| Strengths & Weaknesses
| Future Development
| Vendors |
Capital costs of Stirling engines are relatively high ($2,000-$50,000/kW), and are generally not cost competitive with other DER technologies. Stirling engines are manufactured in very low quantities which results in the high capital cost. At the high end of the cost range are Stirling engines for very specialized (e.g., space) applications. Developers are working to lower first costs through a combination of design refinements and material substitution.
Reducing the cost of Stirling engine technologies has been a focus of ongoing research due to a number of material-related issues specific to the design architecture. Among these are:
- High temperature heater head assemblies require large surface areas, and must be made from exotic materials that are particularly difficult to machine, braze and weld.
- The cooler section also requires large surface areas to allow for sufficient heat transfer with minimal void volumes.
- The regenerator assembly has a need for very fine mesh heat-transfer matrices that can operate near heater head temperatures, and therefore requires high-temperature materials.
- Shaft-seal assemblies separating the high-pressure hydrogen working space from the lubricated drive train are expensive to machine due to the seal complexity and very tight tolerances.