A Guide to Hydrogen Generators (Gensets)
Curious about what exactly is a hydrogen generator? We have created this handy guide that tells you everything you need to know about hydrogen gensets.

With rising energy costs and the need for net zero to be achieved sooner rather than later, there is an ever-growing need to find new solutions for old technologies. Enter: hydrogen-powered generators.

The global diesel generator market size is expected to reach USD 38.53 billion by 2030, escalating at a compound annual growth rate of 8.5%, according to a new report by Grand View Research, Inc. Demand for emergency backup power and off-grid power generation systems across several end-use industries including manufacturing & construction, telecom, chemical, marine, oil & gas and healthcare will keep increasing thus driving the need for more fuel. Currently, that means more diesel.

However, this increasing demand and market growth, inevitably, goes against the general consensus of lowering emissions and finding alternative carbon-free fuels. This is why it is critical to understand the benefits provided by hydrogen-powered generators.

The diesel crisis can be averted with hydrogen generators


• Burning 1bn+ litres of diesel per year

• 125k UK diesel generators

• Generating 2.2TWhs of electricity

• Producing 3.6m tonnes CO2e + NOx


Hydrogen Fuel Cell Generators

• CE rental-ready products available

• 3.82TWhs curtailed wind energy can be used to generate hydrogen

• Zero emissions at point of use - only water

Why Hydrogen for large off-grid power?

Hydrogen beats the competition across the core requirements for NRMM (non-road mobile machinery) power:

Sources of hydrogen

Regardless of the “colour” of hydrogen, it is all the same gas. The colours specify only where the hydrogen has been sourced from.

Brown and Grey hydrogen has a carbon footprint

Hydrogen made from coal or methane where the resultant greenhouse gases are not captured. 71% of the world's hydrogen currently comes from methane made through a process called Steam Methane Reforming (SMR). Superheated steam is used to break methane into H2 and CO2, producing about 10kg CO2 per 1kg H2.

Blue hydrogen is low carbon to neutral

This is hydrogen still made from hydrocarbons, but which is carbon neutral. It is made from either fossil fuels where the CO2 is captured and stored, or using methane captured from landfill.

Green hydrogen is zero carbon

This is hydrogen made by using renewable electricity, (e.g. wind, solar or other renewable energy) to chemically break water into hydrogen and oxygen. This is done through a process called electrolysis using what is called an electrolyzer. At a basic level electricity is passed through water to produce oxygen and hydrogen. The hydrogen is then captured, pressurised for transport, and bottled.

How green is hydrogen? Even Grey H2 is better than diesel

Grey H2 has a carbon footprint, but it is in most cases a significantly lower footprint than diesel. Most diesel engines are operating between 10% and 30% efficiency. At these efficiencies Hydrologiq has calculated a 31%-81% lifecycle reduction in CO2e when using grey hydrogen converted to electricity using a fuel cell.

Below we have calculated the CO2 footprint comparison to diesel at different engine efficiencies/engine loads.

Read more: our FAQ page How Green is Hydrogen? calculates the difference in emissions from diesel, grey hydrogen, and green hydrogen.

Benefits of hydrogen

Always greener than diesel: Even when using Grey H2, hydrogen generators create just a third of the CO2 of a diesel generator. When using Green H2 it is carbon guilt-free.

Silent and no vibrations: No moving parts mean that hydrogen generators run virtually silent with no vibrations. Perfect for operating in urban environments or late into the night.

Zero emissions, Zero fuel spills: Hydrogen generators produce only water. No emissions or fuel spill risks make it ideal for Ultra Low Emissions Zones or environmentally sensitive locations.

Operationally equivalent: Mobile, plug-and-play deployment, and with similar operational procedures, it should lead to minimal operational or training changes.

Reliable and low maintenance: No moving parts reduce maintenance costs and increase reliability compared with diesel gensets. Thus, reducing project delivery risk.

Instant start and no need to idle: Sub-second response time, plus excellent start-up and load following. Also, hydrogen generators only consume H2 when power is being drawn. No idling means no waste. With our deployment experience, we have visited many sites which have had the diesel generator running but ultimately doing nothing (or simply powering some low-power equipment such as lights and security cameras). The waste comes from the fact that when diesel generators are at low load (when idling), the generator is in fact at its least efficient.

Whilst diesel generator idle waste can be solved by coupling it with a battery, most hydrogen generators already have built-in batteries. Plus, hydrogen generators are much faster to turn on if it is really needed to switch them off, which is not the case with diesel generators.

What is a hydrogen generator?

Hydrogen generators can use two very different technologies to turn hydrogen into electricity.

The first is the internal combustion engine - similar to the combustion engine used in current diesel generators. Here, a hydrogen-air mixture is burned inside a combustion chamber. Just like diesel, this miniature explosion produces force to turn a crankshaft and an electrical current is generated via the attached alternator.

