The low-pressure compression/expansion of air is performed in HyPES systems by a rotary compressor/expander module based on an innovative “Co-rotating Scroll” concept with water injection. This technology results from more than 10 years of strong R&D collaboration with our academic partners from the Swiss Federal Institute of Technology Lausanne (EPFL) and the University of Applied Sciences of Geneva (HEPIA), Switzerland.

A Co-rotating (or Spinning) Scroll mainly consists of two eccentric spirals rotating synchronously at the same speed, whose assembly generates several “lunar crescent-shaped” involutes. When the machine rotates in one direction (compressor direction), these involutes move from the periphery to the centre while their volume decreases. Alternatively, when the machine rotates in the opposite direction (expander direction), the involutes move from the centre to the periphery while their volume increases (see the animation).

A Co-rotating Scroll has many advantages compared to an Orbiting Scroll that has one fixed spiral and one orbiting (oscillating) spiral:

• Pure rotational motion, allowing high speed (up to 10’000 rpm) operation and therefore high-power density. A co-rotating scroll compressor can deliver more than 3 times mass flow than an orbiting scroll of equal displacement.
• Low relative speed between the two spirals, allowing high liquid ingestion capability (2-phase processes). Therefore, a substantial amount of water can be injected inside the compression/expansion chambers to control the air temperature and achieve near isothermal processes.
• Oil-free operation
• Low vibration and noise.
• Easy reversibility (Compressor mode and motor mode)

Thus, the Co-rotating Scroll technology developed by Enairys is being deployed in a variety of applications:

• Low pressure air compressors (7 to 15 bare) for various applications, where the scroll module operates only in compressor mode
• Low pressure propulsion units for compressed air-powered boats where the scroll module operates only in motor mode
• Low pressure reversible electro-pneumatic conversion units for Didactic & Experimental Test Setups or for Hydro-Pneumatic Energy Storage (HyPES) systems where the scroll module operates both in compressor and motor modes. A picture of a prototype of such a reversible conversion unit is shown below.