This paper introduces a bilevel programming approach to electricity tariff optimization for the purpose of demand response management (DRM) in smart grids. In the multi-follower Stackelberg game ...model, the leader is the profit-maximizing electricity retailer, who must set a time-of-use variable energy tariff in the grid. Followers correspond to groups of prosumers (simultaneous producers and consumers of the electricity. They response to the observed tariff, schedule controllable loads and determine the charging/discharging policy of their batteries to minimize the cost of electricity and to maximize the utility at the same time. A bilevel programming formulation of the problem is defined, and its fundamental properties are proven. The primal-dual reformulation is proposed in this paper to convert the bilevel optimization problem into a single-level quadratically constrained quadratic program (QCQP), and a successive linear programming (SLP) algorithm is applied to solve it. It is demonstrated in computational experiments that the proposed approach outperforms typical earlier methods based on the Karush–Kuhn–Tucker (KKT) reformulation regarding both solution quality and computational efficiency on practically relevant problem sizes. Besides, it also offers more flexible modeling capabilities.
This study reports on the performance of delta-shaped obstacles in a solar water heating system (SWHS) by means of experimental analysis and optimization. The influence of different parameter ...combinations such as Reynolds number (200, 600, 1000, 1400, 1800), pitch ratio (0.5, 1, 1.5), blockage ratio (0.15, 0.20, 0.25), and angle of attack (45°) on Nusselt number, friction factor and thermo-hydraulic performance of SWHS were analyzed. For the combination of Reynolds number = 1800 and pitch ratio = 0.5, the Nusselt number remained highest for 0.25 of blockage ratio, whereas the friction factor remained lowest for a blockage ratio of 0.15. The maximum thermo-hydraulic efficiency was achieved using Reynolds number = 200, pitch ratio = 0.5, and blockage ratio = 0.20. The obtained results were intensely dependent on parameter combinations without any pronounced trend. Therefore, criteria importance through inter-criteria correlation (CRITIC) and complex proportional assessment (COPRAS) approach was implemented to find optimal design alternative. The results of the hybrid CRITIC-COPRAS approach showed that the combination of Reynolds number = 1800, pitch ratio = 0.5, blockage ratio = 0.20, and angle of attack = 45° is the best alternative for maximum thermal enhancement in SWHS. The sensitivity analysis proved the robustness of the results that the first-ranked alternative is the most dominant in all scenarios.
•Solar water heating system (SWHS) design selection based on geometric/flow combinations.•Selection criteria include Nusselt number, friction factor, and thermo-hydraulic efficiency.•Integrated CRITIC/COPRAS methodology proposed to identify the optimal SWHS alternative.•Effectiveness and robustness of the proposed methodology is proved by sensitivity analysis.
Display omitted
•Sustainable land use management is problematic, even in national parks.•Effectiveness of nature conservation is under the influence of agriculture.•Agricultural subsidies have ...contradictory effects on protected areas.•CAP reform is necessary to promote well-functioning cross-sectoral cooperation.•Farmers' environmental awareness needs to be improved.
National parks and other forms of protection ensure the natural values in the European Union. However, a significant part of protected areas is under agricultural cultivation, and the two sectors have been kind of opponents to each other for a long time. In the last 50 years, because of various socio-economic changes, the European and Hungarian agricultural policies had opposing concepts and goals, even related to protected areas. In our work, we identified the policy and institutional changes, examined their effects, and the conflicts that accompanied them by exploring the area of Kiskunság National Park (KNP) in Hungary. Based on literature and document review, in-depth interviews, GIS, and statistical analysis, we present the main reasons and symptoms of the two sectors' counter-interest. We found that farming objectives and agricultural subsidies have an essential influence on nature conservation. In contrast, the KNP as an institution has less and less control over the landscape management of conservation areas. The historical turning points have fundamental impacts on the behavior of local actors. The changing macro-conditions cause unbalanced relations between nature conservation and agriculture, which could endanger valuable close-to-nature landscapes. We conclude that the coexistence of agricultural production and nature conservation can be improved, but it will require the equal treatment and independence of sectors, comprehensive policy coordination, complex spatial planning, and paradigmatic change in support to agricultural communities and conservationists. The linkages between these two policy areas will increasingly determine sustainable land use management in the future, thus protecting natural values not just in Hungary, but in the EU and other countries too.
This article investigates the effect of an additional thin dielectric layer on the top of the metasurface (MS), on the transmission of electromagnetic waves in the terahertz band. For this purpose, ...the split ring resonator-based MS was designed and analyzed in the terahertz band. The influence of permittivity, film thickness, and suspension height on
transmission coefficient characteristics was studied. For this purpose, a numerical model was created and solved using the finite element method. The conducted study can be helpful in three cases. First, changing the suspension height of the dielectric layer may allow tunable MSs using MEMS structures. Also, this research can be used to determine the effect of applying an additional layer of protection when using the MS as a sensor to test substances that can damage it. In addition, there is an opportunity to study the dielectric properties of thin films using the proposed MS.
Different modeling and solution approaches to electricity tariff optimization for demand response management have received considerable attention recently. Yet, there are hardly any results available ...on the computational complexity of these problems. The clarification of the complexity status is crucial to understand for which models an efficient, polynomial algorithm, or a closed-form analytical solution can be expected, and when the application of heuristics delivering suboptimal solutions or time consuming search procedures is justifiable. In this letter, we define the Simple Multi-Period Energy Tariff Optimization Problem (SMETOP) and prove its NP-hardness. The result naturally applies to many models in the literature that generalize SMETOP, and whose complexity status has been unknown to date.
