De nos, jours avec la démocratisation des équipements électroniques et l’explosions des services informatiques proposés sur le web, la consommation des datacenters devient un enjeu énergétique et économique majeur. Ce terme qui peut être traduit par « centre de calcul », désigne les infrastructures qui hébergent et font fonctionner en permanence des serveurs informatiques. Son rôle est de fournir aux équipements électroniques un environnement thermique adapté, ainsi qu’une alimentation électrique stable de manière à assurer une très grande sécurité de fonctionnement. Mais l’activité permanente des serveurs génère de grandes quantités de chaleurs, et un refroidissement permanent est nécessaire. Cette étude à pour objectif de mieux comprendre les phénomènes physiques qui interviennent dans le fonctionnement des datacenters afin d’apporter des solutions pour optimiser leur fonctionnement et diminuer leur consommation. A l’aide de simulations numériques, nous étudions les écoulements d’air et les transferts de chaleur qui interviennent dans la salle informatique, et nous proposons un nouveau modèle numérique qui permet de simuler le comportement des serveurs de nouvelle génération. Puis, grâce à une méthode de type POD, couplée au logiciel TRNSYS, nous développons un modèle « transversal » capable de simuler le fonctionnement complet d’un centre de calcul depuis les équipements informatiques, jusqu’au système de production d’air froid. Finalement, ce dernier est employé pour concevoir et tester un système de régulation adaptatif qui permet de réduire significativement les consommations d’énergie. / Nowadays, with the constant evolution of Information Technology (IT) equipments, the energy consumption of datacenter over the world becomes a major concern. These infrastructures are designed to provide an adapted thermal environment and an uninterrupted power supply to the IT servers, in order to guarantee a high level of reliability. However, the constant activity of electronic equipments releases a large amount of heat, and requires a constant cooling. Thus the objective of this work is to study the physical phenomena involved in an operating datacenter, in order to optimize the process and to reduce its energy consumption. Using numerical simulation, we study the air flow and the heat transfers happening in the servers’ room. To quantify the impact of new generation servers on the cooling process, we propose a numerical model that simulates the behavior of “blade” server. Then, using a Proper Orthogonal Decomposition (POD) method linked to the software TRNSYS, we propose a new “transversal” model, that simulates a datacenter behavior from the servers to the cooling plant. This model is used to develop a new adaptive regulation strategy, which constantly optimizes the system in order to ensure a safe thermal environment, and provides large energy savings.

Rapporten redovisar resultatet från energikartläggningen samt utredningen om kylsystemet som genomförts på glassgrossisten i Umeå. En övergripande studie av hela verksamheten med samtliga tekniska system har utförts. Grossisten ämnar minska sin klimatpåverkan som orsakas av energianvändning i fastigheten samt läckage av köldmedium från kylanläggning och fordonskylaggregat. Grossisten förbrukar frånsett bränsle till lastbilarna endast elenergi. Följande energiaspekter har framkommit som betydande för verksamheten:   Total energianvändning                            394 MWh Kylanläggning                                          258 MWh      (65% av total energianvändning) Kylaggregat lastbilar                                75   MWh      (19% av total energianvändning) Kylanläggningen utgör en stor del av grossistens totala energianvändning och måste efter beslut från EU:s f-gasförordning åtgärdas innan år 2020 då ett service- och underhållsförbud träder i kraft för det befintliga köldmediet.   Utredningen avser besvara hur man bäst tillmötesgår detta förbud, konvertera och ersätta köldmediet för fortsatt drift av den befintliga anläggningen eller investera i en ny klimatneutral kylanläggningstyp. Efter inspektion av kylsystemet samt genomförd studie om kylanläggningar och köldmedier rekommenderas att investera i en ny klimatneutral transkritisk koldioxidkylanläggning. En prisuppskattning är gjord och har uppskattats kosta mellan 1,3 – 1,5 mkr.   Transmission (värmeförluster genom klimatskal) och infiltration (ofrivillig ventilation) står för 50 % av den totalt avgivna energin. Avgiven värmeenergi via kylanläggningens kondensorfläktar på taket står för 18 % och lastbilarnas kylaggregat 19 %. Förslag på effektiviseringsåtgärder som framtagits efter energikartläggningen är följande: Installera en luftridå för att minska infiltrationsflöden i portöppning mellan frys- och varmlager. Installera timerstyrda motorvärmare på gårdsplanen. Tillsätta ett nytt ventilationsaggregat med roterande värmeväxlare Täta kring nödutgången på fryslagret Utförs alla effektiviseringsåtgärder beräknas en minskning av energianvändningen med 42 MWh, detta utgör 11% av grossistens totala energitillförsel.   