| 1. |
- Jadim, Ramsey, et al.
(författare)
-
On Approaching Relevant Cost-Effective SustainableMaintenance of Mineral Oil-Filled Electrical Transformers
- 2021
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:12
-
Tidskriftsartikel (refereegranskat)abstract
- Fire and explosion accidents of oil-filled electrical transformers are leading to negativeimpacts, not only on the delivery of energy, but also on workplace health and safety as well asthe surrounding environment. Such accidents are still being reported, regardless of applying theregular maintenance strategy in the power plants. The purpose of this paper is to integrate asustainability perspective into the maintenance strategy. The problem addressed is: how can weapproach the relevant cost-effective sustainable maintenance for oil-filled electrical transformers?For this purpose, an empirical study in a power plant in Kuwait was introduced. The first stagewas to carry out a sustainability assessment using the ABCD procedure. In this procedure, gaps toapproach sustainability were identified and actions prioritized to close these gaps were demonstrated.Applying this procedure yielded an early fault diagnosis (EFD) model for achieving cost-effectivesustainable maintenance using a fault trend chart based on a novel numerical method. Implementingthis model resulted in an extension of the lifetime of transformers with suspected failure propagation,leading to a deferral of the replacement investment costs. The principal conclusion of this paper isthe importance of viewing the maintenance strategy of transformers from a strategic sustainabilityperspective, in order to approach relevant cost-effective sustainable maintenance.
|
|
| 2. |
- Baldi, Francesco, 1986, et al.
(författare)
-
Energy and exergy analysis of a cruise ship
- 2018
-
Ingår i: Energies. - Basel, Switzerland : MDPI. - 1996-1073. ; 11:10, s. 1-41
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, the International Maritime Organization agreed on aiming to reduce shipping’s greenhouse gas emissions by 50% with respect to 2009 levels. Meanwhile, cruise ship tourism is growing at a fast pace, making the challenge of achieving this goal even harder. The complexity of the energy system of these ships makes them of particular interest from an energy systems perspective. To illustrate this, we analyzed the energy and exergy flow rates of a cruise ship sailing in the Baltic Sea based on measurements from one year of the ship’s operations. The energy analysis allows identifying propulsion as the main energy user (46% of the total) followed by heat (27%) and electric power (27%) generation; the exergy analysis allowed instead identifying the main inefficiencies of the system: while exergy is primarily destroyed in all processes involving combustion (76% of the total), the other main causes of exergy destruction are the turbochargers, the heat recovery steam generators, the steam heaters, the preheater in the accommodation heating systems, the sea water coolers, and the electric generators; the main exergy losses take place in the exhaust gas of the engines not equipped with heat recovery devices. The application of clustering of the ship’s operations based on the concept of typical operational days suggests that the use of five typical days provides a good approximation of the yearly ship’s operations and can hence be used for the design and optimization of the energy systems of the ship.
|
|
| 3. |
- Gustavsson, Leif, 1954-, et al.
(författare)
-
Cost Optimized Building Energy Retrofit Measures and Primary Energy Savings under Different Retrofitting Materials, Economic Scenarios, and Energy Supply
- 2022
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:3
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze conventional retrofit building materials, aluminum, rock, and glass wool materials and compared such materials with wood-based materials to understand the lifecycle primary energy implications of moving from non-renewable to wood-based materials. We calculate cost optimum retrofit measures for a multi-apartment building in a lifecycle perspective, and lifecycle primary energy savings of each optimized measure. The retrofit measures consist of the thermal improvement of windows with varied frame materials, as well as extra insulation of attic floor, basement walls, and external walls with varied insulation materials. The most renewable-based heat supply is from a bioenergy-based district heating (DH) system. We use the marginal cost difference method to calculate cost-optimized retrofit measures. The net present value of energy cost savings of each measure with a varied energy performance is calculated and then compared with the calculated retrofit cost to identify the cost optimum of each measure. In a sensitivity analysis, we analyze the cost optimum retrofit measures under different economic and DH supply scenarios. The retrofit costs and primary energy savings vary somewhat between non-renewable and wood-based retrofit measures but do not influence the cost optimum levels significantly, as the economic parameters do. The lifecycle primary use of wood fiber insulation is about 76% and 80% less than for glass wool and rock wool, respectively. A small-scale DH system gives higher primary energy and cost savings compared to larger DH systems. The optimum final energy savings, in one of the economic scenarios, are close to meeting the requirements in one of the Swedish passive house standards.
|
|
| 4. |
- Haus, Sylvia, et al.
