0.1 MPa).

What is the composition of the oxygen that we produce?

Our oxygen content, though it hasn’t been formally characterized, is primarily O2 with a high relative humidity and trace amounts of atmospheric gases, plus about 2% H2. Any KOH/K2CO3 (potassium carbonate) will be solvated or exist only in trace amounts of ppm concentration within water droplets that are on the outlet line.

What is the water content at hydrogen side outlet?

The water content in the hydrogen gas produced is <1,000 ppm. Adding the optional dryer to remove water, reduces trace amounts to > 10 ppm at the start (at -60.5˙C dewpoint) to about 3 ppm (at-70˙C dewpoint) on average.

What is the water input quality requirement for the electrolyser?

The AEM 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 conductivity of <20 microS/cm. It is not possible to use saltwater in the electrolyser.

(EL 2.1 data sheet)

How is the water in the AEM electrolyser replenished?

The AEM electrolyser has an internal tank of approximately 3.5 litres. In order to produce hydrogen, clean water with a conductivity of <20 µS/cm must be provided to the electrolyser. Water must be present in the electrolyser water refilling pipe at a pressure between 0.5 bar and 4 bar to do so. The refilling from an external water tank starts automatically and is independent from the hydrogen production. The EL2.1 will need about 1.5 litres of water for a refill and it will ideally refill every 3 hours. Once the refilling signal is triggered, the electrolyser will try to refill every 10 minutes until HIGH level is reached or LOW water level triggers error messages. Once the refilling process has started, it needs to be completed within 10 minutes to avoid safety shutdowns.

What is the duration of starting the electrolyser until it is fully functional, in other words, what’s the warmup time?

The ramp up time of the AEM electrolyser depends on the electrolyte temperature (the ramp-up is slower at cooler temperatures and quicker in warm temperatures). Typically, the system will start with a hydration period of 90 seconds, and then ramp up to the nominal production rate with the following values:

  • Warm-up time (time for the EL to heat up): the electrolyte working temperature in the AEM electrolyser is 55°C. The EL can usually reach a heating ratio of 1 °C/min, at 55°C at maximum efficiency. For example, if we start the machine 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/hr production rate is reached in about 2/3 of the total warm-up time. time (the warmup time is 30 min, so if you start at 25°C, you will need 20 min to reach max production rate)
  • Build pressure time: when the system starts and the EL starts to heat up, the hydrogen production starts immediately, and the maximum production rate is reached later. With standard setpoints, the pressure is completely built in 1/3 the total warm-up time (say you start at 25°C, you need 10 min to build pressure)
What effect do frequent start/stop cycles and ramping have on the longevity or system performance of the EL?

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, normal use with several on-off cycles per day does not affect the system negatively.

In industrial or in-process use cases with frequent changes in the hydrogen consumption rate, we recommend installing a buffer tank (at least 50L) to hold some hydrogen and to avoid switching the electrolysers on and off every few minutes.

To help with the control of the devices for these constant consumption use cases, it is also possible to regulate hydrogen production to keep the outlet pressure stable at a given setpoint with the use of the Enapter gateway running rule-based controls; this also minimises system cycling.

Is a hydrogen storage tank required to operate the AEM electrolyser safely?

Enapter provides the electrolyser system for hydrogen generation from electrical energy and water. Each Enapter electrolyser module generates a stream of hydrogen at a rate of 500 NL/hr which is released at 35 bar. 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 system performance to degrade. Normal use with several on-off cycles per day is no problem. The storage system, or immediate use case of the hydrogen output gas is outside Enapter’s standard scope of delivery and normally taken care of by the system integrator or end customer. In industrial or in-process use cases with very frequent changes in the hydrogen consumption rate, our customers normally install a buffer tank (~50L) to hold some hydrogen and to avoid switching the electrolysers on and off every few minutes.

What is the lifetime of an Enapter electrolyser?

We expect a lifetime of the stacks of >30,000 hours.

Do you offer a warranty?

Yes, our systems come with a standard warranty of 1 year. With an activated Enapter remote monitoring and control system, Enapter offers a free extended warranty of 2 years. Enapter is happy to set up customised service agreements with customers/partners requiring longer guarantees.

