| 1. |
- Basset, F. Basso, et al.
(författare)
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Entanglement Swapping with Photons Generated on Demand by a Quantum Dot
- 2019
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 123:16
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Tidskriftsartikel (refereegranskat)abstract
- Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test of quantum mechanics and an essential resource to the realization of quantum networks. Probabilistic sources of nonclassical light were used for seminal demonstration of entanglement swapping, but applications in quantum technologies demand push-button operation requiring single quantum emitters. This, however, turned out to be an extraordinary challenge due to the stringent prerequisites on the efficiency and purity of the generation of entangled states. Here we show a proof-of-concept demonstration of all-photonic entanglement swapping with pairs of polarization-entangled photons generated on demand by a GaAs quantum dot without spectral and temporal filtering. Moreover, we develop a theoretical model that quantitatively reproduces the experimental data and provides insights on the critical figures of merit for the performance of the swapping operation. Our theoretical analysis also indicates how to improve stateof-the-art entangled-photon sources to meet the requirements needed for implementation of quantum dots in long-distance quantum communication protocols.
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| 2. |
- Glad, Wiktoria, et al.
(författare)
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Collaboration for reduced energy use in Swedish rental flats – a socio-technical perspective
- 2012
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Ingår i: Proceedings 11th IAS-STS Annual Conference 7-8 May 2012.
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Konferensbidrag (refereegranskat)abstract
- People want to live a good life, what this means varies greatly between people and households, however for all it is important to have a home that is comfortable to live in. It should be warm enough, light and there should be room for mundane activities. However, this requires energy: heating, lighting and household appliances.The Swedish Parliament’s goal is to reduce energy use in residential and commercial buildings by 20% in 2020. Research shows that there is a potential in behaviour change among residents in apartment buildings as well as in the operation and maintenance of buildings, which can lead to energy savings between 15 and 30 percent.The project is based on a joint responsibility and involvement of researchers and housing company Stångåstaden, based in Linköping, Sweden, and owner of 18,600 flats. It is a 5 year project, where so far one year of research has been completed. The energy efficiency goal of Stångåstaden is 25 % by 2025.The aim of the research project is to reduce energy by applying existing and developing new knowledge and new approaches in cooperation with Stångåstaden. The general research approach is socio-technical and case study methodology. Both qualitative and quantitative data collections methods have been used. Tentative results show that it is possible to identify barriers to energy efficiency, both from residents’ and professionals’ perspectives. Conclusions are that socio-technical relationships should be developed with regard to communication, knowledge and technical system.
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| 3. |
- Glad, Wiktoria, et al.
(författare)
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Stated energy behaviour in Swedish public housing– a questionnaire study
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper is based on results from an ongoing research project targeting energy behaviour in Swedish public housing. The aim is to map stated energy behaviour in the 18,600 flats owned by the housing company Stångåstaden in Linköping, Sweden.Our starting points are that households play a crucial role when it comes to energy efficiency. Energy is mostly used indirectly and is invisible. Many of our daily activities in our household involve the use of energy, referring to routines that we have in our everyday life. People warm or cool their apartments, turn the light on, cook, do laundry or use other appliances – this requires energy. The energy consumption varies greatly between people and households, however for all it is important to have a home that is comfortable to live in. The energy saving potential lies around 15 to 30% regarding behaviour change among residents in apartment buildings as well as in the operation and maintenance of buildings. Stångåstaden recently launched an energy efficiency goal of 25 % by 2025. Earlier, the Swedish Parliament set a goal of 20 % by 2020 for residential and commercial buildings.The Stångåstaden residential buildings constitute the case study of this research and have been explored using a paper questionnaire. The questionnaire was mailed to 1200 households in December 2011. The response rate was around 50 %. The focus of the analysis lies at the everyday energy-related behaviour and practices in the households to establish different behaviours in relation to different background variables. Practices that are included are the specific heating, lighting, use of appliances for cooking, washing and entertainment. Conclusions are that there is an energy efficiency potential corresponding to the goals of Stångåstaden, but this is embedded in practices that are more or less difficult to change.
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| 4. |
- Hanschke, Lukas, et al.
