How to effectively utilize low and medium temperature energy is one of the solutions to alleviate the energy shortage and environmental pollution problems. In the past twenty years, because of its feasibility and reliability, organic Rankine cycle has received widespread attentions and researches. In this paper, it reviews the selections of working fluids and expanders for organic Rankine cycle, including an analysis of the influence of working fluids' category and their thermodynamic and physical properties on the organic Rankine cycle's performance, a summary of pure and mixed working fluids' screening researches for organic Rankine cycle, a comparison of pure and mixture working fluids' applications and a discussion of all types of expansion machines' operating characteristics, which would be beneficial to select the optimal working fluid and suitable expansion machine for an effective organic Rankine cycle system.

A review of working fluid and expander selections for organic Rankine cycle

Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

Review of organic Rankine cycles for internal combustion engine exhaust waste heat recovery

Thermoelectric generators are solid state energy harvesters which can convert thermal energy into electrical energy in a reliable and renewable manner. Over the last decade, the human body has been considered as a good source of heat to harvest electrical energy through wearable thermoelectric generators. It may become an alternative power generation technique compared to other conventional ones used for many wearable devices. The wearable thermoelectric generator has potential to generate sufficient energy for any wireless sensor nodes (typically power requirements

A review of the state of the science on wearable thermoelectric power generators (TEGs) and their existing challenges

The focus of this study is to review the latest developments and technologies on waste heat recovery of exhaust gas from internal combustion engines (ICE). These include thermoelectric generators (TEG), organic Rankine cycle (ORC), six-stroke cycle IC engine and new developments on turbocharger technology. Furthermore, the study looked into the potential energy savings and performances of those technologies. The current worldwide trend of increasing energy demand in transportation sector are one of the many segments that is responsible for the growing share of fossil fuel usage and indirectly contribute to the release of harmful greenhouse gas (GHG) emissions. It is hoped that with the latest findings on exhaust heat recovery to increase the efficiency of ICEs, world energy demand on the depleting fossil fuel reserves would be reduced and hence the impact of global warming due to the GHG emissions would fade away.

Technologies to recover exhaust heat from internal combustion engines

Internal combustion (IC) engines are the major source of motive power in the world, a fact that is expected to continue well into this century. To increase the total efficiency and reduce CO2 emissions, recently exhaust heat recovery (EHR) based on thermoelectric (TE) and thermal fluid systems have been explored widely and a number of new technologies have been developed in the past decade. In this paper, relevant researches are reviewed for providing an insight into possible system designs, thermodynamic principles to achieve high efficiency, and selection of working fluids to maintain necessary system performance. From a number of researches, it has been found the Rankine cycle (RC) has been the most favourite basic working cycle for thermodynamic EHR systems. Based on the cycle, various different system configurations have been investigated. Accepting a certain design and manufacture cost, a system based on heavy duty vehicle application can increase the total powertrain efficiency by up to 30% (based on NEDC driving condition). To achieve the highest possible system efficiency, design of systemic structure and selections for both the expander and the working fluid (medium) are critical.

A review of researches on thermal exhaust heat recovery with Rankine cycle

https://uhra.herts.ac.uk/bitstream/handle/2299/11848/ATEPaper_EER_ZPeng_12Dec2011.pdf;sequence=2

Zhijun Peng

Papers

A review of researches on thermal exhaust heat recovery with Rankine cycle

Analysis of recoverable exhaust energy from a light-duty gasoline engine