*4.2. Reflection on Research Questions*

The first research question referred to the common use-cases of energy communities, which are described in Section 3.1. While a majority of ECs are renewable energy communities, there is an abundance of ways actors can cooperate on energy-related matters. There are also obvious synergies among use-cases for hybrid, or multi-purpose energy communities to be developed. Some ECs already diversify their services, such as acquiring storage after saving up from energy sales revenues [14,89,90]. On the one hand, this trend points to a potential for existing ECs to pilot new unique or hybrid use-cases, leapfrogging some of the initiation-exclusive progression factors and accelerating EC uptake. On the other hand, more research into the development, drivers and barriers of novel use-cases are needed. Especially when it comes to hybrid use-cases and multi-purpose ECs, both the progression factors influencing the projects and the impacts will be a result of multiple interacting core activities. It has been noted in previous reviews that such assessment is a research gap [2,6], and this study has found only one article discussing co-impacts [55].

The second research question referred to the various progression factors of ECs, collected and compiled in Section 3.3. A full classification of progression factors is presented in Appendix A. Due to limitations mentioned above, only one essential classification can be considered conclusive: by lifecycle phase. While the case studies and reviews identified four distinct phases (see Section 3.2), the analysis of progression factors revealed a clear distinction between operation and all other phases. This is reasonable, considering operation refers to the continuity of some form of status-quo, while initiation, design, early implementation, and various further developments are changes in the status quo. Most progression factors refer to initiation either exclusively or together with other phases. In reflection to the practical objective of supporting EC planners and policymakers, the EC progression factors by lifecycle phase are summarized on a project lifecycle wheel, reflecting the weight of each phase (Figure 22).

The third research question referred to the utility of UBEM tools in the various lifecycle phases of ECs, which is described in Section 3.4. It was shown that free, web-based hybrid or reduced order bottom-up models with over-hourly output resolution and heterogeneous output types and energy service modelling are most suitable for social upscaling; while bottom-up co-simulation model with an econometric model, sub-hourly output and diverse range of energy services modelling on district scale and the aforementioned tool are equally the best suited for initiation. There is only one existing tool for the former CityBES [116], and several for the latter HUES [117], UMEM [113], MESCOS [114]. In general, most UBEM capabilities deliver affordances for initiation and design stages, where most progression factors are. This also feeds into the main research question, whether UBEM is a technological trigger. The potential of UBEM, and UBEM-based simulation pipelines lie in the fact that they offer flexible decision-support in the earlier stages of projects, and whenever they are further developed. While decision-support for the operation of energy communities would require short term dynamic predictions on high resolutions to optimize the operation of energy communities, UBEM is a far more cost-efficient, early-stage alternative, requiring less input data and returning easy-to-understand outputs. To provide a quick tool for EC planners, the UBEM capabilities to look for based on progression factors, is summarized on a bipartite graph (Figure 23).

Reflecting on the second practical objective, recommending a development direction for UBEM, the trends in EC use-cases (see discussion above, based on section) make a good argument to invest in UBEM tool agility. The most impactful modelling capabilities were output resolution, output diversity, modularity and web deployment. Resolution on sub-hourly levels is necessary to forecast interactions on P2P energy markets, as trading usually occurs with 15-min frequency [27]. Output diversity and modularity becomes important with the diversification of energy community use-cases, and the growing prevalence of multi-purpose communities, such as green neighbourhoods. The value of UBEM tools is likely going to be determined by how many intertwined inputs and impacts do they handle, whom can be convinced with the evidence simulations provide. In other words, UBEM needs to respond well to in- and output diversification. This is why all affordances are met by USEM tools, whereas only two out of five are met by UBEM-only tools. Tools that either integrate UBEM with other models, such as City Energy Analyst [118], LakeSIM [119], CitySIM [120] and UrbanFootprint [109] with in-built transportation models, or tools that are modular and technically scalable, such as SEMANCO [111], UMEM [113], will be better suited to deliver diverse outputs reflecting EC use-case diversification. However, scalability to diverse, often uncertain and low-quality input data, which necessitates robust modules for data ingestion and pre-processing, is still something UBEM pipelines struggle with [121]. Finally, apart from architecture and functionalities, accessibility to users is also crucial, as seen by the performance of web-based tools versus desktop tools. While this was not explored as modelling tools are designed for engineers, user friendliness could be a pivotal improvement in the EC context. Given that laypeople gain formal powers and responsibilities in the EC model, tools in the future could support simple functionalities for users outside a niche of experts.

**Figure 22.** Energy community lifecycle wheel: distribution of progression factors by lifecycle phase.

Finally, reflecting on the research of energy communities, affordances have been a seamless addition to the conceptual frameworks of transition theory, multi-level perspective (MLP) and strategic niche management, as a missing link between the capabilities of enabling technologies, and the challenges posed by socio-technical transitions. We argue that technological affordances deserve an equal footing with institutional design and behaviour change, among factors that enrich any niche concept, be it a fundamentally technical, or a fundamentally social niche. Furthermore, the concept of MLP substantiates the influence of energy communities and UBEM tools on the user behaviour and preferences, which can gradually change the extraneous forces of the landscape, such as climate change. More articles need to be written on the role of technological affordances in fostering sustainable socio-technical transitions, with a special attention to disruptive technologies.