(författare)
-
Coherent scattering: either sub-natural linewidth or anti-bunched light
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Epitaxial quantum dots have emerged as one of the best single–photon sources, not only for applications in photonic quantum technologies but also for testing fundamental properties of quantum optics. One intriguing observation in this area is the emission of photons with subnatural–linewidth from a two-level system under resonant continuous wave excitation. In particular, an open question is whether these subnatural–linewidth photons exhibit simultaneously single–photon characteristics, i.e. show antibunching as a signature of single-photon emission. Here, we demonstrate that this simultaneous observation of subnatural–linewidth and single photoncharacter is not possible with simple resonant excitation. First, we independently confirm single–photon character and subnatural–linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our experimental work is consistent with recent theoretical findings, and can be explained by a fundamental model considering higher-order photon correlations.
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| 5. |
- Hanschke, Lukas, et al.
(författare)
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Origin of Antibunching in Resonance Fluorescence
- 2020
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 125:17
-
Tidskriftsartikel (refereegranskat)abstract
- Resonance fluorescence has played a major role in quantum optics with predictions and later experimental confirmation of nonclassical features of its emitted light such as antibunching or squeezing. In the Rayleigh regime where most of the light originates from the scattering of photons with subnatural linewidth, antibunching would appear to coexist with sharp spectral lines. Here, we demonstrate that this simultaneous observation of subnatural linewidth and antibunching is not possible with simple resonant excitation. Using an epitaxial quantum dot for the two-level system, we independently confirm the single-photon character and subnatural linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our observation is explained by antibunching originating from photon-interferences between the coherent scattering and a weak incoherent signal in a skewed squeezed state. This prefigures schemes to achieve simultaneous subnatural linewidth and antibunched emission.
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| 6. |
- Heiskanen, Eva, et al.
(författare)
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From shadows to light: The role of latent networks in mainstreaming solar PV practices
- 2024
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Ingår i: Environmental Innovation and Societal Transitions. - 2210-4232. ; 50
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Tidskriftsartikel (refereegranskat)abstract
- Practice theories have generated interest in sustainability transitions research as a means to study shared expectations, conventions and routines that maintain unsustainable consumption within the dominant regime. However, collective action to change practices, which is crucial for innovation, is seldom examined in practice theory research. This article applies practice theories to conceptualize the nature of collective action in shaping energy practices, using insights from a literature review on residential photovoltaic (PV) production by German citizens. We demonstrate the significance of latent networks, which refer to individuals involved in similar parallel practices, in promoting the adoption of solar power in homes. Our results show that both multi-actor and latent networks contributed to mainstreaming residential solar PV practices. Multi-actor networks encompassed households and various service providers, each integrated within larger latent networks.
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| 7. |
- Janda, Kathryn B., et al.
(författare)
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Making more of middles: advancing the middle-out perspective in energy system transformation
- 2019
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Ingår i: eceee 2019 Summer Study on energy efficiency: Is efficient sufficient?. - 9789198387803 - 9789198387810 ; , s. 199-204
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Konferensbidrag (refereegranskat)abstract
- Social and technological innovations are commonly seen as either being induced from the ‘top-down’ – e.g., by policymakers – or evolving from the ‘bottom-up’ – e.g., by consumers. Instead, a ‘middle-out’ perspective (MOP) focuses on agents of change that are located in the middle, between the top and the bottom. Janda and Parag (2013) and Parag & Janda (2014) describe how middle actors include (but are not limited to) such groups as building professionals, religious congregations, and commercial property owners (Janda & Parag 2013; Parag & Janda 2014). In recent years, these and other authors have further developed the MOP to address providers of housing refurbishment (Janda, Killip & Fawcett 2014), heating engineers (Wade, Hitchings & Shipworth 2016), community-based organizations (Hamilton et al. 2014), facilities managers (Goulden & Spence 2015), social housing providers (Cauvain & Karvonen 2018), and actors involved in energy storage (Devine-Wright et al. 2017). This paper focuses on recent advances in the ‘middleout perspective’. It considers several new middle actor groups, including an energy committee for orthodox Jews in Israel (Parag 2018), code officials in India (Janda & Khosla 2018), formal social groups in Swiss cities (Blumer et al. 2018; Frick et al. 2017), professionals working with housing providers in Sweden (Reindl 2017), local authorities and delivery agents in Scotland (Bush, Wade & Webb 2018), and housing developers in the USA (Agee et al. 2018). These cases demonstrate new applications of the MOP, bring additional theoretical perspectives to bear (such as practice theory) and further develop the use of perspectives already recognized within the MOP (e.g., system of professions). By looking across these, this paper develops the MOP with respect to other work on intermediaries, professionals, and communities of practice. To increase practical use of the MOP, the paper encourages future authors to clarify both the direction and scale of middle-actor impacts.
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| 8. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 9. |
- Palm, Jenny, et al.
