Bottoming cycles for electric energy generation: Parametric investigation of available and innovative solutions for the exploitation of low and medium temperature heat sources

Bianchi, Michele; Pascale, Andrea De

doi:10.1016/j.apenergy.2010.11.013

Cited by 198 publications

(74 citation statements)

References 11 publications

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“…Several alternative methods exist for exploiting heat sources at such low temperatures, including the Stirling Cycle, Organic Rankine Cycle (ORC), and Kalina Cycle. However, Bianchi and De Pascale [3] have identified the Organic Rankine Cycle as the most promising technology for their utilisation. Typical heat sources for the Organic Rankine Cycle include solar, geothermal, biomass and industrial waste heat [4].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of an Organic Rankine Cycle with Adjustable Working Fluid Composition, a Volumetric Expander and a Recuperator

Collings

2017

Energies

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Conventional Organic Rankine Cycles (ORCs) using ambient air as their coolant cannot fully utilize the greater temperature differential available to them during the colder months. However, changing the working fluid composition so its boiling temperature matches the ambient temperature as it changes has been shown to have potential to increase year-round electricity generation. Previous research has assumed that the cycle pressure ratio is able to vary without a major loss in the isentropic efficiency of the turbine. This paper investigates if small scale ORC systems that normally use positive-displacement expanders with fixed expansion ratios could also benefit from this new concept. A numerical model was firstly established, based on which a comprehensive analysis was then conducted. The results showed that it can be applied to systems with positive-displacement expanders and improve their year-round electricity generation. However, such an improvement is less than that of the systems using turbine expanders with variable expansion ratios. Furthermore, such an improvement relies on heat recovery via the recuperator. This is because expanders with a fixed expansion ratio have a relatively constant pressure ratio between their inlet and outlet. The increase of pressure ratio between the evaporator and condenser by tuning the condensing temperature to match colder ambient condition in winter cannot be utilised by such expanders. However, with the recuperator in place, the higher discharging temperature of the expander could increase the heat recovery and consequently reduce the heat input at the evaporator, increasing the thermal efficiency and the specific power. The higher the amount of heat energy transferred in the recuperator, the higher the efficiency improvement.

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Section: Introductionmentioning

confidence: 99%

Numerical Analysis of an Organic Rankine Cycle with Adjustable Working Fluid Composition, a Volumetric Expander and a Recuperator

Collings

2017

Energies

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“…Moreover, even technologies with low conversion efficiencies can be of interest if there is no other use for the excess heat. Bianchi & De Pascale (2011) compared and evaluated five technologies for electricity generation from excess heat with temperatures 200-500°C. The technologies were the organic Rankine cycle (ORC), micro Rankine cycle, Stirling engine systems, thermoelectric generation (TEG) and inverted Brayton cycle.…”

Section: Introductionmentioning

confidence: 99%

Electricity generation from low-temperature industrial excess heat—an opportunity for the steel industry

Johansson

Söderström

2013

Energy Efficiency

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Awareness of climate change and the threat of rising energy prices have resulted in increased attention being paid to energy issues, and industry seeing a cost benefit in using more energyefficient production processes. One energy-efficient measure is the recovery of industrial excess heat. However, this option has not been fully investigated and some of the technologies for recovery of excess heat are not yet commercially available. This paper proposes three technologies for the generation of electricity from low temperature industrial excess heat. The technologies are thermoelectric generation, organic Rankine cycle and phase change material engine system. The technologies are evaluated in relation to each other, with regard to temperature range of the heat source, conversion efficiency, capacity and economy.Because the technologies use heat of different temperature ranges, there is potential for concurrent implementation of two or more of these technologies. Even if the conversion efficiency of a technology is low, it could be worthwhile to utilise if there is no other use for the excess heat.The iron and steel industry is energy intensive and its production processes are often conducted at high temperatures. As a consequence large amounts of excess heat are generated. The potential electricity production from low temperature excess heat at a steel plant was calculated together with the corresponding reduction in global CO 2 emissions.

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“…This can be analysed by the results of the specific advanced exergy analysis presented in Table 5. 13. Table 5.13 shows that the system is more efficient (less exergy destroyed in kJ/kg for all the components) in the endogenous case than in the real case.…”

Section: Advanced Exergy Analysismentioning

confidence: 99%

“…Among these technologies, Organic Rankine Cycles promise high potential [13], therefore, this technology is most widely used in small-scale energy production and industrial applications, i.e. geothermal, biomass, solar thermal power and waste heat recovery (WHR) on industrial processes.…”

Section: Introductionmentioning

confidence: 99%

Study of Organic Rankine Cycles for Waste Heat Recovery in Transportation Vehicles

Pascual¹

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Regulations for ICE-based transportation in the EU seek carbon dioxide emissions lower than 95 g CO 2 /km by 2020. In order to fulfill these limits, improvements in vehicle fuel consumption have to be achieved. One of the main losses of ICEs happens in the exhaust line. Internal combustion engines transform chemical energy into mechanical energy through combustion; however, only about 15-32% of this energy is effectively used to produce work, while most of the fuel energy is wasted through exhaust gases and coolant. Therefore, these sources can be exploited to improve the overall efficiency of the engine. Between these sources, exhaust gases show the largest potential of Waste Heat Recovery (WHR) due to its high level of exergy. Regarding WHR technologies, Rankine cycles are considered as the most promising candidates for improving Internal Combustion Engines. However, the implementation of this technology in modern passenger cars requires additional features to achieve a compact integration and controllability in the engine. While industrial applications typically operates in steady state operating points, there is a huge challenge taking into account its impact in the engine during typical daily driving profiles.This thesis contributes to the knowledge and characterization of an Organic Rankine Cycle coupled with an Internal Combustion Engine using ethanol as working fluid and a swash-plate expander as expansion machine. The main objective of this research work is to obtain and quantify the potential of Organic Rankine Cycles for the use of residual energy in automotive engines. To do this, an experimental ORC test bench was designed and built at CMT (Polytechnic University of Valencia), which can be coupled to different types of automotive combustion engines. Using these results, an estimation of the main variables of the cycle was obtained both in stationary and transient operating points. A potential of increasing ICE mechanical efficiency up to 3.7% could be reached at points of high load installing an ORC in a conventional turbocharged gasoline engine. Regarding transient conditions, a slightly simple and robust control based on adaptive PIDs, allows the control of the ORC in realistic driving profiles. High loads and hot conditions should be the starting ideal conditions to test and validate the control of the ORC in order to achieve high exhaust temperatures that justify the feasibility of the system.In order to deepen in the viability and characteristics of this particular application, some theoretical studies were done. A 1D model was developed using LMS Imagine.Lab Amesim platform. A potential improvement of 2.5% in fuel conversion efficiency was obtained at the high operating points as a direct consequence of the 23.5 g/kWh reduction in bsfc. To conclude, a thermo-economic study was developed taking into account the main elements of the installation costs and a minimum Specific Investment Cost value of 2030 C/kW was obtained. Moreover, an exergetic study showed that a total amount of 3.75 kW...

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Bottoming cycles for electric energy generation: Parametric investigation of available and innovative solutions for the exploitation of low and medium temperature heat sources

Cited by 198 publications

References 11 publications

Numerical Analysis of an Organic Rankine Cycle with Adjustable Working Fluid Composition, a Volumetric Expander and a Recuperator

Numerical Analysis of an Organic Rankine Cycle with Adjustable Working Fluid Composition, a Volumetric Expander and a Recuperator

Electricity generation from low-temperature industrial excess heat—an opportunity for the steel industry

Study of Organic Rankine Cycles for Waste Heat Recovery in Transportation Vehicles

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