Overview

Background

FLEX was originally developed as part of the EU H2020 project newTRENDs, a collaboration between Fraunhofer ISI and TU Wien (Energy Economics Group). The goal was to model how households behave, how their energy systems operate, and how groups of households can interact within an energy community.

This repository is a fork of the original FLEX project, maintained by the Climate-Neutral Buildings group at Fraunhofer ISI for continued research and method development.

What FLEX Models

FLEX addresses three levels of analysis, implemented as three sequentially coupled modules:

FLEX-Behavior

Models the demand side: what do household members do throughout the day, and how does that translate into energy demand?

The key research question is: how does occupant behavior — activity patterns, appliance use, hot water consumption, occupancy — vary across different household types, and how does this affect the load profiles that downstream energy models need as input? Rather than using static load profiles, FLEX-Behavior generates stochastic, behavior-derived demand profiles.

FLEX-Operation

Models the supply and dispatch side: given a household’s technology stack (heat pump, PV, battery, EV, etc.) and the demand from FLEX-Behavior, what is the optimal or reference operation of the energy system?

The key distinction here is between two operating modes:

  • Reference mode — no smart control, devices operate by simple rules (heat when needed, charge EV when at home).

  • Optimization mode — a Smart Energy Management System (SEMS) minimizes the household’s electricity cost by optimally scheduling flexible devices.

This makes FLEX-Operation a direct tool for quantifying the value of demand flexibility and SEMS at the household level.

FLEX-Community

Models the community level: given a group of households’ operation results, how can an energy community aggregator generate profit?

Two mechanisms are analyzed:

  • Peer-to-peer (P2P) trading — surplus PV generation from one household is consumed by a neighbor rather than being fed to the grid, with the aggregator facilitating and profiting from the spread.

  • Aggregator battery optimization — the aggregator operates a community battery (or controls household batteries) to buy electricity cheaply and sell at higher prices.

License

MIT License — see LICENSE in the repository root.

Citation

If you use FLEX in research, please cite:

Yu, S.; Mascherbauer, P.; Haupt, T.; Skrona, K.; Rickmann, H.; Kochański, M.; Kranzl, L. (2025). Modeling households’ behavior, energy system operation, and interaction in the energy community. Energy, p. 136338. doi: 10.1016/j.energy.2025.136338