(författare)
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New Clean Energy Communities in a Changing European Energy System (NEWCOMERS) : Deliverable D3.1 Description of polycentric settings in the partner countries
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable maps the prevailing polycentric settings of six studied countries. The studied countries are the partner countries for the NEWCOMERS project, i.e. Germany, Italy, the Netherlands, Slovenia, Sweden and the United Kingdom. In this report, the countries' polycentric settings will be described in relation to the polycentric framework developed in WP 2, with specific focus on the technical system and actors. The factors in focus for the country descriptions are socio-economic conditions, technical system (electricity and heat), institutional arrangements as well as actors. Additionally, a description of energy communities in each country is presented, showing different developments in this area.The research was conducted through a desktop research. Existing literature, reports as well as statistical information were gathered and then organised according to the factors chosen.The aim in this delivery is to describe and understand the national polycentric settings as a first step to understand the emergence of new forms of energy communities. This deliverable is the basis for delivery 3.2, which will compare different polycentric national settings and delivery 3.3, which will evaluate what forms of energy communities work best in different polycentric setting and what are the potentials for learning between different polycentric settings.
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| 10. |
- Palm, Jenny, et al.
(författare)
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Understanding barriers to energy-efficiency renovations of multifamily dwellings
- 2018
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Ingår i: Energy Efficiency. - : Springer Science and Business Media LLC. - 1570-646X .- 1570-6478. ; 11:1, s. 53-65
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Tidskriftsartikel (refereegranskat)abstract
- We have studied how energy efficiency is discussed by professionals during renovation of multifamily dwellings, in order to capture how barriers in relation to energy measures are appearing, disappearing and transformed during the process. We did participatory observations of renovation meetings, conducted interviews with the involved professionals and studied-related documents. Our intentions have not been to assess decisions made, but to follow the process to gain a different understanding of how barriers can be understood during renovations. We can conclude that the renovation process is based on a complex series of contractural relationships, where assymetric information and lack of common goals contribute to split incentives. The results also show that the housing company’s internal organisation becomes a barrier where assymetric information and split incentives also became an in-house barrier. The decisions were often based on bounded rationality where calculations were surprisingly absent in meetings and during discussions on energy measures.
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| 11. |
- Palm, Jenny, et al.
(författare)
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Understanding energy efficiency in Swedish residential building renovation: A practice theory approach
- 2016
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Ingår i: Energy Research & Social Science. - : ELSEVIER SCIENCE BV. - 2214-6296 .- 2214-6326. ; 11, s. 247-255
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Tidskriftsartikel (refereegranskat)abstract
- Examining renovation processes having reduced energy consumption as an explicit goal, this article considers how energy efficiency is made part of renovation processes, focusing on the planning and design phase. Interviews and participant observations of meetings have been conducted. Applying a framework developed in practice theory, we demonstrate the importance of understanding routines, technology, meanings, and knowledge in order to understand why renovation processes repeat themselves and why a renovation practice are hard to change. The analysis shows that the professionals were only engaged in decisions in relation to their own specialized areas, which benefited established solutions. The existing technical infrastructure, such as the HVAC shafts and the district heating system, largely determined what issues were up for discussion. It was clear that practical know-how were valued much higher than theoretical knowledge. The meaning of an energy efficient renovations for the professionals was to reduce the energy consumed as much as possible in every renovated building. With this in mind, we were surprised by how little energy efficiency was on the agenda. We can conclude that there was nothing in the studied processes that could trigger changes and dislodge the inertia of the practice. (C) 2015 Elsevier Ltd. All rights reserved.
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| 12. |
- Palm, Jenny, et al.
(författare)
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Understanding tenants’ responses to energy efficiency renovations in public housing in Sweden : From the resigned to the demanding
- 2020
-
Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 6, s. 2619-2626
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the experiences of tenants in renovation projects of public housing rental apartments in Sweden. Tenants’ perspectives are under-researched in the context of energy efficiency renovation projects, which is a considerable oversight given the many ways in which such projects impact their lives. The aim of the paper is to reveal rare qualitative insights into tenants’ experiences of, and attitudes towards, energy efficiency renovations in a public housing context and the extent to which they feel motivated and able to influence the renovation project. Participatory observations at tenant meetings were conducted as well as semi-structured phone interviews. An empirically driven typology is developed indicating that tenants have different interests and attitudes regarding energy efficiency renovations. Six different types are identified: the satisfied; the demanding, the conservative, the resigned, the sceptical and the resistant.
