Trilateral Cycle Research Articles

Feasibility of solar-driven trilateral-like organic Rankine cycle with radial-inflow turboexpander

Low-temperature solar collectors coupled with thermal energy storage can enable stable and carbon-free energy production. This work proposes a fully integrated organic Rankine cycle (ORC) with solar field and thermocline direct energy storage. The organic fluid remains liquid inside the solar field and the thermal energy storage, leading to a trilateral-like thermodynamic cycle. As opposed to other trilateral (flash) cycles, the proposed system distinguishes itself by including a turboexpander to deal with two-phase expansion, leading to higher conversion efficiency. In particular, with the same turbine efficiency, the proposed cycle outperforms alternative integrated ORC-solar field configurations by 1.5–3.8 percentage points in thermodynamic cycle efficiency for maximum temperatures between 400–600K. The equivalent electric energy density also increases by 30% to 60%. The problem of the two-phase turbine is tackled by relying on a recently proposed radial-inflow turbine concept. The centripetal stator leverages the retrograde shape of the saturation curve to achieve a complete liquid-to-vapor expansion. As a result, the rotor can handle dry organic vapors without experiencing mechanical damage or additional losses from two-phase interactions. Preliminary turbine designs, obtained through optimization of a validated meanline method, consistently yield isentropic total-to-static efficiencies exceeding 85%, confirming the potential of the proposed system.

4E optimization comparison of different bottoming systems for waste heat recovery of gas turbine cycles, internal combustion engines, and solid oxide fuel cells in power-hydrogen production systems

Gas turbine cycles (GTC), internal combustion engines (ICE), and solid oxide fuel cells (SOFC) are three important sources of waste energy, and although some studies have been done about their waste heat recovery (WHR) systems individually, there is a lack of a study comparing them to select the best solution. In the present research, the steam Rankine cycle, CO2 supercritical Brayton cycle (SBC), inverse Brayton cycle (IBC), and air bottoming cycle are used for WHR of high-temperature exhausted gas of 500 kW natural gas-fueled GTC and ICE. Furthermore, the organic Rankine cycle (ORC), trilateral cycle, organic flash cycle, Kalina cycle, and CO2 SBC are utilized for the WHR of the SOFC-gas turbine (GT). The performance of 13 proposed configurations is compared through 4E (energy, exergy, exergy-economic, and environmental) three-objective optimizations. Considering exergy efficiency, total cost rate, and unit cost of products as target functions, the SOFC-GT-ORC system has the best performance with exergy efficiency, total cost rate, and unit cost of 64.74%, 92.51 $/h, and 19.03 $/GJ. Furthermore, GTC-IBC and ICE-IBC have the best performance in their respective categories.

Thermodynamic analysis of a coupled system based on total flow cycle and partially evaporated organic Rankine cycle for hot dry rock utilization

The total flow cycle (TFC) has a great potential to improve efficiency of geothermal energy utilization. However, it can not fully utilize the heat source due to the limited expansion ratio of the two-phase expander. To solve the problem, a coupled system of TFC and partially evaporated organic Rankine cycle (TFC-PEORC) is proposed. The thermodynamic model considering the pinch point location migration is developed, and the effects of operating parameters on the temperature matching and system performance are investigated. On this basis, system optimization is carried out. At the same time, the performance of TFC-PEORC was compared with the single-stage TFC, the coupled system of TFC and organic Rankine cycle (TFC-ORC), the coupled system of trilateral cycle and organic Rankine cycle (TLC-ORC), and the coupled system of TFC and Kalina cycle (TFC-KC) under optimal operating conditions. The results show that the net output power of TFC-PEORC has a 14.26 % increase compared to TFC, and that TFC-PEORC can provide excellent the temperature matching of the high temperature (HT) stage and the low temperature (LT) stage working fluids, thus providing the maximum net output power (84.36 kW) that is up to 1.93 % higher than TFC-ORC.

