*1.4. Theoretical Background*

The following two subsections justify the research gap by summarizing recent reviews in both EC and UBEM, showcasing a lack of intersections in previous studies. Subsequently, a new conceptual framework rooted in transition theory is defined in which the research gap will be filled.

Previous reviews concerning EC can be grouped according to their subject of focus: one group studies community energy in general, while others specialize in a specific type of energy community—characterised by their core activity. Schoor et al. [1] made a review of community energy research identifying that most studies come from developed countries and that there are different networks building up the discourse—however, these networks rarely interact. Brummer [2] collects definitions of community energy, its benefits provided for society and the barriers of EC projects. Berka et al. [12] and Roby et al. [33] investigate community energy impacts with different approaches. Nolden et al. [34] move on to business models, particularly in the UK, and how they evolved over time. Ceglia et al. [35] propose a standard for smart energy communities. Drivers and barriers feature in most previous studies, Lehtonen et al. [36] explore the role of trust more deeply. Moroni et al. [3] use a transition theory approach to classify energy communities, introducing the distinction between place-based and non-place-based communities.

Most of the specialized studies focus on renewable energy communities. Creamer et al. [6] have developed a conceptual framework and sets the focus of research on impacts, while others studied impacts [37,38] and monitored adoption [39]. Hess et al. [40] and Joshi et al. [41] made comparative reviews of multiple case studies, with the former focusing on country-level differences, and the latter exploring how justice is addressed. Bauwens [42] collects factors determining investment. Regarding institutional drivers, Heldeweg et al. [43] outlines and argues for a distinct legal form for renewable energy communities in a separate institutional context, while Petersen [44] analyses municipal energy plans as instruments.

Out of the remaining specialised studies, Gorroño-Albizu et al. compares community ownership models for renewable energy production and microgrid ownership [45]. Others [46–48] focus on community energy storage, its potential role, challenges, social, environmental, economic impacts, with an extended description of applied technologies. Warneryd et al. [49] explores institutional frameworks that drive microgrids, while two reviews [50,51] collects general microgrid drivers and challenges. Van Cutsem et al. [52] is a study on demand-response communities and the process of decentralization. Peer-to-peer electricity markets are the focus for Sousa et al. [53], classifying market designs, motivations and challenges. One review conceptualizes energy cooperation in industrial parks [54]. Finally, three reviews focus on broader "green neighbourhoods", community projects with more complex sustainability profiles, where energy is one component [32,55,56].

Review articles are considerably scarcer with technological factors of EC progression. While there is extensive literature on drivers, barriers and challenges of multiple EC types, and they are linked to institutional, social or economic interventions, this review will continue by investigating how technologies relate to these drivers, barriers and challenges.

In case of UBEM, numerous reviews have been done, however only outside the field of energy communities. In most cases the reviews differentiate the UBEM tools regarding their approaches. Swan and Ugursal [57] and many others [58,59] differentiated 2 mainly different building energy modelling methods: Top-down and Bottom up. Some of the reviews like [60,61] are focusing on classifying UBEM tools by this methodology. Li et al. [60] in their review classified the UBEM models in the aforementioned way, and emphasized the advances and still existing discrepancies in geospatial techniques. Abbasabadi et al. [61] described strengths and limitations by each method and extended their research further on urban scale energy simulation.

Sola et al. [22] expressed the need for a new hybrid tool for properly model energy use at urban scale incorporating other urban scale energy uses. [22] with the same approach reviewed not only UBEM tools, but holistic USEM tools They used a decomposition framework, where tools are decomposed into sub-models and their sub-models are reviewed as well. In addition, further explored how integrated and co-simulation platforms can work individually and together.

Allegrini et al. [23] reviewed 20 tools which can model neighbourhood level energy systems. In their review they created a comprehensive matrix where the capabilities of the twenty reviewed tools can be compared and screened easily. Reinhart et al. [24] reviewed models which are based on a bottom-up methodology. They provided a comprehensive review about the existing workflows and challenges in modelling in such a way due to the lack of data.

Ferrari et al. [62] reviewed 17 tools where these tools were classified based on their most useful features [62]. Their goal was to identify user friendly tools with hourly or sub-hourly outputs. Six of them were identified in the paper. Manfren et al. [26] assessed tools for distributed generation projects. They decomposed the distributed generation adoption into work phases and paired them with tools according to their inherent features. It is clearly visible that most reviews are presenting UBEM as a technological niche itself, hence this review will reposition UBEM and USEM tools as part of a socio-technological framework.

