Low-potential Sources Research Articles

The engine-recoverer of secondary energy thermal sources based on a Curie point effect for magnetic materials

The article discusses one of the most important issues of the fuel and energy complex - the energy efficiency and the most complete use of the flue gases heat. A review of existing technologies for the heat utilization, including some designs of magneto-thermal engines, is carried out, their structural and technical characteristics are considered. A technology is proposed that ensures not only the utilization of exhaust gases from power plants, but also the application in the field of waste management, for example, increasing the energy efficiency of waste incineration technologies. The idea is to use the Curie point effect when designing a recovery engine that utilizes the waste heat of secondary energy sources. The applied potential of using the effect is based on the possibility of utilizing the heat of various secondary energy sources, such as exhaust gases of heat engines, up to low potential sources, since today there are materials that carry out a second-order phase transition already at 20 °C.

Method of calculation and selection of design parameters and operational characteristics of the spiral expander

The paper proposes a method for calculating the main design parameters and operational characteristics of the HPEC using the Helmholtz equations of state. N-pentane, freon R11, and acetone were considered as the working fluid. The calculations were performed using the CoolProp 6.3.0 library. It was found that the most profitable for HPEC operating on the Rankin cycle with low-potential sources is n-pentane. LD expander operation and mass flow rate of the working fluid are calculated. The calculations were performed using the freely distributed open source library CoolProp 6.3.0. The calculations show that the most profitable WF for HPEC running on the Rankin cycle with low-potential sources is n-pentane. It is determined that the increase in costs when the temperature decreases before the SD is due to a decrease in the level of operation of the Lд expander, which in turn depends on the value of the steam enthalpy at the entrance to the ex-pander.

Development of Smart Grid technology for maintaining the functioning of a biogas cogeneration system

The integrated Smart Grid System of harmonization of production and consumption of electric power and heat with the use of heat-pumping power supply of the biogas plant, which uses fermented wort as a low-potential source of power, was developed. A change in the power factor of the cogeneration system, the temperature of local water is predicted by measuring the voltage at the inlet to the inverter, at the outlet from the inverter and voltage frequency. In the engine cooling circuit, the temperature of cooling water at the inlet to the heat exchanger, at the outlet from the heat exchanger, and the return water temperature are measured. It was proposed to estimate a change in the ratio of voltage at the inlet to the inverter and at the outlet from the inverter. Making forestalling decisions to change the power of the heat pump and the number of plates in the heat exchanger of the engine cooling circuit makes it possible to maintain the voltage at the entrance to the inverter and the temperature of the heated local water. The complex mathematical and logical modeling of the cogeneration system, based on the mathematical substantiation of the architecture of the cogeneration system and mathematical substantiation of the maintenance of functioning of the cogeneration system, was performed. Time constants and coefficients of the mathematical models of dynamics regarding the estimation of a change in the power factor of the cogeneration system, temperature of local water, were determined. Functional estimation of a change in power factor of the cogeneration system in the range of 85–95 %, temperature of local water in the range of 30–55 °С at the compensation of reactive power of up to 40 % was obtained. Determining final functional information provides an opportunity to make forestalling decisions on a change in the power of a heat pump and a change in the number of plates in the heat exchanger of the engine cooling circuit to maintain the functioning of the cogeneration system

Estimation of usage efficiency of freon-steam turbines in mine energy complexes

Increase of operating efficiency of mine energy complexes is an actual scientific and technical problem. Systems that utilize energy of low-potential sources and have freon-steam turbines are suggested to be included in mine energy complexes. Principles of selection of freons as working fluids in energy systems are suggested in the paper. Usage of some thermal equations of state for defining thermal and physical properties of freons is analyzed. Equation of isentropic process for the thermal Redlich–Kwong equation of state is obtained. Calculation of energy efficiency of a system with a freon-steam turbine for selected variants of usage of working fluids is performed. A calculation method of thermodynamic parameters that are necessary for energy conversion efficiency estimation of specific freons in a system of useful utilization of energy is developed. Analysis of results indicates that usage of ozone-safe and fire-safe freons in energy utilization systems of low-potential sources with a possibility of utilization of additional waste heat, which was not used in the past, allows increasing the operating efficiency of mine energy complexes.

