Cooling demand in Europe is predicted to grow 25-50% between 2020-2050. Meanwhile, the EU aims to lower the greenhouse gas emissions from its building stock by 60%. Therefore, it is essential to find solutions that can meet the growing cooling demand with less energy and integrate renewable energy sources. The goal of this thesis is to technically evaluatehigh-temperature cooling systems and their contributions to the targets mentioned above. The study was conducted using advanced building energy simulations and developing analytical methods. IDA Indoor Climate and Energy 4.8was selected as the simulation tool. The study is a part of GEOFIT project, and the used building physics and measurement data were based on one of the project pilots. The selected building is a representative office building that is a part of a three-building school complex. The building is located in Sant Cugat near Barcelona, in an area which has a typical Mediterranean climate. The simulated building model was validated using onsite measurement data. Two types of high-temperature cooling systems were studied: a radiant cooling system and an all-air cooling system. For the study, the systems were designed to create equal thermal comfort conditions, so that their energy and exergy use could be compared. In the studied case, the radiant cooling system was found to use 40% less energy and consume 85% less exergy than a conventional low-temperature all-air cooling system. It was also found that a passive geothermal radiant cooling system requires 66% less electricity for pumps and fans than a passive geothermal all-air cooling system. The results demonstrate that radiant cooling systems have the potential to lower exergy consumption in cooling applications thanks to the high supply temperature and that using water as a heat transfer medium is more efficient than using air. / Kylningsefterfrågan i Europa förutses att växa 25-50% mellan 2020-2050. Samtidigt strävar EU efter att sänka utsläppen av växthusgaser från sina byggnader med 60%. Det är därför viktigt att hitta lösningar som kan tillgodose det växande kylbehovet med mindre energi och att integrera förnybara energikällor. Målet med denna avhandling är en teknisk evaluering av högtemperatur-kylsystem och deras bidrag till ovan nämnda mål. Studien genomfördes med avancerade simuleringar av byggnadsenergi och utvecklade analytiska metoder. IDA Indoor Climate and Energy 4.8 valdes som simuleringsverktyg. Studien är en del av GEOFIT-projektet och den använda byggnadsfysiken och mätdata baserades på en av projektpiloterna. Den valda byggnaden är en representativ kontorsbyggnad som ingår i ett skolbyggnad med tre byggnader. Byggnaden ligger i Sant Cugat nära Barcelona, i ett område som har ett typiskt medelhavsklimat. Den simulerade byggnadsmodellen validerades med hjälp av mätdata på plats. Två typer av högtemperatur-kylsystem studerades: ett strålande kylsystem och ett luftkylsystem. För studien designades systemen för att skapa lika termiska komfortförhållanden, så att deras energi och exergianvändning kunde jämföras. I det studerade fallet visade sig att det strålande kylsystemet använde 40% mindre energi och förbrukade 85% mindre exergi än ett konventionellt högtemperatur-kylsystem med låg temperatur. Man fann också att ett passivt geotermiskt strålkylsystem kräver 66% mindre el för pumpar och fläktar än ett passivt geotermiskt luftkylsystem. Resultaten visar att strålningskylsystem har potential att sänka exergiförbrukningen i kylapplikationer tack vare den höga framledningstemperaturen och att användning av vatten som värmeöverföringsmedium är effektivare än att använda luft. / <p>QC 210204</p>

Liquefied natural gas (LNG) cold utilization in small scale regasification stations is a novel topic in the industry, while such systems have been proven feasible in large scale LNG facilities. Cold recovery and utilization in LNG regasification facilities would increase the thermodynamic efficiency and reduce cold pollution. The aim of the study is to analyze the possibility to apply industry-proven thermodynamic cycles in small scale satellite regasification stations for electricity production, taking the characteristics of a real-world regasification station project in Druskininkai, Lithuania for which useful cold utilization is not currently planned. Direct Expansion (DE) and Rankine (ORC) Cycles are analyzed together with cascading using Aspen Hysys software to find the optimal solution considering thermal and exergy efficiency as well as the payback period. Thermoeconomically feasible retrofit solutions of approximately 13% thermal efficiency and approximately 17% exergy efficiency showing payback periods of 5 to 10 years and 3.3 to 6 thousand euro additional capital expenditure (CAPEX) per net kW of power production are found. Increase in complexity of thermodynamic cycles is directly proportional to both increased thermodynamic efficiencies and capital costs and the study proves that there is a limit at which increase in thermodynamic efficiency of a cycle by cascading becomes economically infeasible. Future work is suggested to improve the accuracy of the results by rigorous design to evaluate pressure drops as well as improvements in economic analysis by utilizing the discounted cash flow methodology. Sensitivity analysis of LNG physical and chemical conditions as well as ambient air could be performed whereas changes in working fluid and better engineering of the part related to intial heat exchange could improve thermodynamic efficiencies. Alternative solutions with a higher temperature heat source are also suggested.