Thermodynamic investigation of a novel organic Rankine cycle including partial evaporation, dual-phase expander, flash tank, dry expander and recuperator for waste heat recovery

The optimum exploitation of low-grade waste heat sources is a critical issue for producing clean electricity and promoting sustainability. Organic Rankine Cycle (ORC) is an emerging technology to produce electricity exploiting various energy sources like waste heat recovery, solar irradiation and geothermal energy. The present work suggests a novel ORC architecture that combines different solutions for increasing electricity production from low-grade waste heat sources (e.g., industrial waste heat up to 200 °C). More specifically, the present cycle includes the solution of partial evaporation, dual-phase expansion, flash tank separator, dry expander and recuperator. All these concepts together create a global optimal design which is examined with the environmentally friendly working fluid R1233zd(E). The present work examines the suggested ORC parametrically, and then the design is optimized. According to the results, the present novel configuration was found to outperform compared to the trilateral cycle, classical ORC without superheating, flash tank cycle, and partial evaporation ORC, for waste heat stream temperatures from 80 °C up to 200 °C. Furthermore, the analysis for the novel systems proved that the optimal system energy efficiency was found to range from 2.3% for Tin = 80 °C up to 13.3% for Tin = 200 °C, while the respective exergy efficiency from 27.3% for Tin = 80 °C up to 62.5% for Tin = 200 °C.

Technical and Economic Performance of Four Solar Cooling and Power Co-Generated Systems Integrated With Facades in Chinese Climate Zones

Abstract There has been an increasing interest in solar-driven combined energy supply systems for low-temperate applications, particularly those based on the Organic Rankine Cycle (ORC), Kalina Cycle (KC), or Trilateral Cycle (TLC). However, systems based on these thermodynamic cycles usually employ large area collectors that stand alone or are placed on the roof, without considering integration with the building facade. This research presents a solution to large-scale photothermal utilization integrated with facades for co-generated systems. The current study is the first to conduct performance and economic assessment for four novel solar cooling and power (SCP) co-generated systems driven by evacuated tube solar collectors (ETCs) or semi-transparent photovoltaic (STPV) integrated into the building facades. The suggested systems were simulated using TRNSYS to forecast their performance metrics when used in four Chinese cities with various climate zones. As indicators, a solar fraction (SF) and unit energy cost (UEC) were used to evaluate the technical and financial aspects of each system. The STPV-vapor compression cycle (VCC) system had the highest SF (100%, except Haikou), as well as the lowest UEC (0.211$/kWh on average) among the four cities, according to the results. Among the three solar–thermal co-generation systems, ETC–ORC–VCC had the best performance (SF,37.9%; UEC,0.597$/kWh on average).

Potential savings in the cement industry using waste heat recovery technologies

This work describes technologies especially suitable for enhancing cement production process efficiency and overall plant performance by preheating raw material or generating electricity, thus reducing thermal losses, costs, and carbon dioxide emissions. Assessed systems for this purpose include power cycles such as the Organic Rankine Cycle, Tri-lateral Cycle, and Kalina cycle, and alternatives currently under development, such as thermoelectric generators and supercritical fluid cycles. Likewise, the zones of the cement production process with the most significant waste-heat recovery potential are pointed out, focusing on clinkerisation, which accounts for most of the thermal energy expenditure of a cement plant. In addition, the total carbon dioxide emissions related to cement manufacture and the participation of each production stage are presented. Finally, the potential for waste heat recovery in the cement industry of the first six Latin American producers is reviewed, which covers 82% of the total production in the region, based on the thermal and electrical requirements reported in the literature. The potential for emissions savings of carbon dioxide is estimated under the emission factor for the electricity system in each country.

Exergy-economic analysis and multi-objective optimization of a multi-generation system based on efficient waste heat recovery of combined wind turbine and compressed CO2 energy storage system

Due to the intermittent feature of renewable energies, their combination with energy storage systems seems efficient and profitable. In this regard, a wind turbine system is coupled with a compressed CO2 energy storage (CCES) system for multi-generation propose. This combination has not been done yet and seems very attractive and efficient with the present popularity of wind energy and energy storage systems. A fraction of the output power of the wind turbine is sent to the compressor and electric heater of the CCES layout in the charging and discharging period. In the CCES system, a thermoelectric generator (TEG 1), an absorption chiller, and a domestic hot water heat exchanger are used to waste energy elimination and the waste energy of the wind turbine is recovered by a trilateral cycle (TLC). The produced power of the TEG 1 and TLC is transmitted to a reverse osmosis desalination unit and an alkaline electrolyzer for freshwater and hydrogen production. Hence, the considered system is converted to a multi-product one. Energy, exergy, and exergy-economic (3E) studies are done on the whole layout through parametric analysis and multi-objective optimization. Exergy round trip efficiency and unit cost of products are obtained as 37.027% and 30.41 $/GJ in the optimization process. The considered system can produce 1960 kW of power, 336.1 kW of heating, 183.3 kW of cooling, 1.077 kg/s of freshwater, and 0.0138 kg/h of hydrogen in this case.

