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Opcon Powerbox is a product developed by Opcon together with the underlying company SRM (Svenska Rotor Maskiner) where surplus heat from the industry is used through an Organic Rankine Cycle (ORC)–process to produce electricity. An ORC-process is a thermodynamic circle process in which a refrigerant is used as the working fluid. The refrigerant makes it possible for the circle process to operate at lower temperatures than the conventional Rankine process. In this master’s thesis a data analysis software for the Opcon Powerbox has been developed in which measurement data is retrieved and handled from the Opcon Powerbox. The software performs calculations and analysis on the data with which the system can be evaluated. This thesis has been carried out with SRM.

Liquid-metal Rankine power conversion systems (PCS) coupled with a fission reactor remain an attractive option for space power applications because system specific power and efficiency is very favorable for plant designs of 100 kW(e) or higher. Potential drawbacks to the technology in a reduced gravity environment include two-phase fluid management processes such as liquid-vapor phase separation. The most critical location for phase separation is at the boiler exit where only vapor must be sent to the turbine because blade erosion occurs from high velocity liquid droplets entrained by vapor flow. Previous studies have proposed that rotary separators be used to separate the liquid and vapor from a two phase mixture. However these devices have complex turbo machinery, require kilowatts of power and are untested for high vapor flow conditions. The Interphase Transport Phenomena (ITP) laboratory has developed a low-power, passive microgravity vortex phase separator (MVS) which has already proven to be an essential component of two-phase systems operating in low gravity environments. This thesis presents results from flight experiments where a Rankine cycle was operated in a reduced gravity environment for the first time by utilizing the MVS for liquid and vapor phase separation. The MVS was able to operate under saturated conditions and adjust to system transients as it would in the Rankine cycle by controlling the amount of liquid and vapor within the device. A new model is developed for the MVS to predict separation performance at high vapor flow conditions for sizing the separator at the boiler, condenser, and turbine locations within the cycle by using a volume limiting method. This model factors in the following separator characteristics: mass, pumping power, and available buffer volume for system transients. The study is concluded with overall Rankine efficiency and performance changes due to adding vortex phase separation and a schematic of the Rankine cycle with the integration of the MVS is presented. The results from this thesis indicate the thermal to electric efficiency and specific mass of the cycle can be improved by using the MVS to separate the two phases instead of a rotary separator.

Liquid-metal Rankine power conversion systems (PCS) coupled with a fission reactor remain an attractive option for space power applications because system specific power and efficiency is very favorable for plant designs of 100 kW(e) or higher. Potential drawbacks to the technology in a reduced gravity environment include two-phase fluid management processes such as liquid-vapor phase separation. The most critical location for phase separation is at the boiler exit where only vapor must be sent to the turbine because blade erosion occurs from high velocity liquid droplets entrained by vapor flow. Previous studies have proposed that rotary separators be used to separate the liquid and vapor from a two phase mixture. However these devices have complex turbo machinery, require kilowatts of power and are untested for high vapor flow conditions. The Interphase Transport Phenomena (ITP) laboratory has developed a low-power, passive microgravity vortex phase separator (MVS) which has already proven to be an essential component of two-phase systems operating in low gravity environments. This thesis presents results from flight experiments where a Rankine cycle was operated in a reduced gravity environment for the first time by utilizing the MVS for liquid and vapor phase separation. The MVS was able to operate under saturated conditions and adjust to system transients as it would in the Rankine cycle by controlling the amount of liquid and vapor within the device. A new model is developed for the MVS to predict separation performance at high vapor flow conditions for sizing the separator at the boiler, condenser, and turbine locations within the cycle by using a volume limiting method. This model factors in the following separator characteristics: mass, pumping power, and available buffer volume for system transients. The study is concluded with overall Rankine efficiency and performance changes due to adding vortex phase separation and a schematic of the Rankine cycle with the integration of the MVS is presented. The results from this thesis indicate the thermal to electric efficiency and specific mass of the cycle can be improved by using the MVS to separate the two phases instead of a rotary separator.