Given the divergence of previous studies, a discourse to conceptualize the research gap must be defined. While multiple research fields engage in the investigation of energy communities [1], this study is positioned in the field of transition management due to its core tenet being built upon the entanglement of social and technical practices [63]. At the heart of its conceptual framework is the socio-technical system, in which the multi-level perspective (MLP), helps to visualize how the energy communities as the social niche with the contribution of a technological novelty (as UBEM) can make a shift in the prevailing regime of the energy sector Figure 1.

**Figure 1.** Positioning research subject in the multi-level perspective—adapted figure of Geels [64].

The regime is the meso-level comprising of the dominant socio-technical system [65]. The regime defining the energy sector is influenced by the relation between social interests, like policies and regulations (from municipal, national, supranational levels), user preferences, which is characterized by a lack of choice awareness, energy dependency and the passive demand side in the energy system in a centralized, vertically integrated energy market [66]. MLP states that transitioning this regime towards decarbonisation is dependent on the novel technologies entangled with social change [63,67]. On the one hand, this is pushed from the micro-level, in niches, where technological innovations are sheltered from the selection of mainstream market [65] (Figure 2). On the other hand, the external factors are also essential in order to transform the regime, which in the context of MLP is the landscape (macro-level). The landscape can include extreme events, such as climate change, but it can also be less conspicuous events, like urbanization, or energy security concerns [65].

**Figure 2.** Positioning of research subject in niche development—adapted figure of Geels [65].

In this context, ECs are social innovations existing on niche level that need to progress from the protected environment into small market niche and eventually larger market niche. The strategic niche management (SNM) discourse explores the factors and process of niche progression [63,67]. A bottom-up initiative, like the energy communities as social niche can affect the regime, in this process the ECs become nodes in the decentralized energy sector, which can include the energy production, consumption as well as management. The members of community turn into prosumers from consumers [2]. This transition decreases their dependency on the vertically integrated energy market. Moreover, the change in regime can also occur as the involvement of users into the energy system, which raises awareness on the energy related issues, as well as on sustainability, thus increases their choice awareness. This, in combination with landscape pressures that provide a window of opportunity is the precursor for regime transition.

While the SNM emphasizes the dominant role of the niches in the replacement of regime, the transition does not depend on a single factor, rather different dynamics must reinforce each other on multiple dimensions. In that regard SNM usually focuses on the technological novelties as the dominant forces to make a shift in the current regime arguing for complementary social, institutional, behavioural change [63,67]. In other words, it focuses on technological niches, and how they can be enriched by a social perspective, but not the other way around. However, in case of ECs, it is the social novelty—with enabling technologies—that would eventually replace both the prevailing technology and social, political as well as cultural practices (the regime), ultimately feeding back to the landscape level [64,65].

By shifting the focus to a social innovation at the niche force driving change, and the technical innovation as the support, the conceptual framework of transition theory must be expanded to characterise this support. The theory of affordances is applied as an approach to link technological characteristics to the psychosocial, socioeconomic and governance factors describing EC drivers and barriers. Originally a concept describing complementarity between animals and their environment [68], affordance refers to the range of interactions possible between an environment and an agent operating within it [69]. In the field of design, the notion is used to sort the behaviour not only made possible, but also suggested by specific design features, in other words, the perceived affordances [70]. In this case, affordances are inherent in the object, technology, artefact, and more importantly, are influenced by design choices [71]. However, affordances are differentiated from capabilities or functionalities, as the same capability can have different affordances in different goal-oriented actions [72,73]. In the context of UBEM for example, the capability to predict energy demand affords evidence-basis for planning for consumers, but also affords risk elimination for a potential investor. Affordances that are intended by a product or technology, affordances that are suggested by its design features and actual observed behaviour are expected to deviate—the size of the gap is usually an indicator of good user-experience design. It is also important to note that by affording a set of interactions over others, features of technologies or environments do not only influence individual behaviour, but indirectly afford organizational models, routines, social practices in general, [74,75]. Thus, the notion of affordances fits the discourse of sociotechnical transitions well and is a useful method to articulate what exactly is in technology that breaks down a non-technical barrier, and how. This review offers a methodological contribution to transition theory by expanding its conceptual framework with affordances, which will allow investigations in the role of technology in accelerating social innovations, social niches.
