Master of Science / Department of Grain Science and Industry / Carlos Campabadal Teran / The use of grain aeration as a tool to minimize post-harvest losses requires lower ambient temperature (≤ 20°C) and relative humidity (≤ 70%) conditions than what is usually available during the summer season in temperate climates and throughout the year in some tropical climate regions. Warm and moist conditions contribute to pest problems and increase dependence on chemical control for pest reduction as part of grain management strategies. The grain chilling technology is a non-chemical alternative to cool grain stored under high risk climatic conditions. For this research project, the grain chilling technology was tested in a 1,350-ton low moisture content wheat silo during the 2015 and 2016 summer harvests in Kansas. The grain temperature was lowered from a maximum of 39°C to a minimum of 17°C in less than 250 hours. The results showed that chilled grain maintained at temperatures under 20°C reduced the development rate of insect pests compared to grain stored at temperatures over 25°C and cooled with ambient aeration. However, the cost of grain chilling was calculated to be between 0.26 and 0.32 $/t higher than using ambient aeration. Through computer simulation it was possible to evaluate the performance of the grain chiller against four different ambient aeration strategies for paddy rice stored under the tropical climatic conditions of the North Pacific coast of Costa Rica. After six months of storage, the minimum grain temperature achieved through ambient aeration was 30.8°C using an aeration strategy based on a grain-ambient temperature differential greater than 10°C. Grain chilling lowered the average grain temperature from 35°C to below 15°C in 117 hours and the maximum average temperature it registered after six months of storage was 15.5°C. The economic evaluation of the simulated ambient aeration and chilling strategy determined that the operational costs of grain chilling were between 2 and 4 $/t lower than ambient aeration plus fumigation. However, the initial cost of the grain chiller made the net present cost (NPC) of the chilling strategy between 0.22 and 0.85 $/t higher than the cost of ambient aeration plus fumigation over a 10-year analysis. Several potential financial options were analyzed to make the grain chiller more economically feasible for a rice miller in Costa Rica. It was concluded that the grain chilling technology can reduce grain temperatures below 20°C in a relatively short period of time, which helps control insect populations and maintain grain quality during summer storage in temperate climates and in tropical climates. Utilizing grain chilling reduced operational costs between 78% and 88% when compared to using chemical control of pests. Additionally, it was determined that an initial cost of $74,700 for the grain chiller would require a 16% discount or at least 10,641 t to be chilled annually to make this technology viable for the Costa Rican rice milling industry. Leasing the grain chiller (ten equal payments of $10,926) or adding a premium sell price of 1 $/t to chilled rice would make this technology feasible compared to the traditional grain management strategies utilized in Costa Rica.

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A automação de uma central de água gelada é muito utilizada para reduzir o consumo energético de edificações comerciais ao controlar a operação dos seus componentes e consequentemente das vazões de ar e água em função da carga térmica. Considerando as estratégias de controle atualmente em uso, existe a possibilidade de melhorá-las por meio do controle das variáveis de temperatura do sistema (temperaturas de insuflação do ar, da água gelada e da água de condensação), que na maioria dos casos são mantidas fixas para as condições de dimensionamento do sistema ou alteradas apenas em função das condições externas. Estudos demonstram que o controle adequado de cada uma dessas temperaturas nas condições de operação momentâneas (condições climáticas e carga térmica), seja de forma individualizada ou integradas, pode proporcionar reduções significativas no consumo de energia do sistema de climatização. Dessa forma, o presente estudo avaliou os ganhos de uma automação isolada e integrada dessas três temperaturas em base anual para as condições climáticas brasileiras, implementando a automação em diferentes cidades representativas do zoneamento bioclimático brasileiro via simulação computacional utilizando o software EnergyPlus(TM) para uma edificação comercial típica. Os resultados obtidos para a automação integrada indicam reduções globais de consumo que variam com a condição climática entre 5,03% e 19,68% quando comparado com o controle de temperatura fixa, e quando comparado com um controle que varia apenas em função das condições externas as reduções variam entre 3,22% e 8,21%. Esses resultados demonstram que o controle sugerido é melhor que os modelos adotados como