4E analysis and optimization of a biomass-fired waste-to-energy plant integrated with a compressed air energy storage system for the multi-generation purpose

A novel multi-generation system is introduced based on the combination of biomass gasifier-fired steam Rankine cycle (SRC) and compressed air energy storage (CAES) system. The output power of SRC feeds the compressor and electric heater of the CAES system. A domestic hot water heat exchanger and an absorption chiller are used to waste heat utilization of gasifier-SRC and a trilateral cycle (TLC) is utilized to waste energy recovery of the CAES system. Then, the output power of TLC is sent to a proton exchange membrane electrolyzer for the production of hydrogen. Hence, the considered system is converted to a power, heating, cooling, and hydrogen multi-generation system. Energy, exergy, exergy-economic and environmental studies are done on the layout in a base case, parametric analysis, and design optimization. The three-objective optimization results in the exergy round trip efficiency (ERTE), total cost rate, and unit cost of multi-generation of 41.205%, 708.136 $/h, and 17.206 $/GJ. The improvement of ERTE (30.23%) is the most visible one in comparison to the base case outputs.

Thermo-economic feasibility analysis of trilateral-cycle power generators for waste heat recovery-to-power applications

The trilateral cycle (TLC), a promising alternative waste heat recovery-to-power cycle, is receiving increasing attention due to feats such as the high thermal match between the exergy of the heat source temperature profiles and its working fluid. Although the TLC has neither been broadly applied nor commercialised because of its thermo-economic feasibility considerations. This study examined the thermo-economic analysis of different TLC power generator configurations; i.e., the saturated subcritical simple (non-recuperative) and recuperative cycles using n-pentane as the working fluid for low-grade waste heat recovery-to-power generation. Based on the thermodynamic and economic analyses, the feasibility analysis models of the cycles were established using Aspen Plus, considering efficiency, cost, and expected operating and capacity factors. Furthermore, the capacity factor, specific investment cost (SIC), and payback period (PBP), among other, were used to evaluate the cycle design configurations and sizes. The SICs of the simple and recuperative TLCs were 3,683.88 $/kW and 4,220.41 $/kW, and their PBPs were 8.43 years and 8.55 years, respectively. The simple TLC had a lower investment ratio of 0.24 compared to an investment ratio of 0.28 for the recuperative TLC. These economic values suggest that the simple TLC is more cost-effective when compared with the recuperative TLC because the recuperation process does not recompense the associated cost, making it unattractive.

Performance investigation of a novel thermosyphon based trilateral cycle using hydraulic turbine for power generation instead of two-phase expander

The trilateral cycle (TLC) has been viewed as a promising technology for low grade heat to power conversion, while its application in reality is greatly limited by the low efficiency of two-phase expander and high volume flow rate at the expander outlet. This paper suggests a novel thermosyphon based trilateral cycle (TTLC), which uses hydraulic turbine for power generation instead of two-phase expander, avoiding problems in traditional TLC systems and also providing a chance for utilization of pump-as-turbine (PAT) technologies. Thermodynamic model of the novel system is developed, as well as the two-phase flow model for the riser. The system performance of TTLC is investigated based on the first law analysis and the second law analysis, and the results are compared with those of traditional TLC and organic Rankine cycle (ORC). It is found that the extra gravitational pressure drop is the main contributor to the riser efficiency. The working fluids with smaller density ratio and specific heat are more suitable for the proposed system, such as R502, R218, R125 and R115. Increasing heat source temperature is more efficient in energy conversion than decreasing sink temperature for the TTLC system, which generates marginally more power than TLC when the heat source temperature is less than 50 °C, and less power than TLC within the deviation of 10% for the heat source temperature in the range of 50–75 °C. The traditional ORC has the worst performance due to its bad temperature matching. Moreover, the volume flow rate at the turbine outlet of TTLC is only 2–17% of those for TLC and ORC, indicating a much smaller turbine size.

