The development and implementation of technologies that improves Heating Ventilation & Air Conditioning (HVAC) system efficiency, including unique waste heat recovery methods, are sought while considering financial constraints and benefits. Recent studies have found that through the use of advanced waste heat recovery systems, it is possible to reduce building’s energy consumption by 30%. Oscillating heat pipes (OHP) exists as a serpentine-arranged capillary tube, possesses a desirable aerodynamic form factor, and provides for relatively high heat transfer rates via cyclic evaporation and condensation of an encapsulated working fluid with no internal wicking structure required. In last two decade, it has been extensively investigated for its potential application in thermal management of electronic devices. This dissertation focuses on the application of OHP in waste heat recovery systems. To achieve the goal, first a feasibility study is conducted by experimentally assessing a nine turn copper-made bare tube OHP in a typical HVAC ducting system with adjacent air streams at different temperatures. Second, for a prescribed temperature difference and volumetric flow rate of air, a multi-row finned OHP based Heat Recovery Ventilator (OHP-HRV) is designed and analyzed for the task of pre-conditioning the intake air. Additionally, the energy and cost savings analysis is performed specifically for the designed OHP-HRV system and potential cost benefits are demonstrated for various geographical regions within the United States. Finally, an atypically long finned OHP is experimentally investigated (F-OHP) under above prescribed operating condition. Helical fins are added to capillary size OHP tubes at a rate of 12 fins per inch (12 FPI), thereby increasing the heat transfer area by 433%. The coupled effect of fins and oscillation on the thermal performance of F-OHP is examined. Also, F-OHP’s thermal performance is compared with that of bare tube OHP of similar dimension and operating under similar condition. It was determined that OHP can be an effective waste heat recovery device in terms of operational cost, manufacturability, thermal and aerodynamic performance. Moreover, it was also determined that OHP-HRV can significantly reduce energy consumption of a commercial building, especially in the winter operation.

The ever-growing demand for cyber-physical infrastructures has significantly affected worldwide energy consumption and environmental sustainability over the past two decades. Although the average heat load of the computing infrastructures has increased, the supportive capacity of cooling infrastructures requires further improvement. Consequently, energy-efficient cooling architectures, real-time load management, and waste heat utilization strategies have gained attention in the data center (DC) industry. In this dissertation, essential aspects of cooling system modularization, workload management, and waste-heat utilization were addressed. At first, benefits of several legacy and modular DCs were assessed from the viewpoint of the first and second laws of thermodynamics. A computational fluid dynamics simulation-informed thermodynamic energy-exergy formulation captured equipment-level inefficiencies for various cooling architectures and scenarios. Furthermore, underlying reasons and possible strategies to reduce dominant exergy loss components were suggested. Subsequently, strategies to manage cooling parameters and IT workload were developed for the DCs with rack-based and row-based cooling systems. The goal of these management schemes was to fulfill either single or multiple objectives such as energy, exergy, and computing efficiencies. Thermal models coupled to optimization problems revealed the non-trivial tradeoffs across various objective functions and operation parameters. Furthermore, the scalability of the proposed approach for a larger DC was demonstrated. Finally, a waste heat management strategy was developed for new-age infrastructures containing both air- and liquid-cooled servers, one of the critical issues in the DC industry. Exhaust hot water from liquid-cooled servers was used to drive an adsorption chiller, which in turn produced chilled water required for the air-handler units of the air-cooled system. This strategy significantly reduced the energy consumption of existing compression chillers. Furthermore, economic and environmental assessments were performed to discuss the feasibility of this solution for the DC community. The work also investigated the potential tradeoffs between waste heat recovery and computing efficiencies. / Thesis / Doctor of Philosophy (PhD)

Analytical, closed-form solutions governing thermoelectric behavior are derived. An analytical model utilizing a thermal circuit is presented involving heat transfer into, through, out of, and around a thermoelectric device. A nondimensionalization of the model is presented. Linear heat transfer theory is applied to the model to obtain a series of closed form equations predicting net power output for the thermoelectric device. Fluid streams flowing through shrouded heat sinks with square pin fins are considered for the thermal pathways to and from the device. Heat transfer and pressure drop are characterized in a manner conducive to an analytical model using previously published experimental results. Experimental data is presented which validates and demonstrates the usefulness of the model in predicting power output for commercially available thermoelectric generators. A specific design for a thermoelectric power harvester is suggested consisting of a pattern of thermoelectric generators. An economic model for calculating payback time is developed. An optimization process is demonstrated that allows for the payback time of such a system to be minimized through optimization of the physical design of the system. It is shown that optimization of the thermal pathways dramatically reduces payback time. Optimized design of a system is discussed in light of theoretical cases with feasible payback times.