referência de mercado. / Automation of a central chilled-water plant is widely used to reduce the energy consumption of commercial buildings by controlling the operation of its components and consequently the air and water flow rates according to the thermal load. Considering the control strategies currently in use, there is a possibility to improve them by controlling the system temperature variables (air insufflation, cold and condensation water temperatures), which in most cases are fixed in system design conditions or variable only according to the external weather. Studies demonstrate that an adequate control of each of these temperatures under momentary operating conditions (climatic conditions and thermal load), whether in an individualized or integrated way, can provide significant reductions in the energy consumption of the HVAC system. Thus, the present study intends to evaluate the energy consumption gains of an individualized and integrated automation of the three variable temperatures on an annual basis for Brazilian climatic conditions, implementing automation for different cities representing the Brazilian bioclimatic zoning. Such evaluation was made by computer simulation using EnergyPlus(TM) software for a typical commercial building. The results obtained with the integrated automation show savings in global consumption that change with the weather between 5,03% and 19,68% when compared with a fixed control, and when compared with a control that varies according to weather conditions the savings are between 3,22% and 8,21%. These results show that the proposed control is better than both models adopted as market benchmarks.

A automação de uma central de água gelada é muito utilizada para reduzir o consumo energético de edificações comerciais ao controlar a operação dos seus componentes e consequentemente das vazões de ar e água em função da carga térmica. Considerando as estratégias de controle atualmente em uso, existe a possibilidade de melhorá-las por meio do controle das variáveis de temperatura do sistema (temperaturas de insuflação do ar, da água gelada e da água de condensação), que na maioria dos casos são mantidas fixas para as condições de dimensionamento do sistema ou alteradas apenas em função das condições externas. Estudos demonstram que o controle adequado de cada uma dessas temperaturas nas condições de operação momentâneas (condições climáticas e carga térmica), seja de forma individualizada ou integradas, pode proporcionar reduções significativas no consumo de energia do sistema de climatização. Dessa forma, o presente estudo avaliou os ganhos de uma automação isolada e integrada dessas três temperaturas em base anual para as condições climáticas brasileiras, implementando a automação em diferentes cidades representativas do zoneamento bioclimático brasileiro via simulação computacional utilizando o software EnergyPlus(TM) para uma edificação comercial típica. Os resultados obtidos para a automação integrada indicam reduções globais de consumo que variam com a condição climática entre 5,03% e 19,68% quando comparado com o controle de temperatura fixa, e quando comparado com um controle que varia apenas em função das condições externas as reduções variam entre 3,22% e 8,21%. Esses resultados demonstram que o controle sugerido é melhor que os modelos adotados como referência de mercado. / Automation of a central chilled-water plant is widely used to reduce the energy consumption of commercial buildings by controlling the operation of its components and consequently the air and water flow rates according to the thermal load. Considering the control strategies currently in use, there is a possibility to improve them by controlling the system temperature variables (air insufflation, cold and condensation water temperatures), which in most cases are fixed in system design conditions or variable only according to the external weather. Studies demonstrate that an adequate control of each of these temperatures under momentary operating conditions (climatic conditions and thermal load), whether in an individualized or integrated way, can provide significant reductions in the energy consumption of the HVAC system. Thus, the present study intends to evaluate the energy consumption gains of an individualized and integrated automation of the three variable temperatures on an annual basis for Brazilian climatic conditions, implementing automation for different cities representing the Brazilian bioclimatic zoning. Such evaluation was made by computer simulation using EnergyPlus(TM) software for a typical commercial building. The results obtained with the integrated automation show savings in global consumption that change with the weather between 5,03% and 19,68% when compared with a fixed control, and when compared with a control that varies according to weather conditions the savings are between 3,22% and 8,21%. These results show that the proposed control is better than both models adopted as market benchmarks.