The second technology uses a fuel cell (FC) to generate electricity. A fuel cell generates electricity by chemically reacting hydrogen with oxygen (usually from the air) to create water. Hydrogen is put into close contact with oxygen inside the fuel cell, separated only by a membrane - typically a proton-exchange membrane (PEM). The hydrogen’s proton moves through this membrane to react with the oxygen, which forces the hydrogen’s electron along a circuit to rejoin, creating an electric current. Water is then evacuated from the fuel cell as the only by-product. There are many different types of FC. However, in principle, they all work like this.

In most cases, a hydrogen generator will be connected to externally bottled hydrogen. This hydrogen is typically produced somewhere else and brought in gas bottles to the location of the hydrogen generator. Internally hydrogen generators will contain a FC, power electronics, control systems for electronics and gas, and often a battery to manage power up and down procedures as well as supply extra power during peak loads.

Storing Hydrogen

Compressed gas. Hydrogen is most commonly stored as a compressed gas at 200bar, 300/350bar, or 700bar.

High-pressure trade-off. Every increase in compression reduces the overall efficiency and increases cost. However, in some cases the volumetric space taken up by hydrogen is more important than the loss of energy efficiency, for example in vehicles 700bar is used to reduce tank size. In short, it depends on the business case around the use case.

Liquid hydrogen. It can also be stored as liquid hydrogen. This requires more energy than compression in order to keep the hydrogen cold enough. -252C, to stay as a liquid. Thus increasing the cost of compressed hydrogen. Again in some use cases, liquid hydrogen makes the most sense. For example, in trucking, the size available for the payload is increased using liquid hydrogen and the weight of the truck decreased as fewer storage tanks are needed for the same volume of hydrogen, the same is true for long-distance transport of hydrogen.

Ammonia, silicon liquid carriers, and metal hydrides. Hydrogen can be stored in the form of ammonia or by chemically bonding it with some liquids or metals. This can increase the volumetric density of hydrogen but often comes with other challenges around cost, high temperatures, transporting a highly toxic fluid (ammonia), or still being in early research and development.

Genset Use Cases

Knowing where, how and when to use a hydrogen generator is relatively easy as it should be considered a direct replacement for diesel generators. With that being said below are some use cases where hydrogen generators can be used for optimal net-zero and performance benefits.


Construction is a big user of diesel generators and this is for a good reason. Many sites start off being off-grid so power is inaccessible where it is most needed. For example, lights and cabins are set up in the very early stages of a construction project which requires power in some cases 24/7. 

Another factor to consider with construction sites is that there are people working on them which also means they are exposed to the various pollutants of a diesel generator - noise and air. With this in mind, installing hydrogen generators provides emissions-less, quiet power to key parts of your site but it also provides consistently clean energy, meaning no more flickering lights in the cabins.

With a push to decarbonise construction inevitably getting more steam, the next coming years will be a pivotal time for new technologies and requirements on construction sites. Low-emission zones will quickly become no-emissions zones which will require solid planning and preparation to avoid any potential project closures.


To keep their servers online, data centers need steady power. Server availability may be impacted by power outages. These interruptions may cause businesses with internal servers to lose productivity. If a power outage affects the servers that companies host for other businesses, those businesses will suffer.

Generators protect against lost revenue and decreased productivity for data centers and any other enterprises that need continual power for their systems.

Hospitals and Clinics

In the medical field, maintaining power could mean the difference between life and death. For instance, gensets are widely used as backup power sources in hospitals. If a storm or local blackout results in electrical issues, several kinds of power sources give electricity.

To assure an endless supply of fuel from the nearby gas lines, the generators for these kinds of facilities may be connected to a natural gas supply. These generators don't need to have their fuel tanks refilled. When the main power is turned off, they can also switch on automatically.

Operation of Emergency Power

In an emergency, backup power for businesses can keep them operating. Operations for crucial operations can continue after storms with the help of this backup power. 

For instance, backup generators may be necessary for emergency response teams or news outlets that must continue to broadcast during emergencies in order to notify the public. To power incubators, ventilators, and other support equipment for keeping livestock safe and healthy, even farms may need backup generators.

TV/Film Production

The need for quiet, reliable energy on a TV or film set is vital for cost purposes. Noise in the background will require longer post-production or even keeping actors on set which will increase daily costs. Diesel generators are noisy so they do inevitably cause interference when filming, requiring time to be spent on editing. 

With hydrogen generators, there is very little noise, if any, that can cause delays and increase production costs. Also given that it is emissions-less, people working around units or locations which require power will not be getting exposed to pollutants.

Remote Locations with Power

Gensets can provide an option for obtaining electrical power in rural areas that are not wired into the power grid. Examples include rural hilly regions or even remote island locations. Emergency response teams can provide assistance in places following a natural disaster with the aid of generator sets. 

A genset can also be used by military operations to power essential equipment in places without access to a power grid.

Be sure to check our website h2generators.co.uk for examples of various hydrogen generators that we are able to source.



Hydrologiq is the online platform making off-grid hydrogen happen.

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