Conceptualizing Niche–Regime Dynamics of Energy Transitions from a Political Economic Perspective: Insights from Community-Led Urban Solar in Seoul

: The complex dynamics between technological niches and regime “lock-in” are critical in determining the pace and outcomes of energy transitions. The socio-technical transitions literature has received growing scholarly attention, but it lacks consideration of the broader political and economic contexts. This paper aims to advance understanding of socio-technical transitions by conceptualizing niche–regime dynamics from a political economic perspective, with reference to a case study of solar in Seoul. Based on in-depth face-to-face interviews with 18 key stakeholders, we have three ﬁndings. Firstly, the politico-economic contexts have created an embedded environment in which ﬁve factors have a clear inﬂuence on niche–regime dynamics. Secondly, the politico-economic contexts created conducive conditions for niche developments on the one hand, but, on the other hand, have created inhibitive conditions that have cancelled out the positive forces and reinforced “lock-in”. Thirdly, the processes occur at multi-scalar levels: Community solar niches in Seoul are conditioned by the broader politico-economic contexts at city and national levels. We conclude that su ﬃ cient policy attention should be given to the political economy of a national energy system in order to create conducive conditions for community-led niches to realize the full potential that they could o ﬀ er in energy transitions.


Introduction
Low-carbon and energy innovations have proliferated in national and sub-national levels all over the world. Among these initiatives, urban solar photovoltaic (PV) developments in cities such as Seoul, London, and New York City have experienced major progress as solar PV costs continue to decline and policy-makers seek cost-effective post-Fukushima energy strategies. The Solarize NYC program in New York City [1] and the 2022 Solarcity Plan in Seoul [2] are examples showing that solar has become a core element of cities' sustainability and energy plans.
These recent solar developments have increasingly shown that cities are key sites of transitions [3][4][5][6]. An extensive body of energy studies has already found that renewable energy (RE) has the potential to break the lock-in and achieve deep decarbonization targets required to avoid catastrophic climate impacts [7,8]. How and the extent to which these urban solar developments emerge, scale up, diffuse, and compete with traditional fossil fuel/nuclear energy options has, however, remained under-studied.
Transitions studies have grown rapidly in the last decade, shedding light on the complex interplay of socio-technological aspects of energy transitions. Transitions theorists argue that energy transitions can be delivered only if there is a co-evolution of technology, policy, infrastructure, scientific knowledge, nuclear risks [18]), political ideologies, societal values, macro-economic patterns, and institutions [10]. The MLP argues that as niches scale-up, diffuse, and accumulate, they can weaken, destabilize, shift, and eventually replace regimes. This niche development process can be conceptualized as a progression from technological niches to market niches and to regime shift [19].
Transitions studies explain and conceptualize the complex niche-regime interactions by introducing the terms "lock-in" and niche development processes. Studies on carbon and nuclear lock-in have attributed the causes of lock-in principally to the dynamics of collective action (societal norms, customs, consumption patterns, and formal regulations through coalition building and networking) and asymmetries of power [20].
In addition, niche building processes can weaken lock-in situations in the presence of particular drivers and contexts [19,21]. However, the linkages between niche processes and the broader contextual environment have remained under-studied. The understanding of complex linkages between carbon/nuclear lock-ins and niche development processes and of the relationships with the broader contextual environment is not well developed [19].

The Political Economic Perspective on the Niche-Regime Dynamics
Context has been increasingly recognized as an important factor shaping energy transitions. The political economic perspective is increasingly examined to provide a broader, contextualized view of energy socio-technical transitions [22][23][24][25]. This sub-theme of transitions studies examines embeddedness formed by the politico-economic factors of a transition site [16,26]. This political economic perspective of energy transitions is thus crucial to provide a better understanding of the conditions in which niches might move to regimes [26].
The political economy analysis of energy transitions gives special attention to national political and socio-economic relationships and positions of actors, where political elites and incumbent utilities in particular may be able to reinforce carbon/nuclear lock-ins [10]. This perspective of regime-niche dynamics tends to focus on the relatively democratic nature of state power, national infrastructure development, political institutions [16], energy access, national capacities for technological innovation, and levels of electricity market reform [16,25,[27][28][29]. However, this perspective lacks an understanding of complex interactions between national and sub-national levels, with a few exceptions [27].
There are three main gaps in the literature. Firstly, most political economy analysis focuses on the "lock-in" or path-dependent mechanisms favoring incumbent fossil/nuclear-based regimes [20,30], overlooking conducive conditions that may favor niche diffusion. Secondly, most analyses focus on the national level, and few capture the dynamics across national and sub-national levels. Some transitions scholars argue that "scales" are critical in understanding complex social processes, which have a certain scale size at a certain level, i.e., an operational scale [31]. Such a scalar perspective has the potential to provide a better understanding of the socio-political interactions of regime and niche actors in energy transitions beyond and below the national level. It is thus relevant to this study, as urban/community solar may well operate on an individual or a community scale, but fail to function well when scaling up to the regime level. The current literature has limited discussion in this important aspect. Thirdly, few studies develop a political economy analysis of energy transitions beyond North America and Europe (except, for example, [25,28]).