This thesis develops a calibrated model of the Cal Poly Central Chilled Water Plant with Thermal Energy Storage for use in determining an optimal operating control strategy. The model was developed using a transient systems simulation program (TRNSYS) that includes plant performance and manufacturer data for the primary system components, which are comprised of pumps, chillers, cooling towers, and a thermal energy storage tank. The model is calibrated to the actual measured performance of the plant using the current control strategy as a baseline. By observing and quantifying areas for potential improvement in plant performance under conditions of high campus cooling load demands, alternative control strategies for the plant are proposed. Operation of the plant under each of these control strategies is simulated in the model and evaluated for overall energy and demand-usage cost savings. These results are used to recommend improvements in the plant’s current control strategy, as well as to propose an optimal control strategy that may be applied to reduce plant operating costs. The results of the model identify that the plant can perform more economically by employing more chiller power to charge the Thermal Energy Storage tank to higher capacities during overnight periods when the utility rates are lower. Staging the operation of the different chillers to more precisely follow the tank charges during these off-peak periods can ensure faster tank charging when its capacity may not be sufficient to meet the peak and part-peak cooling load demands. A proposed control strategy to accomplish this breaks the overnight Off-Peak rate period into three periods with separate control setpoints, which are designed to maintain the tank charge capacity at the minimum levels to be able to accommodate the daily campus cooling demands during peak and part-peak hours.

Cooling towers form an important part of chilled water systems and perform the function of rejecting the heat to the atmosphere. These systems are often not operated optimally, and cooling towers being an integral part of the system present a significant area to study and determine possible energy saving measures. Operation of cooling towers in economizer mode in winter and variable frequency drives (VFDs) on cooling tower fans are measures that can provide considerable energy savings. The chilled water system analysis tool (CWSAT) software is developed as a primary screening tool for energy evaluation for chilled water systems and quantifies the energy usage of the various components and typical measures that can be applied to these systems to conserve energy, all while requiring minimum number of inputs to analyze component-wise energy consumption and incurred overall cost. A careful investigation of the current model in CWSAT indicates that the prediction capability of the model at lower wet bulb temperatures and at low fan power is not very accurate. A new model for accurate tower performance prediction is imperative, since economizer operation occurs at low temperatures and most cooling towers come equipped with VFDs. In this thesis, a new model to predict cooling tower performance is created to give a more accurate prediction of energy savings for a tower. Further the economic feasibility of having additional cooling tower capacity to allow for economizer cooling, in light of reduced tower capacity at lower temperatures is investigated.

The Paris Agreement has ambitious targets to limit the global warming below 1.5 °Cin the 21st century. This goal is reflected in the national climate targets, for example, Sweden aims to achieve net zero greenhouse gas emissions by 2045, and thereafter achieve negative emissions. One of the pivotal ways to achieve these goals is by applying the mature bioenergy with carbon capture and storage (BECCS) technology to large-scale industries that emit CO2. Around 6% of the global emissions arise from the pulp and paper industry making them one of the largest localized emitters of biogenic CO2. This makes them suitable for retrofitting BECCS technologies and post-combustion capture (PCC) is one among them. This study presents a techno-economic assessment of an absorption-based PCC unit in SCA Östrand pulp mill. Chemical absorption using MEA and chilled ammonia process (CAP) using NH3 as the solvent are considered in this study. For both the processes, mass and energy balances using Aspen HYSYS were done and validated against published data in literature. Heat integration by applying excess or waste heat from the mill is also considered in this work. CO2 capture from flue gas originating from various emission sources in the mill (recovery boiler, lime kiln and multi-fuel boiler) are considered in different combinations in the analysis. The main key performance indicator (KPI) evaluated in this work is the cost of CO2capture for all the different cases for both the MEA- and chilled NH3-based absorption processes. The minimum cost of CO2 capture for MEA-based absorption process was found to be in the range 37-41 €/tCO2 and for CAP, it was found to be in the range 73-81 €/tCO2. For MEA-based absorption process, the excess low pressure steam from the mill satisfies the steam demand in all the cases, except the one where CO2 is captured from all the three emission sources. For CAP, sufficient excess low pressure steam is present in the mill for all the capture cases due to a lower reboiler duty compared to MEA-based absorption process. An optimal process configuration and capture scenario for the existing design conditions in the mill are derived and justified. A sensitivity analysis was carried out to find the associated bottlenecks from the breakdown of the cost of CO2 capture for each process. The overall BECCS cost is also sensitive to CO2 transport & storage costs. However, it is also clear that incentives for negative emissions will make BECCS an attractive solution for the pulp and paper industry.

