Organic Rankine Cycle Machine Research Articles

Machine learning for design and optimization of organic Rankine cycle plants: A review of current status and future perspectives

AbstractThe organic Rankine cycle (ORC) is widely acknowledged as a sustainable power cycle. However, the traditional approach commonly adopted for its optimal design involves sequential consideration of working fluid selection, plant configuration, and component types, before the optimization of state parameters. This way, the design process fails to achieve an optimal design in most cases, since the process relies heavily on empirical judgments. To improve the design process, researchers have been exploring lately the suitability of machine learning techniques. It is however not clear yet if data‐driven designs of ORC plants are practically viable and accurate. To bridge this gap, this article reviews literature studies in the field. Overviews were first presented on the ORC technology and machine learning modeling approaches. Next, studies that applied machine‐learning methods for the design and performance prediction of ORC plants were discussed. Furthermore, studies that focused on ORC machine learning optimizations were discussed. The artificial neural network (ANN) approach was observed as the technique most frequently applied for ORC design and optimization. Additionally, researchers agree in general that machine‐learning methods can achieve accurate results, with significant reductions of computational time and cost. However, there is the risk of using inadequate data size in the machine learning design approach, or insufficient data set training time, all of which can affect accuracy. It is hoped that this effort would spur the practical implementation of machine learning techniques in the future design and optimization of ORC plants, toward the achievement of more sustainable energy technology.This article is categorized under: Sustainable Energy > Energy Efficiency Sustainable Energy > Other Renewables

A PRACTICAL APPROACH FOR TEACHING THE ORGANIC RANKINE CYCLES (ORC) IN AN ADVANCED THERMODYNAMICS COURSE

Higher Education Institutions must consider the most recently developed technologies to increase energy efficiency. A significant share of the heat used in industry is wasted while still being at usable temperature levels and hence a significant energy saving potential is present in this sector. The Organic Rankine Cycle (ORC) is a system that uses low-grade waste or renewable heat to produce electricity and lower grade heat and can be integrated into a variety of applications. In this paper, an introduction to ORCs is presented, and then, a practical example of a laboratory session using an experimental test bench based in this technology in a last year bachelor’s degree course is detailed. A commercial ORC machine was run in the laboratory session, where the students were able to explore its operation through the graphical interface. They applied the main thermodynamic concepts in the interpretation of the behavior and seen the utility of this science in recently developed environmentally friendly technologies. Then, the students simulated a real case based on the valorisation of exhaust gases from an engine installed in a wastewater treatment plant. Students agreed that the combination of both parts in this session is beneficial for their understanding and that ORC machines are a viable solution to control climate change. Keywords:Combined Heat and Power (CHP); Higher Education (HE); applied thermodynamics; laboratory session; experimental setup; real problem solving

The condensing engine: A heat engine for operating temperatures of 100 ℃ and below

The cost-effective utilisation of low-grade thermal energy with temperatures below 150 ℃ for electricity generation still constitutes an engineering challenge. Existing technology, e.g. the organic Rankine cycle machines, are complex and only economical for larger power outputs. At Southampton University, the steam condensation cycle for a working temperature of 100 ℃ was analysed theoretically. The cycle uses water as working fluid, which has the advantages of being cheap, readily available, non-toxic, non-inflammable and non-corrosive, and works at and below atmospheric pressure, so that leakage and sealing are not problematic. Steam expansion will increase the theoretical efficiency of the cycle from 6.4% (no expansion) to 17.8% (expansion ratio 1:8). In this article, the theoretical development of the cycle is presented. A 40 Watt experimental engine was built and tested. Efficiencies ranged from 0.02 (no expansion) to 0.055 (expansion ratio 1:4). The difference between theoretical and experimental efficiencies was attributed to significant pressure loss in valves, and to difficulties with heat rejection. It was concluded that the condensing engine has potential for further development.

Techno-economic assessment for the integration into a multi-product plant based on cascade utilization of geothermal energy

The Organic Rankine Cycle (ORC) is a technology that has reached maturity in cogeneration or waste heat applications. However, due to low thermal efficiency and high capital cost of ORC machines, geothermal-based ORC applications represent only a small percent sharing of the geothermal power capacity worldwide. Several countries have reported a great potential of low- and mid-temperature geothermal energy, representing an opportunity to explore a more efficient ORC integration into non-conventional applications of geothermal energy. One alternative, resembling the polygeneration concept, is known as cascade utilization of geothermal energy, where different energy outputs or products can be obtained at the same time, while improving thermal and economic performance. In this paper, a techno-economic analysis for the selection of small capacity ORC machines and absorption chillers (for ice production), to be integrated into a polygeneration plant that makes use of geothermal energy in a cascade arrangement, is presented. A simple cascade system that consists of three sequential thermal levels, producing simultaneously power, ice and useful heat is proposed, considering typical temperatures of geothermal zones in Mexico. A simple optimization algorithm, based on energy and economic models, including binary variables and manufacturer’s data, was developed to evaluate and determine optimal ORC and absorption chiller units. Results show, firstly, that inconvenience of low thermal efficiency and high capital cost of ORC machines can be overcome. Secondly, that the temperature difference in ORC evaporator strongly influences the overall energy efficiency and the economic profit of the system.