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| 13. |
- Reindl, Katharina
(författare)
-
Agency and capacity in the planning and design phase of building renovations
- 2020
-
Ingår i: Energy Efficiency. - : Springer Science and Business Media LLC. - 1570-646X .- 1570-6478.
-
Tidskriftsartikel (refereegranskat)abstract
- The building sector is a large energy consumer and is responsible for high CO2 emissions; hence, improving the energy performance of buildings is vital. Building renovations open opportunities to improve their energy performance.Building professionals and other actors in the early phase of renovations decide what energy efficiency and saving measures will be implemented. Their role is studied here from a middle-out perspective (MOP), investigating the different actors’ agency and capacity. Agency refers here to an interest in and a willingness to implement energy efficiency and saving measures, and capacity refers to the ability to implement such measures. Higher agency and capacity are said to increase the realisation of the planned energy efficiency and saving measures.The data was gathered during three planning and design phases of renovation projects of a municipal housing company in a middle-sized Swedish town. A case study was conducted which is based on semi-structured interviews with actors from the planning and design phase of the renovations, as well as participant observations and a document analysis.The levels of agency and capacity of professionals in the middle of a project’s planning and design phase are investigated thoroughly, but the here defined top and bottom levels are also in focus. The analysis shows that a mismatch in agency and capacity on the different levels hindered the uptake of energy efficiency and saving measures in the planning and design of the renovation projects.
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| 14. |
- Reindl, Katharina, et al.
(författare)
-
Circular Economy Integration in Smart Grids: A Nexus for Sustainability
-
Ingår i: Circular Economy and Sustainability. - 2730-5988.
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Tidskriftsartikel (refereegranskat)abstract
- The increased electrification of society and the development of smart grids are often seenas central in the transition towards a more sustainable and secure energy system and necessaryto address the challenges of increasing energy demand and limited resources. Thereare many visions and ideas on what a smart grid is or could be. While most research relatedto environmental impacts on the smart grid focuses on the energy and climate implications,there is a growing interest in looking into material aspects and resource use, i.e., the CircularEconomy (CE) dimensions of the grid. It is increasingly understood that the varioustechnologies in the grid, such as grid infrastructure and electric vehicles, will require massiveamounts of natural resources. This research explores how smart grids can integrate CEconsiderations and the current state of knowledge related to CE issues in smart grid discussionsin Sweden. The main methods employed were a literature review and semi-structuredinterviews with 19 stakeholders. The results show that limited literature deals directly withhow CE issues can be integrated with smart grid development. The interviews show thatvarious stakeholders have started to discuss these issues, but the discussion is still in itsinfancy for most of them. The interviewees also pointed to several barriers to developing amore “circular” grid, such as regulatory frameworks, network maintenance, financing, andcost considerations.
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| 15. |
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| 16. |
- Reindl, Katharina, et al.
(författare)
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Energy efficiency in the building sector: a combined middle-out and practice theory approach
- 2020
-
Ingår i: International Journal of Sustainable Energy Planning and Management. - 2246-2929. ; 28, s. 3-3
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Tidskriftsartikel (refereegranskat)abstract
- AbstractThe building sector in Sweden and Europe is a major energy consumer, accounting for around 40% of total energy use. It is a challenge to optimize available technical and social strategies for the fragmented construction industry. Professionals such as architects and different building engineers play a crucial role in the technology adoption process.This study aims to contribute to the understanding of how and why energy efficiency and saving measures are implemented by different professionals. The paper combines perspectives focusing the “the middle” in an organisation and social practice theory (SPT) to develop a framework which can be used to enhance the understanding of how and why energy efficiency measures are adopted in building processes. By combining these theoretical perspectives it is possible to arrive at a deeper understanding of what needs to be changed in the planning and management process to achieve a highly energy efficient renovation.
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| 17. |
- Reindl, Katharina, et al.
(författare)
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Exploring PV Adoption by Non-Residential Property Owners: Applying Social Practice Theory
- 2024
-
Ingår i: International Journal of Sustainable Energy Planning and Management. - 2246-2929. ; 41, s. 20-33
-
Tidskriftsartikel (refereegranskat)abstract
- This article explores the emergence of PV adoption practices among non-residential property owners in Sweden to deepen insights into PV diffusion and accelerate a renewable electricity transition. It applies a social practice theory approach to show how different practice elements need to come together to establish a PV adoption practice.Twenty-five semi-structured interviews were conducted with private and public non-residential property owners in southern Sweden. The results show that about half of the property owners had PV systems installed for a long period and had developed a PV adoption practice. These property owners had energy and environmental goals formulated, interacted with tenants, established routines within the company, aggregated relevant knowledge, established trusted relationships with PV installers and considered PVs a mature technology that supported the PV adoption process. On the contrary, first-time installers and non-adopters without an established PV adoption practice were missing these elements.This study is the first step towards understanding PV adoption as a practice for non-residential property owners. It contributes to an analysis of the elements that are required for a PV adoption practice to emerge. The practical relevance of the study is that it can facilitate and support non-residential property owners to adopt PV systems and contribute to a renewable electricity transition.