What maintenance is required on the AEM Electrolyser?

The only regular maintenance needed is a replacement of the electrolyte once a year. The electrolyser operates with a slightly alkaline solution (1% KOH) which makes it safe and easy to handle. The electrolyte is filled into the electrolyser during the initial installation and is not consumed. Only water needs to be supplied to the electrolyser during operation, no KOH needs to be refilled. The maintenance task to drain the used electrolyte solution and refill with fresh electrolyte takes only about 15 minutes.

Is it possible to remotely control the system in terms of on/off switching, H2 pressure, flow regulation etc?

Absolutely, the best way to control our electrolysers is via our Enapter Energy Management System, which allows full monitoring and control via a web dashboard and mobile app. It also collects monitoring data to enable efficient support and service of the system.

What does the monitoring measure and control when it comes to the Dryer 2.0?

As for our software monitoring system, it measures and displays input pressure, output pressure, several temperature levels, fan speeds, digital in- and outputs. You can control (start/stop/reboot/over-the-air firmware update (OTA)). This is for the dryer only, for the EL there is obviously much more specs to monitor and control. Please contact us for a demo of the monitoring software.

What kind of smart production regulation possibilities are there using the EMS in my system?

The EMS and its system of extension modules can perform a large variety of smart functions. Due to the rule-based control, the system can truly be programmed to be as versatile as needed. For example, the system can regulate production rates to keep the output pressure stable at a certain pressure set point (useful for constant flowrate requirements). Another example is the use case for the Big Thing microgrid, using the EMS and the integrated extension modules, the system can regulate which devices are running when, anticipate bad weather and determine how much hydrogen is needed to be stored for continuous autonomy.

Can we use the EMS extensions to integrate inverters/power meters/fuel cells from other suppliers?

Yes. The adaptability of the EMS allows it to communicate and read data from all commonly used industrial communication protocols normally used in microgrid systems, as well as analogue inputs. If you would like to integrate a new component into the EMS ecosystem, please contact us for help!

What does the Enapter mobile app enable me to do?

Enapter’s development approach is “mobile first”. The mobile application is the main tool used for setup and configure the end-user’s site and devices, such as Eelectrolyser, Dryer, and Universal Communication Module with Extensions. The Enapter mobile app allows easy and secure system setup using QR codes, management and monitoring all over the world. Mobile applications are available for Android and iOS.

Which operation systems are supported by the Enapter EMS system?

The mobile app is available for Android and iOS. The web dashboard runs in any standard internet browser, such as Google Chrome, Firefox, etc.

Where I can download the application?

You can download it in the Apple App Store or Google Play app store.

How can I set up custom control logic for my energy system?

The Enapter Gateway enables this functionality. One Gateway can be installed per user site to enable advanced control features and mitigate internet connectivity issues. Using the Gateway, the Enapter Ruel Engine can be configured in a simple if-then-else logic defined by the user. This logic allows to send action commands to devices based on conditions driven by sensors or other device’s data integrated in the energy system. The logic is set using the convenient command line interface (CLI) and can extend to any level of branching and complexity. In cases when standard condition rules are not sufficient it is possible to extend functionality by contributing additional logic using Lua scripting language.

How can I export data for analysis?

The Enapter Cloud collects performance and error data from the Enapter Gateway and all connected devices such as Electrolysers, Dryers and UCMs. It stores it in a time series database and provides real-time or on-demand visualisation of collected data on customizable dashboards. Specific data sets can also be downloaded in CSV format with a few clicks on Exports page.

What is the technology of the Enapter Dryer?

