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Number of results: 13
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Abstract

The policy of sustainable development seeks to improve energy efficiency of industrial equipment. Efforts to improve energy efficiency also apply to the paint shops, where the recovery of waste heat is sought. The main source of a large amount of low-temperature waste heat in the paint shop is the spray booth. The second place where a large amount of low temperature waste heat is released is the room where the compressed air is prepared. Low energy efficiency of air compressors requires a large electric power supply. As a result, the emitted large heat fluxes become waste energy of the technological process. Heat is equivalent to up to 93% of the electric power supplied in the air compression process. There are solutions for recovering heat from compressors coming from the oil cooling water, but then the waste heat from the cooling of the compressed air and from the electric motor is released into air in the room. A method for recovering low-temperature waste heat from the air preparation room by means of an air-source heat pump has been proposed. An energy balance of the air compression and dehumidification process for the paint shop was made. A Matlab’s built-in numerical model includes air compressor and dehumidifier, heat recovery and accumulation for the purposes of use in the spray booth. A simulation experiment was carried out on the effectiveness of heat recovery from the air preparation room. The use of combined energy management in paint shops was proposed.
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Abstract

The purpose of this article was to discuss the use of adsorption chillers for waste heat recovery. The introduction discusses the need to undertake broader measures for the effective management of waste heat in the industry and discusses the benefits and technical problems related to heat recovery in industrial plants. In addition, heat sources for adsorption chillers and their application examples were described. The principle of operation of adsorption chillers is explained in the next chapter. Heat sources for adsorption chillers are indicated and their application examples are described. The above considerations have allowed the benefits and technical obstacles related to the use of adsorption chillers to be highlighted. The currently used adsorbents and adsorbates are discussed later in the article. The main part of the paper discusses the use of adsorption chillers for waste heat management in the glassworks. The calculations assumed the natural gas demand of 20.1 million m3 per year and the electricity demand of 20,000 MWh/year. As a result of conducted calculations, a 231 kW adsorption chiller, ensuring the annual cold production of 2,021 MWh, was selected. The economic analysis of the proposed solution has shown that the investment in the adsorption chiller supplied with waste heat from the heat recovery system will bring significant economic benefits after 10 years from its implementation, even with total investment costs of PLN 1,900,000. However, it was noted that in order to obtain satisfactory economic results the production must meet the demand while the cost of building a heat recovery system shall not exceed PLN 1 million.
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Abstract

The article analyzes the risk factors related to the energy use of alternative fuels from waste. The essence of risk and its impact on economic activity in the area of waste management were discussed. Then, a risk assessment, on the example of waste fractions used for the production of alternative fuel, was carried out. In addition, the benefits for the society and the environment from the processing of alternative fuels for energy purposes, including, among others: reducing the cost of waste disposal, limiting the negative impact on water, soil and air, reducing the amount of waste deposited, acquisition of land; reduction of the greenhouse effect, facilitating the recycling of other fractions, recovery of electricity and heat, and saving conventional energy carriers, were determined. The analysis of risk factors is carried out separately for plants processing waste for alternative fuel production and plants producing energy from this type of fuel. Waste processing plants should pay attention to investment, market (price, interest rate, and currency), business climate, political, and legal risks, as well as weather, seasonal, logistic, technological, and loss of profitability or bankruptcy risks. Similar risks are observed in the case of energy companies, as they operate in the same external environment. Moreover, internal risks may be similar; however, the specific nature of the operation of each enterprise should be taken into account. Energy companies should pay particular attention to the various types of costs that may threaten the stability of operation, especially in the case of regulated energy prices. The risk associated with the inadequate quality of the supplied and stored fuels is important. This risk may disrupt the technological process and reduce the plant’s operational efficiency. Heating plants and combined heat and power plants should also not underestimate the non-catastrophic weather risk, which may lead to a decrease in heat demand and a reduction in business revenues. A comprehensive approach to risk should protect enterprises against possible losses due to various types of threats, including both external and internal threats.
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Abstract