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| 18. |
- Reindl, Katharina, et al.
(författare)
-
Fastighetsägare som prosumenter – stödstrukturer och hinder
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Solceller har en viktig roll att fylla för att uppnå politiskt fattade mål om 100%hållbart elsystem. Det är rimligt att anta att det är i bebyggelsen som en storutbyggnad kommer att behöva ske eftersom det är existerande strukturermed nätanslutningar där det också finns möjlighet att använda den solel somproduceras. Fastighetsägare blir därmed en viktig aktörsgrupp att engagera.En relativt outforskad grupp är fastighetsägare till lokaler och det är dem somär fokuserade i detta projekt.Det övergripande syftet med detta projekt är att kartlägga och analyseraförutsättningar för att vi ska se en betydande ökning av antalet prosumenterhos privata och offentliga fastighetsägare av lokaler och vilken betydelse ensådan ökning kommer att få för elsystemens etablerade aktörer.Studien har genomförts i samverkan mellan Lunds universitet och EnergikontorSkåne. En litteraturstudie, en enkät och intervjuer har kombinerats ochdet är fastighetsägare med fastigheter i Skåne som varit i fokus.De vanligaste hindren för att installera solpaneler var kopplade till ekonomi,information och kunskap och administration. Även brist på lagringsmöjligheteroch affärsmodeller för hur kostnader och vinster ska fördelas bland hyresgästernämndes av flera. Vanliga drivkrafter som omnämndes var tillgången tillsubventioner, att det fanns ett miljöengagemang i företaget och möjlighetenatt minska framtida kostnader. I Sverige lyfte fastighetsägarna också frambyggnadsrenoveringar som en drivkraft, där en renovering skapade möjlighetenatt samtidigt installera solceller.Teknik omnämndes av viss som hinder och andra som möjlighet. En delfastighetsägare var entusiastiska över att testa den nya tekniken och såg solcellersom en enkel teknik. Andra fastighetsägare tyckte att tekniken kändessvår att ha i fastigheten. Ytterligare några vara oroliga att effektiviteten hossolcellerna skulle minska snabbare än vad säljarna uppgav eller att teknikensnart skulle bli föråldrad på grund av den snabba tekniska utvecklingen.
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| 19. |
- Reindl, Katharina, et al.
(författare)
-
How interdisciplinary are Master’s programmes in sustainability education?
- 2020
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Ingår i: Interdisciplinary pedagogy in higher education : Proceedings from Lund University's Teaching and Learning Conference 2019 - Proceedings from Lund University's Teaching and Learning Conference 2019. ; , s. 61-61
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 20. |
- Reindl, Katharina, 1984-
(författare)
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Implementing energy measures in renovations for multi-family dwellings : Influence and practice of professionals
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aging buildings will sooner or later be in need of renovation, which opens opportunities to reduce energy use. Even if economically feasible energy measures or technologies exist, they are not always implemented, leading to an energy efficiency gap. This dissertation deals with how energy measures are handled and why they are enabled or disabled during the planning and design of renovations. During renovations, different kinds of building professionals are engaged, here referred to as middle professionals. The meeting practice of the professionals is investigated, with a focus on how the middle professionals exert influence from the middle-out and to the top and bottom, and how and why they enable or disable measures aimed at energy efficiency or reduction. Three renovation projects are followed in the municipality-owned housing company Stångåstaden, in Linköping, Sweden. The housing company’s goal is to reduce the amount of purchased energy by 25% by 2025. Methods applied during the research are semi-structured interviews, participant observations and document analysis. The conclusions show that energy measures were implemented, but more can be done in renovations. Predefined meeting agendas make the process efficient but not flexible, thus it can be difficult to introduce innovations and alternative ways of thinking into the process. The professionals usually selected measures they had used before. Energy calculations attracted little interest compared to the aggregated knowledge from previous projects, and experience and tacit knowledge were highly valued. This and more lead to a renovation process where it is difficult for energy to enter the current meeting practice.
