Rankine Cycle Power Generation Research Articles

Recommendations for Energy Water Nexus Problems

The chronic water problems in parts of India are probably due mainly to mismanagement. The rolling blackout and brownout problems in the larger Indian cities are due to lack of generation capacity. Since about ninety percent of the world's electricity is generated based on the steam Rankine cycle, environmental water is necessary for cooling, and freshwater is used as the working fluid. Furthermore, electricity is tied to water as part of the bigger water energy nexus phenomena occurring worldwide. China has started and continued with many initiatives to correct problems with water management. Projects do exist where the climatically dry north is being fed water from the wet south. China has water energy nexus conditions occurring too. The review of the scientific literature on studies about the sources of the Ganges, the Yangtze, the Yellow river, the Indus and the Mekong (the drinking water source of about forty percent of the World's population), the glaciers that feed these sources and how they are shrinking with global warming, has yielded a simple policy decision. Mass balance considerations provide the answer that the logical solution of the recent accelerated water changing from solid to liquid on mountain tops, requires dams and storage areas (lakes) to prevent all that freshwater from escaping to the lowlands, and ultimately being discharged into the oceans. One of the other major contributions in this work is to suggest conversion of (old) Rankine cycle generation of electricity to (new) combined gas cycle generation and/or simple gas cycle generation. The combined gas cycle generation can achieve efficiencies of 55–60%, while that of the Rankine cycle power generation languishes around 30%. Less water is required per MW electric power generated for condenser cooling in the combined cycle. The simple gas cycle generation can achieve 40% thermal efficiency on the average and use no water for cooling. There is also the suggestion to upgrade to supercritical power plants due to the advances in power plant technologies. The improved thermal efficiencies gained from this upgrade generate other benefits as well. Another contribution is the suggestion to use seawater for closed system condenser cooling in power plants that are not near the sea or ocean or any large body of freshwater. The open system seawater condenser cooling has been practiced for years throughout the world. This will definitely reduce the demand for freshwater, which could otherwise be used for human consumption or agriculture. Additionally, the rising seas problem locally may be reduced somewhat if enough of the seawater is used.

Techno-economic Study of Carbon Capture from Coal-fired Power Plant Using MEA Assisted by Solar Organic Rankine Cycle for Power Generation

A carbon capture system applied in coal-fired power plant assisted by solar organic rankine cycle(ORC) for power generation is studied; the ORC system is driven by concentrated solar energy for power generation, the heat of condensation is for carbon capture system using MEA applied in coal-fired power plant, which makes thermal efficiency of ORC 100% theoretically. The system guarantees stable operation and high benefit of the coal-fired power plants via avoiding steam extraction from steam turbine. ORC working fluid candidates are selected based on thermodynamic analysis and parameter design of the system. Toluene, octane, silicone oil MDM and cyclohex are four candidate ORC working fluid. Economic analysis and comparison between different carbon capture systems are conducted based on levelized cost of electricity(LCOE), cost of carbon(COC) and net present value(NPV). When carbon capture rate is less than 90%, LCOE of proposed system is higher than that of traditional carbon capture based on steam extraction. COC of new system is higher than that of traditional one, approximately twice. The new system has higher NPV than that of normal one when subsidy electricity price for concentrated solar power(CSP) is higher than 1.18 CNY/(k W·h), otherwise, if subsidy electricity price for(CSP) is lower than 0.82 CNY/(k W·h), traditional system has higher NPV, and it depends on carbon capture rate to decide which system has better economy when subsidy electricity price is between them.

Comparison of Medium-size Concentrating Solar Power Plants based on Parabolic Trough and Linear Fresnel Collectors