Strategic integration of single flash geothermal steam cycle (SFGSC) and ejector assisted dual-evaporator organic flash refrigeration cycle (EADEOFRC) for power and multi-temperature cooling: 2nd law performance study

ABSTRACT In the present study, an ejector-assisted dual-evaporator organic flash refrigeration cycle (EADEOFRC) is integrated with a single flash geothermal steam cycle (SFGSC). The EADEOFRC also consists of a two-phase expander extracting power from the high pressure fluid before the flashing. Isopentane and n-pentane are used as the working fluid of the EADEOFRC. It is observed that EADEOFRC can be operated at an organic fluid flash pressure corresponding to which refrigeration effects of both evaporators are equal. Corresponding to this operating condition of EADEOFRC, the integrated cycle yields higher second law efficiency compared to that of the SFSC. However, this yielded second law efficiency is lower than that of the dual flash steam cycle (DFSC). In the absence of the flash chamber, the ejectors and the evaporators, the EADEOFRC becomes merely a trilateral cycle (TLC), yielding only power output. Integration of SFSC and TLC yield substantially higher second law efficiency compared to that of the DFSC. Performance of the combined cycle slightly improves if n-pentane is used as the working fluid instead of isopentane.

Performance Investigation of a Novel Thermosyphon Based Trilateral Cycle Using Hydraulic Turbine for Power Generation Instead of Two-Phase Expander

The trilateral cycle (TLC) has been viewed as a promising technology for low grade heat to power conversion, while its application in reality is greatly limited by the low efficiency of two-phase expander and high volume flow rate at the expander outlet. This paper suggests a novel thermosyphon based trilateral cycle (TTLC), which uses hydraulic turbine for power generation instead of two-phase expander, avoiding problems in traditional TLC systems and also providing a chance for utilization of pump-as-turbine (PAT) technologies. The system performance of TTLC is theoretically investigated, and the results are compared with those of traditional TLC and ORC. It is found that the slip loss is the main contributor to the riser efficiency. The working fluids with smaller density ratio and specific heat are more suitable for TTLC. TTLC generates more power than TLC when the heat source temperature is less than 50 °C, and less power than TLC within the deviation of 10% for the heat source temperature in the range of 50-75 °C. Moreover, the volume flow rate at the turbine outlet of TTLC is only 2-17% of those for TLC and ORC, indicating a much smaller turbine size.

Advanced exergo-economic schemes and optimization for medium–low grade waste heat recovery of marine dual-fuel engine integrated with accumulator

Facing the multiple pressures of energy reserves decline, ecological environment deterioration and transportation industry prosperity, in order to enhance the marine performance, improve the enterprises economic benefits, and achieve the purpose of energy conservation and emission reduction, the revolution of green and efficient waste heat recovery technology is imperative. Therefore, the exergy-based configuration design of marine cascade waste heat recovery system is proposed, including supercritical Brayton cycle, organic Rankine cycle, organic flash cycle, organic trilateral cycle and absorption refrigeration cycle. Firstly, the mathematical models of three cycle-configurations are established based on thermodynamic equations, and the authority of simulation results is preliminarily verified. Then, the relationship between working-fluid, matching mode and operation parameters with cycle-configuration performance is analyzed in turn. After the multi-objective optimization, the thermodynamic performance and economic benefits of the cycle-configuration are comprehensively evaluated. Finally, the positive influence of the accumulator on the refrigeration system is explored. The numerical results prove that the proposed cycle-configuration has significant thermodynamic performance and economic benefits, reflects the good performance of energy saving and emission reduction, and can eliminate the negative impact of latent heat fluctuation on the refrigeration system. It provides a feasible idea for researchers and manufacturers who are committed to comprehensively improve the performance of cascade waste heat recovery, and fills the research gap in the latest investigation.