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| 21. |
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| 22. |
- Reindl, Katharina, et al.
(författare)
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Installing PV: Barriers and enablers experienced by non-residential property owners
- 2021
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Ingår i: Renewable & Sustainable Energy Reviews. - : Elsevier BV. - 1364-0321. ; 141
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Tidskriftsartikel (refereegranskat)abstract
- There is huge potential to increase installation of photovoltaics (PV) using the roofs of non-residential buildings. While barriers to and enablers of the adoption of PV in residential buildings are well studied, this is not the case for non-residential buildings. This article is intended to fill this research gap by mapping barriers to and enablers of PV adoption by property owners of non-residential buildings. This was done through a literature review and an empirical study in Sweden using a survey and semi-structured interviews.Common barriers identified in earlier research and in the present Swedish empirical study include economic, information/knowledge, and administrative/organizational barriers. New barriers identified in this Swedish study include building construction, lack of electricity storage, and tenants’ existing electricity supply contracts. Enablers identified in this Swedish and in earlier research include subsidies, environmental concerns, and expense reduction. The Swedish material also revealed enablers not mentioned in earlier studies, such as the opportunity to earn money and taking advantage of third-party ownership.Mapping barriers and enablers in research and in practice is an important step to understand why a wider diffusion is not happening. It is also important for developing new, creative ways of approaching companies and as a base when developing policy interventions. This study contributes to such a mapping for the non-residential sector.
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| 23. |
- Sattlegger, Lukas, et al.
(författare)
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Plastic Packaging, Food Supply, and Everyday Life : Adopting a Social Practice Perspective in Social-Ecological Research
- 2020
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Ingår i: Nature and Culture. - : Berghahn Books. - 1558-5468 .- 1558-6073. ; 15:2
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Tidskriftsartikel (refereegranskat)abstract
- This article presents practice-theoretical conceptions of societal relations to nature as a fruitful alternative to common system approaches in social-ecological research. Via the example of plastic food packaging, two different practice-theoretical approaches to food supply are discussed regarding their suitability for relating the material properties of packaging to their everyday use by producers, retailers, and consumers: (1) the network approach (portraying food supply as a network of practices; these practices include material elements that interrelate with other elements like competence or meaning) and (2) the nexus approach (investigating the interrelation between social practices and material arrangements in which they take place). Depending on the given research interest, both perspectives have their pros and cons: the network approach is stronger in understanding the everyday use of technologies, while the nexus approach encourages the integration of infrastructures and environmental contexts that are not directly observable within the practice.
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| 24. |
- Schweickert, Lucas, et al.
(författare)
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On-demand generation of background-free single photons from a solid-state source
- 2018
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 112:9
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Tidskriftsartikel (refereegranskat)abstract
- True on-demand high-repetition-rate single-photon sources are highly sought after for quantum information processing applications. However, any coherently driven two-level quantum system suffers from a finite re-excitation probability under pulsed excitation, causing undesirable multi-photon emission. Here, we present a solid-state source of on-demand single photons yielding a raw second-order coherence of g((2)) (0) = (7.5 +/- 1.6) x 10(-5) without any background subtraction or data processing. To this date, this is the lowest value of g((2)) (0) Peported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting single-photon detectors with ultralow dark-count rates of (0.0056 +/- 0.0007) s(-1) and (0.017 +/- 0.001) s(-1), respectively. Re-excitation processes are dramatically suppressed by (i), while (ii) removes false coincidences resulting in a negligibly low noise floor.
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| 25. |
- Schöll, Eva, et al.
(författare)
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Crux of Using the Cascaded Emission of a Three-Level Quantum Ladder System to Generate Indistinguishable Photons
- 2020
-
Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 125:23
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the degree of indistinguishability of cascaded photons emitted from a three-level quantum ladder system; in our case the biexciton-exciton cascade of semiconductor quantum dots. For the three-level quantum ladder system we theoretically demonstrate that the indistinguishability is inherently limited for both emitted photons and determined by the ratio of the lifetimes of the excited and intermediate states. We experimentally confirm this finding by comparing the quantum interference visibility of noncascaded emission and cascaded emission from the same semiconductor quantum dot. Quantum optical simulations produce very good agreement with the measurements and allow us to explore a large parameter space. Based on our model, we propose photonic structures to optimize the lifetime ratio and overcome the limited indistinguishability of cascaded photon emission from a three-level quantum ladder system.
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