I samband med en installation av en transkritisk koldioxidkylanläggning finns stora möjligheter att installera systemet så att den högtempererade kondensorvärmen kan tillvaratas för värmeåtervinning. Den heta gasvärmen kan förvärma tilluften i ventilationsaggregaten samt värma tappvarmvatten. Detta skulle bidra till att sänka det totala energibehovet ytterligare. / The report presents the results of the energy mapping and the investigation of the cooling system performed at the ice cream wholesaler GB Glass in Umeå. An overall study of the entire operation with all technical systems has been performed. GB glass aims to reduce its climate impact caused by energy consumption in the property as well as leakage of refrigerant from the cooling system and vehicle refrigeration equipment. Except fuel for trucks the wholesaler only consumes electricity. The following energy aspects have been identified as significant for the business:   Total energy use                                       394 MWh Cooling system plant                                258 MWh      (65% of total total energy use) Refrigeration trucks                                 75   MWh      (19% of total total energy use) The cooling system plant constitutes a major part of the wholesaler's total energy use and must be rectified due to a decision by the EU's F-Gas Regulation by 2020 when a service and maintenance prohibition carries out for the existing refrigerant. The investigation concerns how to best accommodate this prohibition, convert and replace the refrigerant for continued operation of the existing plant or invest in a new climate-neutral type. After inspection of the cooling system and completed study of cooling systems and refrigerants, it is recommended to invest in a new climate-neutral transcritical carbon dioxide plant. A price estimate has been made and has been estimated to cost between 1.3 - 1.5 million.  Transmission (thermal loss through climate scale) and infiltration (involuntary ventilation) accounts for 50% of the total energy delivered. Ceded heat energy by the cooling plants condenser fans on the roof accounts for 18% and the truck's cooling units 19%. Proposals for efficiency enhancements developed after the energy survey are as follows:  Install an air curtain to reduce infiltration flows in the doorway between freezing and storage Install timer-controlled engine heaters on the yard Add a new ventilation unit with rotary heat exchanger Seal around the emergency exit on the freezer Performing all efficiency measures is estimated to reduce energy consumption by 42 MWh, which represents 11% of the wholesaler's total energy supply. In connection with the installation of a transcritical carbon dioxide cooling system, there is a great opportunity to install the system so that the high temperature condenser heat can be used for heat recovery. The hot gas heater can preheat the supply air in the ventilation units as well as heating the tap water. This would help to further reduce the overall energy demand.

Demand for cooling has been increasing around the world for the last couple of decades due to various reasons, and it will continue to increase in the future particularly in developing countries. Traditionally, cooling demand is met by decentralised electrically driven appliances which affect energy, economy and environment as well. District Cooling Plant (DCP) is an innovative alternative means of providing comfort cooling. DCP is becoming an essential infrastructure in modern city development owning to many benefits compared to decentralized cooling technology. Demand Response Management (DRM) is largely applied for Demand Side management of electrical grid. Demand of electrical energy is closely connected with the demand of alternative form of energy such as heating, cooling and mechanical energy. Therefore, application of DR concept should be applied beyond the electrical grid; in particular, it could be applied to any interconnected district energy systems. District Cooling Plant is one of a potential candidate and Demand Response management solutions can be applied to DCP for sustainable operation. The study of demand response and its applicability has not been attempted previously for district cooling systems. To our knowledge, this is the first attempt to evaluate its applicability and economical feasibility. This thesis focused on some of the DR objectives which have the potential to implement for DCP of a mixed-use city. General published data on mixed use city developments and a specific city in Dubai was taken as a case study to show the usefulness on DRM objectives. This study primarily addressed the issues related to load management. The findings are: DRM creates greater flexibility in demand management without compromising service levels. Also it reduces the operation cost and impact to environment. However implementation is a big challenge. Therefore implementation strategies are also proposed as a part of recommendation which includes a generic model for demand response management. Moreover, a review is provided on key enabling technologies that are needed for effective demand response management. Finally this thesis concludes with recommendations for prospective applications and potential future works.