The UK building stock accounts for about half of all energy consumed in the UK. A large portion of the energy is consumed by nondomestic buildings. Offices and retail are the most energy intensive typologies within the nondomestic building sector, typically accounting for over 50% of the nondomestic buildings’ total energy consumption. Heating, ventilating and air conditioning (HVAC) systems are the largest energy end use in the nondomestic sector, with energy consumption close to 50% of total energy consumption. Different HVAC systems have different energy requirements when responding to the same building heating and cooling demands. On the other hand, building heating and cooling demands depend on various parameters such as building fabrics, glazing ratio, building form, occupancy pattern, and many others. HVAC system energy requirements and building energy demands can be determined by mathematical modelling. A widely accepted approach among building professionals is to use building energy simulation tools such as EnergyPlus, IES, DOE2, etc. which can analyse in detail building energy consumption. However, preparing and running simulations in such tools is usually very complicated, time consuming and costly. Their complexity has been identified as the biggest obstacle. Adequate alternatives to complex building energy simulation tools are regression models which can provide results in an easier and faster way. This research deals with the development of regression models that enable the selection of HVAC systems for office buildings. In addition, the models are able to predict annual heating, cooling and auxiliary energy requirements of different HVAC systems as a function of office building heating and cooling demands. For the first part of the data set development used for the regression analysis, a data set of office building simulation archetypes was developed. The four most typical built forms (open plan sidelit, cellular sidelit, artificially lit open plan and composite sidelit cellular around artificially lit open plan built form) were coupled with five types of building fabric and three levels of glazing ratio. Furthermore, two measures of reducing solar heat gains were considered as well as implementation of daylight control. Also, building orientation was included in the analysis. In total 3840 different office buildings were then further coupled with five different HVAC systems: variable air volume system; constant air volume system; fan coil system with dedicated air; chilled ceiling system with embedded pipes, dedicated air and radiator heating; and chilled ceiling system with exposed aluminium panels, dedicated air and radiator heating. The total number of models simulated in EnergyPlus, in order to develop the input database for regression analysis, was 23,040. The results clearly indicate that it is possible to form a reliable judgement about each different HVAC system’s heating, cooling and auxiliary energy requirements based only on office building heating and cooling demands. High coefficients of determination of the proposed regression models show that HVAC system requirements can be predicted with high accuracy. The lowest coefficient of determination among cooling regression models was 0.94 in the case of the CAV system. HVAC system heating energy requirement regression models had a coefficient of determination above 0.96. The auxiliary energy requirement models had a coefficient of determination above 0.95, except in the case of chilled ceiling systems where the coefficient of determination was around 0.87. This research demonstrates that simplified regression models can be used to provide design decisions for the office building HVAC systems studied. Such models allow more rapid determination of HVAC systems energy requirements without the need for time-consuming (hence expensive) reconfigurations and runs of the simulation program.

