| 1. |
- Ahlborg, Helene, 1980, et al.
(författare)
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Thirty-five years of research on energy and power: A landscape analysis
- 2024
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Ingår i: Renewable and Sustainable Energy Reviews. - 1879-0690 .- 1364-0321. ; 199
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Forskningsöversikt (refereegranskat)abstract
- The urgent need to mitigate climate change and decarbonise the energy sector brings the risk that wider social and environmental concerns about the sustainability of energy systems are neglected. Countries may achieve decarbonization goals while reproducing or worsening the unequal distribution of access, opportunities, costs and burdens that is inherent to current energy systems. This study is motivated by the tension between visions for change towards sustainable energy systems and historic and contemporary inequities on the ground. The study contributes a quantitative, global-scope overview of existing research that places energy users and their lives at the centre of analysis for inclusive and equitable transitions. It further identifies the themes, concepts and perspectives that dominate scholarly debate and analyses the presence and relative influence of work that explicitly considers relations of power. The stepwise review uses the Scopus database and multiple bibliometric tools, covering the period until June 2022. It adopts a novel approach to identify dominant and marginal topics, geographical contexts and theoretical lenses employed including the uptake of critical social science approaches. The results indicate that dominant studies fail to engage critically with relationships of power. Even within the debate on “energy poverty”, work based in critical theory approaches account for less than seven percentages of the total body of work. For work on “energy justice” and users, four percentages of publications account for gender. The dominant language is technical and depoliticized. The study identifies research gaps and promising avenues for further research.
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| 2. |
- Alves, Joao S., et al.
(författare)
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Experimental investigation on performance improvement by mid-plane guide-vanes in a biplane-rotor Wells turbine for wave energy conversion
- 2021
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- The Wells turbine is the most frequently used or proposed self-rectifying air turbine for oscillating-water column wave-energy converter application, largely because of its conceptual and mechanical simplicity. Biplane Wells turbines allow a higher total blade solidity to be attained than monoplane turbines do, but this results in larger aerodynamic losses associated with the swirl kinetic energy loss at turbine exit. This may be overcome by the presence of a row of guide vanes between the two rotor planes, a solution that had been proposed and investigated theoretically or by numerical modelling. Results of turbine overall performance and flow details are reported from laboratory tests of a biplane Wells turbine without guide vanes and with specially designed guide vanes. The presence of the guide vanes was found to increase the peak efficiency by seven percentual points, while reducing (for fixed rotational speed) the damping provided by the turbine. Measured losses in the guide vane row were much smaller than in the rotors. Experimental results are compared with previously published numerical results. A stochastic theoretical transform was applied to obtain averaged results for the turbine performance subject to the irregular bidirectional air flow induced by real sea waves.
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| 3. |
- Andersson, Johnn, 1983, et al.
(författare)
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Photovoltaics in Sweden – Success or failure?
- 2021
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Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 143
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Tidskriftsartikel (refereegranskat)abstract
- Promoting global energy transitions while stimulating domestic industrialization requires national policymaking that shapes technological innovation towards specific outcomes. Although this is inherently difficult, historical case studies may bring a better understanding of innovation dynamics and thereby guide the design of future policy interventions. The purpose of this paper is to review and analyze the emergence of Swedish photovoltaics technology from a policy perspective. Our main aim is to provide a retrospective account of historical developments, but we also derive more general insights about technological innovation and related policy challenges. The paper departs from an adapted analytical framework based on the technological innovation systems approach. Our review identifies four decades of Swedish research that has largely failed to drive domestic commercialization, the rise and fall of an industry that mainly served international markets, and a rapidly growing domestic market based on imported products. This situation is the result of mismatches and fragmentation among key innovation processes, which have not been addressed by strategic policy interventions. We suggest that policymakers should promote a full range of innovation processes and consider making innovation support subject to a payback mechanism that delivers a return on public investments even if industries and markets emerge abroad. Our study also demonstrates how the technological innovation systems approach can be extended to include the function commercialization and emphasizes the importance of paying attention to the directionality of technological innovation processes.
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| 4. |
- Andrei, Mariana, 1981-, et al.
