• Energy Research

To assess the sustainability of waste management scenario with energy recovery, it is necessary to carry out an adequate analysis of all influential criteria. The main problem in the analysis is to determine the indicators that clearly and fully sublimate the most important influential factors. The model for the assessment of the sustainability of waste treatment scenarios based on multi-criteria analysis AHP (analytic hierarchy process) method is developed. The model predicts an increase in the number of indicators, if it found that a selected number of indicators are not sufficient to distinguish between scenarios and new criterion for the selection of indicators: the relevance of the indicator for certain waste treatment. The model is verified in the case study the city of Nis. Four scenarios were selected and examined: business as usual scenario (landfilling of waste) and the other are created as scenarios with energy recovery and recourses preserving: composting organic waste with recycling inorganic waste, incineration of waste and anaerobic digestion of waste. The assessment of the sustainability of waste treatment scenarios was made in several steps. It is found that the best sustainable scenario is composting of organic and recycling of inorganic waste.

Abstract When complex energy systems are analyzed and when a large number of their components is observed, the destruction of exergy related to a single component is dependent on its own properties, but also on the characteristics of other components. The advanced exergy analysis is useful for providing supplementary information on the interaction between the components. It also exposes the real improvement potential related to each component of a system, but also of a system as a whole. In this paper, an existing complex industrial plant with 33 components and 70 streams is analyzed using the first and second level of exergy destruction splitting for the boiler, as a main plant component from the aspect of destroying the useful work. From the total unavoidable exergy destruction 97.28% comes from the internal irreversibility, 2.72% comes from the irreversibilities of other components, while 95.26% of the unavoidable exergy destruction (186.49 kW) comes from the internal irreversibility, and 4.74% from the external irreversibility. The final result of the advanced exergy analysis for the steam generator is the total value of the avoidable exergy destruction as a real potential that can be avoided. It is 16.19% of the total exergy destruction of the component. That is less than the data obtained in the first decomposition level (186.49 kW) merely due to the existence of mexogenous exergy destruction.

Abstract Exergy analysis and exergoeconomics are often used to evaluate industrial energy systems performance from the thermodynamic and economic points of view. While the classical exergy analysis can be used to recognize the sources of inefficiency and irreversibilities, so called advanced exergy analysis is convenient for identifying real potential for thermodynamic improvements of the system by splitting exergy destruction into avoidable and unavoidable parts. In this paper, the advanced exergy analysis is used to identify performance critical components and the potential for exergy efficiency improvement of a complex industrial energy supply plant. This plant is a part of a rubber factory and its role is to provide steam, compressed air and cooling water to the production facilities, as well as hot water for space heating and sanitary use. The plant is first analyzed as is and the avoidable (and the unavoidable) part of exergy destruction is identified for each observed component. Then, the measures for removing the avoidable destruction are defined. Finally, the plant is analyzed as if the measures were implemented and avoidable losses eliminated. Numerical analysis is based on real data, some of which are collected during on site measurements. Large system of nonlinear and linear equations is defined and solved numerically using the Engineering Equation Solver. Results of the presented analysis show the difference in thermodynamic and economic operational parameters of the plant for the cases without and with the efficiency measures implemented, i.e. the current state and the state with the avoidable irreversibilities eliminated. Beside obvious increase of exergy efficiency and enhancement of other thermodynamic parameters, certain improvement in the economy of the plant could be achieved.