Towards an Integrated Framework
To fill these gaps, we expand the MLP with the political economic perspective by developing an integrated framework to conceptualize the complex and critical politico-economic dynamics in the niche-regime interactional processes ( Figure 1). Our framework has several features. Firstly, we specify five main types of critical factors shaped by the politico-economic contexts, influencing the progression from technological niches to market niches and, subsequently, regime shifts under the interactions between state and non-state actors at the landscape, regime, and niche levels. Encompassing the technical, economic and financial, political and institutional, as well as social and cultural dimensions [26,32], (1) Global trends, political and economic ideologies, and public preferences: Manifested at the landscape level, political economy of socio-technical transitions can be approached in the domains of "interests", "institutions", and "ideas" [33]. This study departs from and contextualizes these domains into global trends, political and economic ideologies, and public preferences. The worldview on climate change (global trends, [18]), the Green Growth Vision in South Korea (political and economic ideologies, [18]), and low tariffs, clean air, energy sources, and community energy (public preferences, [34,35]) are some examples; (2) Political power structure, policy traditions, and governance approaches: Referencing the "horizontal understanding of power" and highlighting the dynamics of actors' engagement with resources, structures, and systems through reinforcive, innovative, and transformative power [36,37], political power structure, policy traditions, and governance approaches are proposed in this study to understand such dynamics. Political power structure refers to, e.g., the relatively democratic nature of state power, political and industrial networks (in particular, the nature and intensity of government-industry linkages) [38][39][40], social networks between governments and civil society [12], and the role of political media (e.g., [29]); policy traditions include the "developmental state" in east Asia [41]; governance approaches refer to, e.g., authoritarian policy-making in China, technocratic policy-making in France [42,43], and participatory approaches in the UK [44], and key governance issues include public trust [12]; (3) Physical availability of energy resources, national capacities for technological innovation, and national (energy) infrastructure development: These elements constitute the core building blocks of socio-technical systems transitions [45]. Energy self-reliant rates and power grid networks are some instances [39,46,47]; (4) Electricity market reforms and market features: These features determine regime and niche actors' incentives/disincentives [48] and constitute the social groups from production and functional/user sides of socio-technical systems transitions [45]; and (5) Visioning and leadership, and national energy plans and policy frameworks: Visioning relates to visions of how energy transitions might unfold over time under the political processes, and the role that specific technologies could play in the process [49]; leadership refers to the ability of political and community leaders to articulate a vision and inspire people to act in order to achieve concrete results [50]; energy policy frameworks relate to clear policy objectives, policy frameworks, and specific policies such as RE feed-in tariff (REFIT) policies to guide technological searches [26,51]. Grounded by the theoretical articulation in "transitions management", the long-term perspective of transitions is embedded in "goals" and "visions" defined in the processes of visioning, leadership, national energy plans, and policy frameworks [52].
conditions to foster niche diffusion, but they can also create inhibitive conditions that impede niche diffusion. Our framework predicts that the existence of more conducive conditions would create stronger forces for change to counteract the forces against change. Thirdly, our framework adopts a multi-scalar approach with special attention to the community niches' conditions under the broader politico-economic contexts at city and national levels.

Methodology
Our research questions are: (1) What are the features of Seoul's urban solar developments as a niche innovation for Korean energy transitions? (2) To what extent does Seoul's approach to urban solar development weaken, replace, or transform energy regimes? (3) What are the explanatory factors of the observed phenomenon? In particular, how do the politico-economic contexts of South Korea create conducive and inhibitive conditions for the niche development of urban solar in Seoul?
This study is based on desktop studies and 18 in-depth, semi-structured, face-to-face interviews conducted between 2017 and 2019. The interviewees were carefully selected informants or key stakeholders who participated in climate and RE policy-making at the Seoul city and national levels, comprising energy experts, academics, NGOs, community leaders, government committee members, and government officials (Appendix A). To avoid "limitations of interpretivism"-the person-specific and private subjective account of data interpretation that cannot be viably verified or replicated by a third person [53]-we review Secondly, our framework argues that these regime-niche dynamics can create conducive conditions to foster niche diffusion, but they can also create inhibitive conditions that impede niche diffusion. Our framework predicts that the existence of more conducive conditions would create stronger forces for change to counteract the forces against change. Thirdly, our framework adopts a multi-scalar approach with special attention to the community niches' conditions under the broader politico-economic contexts at city and national levels.

Methodology
Our research questions are: (1) What are the features of Seoul's urban solar developments as a niche innovation for Korean energy transitions? (2) To what extent does Seoul's approach to urban solar development weaken, replace, or transform energy regimes? (3) What are the explanatory factors of the observed phenomenon? In particular, how do the politico-economic contexts of South Korea create conducive and inhibitive conditions for the niche development of urban solar in Seoul?
This study is based on desktop studies and 18 in-depth, semi-structured, face-to-face interviews conducted between 2017 and 2019. The interviewees were carefully selected informants or key stakeholders who participated in climate and RE policy-making at the Seoul city and national levels, comprising energy experts, academics, NGOs, community leaders, government committee members, and government officials (Appendix A). To avoid "limitations of interpretivism"-the person-specific and private subjective account of data interpretation that cannot be viably verified or replicated by a third person [53]-we review government archives, academic publications, reports, and news articles to triangulate the interview data and provide additional contextual information.