A comparing on the use of Centrifugal Turbine and Tesla Turbine in an application of Organic Rankine Cycle

ABSTRACT This paper aims to compare the use of Centrifugal Turbine and Tesla Turbine in an application of Organic Rankine Cycle (ORC) Machine using Isopentane as working fluid expanding. The working fluid has boiling point below boiling water and works in low-temperature sources between 80-120  C which can be produced from waste heat, solar-thermal energy and geothermal energy etc. The experiment on ORC machine reveals that the suitability of high pressure pump for working fluid has result on the efficiency of work. In addition, Thermodynamics theory on P- h diagram also presented the effect of heat sources’ temperature and flow rate on any work. Thus, the study and design on ORC machine has to concern mainly on pressure pump, flow rate and optimized temperature. Result experiment and calculate ORC Machine using centrifugal Turbine efficiency better than Tesla turbine 30% but Tesla Turbine is cheaper and easily structure. Further study on the machine can be developed throughout the county due to its low cost and efficiency

A Study on Performance comparison of two-size Tesla Turbines Application in Organic Rankine Cycle Machine

This paper aims to study and design of Organic Rankine Cycle (ORC) Machine using Isopentane as working fluid expanding through Tesla turbine. The study on ORC machine expanding through Tesla turbine has result on the efficiency of Tesla turbine. In addition, Thermodynamics theory on isentropic efficiency proved to be a successful method for overcoming the difficulties associated with the determination of very low torque at very high angular speed. By using an inexpensive experiment device and a simple method, the angular acceleration method, for measuring output torque and power in a Tesla turbine is able to predict a tendency of output work. The experiments using two Tesla turbine sizes, the first size is 1.6 bigger than the second one. In comparison with the first size, the tesla turbine can produce power output more than 62% of the second size. Further study on the machine can be developed throughout the county due to its low cost and efficiency.

Heat resources and organic Rankine cycle machines

Heat resources and organic Rankine cycle machines

Power generation with ORC machines using low-grade waste heat or renewable energy

By 2030, global energy consumption is projected to grow by 71%. At the same time, energy-related carbon dioxide emissions are expected to rise by more than 40%. In this context, waste and renewable energy sources may represent alternatives to help reduce fossil primary energy consumption. This paper focuses on the technical feasibility, efficiency and reliability of a heat-to-electricity conversion, laboratory beta-prototype, 50 kW Organic Rankine Cycle (ORC) machine using industrial waste or renewable energy sources at temperatures varying between 85 °C and 116 °C. The thermodynamic cycle along with the selected working fluid, components and control strategy, as well as the main experimental results, are presented. The study shows that the power generated and the overall net conversion efficiency rate of the machine mainly depends on such parameters as the inlet temperatures of the waste (or renewable) heat and cooling fluid, as well as on the control strategy and amount of parasitic electrical power required. It also indicates that after more than 3000 h of continuous operation, the ORC-50 beta-prototype machine has shown itself to be reliable and robust, and ready for industrial market deployment.

Techno-economic comparison of a high-temperature heat pump and an organic Rankine cycle machine for low-grade waste heat recovery in UK industry

This paper presents a comparison of a high-temperature heat pump and an organic Rankine cycle (ORC) plant for the recovery of low-grade waste heat for a UK inorganic chemicals case study. Superficially, the two technologies appear equally suitable for use here; therefore, both technologies are modelled in order to provide data for a comparison in terms of expected technical and economic performance. Both technologies are proven to be feasible in this case study, with the heat pump helping to significantly reduce the natural gas requirement of the plant and the ORC producing a significant net output of electricity. This leads to each technology being attractive from the economic and environmental viewpoints. However, the proposed ORC achieves greater potential greenhouse gas reductions (499 tCO2 eq/year as opposed to 401 tCO2 eq/year) and greater potential cost savings (£69 000/year as opposed to £37 800/year). Therefore, the ORC machine is shown to be the preferred technology in this case. A sensitivity analysis based on continuation of the utility cost trends is performed and shows that the ORC plant would gain in profitability in future years whereas the potential profit of the heat pump system would diminish to almost zero by 2020. Such results suggest that ORCs may be further utilised in future years whilst the use of heat pumps may decline.