(författare)
-
Lignocellulosic Ethanol in a Greenhouse Gas Emission Reduction Obligation System : A Case Study of Swedish Sawdust Based-Ethanol Production
- 2020
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 13:5
-
Tidskriftsartikel (refereegranskat)abstract
- A greenhouse gas (GHG) emission reduction obligation system has been implemented in the Swedish road transport sector to promote the use of biofuels. For transportation fuel suppliers to fulfil this obligation, the volume of biofuel required decreases with decreasing life cycle GHG emission for the biofuel, linking lower GHG emission to higher economic value. The aim of this study was to investigate how the economic competitiveness of a Swedish emerging lignocellulosic-based ethanol production system would be influenced by the reduction obligation. The life cycle GHG emission for sawdust-based ethanol was calculated by applying the method advocated in the EU Renewable Energy Directive (RED II). The saving in GHG emissions, compared with fossil liquid transportation fuels, was 93% for a potential commercial production system in southern Sweden. This, in turn, will increase the competitiveness of sawdust-based ethanol compared to the mainly crop-based ethanol currently used in the Swedish biofuel system, which has an average GHG emission saving of 68%, and will allow for an almost 40% higher price of sawdust-based ethanol, compared to the current price of ethanol at point of import. In a future developed, large-scale market of advanced ethanol, today’s GHG emission reduction obligation system in Sweden seems to afford sufficient economic advantage to make lignocellulosic ethanol economically viable. However, in a short-term perspective, emerging lignocellulosic-based ethanol production systems are burdened with economic risks and therefore need additional economic incentives to make a market introduction possible.
|
|
| 5. |
- Jadim, Ramsey, et al.
(författare)
-
A Novel Condition Monitoring Procedure for Early Detection of Copper Corrosion Problems in Oil-Filled Electrical Transformers
- 2021
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:14
-
Tidskriftsartikel (refereegranskat)abstract
- The negative impacts of catastrophic fire and explosion accidents due to copper corrosion problems of oil-filled electrical transformers are still in the spotlight due to a lack of effective methods for early fault detection. To address this gap, a condition monitoring (CM) procedure that can detect such problems in the initial stage is proposed in this paper. The suggested CM procedure is based on identified measurable variables, which are the relevant by-products of the corrosion reaction, and utilizes an Early Fault Diagnosis (EFD) model to detect and solve the copper corrosion problems. The EFD model includes a fault trend chart that can track a fault progression during the useful life of transformers. The purpose of this paper is to verify and validate the effectiveness of the suggested CM procedure by an empirical study in a power plant. The result of applying this procedure was early detection of copper corrosion problems in two transformers with suspected copper corrosion propagation from a total of 84. The corrective action was adding an optimized amount of a passivator, an anticorrosion additive, to suppress the corrosion reaction at the correct time. The main conclusion of this study is the importance of early detection of transformer faults to avoid the negative impacts on societal, company, and individual levels.
|
|
| 6. |
- Olofsson, Martin, 1975-, et al.
(författare)
-
Seasonal variation of lipids and fatty acids of the microalgae Nannochloropsis oculata grown in outdoor large-scale photobioreactors
- 2012
-
Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 5:5, s. 1577-1592
-
Tidskriftsartikel (refereegranskat)abstract
- While focus in oil-producing microalgae is normally on nutrient deficiency, weaddressed the seasonal variations of lipid content and composition in large-scalecultivation. Lipid content, fatty acid profiles and mono- di- and triglycerides (MAGs,DAGs, and TAGs) were analyzed during May 2007–May 2009 in Nannochloropsis oculatagrown outdoors in closed vertical flat panels photobioreactors. Total lipids (TL) rangedfrom 11% of dry weight (DW) in winter to 30% of DW in autumn. 50% of the variation inTL could be explained by light and temperature. As the highest lipid content was recordedduring autumn indicating an optimal, non-linear, response to light and temperature wehypothesize that enhanced thylakoid stacking under reduced light conditions resulted inmore structural lipids, concomitantly with the increase in glycerides due to releasedphoto-oxidative stress. The relative amount of monounsaturated fatty acids (MUFA)increased during autumn. This suggested a synthesis, either of structural fatty acids asMUFA, or a relative increase of C16:1 incorporated into TAGs and DAGs. Our resultsemphasize the significant role of environmental conditions governing lipid content and composition in microalgae that have to be considered for correct estimation of algal oilyields in biodiesel production.
|
|
| 7. |
- Rahmati-Abkenar, Mahboubeh, et al.
