SUNTRACKER

A novel hybrid process for production of cyclohexanone oxime and high temperature hydrogen production using solar energy

This study examines the performance of a gas-cooled nuclear power plant with closed Brayton cycle (CBC) combined with an organic Rankine cycle (ORC) plant, as well as the irreversibility within the system. Individual models have been developed for each component, through applications of the first and second laws of thermodynamics. The overall system performance is then analyzed by employing individual models and further application of thermodynamic laws for the entire cycle, to evaluate the thermal efficiency and entropy production of the plant. The effects of the turbine inlet temperature, compressor pressure ratio, evaporator temperature, and temperature difference in the evaporator on the combined cycle first-law, second-law efficiency and exergy destruction rate are studied. Finally optimization of the combined cycle in a systematic way has been developed and discussed. It was found that the combined cycle first-law efficiency is about 9.5–10.1% higher than the simple CBC cycle. Also, the exergy destruction rate for the GT-MHR/ORC combined cycle, is about 6.5–8.3% lower than that of the GT-MHR cycle.

<div class="htmlview paragraph">The increasing need for higher electrical power levels for military and scientific space purposes has spurred development of energy conversion systems with higher efficiencies than the traditional solar array. Numerous nuclear options are currently under development. These fuels eliminate the need for large deployable solar arrays or concentrators, allow unrestricted pointing and maneuvering, and are inherently less susceptible to natural and threat environments; they are the only viable energy source for outer planetary exploration. Fission reactors are the most desirable nuclear source for electric power levels above 10 kW. Radioisotope sources have been used in conjunction with thermoelectrics up to 1 kWe for planetary exploration. However, for radioisotope systems in the 1 to 10 kWe range, a much higher conversion efficiency is required. For over 15 years, NASA and the Department of Energy (DOE) have been developing closed cycle turbo-alternator (dynamic) power conversion systems for space use. The Air Force and DOE are jointly developing such a system under the Dynamic Isotope Power System (DIPS) program.</div> <div class="htmlview paragraph">Two closed dynamic cycles are being evaluated for use as part of the DIPS system. They are the Closed Brayton Cycle (CBC) which uses an inert (single phase) gas as the working fluid. The other system is the Organic Rankine Cycle (ORC) which utilizes the phase change properties of the working fluid. Each has a significantly different effect on the design of a radiative heat rejection system, primarily because of the temperature variation of the CBC single phase heat rejection versus the nearly constant temperature two-phase (condensing) ORC heat rejection. The heat rejection system plays an important role, since the power conversion efficiency is strongly dependent on the heat rejection temperature. The lower the rejection temperature, the higher the efficiency. However, the radiator area requirement increases as the rejection temperature is reduced. On a weight optimization basis both systems are comparable, however, the ORC system requires more radiator area for the same cycle efficiency. With the design requirement that the radiator be mounted around the circumference of the vehicle, available area is limited. Therefore, the heat rejection system design may not be a clear-cut weight optimization but rather a matter of area reduction at minimum penalty to efficiency and weight.</div> <div class="htmlview paragraph">The paper presents the results of an optimization study performed on the heat rejection system for a space based ORC power system using an isotope heat source. The radiator sizing depends on the heat rejection temperature, radiator configuration, and radiator properties such as the fin effectiveness, emissivity, and absorptivity. The optimization analysis to evaluate the effect of each of these parameters on the system weight and area is presented.</div>

Effects of working fluid and shaft rotation speed on the performance of HTR plants and the size of CBC turbo-machine

Silicon Carbide (SiC) was integrated into an Organic Rankine cycle (ORC) design to enhance its ability to operate at high temperature. Low-grade heat dissipated from large data centres was used to run the modified ORC to generate electrical power. This allowed for a temperature increase of low-grade heat to a temperature capable of improving the power output and efficiency of the turbine used in the ORC. This research demonstrated that energy management can be applied in large centres, 65 MW power can be generated from a 260 MW data centre at a temperature of 150°C and mass flow rate of 476.19 kg/sec. Heat pumps were integrated into the ORC system to boost the temperature of heat rejected from the condenser and making it available for the cycle. Temperature values from 135°C - 270°C were used to optimise the best temperature to achieve a maximum power production in the ORC; 157.5°C showed a maximum output power of 65 MW. A 25% electrical power can be produced from low-grade heat dissipated by data centres by using modified ORC provided the inlet and outlet enthalpies are constant for all data centres.