Turbine stages can be divided into two types: impulse stages and reaction stages. The advantages of one type over the second one are generally known based on the basic physics of turbine stage. In this paper these differences between mentioned two types of turbines were indicated on the example of single stage turbines dedicated to work in organic Rankine cycle (ORC) power systems. The turbines for two ORC cases were analysed: the plant generating up to 30 kW and up to 300 kW of net electric power, respectively. Mentioned ORC systems operate with different working fluids: DMC (dimethyl carbonate) for the 30 kW power plant and MM (hexamethyldisiloxane) for the 300 kW power plant. The turbines were compared according to three major issues: thermodynamic and aerodynamic performance, mechanical and manufacturing aspects. The analysis was performed by means of the 0D turbomachinery theory and 3D computational aerodynamic calculations. As a result of this analysis, the paper indicates conclusions which type of turbine is a recommended choice to use in ORC systems taking into account the features of these systems.
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Abstract

This paper presents the origins of marine steam turbine application on liquefied natural gas carriers. An analysis of alternative propulsion plant trends has been made. The more efficient ones with marine diesel engines gradually began to replace the less efficient plants. However, because of many advantages of the steam turbine, further development research is in progress in order to achieve comparable thermal efficiency. Research has been carried out in order to achieve higher thermal efficiency throughout increasing operational parameters of superheated steam before the turbine unit; improving its efficiency to bring it nearer to the ideal Carnot cycle by applying a reheating system of steam and multi stage regenerative boiler feed water heating. Furthermore, heat losses of the system are reduced by: improving the design of turbine blades, application of turbine casing and bearing cooling, as well as reduction in steam flow resistance in pipe work and maneuvering valves. The article identifies waste energy sources using the energy balance of a steam turbine propulsion plant applied on the liquefied natural gas carrier which was made out basing on results of a passive operation experiment, using the measured and calculated values from behavioral equations for the zero-dimensional model. Thermodynamic functions of state of waste heat fluxes have been identified in terms of their capability to be converted into usable energy fluxes. Thus, new ways of increasing the efficiency of energy conversion of a steam turbine propulsion plant have been addressed.
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Abstract

The paper illustrates a case study of fluid selection for an internal combustion engine heat recovery organic Rankine cycle (ORC) system having the net power of about 30 kW. Various criteria of fluid selection are discussed. Particular attention is paid to thermodynamic performance of the system and human safety. The selection of working fluid for the ORC system has a large impact on the next steps of the design process, i.e., the working substance affects the turbine design and the size and type of heat exchangers. The final choice is usually a compromise between thermodynamic performance, safety and impact on natural environment. The most important parameters in thermodynamic analysis include calculations of net generated power and ORC cycle efficiency. Some level of toxicity and flammability can be accepted only if the leakages are very low. The fluid thermal stability level has to be taken into account too. The economy is a key aspect from the commercial point of view and that includes not only the fluid cost but also other costs which are the consequence of particular fluid selection. The paper discusses various configurations of the ORC system – with and without a regenerator and with direct or indirect evaporation. The selected working fluids for the considered particular power plant include toluene, DMC (dimethyl carbonate) and MM (hexamethyldisiloxane). Their advantages and disadvantages are outlined.
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Abstract

This paper provides some information about thermoelectric technology. Some new materials with improved figures of merit are presented. These materials in Peltier modules make it possible to generate electric current thanks to a temperature difference. The paper indicates possible applications of thermoelectric modules as interesting tools for using various waste heat sources. Some zero-dimensional equations describing the conditions of electric power generation are given. Also, operating parameters of Peltier modules, such as voltage and electric current, are analyzed. The paper shows chosen characteristics of power generation parameters. Then, an experimental stand for ongoing research and experimental measurements are described. The authors consider the resistance of a receiver placed in the electric circuit with thermoelectric elements. Finally, both the analysis of experimental results and conclusions drawn from theoretical findings are presented. Voltage generation of about 1.5 to 2.5 V for the temperature difference from 65 to 85 K was observed when a bismuth telluride thermoelectric couple (traditionally used in cooling technology) was used.
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Abstract

In the paper presented are studies on the investigation of the capillary forces effect induced in the porous structure of a loop heat pipe using water and ethanol ad test fluids. The potential application of such effect is for example in the evaporator of the domestic micro-CHP unit, where the reduction of pumping power could be obtained. Preliminary analysis of the results indicates water as having the best potential for developing the capillary effect.
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Abstract