(författare)
-
A New Dynamic Modeling Approach to Predict Microbial Methane Generation and Consumption in Marine Sediments
- 2021
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:18
-
Tidskriftsartikel (refereegranskat)abstract
- Methane, as a clean energy source and a potent greenhouse gas, is produced in marine sediments by microbes via complex biogeochemical processes associated with the mineralization of organic matter. Quantitative modeling of biogeochemical processes is a crucial way to advance the understanding of the global carbon cycle and the past, present, and future of climate change. Here, we present a new approach of dynamic transport-reaction model combined with sediment deposition. Compared to other studies, since the model does not need the methane concentration in the bottom of sediments and predicts that value, it provides us with a robust carbon budget estimation tool in the sediment. We applied the model to the Blake Ridge region (Ocean Drilling Program, Leg 164, site 997). Based on seafloor data as input, our model remarkably reproduces measured values of total organic carbon, dissolved inorganic carbon, sulfate, calcium, and magnesium concentration in pore waters and the in situ methane presented in three phases: dissolved in pore water, trapped in gas hydrate, and as free gas. Kinetically, we examined the coexistence of free gas and hydrate, and demonstrated how it might affect methane gas migration in marine sediment within the gas hydrate stability zone.
|
|
| 8. |
- Rodrigues, Luiz F., et al.
(författare)
-
High-Pressure and Automatized System for Study of Natural Gas Hydrates
- 2019
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:16
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the declining of oil reserves in the world in the coming decades, gas hydrate (GH) is seen as the great promise to supply the planet's energy demand. With this, the importance of studying the behavior of GH, several researchers have been developing different systems that allow greater truthfulness in relation to the conditions where GH is found in nature. This work describes a new system to simulate formation (precipitation) and dissociation of GH primarily at natural conditions at deep-sea, lakes, and permafrost, but also applied for artificial gas hydrates studies (pipelines, and transport of hydrocarbons, CO2, and hydrogen). This system is fully automated and unique, allowing the simultaneous work in two independent reactors, built in Hastelloy C-22, with a capacity of 1 L and 10 L, facilitating rapid analyses when compared to higher-volume systems. The system can operate using different mixtures of gases (methane, ethane, propane, carbon dioxide, nitrogen, ammonia), high pressure (up to 200 bar) with high operating safety, temperature (-30 to 200 degrees C), pH controllers, stirring system, water and gas samplers, and hyphenated system with gas chromatograph (GC) to analyze the composition of the gases formed in the GH and was projected to possibility the visualizations of experiments (quartz windows).
|
|
| 9. |
- Simonsen, Morten, et al.
(författare)
-
Model for Estimation of Fuel Consumption of Cruise Ships
- 2018
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 11:5
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a model to estimate the energy use and fuel consumption of cruise ships that sail Norwegian waters. Automatic identification system (AIS) data and technical information about cruise ships provided input to the model, including service speed, total power, and number of engines. The model was tested against real-world data obtained from a small cruise vessel and both a medium and large cruise ship. It is sensitive to speed and the corresponding engine load profile of the ship. A crucial determinate for total fuel consumption is also associated with hotel functions, which can make a large contribution to the overall energy use of cruise ships. Real-world data fits the model best when ship speed is 70-75% of service speed. With decreased or increased speed, the model tends to diverge from real-world observations. The model gives a proxy for calculation of fuel consumption associated with cruise ships that sail to Norwegian waters and can be used to estimate greenhouse gas emissions and to evaluate energy reduction strategies for cruise ships.
|
|
| 10. |
- Forslund, Helena, 1964-, et al.
(författare)
-
Toward Circular Supply Chains for Flat Glass : Challenges of Transforming to More Energy-Efficient Solutions
- 2022
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:19
-
Tidskriftsartikel (refereegranskat)abstract
- Even if flat glass is 100% recyclable, only 1% is currently handled in circular or closed-loop supply chains (CLSCs) in Sweden. This has an unnecessary environmental impact, indicating not only the potential for more energy-efficient solutions but also the challenges that need to be understood. The purpose of this article is to increase the knowledge of challenges in applying different types of more or less energy-efficient CLSCs for flat glass. Through a literature review, an overview of CLSC types, together with challenges in different areas, is provided. The CLSC types and challenges are corroborated in a flat glass context, including focus groups and expert interviews. Four CLSC types-two CLSCs based on remanufacturing, one on reconditioning, and one on reuse-are identified. A framework provides implications for both literature and practice. It contains 19 challenges-such as lack of large-scale actors, lack of material knowledge, lack of knowledge of customers' behavior, lack of promotion of flat glass CLSCs at many levels in society-in terms of both legislation and cost-and lack of business models-structured in four areas-material characteristics and quality, inefficient logistics systems, demand and supply, and means of control and costs. The least-applied CLSC includes almost every challenge and has a large upscaling potential, indicating the necessity of mitigating challenges. The framework identifies challenges not included in earlier flat glass literature. CLSC types are related to different challenge set-ups and different energy efficiency potentials, leading to expanded CLSC knowledge. One additional implication is that practitioners can identify potential CLSC types and understand their challenges from the perspective of several stakeholders. The participatory research methodology fills a methodological research gap within CLSC literature and provides important insights.
|
|