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The global hydrogen demand is steadily increasing, and one way of accelerating the green hydrogen supply is to stimulate the green hydrogen economy. Utilization of waste heat from hydrogen production can increase the profitability of produced green hydrogen. Therefore, the aim of this study is to propose a system for integration of waste heat on the district heating (DH) network in Luleå, Sweden. Furthermore, an economic evaluation of the proposed system was conducted. In this study, the system was developed and investigated for two cases i.e. for a PEM and alkaline electrolyzer with an installed capacity of 100 MW. A large-scale heat pump and a heat exchanger were further added to the system to integrate the waste heat on the DH-network, while simultaneously providing cooling to the electrolyzer stack. The system was modelled for static conditions in the software MATLAB, with retrieved hourly DH data from Luleå Energi. The results showed that 203 060 MWhth can be extracted from the PEM electrolyzer with a waste heat temperature of 79 oC, while 171 770 MWhth can be integrated on the DH network annually. For the alkaline electrolyzer, 310 630 MWhth can be extracted at a waste heat temperature of 80 oC, while 226 220 MWhth can be integrated on the DH annually. The overall system efficiency is 94.7 % and 88.4 % for PEM and alkaline connected systems, respectively. Furthermore, the Levelized Cost of Heat (LCOH) is 0.218 SEK/kWhth and 0.23 SEK/kWhth for a PEM and alkaline connected system, respectively. For future scenarios with fourth generation of DH-networks, it is predicted that the LCOH can reach 0.018 SEK/kWth for a PEM electrolyzer system, and 0.017 SEK/kWth for an alkaline electrolyzer system. One conclusion that can be drawn from this study is that the utilized heat from the proposed system is price competitive in comparison with other thermal energy sources.

In recent times, there has been an explosion in the need for high-density computing and data processing. As a result the Internet and Communication Technology (ICT) demand on global energy resources has tripled in the last five years. Edge computing - bringing computing power close to the user, is set to be the cornerstone of future communication and information transport, satisfying the demand for instant response times and zero latency needed for applications such as 5G, self-driving vehicles, face recognition, and much more. The Micro Data Centre (micro DC) is key hardware in the shift to edge computing. Being self-contained, with in-rack liquid cooling systems, these micro data centres can be placed anywhere they are needed the most - often in areas not thought of as locations for datacentres, such as offices and housing blocks. This presents an opportunity to make the ICT industry greener and contribute to lowering total global energy demand, while fulfilling both the need for data processing and heating requirements. If a solution can be found to capture and utilise waste heat from the growing number of micro data centres, it would have a massive impact on overall energy consumption. This project will explore this potential synergy through investigating two different ways of utilising waste heat. The first being supplying waste heat to the District Heating network (Case 1), and the second using the micro DC as a ’data furnace’ supplying heat to the near vicinity (Case 2 and 3). Two scenarios of differing costs and incomes will be exploredin each case, and a sensitivity analysis will be performed to determine how sensitive each scenario is to changing internal and external factors. Results achieved were extremely promising. Capturing waste heat from micro data centres, and both supplying the local district heating network as well as providing the central heating of the near vicinity, is proving to be both economically and physically viable. The three different business models (’Cases’) created not only show good financial promise, but they demonstrate a way of creating value in a greener way of computing and heat supply. The amount of waste heat able to be captured is sufficient to heat many apartments in residential blocks and office buildings, and the temperatures achieved have proven to be sufficient to meet the heating requirements of these facilities, meaning no extra energy is required for the priming of waste heat. It is the hope that the investigations and analyses performed in this thesis will further the discussion around the utilisation of waste heat from lower energy sources, such as micro DCs, so that one day, potential can become reality. / På senare har tid har det skett en explosion i behovet av databehandling och databehandling med hög densitet. Som ett resultat har Internet- och kommunikationstekniksektorns (ICT) efterfråga på globala energiresurser tredubblats under de senaste fem åren. Edgecomputing för datorkraften närmre användaren och är hörnstenen i framtida kommunikation och informationsflöde. Omedelbar svarstid och noll latens som behövs för applikationersom 5G, självkörande fordon, ansiktsigenkänning och mycket mer tillfredställs av att datorkraften förs närme användaren. Micro Data Center är nycklen i övergången till edge computing. Eftersom att MicroData Center är fristående med inbyggda kylsystem kan de placeras där de behövs mest -ofta i områden som inte betraktas som platser för datacenter som exemeplvis kontor och bostadshus. Detta möjliggör för ICT-branschen att bli grönare och bidra till att sänka det totala globala energibehovet, samtidigt som behovet av databehandling kan tillgodoses. Om enlösning kan hittas för att fånga upp och använda spillvärme som genereras från växande antalet Micro Data Center, skulle det ha en enorm inverkan på den totala energiförbrukningen. Detta projekt kommer att undersöka potentiella synergier genom att undersöka två olikasätt att utnyttja spillvärme. Den första är att leverera spillvärme till fjärrvärmenätet (Case 1), och det andra att använda Micro Data Center som en "Data Furnace" som levererar värme till närområdet (Case 2 och 3). Två scenarier med olika kostnader och intäkter kommer att undersökas i varje Case och en känslighetsanalys kommer att utföras för att avgöra hur känsligt varje scenario är för ändrade interna och externa faktorer. Resultaten som uppnåtts är extremt lovande. Att fånga upp spillvärme från Micro Data Center och leverera till antingen det lokala fjärrvärmenätet eller nyttja spillvärmen lokalt har visat sig vara både ekonomiskt och fysiskt genomförbart. De tre olika affärsmodellerna (’Cases’) som skapats visar inte bara positivt ekonomiskt utfall, utan också ett sätt att skapa värde genom att på ett grönare sätt processa och lagra data och samtidigt värma städer. Mängden spillvärme som kan fångas upp är tillräcklig för att värma upp många lägenheter i bostadshus och kontorsbyggnader. Temperaturen på spillvärmen har visat sig vara tillräcklig för att uppfylla uppvärmningskraven i dessa anläggningar, vilket innebär att ingen extra energi krävs för att höja temperturen av spillvärme. Förhoppningen är att de undersökningar och analyser som utförs i denna rapport kommer att främja diskussionen kring utnyttjande av spillvärme från lägre energikällor, såsom Micro Data Center.