Joint project "Sustainable decentralised power generation"

Decentralised multi-energy-hub systems (MES) are a promising solution for coping with the challenges of implementing the Energy Strategy 2050, such as integrating decentralised energy production while handling the daily and seasonal variability of load and renewables. However, the optimal design and control of these systems is complicated by the interaction of several aspects, such as (i) modelling of time-dependent building demand (present and future) and renewable potential, (ii) simulation of technology performance and prediction of techno-economic evolution, (iii) short- and long-term dynamics of storage technologies, (iv) uncertainty of the input data in the short and long term, and (v) policy framework and social acceptance.

The aim of the IMES project was to develop a general and integrated methodology able to take into account several considerations ranging from the minimisation of the economic and environmental impact of MES at the design and control phase to the evaluation of the most critical techno-economic factors and societal barriers. Moreover, the project aimed at formulating guidelines for the development and deployment of MES, integrating renewable energy sources, natural gas micro-cogeneration (mCHP), hydrogen-based technologies and short- and long-term storage devices.

The developed integrated methodology was applied to optimally design and control the MES of two Swiss case studies, namely the rural village of Zernez (GR) and the urban neighbourhood of Altstetten (ZH). For each case study the optimal portfolio of technologies, as well as the optimal control strategies, for satisfying electricity and heat demands while minimising the total annual costs and CO2 emissions of the energy systems was determined. Furthermore, the project team evaluated the impact of renewable availability and changes in energy demand on the feasibility of achieving the goals of the Energy Strategy 2050 for different possible techno-economic MES scenarios from today to 2050.

Findings show that different neighbourhoods require different MES. Specifically, renewables availability and energy demand are the main drivers in defining optimal design and control strategies. In fact, both building retrofit and renewables integration should be pursued to meet the goals of the Energy Strategy 2050. High renewables availability is also the major driver for installing long-term storage devices. Moreover, the team has found that current technology approximations implemented in the analysis of MES lead to unrealistic and possibly unfeasible solutions. Therefore, they have implemented more accurate models to describe the behaviour of mCHP and power-to-gas (P2G) technologies. This has allowed identification of the thermal-to-electrical efficiency ratio and the conversion dynamics as the most relevant technical parameters for the development and deployment of fuel cell co-generation technologies. Furthermore, the results show the importance of considering robust and distributed control approaches, as well as network constraints, to meet customer satisfaction while considering customer privacy. Finally, the social assessment showed a positive attitude towards MES, though it identified barriers such as ownership, models and financing mechanisms.

Implications for research

The developed methodology improves the state-of-the-art techniques for designing, controlling and assessing MES by: (i) improving current techniques for describing the performance of mCHP units and P2G technologies within MES; (ii) identifying the most relevant techno-economic parameters for the development and deployment of fuel cell cogeneration devices; (iii) developing time-series aggregation methods to integrate seasonal storage devices within MES at low computational complexity; (iv) developing novel control strategies able to operate MES while accounting for data uncertainty and customer privacy; and (v) assessing the economic and environmental potentials of self-sufficient solutions and comparing them against grid-connected options. All such improvements address current research issues and provide the basis for novel research possibilities in the corresponding fields.

Implications for practice

To translate the research activity into practice, the developed methodology is applied to design MES that supply electrical and thermal energy to Zernez (GR) and Altstetten (ZH). To this end, a discussion with stakeholders (e.g. Elektrizitätswerk der Stadt Zürich (ewz), Energie 360°, Energia Engiadina) was carried out to collect and validate input data and assumptions, as well as to address the barriers that prevent the implementation of MES in today’s practice. Moreover, a survey and a group discussion have been carried out to assess people’s perceptions about MES.

The methodology developed within IMES can in principle be applied to any case study, pro-vided that the required input data are available. Discussions are already ongoing to apply the methodology to the energy grid installed at the ETH Zurich Hönggerberg campus.

Integration of sustainable multi-energy-hub systems at neighbourhood scale (IMES)

The joint project consists of five research projects

Integration of sustainable Multi-Energy-hub Systems from the Building Performance perspective (IMES-BP)

• Dr. Kristina Orehounig, EMPA Dübendorf; Prof. Jan Carmeliet, Herr Viktor Dorer, Dr. Ralph Evins, Prof. Matthias Sulzer

Technical evaluation of multi-energy-hub systems integration at neighbourhood scale (IMES-TEC)

• Prof. Marco Mazzotti, Institut für Verfahrenstechnik, ETH Zürich; Dr. Ndaona Chokani, Prof. Reza Abhari

Economic assessment of multi-energy-hub systems integration at neighbourhood scale (IMES-ECO)

• Prof. Volker Hoffmann, Departement Management, Technologie und Ökonomie, ETH Zürich

Integration of sustainable multi-energy-hub systems from the system control perspective (IMES-SC)

• Dr. Turhan Hilmi Demiray, Forschungsstelle Energienetze, ETH Zürich; Prof. Roy Smith

Integration of sustainable multi-energy-hub systems from a societal perspective (IMES-SE)

• Dr. Pius Krütli, Transdisciplinarity Lab - USYS TdLab, Departement Umweltsystemwissenschaften, ETH Zürich