Performance analysis and sensitivity of system parameters on the performance of trilateral-cycle power generator systems

ABSTRACT Though the trilateral cycle (TLC) is a promising heat recovery-to-power cycle, its application has not been widely accepted or commercialised due to some thermodynamic feasibility concerns. This study examined the performance analysis and sensitivity of the system parameters on the thermodynamic performance of the TLC power generator systems for waste heat recovery-to-power generation. Thermodynamic models of the simple, recuperative, reheat and regenerative TLCs were established. Performance analysis and sensitivity of the system parameters on the cycles’ performance were conducted at the expander inlet temperature of 453 to 473 K, expander pressure of 2 to 3 MPa and expander isentropic efficiency of 50% to 100%. The expander inlet temperatures, pressures, and its isentropic efficiencies have significant effects on the thermodynamic efficiencies and net work output of the cycles. At 473 K cycle high temperature, the thermal efficiencies of the cycles increase from 20.13% to 21.97%, 23.29% to 23.91%, 20.62% to 22.07% and 20.66% to 22.9% for the simple, recuperative, reheat and regenerative TLCs, respectively. Their corresponding net power outputs varied from 131.6 to 134.1 kW, 145.9 to 152.2 kW, 113.8 to 124.1 kW and 124.9 to 130.5 kW, respectively. The cycles’ thermodynamic performance increased with an increase in expander inlet temperature, expander pressure and expander isentropic efficiencies.

Thermoeconomic comparison between the organic flash cycle and the novel organic Rankine flash cycle (ORFC)

Growing environmental concerns are driving the energy market toward the development of thermodynamic cycles to harness renewable energy and waste heat. This manuscript introduces the novel organic Rankine flash cycle, which combines the organic Rankine cycle with the trilateral cycle, merging their advantages in terms of high specific power output and low heat transfer irreversibility, respectively. By comparing the organic Rankine flash cycle to the organic flash cycle, it was found that the proposed architecture reaches a peak exergy efficiency at a more realistic value of two-phase expansion volume flow ratio, consistently achieves higher energy and exergy efficiencies, presents a lower cost, and is not constrained to operate close to the working fluid saturation temperature, promising easier operability. Considering pentane as working fluid, the exergy efficiency of the organic Rankine flash cycle is 18%p higher for a heat source temperature of 150 °C, 12%p for 175 °C, and 4%p for 200 °C. The attractive thermoeconomic performance of the proposed organic Rankine flash cycle highlights the potential of such a cycle as a new paradigm in the ORC panorama, encouraging further investigation towards practical demonstration.

Advanced thermodynamic cycles for finite heat sources: Proposals for closed and open heat sources applications

This paper analyses two non-conventional thermodynamic cycles designed to work with finite heat sources, which are suitable for maximum temperatures of about 400 °C. The Hybrid Rankine-Brayton (HRB) cycle fits well to closed heat sources and, in the paper, it is analysed considering its exergy efficiency and some requirements for the maximum and minimum temperature of the heat transfer fluid that feeds the cycle, obtaining promising results. The other one is a new proposal called Recuperated and Double Expanded (RDE) cycle, aimed to translate the good features of HRB from closed heat sources to open ones, where the performance of HRB is limited.Both cycles are compared to some reference ones. Results show that the HRB cycle is a good candidate for finite closed heat sources, particularly with maximum temperature around 400 °C and with temperature changes of the heat transfer fluid from 100 °C to 150 °C. The RDE cycle exhibits good performance for finite open heat sources with maximum temperatures between 200 °C and 400 °C, and it behaves similarly to tri-lateral cycles.

Analysis of a combined trilateral cycle - organic Rankine cycle (TLC-ORC) system for waste heat recovery

A combined Trilateral Cycle-Organic Rankine Cycle (TLC-ORC) system for waste heat recovery is proposed in this paper in order to obtain a better matching performance between the heat source and working fluid. Working fluid selection including Cyclohexane, Toluene, Benzene and water for the high temperature cycle is analyzed based on thermodynamic model under different evaporating temperature of high temperature cycle and low temperature cycle. Results show that Toluene has the best performance among the studied four high temperature working fluid. The net power output, thermal efficiency and exergy efficiency increases with Tevap,HT or Tevap,LT increasing at any a high temperature working fluid. The maximum net power output 11.3 kW, thermal efficiency 24.2% and exergy efficiency 63.2% are achieved by Toluene at Tevap,HT =530 K and Tevap,LT =373 K at the same time. It is also found that evaporator 1 has the largest exergy destruction while condenser 1 has the smallest one among all the components. Meanwhile, the condenser 2 has the lowest exergy efficiency while condenser 1 has the highest one. These results show us the direction to optimize the system parameters to improve the total efficiency of the whole system.

