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11:00   Session 3: Large-scale ORC units I
Chair: Johan Van Bael
11:00
20 mins 		System-search INNOVATIVE ORC SCHEMES FOR RETROFITTING ORC WITH HIGH PRESSURE RATIO GAS TURBINES
Vinayak Hemadri, P.M.V Subbarao
Abstract: Combined cycle mode of power generation is one of the efficient way of generation of power. Combined cycles generally use gas turbine in the toping cycle. Gas turbines with retrofits like intercooling between the compressor stages and regenerator are not suitable for combined cycle operations. Tapping gas turbine exhaust heat to power for a high pressure ratio, recuperative gas turbines needs organic working fluid. This work discusses integration of ORC as a bottoming cycle in a combined cycle mode. Commercially available gas turbine models like small capacity SGT200 and medium capacity GE LM -6000 have been considered for the toping cycle. Toluene, cyclopentane, butane, MM, MDM, MD2M, D4, D5 are studied parametrically for different ORC schemes, to understand energy recovery potential from the gas turbine exhaust. ORC working fluids have been studied for saturated, superheated and supercritical schemes. The working fluid with higher potential for power generation is best suited for ORC integration. The power recovered by toluene cycle at 0.85Pr is highest with a value of 2.723MW and thermal efficiency of 31.09% for cycle with internal regeneration (IHE) amongst saturated schemes for integration with SGT200. The corresponding combined cycle efficiency is 54.11%. While recovering waste heat to power using dry working fluids, the efficiency with internal heat exchange does not actually matter, in the sense of savings in fuel. The advantage of IHE can be understood with reduced condenser loads and enhanced potential for waste heat recovery from the source fluid. It can be either used for thermal applications or power applications depending upon its availability. As siloxanes are deep dry working fluids, their internal regeneration capability is good and hence another bottoming cycle can be thought with lower boiling point organic working fluid in conjunction with primary bottoming cycle. A very innovative scheme with R-245fa and butane bottoming cycles are studied in conjunction with MM saturated cycle at 0.9Pr. The power recovery potential by using both the bottoming cycle schemes is studied. The combined cycle efficiency of 70.82% is obtained by using this arrangement. This scheme increases complexity of the combined cycle. Hence a dual pressure bottoming cycle scheme is developed using MM as the working fluid. Saturated MM is injected with expanding vapor in the turbine (which is in superheated state). Studying the potential of energy recovery in this arrangement is very creative.
11:20
20 mins 		System-search UTILIZATION OF WASTE HEAT FROM INTERCOOLED, REHEAT AND RECUPERATED GAS TURBINES FOR POWER GENERATION IN ORGANIC RANKINE CYCLES
Xurong Wang, Yi Yang, Mingkun Wang, Ya Zheng, Jiangfeng Wang, Yiping Dai
Abstract: Organic Rankine cycle (ORC) is a very attractive technology for the conversion of low-grade thermal energy into electrical and/or mechanical energy. As the ORC has a wide range of power, it can recover the waste heat from power cycles such as turbines and/or microturbines of gas. The ORC bottoming cycle is currently incorporated into the exhaust of recuperative gas turbines to further lower the temperature of the exhaust gas, yielding similar overall efficiency to that of conventional gas turbine and steam combined cycles. However, a certain amount of thermal energy in the intercooler is not effectively utilized in the intercooled gas turbine cogeneration cycles. The temperature of the compressed air at the intercooler inlet could be found about 120 ℃-250 ℃. This is an ideal energy source to be used in an ORC for power generation. In this investigation, a thermodynamic analysis was carried out on combined cycles comprising recuperated, intercooled and reheat gas turbines and two ORCs (recuperated ICRHGT-ORCs) to recover waste heat from the intercooler and the exhaust of recuperated gas turbine. Three existing gas turbines were performed as the topping cycles with appropriate modifications. The following organic fluids were considered as the working fluids in ORCs: R123, R245fa, toluene and cyclohexane. A computer program was then designed for computations of system performance. Thermodynamic analyses were performed to study the effects of parameters including evaporator temperatures and degrees of superheat at the ORC turbine inlet on the combined cycle performance. These parameters were then optimized with thermal efficiency as the objective function by means of a genetic algorithm. It was found that all the three modified gas turbines with bottoming ORCs had higher performance, with thermal efficiency increase of 7.8% to 15.2%, in comparison to their original values.
