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Abstract:In district heating stations, the heat carrier is circulated between the energy source and consumers by a pumping system. Fluid handling systems, such as pumping systems, are responsible for a significant portion of the total electrical energy use. Significant opportunities exist to reduce pumping energy through smart design, retrofitting, and operating practices. Most existing systems requiring flow control make use of bypass lines, throttling valves or pump speed adjustments. The most efficient of these options is pump speed control. One of the issues in using variable-speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper provides a comprehensive discussion about pump control in heating stations and analyzes the energy efficiency of flow control methods. Specific attention is also given to the selection of motor types, sizing and pump duty cycle. A comparative energy analysis is performed on the hot water discharge adjustment using throttling control valves and variable-speed drives in a district heating station constructed in Romania. To correlate the pumped flow rate with the heat demand and to ensure the necessary pressure using minimum energy, an automatic system has been designed. The performances of these control methods are evaluated in two practical applications. The results show that approximately 20%-50% of total pumping energy could be saved by using the optimal control method with variable-speed pumps. Additionally, some modernization solutions to reduce the environmental impact of heating stations are described. OPEN ACCESSSustainability 2015, 7 5706

Economic operation with minimal energy consumption and low costs of a cooled room or a refrigerant piping system depends largely on the quality and thickness of their insulation. The classical method of insulation rating for refrigeration systems is based on respect of the condition to prevent condensation of water vapours in the air on the surface of insulation or on limiting heat gain, but rarely leads to optimum in terms of a technical and economic criterion. In this paper are described some types of insulation for refrigeration applications and is developed a rating optimization model of these insulations with a high level of generality. It uses multiple dynamic optimization criteria simple or compound, which better reflects the economic and energy complex aspects, present and future. Based on this model were elaborated two computer programs implemented on PC microsystems. Numerical examples will be presented to demonstrate the accuracy and efficiency of the proposed optimization model. These show the good performance of the new model.

Along with the global warming impacts and climate changes, the demands for air conditioning and refrigeration have increased. Therefore, providing cooling by utilizing renewable energy such as solar energy is a key solution to the energy and environmental issues. In this paper are presented theoretical basis and practical applications for cooling technologies assisted by solar energy and their recent advances. The ejector cycle represents the thermo-mechanical cooling system, and has a higher coefficient of performance (COP) but require a higher heat source temperature than other cycles. Based on the thermal COP of each cycle, the absorption cycle which represents the thermal cooling is preferred to the ejector cycle. Next to improving efficiency of solar cooling technologies, research on advanced solar collector is the most important research topic.

The slag and the ash, resulted after the lignite burning in the boilers of Thermal Power Plant located at Timisoara South (Romania), are hydraulically evacuated at the storage facility for slag and ash near village Utvin. Fine ash from compartments of slag and ash deposits that are not covered by water can be driven by air currents, causing pollution. After admission of Romania in European Community, the rules for environmental protection are strictly applied. This paper presents the review on the researches, studies and actions made in order to minimize the pollution due to the slag and ash storage yard upon the environment.