According to the Intergovernmental Panel on Climate Change, Carbon Dioxide Removal (CDR) technologies play a significant role in deep mitigation pathways to limit global temperature rise to 1.5°C. As a result, interest in them is becoming increasingly prevalent, the most widely discussed being Direct Air Capture (DAC), or active removal of carbon dioxide from atmospheric air. While DAC processes have indeed been successfully tested, one of the most prominent being that developed by Canadian company Carbon Engineering, their widespread deployment faces significant headwinds due to prohibitively high energy consumption and its associated costs. Before DAC can be considered to exist in a state of technological readiness, reductions to the installations' energy demand must be realized. This thesis analyzes the thermodynamic behavior of Carbon Engineering's proposed 1 Mt-CO2/year natural gas fuelled DAC plant, which they describe as “a low-risk starting point rather than a fully optimized least-cost design” [Keith et al., Joule 2, 1573], with the aim to illustrate key areas to which energy efficiency improvement measures must target. With an understanding built of the mechanisms by which energy is utilized and irreversibly lost within their plant, suggestions are put forth for directions to pursue for process improvements, with further analysis included on potential alternative plant configurations which would reduce overall heat and power consumption. A thermodynamic work loss analysis is performed on their plant design at a system level, which finds 92.2% of incoming exergy being lost to thermodynamic irreversibilities. A component-level analysis is then performed to detail the mechanisms by which these losses occur in the most energy-intensive plant segments, namely, the calciner and preheat cyclones, air separation unit, water knockout system, CO2 compression system, and power island. The dissipation of chemical exergy in the air contactor component, i.e., the release of stored chemical exergy as low-grade heat to the environment due to the exothermic reaction of CO2 and aqueous KOH, was determined as the largest unavoidable source of work loss. The most avoidable losses were found to be associated with use of natural gas as a feedstock for heat and power, namely, through its introduction of additional CO2 and water to be processed within the plant, and due to gas turbine power production's inherent Carnot efficiency limits. Additional analysis and discussion follows regarding possible loss reduction measures and modifications, the key concept presented being the use of renewable energy to provide plant power, combined with a calciner using electric resistance heating to meet its reduced thermal demand. Use of a readily-available high-temperature heat source for calciner heat is also considered, with thorough description included of its thermodynamic advantages. Finally, the all-electric plant concept is analyzed at a system level, and its advantages compared to the original natural gas fuelled case. / Graduate

No description available.

Power plant performance can be assessed by the method of thermodynamic analysis. The goal of this thesis is to perform a thermodynamic analysis on the University of Massachusetts’ Combined Heat and Power (CHP) District Heating System. Energy and exergy analyses are performed based on the first and second laws of thermodynamics for power generation systems that include a 10-MW Solar combustion gas turbine, a 4-MW low pressure steam turbine, a 2-MW high pressure steam turbine, a 100,000 pph heat recovery steam generator (HRSG), three 125,000 pph package boilers, and auxiliary equipment. The University of Massachusetts’ CHP plant delivers all of the campus’ steam and nearly all its electricity to the more than 200 buildings and nearly 10 million gross square feet of building space. Two 20-inch main steam transmission lines connect the plant to the campus. On an annual basis the plant generates approximately 1,100,000,000 pounds of steam and 100,000,000 kWh of electric power. The plant has a SCADA (Supervisory Control and Data Acquisition) system. Rockwell Automation’s RSLinx OPC (Object Linking and Embedding for Process Control) server acquires data from up to 675 field instruments in the plant which is used for carrying out the analyses. The latest pollution control technologies, including advanced combustion turbine low NOx burners, advanced Selective Catalytic Reduction and Oxidation Catalyst pollution control technologies are employed in the plant. System efficiencies are calculated for a wide range of component operating loads. Factors affecting efficiency of the CHP district heating system are analyzed. In the analysis, actual system data is used to assess the district heating system performance, energy and exergy efficiencies and exergy losses. Energy and exergy calculations are conducted for the whole year on an hourly basis. Factors affecting efficiency of the CHP district heating system are analyzed and recommendations made to improve the operating efficiency. The results show how thermodynamic analysis can be used to identify the magnitudes and location of energy losses in order to improve the existing system, processes or components.