11:40
20 mins 		System-search TECHNICAL AND ECONOMICAL STUDY OF AN ORC DEDICATED TO THE PRODUCTION OF ELECTRICITY FROM A GEOTHERMAL SOURCE
Stéphane Schuller, Morgan DaSilva, Christophe Josset, Bruno Auvity, Jérôme Bellettre
Abstract: If the ORC are proving to be an effective solution to produce mechanical or electrical power from low temperature heat source, this also makes them more sensitive to the sizing of their equipment. In fact, due to the Carnot cycle between a source and a heat sink close in temperature, the pinch involved in the evaporators or condensers have new consequences on the surfaces of exchanges. In these specific conditions, technical and economical compromises must be determined in order to make ORC competitive. This paper focuses on the technical-economic study of an ORC supercritical with propane, without regenerator dedicated to the production of electricity from a geothermal source. A program is written in Matlab environment. It describes how in a first time, the four main equipment (pump, geothermal exchangers, turbine and condenser) are dimensioned by applying the theorem of equipartition of entropy production in the heat exchanger geothermal. Their costs are estimated in relation to their sizing parameters for an arbitrary chosen design ambient temperature. In a second time, it describes how their behaviour change according the weather along the year. A typical ambient temperature distribution along the year is estimated with Meteonorm and used to calculate the yearly production. In a third time the same geothermal source is virtually placed in four places in the world with different weathers. By the previous described methods four different ORC plants are designed and the comparison between each is presented. A discussion is open about the consequence of heat sink temperature variations on the characteristics of equipment, designed at a fixed ambient temperature but used at a variable ambient temperature.
12:00
20 mins 		System-search ORC BOTTOMING FOR COMBINED CYCLE SYSTEMS FED BY BIOMASS
Mario Gaia, Fredrik Mowill, Claudio Pietra
Abstract: In the last two decades ORCs have been largely used to convert the heat from biomass combustion into electric energy. The success of the ORC technology for this application is mainly due to its low maintenance requirements, ease of operation and good partial load performance. In quest for higher efficiency systems, biomass gasification , followed by conversion to electric power in a small scale combined cycle, is very promising. Indeed several gasification systems, integrated with gas cleaning and gas engines for power production, have been put into operation in the past, with different results depending on the adopted solution. The paper suggests a different approach featuring an innovative gasification device, a gas turbine prime mover, and an Organic Rankine Cycle as bottoming system, typically for a power of the combined system up to 5 MW. In the paper a preliminary study of the system performance is presented, together with a sensitivity analysis concerning the various components as well as a discussion on the main advantages and shortcomings. A comparison of the proposed system with combustion/ORC systems is , taking also into account expected O&M requirements, load modulation and pollutant emissions.
12:20
20 mins 		System-search DEVELOPMENT AND TEST OF A 100KW CLASS ORC POWER-GENERATOR FOR LOW TEMPERATURE GEOTHERMAL APPLICATIONS
Dong Hyun Lee, Young Min Yang, Chun Dong Park, Si Woo Lee, Byung Sik Park
Abstract: The major portion of the heat sources is in the lower end of the temperature spectrum. Therefore, the successful utilization of low-grade heat is very essential to energy. The organic Rankine cycles (ORCs) are one of the appropriate technologies to convert low grade heat to power. Korea Institute of Energy Research (KIER) and Jinsol Turbomachinery have jointly developed an ORC power-generator applicable to very low-temperature heat sources. This paper deals with the design, fabrication and test results of the ORC power generator. The ORC system was designed the maximum electric power output of 100kW utilizing geothermal hot water. The ORC has a simple configuration with an evaporator, an expander, a condenser and a pump. The completely hermetic turbo-generator was developed by Jinsol Turbomachinery and applied to the system. The turbo-generator has twin radial inflow turbines connected with high-speed synchronized generator. Two plate heat exchangers are used for evaporator and condenser. The performance test was conducted and the resulted gross electric power output was 91.22kW with cycle efficiency of 7.14%.