<div class="section abstract"><div class="htmlview paragraph">Electricity is a fundamental necessity for individuals worldwide, serving as a force driving technological progress hitherto unimaginable. Electricity generation uses diverse methodologies based on available natural resources in a given geographic region. Conventional methods like thermal power from coal and natural gas, water-based hydropower, solar power from the sun, wind power, and nuclear power are used extensively, the former two being the dominant sources. The generation of nearly 70% of the world's electricity is estimated to be from thermal power plants; however, these operations lead to widespread environmental destruction, greenhouse emissions, and the occurrence of acid rain. Conventional thermal power plants run on the Rankine cycle principle of a boiler, a turbine, a condenser, and a pump. A similar method may be used in the Organic Rankine Cycle (ORC) with the use of solar energy, where heat is transferred to the working fluid in the boiler using a heat pipe, a passive heat transfer device. A closed system makes use of Liquefied Petroleum Gas (LPG) as the working fluid in the Organic Rankine Cycle, while acetone serves as the working fluid when used inside the heat pipe. The boiler is constructed to function within the pressure range of 4-7 bar, while the turbine is constructed to function at temperature levels of 150-200°C when optimized for maximum thermal efficiency. In this current research, a refrigerant boiler has been designed incorporating thermal management strategies to optimize efficiency. The rate of heat transfer from the solar collectors was analyzed under various conditions, and it was found that the evacuated tube collectors had temperature efficiencies ranging from 40-60% at various irradiation levels. Technical parameters unique to the solar collectors are an average flux of 500 W/m<sup>2</sup> and a collector efficiency of 65% at the peak of sunlight intensity. The system can also sustain a boiler temperature of 250°C to allow for maximum system working fluid vaporization and pressure generation. The performance of the system was also subjected to different weather conditions, with particular emphasis on temperature variation and the effect on system efficiency. This research offers an insight into the development of solar-powered ORC systems with emphasis on their capability to generate clean and renewable energy. The research can also be applied to enhance the heat management of refrigerant boilers to allow for efficient temperature control and increased overall system efficiency in solar electric energy conversion.</div></div>

The recurrent rises in energy demand and greenhouse gas emissions (GHGs) appeal for effective usage of energy sources. Micro-combined heat and power (micro-CHP) generation is regarded as an efficient replacement to traditional energy systems with distinct electrical and thermal production attributable to the greater energy effectiveness, reduced capacity and to the reduced GHGs. In this context, the Organic Rankine Cycle (ORC) is broadly recognised like a capable system to generate electrical power from solar energy, waste heat or low-quality thermal energy sources, even lower than 90 circ C. The present study aims at examining the performance of a solar driven micro-CHP system for residential buildings using a regenerative ORC. The analysis focuses on modelling, simulation and optimisation of various working fluids (WFs) in ORC to utilise low-temperature heat source from solar thermal collectors for heat and power generation. A detailed parametric study is performed to analyse the impacts of different WFs and operating situations at several temperatures of the hot and cold sources, as well as several temperatures and flow rates of the evaporator heating and condenser cooling WFs, on the system performance and heating and electrical power yields. The outcomes showed significant changes in performance such as efficiency and power extracted by the expander and generator based on the temperatures of each hot or cold sources for all WFs. The work extracted by the expander and the electrical power were within the range for residential building applications, in the range of 1-7 kWe, with an electrical isentropic efficiency of about 60% and cycle efficiency up to 9.8%, for a hot source temperature of 108 circ C. The WFs will operate in the hot source temperature range that would allow the use of a solar flat plate or evacuated tube collectors.

Integration of concentrated multi-junction solar cells with small-scale organic rankine cycle

Energy is crucial for the development of the newest technologies that support human life and its needs, as well as industry and its uses. Due to the growing demand for energy, it is very important to find appropriate and excellent solutions, methods, and technologies in terms of environmental and economic impact. The organic Rankine cycle (ORC) is optimal for power generation in today’s environmental and economic considerations. In this paper, the thermodynamic performance analysis and design of an ORC driven by solar energy for power generation were investigated. This study included the installation of the system for solar energy, where the thermal energy is used as an input for the organic Rankine cycle. Five different systems were developed as follows: basic (ORC), recuperative (ORC), regenerative (ORC), recuperative–regenerative (RR) (ORC), and basic (ORC) with reheat. Also, five different types of working fluids, toluene, R123, R11, n-pentane, and R141b used to compare the effect of changing parameters such as the temperature of the evaporator, temperature of condenser, difference in superheated temperature, and pressure of regenerative and reheat. The RR ORC system using toluene as a working fluid showed the best results for power, efficiency, and cost savings, which were 128.7 kW, 25.83%, and $1872/month, respectively.