This thesis contributes to the knowledge and the characterization of scroll machines and their systems. It is based on experimental and modeling works carried out on: a) A hermetic scroll compressor used inside an air-cooled water chiller. b) An oil-free open-drive scroll expander integrated into an Organic Rankine Cycle (ORC) power system. c) Open-drive scroll compressor and expander used in a Liquid Flooded Ericsson Cycle Cooler (LFEC). Such a system uses the liquid flooding of the compressor and of the expander to approach isothermal compression and expansion processes. New semi-empirical models of the scroll compressor and expander were proposed and existing models improved. A deterministic model of the scroll expander was established. The model associates a geometrical description of the machine with a thermodynamic description of the expansion process. This model was validated for the two expanders investigated experimentally. The model validation revealed that the performance of the expanders is mainly affected by the supply pressure drop and by the internal leakages. Using the validated model, parametric studies were carried out to investigate the variation of the performance of both expanders with modification of their design and with the operating parameters. The thesis also investigated the scroll machines from the point of view of their integration into thermal systems. A first experimental investigation was carried out on an air-cooled chiller. The scroll compressor semi-empirical model, with its parameters identified on the basis of published manufacturer data, was used as a refrigerant flow meter. The analysis of the experimental data allowed a better understanding of the chiller operation and a better identification of its model parameters (such as the fan and the hot gas bypass control models). A second experimental investigation was carried out on an ORC power system, working with R123. In order to select the most appropriate fluid, the performances achieved with four different fluids were compared by simulation. The experimental study confirmed that the scroll expander is a good candidate for an ORC system: the tested prototype presented a good performance (the maximum global isentropic effectiveness achieved was 68%). Using an ORC simulation model, parametric studies were carried out to investigate the effects of the expander characteristics and operating conditions on the cycle performance. The latter is mainly affected by the expander internal leakage and by the liquid subcooling at the condenser exhaust. A third experimental investigation was performed on a LFEC working with nitrogen as refrigerant and alkyl-benzene oil as flooding liquid. Experimental data was used to identify the parameters of the scroll compressor and expander semi-empirical models. Parametric studies were performed to identify the different factors affecting their performance. One of the undesirable features of the machines is the increase of the supply and exhaust pressure drops with the increase of oil quantity.

Conversion of a scroll compressor to an expander for organic Rankine Cycle: modeling and analysis / UOIT

Organic Rankine Cycle (ORC) heat engines convert low-grade heat to other forms of energy such as electrical and mechanical energy. They achieve this by vaporizing and expanding the organic fluid at high pressure, turning the turbine which can be employed to run an alternator or any other mechanism as desired. Conventional Rankine Cycles operate with steam at temperatures above 400 ℃. The broad aspect of the research focussed on the generation of electricity to cater for household needs. Solar energy would be used to heat air which would in turn heat rocks in an insulated vessel. This would act as an energy storage in form of heat from which a heat transfer fluid would collect heat to supply the ORC heat engine for the generation of electricity. The objective of the research was to optimize power output of the ORC heat engine operating at temperatures between 25℃ at the condenser and 90 to 150℃ at the heat source. This was achieved by analysis of thermal energy, mechanical power, electrical power and physical parameters in connection with flow rate of working fluid and heat transfer fluids.

A high demand of both electricity and heat exists in Arizona Chemical (a chemical plant dedicated to the distillation of Crude Tall Oil) for production processes. Due to the rising cost of resources and electricity, more and more companies are trying to decrease the energy expenses to increase their competitiveness in a global market, thus increasing their profit. Some companies look at their energy consumption in order to diminish it or to explore the opportunity to generate their own and cheaper energy. In companies where the production of steam already takes place, cogeneration can be a good solution to palliate the cost of the energy used. This study addresses this issue through three actions such as the characterization of the boiler, a better steam flow measurement grid and the generation of electricity. The first one addresses the state of one of the key parts of steam production, the boiler, through the calculation of its efficiency with two different methods (direct and indirect calculation). These methods require some measurements which were provided afterwards by the company supervisor. This will allow the company to identify the weaknesses of the boiler to be able to improve it in the future. The second one aims to improve the knowledge about the steam system. New flow measurement points were suggested after doing an analysis of the current controlled flows to have a better overview outline of the steam use.The third one studies the generation of electricity with a Rankine cycle. The limitations in the characteristics of the steam were identified and different configurations are proposed in accordance to the restrictions identified. An efficiency of 93% is obtained for the boiler with the direct method and 82.3 % for the indirect one. The difference between them can be explained by the use of datafrom different time frames for both methods. The main contributors to the losses are the ones related to the dry flue gas and the hydrogen in the fuel. In the current status only 40% of the steam flows are identified, a number which is expected to raise with the new measurement points. It was not possible to estimate the effect of the new points due to the desire of the company to not disturb the current production. Due to the fuel price the production of steam for only electricity was not profitable and instead the generation of both electricity and heat from the same steam is proposed. This integrated system is now possible to implement due to its low payback time (2.3 years). This solution can generate 758 kW of electricity and provide the company with 6437 MWh of electricity each year. Then, the effect of the variation of different variables over the performance of the cycle were studied: different electricity prices, steam rate production, fuel cost and the state of the condensate recovery were discussed. The variation of both the condensate recovery and fuel cost did not affect the payback time due to their costs being neutralised by the revenues obtained from them. The variation of the electricity prices and steam production affects the payback but due to the high revenue that is expected it does not hamper the good nature of the investment. The generation of electricity is recommended due to the low payback time obtained. The different variations studied in the system did not change the payback time notably and showed that the investment is highly profitable in all the scenarios considered. The use of two smaller turbines instead of the one chosen (with a maximum rated power of 6 MW while only 758 kW is generated with the proposed solution) should be studied since the turbines would work closer to their maximum efficiency.