The Enapter Dryer 2.0 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 comprised of two cartridges filled with a highly adsorbent material. One cartridge will be catching the humidity from the hydrogen gas stream of the electrolyser, while the other cartridge is heated and regenerated with a small reverse stream of hydrogen gas (about 1% of the output of the EL). This reverse stream of hydrogen gas will carry out the water caught by the dryer and be released into the atmosphere from the purge output of the dryer. All of this is completely automatic, and the system is fully integrated in the Enapter EMS, so the states of the dryer, temperatures and pressures of the system can be monitored. The drying process gets the purity level to >99.999% in molar mass. We do measure the dewpoint (on average below -70deg C) of a system during the final acceptance test in our factory, but we don’t have any continuous purity measurement in the system. In response to some infrequent customer requests, some of our system integration partners are buying portable dew point measurement equipment to check the dew point on the customer site periodically, or during the annual maintenance visit. We curently have two models of the dryer: one with 2 cartridges that dries up to 1,000NL/h, and one with 4 cartridges that dries up to 2,000NL/h.

(Dryer 2.0 data sheet)

What is the Enapter Water Purification System (WPS)?

The Enapter WPS (data sheet) is a simple reverse osmosis processes coupled with resin filters to provide the required water quality with a conductivity of <20 µS/cm to the AEM electrolyser. The WPS has a water production rate of up to 1 L/min at the required conductivity level. The flow varies depending on water input quality and can be much lower depending on water input quality. Water conductivity should be checked frequently to avoid low quality water going into the electrolysers. It is recommended to change the RO filter every 6 months or after 2,500 liters of purified water. Resin filters should be changed if they cannot guarantee the correct water conductivity.

With an assumed flowrate of 1 L/min the WPS can provide water directly to up to 8 units of the AEM electrolyser given that they all need to refill at the same time without a buffer tank. This is very unlikely, and the WPS could probably supply much more units, however, in that case you would probably want to choose a system with higher flowrate altogether.

IMPORTANT: While water can directly be supplied to electrolysers from the WPS, we recommend the use of a water tank, ideally combined with a conductivity meter to recognize and dilute impurities! The customer always needs to ensure the required conductivity. Using a WTM or other clean water storage tank increases the autonomy of the system and makes it easier to monitor the water quality. It will also give the operator a little more time to react and maintain the water purifier should the water quality worsen. Therefore, Enapter recommends using a WTM or other buffer tank, as well as continuous water conductivity monitoring.

What is the Enapter Water Tank Module (WTM)?

The water storage capacity of the Enapter WTM is 35 litres. The pump of the WTM offers a supply rate of up to 3.8 L/min. This refilling rate is reached in case there are no pressure losses in the pipes. Depending on the distance to the destination of the electrolysers a single typical refilling can be done in between 10-20 seconds. This allows for 30 electrolysers to be refilled at the same time if the water in the WTM is accordingly replenished. While the WTM can supply even more electrolysers in one stacked system, for redundancy purposes it is suggested not to supply more than 30 electrolysers.

(WTM data sheet)

We need a water purification unit to feed the electrolyser. What is the maintenance associated with this?

If a water purification unit is needed, we recommend the WPS to clean up tap water and supply it to the electrolyser. The maintenance consists of filter/resin replacements and will depend on the input water quality and the amount of water consumed. As long as the water purity requirements of our electrolysers are met, you can use any water purification system you like.

What safety features are integrated?

The electrolyser is designed to be intrinsically safe – it self-pressurizes the hydrogen side and performs leak test routines at regular intervals or when some data suggests a leak could be present. The EL2.1 is CE certified, and in our experience it is very straightforward for our customers to integrate the electrolyser into the safety concept on their sites. Depending on the specific site safety concept and local regulations, some of our customers install additional safety devices such as a hydrogen sensor in order to cut the power if any hydrogen leaks occur on the site. The electrolyser also has a dry contact on the front panel that triggers a safe shutdown based on an external signal.

Are the cabinet/modules equipped with internal H2 gas sensors and related emergency shutdown logics?

The electrolysers have an internal hydrogen leakage detection, so they will shut themselves down in case of a substantial leak being detected. However, there is no gas sensor present in each machine. If required by the safety concept on the end-user site, we recommend a sensor to be installed at the top of the cabinet. We recommend defining two safety levels (for example at 10% and 25% of LEL):

  1. When a small unexpected leak occurs, closing of a dry contact on the front panel of the EL2.1 to triggers a safe shutdown.
  2. In critical situations with large leakages, simply cut of the power.