Products & Services


Thermal energy storage – TES

The system functions in a similar way to a battery that powers the Stirling engine. The thermal energy comes into the TES via the receiver. It is this energy from the TES that in turn powers the Stirling engine and lets the PCU create electricity. The material in the TES has excellent thermal energy conserving characteristics and it feeds the Stirling engine the necessary thermal energy required regardless of temporary collar blockage (clouds) as well as for an extended period of time when direct sunlight is no longer available.

Product and sub systems outline and functionality


A parabolic dish (also referred to as a concentrator) has an ideal shape for light concentration onto a single designated area, as an angle correcting system can constantly point (track) the structure in the direction of the sun. The inner surface of a parabolic dish is covered with mirrors that are angled to redirect the sun’s light onto the receiver.


This component’s role is to absorb the concentrated sunlight from the parabolic dish and transfer the captured thermal heat into the Thermal Energy Storage System (TES).

  Power Conversion Unit – PCU

Contained and integrated in the PCU is:

  • V4-90 Stirling engine
  • Oil and cooling system
  • Generator
  • Electrical control system


 V4-90 Stirling engine

At the heart of the PCU will our world leading 33 kW V4-90 Stirling engine. This engine has a thoroughbred background with extensive testing, general supersessions and field test scrutiny under such major industry partners such as; American Ford Motor Company, McDonnell Douglas and US space agency NASA as well as the Swedish submarine manufacturer Kockums who are world leading in Stirling engine design.

The engine designation meaning:
V4-90: V-shape, 4 cylinder with the volume of 90 cubic centimetres per cylinder.

 CHP – Combined heat and power

The V4-90 Stirling engine can also be used as a CHP system, delivering energy from hydrogen gas contained in: Landfill gas, Bio gas and Natural gas. USSI has created a company called Stirling Gas AB. This company that has an enormous amount of synergies with the mother company. USSI will utilise the V4-90 engine for this market. Stirling Gas AB is 100% owned by United Sun Systems International Ltd.