At the heart of all our products is the paired rotor technology developed by Epicam. The rotors form a rotary displacement device. This is more efficient and scalable than a turbine, which harnesses energy from flow over its blades, it has fewer losses to friction than a reciprocating displacement engine with a piston, and compression ratio is not limited by flex as in a screw or scroll expander.
The unique geometry of the paired rotors, one with lobes and a second with pockets, is protected by 6 worldwide patents.
The rotor pairs create multiple expanding or contracting chambers as they turn, with a complete pocket expansion or contraction occurring in only 90o of rotation. The rotors can retain efficiency when designed to spin at manageable speeds of 1,000-3,000 rpm (allowing use of automotive components).
With very high compression/expansion ratios over very short times and distances, and machined to a high tolerance, the rotors do not touch and are therefore almost frictionless without any lubrication.
All of this results in gas compression or expansion with the following characteristics:
Very low friction
High power density
High compression/expansion ratio
‘Virtual pipelines’ are increasingly used to transport either natural gas or biomethane from production site to the point of use. Typically the gas is compressed to 250 bar, loaded onto trucks, and then depressurised after transport for grid injection or use in CHP.
Significant energy is used to compress the gas to 250 bar, and given the high pressure gradient, it should be possible to recover some of that energy when that pressure is dropped again. (At large scales, turbines are used to recover some energy, but these are too inefficient to work at the scale of virtual pipelines.) Cryofuel Energy systems aims to use paired rotors to harvest energy from the flow of gas from high to low pressure.
Huge amounts of low grade heat are wasted across multiple industries. Although technologies to recover this heat are well established, a lack of matching demand for space heating or hot water makes it uneconomic in most cases. Conversion of low grade heat to electricity is possible using an Organic Rankine Cycle (essentially a fridge in reverse) but development of such systems is hampered by the lack of an efficient, affordable expander that can be scaled down – a niche Cryofuel Energy aims to fill using paired rotor technology.
Small scale liquefaction plants (2-25 tonnes/day) offer many advantages for the efficient distribution of small scale sources of natural gas and methane.
However, plants in this capacity range lack the efficiencies of scale achievable in large scale liquefaction trains, and are thus unattractive on grounds of both energy and operating cost.
Cryofuel Energy Systems is in the early stages of combining paired rotor technology with other best-in- class small scale liquefaction technologies. The patented rotors offer the capability to compress gas efficiently without the lubricants and filters needed with conventional screw compressors, and then to expand or ‘flash’ the gas in a final step while recovering energy for the rest of the process.
While most biogas upgrade plants make use of water scrubbing or membrane technology, one other approach is cryogenic upgrade. Biogas is cooled in three stages, the first to freeze out water, the second to freeze out carbon dioxide and the third to liquefy the remaining methane. This is most advantageous if the biogas source is remote from the gas grid, as the product, liquid methane, is easily transported (while the alternative, compression, would require additional equipment).
Cryofuel Energy Systems is in the early stages of combining its approach to small scale methane liquefaction with the developers of cryogenic biogas upgrading. The result will be the most efficient and cost effective biogas upgrade system on the market, for grid-remote biogas producers, or biogas producers interested in supplying liquid biomethane for the heavy duty transport fuel market.