New approach of decision support method for Stirling engine type choice towards a better exploitation of renewable energies

Stirling engines are constructed with different mechanical configurations namely Alpha, Beta, Gamma and all of them can be powered by any source of renewable energies including biomass, solar energy or even waste heat from industrial sectors. The question that arises is: how can we choose the right type of Stirling engine that best matches our renewable energy source? In the existing bibliography, there is a great lack of an in-depth approach that establishes an objective comparison between the different types of Stirling engine, which leads researchers to make an inappropriate choice of a given configuration for a specific application. Consequently, a decrease in engine output performance can be noted while increasing the engine operating price. In this context, this paper develops a solution to Stirling engine users that will help them choose the suitable configuration for a given energy source. To do this, a non-ideal adiabatic model which takes several thermal and mechanical losses into consideration has been proposed using MATLAB software. The results of the current model have been compared with experimental findings of NASA Lewis Research Center and previous models and the comparison results demonstrate the high accuracy of the present model. The same physical and geometrical parameters were used to analyze the different configurations of Stirling engine by using crank drive mechanism. The results of this work demonstrate that each Stirling engine type is more suitable for a particular application where it provides high performances. The findings show the ability of Alpha configuration to operate with high temperature difference which correspond to waste heat recovery in industrial sectors where the gas temperature reaches high values. Alpha engine can produce high power-volume ratio and efficiency thanks to its low dead volume in working spaces and the separation that exists between its hot and cold sources. Under the same operating conditions, the output power and efficiency of Alpha, Beta and Gamma were 4120 W, 2280 W, 2500 W and 40.19%, 32.13%, 32.95% respectively. Beta and Gamma types have been found to be more suitable for low and medium temperature difference such as biomass and solar energy. Within these temperature ranges, Beta and Gamma types can produce almost the same output power as Alpha machine with less engine pressure requirement since they contain only one power piston. Beta and Gamma types have efficiencies of 17.57% and 18.40% with only mean pressure of 2.6 MPa and 2.7 MPa respectively, while Alpha arrangement provides an efficiency of 20.95% at 3.5 MPa mean pressure. This contributes to a main advantage of Beta and Gamma Stirling engines in terms of sealing process which will decrease the engine construction cost of these types. In addition, the code developed in this work indicates, at its output, the appropriate type for any application based on the user’s input parameters including the temperature of the hot source. This contributes to a new decision support approach allowing the choice of the suitable configuration for a given energy source.