Avoidable endogenous/exogenous parts of the exergy destruction in the components of an energy conversion system can be computed by applying advanced exergy analysis. Their calculation is crucial for the correct assessment of the real thermodynamic enhancement achievable by the investigated energy conversion system. This work proposes a new approach to estimate the avoidable exergy destruction rates of system components, being more rigorous compared to the conventional method due to the elimination of the need for the implementation of theoretical assumptions associated with the idealization of processes. An open-source web-based interactive tool was implemented to contrast the results of the conventional advanced exergy analysis to those involving the new approach for avoidable exergy destruction estimation. The comparison was based on the same case study, i.e., a refrigeration system selected from the literature. It was observed that the developed tool can be properly employed for comparing the two approaches within exergy analyses, and the results obtained presented some differences for the compressor and the condenser. Compared to the new approach, the existing methodology of advanced exergy analysis suggests lower values of the avoidable part of exergy destruction, which can be reduced by improving the efficiency of the compressor and the condenser. Moreover, the avoidable parts of exergy destruction, which could be removed within these components by improving the efficiencies of the remaining components, were higher in the case of the application of the existing advanced exergetic analysis as compared with the findings obtained by the proposed approach. These differences were due to the impossibility of the existing advanced exergy analysis to implement complete thermodynamic “idealization” for the condenser and evaporator.
The building is considered together with a heating source in the analysis, it is also proposed to include a human thermal comfort model in this complex system. Regression equations for determining the comfortable room air temperature according to energy and exergy approaches are presented. Human thermal comfort model is included for the first time in the complex building energy system, by determining the comfortable room air temperature, which corresponds to PMV (predicted mean vote), not lower than value for the corresponding building category. The effect of enclosing structures thermal resistance changes on space average radiant temperature and on building category in terms of providing comfortable conditions is estimated. The influence of thermal comfort subjective parameters on primary fuel exergy consumption by the centralized heating system is estimated on the basis of developed model for the Ukrainian conditions.
The article is an analysis of the feasibility of replacing the energy source with heating an office building in Kyiv to the level of a building using energy produced by renewable sources (biomass). The authors assessed the potential of biomass in Ukraine, the logistics routes to ensure uninterrupted supply and the cost of renewable resources. Estimation of necessary investments of transition from energy source to heating, running on natural gas, to energy source, running on biomass (sunflower husk), is given by changing the integral cost of heating costs for three options for thermal protection of the building: non-insulated (existing) building; building, the level of thermal protection of which meets the requirements of Ukraine; a building whose thermal protection level satisfies the requirements of Sweden. In particular, the authors determined that the integral cost of heating when using a boiler on pellets from sunflower husks without improving the thermal insulation of the enclosing structures of the building is significantly lower than when using natural gas as an energy carrier for the production of thermal energy, and the initial cost of an insulated building meets the requirements of Ukraine and the requirements of Sweden when using a natural gas boiler is significantly higher than an uninsulated building with a biomass boiler. The results obtained indicate that there are prospects for scaling buildings with almost zero energy consumption in Ukraine, given the development potential of biomass and the significantly lower unit cost of biomass energy compared to natural gas.
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