This paper compares the performance of medium-size Concentrating Solar Power (CSP) plants based on an Organic Rankine Cycle (ORC) power generation unit integrated with parabolic trough and linear Fresnel collectors. The CSP plants studied herein use thermal oil as heat transfer fluid and as storage medium in a two-tank direct thermal storage system. The performance of the CSP plants were evaluated on the basis of a 1 MW ORC unit with a conversion efficiency of about 24% and by considering different values of solar multiple and thermal storage capacity. The comparative performance analysis of the two CSP solutions was carried out with reference to the direct solar energy availability of Cagliari, Italy (1720 kWh/m2y) on a yearly basis by means of specifically developed simulation models.The results of the performance assessment demonstrate that CSP plants based on linear Fresnel collectors lead to higher values of electrical energy production per unit area of occupied land. The highest specific energy production of CSP plants based on linear Fresnel collectors is about 55-60 kWh/y per m2 of occupied land and it is achieved with solar multiples in the 1.74-2.5 range and storage capacities in the range of 4-12hours. The highest specific production of the solutions based on parabolic trough collectors is about 45-50 kWh/y per m2 of occupied land and is achieved with lower solar multiples (around 1.5-2.3). Owing to their better optical efficiency, the use of parabolic troughs gives better values of energy production per unit area of solar collector (about 180-190 kWh/m2 vs. 130-140 kWh/m2).

LNG 냉열을 이용하는 암모니아-물 복합 재생 동력 사이클의 성능 특성

The ammonia-water based power generation cycle utilizing liquefied natural gas (LNG) as its heat sink has attracted much attention, since the ammonia-water cycle has many thermodynamic advantages in conversion of low-grade heat source in the form of sensible energy and LNG has a great cold energy. In this paper, we carry out thermodynamic performance analysis of a combined power generation cycle which is consisted of an ammonia-water regenerative Rankine cycle and LNG power generation cycle. LNG is able to condense the ammonia-water mixture at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the thermodynamic models, the effects of the key parameters such as source temperature, ammonia concentration and turbine inlet pressure on the characteristics of system are throughly investigated. The results show that the thermodynamic performance of the ammonia-water power generation cycle can be improved by the LNG cold energy and there exist an optimum ammonia concentration to reach the maximum system net work production.

Materials and Processes for Renewable Energy Technologies

This collection of papers is dedicated to the topic ‘‘Materials and Processes for Renewable Energy Technologies’’. The focus is on concentrated solar energy, which provides a source of clean, non-polluting, high-temperature heat for power and fuels production. Current technologies are based on solar receivers that usually operate below 500 C, coupled to steambased Rankine cycles for power generation at 20% peak efficiency. The next generation of technologies will allow for surpassing 1000 C and enable higher efficiencies via Brayton–Rankine combined cycles. Olivares et al. present a thermogravimetric study on promising high-temperature-resistant alloys for application in solar air receivers coupled to gas turbines. Solar thermochemical approaches to splitting CO2 and H2O inherently operateat high temperatures and use the entire solar spectrum, and as such, they provide a thermodynamically favorable path to solar fuels production. Several authors investigate twostep redox cycles, encompassing the solar thermal reduction of a metal oxide followed by its re-oxidation with H2O and CO2 for H2 and CO generation. Allen et al. examine doped ferrite as redox material and analyze its reaction kinetics. Ceria emerges as another attractive redox candidate because of its high oxygen ion conductivity. Ganesan et al. determine the optical properties of ceria when exposed to concentrated solar radiation. Suter and Haussener present a tomography-based methodology to characterize and optimize porous reticulated ceramic materials used in solar power and fuel applications. Solar concentrating technologies offer round-theclock dispatchability of heat and power through the integration of thermal storage and/or hybridization. There is an opportunity for the minerals processing industry to take advantage of these developments and use the same solar concentrating infrastructure as a direct heat source at high temperatures. The candidate processes are the production of metals (e.g., zinc, magnesium, aluminum, and silicon) from their oxide ores by carbothermal reductions. These processes are highly endothermic and are characterized by their concomitant vast emissions of greenhouse gases (GHGs) and other pollutants. The use of solar process heat integrated with thermal storage offers unique potential advantages for GHG avoidance in extractive metallurgical processes. Eglinton et al. assess this potential for the Australian minerals industry. Vishnevetsky et al. describe exploratory experimental studies on the production of aluminum by carbothermal reduction of alumina at vacuum pressures, enabling its vacuum distillation while bypassing the formation of undesired by-products. Tzouganatos et al. experimentally demonstrate the recycling of zinc by clinkering of Waelz oxide and by its carbothermal reduction using a packed-bed reactor driven by concentrated solar energy. Finally, Perruchoud and Fischer describe the production of upgraded metallurgical silicon, which is the preferred feedstock for the preparation of solar grade silicon for photovoltaic cells. These original papers indicate favorable longterm potential of materials and processes for solar technologies, warranting further research, development, and large-scale demonstration.

