Review of experimental research on supercritical and transcritical thermodynamic cycles designed for heat recovery application

Supercritical operation is considered a main technique to achieve higher cycle efficiency in various thermodynamic systems. The present paper is a review of experimental investigations on supercritical operation considering both heat-to-upgraded heat and heat-to-power systems. Experimental works are reported and subsequently analyzed. Main findings can be summarized as: steam Rankine cycles does not show much studies in the literature, transcritical organic Rankine cycles are intensely investigated and few plants are already online, carbon dioxide is considered as a promising fluid for closed Brayton and Rankine cycles but its unique properties call for a new thinking in designing cycle components. Transcritical heat pumps are extensively used in domestic and industrial applications, but supercritical heat pumps with a working fluid other than CO2 are scarce. To increase the adoption rate of supercritical thermodynamic systems further research is needed on the heat transfer behavior and the optimal design of compressors and expanders with special attention to the mechanical integrity

Experimental investigation of a cascaded organic Rankine cycle plant for the utilization of waste heat at high and low temperature levels

A power plant with two cascaded organic Rankine cycles (CORC) to exploit waste heat from a 800 kWe combined heat and power plant, fueled by biogas, is designed and tested. Heat from the exhaust gas is utilized with a high temperature organic Rankine cycle (HT-ORC), where toluene is employed as a working fluid. The heat discharged from the HT-ORC as well as heat from the engine coolant and additional heat from the exhaust gas is supplied to a low temperature ORC (LT-ORC) with the working fluid Solkatherm SES36. The design of the CORC and the selection of working fluids is presented, aiming at a maximum plant efficiency, but also complying with environmental, safety and practical issues. Furthermore, plant components and construction details are described. After manufacturing, initial tests are carried out, obtaining thermodynamic conditions that are close to the design of the HT-ORC, where a maximum electrical turbo-generator output of 17.5 kW is measured. The cascading of the low temperature heat sources and the transfer to the LT-ORC is shown as well as the basic operation of the LT-ORC. However, several problems occurred, such as a turbo-generator damage in the HT-ORC, a too high condensation pressure and a low working fluid mass flow rate in the LT-ORC, which are discussed together with proposed optimization measures

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

The development of engine waste heat recovery (WHR) technologies attracts ever increasing interests due to the rising strict policy requirements and environmental concerns. Organic Rankine Cycle (ORC) can convert low medium grade heat into electrical or mechanical power and has been widely recognized as the most promising heat-driven technologies. A typical internal combustion engine (ICE) converts around 30% of the overall fuel energy into effective mechanical power and the rest of fuel energy is dumped through the engine exhaust system and cooling system. Integrating a well-designed ORC system to ICE can effectively improve the overall energy efficiency and reduce emissions with around 2–5 years payback period through fuel saving. This book chapter is meant to provide an overview of the technical development and application of ORC technology to recover wasted thermal energy from the ICE with a particular focus on vehicle applications

Techno-economic survey of Organic Rankine Cycle (ORC) systems

New heat conversion technologies need to be developed and improved to take advantage of the necessary increase in the supply of renewable energy. The Organic Rankine Cycle is well suited for these applications, mainly because of its ability to recover low-grade heat and the possibility to be implemented in decentralized lower-capacity power plants. In This paper, an overview of the different ORC applications is presented. A market review is proposed including cost figures for several commercial ORC modules and manufacturers. An in-depth analysis of the technical challenges related to the technology, such as working fluid selection and expansion machine issues is then reported. Technological constraints and optimization methods are extensively described and discussed. Finally, the current trends in research and development for the next generation of Organic Rankine Cycles are presented

Design, construction and commissioning of an organic Rankine cycle waste heat recovery system with a Tesla-hybrid turbine expander