Optimization of waste heat utilization in oil field development employing a transcritical Organic Rankine Cycle (ORC) for electricity generation

This study describes the low temperature waste heat exploitation during enhanced crude oil development providing a 600–900 kW continuous electric power supply under deteriorating and oscillating thermal boundary conditions. The aim of this project was to optimize the heat-to-power conversion process by maximizing the net power output employing a transcritical Organic Rankine Cycle (ORC) with R134a as working fluid. Volatile supercritical thermo-physical fluid properties demand a review of heat transfer and expansion procedures. In order to design a comprehensive and dynamic unit configuration, a flexible cycle layout with an adjustable working fluid mass flow is required. The optimization developed a positive heat exchange/pressure correlation for the net power output with reasonable cycle efficiencies of around 10% employing moderate device sizes. Changing ambient temperatures from a winter night with 10 °C to a summer day with 28 °C ambient temperature, on the US West Coast, leads to net power differences of up to 200 kW for an identical cycle configuration. Positive and negative effects result from these temperature oscillations while the heat sink temperature decreases, as does the bottom pressure. Extended available temperature and pressure differences lead to higher power outputs and cycle efficiencies. Considering higher ambient temperatures, the efficiency and power increase per heat transfer performance increase is higher than at low ambient temperatures. For this reason a “large” heat exchanger is more beneficial under warm ambient conditions than under cold ones. In addition, “large” configurations do not easily run the risk of subcritical cycle operation unlike small configurations. It is therefore important to examine the ORC machine performance over a full range of ambients. Considering a likelihood of heat source temperature degradation, an aggressive cycle design does not pay off. The selection of larger heat transfer devices almost equalizes the net power output compared to smaller ones after a heat source temperature deterioration of ∼ 6 K. Sensitivity analyses in the way presented here are an indispensable tool for achieving optimal cycle layout and operation.

Impact of new technologies on future heat exchanger design

Heat recovery technology has featured strongly in most major inductrial energy conservation programmes, and significant penetration of heat exchange equipment into processes, for the express purpose of energy efficiency, has been achieved. Barriers, both technical and economic, still exist however, preventing more widespread adoption of heat exchangers. Problems associated with fouling and corrosion remain, and the temptation to adopt more sophisticated energy recovery methods such as organic Rankine cycle machines had led to some overambitious installations with dubious economic benefits. The prospects for cost-effective low temperature heat recovery are improving due to a combination of developments, including the novel use of materials and new heat exchanger concepts. A number of peripheral aids, in particular improved design procedures including process integration, and the use of artificial intelligence techniques, can help users select appropriate state-of-the-art equipment. In this paper, the role of techniques for enhancing heat (and mass) transfer will be discussed. Process intensification, perhaps normally associated with compact chemical plant unit operations, has, the author believes, an important future role to play in enabling heat exchanger size and costs to be reduced. Enhancement of transport processes, by techniques which are largely established in other heat transfer areas or in other technologies, is a necessary step to achieving compact systems.

Heat recovery—an opportunity for process redesign or a case for retrofitting?

Within many sectors where energy usage is significant, conservation measures may be implemented without recourse to extensive plant or building redesign. This applies to heat recovery in the textile finishing industry, for example. The chemical engineer, however, has considerably greater incentive to redesign his process when faced with the opportunity to incorporate heat recovery equipment. Network analysis techniques tend to encourage the trend towards redesign, and this may spread to other industrial sectors. Are ‘retrofitting’ and redesign incompatible? Both can lead to cost savings, the former generating a more rapid return of possibly lower magnitude. Both provide the engineer with challenges to his technical and managerial skills. It can be argued, however, that most suppliers of heat recovery equipment and systems are structured to meet the demands of ‘retrofit’ business, while potential users in the chemical industry often take the initiative from suppliers in specifying heat recovery plant and technologies. Even so, some of these technologies, notably heat pumps and organic Rankine cycle machines, are not yet making a significant impact. This paper discusses examples which fall within each of the above categories, and comments on the role other energy efficient technologies might play.

Heat recovery—research and development within the European community

The European Community has been involved in research in the field of energy ever since its formation. More recently, major research, development and demonstration programmes directed at energy conservation have been initiated. This paper briefly describes a number of projects in the U.K. concerned with heat recovery in the current 4 year Energy R&D programme, and reviews some of the work of the first programme, completed during 1980. Emphasis is given to heat exchanger developments, although a considerable proportion of the £14 million in the current programme is allocated to heat pumps. Support is also being given to development of organic Rankine cycle machines.