Energy management for user’s thermal and power needs: A survey <s> A.4. Energy hubs <s> This paper presents an approach for combined optimization of coupled power flows of different energy infrastructures such as electricity, gas, and district heating systems. A steady state power flow model is presented that includes conversion and transmission of an arbitrary number of energy carriers. The couplings between the different infrastructures are explicitly taken into account based on the new concept of energy hubs. With this model, combined economic dispatch and optimal power flow problems are stated covering transmission and conversion of energy. A general optimality condition for optimal dispatch of multiple energy carriers is derived, and the approach is compared with the standard method used for electrical power systems. Finally, the developed tools are demonstrated in examples <s> BIB001 </s> Energy management for user’s thermal and power needs: A survey <s> A.4. Energy hubs <s> MES (multi-energy systems) whereby electricity, heat, cooling, fuels, transport, and so on optimally interact with each other at various levels (for instance, within a district, city or region) represent an important opportunity to increase technical, economic and environmental performance relative to “classical” energy systems whose sectors are treated “separately” or “independently”. This performance improvement can take place at both the operational and the planning stage. While such systems and in particular systems with distributed generation of multiple energy vectors (DMG (distributed multi-generation)) can be a key option to decarbonize the energy sector, the approaches needed to model and relevant tools to analyze them are often of great complexity. Likewise, it is not straightforward to identify performance metrics that are capable to properly capture costs and benefits that are relating to various types of MES according to different criteria. The aim of this invited paper is thus to provide the reader with a comprehensive and critical overview of the latest models and assessment techniques that are currently available to analyze MES and in particular DMG systems, including for instance concepts such as energy hubs, microgrids, and VPPs (virtual power plants), as well as various approaches and criteria for energy, environmental, and techno-economic assessment. <s> BIB002
An energy hub can be described as a ''block'' that exchanges energy with the neighboring systems via input and output ports. Inputs can be in the form of both primary energy, e.g., natural gas, and secondary energy coming from external grids, such as electricity or district heat. Outputs are usually electricity and heat, locally produced and converted by means of generation and transformation units, such as transformers, CCHP systems, and boilers BIB001 BIB002 . Both thermal and electric storage are often included in the energy hub model as well, which is traditionally described by a coupling matrix that determines the outputs given the inputs and generation/conversion/storage units. Several real systems can be modeled as an energy hub, from power plants to buildings and districts BIB001 .