WASTE HEAT VALORIZATION FROM DATA CENTERS: DESIGN OF AN ORC AND INTEGRATION WITH OTHER WASTE HEAT VALORIZATION SYSTEMS

In the past years, since many new data centers have been built, the overall electricity consumption of this kind of infrastructure has increased significantly. The share of electricity consumption on total electricity demand in Europe is supposed to pass from less than 4% in 2022 to more than 5% in 2026 [1]. According to IEA data centers in 2022 accounted for 0.6% of total GHG emissions and for 0.9% of energy-related GHG emissions [2]. A potential solution to boost the overall energy efficiency of data centers is Waste Heat Recovery and reutilization. The primary drivers of data centres electricity demand are the cooling systems and the servers themselves, with each typically accounting for 40% of the total consumption [1]. Regarding the extraction of heat from ICT equipment, immersion cooling is a liquid cooling method in which the cooling medium is in close and direct contact with ICT equipment. This technique requires lower electricity consumption than traditional computer room air cooling. The heat absorbed by the cooling medium can be used for instance to supply a District Heating System, or can be released in another fluid for direct exploitation. The scope of this thesis is to design an Organic Rankine Cycle (ORC), fed by waste heat from a data center and to develop a preliminary working logic for the integration of it with other waste heat recovering systems. Regarding the design of the ORC, firstly the selection of the working fluid has been performed. R1234yf has resulted to be one of the best candidates and has been chosen for the further analyses. Regarding the architecture, a basic architecture for the ORC has been chosen. The design of the ORC system has resulted in a thermal efficiency having a maximum value of 6.4%, which is a reasoning value compared to the ones that can be found in literature. Later the design of the system has been performed, in particular the sizing of the piping and of the various component (pump, boiler, turbine, electric generator, condenser and refrigerant collector tank) has been performed. Furthermore the engineering documentation required for the production of the system has been compiled. In particular this documentation includes the Battery Limits, Fluids List, Block Flow Diagram, Process Flow Diagram, Mass and Energy Balance, Process Data Sheet, Mechanical Data Sheet, Equipment List, Instrument list and Valve list. The ORC system is part of a larger system which is being developed by the company where this thesis has been developed together with other companies from various parts of the EU. The EU project is named MODERATOR. The system that is to be designed is composed by a space heating system, a domestic hot water system, a thermal energy storage, the ORC and other heat recovering systems that have not been considered in this work. The first two systems are supposed to supply heating to the data center, while the thermal energy storage is meant to store surplus heat from the data center in order to use it when needed both inside the data center and for other purposes and the ORC produces electricity which can be used inside the data center. These four systems are meant to be integrated in order to maximize the energy recovery from waste heat. The preliminary development of the logic of the integrated system is part of this thesis, together with the production of some engineering documentation for the integrated system comprehending the battery limits, the block flow diagram and the process flow diagram.