Abstract
This article presents and validates a dynamic model of a natural gas-run micro-CHP boiler, whose primary mover is a Stirling engine. From a preliminary literature review on the modelling of this kind of devices, and taking into consideration the goal of performing full system simulations, a semi-empirical one is proposed. Specifically, the model consists of the direct application of general mass and energy conservation principles, supported by empirical expressions based on parametric factors that must be determined experimentally. For that purpose, an experimental test-rig was developed, and a full characterization of a Stirling unit was carried out in order to calibrate the model. Unlike other previous models, the one developed throughout this article fully takes into account both the dynamics that occur during the start-up and cool-down periods, as well as the partial load performance of the engine, providing high precision results while maintaining the simplicity required in energy simulation environments. Calculations during the validation phase show that, when operating at normal conditions, the model is able to reproduce the electricity output and the water delivery temperature with errors below 2.4% and 0.9% in any case, respectively; while during a full-length test, the mean errors for the energy exchanges due to fuel input, thermal output and electrical output were 1.4%, 0.4% and 0.1%, respectively.
Published Version
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