(författare)
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Exploring a decarbonization framework for a Swedish automotive paint shop
- 2024
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 200
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Tidskriftsartikel (refereegranskat)abstract
- The automotive industry is the world’s largest manufacturing activity, characterized by complex productionprocesses and some energy-intense processes which use a significant quantity of raw materials. The production processes responsible for the highest energy end-use take place in the paint shop. Depending on the type of paintshop processes, the energy use can account for up to 75 % of the plant’s total energy end-use. This study aims to contribute to an enhanced understanding of the complexity of adopting decarbonization measures and to provide support for planning and decision-making in practice. By adopting a bottom-up perspective, a longitudinal case study was conducted on a state-of-the-art automotive paint-shop between November 2019 and March 2023. To achieve the study’s aim, a bottom-up methodology was developed comprising several steps: i) analysis of decarbonization measures, ii) mapping of process energy use and CO2 emissions, and iii) economic analysis. The data-based methodology is flexible and can be applied in different automotive paint-shops. Main findings show that i) incremental energy efficiency measures have the fastest adoption level, with relatively high savings potential,and most of these are cost effective; ii) radical process innovation measures have a higher savings potential, but long-term adoption levels due to the radical innovations required in the supply chain, and the highly specialized knowledge needed in the pre-treatment process; and iii) the primary drivers for implementing the measures are to achieve the climate targets and establish a leading position in the sector, rather than focusing primarily on the cost-effectiveness of the measures.
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| 5. |
- Andrei, Mariana, 1981-, et al.
(författare)
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Knowledge demands for energy management in manufacturing industry - A systematic literature review
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 159
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Forskningsöversikt (refereegranskat)abstract
- The social context in relation to energy policies and advances in more energy efficient technologies is changing constantly, thus driving a need for change in the manufacturing sector. This study presents a knowledge-based framework that enables the understanding of the model for knowledge that has taken industrial energy efficiency to current levels and the analysis of the model in the current context of industry transition. The framework consists of three broader forms of knowledge and specific knowledge attributes that can capture the knowledge employed in industrial energy management. The framework is applied in a systematic literature review, analyzing the forms of knowledge and main aspects of energy management in manufacturing industries from 157 articles published between 2010 and 2020 in various academic journals. Besides the framework, the results show that the technical form of knowledge is the primary type of knowledge employed in energy management and that a paradigm-changing towards Industry 4.0. is seen. Another employed form of knowledge is process knowledge, which is concerned with the prerequisite information needed to implement energy management. Finally, lead- ership knowledge is also employed in energy management and a blend in these three forms of knowledge might move us beyond traditional knowledge towards new forms of knowledge that maximize the potential for energy management in manufacturing industries. The knowledge demands brought by Industry 4.0 for all forms of knowledge are identified and discussed.
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| 6. |
- Anukam, Anthony, et al.
(författare)
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A review of the mechanism of bonding in densified biomass pellets
- 2021
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 148
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Tidskriftsartikel (refereegranskat)abstract
- The production of durable biomass pellets have always been challenged by several factors including the lack of understanding of the mechanism involved in how particles combine to form pellets under standard conditions of the pellet press. This is because contributing factors span several molecular, microscopic, and even nanoscopic levels as biomass undergoes pelleting. The characteristics of the bonds formed between the combining particles and their relevance to the quality of pellets remains vague, no matter how quality is defined. However, even though few researchers have attempted to explain the mechanism of bonding in densified biomass pellets using different theories, none of their hypotheses supports particle bonding from a structural chemistry perspective. There are still no clear explanations which consider the role of molecular structure and the interactions of substances as milled biomass undergo pelleting. In view of these arguments therefore, this review presents an in-depth analysis of a structural chemistry perspective of the mechanism of bonding and the use of additives in densified biomass pellets and helps identify research areas needed to facilitate better understanding of bonding in densified biomass pellets. The status of current research in biomass pelleting, types of materials suitable as additives and their structural characteristics, as well as the current technical specifications of using additives are also discussed.
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| 7. |
- Awais, Fawad, et al.
