• Energy Research
• Energy Research close

Engineering and construction industry plays a significant role in growing Slovak economy. Investors have only limited support in vague and unclear urban- and zone-planning data and local community is often omitted from the area development planning activities. Construction plans are often subject to significant changes during the preparation and construction phase, and include imperfections between respective parts of the plans. Vast majority of the construction projects incur significant cost and time-schedule overruns, often caused by investor's unclear project definition, unbalanced contracts and adaptations of building plans during construction projects. The environment both locally and globally is heavily affected by construction activities and building operations. Overworks during building phase and suboptimal design solutions has significant negative impact on the environment during entire project lifecycle. Based on literature research, analysis of construction projects case studies, investigation of conference reports and reviews, in combination with interviews with leading specialist on Slovak market, three main factors of unsustainability in construction industry in Slovakia have been identified and both triggers and actors for positive change have been determined. The the respective problem is currently discussed on the Slovak market, however the individual topics are considered as isolated cases, without broader understanding of connections and relationships between them. The thesis offers new perspective on the topic with outlined actions to be taken.

Abstract The amount of installed solar power in Finland is increasing as a result of decreasing photovoltaic (PV) system component prices. The growth is especially noticeable in residential systems, and ways to make PV electricity a more competitive choice for Finnish residents are studied. One of these ways is to decrease the solar PV electricity production costs by decreasing the investment costs by undersizing the inverter of the PV system. The objective of undersizing is to find the optimal array-to-inverter sizing ratio (AISR) where the ratio of the economic loss from the clipped energy to the economic gain from the decreased system investment achieved by an undersized inverter is lowest. In this paper, the economically most optimal AISRs are determined for different residential array sizes, orientations, and inclinations when operating in Finnish locations and conditions. Calculations for each inverter size are carried out by using recorded Finnish meteorological data and the current Finnish PV system cost distribution, and by analyzing existing 1-s resolution production measurement data of a Finnish PV system. It is concluded that it is necessary to use 1-s resolution data as the use of 1-h resolution production data would lead to more significant undersizing caused by the power clipping occurring within an hour. The optimal AISRs presented in this study are higher than the optimal ratios reported in previous studies for locations further south than Finland. This can be explained by the northern location of Finland, where the irradiance above Standard Test Conditions (STC) is lower than in central Europe, for example. This allows more significant undersizing as less energy is clipped even at higher ratios. In the case of south-oriented arrays in a 30° installation angle, the optimal AISRs for the 10 kW, 6 kW, and 3 kW inverters were 1.6, 1.8, and 2.08, respectively. Again, the AISRs for the southwest-southeast facade installations were 1.8, 1.9, and 2.17 for the inverters under study. They do not clip the produced energy as much as rooftop systems because their production is more evenly distributed throughout the day, yet they do not achieve as low production costs either. It is pointed out that if the PV self-consumption is optimized by using PV to heat water or batteries as a storage, limitation of the PV generation might not be the correct solution.

Abstract The purpose of this paper is to investigate the influence of blending methods on the co-gasification of petroleum coke and lignite with CO 2 using a thermogravimetric system at 0.1 MPa. The weight loss curves, XRD analysis, SEM images, BET specific surface area, were investigated. It was observed that petroleum coke shows a low reactivity because of the graphitic carbon structure, low catalyst content and small specific surface area. Blending with lignite can get a high reactivity. The co-gasification reactivity was significantly influenced by blending methods. Wet grinding is much effective than dry grinding. Long grinding time made lignite show greater BET specific area. And the sample in long grinding time has more association chances between petroleum coke and AAEM species. The co-gasification reactivity increases linearly with a rise of BET specific area.