A decomposition methodology based on the concept of "thermoeconomic isolation" applied to the synthesis/design and operational optimization of an advanced tactical fighter aircraft is the focus of this research. Conceptual, time, and physical decomposition were used to solve the system-level as well as unit-level optimization problems. The total system was decomposed into five sub-systems as follows: propulsion sub-system (PS), environmental control sub-system (ECS), fuel loop sub-system (FLS), vapor compressor and PAO loops sub-system (VC/PAOS), and airframe sub-system (AFS) of which the AFS is a non-energy based sub-system. Configurational optimization was applied. Thus, a number of different configurations for each sub-system were considered. The most promising set of candidate configurations, based on both an energy integration analysis and aerodynamic performance, were developed and detailed thermodynamic, geometric, physical, and aerodynamic models at both design and off-design were formulated and implemented. A decomposition strategy called Iterative Local-Global Optimization (ILGO) developed by Muñoz and von Spakovsky was then applied to the synthesis/design and operational optimization of the advanced tactical fighter aircraft. This decomposition strategy is the first to successfully closely approach the theoretical condition of "thermoeconomic isolation" when applied to highly complex, highly dynamic non-linear systems. This contrasts with past attempts to approach this condition, all of which were applied to very simple systems under very special and restricted conditions such as those requiring linearity in the models and strictly local decision variables. This is a major advance in decomposition and has now been successfully applied to a number of highly complex and dynamic transportation and stationary systems. This thesis work presents the detailed results from one such application, which additionally considers a non-energy based sub-system (AFS). / Master of Science

Yes / In this study, air, steam and CO2-enhanced gasification of rice straw was simulated using Aspen PlusTM simulator and compared in terms of their energy, exergy and environmental impacts. It was found that the addition of CO2 had less impact on syngas yield compared with gasification temperature. At lower CO2/Biomass ratios (below 0.25), gasification system efficiency (GSE) for both conventional and CO2-enhanced gasification was below 22.1%, and CO2-enhanced gasification showed a lower GSE than conventional gasification. However at higher CO2/Biomass ratios, CO2-enhanced gasification demonstrated higher GSE than conventional gasification. For CO2-enhanced gasification, GSE continued to increase to 58.8% when CO2/Biomass was raised to 0.87. In addition, it was found that syngas exergy increases with CO2 addition, which was mainly due to the increase in physical exergy. Chemical exergy was 2.05 to 4.85 times higher than physical exergy. The maximum exergy efficiency occurred within the temperature range of 800 oC to 900 oC because syngas exergy peaked in this range. For CO2-enhanced gasification, exergy efficiency was found to be more sensitive to temperature than CO2/Biomass ratios. In addition, the preliminary environmental analysis showed that CO2-enhanced gasification resulted in significant environmental benefits compared with stream gasification. However improved assessment methodologies are still needed to better evaluate the advantages of CO2 utilization.

Yes / In this study, a novel single-step synthesis of dimethyl ether (DME) based on CO2-enhanced biomass gasification was proposed and simulated using ASPEN PlusTM modelling. The exergetic and environmental evaluation was performed in comparison with a conventional system. It was found that the fuel energy efficiency, plant energy efficiency and plant exergetic efficiency of the CO2-enhanced system were better than those of the conventional system. The novel process produced 0.59 kg of DME per kg of gumwood with an overall plant energy efficiency of 65%, which were 28% and 5% higher than those of conventional systems, respectively. The overall exergetic efficiency of the CO2-enhanced system was also 7% higher. Exergetic analysis of each individual process unit in both the CO2-enhanced system and conventional systems showed that the largest loss occurred at gasification unit. However, the use of CO2 as gasifying agent resulted in a reduced loss at gasifier by 15%, indicating another advantage of the proposed system. In addition, the LCA analysis showed that the use of CO2 as gasifying agent could also result in less 21 environmental impacts compared with conventional systems, which subsequently made the CO2-22 enhanced system a promising option for a more environmental friendly synthesis of bio-DME. / Part of this work is sponsored by Ningbo Bureau of Science and Technology under its Innovation Team Scheme (2012B82011) and Major R&D Programme (2012B10042).