Case Contexts: Energy Challenges and Policy Responses in South Korea and Seoul
South Korea is heavily reliant on energy imports, with a low energy self-reliance rate of 5.3% [54]. The Korean electricity sector is fossil-and nuclear-based. Coal, natural gas, and nuclear contributed 42.0%, 21.6%, and 26.1% of the national electricity generation in 2017 (Table 1 and Figure 2b) [55]. With 24 nuclear reactors and a capacity of 22.5 GW in 2017, Korea ranked as the fifth largest nuclear-producing country in the world [56,57]. Hydroelectricity and RE (including solar, wind, biofuel, and other RE) contributed the remainder [55]. South Korea's electricity consumption increased rapidly since the 1990s, with its peak annual growth rate reaching 10% in 2010 before slowing down. Electricity consumption doubled from 239,535 GWh in 2000 to 507,746 GWh in 2017, followed by an increase in CO 2 emissions from 431.9 MtCO 2 in 2000 to 589.17 MtCO 2 in 2016 ( Figure 2d).
Seoul, the capital, is home to 21.9% of the national population and accounts for 9.1% of national annual electricity consumption (Data compiled from [54]), yet its electricity self-sufficiency rate was only 3.0% [58]. While Seoul's electricity generation mainly came from fossil fuels, Seoul's electricity consumption was mainly met by electricity transmitted from coastal nuclear power plants. The rising electricity demand has heightened the capital's electricity dependence issue; Seoul's electricity consumption rose from 41,824 GWh in 2006 to 46,493 GWh in 2016 [56]. These energy challenges have prompted the national and city governments to formulate energy plans and policies for sustainable energy transitions. Korean and Seoul energy policies have experienced major changes after the Fukushima nuclear accident ( Table 2). Nuclear energy was formerly a national strategic priority, but the incumbent president Moon Jae-in aimed to phase out nuclear by 2082 [61,62]. Since 2017, the Korean government has introduced energy-saving initiatives while increasing non-hydro RE installed capacity from about 7.6% in 2017 to 20% by 2030. The national Eighth Basic Energy Plan announced in 2017 set RE targets at 58.5 GW in 2030 from 11.3 GW in 2017.
Under the national energy policy framework, the Seoul government has introduced policies to reduce the reliance on nuclear, use more RE, and improve energy efficiency. The One Less Nuclear Power Plant Policy (OLNPPP) introduced in 2011 was the most notable mayoral energy policy, and was aimed to reduce the city's energy demand by the annual generation capacity of one nuclear power plant (1 GW) by 2014 [63,64].
installed capacity from about 7.6% in 2017 to 20% by 2030. The national Eighth Basic Energy Plan announced in 2017 set RE targets at 58.5 GW in 2030 from 11.3 GW in 2017.
Under the national energy policy framework, the Seoul government has introduced policies to reduce the reliance on nuclear, use more RE, and improve energy efficiency. The One Less Nuclear Power Plant Policy (OLNPPP) introduced in 2011 was the most notable mayoral energy policy, and was aimed to reduce the city's energy demand by the annual generation capacity of one nuclear power plant (1 GW) by 2014 [63,64].

Solar Has Been Supported as a Viable Energy Option in Both the National and Seoul Post-Fukushima Energy Strategies
Solar, alongside energy-saving, has become a public preference as a viable energy alternative in post-Fukushima South Korea, and in Seoul in particular. Several observations of this solar-oriented post-Fukushima energy strategies are important to note:  (Table 2). (4) Solar energy is considered the most promising RE source mainly due to its suitability across the country [59]. South Korea is generally exposed to relatively high solar radiation, especially in the southern part of the Korea Peninsula. Seoul has a significant solar resource, with a monthly average daily solar radiation of 4.65 kWh/m 2 compared to the national average of 4.01 kWh/m 2 [59]. Approximately 30% of the 187 million m 2 rooftops at a five-degree tilt in Seoul are also found suitable for solar deployment [77].
1% of the city's 3.6 million households in 2017 [76], providing just 0.23% of Seoul's electricity needs in 2017 despite Seoul's ambitious solar target of 1 GW by 2022 (Table 2). (4) Solar energy is considered the most promising RE source mainly due to its suitability across the country [59]. South Korea is generally exposed to relatively high solar radiation, especially in the southern part of the Korea Peninsula. Seoul has a significant solar resource, with a monthly average daily solar radiation of 4.65 kWh/m 2 compared to the national average of 4.01 kWh/m 2 [59]. Approximately 30% of the 187 million m 2 rooftops at a fivedegree tilt in Seoul are also found suitable for solar deployment [77].

Seoul's Model of Niche Innovation: Government-Empowered Community-Led Solar Developments
Urban solar developments have proliferated across Western and Asian countries, but progressed along different pathways. Seoul's niche innovation with a government-empowered community-led approach for urban solar has two distinctive characteristics.
Firstly, Seoul's model is community-based and citizen-driven, underpinned by the preexisting community grassroots environmental movement across Seoul (Interviewee 7b; [50]). In contrast to countries (e.g., the U.S. and China) where solar PV deployment is dominated by the utilities, a relatively high level of household participation is evident in Seoul's solar

