Together, we can fight climate change.
Invest in Airthium

Renewable energy. Guaranteed available.

Low cost seasonal energy storage
Wind farm

What we do

Our mission is to guarantee the availability of low cost solar and wind electricity 24 hours a day, 365 days a year, in every part of the world.

We envision a world powered 100% from renewables, where electricity would be easily accessible and cheaper than today - cheaper than all fossil fuels including nuclear.

To realize this vision, we are building a low-cost seasonal battery that can store renewable energy for years instead of hours, and is up to 100 times cheaper than current solutions, including lithium-ion batteries.

A "low-cost seasonal battery" means we can store solar energy in the summer and deliver it in the winter, while not increasing the yearly average cost of solar energy beyond fossil fuel prices. We can even compensate for a few "years with bad weather" using reserves built during better years. This way, fossil-fired power plants, which are used for backup power today when there is no sun or no wind for long durations, can finally be shut down.

10,000 hours of autonomy

Our system uses ammonia as zero-carbon synthetic fuel. Large scale liquid ammonia tanks cost $0.2/kWh electrical to build, allowing our battery to deliver its rated power for up to 1 full year straight - and still remain economical.

100% recyclable

Our storage system is mostly made of liquid ammonia, molten nitrate salt, water, and steel. We draw on the decades of experience and existing equipment from the fertilizer and CSP industry, with a fully and easily recyclable design.

100x cheaper than Li-ion

Typical systems with 1000 hours of autonomy cost down to $2/kWh to build, representing minor additional cost to solar and wind farms. This makes 100% solar&wind electricity practical, and cheaper than fossil fuels in more locations every year.

100 kW minimum size

The heat engine at the core of our system is a new kind of Stirling engine, with a 100 kW minimum size that fits off-grid scenarios. It can be scaled to GW size with multiple engines on a few shafts, and still benefit from mass manufacturing.

Imagine a future with zero fossil fuels - and no need for nuclear power
Solar plant

Our Technology

Our battery works by storing electricity in the form of renewable ammonia and hot molten nitrate salt, and then converting the stored energy back into electricity. Ammonia is used for seasonal storage whereas molten salt is used for overnight storage. Energy stored in both media is converted back into electricity using our proprietary, high efficiency, low-cost Stirling engine.

Renewable ammonia is a synthetic (i.e. not fossil) fuel made from air, water and renewable electricity, using a so-called fully electric Haber-Bosch process. It is used to fuel our Stirling engine in generator mode. When burned inside our Stirling engine, combustion only emits nitrogen, water, and trace amounts of NOx that are much lower than any current emission regulation worldwide. Ammonia is a century-old industry with 150+ million tons produced annually; we tap into this experience to make our system safe and recyclable.

Molten nitrate salt is a kind of "engineering lava" consisting of sodium and potassium nitrate salts in liquid form. These salts are made industrially from ammonia, rock salt, potash, and limestone. Molten salt is heated to store electricity, and cooled later to convert the heat back into electricity, using our Stirling engine, run in either heat pump or heat engine mode. Such a sub-system is called Pumped Heat Energy Storage (PHES) and has 70% roundtrip efficiency. Molten salt has been used in the concentrated solar power industry for more than 30 years and is easily and fully recyclable at end of life.

In other words, 3 out of 4 energy conversion steps in our systems rely on our Stirling engine. Our technical architecture is the reason why most of our materials are 100% recyclable, with a well-established safety track record, and how we still keep a system with extremely low cost and high efficiency.

Our Company

Airthium was founded in March 2016 by Andrei Klochko. The Company won numerous prizes including Prix Gérondeau by Zodiac Aerospace 2014, Prix des innovateurs by ArcelorMittal 2016 and the Concours Mondial de l'innovation 2016 organized by the French Government. We went through the Y Combinator startup accelerator in the summer of 2017.

Logo Y Combinator
Logo Accelair
Logo Polytechnique
Logo Zodiac Aerospace
Logo Arcelor Mittal
Logo Concours mondial de l'innovation
Logo Université Paris Saclay
Portrait Andreï Klochko
Andreï Klochkomore_vert


Andreï Klochkoclose

Engineering Master's degree and PhD in Plasma Physics from École polytechnique (2007-2014)

Andrei has a deep knowledge of general physics, mechanics (both solid and fluid), thermodynamics, and electromagnetic systems, as well as multiphysics modeling. He built the first Airthium prototype single-handedly.

Portrait Simon Garnotel
Simon Garnotelmore_vert

Multiphysics simulation engineer

Simon Garnotelclose

PhD in Applied Mathematics from Amiens University/Hospital research center

Expert in 3D Navier-stokes and fluid-structure interaction

Portrait Houssam Houssein
Houssam Housseinmore_vert

Multiphysics simulation engineer

Houssam Housseinclose

Engineering Master's degree at Ecole Centrale (2010-2013), Master 2 in pure mathematics from Paris Diderot University

Houssam is currently a PhD student at Sorbonne University and Airthium.

Portrait Franck Lahaye
Franck Lahayemore_vert


Franck Lahayeclose

Previously Sales director EMEA at Intelsat, MSc in Management ICN 2008

Healing our Planet, faster than it is destroyed
Wind farm