Influence of temperatures of a low-potential source and heat consumer on the efficiency of a heat pump

The article describes the experimental setup for testing a heat pump and the results of its operation at various temperatures at its inlet and outlet. An actually task is to study the operation of a heat pump under various boundary conditions, which are determined from the phase transition temperature in the evaporator and condenser. These temperatures depend on the temperature in the evaporator of a low-potential source of heat (the lower source is water, air, etc.) and the temperature in the condenser of a high-potential source of heat (the upper source is a consumer). The main indicator of the efficiency of the heat pump is the coefficient of performance. To determine the reliable value of the coefficient of performance, tests of compression heat pump were carried out. Refrigerant R-142b was used as a working fluid. Based on the experimental data, the dependences of the coefficient of performance on the temperature of the hot and cold heat source are constructed. Also, the coefficient of performance heat pump decreases when the lower heat source decreases.

Development of the schematic thermal circuit of the heat power complex for highly effective use of secondary and renewable energy resources

Development process of a schematic thermal circuit of a heat power complex for highly effective use of secondary and renewable energy resources is considered in this article. Earlier authors developed basic elements of the developed scheme they are warmth transformation block (cascade thermal pump) and warmth accumulation block (accumulators of warmth and cold). The schematic thermal circuit of a heat power complex also contains additional units. It is the module of additional low-potential sources of warmth and cold connection, solar collector, the soil probe (heat exchanger), consumers of heat energy for a heat power complex. Authors defined receivers they are heating, hot water supply, conditioning, freezing and sources of energy are low-potential energy soil/air, solar energy, recuperation of ventilating air, utilization of warmth when conditioning rooms, using a sewer source.

Enhanced Boost Converter Fed Asymmetrical Cascaded -MLI for 3 Induction Motor

modern days more research works are going in the field of a non conventional source based power supply generation for interfacing low potential into high potential. Coupled inductor based Enhanced Boost Converter is proposed in this article. The passive clamp circuit is used to recycle the leakage energy and increase potential gain and less loss. Thus the proposed converter has maximum potential gain and efficiency due to coupled inductor and clamp circuit. This dc-dc converter output is given to hybrid multilevel inverter. The proposed Enhanced Boost Converter fed hybrid multilevel inverter is developed for interfacing low potential dc source into high potential AC.

Energy Conversion by Nanomaterial-Based Trapezoidal-Shaped Leg of Thermoelectric Generator Considering Convection Heat Transfer Effect

Thermoelectric generators (TEGs) can harvest energy without any negative environmental impact using low potential sources, such as waste heat, and subsequently convert that energy into electricity. Different shaped leg geometries and nanostructured thermoelectric materials have been investigated over the last decades in order to improve the thermal efficiency of the TEGs. In this paper, a numerical study on the performance analysis of a nanomaterial-based (i.e., p-type leg composed of BiSbTe nanostructured bulk alloy and n-type leg composed of Bi2Te3 with 0.1 vol % SiC nanoparticles) trapezoidal-shaped leg geometry has been investigated considering the Seebeck effect, Peltier effect, Thomson effect, Fourier heat conduction, and surface to surrounding irreversible heat transfer loss. Different surface convection heat transfer losses (h) are considered to characterize the current output, power output, and thermal efficiency at various hot surface (TH) and cold surface (TC) temperatures. Good agreement has been achieved between the numerical and analytical results. Moreover, current numerical results are compared with previous related works. The designed nanomaterial-based TEG shows better performance in terms of output current and thermal efficiency with the thermal efficiency increasing from 7.3% to 8.7% using nanomaterial instead of traditional thermoelectric materials at h = 0 W/m2K while TH is 500 K and TC is 300 K.

Use of low potencial wastewater heat

The article points out that exhaustion of fossil stocks of fuel and negative impacts of fuel burning on environment determined a significant interest in technologies of heat utilization of low-potential sources in many developed countries of the world. Therefore the solution of the problem of using heat utilization technologies of low-potential sources will be of great importance for preserving people's habitats. In Russia, the most promising area of using unconventional energy sources is heat supply systems of houses and buildings. The conducted analysis shows that one of the effective directions of energy saving is heat pump systems of heat supply, using the most available low potential heat source of flooded massif of soil. It is noted that a huge energy potential of water pumped from closed mines is practically unused because of considerable distance of heat consumers from water purification complexes.

Concerning utilization of heat from low-potential sources

The possibility of using R245fa and n-pentane in the Rankine cycle to convert the heat of low-potential sources into electrical energy is analyzed. A multistage axial-type turbine is considered as a drive of an electric generator. The influence of initial pressure of working fluids on the efficiency of the expansion process is determined. The algorithm and characteristics of thermal calculation of the turbine are given.