The increasing price of oil and the destabilisation of the world’s climate are urging governments, businesses and individuals to constantly investigate energy-efficient technologies and methodologies and pursue the adoption of energy efficiency programmes in a global effort to reduce energy consumption, greenhouse gas emissions and ultimately energy costs. In New Zealand, one of the biggest industrial energy efficiency projects was started in 2002 by a multinational dairy company, the Fonterra Co-operative Group, in partnership with the energy service company Demand Response Ltd; the project currently aims at reducing by 15% the energy costs at all Fonterra’s major production sites throughout the country. This thesis, undertaken as part of the above project, examines the development and implementation of a structured and integrated energy monitoring and targeting methodology (M&T) for the most efficient operation of all Fonterra’s chilled water systems, with an initial focus on the ones installed at Clandeboye, one of the Fonterra’s sites involved in the energy saving project. A data collection system (Insite) was already in place at Clandeboye to enable storage and analysis of some of the site’s utility metering data. After identification of key chilled water system components and definition of data requirements for M&T purposes, an analysis of past energy consumption trends (based on multiple regression calculations) was carried out to develop an historical benchmark of the energy used, compare it with current energy performance and thus identify opportunities for future improvements. The creation of an M&T reporting system for presenting findings to operators and management was the last essential part of the thesis development. The study has highlighted that the robustness of the proposed regression model was badly affected by the unreliability of the existing data collection system and the uncertainty associated with poorly documented changes to operating conditions/plant configuration that had occurred over time. The conclusion is that, while the developed M&T methodology is theoretically valid and readily applicable, further developments are necessary (and recommended) to make it suitable for other similar systems.

Fossil fuels are the major sources of electrical power generation in the world. Among all fossil fuels, oil is considered as the most sought-after fuel. The burden on countries that provide subsidized electricity produced from oil-fired power plants is noteworthy. Kuwait is a notable example of these countries. Electricity in Kuwait is heavily consumed by residential air conditioning, which comprises 60% of the total electricity generated at peak times on a hot summer day. From this perspective, residential air conditioning in Kuwait was selected to undergo further investigation regarding low energy air conditioning choices. Three solutions to control the rapid growth of demand for electricity by residential air conditioning are examined. The first solution investigated assesses the orientation and grouping of houses in Kuwait in order to examine their effect on cooling load and electrical energy consumption for future houses. Four residential cases were developed; each case comprises six typical houses. The cases identified are: (1) single block facing east-west, (2) single block facing north-south, (3) double block facing east-west and (4) double block facing north-south. Cooling loads are calculated using the DesignBuilder building thermal simulation software. Case (2) is found to have the smallest cooling load, and case (1) the largest. The estimated savings from applying case (2) compared to the average of the four cases for the future houses planned to be built by the government by the year 2016 (i.e. approximately 20,000 houses) are found to be approximately .US 33 million of power system capital costs, 15 GWh per year of electrical energy consumption and 11 kilotons per year of CO2 emissions. In the second solution, a lifecycle cost analysis is performed to evaluate the economic feasibilities of electricity driven chilled water system compared to predominant air conditioning system in Kuwaiti houses which is Packaged- Direct Expansion. The study considers the total cash paid by the consumer and the total cash paid by the government, since electricity is subsidized in Kuwait. The study finds that the chilled water system is not cost-effective for consumers due to high installation cost. However, a chilled water system would be cost-effective for the government because it consumes 40%less electrical energy than Packaged-DX. So, the study suggests subsidising the installation of chilled water systems so that the installation cost to the consumer is the same as for Packaged-DX systems. In the third solution, the study examines the viability of a single-effect LiBr absorption chiller driven by steam extracted from the steam turbine in the configuration of a combined cycle power plant (CCPP). The analysis shows that CCPP with absorption chiller yields less net electrical power available to utility grid compared to similar CCPP giving electricity to the grid and to Direct-Expansion air conditioning systems for the same cooling requirements. The reasons for that are the reduction in steam turbine power output resulted from steam extraction, and the amount of electrical energy required to operate the configuration of CCPP with absorption chiller.