<div>The internal and external interactions between the complex structural and behavioral characteristics of the system of interest and the surrounding environment result in unpredictable emergent behaviors. These emergent behaviors are not well understood, especially when modeled using the traditional top-down systems engineering approach. The intrinsic nature of current complex systems has called for an elegant solution that provides an integrated framework in Model-Based Systems Engineering. A considerable gap exists to integrate system engineering activities and engineering analysis, which results in high risk and cost. This thesis presents a framework that incorporates indefinite and definite modeling aspects that are developed to determine the complexity that arises during the development phases of the system. This framework provides a workflow for modeling complex systems using Systems Modeling Language (SysML) that captures the system’s requirements, behavior, structure, and analytical aspects at both problem definition and solution levels. This research introduces a new level/dimension to the framework to support engineering analysis integrated with the system architecture model using FMI standards. A workflow is provided that provides the enabling methodological capabilities. It starts with a statement of need and ends with system requirement verification. Detailed traceability is established that glues system engineering and engineering analysis together. Besides, a method is proposed for predicting the system’s complexity by calculating the complexity index that can be used to assess the complexity of the existing system and guide the design and development of a new system. To test and demonstrate this framework, a case study consisting of a complex district cooling system is implemented. The case study shows the framework’s capabilities in enabling the successful modeling of a complex district cooling system. The system architecture model was developed using SysML and the engineering analysis model using Modelica. The proposed framework supports system requirements verification activity. The analysis results show that the district chiller model developed using Modelica produces chilled water below 6.6 degrees Celsius, which satisfies the system requirement for the district chiller system captured in the SysML tool. Similarly, many such requirement verification capabilities using dynamic simulation integration with the high-level model provides the ability to perform continuous analysis and simulation during the system development process. The systems architecture complexity index is measured for the district cooling case study from the black-box and white box-perspective. The measured complexity index showed that the system architecture’s behavioral aspect increases exponentially compared to the structural aspect. The systems architecture’s complexity index at black-box and white-box was 4.998 and 67.3927, respectively.</div>

Arbetet baseras på en kylanläggning som installerats på ett biogas företag, som till en början var tänkt som ett pilotprojekt men som nu används fullt ut i anläggningen. Projektet var inte utvärderat eller dokumenterat och vilken effekt som överförs var obekant. Arbetets innebörd var att beräkna effekten samt dokumentera systemet i form av både beräkningar, ritning och eventuella effektiviserings områden. Beräkning gjordes via entalpi skillnaden som togs ut över involverade värmeväxlare, samt flödet som togs ut via en reglerventil med hjälp av ett mätinstrument. Ritning gjordes via programmet Visio utifrån anläggningens nuvarande konstruktion. Resultatet för kyleffekten som överfördes beräknades fram via flöde och entalpi, med resultatet 14,03kW över båda värmeväxlarna. Även beräkning på vad en potentiell förbättring av isolering i rörsystemet skulle kunna bidra med där utifrån beräkningarna skulle energibesparingen kunna fördubblas gentemot nuvarande. / The work is based on a cooling plant installed at a biogas company, which was initially intended as a pilot project but is now fully used in the plant. It is not evaluated or documented and how much power is transmitted is unknown. The meaning of the work is to find out the effect and document the system in the form of both calculations, drawing and any areas of efficiency. Calculation was made via enthalpy the difference that was taken out over the heat exchangers involved, as well as the flow that was taken out via a control valve with the help of a measuring instrument. Drawing was made via the Visio program based on the facility's current design. The result for the cooling power that was transferred was calculated via flow and enthalpy, where the result was 14.03 kW over both heat exchangers. Calculation of what a potential improvement of insulation of the pipe system could contribute, based on the calculations, the energy savings could be doubled compared to the current one.