(författare)
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Logistic characteristics and requirements of Swedish wood biofuel heating plants
- 2021
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier Ltd. - 1364-0321 .- 1879-0690. ; 138
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Tidskriftsartikel (refereegranskat)abstract
- The demand for wood biofuel for district heating plants and combined heat and power plants (CHPs) has increased, caused by an increase in both the number and size of CHPs. This places large demands on the logistics system supplying these plants with fuel, with a particular interest in the use of alternative modes of transport such as rail and sea. The aim of this paper is to identify the industry actors’ requirements, constraints, and preferences regarding the wood-biofuel supply chain and to identify the logistical challenges this entails, as well as how this impacts the opportunity for an increased use of alternative transport solutions. A survey was sent to all Swedish CHPs, combined with six interviews with transport companies, terminal operators, and forest companies. The study shows that the industry has a local focus that limits potential logistics and sourcing solutions. It is also challenged by urban sprawl, with expanding residential areas close to the CHPs putting further constraints on the operations. Significant variations in fuel demand, depending on unpredictable outside temperature and seasonal variation, is a further challenge. The low density of the fuel has a negative impact on transport costs and introduces a trade-off between chipping close to the forest to increase density versus more efficient chipping at the CHP. Intermodal transport only used by large plants, driven by a shortage of local fuel. © 2020 The Authors
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| 8. |
- Bartocci, Pietro, et al.
(författare)
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Bioenergy with Carbon Capture and Storage (BECCS) developed by coupling a Pressurised Chemical Looping combustor with a turbo expander: How to optimize plant efficiency
- 2022
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Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 169
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Forskningsöversikt (refereegranskat)abstract
- Carbon Capture and Storage is a technology of paramount importance for the fulfillment of the Sustainable Development Goal 7 (Affordable and Clean Energy) and the Sustainable Development Goal 5 (Climate Action). The European Union is moving rapidly towards low carbon technologies, for instance via the Energy Union Strategy. Coupling biofuels and carbon capture and storage to decarbonize the power and the industrial sector can be done through the development of BECCS (Bioenergy with Carbon Capture and Storage). Chemical Looping combustion is one of the cheapest way to capture CO2. A Chemical Looping Combustion (CLC) plant can be coupled with a turbo expander to convert energy to power, but it has to work in pressurised conditions. The effect of pressure on the chemical reactions and on fluidised bed hydrodynamics, at the moment, is not completely clear. The aim of this review is to summarize the most important highlights in this field and also provide an original method to optimize power plant efficiency. The main objective of our research is that to design a pressurised Chemical Looping Combustion plant which can be coupled to a turbo expander. To achieve this we need to start from the characteristics of the turbo expander itself (eg. the Turbine Inlet Temperature and the compression ratio) and then design the chemical looping combustor with a top down approach. Once the air and the fuel reactor have been dimensioned and the oxygen carrier inventory and circulation rate have been identified, the paper proposes a final optimization procedure based on two energy balances applied to the two reactors. The results of this work propose an optimization methodology and guidelines to be used for the design of pressurised chemical looping reactors to be coupled with turbo expanders for the production of power with carbon negative emissions.
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| 9. |
- Bartusch, Cajsa, 1965-, et al.
(författare)
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Opening the black box of demand response : Exploring the cognitive processes
- 2024
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 189
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Tidskriftsartikel (refereegranskat)abstract
- Evaluations of price-based demand response programs tend to focus on users' electricity use patterns and/or their practical experiences. Less is known about the effects that price-based demand response programs have on cognitive drivers and barriers to energy-using behaviors and habits, or how well these predict timing of households' electricity use. This study seeks to address this gap by evaluating the effects of a mandatory demand-based time-of-use distribution tariff, using electricity-meter and questionnaire data in an intervention and a reference area, and a structural equation model following the theory of planned behavior. Although no effect was found of the tariff on the actual proportion of peak-hour use, there were significant effects on users’ intentions and motivations to shift electricity use to off-peak hours. The absence of effect on the proportion of peak-hour use seems explained by the facts that only a minority of consumers were aware of their tariffs, and by the (at least partially correct) beliefs that consumers used very little electricity and most of it was already used in off-peak hours. The relationships between intentions, drivers and the actual proportion of peak-hour use were stronger in the intervention area, compared to the reference area. Interestingly, this was true not only for the motivation targeted by the tariff, economic savings, but also for sustainability concerns and social norms. This suggests that effects of the tariff may partly run via other non-monetary motivators.
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| 10. |
- Behzadi, Amirmohammad, et al.
