Multi-energy systems (MES) can often deliver the same coincident power output by different combinations of power inputs. Therefore, they are characterized by an inherent flexibility. This work focuses a special class of MES which comprise large compounds of conversion units, and their exact off-design characteristics (i.e., potentially non-continuous, non-linear and non-convex individual feasible regions). A methodology based on computational geometry is then suggested and applied to assess the available feasible operation region (or space) of the compound system. A brief case study of different thermo-electric MES focuses on general technical limitations in power output on the one hand, and limitations in the special case of contingencies on the other hand. Results show that integrated energy systems show a significant flexibility in power output vector regulation if their individual off-design characteristics are considered properly.

The integration of efficient supply technologies like electric heat pumps and combined-heat-and-power (CHP) plants into multi-energy-systems is of growing interest. However, typical off-the-shelf systems like CHP units and industrial heat pumps are characterized as single-degree-of-freedom systems, which means the interaction between electric and thermal power input/output is well-defined and cannot be altered. In this work, the technically feasible working points of individual plants are translated into a mathematical set representation, which can then be visualized in Portfolio Flexibility Plots (PFP). The proposed PFPs reveal a new degree-of-freedom of partially uncoupled thermal and electric supply. This flexibility can be exploited to derive efficient supply portfolios under consideration of exact technical constraints and arbitrary time-varying supply tasks.

Energy conversion and distribution of heat and electricity is characterized by long planning horizons, investment periods and depreciation times, and it is thus difficult to plan and tell the technology that optimally fits for decades. Uncertainties include future energy prices, applicable subsidies, regulation, and even the evolution of market designs. To achieve higher adaptability to arbitrary transition paths, a technical concept based on integrated energy systems is envisioned and described. The problem of intermediate steps of evolution is tackled by introducing a novel paradigm in urban infrastructure design. It builds on standardization, modularization and economies of scale for underlying conversion units. Building on conceptual arguments for such a platform, it is then argued how actors like (among others) municipalities and district heating system operators can use this as a practical starting point for a manageable and smooth transition towards more environmental friendly supply technologies, and to commit to their own pace of transition (bearable investment/risk). Merits are not only supported by technical arguments but also by strategical and societal prospects like technology neutrality and availability of real options.

In this paper, MPC problem formulations for demand response of a power-to-heat residential microgrid are investigated. Two demand response operation strategies using MPC are proposed and thoroughly evaluated. The simulation results indicate that the problem formulation always poses a trade-off between comfort of the inhabitants, peak power reduction at point of common coupling and CPU time for the optimizer. These aspects have to be taken into consideration for a roll-out of demand response technology for residential buildings. While for the case presented in this paper, a quadratic objective function is the most promising one, the necessity of further investigations is derived from the results.