Seoul's Model of Niche Innovation: Government-Empowered Community-Led Solar Developments
Urban solar developments have proliferated across Western and Asian countries, but progressed along different pathways. Seoul's niche innovation with a government-empowered community-led approach for urban solar has two distinctive characteristics.
Firstly, Seoul's model is community-based and citizen-driven, underpinned by the pre-existing community grassroots environmental movement across Seoul (Interviewee 7b; [50]). In contrast to countries (e.g., the U.S. and China) where solar PV deployment is dominated by the utilities, a relatively high level of household participation is evident in Seoul's solar developments. Of the 105.01 MW of solar PV installed between 2003 and 2015 in Seoul, private buildings (mainly residential) and micro-PV (also mostly in residential) constituted 31.74 and 17.74 MW, whereas public buildings and schools had 43.04 and 12.49 MW of solar installed, respectively [78].
Secondly, Seoul's model is empowered by the Seoul government through a series of mayoral policies. The most notable policy is the Energy Self-reliant Village Program introduced under the OLNPPP in 2012 [64]. The OLNPPP has adopted a citizen-centric approach and has a slogan of "Citizens are Energy". Driven by the core values of energy sharing and public participation, Mayor Park Won-soon introduced this program with the aims of enhancing citizens' energy awareness and promoting energy-saving and solar PV installations. By mid-2018, a network of some 100 energy self-reliant communities across Seoul have been established (Interviewees 7b and 18).
This citizen-centric approach partly explains why Seoul has emphasized the development of energy self-reliant villages (Interviewee 4) and mini solar panels as a means of enhancing wide citizen participation in energy transitions (Interviewees 16 and 18). In addition to rooftop solar, mini solar panels, characterized by their small size (usually 1 × 2 m) and capacity (below 1 kW), have also been introduced to the balconies of apartment-type buildings. Community solar in these energy self-reliant villages can be categorized into two main types: Solar in old urban neighborhoods and solar in residential apartment buildings. As a representative of the first type, Sungdaegol began a community energy movement after the Fukushima accident. Apart from energy-saving initiatives to reduce nuclear reliance, Sungdaegol extended the movement to solar PV installation alongside the OLNPPP. Seoul's citizen-centric approach helped Sungdaegol in establishing its focal Energy Supermarket, in networking academics, solar installers, financial institution, and volunteers to overcome technical, financial, and educational issues from solar installation (Figure 4), and in installing solar PV in some 50 buildings; Sungdaegol's leader participated in the OLNPPP Implementation Committee and the Citizens' Committee of the Seoul Energy Corporation (Interviewee 7b; [50,79]).
citizen-centric approach helped Sungdaegol in establishing its focal Energy Supermarket, in networking academics, solar installers, financial institution, and volunteers to overcome technical, financial, and educational issues from solar installation (Figure 4), and in installing solar PV in some 50 buildings; Sungdaegol's leader participated in the OLNPPP Implementation Committee and the Citizens' Committee of the Seoul Energy Corporation (Interviewee 7b; [50,79]). Shindaebang Hyundai Apartment is a typical apartment-type energy self-reliant village. The resident representatives of the apartment initiated energy-saving campaigns to promote energy-efficient devices and energy-saving habits among residents. Similarly to Sungdaegol, the campaigns extended to promoting mini PVs, and rooftop solar on residential blocks and an apartment kindergarten ( Figure 5). Resident representatives were also invited to sit in Seoul Government's energy committees and participate in energy policy-making (Interviewees 5 and 6). Shindaebang Hyundai Apartment is a typical apartment-type energy self-reliant village. The resident representatives of the apartment initiated energy-saving campaigns to promote energy-efficient devices and energy-saving habits among residents. Similarly to Sungdaegol, the campaigns extended to promoting mini PVs, and rooftop solar on residential blocks and an apartment kindergarten ( Figure 5). Resident representatives were also invited to sit in Seoul Government's energy committees and participate in energy policy-making (Interviewees 5 and 6).

An Evaluation of the Niche Formation Process of Urban Solar in Seoul: Solar Niches Are Emerging, but the Magnitude of Energy Socio-Technical Regime Shift Has Been Limited
To what extent, then, is Seoul's model for urban energy transitions effective? By applying Schot and Geels [19]'s conceptualization of niche development processes, we found that Seoul's solar technological niches have emerged and shown early signs of development into market niches. However, these niches had only limited impacts on regime shifts. Major outcomes of the niche development processes are illustrated in Table 3.
Technological niches of solar communities have evidently emerged in Seoul. Sungdaegol, for example, has provided protected spaces that allowed solar applications to be tested in local customer environments. The Energy Supermarket, a co-operative shop, has become a meeting place, a platform where group works were organized, and a local store for solar DIY tools (Interviewees 7b and 9; [50]). Flat cables were introduced by a local solar installer to address

