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SwRI receives $1.8M DOE award to develop linear motor reciprocating compressor for hydrogen

Compression is a major contributor to the cost of hydrogen fueling. Source: Elgowainy et al. Click to enlarge.

Southwest Research Institute (SwRI) will begin work in August on a $1.8-million contract awarded by the US Department of Energy DOE to develop, to fabricate and to test a linear motor reciprocating compressor (LMRC). The contract is one of 10 awarded by DOE for projects that will advance hydrogen production and delivery technologies for this fuel source. (Earlier post.)

In its 2012 Multi-Year Research, Development and Demonstration Plan, DOE notes that hydrogen fueling station compressor flow rates may be 5 - 100 kg/hr and require compression pressures as high as 90 MPa (900 bar). (Consumer vehicles will likely require gaseous hydrogen compressed to 70 MPa to meet acceptable range targets.) At present, hydrogen delivery (which includes compression) and storage is an expensive operation. Capital costs are high, and the equipment used is often inefficient and unreliable, leading to costly routine maintenance, repairs and downtime.

Currently, high-pressure diaphragm compressors are used at hydrogen fueling stations (although small reciprocating and intensifier compressors are also used). Ionic liquid compressors are beginning to be commercialized for use in low-to-moderate flow rate and high-pressure gas compression operations.

The project’s objective is to meet DOE’s goals of increasing efficiency and reducing cost for hydrogen compression, paving the way toward more economical hydrogen storage. The targets are reducing the cost of compression, storage and dispensing (CSD) of hydrogen from central production plants at the forecourt to <$1.60/gge by 2015 and <$0.70/gge by 2020.

DOE analysis shows CSD cost reduction is key to achieving its delivery targets. Source: DOE. Click to enlarge.

The LMRC is based on an SwRI-patented concept of driving a permanent magnet piston inside a hermetically sealed compressor cylinder through electromagnetic winding, thus minimizing mechanical part count, reducing leakage and ensuring better reliability.

  Drawing of magnetic free piston unit from SwRI patent.

The inclusion of a permanent magnet in the free piston (12) results in what is characterized as a “permanent magnet piston”.

An electromagnetic coil (26) is in the sidewall (24) of the cylinder (16). When the electromagnetic coil is connected with AC power, the magnetic piston will move (electromagnetic induction) in two opposing linear directions to provide reciprocating movement within cylinder. The level of AC power may be controlled by a variable speed drive to vary the speed of the piston.

SwRI’s researchers expect the LMRC system will be able to achieve the required compression ratio with efficiency greater than 95%, greatly exceeding current equipment capabilities with efficiencies that are typically only about 73%.

The SwRI design is more efficient than traditional compressors, and thus will require less energy. The simplified design should also be more reliable, requiring less maintenance, and it can easily be modularized for installation in the field.

—Eugene Broerman, SwRI manager of the DOE project


  • US 8534058, “Energy Storage and Production Systems, Apparatus and Methods Of Use Thereof”

  • Amgad Elgowainy, Krishna Reddi and Marianne Mintz (2014) “Hydrogen Delivery Infrastructure Analysis” 2014 DOE Hydrogen and Fuel Cells Program Annual Merit Review PD014



Its great to get some solid-ish figures for distribution and compression, including efficiencies, as I and some of the guys were noodling it without much luck in several threads.
I realise that these are projections, not achievements, but fuel cells and hydrogen technology has a great record of having met or exceeded targets, they aren't going to be talking about stuff they have not got a very good idea of how they are going to do, and some of the projections like $1.60gge for 2015 are acceptable and right around the corner.

Being a nerd not a businessman I am as much or more interested in the 95% compression efficiency, which again is projected but we were rather unsuccessfully trying to work out.

On the 'projections' question it seems likely that Linde with their ionic compressors which they are starting to produce in series are likely to have hit better efficiency than the mechanical seals etc that are the likely means assumed if you just go by Wiki etc info on compression, although I have not as yet come across proper data.

Its all good, and getting better compression for hydrogen does not take away anything from efforts to increase battery specific energy etc.

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