Efficiency of using heat pumps with various refrigerants in real steam turbine power units with PT-80 and T-250 turbines

Prospects for increasing the efficiency of heat and electric energy-generation and heat-and-power supply at thermal power plants obviously draw attention to such modern and innovative technologies as heat pumps. Heat pumps allow efficient redistribution of energy flows. The abundance of low-potential heat carriers and heat sources in the cycle arrangement of the thermal power plants operation requires modernization of production and increase of the fuel heat utilization factor, therefore, reduction of specific fuel consumption for the production of heat and electricity. This paper analyzes the influence and practicability of introducing heat pumps into the heating circuit of the return water of the heat network of power units with PT-80 and T-250 turbines. Heat pumps of various configurations provide invariant energy conversion factor and efficiency. To assess energy and economic efficiency, modeling of the operation of power units and calculation of heat pump circuits for various refrigerants are performed. The economic effect is represented in quarterly cash savings of operating costs.

Integrated Simulation of the Gas-Turbine Cogeneration System Operating on the Biogas Fuel

The integrated system of a change in the pipeline water temperature was suggested to measure the reverse pipeline water temperature and the gas temperature to maintain the operation of biogas plant using the thermal pump that uses the fermented wort as a low potential energy source. For this purpose, we developed the architecture of gas-turbine cogeneration system that is based on the integrated dynamic subsystem that includes the biogas plant, the heat pump, the gas turbine cogeneration plant and the heat utilization plant. Other units that are included into the composition of gas turbine cogeneration system are the discharge and charge units and functional efficiency estimation unit that interact in agreement with the dynamic subsystem. Reference and functional estimates of a change in the temperature of pipeline water were obtained on the basis of mathematical simulation of the dynamics of heat utilization plant. Control systems of the working capacity and the identification of the state of heat utilization plant were developed using the suggested mathematical description. The discharge-charge of biogas plant, the fermented wort draining and the loading of fresh material maintain the charge -discharge of gas turbine cogeneration system. Decision making after a change in the number of plates of the heat utilization plant allows for the coordination of production and consumption of the electric energy and the heat. It results in the decrease of the cost price of energy production by 20 to 30 % with an increase in the marketable value of the biogas plant by 15 %.

Multi-fuel mini power plant with low-boiling working body based on Tverskoy rotary steam engine

The article presents the results of the development of a multi-fuel mini-power plant with a low-boiling working body based on a rotary steam engine. The description of the structural scheme, design, operating modes, simulation model in MATLAB-SIMULINK are given. The mini-power plant works with both any type of fuel as well as low-potential sources of thermal energy, including thermal solar radiation.

IMPLEMENTATION OF AN INTEGRATED SYSTEM OF INTERMITTENT HEAT SUPPLY FOR EDUCATIONAL INSTITUTIONS

A review of the current world state of application of various heat supply regimes for public buildings is conducted. The efficiency analysis of the use of various renewable energy sources in combined heat supply systems is analyzed. An integrated heat supply system with successive heating of the coolant from low-potential renewable sources of heat (solar system) to high-temperature traditional heat sources (gas and pellet boilers) is developed. A mathematical model of the integrated heat supply system using renewable sources of heat is proposed. This model can be used to simulate the processes of heating rooms in the intermittent heat supply mode. The dynamics of heating of premises with various heating devices: with natural convection (radiator) and forced convection (fan coils) is carried out. During the heating season (2016–2017), the operation modes of integrated systems of alternative intermittent heat supply (ISAIHS) are studied. These studies are extremely relevant for solving the issues of rational use of energy resources. The proposed solutions show that the most effective use of renewable sources of heat can be only in an integrated approach to solving this issue. Also it should be noted the interaction of ISAIHS components: the heat source – the heating system – the characteristics of the building – the operating modes of the premises. As a result of the research, the boundaries of the effective use of various heat generators in ISAHS are established. The influence of the type of heating devices and insulation of internal walls on the effectiveness of ISAIHS operation is revealed. The full-scale tests of a pilot installation of an integrated heat supply system are carried out. The obtained results will help to use heat sources more efficiently with a two-period operation regime for new houses. This can be used to improve the energy efficiency of existing buildings.