Exergy Analysis of Solar Photovoltaic/Thermal Organic Rankine Cycle

A solar thermal organic Rankine cycle (ORC) power generation system model established using R245fa as the working fluid and coupled with a solar photovoltaic generator is introduced. Thermal efficiency and exergy efficiency of the model both with and without a heat regenerator are calculated and compared. Results show the solar organic Rankine cycle system with a heat regenerator has higher thermal and exergy efficiency than the system without a heat regenerator, providing better performance in practice. This result provides a basis for further application and improvement of solar photovoltaic and the solar thermal organic Rankine cycle.

<sub></sub>Research on Vehicle Exhaust Waste Heat Power Generation Technology

Vehicle exhaust waste heat utilization can improve automotive vehicle fuel efficiency to optimize energy use and reduce CO2 greenhouse gas emissions to protect the environment. This paper introduces several methods of using engine waste heat, mainly on the Semiconductor thermoelectric power generation technology and the Organic Rankine Cycle power generation technology, and in-depth study on their system structure, principles and key technologies respectively and get important conclusions.

Experimental verification of a rolling-piston expander that applied for low-temperature Organic Rankine Cycle

A kilowatt-sized rolling-piston expander is proposed for low-temperature Organic Rankine Cycle power generation system. The main purpose of this paper is to conduct a dynamic test of the proposed expander. A low-temperature ORC system using R245fa as working fluid is established for the performance evaluation of the proposed expander. In the experimental system, a hot-water boiler is applied to supply a low temperature heat source. A variety of working conditions are achieved by varying the feed pump capacity and the generator load. In these tests, experimental data such as the R245fa flow rate, the temperature of expander inlet and outlet, the pressure of expander inlet and outlet, the output power and rotation speed of the expander are measured and analyzed. The experimental results show that the proposed expander normally runs between 350rpm and 800rpm with a maximum output power of 0.35kW when the heat source temperature is below 90°C. Meanwhile, a maximum expander isentropic efficiency of 43.3% and a stable Rankine cycle efficiency of 5% are also obtained.

Comparison of sub- and supercritical Organic Rankine Cycles for power generation from low-temperature/low-enthalpy geothermal wells, considering specific net power output and efficiency

Electrical power production at low-enthalpy (∼150 °C) geothermal sites is usually realized using an Organic Rankine Cycle (ORC process). This paper presents our analysis of sub- and supercritical processes using propane, carbon dioxide and ten other refrigerants as working fluids. The impact of crucial indicators for optimization, such as specific net power, thermal efficiency and heat input is discussed in detail.The focus was to optimize the thermodynamic loop and the influence of other parameters, such as condensing temperature, minimal temperature difference in the heat exchanger, and internal heat recovery. Simulations showed that at a geothermal fluid temperature of 150 °C, a suitable working fluid such as propane or R143a can increase specific net power output up to 40%.Furthermore, systematic simulations on brine temperatures of 130–170 °C from subcritical to supercritical operation are discussed.Results from this research may also be applicable for electricity generation using waste heat from combined heat and power (CHP) plants or other technical processes.

Investigation of a two stage Rankine cycle for electric power plants

A two stage Rankine cycle for power generation is presented in this paper. It is made of a water steam Rankine cycle and an Organic Rankine bottoming Cycle. By using an organic working fluid with higher density than water, it is possible to reduce the installation size and to use an air-cooled condenser. In order to search suitable working fluids for our application, nine potential candidates from four different organic fluid families and ammonia are tested. The performances of the two stage Rankine cycle operating with those different working fluids are evaluated. The influences of design external temperatures and the steam turbine outlet pressure on the system are analyzed. Optimal points are found at different cold source temperatures and steam turbine outlet pressures for each fluid. System efficiency can also be enhanced by introducing a regenerator for some of the selected working fluids.

ORC for low temperature power generation with low GWP refrigerants

This article presents and discusses the use of low global warming potential (GWP) refrigerants in low temperature Organic Rankine Cycle for power generation using waste heat. The performance has been compared at low waste heat temperatures to current refrigerants and low GWP ones. In this article, energy and exergy analyses have been also presented and compared for the behaviour of the different refrigerants in question. Results showed that the use of low GWP refrigerants results in reduction of waste heat recovery efficiency with more exergy destruction compared to higher GWP working fluids.

