Dynamic simulation of batch freezing tunnels for fish using Modelica

AbstractFish products are frozen to preserve quality and extend shelf-life. However, freezing processes in the industry are typically very energy demanding and seldom optimized with regard to energy usage. During freezing, the operating conditions for the refrigeration cycle, as well as the driving temperature difference over the product changes significantly from start to finish. A complete transient model including a refrigeration plant, an air blast freezing tunnel and food products has been built, based on the Modelica programming language. The product model is discretized into uniform layers, described with equations for temperature dependent properties such as thermal conductivity and heat capacity. Normally, fan power represents about 25 – 30% of the total refrigeration requirement, but at the end of the freezing process, heat from the fans can represent up to 95-99% of the refrigeration load. The results from this model indicates that a 33% reduction in total power consumption, with a penalty of 14% longer freezing time is possible with better operation of the fan. In general, this model can be a useful tool for visualization of energy saving measures. It combines a product model with a refrigeration system, demonstrating the effect of process modification on both single components and overall process performance

Process Modeling and Optimization of Supercritical Carbon Dioxide-Enhanced Geothermal Systems in Poland

Abstract This paper presents a comprehensive analysis of supercritical carbon dioxide (sCO2)-enhanced geothermal systems (EGSs) in Poland, focusing on their energetic performance through process modeling and optimization. EGSs harness the potential of geothermal energy by utilizing supercritical carbon dioxide as the working fluid, offering promising avenues for sustainable power generation. This study investigates two distinct configurations of sCO2-EGS: one dedicated to power generation via a binary system with an organic Rankine cycle and the other for combined power and heat production through a direct sCO2 cycle. Through accurate process modeling and simulation, key parameters influencing system efficiency and performance are identified and optimized. The analysis integrates thermodynamic principles with geological and operational constraints specific to the Polish context. The results highlight the potential of sCO2-EGSs to contribute to the country’s energy transition, offering insights into the optimal design and operation of such systems for maximizing both power and thermal output while ensuring economic viability and environmental sustainability.Process Modeling and Optimization of Supercritical Carbon Dioxide-Enhanced Geothermal Systems in PolandpublishedVersio

Environmental Impact of Enhanced Geothermal Systems with Supercritical Carbon Dioxide: A Comparative Life Cycle Analysis of Polish and Norwegian Cases

Low-carbon electricity and heat production is essential for keeping the decarbonization targets and climate mitigation goals. Thus, an accurate understanding of the potential environmental impacts constitutes a key aspect not only for the reduction in greenhouse gas emissions but also for other environmental categories. Life cycle assessment allows us to conduct an overall evaluation of a given process or system through its whole lifetime across various environmental indicators. This study focused on construction, operation and maintenance, and end-of-life phases, which were analyzed based on the ReCiPe 2016 method. Within this work, authors assessed the environmental performance of one of the renewable energy sources—Enhanced Geothermal Systems, which utilize supercritical carbon dioxide as a working fluid to produce electricity and heat. Heat for the process is extracted from hot, dry rocks, typically located at depths of approximately 4–5 km, and requires appropriate stimulation to enable fluid flow. Consequently, drilling and site preparation entail significant energy and material inputs. This stage, based on conducted calculations, exhibits the highest global warming potential, with values between 5.2 and 30.1 kgCO2eq/MWhel, corresponding to approximately 65%, 86%, and 94% in terms of overall impacts for ecosystems, human health, and resources categories, respectively. Moreover, the study authors compared the EGS impacts for the Polish and Norwegian conditions. Obtained results indicated that due to much higher electricity output from the Norwegian plant, which is sited offshore, the environmental influence remains the lowest, at a level of 11.9 kgCO2eq/MWhel. Polish cases range between 38.7 and 54.1 kgCO2eq/MWhel of global warming potential in terms of electricity production. Regarding power generation only, the impacts in the case of the Norwegian facility are two to five times lower than for the installation in the Polish conditions. Keywords: enhanced geothermal systems; supercritical carbon dioxide cycles; life cycle assessment; geothermal energy; environmental performancepublishedVersio