O presente trabalho propõe uma metodologia científica, com critérios bem definidos, para avaliar e quantificar o desempenho ambiental e a renovabilidade de processos de tratamento de esgoto, numa base única: a exergia. O desempenho ambiental é quantificado através do cálculo da eficiência exergética ambiental, definida como a razão da exergia do efeito útil do processo pela exergia total consumida dos recursos humanos e naturais, incluindo todas as entradas exergéticas. O cálculo da renovabilidade é feito por meio do índice exergético de renovabilidade definido como como a razão entre a exergia dos produtos pela soma das exergias não renováveis, a exergia destruída, a exergia de desativação e a exergia das emissões e residuos. A metodologia foi aplicada a três processos de tratamento de esgoto: dois biológicos (aeróbio e anaeróbio) e um físico-químico (TQA). O cálculo dos indicadores exergéticos foi realizado para cada um destes processos e foi observado que o processo com maiores valores de desempenho ambiental e renovabilidade, considerando o metano e o lodo do processo como efeito útil, foi o processo RAFA Lagoa Facultativa, com valores respectivamente de n<exerg,amb> (0,983) e lâmbda(7,060). A análise dos resultados mostrou que a metodologia proposta é uma ferramenta útil na avaliação e comparação do desempenho ambiental e da renovabilidade de processos de tratamento de esgoto. / This work proposes a scientific methodology, with well defined criteria, to assess and quantify the environmental performance and renewability of wastewater treatment processes on a single base: the exergy. The environmental performance was measured by calculating the environmental exergy efficiency defined as the exergy ratio of the useful effect of the process to the total exergy consumed by human and natural resources, including all the exergy inputs. The renewability calculation was done using the renewability exergy index defined as the exergy ratio of the products to the sum of the non-renewable exergy, destroyed exergy, deactivation exergy and the emissions and waste exergy. The methodology was applied to three wastewater treatment processes: biological (aerobic and anaerobic) and physicochemical (CEPT) processes. The exergy indicators were calculated for each of these processes and it was observed that the process with the higher environmental performance and renewability values, considering the methane and sludge of process as useful effect, was the Facultative Lagoon UASB process, with values, respectively, of n<env,exerg>(0.983) and lambda(7.060). The results analysis showed that the proposed methodology is a useful tool in the evaluation and comparison of environmental performance and renewability of wastewater treatment processes.

O presente trabalho propõe uma metodologia científica, com critérios bem definidos, para avaliar e quantificar o desempenho ambiental e a renovabilidade de processos de tratamento de esgoto, numa base única: a exergia. O desempenho ambiental é quantificado através do cálculo da eficiência exergética ambiental, definida como a razão da exergia do efeito útil do processo pela exergia total consumida dos recursos humanos e naturais, incluindo todas as entradas exergéticas. O cálculo da renovabilidade é feito por meio do índice exergético de renovabilidade definido como como a razão entre a exergia dos produtos pela soma das exergias não renováveis, a exergia destruída, a exergia de desativação e a exergia das emissões e residuos. A metodologia foi aplicada a três processos de tratamento de esgoto: dois biológicos (aeróbio e anaeróbio) e um físico-químico (TQA). O cálculo dos indicadores exergéticos foi realizado para cada um destes processos e foi observado que o processo com maiores valores de desempenho ambiental e renovabilidade, considerando o metano e o lodo do processo como efeito útil, foi o processo RAFA Lagoa Facultativa, com valores respectivamente de n<exerg,amb> (0,983) e lâmbda(7,060). A análise dos resultados mostrou que a metodologia proposta é uma ferramenta útil na avaliação e comparação do desempenho ambiental e da renovabilidade de processos de tratamento de esgoto. / This work proposes a scientific methodology, with well defined criteria, to assess and quantify the environmental performance and renewability of wastewater treatment processes on a single base: the exergy. The environmental performance was measured by calculating the environmental exergy efficiency defined as the exergy ratio of the useful effect of the process to the total exergy consumed by human and natural resources, including all the exergy inputs. The renewability calculation was done using the renewability exergy index defined as the exergy ratio of the products to the sum of the non-renewable exergy, destroyed exergy, deactivation exergy and the emissions and waste exergy. The methodology was applied to three wastewater treatment processes: biological (aerobic and anaerobic) and physicochemical (CEPT) processes. The exergy indicators were calculated for each of these processes and it was observed that the process with the higher environmental performance and renewability values, considering the methane and sludge of process as useful effect, was the Facultative Lagoon UASB process, with values, respectively, of n<env,exerg>(0.983) and lambda(7.060). The results analysis showed that the proposed methodology is a useful tool in the evaluation and comparison of environmental performance and renewability of wastewater treatment processes.