2011 Fall.Includes bibliographical references.Issues surrounding energy are some of the most compelling subjects in the world today. With human's ever increasing need for energy, production must increase or consumption must be reduced to avoid an unsustainable long-term energy balance. One part of the energy solution is low-temperature Organic Rankine Cycles (ORCs). ORCs can be utilized to produce power in mass quantity from a dedicated heat source such as a geothermal well. ORCs may also be utilized as a waste heat recovery system to generate power from a heat stream that is typically rejected to the environment. Low-temperature waste heat streams are ubiquitous as every internal combustion engine generates 55-75% of its total fuel energy as waste heat. Efficiency of a waste heat recovery ORC system is strongly dependent on condensing temperature and expander efficiency. Condensing temperatures are typically kept low with an evaporative condensing unit. However, water consumption to increase energy production is becoming less tolerated. To provide a means to conduct research around these issues, a waste heat recovery ORC test bed was designed and constructed. This thesis contains information on construction and operation of the test bed with these features: R245fa working fluid, direct dry cooled condensing and a Tesla-hybrid turbine expander

Preliminary experimental comparison and feasibility analysis of CO2/R134a mixture in Organic Rankine Cycle for waste heat recovery from diesel engines

This paper presents results of a preliminary experimental study of the Organic Rankine Cycle (ORC) using CO2/R134a mixture based on an expansion valve. The goal of the research was to examine the feasibility and effectiveness of using CO2 mixtures to improve system performance and expand the range of condensation temperature for ORC system. The mixture of CO2/R134a (0.6/0.4) on a mass basis was selected for comparison with pure CO2 in both the preheating ORC (P-ORC) and the preheating regenerative ORC (PR-ORC). Then, the feasibility and application potential of CO2/R134a (0.6/0.4) mixture for waste heat recovery from engines was tested under ambient cooling conditions. Preliminary experimental results using an expansion valve indicate that CO2/R134a (0.6/0.4) mixture exhibits better system performance than pure CO2. For PR-ORC using CO2/R134a (0.6/0.4) mixture, assuming a turbine isentropic efficiency of 0.7, the net power output estimation, thermal efficiency and exergy efficiency reached up to 5.30 kW, 10.14% and 24.34%, respectively. For the fitting value at an expansion inlet pressure of 10 MPa, the net power output estimation, thermal efficiency and exergy efficiency using CO2/R134a (0.6/0.4) mixture achieved increases of 23.3%, 16.4% and 23.7%, respectively, versus results using pure CO2 as the working fluid. Finally, experiments showed that the ORC system using CO2/R134a (0.6/0.4) mixture is capable of operating stably under ambient cooling conditions (25.2–31.5 °C), demonstrating that CO2/R134a mixture can expand the range of condensation temperature and alleviate the low-temperature condensation issue encountered with CO2. Under the ambient cooling source, it is expected that ORC using CO2/R134a (0.6/0.4) mixture will improve the thermal efficiency of a diesel engine by 1.9%

Experimental study on transcritical Rankine cycle (TRC) using CO2/R134a mixtures with various composition ratios for waste heat recovery from diesel engines

A carbon dioxide (CO2) based mixture was investigated as a promising solution to improve system performance and expand the condensation temperature range of a CO2 transcritical Rankine cycle (C-TRC). An experimental study of TRC using CO2/R134a mixtures was performed to recover waste heat of engine coolant and exhaust gas from a heavy-duty diesel engine. The main purpose of this study was to investigate experimentally the effect of the composition ratio of CO2/R134a mixtures on system performance. Four CO2/R134a mixtures with mass composition ratios of 0.85/0.15, 0.7/0.3, 0.6/0.4 and 0.4/0.6 were selected. The high temperature working fluid was expanded through an expansion valve and then no power was produced. Thus, current research focused on the analysis of measured operating parameters and heat exchanger performance. Heat transfer coefficients of various heat exchangers using supercritical CO2/R134a mixtures were provided and discussed. These data may provide useful reference for cycle optimization and heat exchanger design in application of CO2 mixtures. Finally, the potential of power output was estimated numerically. Assuming an expander efficiency of 0.7, the maximum estimations of net power output using CO2/R134a (0.85/0.15), CO2/R134a (0.7/0.3), CO2/R134a (0.6/0.4) and CO2/R134a (0.4/0.6) are 5.07 kW, 5.45 kW, 5.30 kW, and 4.41 kW, respectively. Along with the increase of R134a composition, the estimation of net power output, thermal efficiency and exergy efficiency increased at first and then decreased. CO2/R134a (0.7/0.3) achieved the maximum net power output at a high expansion inlet pressure, while CO2/R134a (0.6/0.4) behaves better at low pressure