Techno-Economic Assessment of the Supercritical Carbon Dioxide Enhanced Geothermal Systems

Enhanced geothermal systems distinguish themselves among other technologies that utilize renewable energy sources by their possibility of the partial sequestration of carbon dioxide (CO2). Thus, CO2 in its supercritical form in such units may be considered as better working fluid for heat transfer than conventionally used water. The main goal of the study was to perform the techno-economic analysis of different configurations of supercritical carbon dioxide-enhanced geothermal systems (sCO2-EGSs). The energy performance as well as economic evaluation including heat and power generation, capital and operational expenditures, and levelized cost of electricity and heat were investigated based on the results of mathematical modeling and process simulations. The results indicated that sCO2 mass flow rates and injection temperature have a significant impact on energetic results and also cost estimation. In relation to financial assessment, the highest levelized cost of electricity was obtained for the indirect sCO2 cycle (219.5 EUR/MWh) mainly due to the lower electricity production (in comparison with systems using Organic Rankine Cycle) and high investment costs. Both energy and economic assessments in this study provide a systematic approach to compare the sCO2-EGS variants. Keywords: enhanced geothermal systems; CO2-EGS; supercritical carbon dioxide cycles; Organic Rankine Cycle; combined heat and power; geothermal energyTechno-Economic Assessment of the Supercritical Carbon Dioxide Enhanced Geothermal SystemspublishedVersio

Potential tube configurations design for 3D printing – status from 2017 FDM 3D printing activities

publishedVersio

Consumer power via the Internet

Recently, there has been plenty of upbeat reporting on new opportunities provided by the Internet to business in marketing and sales and in financial services, to name a few. Most of these developments may be said to increase "firm-power". This paper describes a proposal to strongly enhance "consumer-power" to the ultimate benefit of both businesses and consumers.

Mathematical modeling of CO2 based heat pumping systems: New developments for simulation tools to aid the design of systems for non-residential buildings

CO2 based heat pumping systems have in recent years received considerable focus world-wide. Now, attention has been turned toward heating and cooling of larger, non-residential buildings. With plate heat exchanger’s now becoming available for CO2, this natural refrigerant becomes a real alternative for larger applications, considering both efficiency and economy. However, research and design tools have not been readily available to fully design optimized systems for larger buildings. Simulation-aided design is particularly valuable for CO2 systems, as existing conventional systems cannot be used with good results. However, the special properties of CO2 both increase the need for discretization of component models, and require more complex fundamental equations for thermophysical properties. Because of this, circuit simulations with CO2 are considerably slower compared to simulation of conventional refrigerant systems, to the extent that it is limiting the ability to design optimal CO2 systems. In this work, an existing circuit simulation tool, CSIM, has been extended and modified to be suited for efficient design and optimization of heat pumping systems with complex-configuration plate heat exchangers. The modification of CSIM performed in this work includes a versatile and configurable plate heat exchanger model, and a general method to handle more complex fluid stream configurations. The new model can describe the local behavior in individual, parallel flowing, plate channels, including asymmetric heat transfer, pressure drop and mass flow distribution. Implemented into CSIM, this model can be used to predict the system performance impact due to local behavior in the component. A demonstration simulation case was carried out, comparing the predicted system performance using a simple uniform model, and the new advanced plate heat exchanger model. The results showed that the additional information in the new plate heat exchanger model could have a large impact on the predicted system performance. A profiling of CSIM simulations on six test cases revealed that approximately 99.85% of the time was consumed calculating thermophysical properties for CO2. To increase the simulation performance, a new, considerably faster thermophysical library (FTL) for CO2 has been developed and implemented. FTL is based on linear interpolation in lookup tables containing pre-calculated values of CO2 properties. Through careful design of extracting functions and table grid, even the highly non-linear properties around the critical point was described with acceptable accuracy. A test suite was performed, focusing on the accuracy and calculation speed compared to the reference equation of state. Overall, simulation results showed only very minuscule differences, but the simulation time was on average reduced from 945 seconds to 2.2 seconds, a reduction of 99.77%. This considerable reduction in simulation time will facilitate the more advanced component and system models needed to optimize CO2 system design