Observing reactions and responses to climate change worldwide, we think climate policies cannot exert their impact sufficiently. Consequently, studying the climate policy paradigms (CPPs) shaped by ...the dominant environmental ideas and climate objectives is essential. This paper analyses the CPPs in the Visegrad Countries (Czech Republic, Hungary, Poland, Slovakia) (V4). We investigated the strategic background and implementation related to climate policies by studying the CPPs' different levels. Our research comprises two components:
1. Analysis of national climate strategies and plans (n = 9) to reveal documented policy goals.
2. In-depth interviews (n = 58) to explore the implementation of policy goals and strategic principles. According to our results, the V4's climate strategy documents (CSDs) align with global climate policy efforts and follow EU standards. However, we have found contradictions between the policy goals and their implementation. Our findings show that CSDs are only partial indicators of the CPPs, and all four countries have gaps between ideas and the realization of climate actions. One of the main reasons is that V4 prioritizes national economic interest and energy security. Consequently, the climate policy paradigm takes a back seat. The other inhibiting factors are the lack of social will and the shortcomings of climate governance.
Display omitted
•The V4 has taken significant steps in climate policy over the past decade.•Policy implementation does not fully match climate policy goals.•Obstacles are economic interest, lack of social will, and institutional failures.•Poland’s coal reliance drives pronounced policy gaps.•Climate strategies serve as superficial indicators of climate policy paradigms.
Nature-based tourism has become increasingly popular in recent years. However, the COVID-19 pandemic dramatically impacted the tourism sector and triggered contradictory processes, even in protected ...areas. This phenomenon opens up new opportunities for nature-based tourism from the perspective of rural development. In this study, we assess the relations between tourism and nature conservation and examine the characteristics of practical cooperation in three Hungarian national parks. Based on in-depth interviews (n = 76), document review, and analysis of tourism-related data, our research proves that nature-based tourism could play an essential role in rural development, but this is far from being fulfilled. None of the sectors have been able to impact the comprehensive development of the rural areas concerned. We conclude that sectoral partnership is inadequate, and there is no effective policy coordination. There is a lack of multiday tourism programs, and the currently available tourism infrastructure is insufficient. Initiatives such as the national park product trademark exist but are not well managed, so they do not have a meaningful impact. The results point out that cross-sector collaboration must be strengthened after the epidemic to provide a basis for policy coordination and joint planning.
Solar water heater (SWH) is important and low-cost technology for transforming solar radiation into heat energy that is utilized for commercial and industrial purposes. However, due to different ...advantages, this technology still suffers from poor thermal efficiency and thermal losses from the collector. The various reasons responsible for the poor heat transfer rate of SWH are heat losses from the system and different geometrical shapes of hindrance promoters. The researcher is working on various innovative methods to ameliorate the effectiveness of solar water heating systems (SWHS) by using various heat enhancement methods. The solar thermal conversion efficiency is found to be 70% as compared to solar electrical direct conversion system, which is around 17%. The different heat enhancement techniques, like twisted tape turbulator and their shape, etc., play a very remarkable role in ameliorating the effectiveness of SWHS. This review work abridges the previous research work with different heat enhancement techniques, including the coating effect of pipes, collector design, use of PCM, and different geometrical shapes of turbulence promoters. The twisted tape provides better η as compared to other heat enhancement techniques.
Vivianite (Fe3(PO4)2·8H2O) may precipitate in anoxic lake sediments affecting the porewater orthophosphate concentration, and thereby the trophic status of lakes. We have investigated changes in lake ...diagenesis of Fe and P (1969–2009), with particular attention focused on vivianite formation with sediment depth (0–20cm) in an iron–silica–carbon rich lake sediment (Ørnsø, Denmark). Porewaters were supersaturated for vivianite by two to five orders of magnitude (upper 10cm) with porewater phosphate concentrations ranging between 0.69 and 10μmoll−1, in winter, and summer concentrations ranging between 9.8 and 40μmoll−1. Significant formation of vivianite was confirmed by X-ray diffraction while scanning electron microscopy and electron dispersive X-ray spectroscopy indicated an increase in vivianite crystal size with depth (~20 to ~70μm across). Variations in elemental composition of vivianite crystals in relation to at.% P and Fe were especially seen going from 9.5cm to 24.5cm. The total sediment Fe pool was very large ~3000μmolg−1 and total P increased from 200μmolg−1 to 400μmolg−1 descending down the sediment profile. Differential extraction experiments of P release at pH3 estimated that vivianite amounts to between 3 and 5% of the total Fe pool. The total P burial fluxes estimate that ~38μmolcm−2yr−1 or ~26% of sedimentary P in the lower sediments is sequestered as vivianite. There are seasonal variations in the porewater composition with lower Fe, orthophosphate and higher sulfate concentrations during winter (5°C), than during summer (15°C). This suggests that temperature modulates the rate of organic matter degradation which in turns affects the rate of Fe(III) phase reduction, release of phosphate, and thereby the porewater Fe2+ and orthophosphate concentrations and hence vivianite formation. This work highlights the role vivianite can play for P retention in a Si–Fe–C rich lake sediment.
•Investigation of changes in lake diagenesis of Fe and P (1969–2009) focused on vivianite formation.•Differential extraction experiments for the estimation of vivianite•Temperature modulates the rate of organic matter degradation and eventual vivianite formation.•Work highlights the role vivianite can play for P retention in a Si–Fe–C rich lake sediment.
PDF