An Evaluation of the Niche Formation Process of Urban Solar in Seoul: Solar Niches Are Emerging, but the Magnitude of Energy Socio-Technical Regime Shift Has Been Limited
To what extent, then, is Seoul's model for urban energy transitions effective? By applying Schot and Geels [19]'s conceptualization of niche development processes, we found that Seoul's solar technological niches have emerged and shown early signs of development into market niches. However, these niches had only limited impacts on regime shifts. Major outcomes of the niche development processes are illustrated in Table 3.
Technological niches of solar communities have evidently emerged in Seoul. Sungdaegol, for example, has provided protected spaces that allowed solar applications to be tested in local customer environments. The Energy Supermarket, a co-operative shop, has become a meeting place, a platform where group works were organized, and a local store for solar DIY tools (Interviewees 7b and 9; [50]). Flat cables were introduced by a local solar installer to address tenants' need of mini PV cable connections without drilling holes into walls.
Early signs of the developments of market niches are also evident from Sungdaegol's technological niches. The recent diffusion of solar rooftops in the local wet market-a defining feature of market niches-demonstrated that market niches supported by user demands existed [19,21]. As a Sungdaegol leader notes, "At first, only a few stores in the local market installed solar panels. However, as that number grew to 20 and 30, we had a power of scale. Then, those stall owners who didn't have solar panels installed feared of being isolated. They thought they might lose something by not being part of this new local social trend. In a sense, we made them feel like outsiders. So, without having to do any further persuasion, more and more merchants decided to install solar panels . . . I think about 50% of merchants have installed solar panels right now, and I hope the number will further increase".
(Interviewee 10) Additionally, in 2018, Sungdaegol started to develop an energy trading scheme among local residents, providing support for emerging market niches (Interviewee 7a).
Our case study, however, revealed that the niche development processes have very limited impact on regime shifts with major limitations in the following important aspects: i.
Fossil fuel/nuclear "lock-in" prevails in Seoul's electricity sector. Solar is still a minor energy source in Seoul, representing merely 0.23% of Seoul's electricity consumption in 2017. Solar households represented a tiny segment of Seoul. As of June 2017, 34,000 households were equipped with solar panels, equivalent to less than 1% of 3.6 million households [76]. ii.
There is limited co-evolution of regulatory structures. KEPCO, the state-owned monopolistic utility that owns 92% of the nation's total electricity generation capacity, has remained as a key regime actor for centralized fossil fuels and nuclear generation (Interviewees 4, 7b, 15, [28]). iii.
There is limited co-evolution of user practices. Although some residents in Seoul were attracted by the financial benefits of solar PV and its low up-front cost (as low as 70,000 KRW (approximately 63 USD) as of January 2019), they might be unwilling to pay for the replacement costs of inverters (170,000 KRW (approximately 152 USD)). Some householders in Sungdaegol have already idled or resold their solar systems in the second-hand markets to avoid paying the replacement costs though the systems were used for only several years. Despite the fact that the official figure of such cases is not available to the authors, at least some early solar adopters had an evidently low level of awareness of the need for system maintenance and low attachment to their solar systems (Interviewee 7b).

The Conducive Conditions for Niche Formation: From a Political Economic Perspective
By applying our framework into the case of Seoul, we found that the politico-economic contexts of South Korea have conducive conditions for various niche-formation processes. The contexts have, however, also become the root of some inhibitive conditions impeding solar niche diffusion. The linkages and interactions between contexts, conducive and inhibitive conditions, and the outcomes in terms of the niche-regime dynamics are summarized in Table 3. Four key conducive conditions are discussed as follows.

Public Preferences for RE Introduced a Major Change in the Landscape
Historically, Koreans supported the fossil-and nuclear-based energy systems mainly because they provided low tariffs and a reliable supply. However, after the Fukushima accident in 2011, because of public concerns over severe fine dust pollution, nuclear risks, and the associated public health issues, the public began to look beyond just the economic issues (Interviewees 7b, 14,15).
It is in the post-Fukushima context that RE as a viable energy alternative has become much more widely supported by the public in South Korea (Interviewees 7b, 14,15). In addition, the aspiration of community energy self-reliance has grown in South Korea and in Seoul in particular, and this explains the wider support for RE and decentralized energy systems (Interviewee 15).

The Alignment of the National Green Growth Strategy and the Development Plans of Hi-Tech RE Clusters
The alignment of the Korean government's macro-economic policy-the Green Growth Strategy [12] and its industrial policies-to support hi-tech energy industries has created a reinforcing effect fostering solar development. While the solar manufacturing industries are not located in Seoul, RE clusters have been set up in a number of regions across South Korea. These regions include Chungcheongnam-do and Chungcheongbuk-do (Cheongju-Cheonan-Sejong), Jeollanam-do (Gwangju), Jeoallabuk-do (Jeonju), Busan and Gyeongsangnam-do, Gyeongsangbuk-do (Daegu-Ulsan), and Jeju [80].
The national technological innovation capacity in PV has been gradually built up in recent years, closing the gap between advanced countries [80]. Currently, PV and wind power accounts for 34% of the new and RE industry's deployment, 74% of investment, 80% of sales, and 97% of exports [80]. Enhancing competitiveness in the global solar market has become a national strategy. A major initiative is the plan to establish the Chungbuk Innovation City as an outpost to promote the nation's PV industry [80].