(författare)
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Smart design and control of thermal energy storage in low-temperature heating and high-temperature cooling systems : A comprehensive review
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 166, s. 112625-
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Forskningsöversikt (refereegranskat)abstract
- Thermal energy storage (TES) is recognized as a well-established technology added to the smart energy systems to support the immediate increase in energy demand, flatten the rapid supply-side changes, and reduce energy costs through an efficient and sustainable integration. On the utilization side, low-temperature heating (LTH) and high-temperature cooling (HTC) systems have grown popular because of their excellent performance in terms of energy efficiency, cost-effectiveness, and ease of integration with renewable resources. This article presents the current state-of-the-art regarding the smart design of TES integrated with LTH and HTC systems. TES is first explained in basic concepts, classification, and design possibilities. Secondly, the literature on well-known existing control approaches, strategies, and optimization methods applied to thermal energy storage is reviewed. Thirdly, the specifications, types, benefits, and drawbacks of the LTH and HTC systems from the viewpoints of supply and demand sides are discussed. Fourthly, the smart design of TES integrated with the LTH and HTC systems based on the control approach/strategy, optimization method, building type, and energy supplier is investigated to find the newest technology, ideas, and features and detect the existing gaps. The present article will provide a realistically feasible solution for having a smart storage configuration with the maximum possible energy efficiency, reliability, and cost-effectiveness for the building owners and the energy suppliers.
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| 11. |
- Benitez, Almudena, et al.
(författare)
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Recent advances in lithium-sulfur batteries using biomass-derived carbons as sulfur host
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- While biomass waste is generated in abundance, these materials and their production processes are generally environmentally friendly, low cost, non-hazardous and easily scalable. These advantages position biomass materials as excellent candidates to solve problems of environmental pollution, primarily by substitution of less sustainable counterparts. This also applies to energy storage systems such as batteries, where several components have large environmental impacts. Lithium-Sulfur batteries have, in this context, been extensively researched to cope with the growing energy needs, and are expected to foresee a growing commercialization. Specifically, advances in the use of renewable cathode materials for Li-S batteries is a field that has been widely addressed in recent years, with carbonaceous materials (C) and/or activated carbons (AC), obtained from biomass, being intensively studied. We here reviewed this field through a classification and discussion of carbonaceous materials from natural waste according to the type of biomass: (1) woody, (2) herbaceous and agricultural, (3) aquatic, (4) animal and human, and (5) contaminated and industrial biomass waste materials. In addition, all porous carbons or activated carbons used as sulfur hosts have been exhaustively evaluated in terms of origin, synthesis parameters, physical properties, and electrochemical performance in Li-S batteries. The purpose is to provide a general description of the progress in the preparation of carbons from biomass resources, examine the textural and electrochemical properties of these materials focusing on the last decade, and also to present an outlook for future research in this developing area.
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| 12. |
- Buberger, Johannes, et al.
(författare)
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Total CO 2 -equivalent life-cycle emissions from commercially available passenger cars
- 2022
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Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 159
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Tidskriftsartikel (refereegranskat)abstract
- The international passenger car market is undergoing a transition from vehicles with internal combustion engines to hybrid and fully electrified vehicles to reduce the climate impact of the transportation sector. To emphasize the importance of this needed change, this paper provides holistic comparisons of the total life-cycle greenhouse gas (GHG) emissions produced by a wide selection of commercially available passenger cars with different powertrains and energy sources. Simple analytical models are used to quantify the total life-cycle GHG emissions in terms of CO2-equivalent values relative to the vehicle curb weight and the peak motor power. The production, utilization and recycling emissions are separately quantified based on the latest reviewed emission coefficient values. In total 790 different vehicle variants are considered. The results show that Battery Electric Vehicles have the highest production emissions. For example, the additional production emissions of a Tesla Model 3 Standard Plus approximately correspond to the driving emissions of a Volkwagen Passat 2.0 TSI after 18 000km. Nonetheless, it is shown that conventional gasoline and diesel vehicles emit the highest amount of total life-cycle GHGs in comparison to vehicles powered by other available energy resources. When using green electricity, plug-in hybrid electric and fully electric vehicles can reduce the total life-cycle emission in comparison to combustion engine vehicles by 73% and 89%, respectively. A similar emission reduction is achieved by biogas powered vehicles (81%). Fuel cell vehicles approximately reduce the GHG emission to a similar extent as electric vehicles (charged with conventional electricity) when using commercially available gray hydrogen (60%).