IntroductionWith the much-needed transformation from linear to more circular resource flows, it is imperative for enterprises to understand their financial prospects. Transforming towards Product-as-a-Service (PaaS) with circular elements introduces new considerations that must be addressed to ensure profitability and sustainability. However, there is a lack of comprehensive financial assessments based on empirical cases to guide companies in assessing the lucrativeness of their transformations. This paper addresses this gap by proposing a simple-to-use and flexible financial assessment model for PaaS, helping practitioners identify the conditions necessary for financial viability from both provider and user perspectives.MethodsGrounded in transdisciplinary research, this study focuses on a construction machine manufacturer's transformation from a traditional one-off sales business model to PaaS. The transformation is analysed through the development of a life cycle costing financial assessment model that addresses relevant cost drivers.ResultsUsing discounting methods, the model can help practitioners generate scenarios to identify feasible solutions for profitable PaaS setups. Additionally, the paper presents an analytical procedure to identify conditions for a financially viable PaaS. The procedure includes scenario-based analysis that accounts for systemic changes often necessary for successfully realising PaaS.DiscussionBy following the proposed procedure, along with the financial assessment model, manufacturers can streamline their financial assessments to identify necessary changes. For the analysed case company, the modelling results indicate that it must redesign its products for PaaS to outperform its previous business model.

Using a large dataset of well-level natural gas production from Wyoming, we evaluate the respective roles played by market signals and geological characteristics in natural gas supply. While we find well-level production of natural gas is primarily determined by geological characteristics, producers respond to market signals through drilling rates and locations. Using a novel fixed effects approach based on petroleum-engineering characteristics, we confirm that production decline rates tend to be larger for wells with larger peak-production rates. We also find that the price elasticity of peak production is negative, plausibly because firms drill in less productive locations as prices increase. Finally, we show that drilling is price inelastic, although the price elasticity of drilling increased significantly when new technologies began to be adopted in Wyoming. Our results indicate that the popular view that shale wells have larger decline rates than conventional wells can be at least partially explained by the pattern of falling natural gas prices.

Microalgae are recognized as a third generation feedstock for biofuel production due to their rapid growth rates and lignin-free characteristics. In this study, a lipid extracted microalgal biomass residues was used as the raw material to produce isoprene, α-pinene and β-pinene with an engineered E. coli strain. We adopted an optimal sulfuric acid hydrolysis method (1:7 ratio of solid to acid solution, 32% (w/v) concentration of sulfuric acid solution at 90 °C for 90 min) to efficiently convert holocellulose into glucose efficiently (6.37 g/L). Futhermore, we explored a novel detoxification strategy (phosphoric acid/calcium hydroxide) to remove inhibitors and notably acetic acid, furfural and 5-hydroxymethylfurfural (5-HMF) were reduced by 5.32%, different number given later 99.19% and 98.22%, respectively. Finally, the fermentation concentrations of isoprene (223.23 mg/L), α-pinene (382.21 μg/L) and β-pinene (17.4 mg/L) were achieved using the detoxified hydrolysate as the carbon source, equivalent to approximately 86.02%, 90.16% and 88.32% of those produced by the engineered E. coli strain fermented on pure glucose, respectively.

A major challenge in sustainability science is identifying targets that maximize ecosystem benefits to humanity while minimizing the risk of crossing critical system thresholds. One critical threshold is the biomass at which populations become so depleted that their population growth rates become negative—depensation. Here, we evaluate how the value of monitoring information increases as a natural resource spends more time near the critical threshold. This benefit emerges because higher monitoring precision promotes higher yield and a greater capacity to recover from overharvest. We show that precautionary buffers that trigger increased monitoring precision as resource levels decline may offer a way to minimize monitoring costs and maximize profits. In a world of finite resources, improving our understanding of the trade-off between precision in estimates of population status and the costs of mismanagement will benefit stakeholders that shoulder the burden of these economic and social costs.

AbstractWe have measured the effect of degradation on the I-V characteristics in APFO3:PCBM solar cells. The solar cell devices were subject to ambient air under simulated solar illumination. We found that the degradation resulted in a lowering of the fill factor and short circuit current while the open circuit voltage remained unchanged. In order to gain insight into what has caused the degraded I-V characteristics we have studied the active layer film using various techniques. We found clear spectral changes both in absorption and in photoinduced absorption spectroscopy correlated with increased carrier lifetimes and lowered mobility when comparing the degraded film with a pristine one. The results show a significant degradation of the active layer causing a lower fill-factor and short circuit current.