Mathematical modeling of CO2 based heat pumping systems : New developments for simulation tools to aid the design of systems for non-residential buildings

CO2 based heat pumping systems have in recent years received considerable focus world-wide. Now, attention has been turned toward heating and cooling of larger, non-residential buildings. With plate heat exchanger’s now becoming available for CO2, this natural refrigerant becomes a real alternative for larger applications, considering both efficiency and economy. However, research and design tools have not been readily available to fully design optimized systems for larger buildings. Simulation-aided design is particularly valuable for CO2 systems, as existing conventional systems cannot be used with good results. However, the special properties of CO2 both increase the need for discretization of component models, and require more complex fundamental equations for thermophysical properties. Because of this, circuit simulations with CO2 are considerably slower compared to simulation of conventional refrigerant systems, to the extent that it is limiting the ability to design optimal CO2 systems. In this work, an existing circuit simulation tool, CSIM, has been extended and modified to be suited for efficient design and optimization of heat pumping systems with complex-configuration plate heat exchangers. The modification of CSIM performed in this work includes a versatile and configurable plate heat exchanger model, and a general method to handle more complex fluid stream configurations. The new model can describe the local behavior in individual, parallel flowing, plate channels, including asymmetric heat transfer, pressure drop and mass flow distribution. Implemented into CSIM, this model can be used to predict the system performance impact due to local behavior in the component. A demonstration simulation case was carried out, comparing the predicted system performance using a simple uniform model, and the new advanced plate heat exchanger model. The results showed that the additional information in the new plate heat exchanger model could have a large impact on the predicted system performance. A profiling of CSIM simulations on six test cases revealed that approximately 99.85% of the time was consumed calculating thermophysical properties for CO2. To increase the simulation performance, a new, considerably faster thermophysical library (FTL) for CO2 has been developed and implemented. FTL is based on linear interpolation in lookup tables containing pre-calculated values of CO2 properties. Through careful design of extracting functions and table grid, even the highly non-linear properties around the critical point was described with acceptable accuracy. A test suite was performed, focusing on the accuracy and calculation speed compared to the reference equation of state. Overall, simulation results showed only very minuscule differences, but the simulation time was on average reduced from 945 seconds to 2.2 seconds, a reduction of 99.77%. This considerable reduction in simulation time will facilitate the more advanced component and system models needed to optimize CO2 system design

El Banco Central con un rol ampliado en un sistema monetario electrónico puro

La moneda f´ısica (billetes y monedas) est´a desapareciendo progresivamente como medio importante de intercambio, tanto en pa´ıses desarrollados como en desarrollo. Las transacciones hechas con tarjetas de d´ebito, computadoras y tel´efonos m´oviles son cada vez m´as importantes. Este proceso, conducido por el avance t´ecnico, abre algunas posibilidades muy ´utiles, entre ellas, un nuevo rol beneficioso para el Banco Central –y la sociedad– . El art´ıculo asume un escenario donde un pa´ıs emite su propia moneda, y todo el dinero es “electr´onico” (sin billetes y monedas). Esto le da un impulso adicional a la soluci´on de dinero soberano: todos los dep´ositos est´an en el Banco Central. El art´ıculo tambi´en argumenta que, en un sistema de este tipo, donde los bancos no pueden crear “dinero-cr´edito” al otorgar sus pr´estamos (en esto se asemeja a la soluci´on del 100 % de reservas que muchos reformadores proponen), la econom´ıa no necesariamente resultar´a afectada por escasez de cr´edito para la inversi´on –una prevenci´on que no solo sostienen quienes defienden el sistema financiero actual, sino tambi´en muchos de sus cr´ıticos– . Esto se lograr´a recurriendo al truco no convencional de dejar que los bancos comerciales recurran al financiamiento del Banco Central para otorgar sus pr´estamos. Un tercer punto del documento es argumentar que la simplificaci´on del sistema financiero deber´ıa ser un objetivo en s´ı mismo