Formic acid generator as the backbone for the electrified construction site

More and more construction site equipment is electric, but that provides little environmental benefit if charging is done by a smelly diesel generator. The formic acid generator offers a solution. Refueling costs a bit more, but you do have an environmentally friendly energy source.

The construction site of De Groene Boog will soon have the first ‘Hydrozine generator’. Voorbij Funderingstechniek, which is working there on a new section of A16, will charge its electrical equipment with the DENS X2: a midi digger, an anchor drilling machine, a machine for high-speed piles and a 20-tonne shovel. “In this work, our generator forms the backbone of the construction site, it supplies all electrical machines with energy”, says a proud Max Aerts of supplier Dutch Energy Solutions (DENS). “Charging infrastructure is the major challenge of the electrified construction site. And we have a solution for it”.

The generator he developed with his start-up company in Helmond runs on Hydrozine, better known as formic acid. This is a liquid hydrogen carrier, which has an important advantage over gaseous hydrogen: being that no compressor or heavy pressure tanks are required for storage.

Hydrozine contains 53 grams of hydrogen per liter and can be produced by adding CO2 after electrolysis of water. The generator developed by DENS is equipped with a fuel cell. After the generator has removed the hydrogen from the formic acid, this fuel cell turns it into clean electrical energy. “The process is similar to putting a Mentos in a bottle of Coke” says Aerts.“The gas that is released when it starts to bubble is captured and converted into electricity by the fuel cell”.

Refueling is easy. Formic acid is a liquid fuel that simply comes to the construction site in plastic tanks. You just  have to dump it in the 6000 liter tank. The generator from DENS delivers a nominal power of 20kW and has a 60 kWh battery. “If it runs 24 hours a day, it can produce about 480 kWh of clean energy per day.” says Aerts. “That’s enough to run all Voorbij’s equipment.” Urban Mobility Systems (UMS) is involved in the project as a supplier of the battery systems and is responsible for the electrification of the equipment.

Closed carbon circuit

The innovative generator is quite thirsty. Almost a liter of formic acid passes through every minute. This is because a liter of formic acid contains only one fifth of the amount of energy contained in a liter of diesel (10kWh). The waste products released during the process are water vapor and CO2. Nevertheless, the formic acid generator is CO2 neutral, Aerts explains. “You first add CO2 to make hydrozine and then emit it again when you use it. So it is a closed carbon cycle, in which carbon dioxide functions as packaging”.

Further emissions are not involved in the formic acid generator. No nitrogen, sulfur oxide, particulate matter is released and the device runs “whisper quiet”. This is because energy production is not a combustion process, but the result of a chemical reaction.

DENS has big plans for its innovation. The first four generators will be piloted by various construction companies. “But we expect to deliver dozens more this year,”says Aerts.

The ambitions go even further. The company is investigating together with UMS whether it is possible to equip construction equipment with a Hydrozine system. Because then they no longer need to charge the generator, they can simply refuel. This can be an interesting option, especially for heavier equipment. “The reason is, that you would need so many batteries that a mobile Hydrozine drive is more practical, efficient and cheaper, “says Aerts. “so instead of exchangeable battery packs, you get exchangeable Hydrozine packs.” A heavy excavator would be able to work continuously  with such a modular system. The founders of DENS already proved this is possible when they were students at Eindhoven University of Technology. Then they built a formic acid system for a bus for VDL Groep.

Using a Hydrozine generator is more expensive than a diesel generator, the costs per kWh are about twice as high, Aerts estimates. ”However if you include the social costs of particulate matter, CO2 and nitrogen that are being released during diesel consumption, it is cheaper. ”He expects costs to fall sharply as the scale of the market for electrical construction equipment grows and CO2 capture becomes more common. “This can become significant, especially with heavy equipment, because Hydrozine is a much more efficient energy carrier than hydrogen.''


Dutch Energy Solutions (DENS) was founded five years ago at Eindhoven university of Technology as Team FAST. This student team, in collaboration with VDL, built a concept system for a bus in which an electric motor was fueled with energy by means of formic acid. At the end of this project, the team further developed the system into a stationary generator for construction sites. This was tested as a generator at a BAM infrastructural construction site during the construction of the N211 near Poeldijk, the first CO2 negative road in the Netherlands.

In 2018, the student team continued as an independent start-up at the Automotive campus in Helmond.

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