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| 13. |
- Caron, Simon, et al.
(författare)
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A comparative analysis of opto-thermal figures of merit for high temperature solar thermal absorber coatings
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- Solar thermal absorber coatings play a key role in the thermal efficiency of receivers for applications in the field of Concentrated Solar Power (CSP). The development of stable spectral selective coatings with a high solar absorptance alpha sol and a low thermal emittance epsilon th is often desired to reduce thermal losses. However, quantitative indicators describing selectivity and the trade-off between solar absorptance and thermal emittance is seldom discussed in the literature. In this review, relevant opto-thermal figures of merit are analyzed for the comparison of reference solar thermal absorber coatings, including real and ideal coatings, both black and spectral selective. The comparison is made for a temperature ranging from 25 to 1000 degrees C and for a concentration factor ranging from 20 to 1000, based on spectral data measured at room temperature from 0.25 to 20 mu m. New figures of merit are introduced, i.e. a normalized selectivity ratio Si*, a trade-off factor Ztrade-off, a normalized solar reflectance index SRI* and a peak efficiency temperature Tpeak,opt. These metrics are derived from existing figures of merit and adapted for CSP. The set of figures of merit analyzed in this review offer a complementary perspective for the detailed characterization of any coating opto-thermal performance. For solar thermal absorber coatings, thermal efficiency eta thermal and peak efficiency temperature Tpeak,opt are respectively deemed more insightful than opto-thermal efficiency eta opt-th and maximum steady-state temperature TSST,max, when comparing the relative opto-thermal performance of two coating formulations.
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| 14. |
- Colarullo, Linda, et al.
(författare)
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Second-life EV batteries for stationary storage applications in Local Energy Communities
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- Alongside the concern for environmental sustainability, the concept of Circular Economy, a term for an economic system designed to regenerate itself, has gained momentum. Circularity finds full expression in Local Energy Communities (LEC), a newly emerging setup wherein the local energy needs of a community are met independently, through the choice of shared solutions for energy production from renewable sources. Erstwhile the use of stationary energy storage systems for self-consumption optimization, load management, peak shaving, backup power and ancillary services, would foster the value of these Local Energy Communities. In this paper, we design a techno-economic analysis to assess the impact of the usage of Second-life Batteries for increasing the energy self-independence of those communities. A cost-minimization approach with technical and economic constraints is used for the analysis and is applied to a use case of Italy. This paper assesses the benefits that a Local Energy Community can entail while considering self-consumption maximization of PV generation, load shifting and grid balancing needs, while addressing the problem of high storage costs through the exploitation of second-life electric vehicles (EV) batteries, adding an extra layer for circularity. Scenarios related to maximizing the selfconsumption of photovoltaic generation and demand side management are designed considering four different LEC technology configurations. The results confirm LEC viability, showing lower energy bills for each scenario and greater benefits coupling a solar generation system with a storage solution.
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| 15. |
- Dahal, Karna, 1984, et al.
(författare)
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Techno-economic review of alternative fuels and propulsion systems for the aviation sector
- 2021
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Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 151
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Forskningsöversikt (refereegranskat)abstract
- Substitution of conventional jet fuel with low-to zero-carbon-emitting alternative aviation fuels is vital for meeting the climate targets for aviation. It is important to understand the technical, environmental, and economic performance of alternative aviation fuels and prospective engine and propulsion technologies for future aircraft. This study reviews alternative fuels and propulsion systems, focusing on costs and technical maturity, and presents conceptual aircraft designs for different aviation fuels. The cost review includes minimum jet fuel selling price (MJFSP) for alternative aviation fuels. Direct operating cost (DOC) is estimated based on the conceptual aircraft designs and the reviewed MJFSP. The DOCs for bio-jet fuel (5.0–9.2 US cent per passenger-kilometer (¢/PAX/km)), fossil and renewable liquefied hydrogen (5.9–10.1 and 8.1–23.9 ¢/PAX/km, respectively), and electro-methane and electro-jet fuel (5.6–16.7 and 9.2–23.7 ¢/PAX/km, respectively) are higher than for conventional jet fuel (3.9–4.8 ¢/PAX/km) and liquefied natural gas (4.2–5.2 ¢/PAX/km). Overall, DOC of renewable aviation fuels is 15–500 % higher than conventional jet fuels. Among the bio-jet fuels, hydroprocessed esters and fatty acids (23–310 $/GJ) and alcohol-to-jet (4–215 $/GJ) pathways offer the lowest MJFSPs. The implementation of alternative fuels in existing aircraft engines and the design and development of appropriate propulsion systems and aircraft are challenging. The overall cost is a key factor for future implementation. Bio-jet fuel is most promising in the near term while hydrogen and electrofuels in the long term. The level of carbon tax on fossil jet fuels needed for the latter options to be competitive depend on the hydrogen production cost.
