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This paper presents a finite control-set model predictive control (FCS-MPC) based technique to reduce the switching loss and frequency of the on-grid PV inverter by incorporating a switching frequency term in the cost function of the model predictive control (MPC). In the proposed MPC, the control objectives (current and switching frequency) select an optimal switching state for the inverter by minimizing a predefined cost function. The two control objectives are combined with a weighting factor. A trade-off between the switching frequency (average) and total harmonic distortion (THD) of the current was utilized to determine the value of the weighting factor. The switching, conduction, and harmonic losses were determined at the selected value of the weighting factor for both the proposed and conventional FCS-MPC and compared. The system was simulated in MATLAB/Simulink, and a small-scale hardware prototype was built to realize the system and verify the proposal. Considering only 0.25% more current THD, the switching frequency and loss per phase were reduced by 20.62% and 19.78%, respectively. The instantaneous overall power loss was also reduced by 2% due to the addition of a switching frequency term in the cost function which ensures a satisfactory empirical result for an on-grid PV inverter.

Offshore grids can play key roles in the transition of energy systems toward sustainability. Although they require extensive infrastructure investments, they allow for the exploitation of additional resources and may be important in providing for part of the increasing electricity demands driven by sector coupling. This paper quantifies the socioeconomic value of offshore grids and identifies their major drivers, performing energy system optimization in a model application of the northern–central European energy system and the North Sea offshore grid towards 2050. The increasing wake loss with the sizes of hub-connected wind farms is integrated in the modeling. We find that without sector coupling no offshore grid may develop, and that the higher the level of sector coupling, the higher the value of offshore grids. Therefore, it can be strongly stated that offshore grid infrastructure development should not be discussed as a separate political topic, but seen in connection to sector coupling.

Industrial exhausted heat can be used as the heat source of central heating for higher energy efficiency. To recover more industrial exhausted heat, a new low-temperature central heating system integrated with industrial exhausted heat using distributed electric compression heat pumps is put forward and analyzed from the aspect of thermodynamics and economics. The roles played by the distributed electric compression heat pumps in improving both thermal performance and financial benefit of the central heating system integrated with industrial exhausted heat are greater than those by the centralized electric compression heat pumps. The proposed low-temperature central heating system has higher energy efficiency, better financial benefit, and longer economical distance of transmitting exhausted heat, and thus, its configuration is optimal. For the proposed low-temperature central heating system, the annual coefficient of performance, annual product exergy efficiency, heating cost, and payback period are about 22.2, 59.4%, 42.83 ¥/GJ, and 6.2 years, respectively, when the distance of transmitting exhausted heat and the price of exhausted heat are 15 km and 15 ¥/GJ, respectively. The economical distance of transmitting exhausted heat of the proposed low-temperature central heating system could approach 25.1 km.

The aim of this study is to identify non-technological critical success factors (CSFs) that influence the different phases of the project life cycle for the deployment of centralized biogas projects; as there is a knowledge gap in this area. This was performed by applying a longitudinal process analysis approach and an analytical framework based on findings from previous studies. Data were collected through extensive document collection and analysis, combined with in-depth semi-structured interviews. The study resulted in the identification of a total of 30 non-technological critical success factors in the case of Solrød Biogas. These were subsequently linked to one of the different phases of the project lifecycle (conceptualization phase, planning phase, execution phase) or categorized as general CSFs. We hope that the findings in this study can help ensure better management of biogas projects and enhance the capabilities of governmental bodies in supporting projects in the future, so a higher rate of centralized biogas projects is successfully implemented both in Denmark and other countries

The household sector in Poland consumes more than 25% of final energy. At the same time, residents reported dissatisfaction with the thermal conditions during the summer months. This paper details the search for passive and energy-efficient solutions to improve thermal comfort in Polish dwellings. A five-story, multi-family building was selected for this research. Analyses were conducted in apartments located on the top two floors using EnergyPlus (for thermal calculations) and CONTAM (for air exchange calculations) simulation programs for current and future climatic conditions. The stochastic behavior of people when opening windows and automatically controlled systems supplying external air to the building was considered. Airing the apartments by opening windows increased the heating demand but reduced the number of thermal discomfort hours by over 90%. The degree of airing by opening windows depends on residents opening their windows; therefore, a mechanical supply of external air controlled by both internal and external temperatures was proposed and tested.

Power-to-X is an upcoming sector-coupling technology that can play a role in the decarbonisation of energy systems. The aim of this study was to widen the current knowledge of strengths, weaknesses, opportunities, and threats (SWOT) of this innovative technology in the Danish context by utilizing the analytic hierarchy process (AHP) to evaluate and compare perception of academic and industrial experts. The results of this analysis indicate that the external factors such as current policy framework are more important than the internal technology related factors. Further, positive factors predominate negative ones, with academic experts indicating strengths as the most important category and practitioners’ opportunities. All experts consider the country being a P2X knowledge hub as one of the most important factors, and in the given context of the Danish energy system, wind developments and Danish industrial environment, seizing this opportunity could be the biggest enabler for P2X success.

Model predictive control based wave power extraction algorithms have been developed and found promising for wave energy converters. Although mostly proven by simulation studies, model predictive control based algorithms have shown to outperform classical wave power extraction algorithms such as linear damping and reactive control. Prediction models and objective functions have, however, often been simplified a lot by for example, excluding power take-off system losses. Furthermore, discrete fluid power forces systems has never been validated experimentally in published research. In this paper a model predictive control based wave power extraction algorithm is designed for a discrete fluid power power take-off system. The loss models included in the objective function are based on physical models of the losses associated with discrete force shifts and throttling. The developed wave power extraction algorithm directly includes the quantized force output and the losses models of the discrete fluid power system. The experimental validation of the wave power extraction algorithm developed in the paper shown an increase of 14.6% in yearly harvested energy when compared to a reactive control algorithm.