The NSC-Motor, showed right (short from Isothermal NSC-Motor, NSC = New Stirling engine Concept) is a piston Heat engine based on the NSC-Concept invented and developed from 1998 to 2007, and patented in 2008 by Wilhelm Servis[1] [2]. For the moment, there are three NSC-Motor types developed; PROFIT0, PROFIT1 and PROFIT2 engines. Due to their favourable properties, the NSC-Motors are the subject of various ongoing scientific research.

Parts and working principlesEdit

Simplified sectional drawing of the NSC-Motor type PROFIT1 is shown right, with the specification of its most important parts.

The NSC-Motor transforms produced or existing heat into mechanical work utilizing their highly economical characteristic process.

The heat is supplied directly (internally in the engines PROFIT-device) to the gaseous working medium in the engine (always same or always fresh supplied medium, depends on NSC-Motor Types [2, 4]). That heat is transformed during the engine’s regenerative thermodynamic process cycle into mechanical work (the cycle can be closed or open, depending on the NSC-Motor type too). This process cycle is known as the Isothermal NSC-Process cycle, (short NSC-Process). The residual heat at the end of the process cycle is carried out from working medium (also direct and internal in the engines PROFIT-device) or in case of open cycle extracted through the exchange of working medium. The NSC-Motors do not need an external cooler.

Idealized NSC-ProcessEdit

Comparisson of processes: Diesel, NSC, Stirling (class.)

Simmilar to idealized classic isothermal Stirling-Process[3], the idealized isothermal NSC-Process consists of: two Isotherms, two Isochors and additional of one Isobaric change of state of the gaseous working medium. The Isochoric change of state of the working medium during the process cycle in the NSC-Motor is performed by a hybrid displacer and regenerator [1, 2, 3, 4], and at the same time, NSC-Process cycle is obtaining effect of carnotization (same as in Stirling engines).

Efficiency and work production of NSC-MotorsEdit

According to information supplied by its inventor NSC-Motor belongs to the heat engine group with the highest thermal efficiency and are able, at equal conditions to achieve higher thermal efficiency than Diesel (actual Diesel = Sabathé) - or Otto engines. That is possible because the NSC-Process is an isothermal process cycle and because it can use precooled working medium. Due to facts, that the NSC-Process executes also a very effective isobaric change of a state of the working medium (in the same way as the Diesel process), it generates at equal conditions greater amounts of work than the Diesel cycle or any other process cycle [4].


  1. ^ Servis Wilhelm: „Influence of lowering the cooler temperature on the Stirling engine performance”, Thesis, Doctor Dissertation, Faculty of Engineering, University of Rijeka, Croatia 2006/ 2007 (for complete list of published papers on this topic see p. 165 to 169)
  2. ^ Servis W. & Medica, V.: „Actual and future perspectives of Isothermal NSC-engines”, STROJARSTVO 2009, Zagreb/ Croatia 2009.
  3. ^ Reader G. & Hooper C.: „Stirling engines“, E. & F.N. Spon - London/ New York 1983.
  4. ^ Servis Wilhelm, Medica Vladimir, Korbar Andrej: „New Stirling engine Concept (NSC-Engine) with application of direct heat introduction”, BRODOGRADNJA 1/ 2008, Zagreb/ Croatia 2008.
  • Meadows D. & D.: „Die Grenzen des Wachstums“, Rohwolt Taschenbuch Verlag GmbH, Rheinbeck bei Hamburg 1994.
  • Kolin I.: „Stirling Motor“, Zagreb University publications, Ltd., Zagreb 1991.
  • Servis W. & Medica V.: „Investigation of experimental NSC-engine PROBA3AS for development of the first solar 2 kW-NSC-engine (PROFIT1)”, Proceedings of Energy & Environment, Rijeka/ Croatia 2008.
  • Medica V. & Servis W.: „Numerical analysis of experimental NSC-engine PROBA3AS“, Proceedings of Energy & Environment, Rijeka/ Croatia 2008.