The paper presents the algorithms for a flue gas/water waste-heat exchanger with and without condensation of water vapour contained in flue gas with experimental validation of theoretical results. The algorithms were used for calculations of the area of a heat exchanger using waste heat from a pulverised brown coal fired steam boiler operating in a power unit with a capacity of 900 MWe. In calculation of the condensing part, the calculation results obtained with two algorithms were compared (Colburn-Hobler and VDI algorithms). The VDI algorithm allowed to take into account the condensation of water vapour for flue gas temperatures above the temperature of the water dew point. Thanks to this, it was possible to calculate more accurately the required heat transfer area, which resulted in its reduction by 19 %. In addition, the influence of the mass transfer on the heat transfer area was taken into account, which contributed to a further reduction in the calculated size of the heat exchanger - in total by 28% as compared with the Colburn-Hobler algorithm. The presented VDI algorithm was used to design a 312 kW pilot-scale condensing heat exchanger installed in PGE Belchatow power plant. Obtained experimental results are in a good agreement with calculated values.
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Abstract

The conversion of a waste heat energy to electricity is now becoming one of the key points to improve the energy efficiency in a process engineering. However, large losses of a low-temperature thermal energy are also present in power engineering. One of such sources of waste heat in power plants are exhaust gases at the outlet of boilers. Through usage of a waste heat regeneration system it is possible to attain a heat rate of approximately 200 MWth, under about 90°C, for a supercritical power block of 900 MWelfuelled by a lignite. In the article, we propose to use the waste heat to improve thermal efficiency of the Szewalski binary vapour cycle. The Szewalski binary vapour cycle provides steam as the working fluid in a high temperature part of the cycle, while another fluid – organic working fluid – as the working substance substituting conventional steam over the temperature range represented by the low pressure steam expansion. In order to define in detail the efficiency of energy conversion at various stages of the proposed cycle the exergy analysis was performed. The steam cycle for reference conditions, the Szewalski binary vapour cycle as well as the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery have been comprised.
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Abstract

Basing on the first and second law of thermodynamics the fundamental trends in the Polish energy policy are analysed, including the aspects of environmental protection. The thermodynamical improvement of real processes (reduction of exergy losses) is the main way leading to an improvement of the effectivity of energy consumption. If the exergy loss is economically not justified, we have to do with an error from the viewpoint of the second law analysis. The paper contains a thermodynamical analysis of the ratio of final and primary energy, as well as the analysis of the thermo-ecological cost and index of sustainable development concerning primary energy. Analyses of thermo-ecological costs concerning electricity and centralized heat production have been also carried out. The effect of increasing the share of high-efficiency cogeneration has been analyzed, too. Attention has been paid to an improved efficiency of the transmission and distribution of electricity, which is of special importance from the viewpoint of the second law analysis. The improvement of the energy effectivity in industry was analyzed on the example of physical recuperation, being of special importance from the point of view of exergy analysis.
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Abstract

In order to recover the low grade waste heat and increase system fuel economy for main engine 10S90ME-C9.2-TII(part load, exhaust gas bypass) installed on a 10000 TEU container ship, a non-cogeneration and single-pressure type of waste heat recovery system based on organic Rankine cycle is proposed. Organic compound candidates appropriate to the system are analyzed and selected. Thermodynamic model of the whole system and thermoeconomic optimization are performed. The saturated organic compound vapor mass flow rate, net electric power output, pinch point, thermal efficiency and exergy efficiency varied with different evaporating temperature are thermodynamically analyzed. The results of thermodynamic and thermoeconomic optimization indicate that the most appropriate organic compound candidate is R141b due to its highest exergy efficiency, biggest unit cost benefit and shortest payback time.
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Abstract

The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been high lightened in recent years and have become an increasingly important subject for ship designers and owners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2emissions from ships, and their proposed energy efficiency design index (EEDI) and energy efficiency operational indicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be employed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions. In this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main propulsion machinery is introduced and three possible types of waste heat recovery systems are designed. To calculate the EEDI and EEOI of the given large container ship, two software packages are developed. From the viewpoint of operation and maintenance, lowering the ship speed and improving container load rate can greatly reduce EEOI and further reduce total fuel consumption. Although the large container ship itself can reach the IMO requirements of EEDI at the first stage with a reduction factor 10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI reduction factor to 20% under the reference line value.
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