Sunpower’s free-piston machines are based on decades of proprietary know-how, trade secrets and patented design features which have evolved into today’s state-of-the-art technology and an array of prototypes.
Sunpower’s free-piston designs are highly differentiated from conventional kinematic Stirling engines that are complicated and expensive to build. Kinematic Stirling engines require lubrication, seals, and mechanical bearings that combine to restrict performance and limit life. Power output is also difficult to change in the kinematic design.
The motivation behind the free-piston concept was to eliminate these complications and deficiencies of the kinematic design. By comparison:
- Sunpower engines are mechanically simpler than kinematic machines.
- Sunpower engines do not require lubrication, seals and mechanical bearings.
- Sunpower designs are thus longer lived and require less maintenance than conventional kinematic machines.
- Sunpower technology makes use of gas bearings, compact linear alternators or motors, and a simple mechanical configuration enabling designs that are smaller, more power dense (more output power per mass), and more efficient than kinematic designs as well as other free-piston Stirling designs.
- Sunpower applies unique electronic controller technology that modulates and controls our free-piston machines, allowing load-matching capability in fields of use.
The combination of these attributes into Sunpower hardware produces results that highlight the advantages of Sunpower technology solutions:
- Demonstrated thermal efficiency up to 40%
- No wear mechanisms in the design, enabling demonstrated lifetime in excess of 10 years, without maintenance.
The benefits of high efficiency, long life and low maintenance directly translate into Stirling cryocooler technology as well.
Sunpower’s position as the world leader in linear free-piston technology is supported by a healthy and evolving intellectual property portfolio. The portfolio currently includes over 48 U.S. patents and 111 related foreign patents.