Political Openness Enables a Bottom-Up Citizen-Centric Approach to Urban Solar in Seoul
The conventional top-down approach in energy strategies has been seen as a root problem causing central-local policy incoherence and the low level of community involvement in South Korea [81]. This was until 2008; when the Lee Myung-bak Administration set up the Prime-Ministerial Green Growth Committee, the Korean policy-making systems started opening up [12]. In more recent years, the Moon Jae-in Administration, which assumed office in May 2017, has provided increasing opportunities for NGOs to be invited to offer inputs to energy policy-making (Interviewee 16).
In Seoul, although the national RE policy framework regulates and influences solar energy developments, the mayor of Seoul, Park Won-soon, has shown his leadership in opening up policy-making and governance systems. The formulation process of the OLNPPP was distinguished by its inclusive approach-many local stakeholders, including local community leaders and NGOs, were invited to offer policy inputs through rounds of consultations and various committee groups. This inclusive approach was found to be effective in gaining substantial local support, and, thus, implementation capacity, to deliver the Energy Self-reliant Village Program (Interviewee 16).
Political leadership of Mayor Park also played an important role in the solar niche diffusion process by introducing the OLNPPP. Different from traditional preoccupations with economic and carbon-reduction benefits, Park emphasized and prioritized social concerns in Seoul's energy policy-making. He brought Seoul citizens' attention to the inequity issue of transmitting nuclear electricity through rural parts of South Korea. In this sense, Park's political leadership and his OLNPPP created spaces for RE to gain public support. In addition, even though the national government abandoned the national REFIT policy in 2012, Mayor Park decided to introduce his Seoul-type REFIT policy in 2013. The REFIT and direct subsidies provided strong economic incentives for solar installation in Seoul (Interviewees 1, 4, 7a).

Vertical and Horizontal Networks
Alongside the energy community network formed by some 100 energy self-efficient villages across South Korea, Mayor Park appointed the Sungdaegol solar community leader, Kim Soyoung, a co-chair of the energy self-reliant villages network, to two important policy committees for the Seoul government. This government-empowered network has allowed Kim to act as a spanning actor for bridging the social and political networks and between community and city levels. Additionally, the community-grown network has, though less directly, extended further upwards to the national level-through the Joint Declaration of Regional Energy Conversion signed between Seoul and three other provinces [82]-as well as to the global level-through the C40 network of global city mayors [83].

The "Developmental State" as the Dominant Economic Ideology Has Reinforced a Technological Lock-In Towards Nuclear
South Korea's economy has been characterized by its "developmental state" model, which continues to impact the economy and reinforce the lock-ins towards fossil fuels and nuclear energy. Introduced by Chalmers Johnson in the 1980s, the concept of the developmental state refers to a state that prioritizes and directs economic growth, productivity, and technological competitiveness with state intervention under an elite economic bureaucracy [84][85][86][87]. Striving for economic development after the Korean War, South Korea has been widely regarded as a developmental state in the literature [41,87,88].
Korea's "developmental state" model favored scientifically and technologically driven economic growth. Nuclear was first pursued as a tool of national development and economic growth under President Park Chung-hee's administration in the 1960s and 1970s [41,88]. Unlike the US nuclear position of being a "responsible regulator" imposing effective containment, South Korea cultivated a national imagination of nuclear as the "atom of development" through a logic of self-reliance [89]. With this ideology and nuclear being viewed as an irreplaceable, affordable, and essential energy source [90], nuclear has gradually been embedded into the Korean political economy as an integrated part of economic development with support from subsequent conservative governments. In recent years, responding to the post-Fukushima power outages in mid-September 2011, the Korean government proposed expanding generation capacity with new coal and nuclear power plants [91]. The political support for nuclear has been reduced since 2017, when the incumbent Moon's administration introduced a nuclear phase-out policy to close all of the nuclear reactors when their lifetimes are over [62].
This developmental state ideology has also cultivated a pro-nuclear approach under a national imagination of wealth creation through developments in science and technology (i.e., technological developmentalism) [41]. Vested interests in nuclear were thus developed among conservatives and nuclear power interests [28,88,92]. The "nuclear village", a term used to describe networks of institutions, utilities, contractors, academics, and scientists favoring nuclear technologies in Japan and other places [93], also exists in South Korea. KEPCO, the political media, conservationists, and other nuclear stakeholders resisted the Moon Administration's nuclear phase-out policy. They argued that phasing out nuclear would lead to tariff increases, dampen the nuclear industry, and damage nuclear technology exports (Interviewees 7b, 15, 16, and 17). KEPCO, through its subsidiary, the Korea Hydro and Nuclear Power (KHNP), owned 22.53 GW of nuclear capacity and announced plans for entering the global nuclear market. KEPCO thus has a vested interest in resisting RE [41].
The OLNPPP, on the other hand, can be seen as a policy response of the Seoul government to counteract the nuclear lock-in. Since the Seoul government and citizens could not directly influence the national nuclear decision and, yet, nuclear constituted the main electricity source for Seoul, the Mayor, inspired by the post-Fukushima citizens' energy-saving initiatives, launched the energy campaign and drew a linkage from Seoul's energy-saving to having "one less nuclear power plant". The mayoral policies could be attributed to the national nuclear situation and the existing nuclear vested interests.