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| 16. |
- Das, Oisik, et al.
(författare)
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Natural and industrial wastes for sustainable and renewable polymer composites
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- By-products management from industrial and natural (agriculture, aviculture, and others) activities and products are critical for promoting sustainability, reducing pollution, increasing storage space, minimising landfills, reducing energy consumption, and facilitating a circular economy. One of the sustainable waste management approaches is utilising them in developing biocomposites. Biocomposites are eco-friendly materials because of their sustainability and environmental benefits that have comparable performance properties to the synthetic counterparts. Biocomposites can be developed from both renewable and industrial waste, making them both energy efficient and sustainable. Because of their low weight and high strength, biocomposite materials in applications such as automobiles can minimise fuel consumption and conserve energy. Furthermore, biocomposites in energy-based applications could lead to savings in both the economy and energy consumption. Herein, a review of biocomposites made from various wastes and their related key properties (e.g. mechanical and fire) are provided. The article systematically highlights the individual wastes/by-products from agriculture and materials processing industries for composites manufacturing in terms of their waste components (materials), modifications, resultant properties, applications and energy efficiency. Finally, a perspective for the future of biowastes and industrial wastes in polymer composites is discussed.
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| 17. |
- Drottberger, Annie, et al.
(författare)
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Urban farming with rooftop greenhouses : A systematic literature review
- 2023
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Ingår i: Renewable and Sustainable Energy Reviews. - 1364-0321 .- 1879-0690. ; 188
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Forskningsöversikt (refereegranskat)abstract
- The environmental impacts of food systems will increase in tandem with rapid urban population growth, which calls for alternative solutions, such as urban agriculture, to reach the United Nations Sustainable Development Goals. Among several urban agriculture systems, rooftop farming and its subset, rooftop greenhouses, are promising technologies. They optimize land use, increase profitability for building owners, deliver good yields per unit area, increase water use efficiency, and reduce the energy use of both greenhouse and host buildings while mitigating the urban heat island effect. A systematic literature review of the rooftop greenhouse technology was carried out to examine the benefits and challenges associated with this technology. This review was based on 45 articles, covering themes such as the impact of rooftop greenhouse technology on yields, energy use, water use, environmental impacts, and life-cycle costs; some benefits identified are the symbiotic heat, water, and CO2 exchanges between the rooftop greenhouse and its host building, and the possibility of delivering year-round production. The additional investment, operational costs, limited availability of flat roofs, and various regulations were challenges to overcome. The relevance of symbiosis between rooftop greenhouses and buildings to enhancing sustainability, and meeting the SDGs was explored. This review also outlines that rooftop greenhouses are increasing in scale, system diversity, societal acceptance and popularity among commercial operations in large cities. The future of rooftop farming lies in customizing the right technology for selected building typologies globally, where food production is fully integrated into the urban landscape.
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| 18. |
- Ek Fälth, Hanna, 1992, et al.
(författare)
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Trade-offs between aggregated and turbine-level representations of hydropower in optimization models
- 2023
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Ingår i: Renewable and Sustainable Energy Reviews. - 1879-0690 .- 1364-0321. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- To model a future power system with high shares of variable renewables, it is essential to capture the flexibility of dispatchable technologies such as hydropower. However, the representation of hydropower is often oversimplified in energy system investment models, such that the flexibility of hydropower is significantly exaggerated. This suggests the need for improved representations of hydropower that capture physical river dynamics but are computationally efficient to maintain the tractability of large models. Here, we develop a series of hydropower optimization models for a single river with various levels of techno-physical detail to evaluate options for hydropower representations in energy system investment models. All models operate hourly over a full year with perfect foresight. We explore trade-offs between accuracy and computational time involved in including features such as the river network, head-dependent power production, and discharge-dependent turbine efficiencies. We find that the level of detail significantly affects the optimal production and confirm that a simplistic hydropower representation similar to those often used in investment models significantly overestimates the flexibility of hydropower. The most detailed nonconvex model includes a full river network, head-dependency, and turbine efficiencies and is solved in just one hour on a modern desktop computer. Furthermore, we linearize this detailed model, thereby reducing computation time to one minute while featuring production dynamics substantially more similar to the full nonconvex model than a naive linear network model. These contributions pave the way for improving hydropower representations in investment models to avoid overestimating the flexibility that hydropower may provide.
