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The paper presents a new proposal of a discrete event simulation (DEVS) model for heat transfer in an enclosure. To our knowledge this is the first proposal in this direction, therefore the model is not comprehensive (has no windows, no ground coupling,etcetera). It is a first step of DEVS into the heat transfer in buildings. The model presented is just one possible implementation for a single thermal zone, although it has been designed to be used in multi-zone models. Common methods like CTF (conduction transfer functions) or RTF (response transfer functions) cannot be used. Instead it employs the successive transition state formulation for the 1D conduction heat transfer through multi-layered walls. An example test room has been calculated and the results compared with software that uses well known methods (CTF,RTF). Finally the DEVS model has been tested with a random convective internal-load signal.Keywords: Successive state transition method, Building energy simulation, Discrete event simulation, DevsNumber of boundary conduction elements of the i-zone, equal as well to the number of its boundary surfaces

The large amount of recoverable heat from CO2 refrigeration systems has led UK food retailers to examine the prospect of using refrigeration integrated heating and cooling systems to provide both the space heating and cooling to food cabinets in supermarkets. This study assesses the performance of a refrigeration integrated heating and cooling system installation with thermal storage in a UK supermarket. This is achieved by developing a thermal storage model and integrating it into a pre-existing CO2 booster refrigeration model. Five scenarios involving different configurations and operation strategies are assessed to understand the techoeconomic implications. The results indicate that the integrated heating and cooling system with thermal storage has the potential to reduce energy consumption by 17-18% and GHG emissions by 12-13% compared to conventional systems using a gas boiler for space heating. These reductions are achieved despite a marginal increase of 2-3% in annual operating costs. The maximum amount of heat that can be stored and utilised is constrained by the refrigeration system compressor capacity. These findings suggest that refrigeration integrated heating and cooling systems with thermal storage are a viable heating and cooling strategy that can significantly reduce the environmental footprint of supermarket space heating provision and under the adequate circumstances can forsake the use of conventional fossil-fuel (natural gas) boiler systems in food retail buildings.

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