Incomplete Electricity Market Reforms and Regulatory Incompetence
Electricity market reforms in South Korea officially started in 2001 with the aim of improving efficiency and privatizing the state-owned vertically integrated monopoly KEPCO [18,94]. The reforms were, however, halted in 2004 due to political resistance [18,94]. A recent attempt to break the stalemate was made in August 2016 by the Park Geun-hye Administration, which announced it would continue the reforms [95]. However, to date, only the generation sector is open to market competition, while the transmission, distribution, and retail sectors have all remained monopolized. These partial electricity market reforms have created barriers to solar niche developments in Seoul in at least two important ways.
The first barrier relates to the disincentives of KEPCO to change. KEPCO has remained a state-owned monopoly controlling the transmission, distribution, and retail systems. As a dominating incumbent, KEPCO faces limited forces for change from its customers, who have literally no choice of their electricity suppliers (Interviewees 7b, 15, and 17). Although there is an emerging force for change from the commercial end-users for RE, the force is too weak to force KEPCO to change. Several Korean conglomerates, such as SK hynix and Naver, have set 100% RE targets for their datacenters, with Samsung recently making a similar commitment [96]. A solar community leader notes that solar niches would be able to cause regime shifts only when these bottom-up forces for change from end-users become strong enough. That leader notes that: "When this kind of change takes place with more companies and in more places, KEPCO will have no choice but to respond." (Interviewee 7b, a community leader of the Sungdaegol solar community) The second barrier relates to regulatory incompetence in dealing with increasingly market-based energy systems. While market competition has already been introduced to the generation sector, KEPCO's subsidiaries still dominate the sector with about 69% of the total capacity of South Korea, though the number of non-KEPCO-affiliated power producers recorded exponential growth to more than 3500 by December 2019 [97]. Some niche actors and academics thought that complete market reforms were essential to open up transmission and distribution segments under such a context. The reforms would create a conducive market environment for new RE suppliers and business models to develop. In Sungdaegol, for example, some local residents were keen to set up a solar energy trading system through which they can act as middle-men. There exist market niches, but there is, however, a lack of regulatory clarity for regulating new business models of a similar nature, nor are there sufficient regulations for local initiators in supplying electricity (Interviewee 7b). Regulatory clarity and competence need to be improved to develop effective rules to regulate energy trading of various forms, such as trading between people, between buildings, and between buildings and people (Interviewee 15).
The third barrier relates to the incompetence in regulating electricity prices. Tariff reforms are essential in order to create a more favorable market environment for RE to make a business case (Interviewees 14, 15, and 17). Electricity prices have been modulated at low levels by the Korean government. Koreans are, therefore, generally accustomed to low electricity prices and would oppose tariff increases (Interviewee 17).

Swinging between Excessive Government Intervention and Inadequate State Action in Governing Solar Niche Developments
Governments have an important role to play in creating favorable price signals and market conditions for niches development [51]. In Seoul, direct subsidies have effectively scaled up solar deployment by cutting upfront costs. This policy has, however, revealed two major limitations. Firstly, the government has relied too much on direct subsidies to increase new solar installations. Direct subsidies to solar have been raised several times in recent years to incentivize potential solar householders. In 2018, a mini-sized PV purchaser had to pay only 60,000 KRW (54 USD) of the full price of 570,000 KRW (510 USD) in contrast to paying 350,000 KRW (315 USD) a few years ago (Interviewee 7b). It has become a concern that the government subsidies have become excessive in ways that have made people accustomed to subsidies. In Sungdaegol, there are reported cases where PV householders were reluctant to pay 170,000 KRW (152 USD) to replace old inverters, as the costs cannot be covered by the subsidies, and their entire solar systems were left unused or even demolished (Interviewee 7b).
Additionally, the subsidies are perceived as excessive, as they have undermined market formation in the solar industry. Credit unions that provide solar loans exist in Seoul as new niche market actors. These locally grown financial institutions have, however, met with limited market demand, as solar householders have good access to heavy subsidies and most of them do not need to apply for solar loans (Interviewees 7b and 11). There are also concerns that public spending could have been allocated to long-term research and development investments in improving efficiency of solar panels rather than focusing on subsidies (Interviewee 11).
In short, there are multiple reasons for the reliance of favorable and perceived excessive subsidies to promote solar at the community level in Seoul. Some of these reasons include: (1) The policy target of the OLNPPP has focused on increasing decentralized solar installed capacity rather than centralized solar electricity generation in order to promote niche development through a citizen-centric and community-led approach [58]; (2) Fewer policy priorities have been given by the Seoul government on grid enhancement to take up more RE from mini-PVs (Interviewee 7b). Under the partial electricity market reforms in South Korea, the national government provided insufficient incentives for the utilities to enhance grid capacity, nor did the Seoul government have the authority to provide such incentives; and (3) Seoul-type REFIT could only be offered to limited sizable solar PV projects instead of covering mini-PV projects under the existing grid infrastructure.
These contextual factors contributed to the conducive and prohibitive conditions in the niche developments in Seoul, and partly explained why the development could not be scaled up to regime shift. Although these factors might not be directly attributed to the outcome of the subsidy policy, these factors limited the potential of using REFIT to promote community solar in Seoul. As such, subsidies and other incentive programs, such as eco-mileage, were utilized to incentivize citizens' engagement under the existing politico-economic contexts.

Understanding the Niche-Regime Dynamics across National, City, and Community Levels
To sum up, our case study shows that political and economic contexts have created an embedded environment for five critical factors that have been influencing the niche-regime dynamics of Seoul's urban solar developments ( Table 3). The current political and governance systems in South Korea have strengths in aligning the national macro-economic policy with the industrial development policy of hi-tech new energy clusters, political openness that enables community engagement, and building extensive social and political networks, both horizontally and vertically. The current systems, however, lack sufficient forces for change, in part because of the "development state" ideology, the existence of incomplete electricity market reforms, and the lack of strategic roles of the state in governing the sustainable growth of technological niches.
Our scalar perspective that emphasizes niche-regime dynamics across national, city, and community levels also sheds light on the complexities involved. Our case study demonstrated that the politico-economic context affects niche diffusion in both positive and negative ways at the national, city, and community levels. We found that in some indicative areas of our framework, there exists a delicate relationship across the national, city, and community levels. For example, in relation to the first factor: Global trends, ideologies, and public preference, the widespread public awareness of nuclear risks at the national level, the prioritization of social considerations in nuclear policy-making in Seoul, and the citizen movement at the community level have reinforced each other across different administrative levels. A set of illustrative examples is summarized in Table 3.

