Experimental and Numerical Study of a Microcogeneration Stirling Unit under On–Off Cycling Operation

Gianluca Valenti, Aldo Bischi, Stefano Campanari, Paolo Silva, Antonino Ravidà and Ennio Macchi
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Gianluca Valenti: Department of Energy, Politecnico di Milano University, Via Lambruschini 4/A, 20156 Milano, Italy
Aldo Bischi: Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, 121205 Moscow, Russia
Stefano Campanari: Department of Energy, Politecnico di Milano University, Via Lambruschini 4/A, 20156 Milano, Italy
Paolo Silva: Department of Energy, Politecnico di Milano University, Via Lambruschini 4/A, 20156 Milano, Italy
Antonino Ravidà: Department of Energy, Politecnico di Milano University, Via Lambruschini 4/A, 20156 Milano, Italy
Ennio Macchi: Department of Energy, Politecnico di Milano University, Via Lambruschini 4/A, 20156 Milano, Italy

Energies, 2021, vol. 14, issue 4, 1-14

Abstract: Stirling units are a viable option for micro-cogeneration applications, but they operate often with multiple daily startups and shutdowns due to the variability of load profiles. This work focused on the experimental and numerical study of a small-size commercial Stirling unit when subjected to cycling operations. First, experimental data about energy flows and emissions were collected during on–off operations. Second, these data were utilized to tune an in-house code for the economic optimization of cogeneration plant scheduling. Lastly, the tuned code was applied to a case study of a residential flat in Northern Italy during a typical winter day to investigate the optimal scheduling of the Stirling unit equipped with a thermal storage tank of diverse sizes. Experimentally, the Stirling unit showed an integrated electric efficiency of 8.9% (8.0%) and thermal efficiency of 91.0% (82.2%), referred to as the fuel lower and, between parenthesis, higher heating value during the on–off cycling test, while emissions showed peaks in NOx and CO up to 100 ppm but shorter than a minute. Numerically, predictions indicated that considering the on–off effects, the optimized operating strategy led to a great reduction of daily startups, with a number lower than 10 per day due to an optimal thermal storage size of 4 kWh. Ultimately, the primary energy saving was 12% and the daily operational cost was 2.9 €/day.

Keywords: micro-CHP; cogeneration; transient operation; mixed integer linear programming; optimal schedule (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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