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| 19. |
- El Gohary, Fouad, et al.
(författare)
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Evaluating demand charges as instruments for managing peak-demand
- 2023
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 188
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Tidskriftsartikel (refereegranskat)abstract
- Reducing peak demand in distribution grids is associated with benefits such as delayed infrastructural investments, decreased losses and a reduced risk of power deficits. One instrument aimed at reducing peak demand is the demand charge, a capacity-based component in a network tariff that intends to encourage users to reduce their peak usage. Using ten years of data from a Swedish distribution network, this study demonstrates that demand charges may be unsuitable for managing the problems they are intended to address. Two critical misalignments in the design of these demand charges are identified: 1) Demand charges are most commonly based on maximum billing demand – a given user's maximum monthly peak – whereas the problem of peak demand overwhelmingly concerns maximum system peaks in the distribution grid as a whole. The lack of coincidence between these peaks suggest that demand charges are, by design, ineffective for reducing peak demand. 2) The peaks which determine a distribution system's maximum capacity requirements are rare, seasonal and largely temperature-driven events, whereas demand charges mainly target users' habitual daily patterns, encouraging daily shifts from peak to off-peak hours. As long as the main driver of network costs, maximum system peaks, are absent in their design, demand charges will neither reflect the costs that users impose on the grid nor provide them with the correct price signals on how to best act.
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| 20. |
- El Gohary, Fouad, et al.
(författare)
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Evaluating user understanding and exposure effects of demand-based tariffs
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 155
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Tidskriftsartikel (refereegranskat)abstract
- Conventionally, demand response functions by communicating to electricity users through price signals embedded in their tariffs. These signals are intended to encourage a change in behavior, which hinges on the ability of users to understand their tariff and link it to the appropriate curtailment actions. This study focuses on demand-based tariffs, evaluating user's understanding of these tariffs and the conceptual grasp of power (rate of energy consumption) that they implicitly require. It also explores whether users exposed to these tariffs for extended periods develop a better understanding of them. Using a survey, the following points are sequentially evaluated: (1) Respondents' abilities to intuitively distinguish between energy/power (2) Their understanding of the different effects of curtailment actions under four distinct tariffs (3) Whether those subject to demand-based pricing outperform those subject to energy-based pricing. Despite a weaker conceptual understanding of power compared to energy, there were no significant differences between respondents' understanding of energy and demand-based tariffs. Comparing those subject to energy and demand-based pricing reveals that a majority were unaware of their own tariff (and hence which group they fall into), but for the minority of users who correctly identified their own tariffs, those subject to demand-based pricing outperform their energy-based counterparts. When presented with clear and instructive tariffs, respondents are largely able to deduce the consequences of curtailment actions, despite a weak conceptual understanding of power. A deeper problem is that the price signal may be entirely disregarded by an apathetic majority, reaching only an inquisitive minority.
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| 21. |
- Fan, Dongming, et al.
(författare)
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Restoration of smart grids : Current status, challenges, and opportunities
- 2021
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 143
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Forskningsöversikt (refereegranskat)abstract
- Smart grids, which constitute intelligent infrastructure in smart cities, provide reliable, energy-efficient, and high-quality power to improve the standard of living while maintaining a sustainable environment. For self-healing, restoration is considered an effective and intelligent way to ensure that parts of the system remain active and even reconfigure automatically with external failures or attacks. Restoration has recently received considerable attention from researchers and engineers. Regarding the technical route of restoration, this survey reveals some common properties and identifies the research gaps in modeling frameworks, reconfiguration technologies, and optimization approaches. It presents a summary of the challenges and opportunities in restoration of smart grids. It is expected to facilitate the researchers in the advancement of effective and intelligent restoration of smart grids.