Conclusions and Policy Implications
By integrating political economy and socio-technical energy transitions theories, this paper seeks to contribute novel insights to the energy literature. Utilizing a case study of the urban solar community in Seoul, this paper underscores the importance of politico-economic contexts in creating embedded conditions that define the opportunities and constraints of niche development processes. Our empirical analysis demonstrates the complex interactions in energy transitions and contributes to the literature in three important ways.
Firstly, we characterized Seoul's model of niche developments as a government-empowered community-led solar approach. This finding enriches the understanding of the variety of transition pathways growing rapidly worldwide (see, for example, [98][99][100]). Indeed, Seoul's approach to engaging communities and citizens in urban solar is atypical compared with initiatives in other global cities. London, for example, focuses on solar deployment in low-income social housing supported by a robust social enterprise sector [101]. Singapore, on the other hand, relies on market forces and central tendering processes coordinated by the government to promote solar in social housing [102]. This case study of Seoul can therefore enrich the literature by providing a crucial context for comparative studies and explaining the resulting varieties in transition pathways and outcomes.
Secondly, we conceptualized the mechanisms of niche-regime interactions and provided greater clarity to complex socio-technical transitions processes. A growing body of energy transitions studies argues that transitions involve long, complex, and uncertain processes that take place at various geographical levels [9]. Our study makes a contribution to the literature by specifying five factors that are shaped by political and economic contexts, and which, in turn, affect niche-regime dynamics. Global trends and public preferences, political power structure and governance approaches, physical availability of energy sources, electricity market reforms, and visioning and leadership have impacted the niche development process in significant ways, as we discussed.
We also argued that the politico-economic contexts are a double-edged sword, creating critical conducive conditions for niches' growth and diffusion, yet major inhibitive conditions that constrain niche developments and reinforce carbon/nuclear "lock-ins". Our assessment of Seoul's niche development argues that the Seoul model has made progress in technological niches with some emerging developments towards market niches, but is far from initiating regime shifts. Our analysis suggests that the outcomes of energy transitions depend on an array of factors, as well as complex interactions between forces for and against change. In Seoul, the forces against change have counteracted the forces for change, subsequently resulting in limits in transitions progress. Our case study has shown that political economy analysis of energy transitions is significant in offering a better understanding about the conditions conducive to or impeding more effective governance. Our conceptualization allows us to make predictions on the governing capacity of energy transitions; the more conducive conditions exist, the more likely that there are effective energy transitions.
Thirdly, the multi-scalar perspective in this case study highlights the multiple and often conflicting trends, values, preferences, and governing approaches of different actors with regard to niche development and regime change. Niches are shaped not only at the local level, but also by politico-economic factors at the city and national levels. Our case study confirms the multi-scalar research that states local sustainability decisions and actions are seldom entirely local, but are conditioned by the values, priorities, and policies of state and non-state actors on various geographic and administrative scales [103]. We also confirm the literature that states a scale-sensitive governance system is needed for energy transitions to respond to inter-scalar political interactions [31].
Our findings have various policy implications. We shed more light on what conditions are promoting and impeding niche development, and where these conditions are (at which spatial scales-national, city, or community). Three policy recommendations can be derived from our findings. Firstly, governments can apply our framework to critically evaluate whether the current energy systems and the associated governance and political systems are well equipped to enable the desired energy transitions. Policies and governance strategies should then focus on reinforcing the conducive conditions or positive drivers for change that exist, and on addressing the inhibitive conditions. Secondly, governments need to give sufficient attention to "operational" strengths and limits of various scales of transitions. In the case study, the community in Sungdaegol acts as a niche testbed, but this testbed has been conditioned by the broader contexts at Seoul's city and national levels. In some important aspects, Sungdaegol has made good progress in technological niche developments. However, the "developmental state" ideologies and incomplete electricity market reforms, for example, have constrained the further development of market niches. Our multi-scalar research approach suggests that governments must focus on leveraging existing or potentially complementary or reinforcing effects across the three administrative levels.
Thirdly, our findings reveal the difficulties for governments to assume new roles in energy transitions. The strong solar policies, particularly in the form of direct subsidies introduced by Seoul's mayor, may present a problem of excessive government intervention, as the government has overlooked its role in building markets for a sustainable solar industry. There is, for example, minimal demand for loans. Governments need to be responsive enough to assume new roles and retreat from some.
Energy transitions are context-dependent. This case study of Seoul has limitations in generalizability. However, it is important to note that our conceptualization of niche-regime interactional mechanisms is not exclusive to the Korean context, and can be applied to energy transitions research in other national contexts. In relation to future research directions, a comparative study of a number of case cities with diverse national institutional contexts would test the generalizability of the framework. Furthermore, this may assist in identifying cities where the environment is more conducive to niche development and which might therefore be more likely to deliver energy transitions towards sustainability.

5.
A chairman of resident representatives of a residential property in Dongjak-gu,