دانلود رایگان مقاله انگلیسی تحلیل حسابداری هزینه های گرماسنجی مقایسه ای و ارزیابی کل انرژی تولید شده - الزویر 2018

abstract

This study presents an analysis of a biogas engine-powered cogeneration system using four different thermoeconomic methods. The most important parameter is the thermoeconomic cost of work produced by the gas engine for each method. The aim is to compare the results obtained from each of those methods. The first method is the exergetic cost theory, which introduced the exergetic cost concept to the thermoeconomic field for the first time. An incidence matrix is defined to show the interaction of flows and components within the system. Exergetic cost theory defines the main rules and delivers a result of 110.065$/h for the work produced by the gas engine. A second method, modified productive structure analysis, is applied to the system and cost balance equations are formed for each component. Exergy destruction is clearly defined and tabulated. At the end of the analysis, the cost of gas engine work was found to be 85.536$/h. A third new method described in published literature, Wonergy, is used to determine both the cost of work and the heat utilized in the cogeneration system. Wonergy gives the same thermoeconomic cost for the components which help to produce work. The smallest value obtained was 72.5$/h. The fourth method, SPECO (specific exergy cost), was the final analytical method used on the system. It defines fuel and product rules to obtain auxiliary equations. The thermoeconomic cost of work produced from the gas engine was determined to be 141$/h which was the highest value obtained in comparison to the others.

5. Conclusions

Cost accounting is a procedure to calculate both fuel and product costs for components in power-producing systems. Thermoeconomics gives hints to calculate these costs from an exergy and economics perspective. A cogeneration system produces work and heat. Since work has more importance, determining the thermoeconomic cost of it in detail becomes obligatory. In this study, different methodologies were applied to an existing cogeneration system having 1000 kW of power production capacity. The first method is ECT, which researches the system in a very detailed way. This method views destructions as products and performs its calculations from this perspective. The second method, MOPSA, investigates destructions more clearly as entropy generation units and it determines the cost of the main product, work. On the other hand it gives distinct costs to destroyed exergies. Hence the cost of the work flow from the engine obtained by MOPSA is smaller than that obtained by ECT. The third method, Wonergy, deals with the cost of both work and heat produced by the system. In this manner, this method may be more reasonable for cogeneration systems and it produces the smallest thermoeconomic cost for work generated by the engine. The fourth and last method, SPECO, makes some assumptions from the fuel product rule perspective. It also considers destructions as products, like ECT; however, ECT gives both unit exergoeconomic cost, dealing with exergy, and unit thermoeconomic cost, dealing with exergetic cost, to each flow, and it analyzes the system more rigorously. Thus, SPECO calculations ended with the highest thermoeconomic cost for work flow from the biogas engine.