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Abstract

In this article, a comparison of economic effectiveness of various heating systems dedicated to residential applications is presented: a natural gas-fueled micro-cogeneration (micro-combined heat and power – μCHP) unit based on a free-piston Stirling engine that generates additional electric energy; and three so-called classical heating systems based on: gas boiler, coal boiler, and a heat pump. Calculation includes covering the demand for electricity, which is purchased from the grid or produced in residential system. The presented analyses are partially based on an experimental investigation. The measurements of the heat pump system as well as those of the energy (electricity and heat) demand profiles in the analyzed building were conducted for a single-family house. The measurements of the μCHP unit were made using a laboratory stand prepared for simulating a variable heat demand. The overall efficiency of the μCHP was in the range of 88.6– 92.4%. The amounts of the produced/consumed energy (electricity, heat, and chemical energy of fuel) were determined. The consumption and the generation of electricity were settled on a daily basis. Operational costs of the heat pump system or coal boiler based heating system are lower comparing to the micro-cogeneration, however no support system for natural gas-based μCHP system is included.
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Abstract

At present, with the increase of production capacity and the promotion of production, the reserves of most mining enterprises under the original industrial indexes are rapidly consumed, and the full use of low-grade resources is getting more and more attention. If mining enterprises want to make full use of low-grade resources simultaneously and obtain good economic benefits to strengthening the analysis and management of costs is necessary. For metal underground mines, with the gradual implementation of exploration and mining projects, capital investment and labor consumption are dynamic and increase cumulatively in stages. Consequently, in the evaluation of ore value, we should proceed from a series of processes such as: exploration, mining, processing and the smelting of geological resources, and then study the resources increment in different stages of production and the processing. To achieve a phased assessment of the ore value and fine evaluation of the cost, based on the value chain theory and referring to the modeling method of computer integrated manufacturing open system architecture (CIMOSA), the analysis framework of gold mining enterprise value chain is established based on the value chain theory from the three dimensions of value-added activities, value subjects and value carriers. A value chain model using ore flow as the carrying body is built based on Petri nets. With the CPN Tools emulation tool, the cycle simulation of the model is carry out by the colored Petri nets, which contain a hierarchical structure. Taking a large-scale gold mining enterprise as an example, the value chain model is quantified to simulate the ore value formation, flow, transmission and implementation process. By analyzing the results of the simulation, the ore value at different production stages is evaluated dynamically, and the cost is similarly analyzed in stages, which can improve mining enterprise cost management, promote the application of computer modeling and simulation technology in mine engineering, more accurately evaluate the economic feasibility of ore utilization, and provide the basis for the value evaluation and effective utilization of low-grade ores.
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