A feasibility study has been conducted for an organic Rankine cycle (ORC) system coupled to the exhaust of a Diesel engine generator. The objective of this study was to determine the possible electrical generation of the ORC using the exhaust gas of a 78 kW diesel engine as its energy input. A thermodynamic model was developed to predict the possible electricity generation of the ORC. Using this model it was determined that the preferred working fluid for the ORC was R245ca. The calculated maximum ORC thermal efficiency was 14.3%. The net electrical power generated from the ORC was 5.36 kWe. The ORC would require no additional fuel and would not generate any additional emissions. The most cost-effective and simple means to develop a small packaged ORC system is to high volume production HVAC system components. An ORC system consisting of air conditioning system components, including a scroll expander, yielded a projected ORC efficiency of 10.7%, and a net electrical power of 4.02 kWe. The total capital cost of the ORC system was $2,140 CAD. Three engine usage scenarios were developed, with the time to payback of the initial capital cost of the ORC ranging from 12.8 to 0.58 years, depending on low or high usage.

Small-scale organic Rankine cycle (ORC) systems driven by solar energy are compared in this paper, which aims to explore the potential of power generation for domestic utilisation. A solar thermal collector was used as the heat source for a hot water storage tank. Thermal performance was then evaluated in terms of both the conventional ORC and an ORC using thermal driven pump (TDP). It is established that the solar ORC using TDP has a superior performance to the conventional ORC under most working conditions. Results demonstrate that power output of the ORC using TDP ranges from 72 W to 82 W with the increase of evaporating temperature, which shows an improvement of up to 3.3% at a 100 °C evaporating temperature when compared with the power output of the conventional ORC. Energy and exergy efficiencies of the ORC using TDP increase from 11.3% to 12.6% and from 45.8% to 51.3% when the evaporating temperature increases from 75 °C to 100 °C. The efficiency of the ORC using TDP is improved by up to 3.27%. Additionally, the exergy destruction using TDP can be reduced in the evaporator and condenser. The highest exergy efficiency in the evaporator is 96.9%, an improvement of 62% in comparison with that of the conventional ORC, i.e., 59.9%. Thus, the small-scale solar ORC system using TDP is more promising for household application.

In this study, the thermodynamic and economical design of an organic Rankine cycle with different energy sources in Arak has been investigated. The effect of organic fluids and pinch temperatures on the Rankine cycle performance was analysed. The use of other energy sources such as solar energy, biomass, heat recovery from micro turbine was Discussed and the cost of power generation was calculated. According to the heat required by the Rankin cycle, the solar tower in Arak has been designed and estimated. The output power of the organic Rankine cycle using microturbine is increased by about 20%The highest cost of power generation is the use of microturbine, solar energy, biomass and hot water, respectively.

Energy and economic analysis of geothermal–solar trigeneration systems: A case study for a hotel building in Ischia

The Organic Rankine Cycle (ORC), which generates electric power by using a low temperature heat source, is developed and an experimental study is conducted. A radial turbine and high speed DC generator are also designed and developed in this study. R245fa is adopted as a working fluid, considering the operation conditions of the cycle and its environmental friendly characteristics. Experiments are conducted to analyze the operation characteristics and performance of the developed ORC. The efficiencies of the cycle and turbine, electric power and temperature versus entropy diagram of the developed ORC with respect to the operation condition are investigated through experiments. The factors that influence the efficiency of the developed ORC are analyzed and discussed.

A thermodynamic analysis and a feasibility study on the organic Rankine cycle (ORC) as a waste heat recovery system for a marine diesel engine were carried out. The ORC and its combined cycle with the engine were simulated, and its performance was estimated theoretically using R245fa. A parametric study on the performance of the ORC system was carried out under different temperature conditions of the heat transfer loop and specification of the heat exchanger. According to the thermodynamic analysis, ~10% of the thermal efficiency of the cycle was able to be realized with the low temperature heat source below . The electric power output of the ORC was estimated to be about 4% of the mechanical power output of the engine, considering additional pumps for cooling water and circulation of the heat transfer medium. According to the present study, the electric power generated by the ORC is about 59%-69% of the required power, and it is possible to reduce the fuel consumption under normal seagoing conditions.