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Microbial electrochemical technologies (METs) constitute the core of a number of emerging technologies with a high potential for treating urban wastewater due to a fascinating reaction mechanism—the electron transfer between bacteria and electrodes to transform metabolism into electrical current. In the current work, we focus on the model electroactive microorganism Geobacter sulfurreducens to explore both the design of new start-up procedures and electrochemical operations. Our chemostat-grown plug and play cells, were able to reduce the start-up period by 20-fold while enhancing chemical oxygen demand (COD) removal by more than 6-fold during this period. Moreover, a filter-press based bioreactor was successfully tested for both acetate-supplemented synthetic wastewater and real urban wastewater. This proof-of-concept pre-pilot treatment included a microbial electrolysis cell (MEC) followed in time by a microbial fuel cell (MFC) to finally generate electrical current of ca. 20 A·m−2 with a power of 10 W·m−2 while removing 42 g COD day−1·m−2. The effective removal of acetate suggests a potential use of this modular technology for treating acetogenic wastewater where Geobacter sulfurreducens outcompetes other organisms.

Offshore wind farm wakes were observed and photographed in foggy conditions at Horns Rev 2 on 25 January 2016 at 12:45 UTC. These new images show highly contrasting conditions regarding the wind speed, turbulence intensity, atmospheric stability, weather conditions and wind farm wake development as compared to the Horns Rev 1 photographs from 12 February 2008. The paper examines the atmospheric conditions from satellite images, radiosondes, lidar and wind turbine data and compares the observations to results from atmospheric meso-scale modelling and large eddy simulation. Key findings are that a humid and warm air mass was advected from the southwest over cold sea and the dew-point temperature was such that cold-water advection fog formed in a shallow layer. The flow was stably stratified and the freestream wind speed was 13 m/s at hub height, which means that most turbines produced at or near rated power. The wind direction was southwesterly and long, narrow wakes persisted several rotor diameters downwind of the wind turbines. Eventually mixing of warm air from aloft dispersed the fog in the far wake region of the wind farm.

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.