This study is an attempt at achieving Net Zero Energy Building (NZEB) using a solar Organic Rankine Cycle (ORC) based on exergetic and economic measures. The working fluid, working conditions of the cycle, cycle configuration, and solar collector type are considered the optimization parameters for the solar ORC system. In the first section, a procedure is developed to compare ORC working fluids based on their molecular components, temperature-entropy diagram and fluid effects on the thermal efficiency, net power generated, vapor expansion ratio, and exergy efficiency of the Rankine cycle. Fluids with the best cycle performance are recognized in two different temperature levels within two different categories of fluids: refrigerants and non-refrigerants. Important factors that could lead to irreversibility reduction of the solar ORC are also investigated in this study. In the next section, the system requirements needed to maintain the electricity demand of a geothermal air-conditioned commercial building located in Pensacola of Florida is considered as the criteria to select the optimal components and optimal working condition of the system. The solar collector loop, building, and geothermal air conditioning system are modeled using TRNSYS. Available electricity bills of the building and the 3-week monitoring data on the performance of the geothermal system are employed to calibrate the simulation. The simulation is repeated for Miami and Houston in order to evaluate the effect of the different solar radiations on the system requirements. The final section discusses the exergoeconomic analysis of the ORC system with the optimum performance. Exergoeconomics rests on the philosophy that exergy is the only rational basis for assigning monetary costs to a system’s interactions with its surroundings and to the sources of thermodynamic inefficiencies within it. Exergoeconomic analysis of the optimal ORC system shows that the ratio Rex of the annual exergy loss to the capital cost can be considered a key parameter in optimizing a solar ORC system from the thermodynamic and economic point of view. It also shows that there is a systematic correlation between the exergy loss and capital cost for the investigated solar ORC system.

The shift towards renewable energy has steered the focus of power plant operation towards flexibility and fast response which are more attainable through the use of combined-cycle power plants. These aspects are required to account for the fluctuation of the supply as well as the demand of power that is associated with renewable energy. Combined-cycle power plants consist of a gas turbine as the topping cycle, forming the core of the plant, and a Rankine cycle with a steam turbine as the bottoming cycle. A component called the Heat Recovery Steam Generator (HRSG) forms a connection point between the two cycles. It uses the heat released from the gas turbine to produce high pressure and temperature steam to be sent to the steam turbine. The objective of this project is to develop a model of a combined-cycle power plant in Flownex which can be solved in off-design conditions in order to compare it to plant data. The verification of this model will show that Flownex can be used to effectively and efficiently model a combined-cycle power plant. The process of development of the final Flownex model was achieved using various additional software. Initially, an analytical model was developed in Mathcad (software used for engineering calculations). This software provides a tool for understanding knowns, unknowns and what is being calculated in the system. Manual calculations of the Heat Recovery Steam Generator (HRSG) were done using heat balance equations. A temperature profile of the gas and water/steam in the HRSG was developed so that the duties of each component (economiser, evaporator, superheater) could be calculated. The overall conductance (UA) of each component was calculated in the design mode for the system to be evaluated in off-design mode. The development of an analytical model provided detailed understanding of the process of mathematical modelling used in commercial tools. Thereafter, a model was built in Virtual Plant, a thermodynamic modelling software for assessing plant performance. Virtual Plant uses plant design information and first engineering principles to predict plant performance. Finally, the Flownex model was designed. Flownex uses endpoint values (initial pressure and temperature and outgoing mass flow) and the UA of each component to calculate the characteristics of the flow at each intermediate point. For the single-, double-, and triple-pressure combined-cycle power plant systems, the analytical, Virtual Plant and Flownex models were compared. The results of all the models agreed closely with one another. The triple-pressure design and off-design Virtual Plant and Flownex models were also compared to plant data and it was concluded that Flownex was successful in modelling the design and off-design conditions of a combined-cycle power plant.