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| 22. |
- Feng, J. -C, et al.
(författare)
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Carbon sequestration via shellfish farming : A potential negative emissions technology
- 2023
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier Ltd. - 1364-0321 .- 1879-0690. ; 171
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Tidskriftsartikel (refereegranskat)abstract
- Negative emission technologies driven by nature with less energy input, lower costs, and long carbon storage capacities are essential for meeting ambitious global carbon mitigation goals. This paper evaluates the carbon sequestration potential of bivalve shellfish farming because its sequestration process is driven by nature, and it is cost-effective and energy efficient. The carbon in shells and the carbon that enters sediments via bio-deposition are long-lived forms of carbon. Using China as a case study, a preliminary estimation suggests that the carbon sequestration efficiency and intensity of cultivated shellfishes are much higher than those of artificial forests. In China, approximately 6.23 Mt CO2-eq a−1 was fixed via net carbon sequestration during shellfish growth from 2015 to 2019. In addition, the farmed shellfishes provided 0.37 Mt of harvested protein, and approximately 37.39 Mt CO2-eq a-1 were reduced compared to the same amount of protein provided by beef, and thus, shellfish farming has the win-win benefits of carbon sequestration and high-quality food provision. More importantly, a total of 5.64 Gt CO2-eq, accounting for 17.63% of the total emissions in 2020, can be potentially sequestrated at the global scale under the world's largest farming area scenario.
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| 23. |
- Forghani, Kamran, et al.
(författare)
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A multi-period sustainable hydrogen supply chain model considering pipeline routing and carbon emissions : The case study of Oman
- 2023
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 173
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a mathematical model for a multi-period hydrogen supply chain design problem consider-ing several design features not addressed in other studies. The model is formulated as a mixed-integer program allowing the production and storage facilities to be extended over time. Pipeline and tube trailer transport modes are considered for carrying hydrogen. The model also allows finding the optimal pipeline routes and the number of transport units. The objective is to obtain an efficient supply chain design within a given time frame in a way that the demand and carbon dioxide emissions constraints are satisfied and the total cost is minimized. A computer program is developed to ease the problem-solving process. The computer program extracts the geographical information from Google Maps and solves the problem using an optimization solver. Finally, the applicability of the proposed model is demonstrated in a case study from Oman.
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| 24. |
- Gupta, Akash Som, et al.
(författare)
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Investigating the sustainability of biogas recovery systems in wastewater treatment plants- A circular bioeconomy approach
- 2024
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 199
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Tidskriftsartikel (refereegranskat)abstract
- Advanced wastewater treatment options offer a unique opportunity to recover valuable resources such as energy (biogas), nutrients, and minerals embedded in the wastewater streams. However, considerable challenges remain when designing and planning sustainable wastewater treatment systems. This study aims to evaluate the sustainability of waste-to-energy (WtE) recovery in the form of biogas in a wastewater treatment plant (WWTP). The study investigates the performance of a biogas recovery system in different scenarios and applications from 2018 to 2040, considering the city of Tbilisi in Georgia. The study results reveal a significant biogas production potential, with an average annual energy (heat and power) generation of 137 GWh when biogas is recovered from the wastewater (WW) and sewage sludge (SS). The WWTP-based WtE systems can avoid up to 38,500 tCO2eq emissions every year. The combined recovery (from WW and SS) scenario is financially feasible with a net present value of 14.88 million EUR and a levelized cost of biogas of 0.08 EUR/m³. Recovered biogas can help avoid the usage of 172.34 million m³ of natural gas worth 42.4 million EUR. Sensitivity analysis shows that the quality of wastewater, price of energy, and capital cost of the anaerobic digestion plant are the key factors in determining the economics of WtE recovery systems. This research also demonstrates the interlinkages between sustainable development goals and various benefits of resource recovery systems. This study could be helpful for decision-makers involved in planning and deploying resource recovery systems in a circular bioeconomy approach in WWTPs globally.
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| 25. |
- Gustafsson, Marcus, 1987-, et al.
(författare)
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Climate performance of liquefied biomethane with carbon dioxide utilization or storage
- 2024
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Ingår i: Renewable and sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture.
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