Heat pump coefficient of conversion and power on off-nominal modes

The article considers the variation of heat pump (HP) compression parameters which define its effectiveness: power and coefficient of conversion (μ) on off-nominal modes of operation. Taking into account that the parameters of low-potential sources of heat for HP change, the demand for thermal energy also changes; study of HP operating on off-nominal modes is relevant. To analyze the operating process on partial power modes of HP, a reciprocating compressor is used. The following options are examined by authors as conditions of HP transitioning to the off-nominal mode: change in temperature of water at the condenser inlet; change in flow rate of water passing through the condenser, change in flow rate of the working medium. Based on the analysis of relationships for determining the coefficient of conversion and power consumed by HP, it is shown that these parameters change if HP transitions to off-nominal mode. The increase of temperature entering the condenser leads to decrease in μ, and with temperature decrease μ increases. Decrease in flow rate of water cooling the condenser moves the beginning point of compression of the working medium to higher moisture region and reduces the efficiency of the compressor. Working medium flow rate decrease virtually does not affect the Carnot cycle efficiency and μ decreases because of rising moisture of gas.

Use of infrastructure of combined heat and power plant for utilization of snow on the example of Ulyanovsk

It is shown that along with development of a heat and electrical energy on combined heat and power plants there is a possibility of implementation of the engineering procedures necessary in municipal economy, one of which is utilization of the snow and ice weight deleted during the winter period from city streets. New technologies for utilization of snow with use of low-potential sources of warmth at combined heat and power plant are offered. Scientific reasons are carried out them and comparative cost effectiveness analysis of developed technologies is made.

TWO-STAGE HEAT PUMPS FOR ENERGY SAVING TECHNOLOGIES

The problem of energy saving becomes one of the most important in power engineering. It is caused by exhaustion of world reserves in hydrocarbon fuel, such as gas, oil and coal representing sources of traditional heat supply. Conventional sources have essential shortcomings: low power, ecological and economic efficiencies, that can be eliminated by using alternative methods of power supply, like the considered one: low-temperature natural heat of ground waters of on the basis of heat pump installations application. The heat supply system considered provides an effective use of two stages heat pump installation operating as heat source at ground waters during the lowest ambient temperature period. Proposed is a calculation method of heat pump installations on the basis of groundwater energy. Calculated are the values of electric energy consumption by the compressors’ drive, and the heat supply system transformation coefficient µ for a low-potential source of heat from ground waters allowing to estimate high efficiency of two stages heat pump installations.

Prediction of Acid Mine Drainage (AMD) and Metal Release Sources at the Küre Copper Mine Site, Kastamonu, NW Turkey

Waste and lithological rocks were subjected to aqueous leaching, acid base accounting (ABA), and net acid generation (NAG) tests, and detailed mineralogical investigations were conducted to predict acid mine drainage (AMD) formation at Turkey’s largest historical copper deposits. The field water chemistry from springs and seeps on the mine site were compared with the static and long term aqueous leaching test results. During the ABA, NAG and long term paste pH tests, ore rich and ore bearing wastes showed a paste pH <4, implying their acid generating nature. The relationship between net neutralization potential and acid producing potential revealed that waste rocks with a low sulfur content were generally low potential sources of AMD. Consistent with the static test results, aqueous leaching tests revealed that greater concentrations of Fe, Cu, Zn, Ni, Pb, Cd, Co and As were released from the wastes rich in pyrite. The test methods all generally agreed that the ore-rich wastes (O, P1C, P1D) were the main sources of AMD and metal contamination in the district.

Sliding wear of AISI1040 steel at different thermo chemical surface treated conditions

This work aims to investigate the sliding wear of pack borided AISI1040 steel, carried out at 1000°C for 12 hours with Na2B4O710H2O as low potential born source, using pin-on-disc apparatus as function of applied load and sliding distance at the sliding speed kept constant; compared with gas carburised samples carried at 930°C for 6hours. SEM images confirm that the layer thickness is 160 μm and 400 μm for borided and carburised samples. x-ray diffraction (XRD) pattern affirms the monolayer of Fe2b on borided samples. Wear test results show an increasing trend in the weight loss of the samples against the wear parameters. Delamination and adhesive wear are found as the principal wear mechanisms in borided samples. Borided samples have superior wear resistance than carburised samples and untreated samples.

Sliding wear of AISI1040 steel at different thermo chemical surface treated conditions

This work aims to investigate the sliding wear of pack borided AISI1040 steel, carried out at 1000°C for 12 hours with Na2B4O710H2O as low potential born source, using pin-on-disc apparatus as function of applied load and sliding distance at the sliding speed kept constant; compared with gas carburised samples carried at 930°C for 6hours. SEM images confirm that the layer thickness is 160 μm and 400 μm for borided and carburised samples. x-ray diffraction (XRD) pattern affirms the monolayer of Fe2b on borided samples. Wear test results show an increasing trend in the weight loss of the samples against the wear parameters. Delamination and adhesive wear are found as the principal wear mechanisms in borided samples. Borided samples have superior wear resistance than carburised samples and untreated samples.