Working fluids selection from perspectives of heat source and expander for a Trilateral cycle

Abstract This paper selects the working fluids for Trilateral cycle from two unique perspectives. The first aspect is to match the heat sources temperature with the critical temperature of working fluids, in which the thermal efficiency, exergy efficiency and utilization of heat source are chosen as the evaluation indicators. A better performance can be achieved when the heat source temperature approaches to the critical temperature of working fluid. From the aspect of expander, working fluids are selected to reduce volumetric flow ratio of expander and the size of expander, which have the lager vapor pressure at condensing temperature (VP), lager density at expander outlet and lower critical temperature. N-butane and R152a show higher net power output and lower volumetric flow ratio of expander among 13 studied working fluids. Two functions of expander volumetric flow ratio with respect to critical temperature of working fluid and VP have been gotten respectively. Furthermore, it can be concluded the suitable heat source temperature range of a TLC system is moderate temperature.

Shift-characteristics and bounds of thermal performance of organic Rankine cycle based on trapezoidal model

In consideration of the constraints of actual working fluids on theoretical study of organic Rankine cycle (ORC), a trapezoidal cycle (TPC) with theoretical model to simulate ORC was proposed in previous works. In this study, mathematical models of working fluids including model of simulated saturation curve (MSSC) and model of linear saturation lines (MLSL) are proposed and built. Combining mathematical models of working fluids and TPC, the thermodynamic characteristics and principles of TPC (or ORC) can be studied or predicted theoretically. There exists a shift-curve of net power output with corresponding shift-temperature of heating fluid for working fluids, which indicates the shift of net power output from having optimum condition of maximum power to monotonic increase with evaporation temperature. This shift-characteristic is significant to working fluid selection and evaluation of cycle performance, for it indicates that cycle without optimum condition can yield higher net power output than the cycle with optimum condition. Equations to calculate the shift-temperature in ORC (or TPC) are derived; and equations to calculate the highest optimal evaporation temperature and highest maximum power as the highest optimum condition at this shift-temperature are obtained. Based on TPC and its theoretical model, the lower and upper bounds of thermal performance (maximum power and corresponding thermal efficiency) of TPC (or ORC) can be demonstrated and acquired. TPC can develop to Carnot cycle or trilateral cycle that it is significant to use TPC as a generalized cycle to study the general principles and characteristics of the cycles.

Investigation of an Innovative Cascade Cycle Combining a Trilateral Cycle and an Organic Rankine Cycle (TLC-ORC) for Industry or Transport Application

An innovative cascade cycle combining a trilateral cycle and an organic Rankine cycle (TLC-ORC) system is proposed in this paper. The proposed TLC-ORC system aims at obtaining better performance of temperature matching between working fluid and heat source, leading to better overall system performance than that of the conventional dual-loop ORC system. The proposed cascade cycle adopts TLC to replace the High-Temperature (HT) cycle of the conventional dual-loop ORC system. The comprehensive comparisons between the conventional dual-loop ORC and the proposed TLC-ORC system have been conducted using the first and second law analysis. Effects of evaporating temperature for HT and Low-Temperature (LT) cycle, as well as different HT and LT working fluids, are systematically investigated. The comparisons of exergy destruction and exergy efficiency of each component in the two systems have been studied. Results illustrate that the maximum net power output, thermal efficiency, and exergy efficiency of a conventional dual-loop ORC are 8.8 kW, 18.7%, and 50.0%, respectively, obtained by the system using cyclohexane as HT working fluid at THT,evap = 470 K and TLT,evap = 343 K. While for the TLC-ORC, the corresponding values are 11.8 kW, 25.0%, and 65.6%, obtained by the system using toluene as a HT working fluid at THT,evap = 470 K and TLT,evap = 343 K, which are 34.1%, 33.7%, and 31.2% higher than that of a conventional dual-loop ORC.