A resorption cogeneration cycle for power and refrigeration

PhD ThesisHeat-driven energy system attracts ever increasing attentions to improve the efficiency of overall energy utilisation by recovering the heat energy such as solar thermal energy, wasted heat from industry and geothermal energy. Adsorption technology is recognised as one of the promising solutions to convert low-grade heat to refrigeration or be used as heat pump. Based on the working principle of this technology, it can promisingly be developed into combined refrigeration and power generation system by integrating an expander in to the system. However, due to the limited research efforts on the system investigation, refrigeration generation by adsorption technology is still immature. The investigation on the working conditions of the system, the selection of proper expansion machine for power generation part of the cogeneration and overall system evaluation are important to be conducted. This study aims to explore the feasibility of integration the adsorption technology with expansion machine for refrigeration and power generation. The proposed cogeneration combines resorption system, which has potentially twice of the cooling capacity compared with conventional adsorption system, integrated with expansion machine to continuously produce refrigeration and power. The design and optimisation methods of the proposed system were studied in order to select the proper resorption working pairs under different heat source conditions. Furthermore, the system performance with and without the optimisation methods were evaluated by the first and second law analysis. Results indicated attractive performance and MnCl2-SrCl2 was stood out as the optimal resorption working pair for the purpose of high refrigeration generation under low grade heat source, when ammonia is the working fluid in the system.Scroll expander was selected as the expander to be explored in this study because of its highest average isentropic efficiency, low cost, low vibration noise, high availability and easy modification from compressor to expander for our special application demand. A lab scale scroll expander test rig was designed, constructed and tested to obtain the performance such as isentropic efficiency and electrical efficiency of a selected scroll machine under various working conditions. An assessment of a case study of the resorption cogeneration system was conducted to evaluate the variation of the power and refrigeration performance with the time. Results indicated that a resorption cogeneration with 25.2 kg MnCl2 and 18.9 kg SrCl2 could potentially produce 1 kW power and 2.5 kW cooling capacity when the cycle time is around 25 minutes.Engineering and Physical Sciences Research Council for the supports through the grants Impact Acceleration Account (EP/K503885/1) -Wasted heat recovery project, LH Cogen (EP/I027904/1) and Global SECURE (EP/K004689/1). The financial support from the Henry Lester trust to support this study is also acknowledged

Biogas engine waste heat recovery using organic Rankine cycle

Italy is a leading country in the biogas sector. Energy crops and manure are converted into biogas using anaerobic digestion and, then, into electricity using internal combustion engines (ICEs). Therefore, there is an urgent need for improving the efficiency of these engines taking the real operation into account. To this purpose, in the present work, the organic Rankine cycle (ORC) technology is used to recover the waste heat contained in the exhaust gases of a 1 MWel biogas engine. The ICE behavior being affected by the biogas characteristics, the ORC unit is designed, firstly, using the ICE nameplate data and, then, with data measured during a one-year monitoring activity. The optimum fluid and the plant configuration are selected in both cases using an “in-house” optimization tool. The optimization goal is the maximization of the net electric power while the working fluid is selected among 115 pure fluids and their mixtures. Results show that a recuperative ORC designed using real data guarantees a 30% higher net electric power than the one designed with ICE nameplate conditions