Behaviour of ORC low-temperature power generation with different refrigerants

This article presents and discusses the behaviour of low-temperature Organic Rankine Cycle for power generation using waste heat. The performance has been compared at low- and medium waste heat temperatures to organic and non-organic fluids. In this article, energy and exergy analysis have also been presented and compared for the behaviour of the different refrigerants. Results showed that the use of refrigerant mixtures maximises the waste heat recovery and produces power from low- and medium waste heat with less exergy destruction compared to other working fluids.

Utilization of waste heat from GT-MHR for power generation in organic Rankine cycles

Abstract The gas turbine-modular helium reactor (GT-MHR) is currently being developed by an international consortium. In this power plant, circulating helium that has to be compressed in a single or two successive stages cools the reactor core. For thermodynamic reasons, these compression stages require pre-cooling of the helium to about 26 °C through the use of intercooler and pre-cooler in which water is used to cool the helium. Considerable thermal energy (≈300 MWth) is thus dissipated in these components. This thermal energy is then rejected to a heat sink. For different designs, the temperature ranges of the helium in the intercooler and pre-cooler could be about 100 and 150 °C, respectively. These are ideal energy sources to be used in an organic Rankine cycles for power generation. This study examines the performance of a gas-cooled nuclear power plant with closed Brayton cycle (CBC) combined with two organic Rankine cycles (ORC). More attention was paid to the irreversibilities generated in the combined cycle. Individual models are developed for each component through applications of the first and second laws of thermodynamics. The effects of the turbine inlet temperature, compressor pressure ratio, evaporator temperature and temperature difference in the evaporator on the first- and second-law efficiencies and on the exergy destruction rate of the combined cycle were studied. Finally the combined cycle was optimized thermodynamically using the EES (Engineering Equation Solver) software. Based on identical operating conditions, a comparison between the GT-MHR/ORC and a simple GT-MHR cycle is also made. It was found that both the first- and second-law efficiencies of GT-MHR/ORC cycle are about 3%-points higher than that of the simple GT-MHR cycle. Also, the exergy destruction rate for GT-MHR/ORC cycle is about 5% lower than that of the GT-MHR cycle.

Analysis of zeotropic mixtures used in low-temperature solar Rankine cycles for power generation

This paper presents the analysis of low-temperature solar Rankine cycles for power generation using zeotropic mixtures. Three typical mass fractions 0.9/0.1 (Ma) 0.65/0.35 (Mb), 0.45/0.55 (Mc) of R245fa/R152a are chosen. In the proposed temperature range from 25 °C to 85 °C, the three zeotropic mixtures are investigated as the working fluids of the low-temperature solar Rankine cycle. Because there is an obvious temperature glide during phase change for zeotropic mixtures, an internal heat exchanger (IHE) is introduced to the Rankine cycle. Investigation shows that different from the pure fluids, among the proposed zeotropic mixtures, the isentropic working fluid Mb possesses the lowest Rankine cycle efficiency. For zeotropic mixtures a significant increase of thermal efficiencies can be gained when superheating is combined with IHE. It is also indicated that utilizing zeotropic mixtures can extend the range of choosing working fluids for low-temperature solar Rankine cycles.

Design of Rankine Cycles for power generation from evaporating LNG

Of the different ways of using the cold available from the large scale evaporation of LNG the generation of electric power, using the Rankine Cycle, appears the most practical. Fourteen such plants have so far been installed in Japan. The present study was undertaken for a plant at Zeebrugge. Six different cycles using nine different refrigerants and mixtures were examined. The results ( Tables 2 and 3) show the importance of using a heat source with the highest possible temperature. No one refrigerant is ideal for all configurations Environmental and safety considerations also affect the choice of refrigerant.

Pinch Temperatures in Rankine Cycle Power Generation Utilizing Heat Sources of Medium and Small Temperatures Differences

中小温度差熱エネルギ利用発電の例として熱水利用バイナリサイクルとガス・蒸気複合サイクルを取り上げ, 特にピンチ温度に着目してサイクル計算, 伝熱計算, 経済計算を行った. ピンチ温度サイクル性能への影響や熱交換器内での挙動さらにはコストへの影響について多断蒸発サイクルも含めて詳細に検討した. その結果パイナリサイクルと複合サイクルの特性の違いを明らかにし, また, 最適ピンチ温度の決定などを行った.