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Photovoltaic (PV) technology allows large-scale investments in a renewable power-generating system at a competitive levelized cost of electricity (LCOE) and with a low environmental impact. Large-scale PV installations operate in a highly competitive market environment where even small performance losses have a high impact on profit margins. Therefore, operation at maximum performance is the key for long-term profitability. This can be achieved by advanced performance monitoring and instant or gradual failure detection methodologies. We present in this paper a combined approach on model-based fault detection by means of physical and statistical models and failure diagnosis based on physics of failure. Both approaches contribute to optimized PV plant operation and maintenance based on typically available supervisory control and data acquisition (SCADA) data. The failure detection and diagnosis capabilities were demonstrated in a case study based on six years of SCADA data from a PV plant in Slovenia. In this case study, underperforming values of the inverters of the PV plant were reliably detected and possible root causes were identified. Our work has led us to conclude that the combined approach can contribute to an efficient and long-term operation of photovoltaic power plants with a maximum energy yield and can be applied to the monitoring of photovoltaic plants.

Electrochemical impedance spectroscopy is an important tool for fuel-cell analysis and monitoring. This study focuses on the low-AC frequencies (2–0.1 Hz) to show that the thickness of the catalyst layer significantly influences the overall resistance of the cell. By combining known models, a new equivalent circuit model was generated. The new model is able to simulate the impedance signal in the complete frequency spectrum of 105–10−2 Hz, usually used in experimental work on polymer electrolyte fuel cells (PEMFCs). The model was compared with experimental data and to an older model from the literature for verification. The electrochemical impedance spectra recorded on different MEAs with cathode catalyst layer thicknesses of approx. 5 and 12 µm show the appearance of a third semicircle in the low-frequency region that scales with current density. It has been shown that the ohmic resistance contribution (Rmt) of this third semicircle increases with the catalyst layer’s thickness. Furthermore, the electrolyte resistance is shown to decrease with increasing catalyst-layer thickness. The cause of this phenomenon was identified to be increased water retention by thicker catalyst layers.

In light of global warming and the energy turn, sector coupling has gained increasing interest in recent years, from both the scientific community and politics. In the following article it is hypothesized that efficient multifaceted sector coupling solutions depend on detailed spatial and temporal characteristics of energy demand and supply. Hence, spatiotemporal modelling is used as a methodology of integrated spatial and energy planning, in order to determine favourable sector coupling strategies at the local level. A case study evaluation was carried out for both central and decentral renewable energy sources. Considering the high temporal resolutions of energy demand and supply, the results revealed a feasible operation of a district heating network in the central areas of the case study municipalities. Additionally, building integrated solar energy technologies are capable of providing large amount of excess energy that could serve other demand sectors, such as the mobility sector, or could be used for Power-to-X solutions. It is suggested that sector coupling strategies require spatial considerations and high temporal comparisons, in order to be reasonably integrated in spatial and urban planning.

To address the huge market of renovation of multi-apartment buildings, minimal-invasive decentral serial-renovation solutions are required. One major challenge in the design of decentral heat pumps is to find the optimal balance between, on one hand, compactness and pleasant design, and on the other hand, efficiency and minimal sound emissions. A comprehensive holistic design and optimization process for the development of decentral heat pumps, from the component level, to the system level, and up to the building level, is developed. A novel façade-integrated speed-controlled exhaust air to supply air heat pump combined with a mechanical ventilation system with heat recovery and recirculation air was developed and simulated in a reference flat. Compared to a traditional supply air heat pump without recirculation, it shows only slight performance improvement, but allows significantly better thermal comfort and control, independently from the hygienic air flow rate and from the heating and cooling loads. Detailed measurement and simulation results are presented for several functional models with heating power of around 1 kW up to 2.5 kW. The design was optimized by means of CFD simulations to allow for low pressure drop, homogeneous flow, and low sound emissions. Moreover, mock-ups of innovative façade-integrated heat pump outdoor units are presented.

A two-step numerical concept was developed for modelling combustion and predicting nitrogen oxide emissions. The model was validated by the Sandia flame D experiment and with measurement data from burners on industrial furnaces. In this paper, the developed model was implemented to evaluate the influence of hydrogen blending with natural gas up to 40 vol.% on an industrial burner with oxidizer temperatures at 300 K and 813 K to assess the performance of the burner without altering the power output of the burner. An experimental test facility is under construction, and the feasibility of using this industrial burner on the test facility with different fuel mixtures was analyzed. Temperature, flow field, and emission characteristics were investigated. Using 40 vol.% hydrogen with natural gas resulted in a decrease of 14.82% in CO2 emissions and an increase of in 16.1% NO emissions when combusted with air at 300 K. The temperature profile indicated that the burner produces a symmetrical flame profile with preheated air and an asymmetrical flame profile with ambient air.

Environmental sustainability remains a critical challenge in the face of global economic development. This study explored the complex interactions among renewable energy consumption, urbanization, trade openness, and economic development, focusing on their effects on environmental quality in 34 high-income European and Asian economies from 1970 to 2022. Using linear Bayesian regression and the Vector Error Correction Model (VECM), the analysis examined short- and long-term impacts to uncover nuanced relationships. Results demonstrated that economic development contributed to environmental degradation over the long term while mitigating it in the short term. Renewable energy consumption supported economic growth but showed limited efficacy in reducing ecological footprints across different time frames. Urbanization and trade openness emerged as significant drivers of long-term environmental degradation, emphasizing the need for targeted policy interventions. This study examined the link among economic progress and environmental sustainability, and identified key areas for improvement in urban planning, renewable energy, and trade policies. The findings provide a framework for policymakers to balance development with environmental preservation.

To realise the energy transition, every renewable source shall at least partially contribute to the demand–supply balancing, including customer-owned controllable loads and energy sources. Their commonly small size and spatial occurrence suggests addressing volatility issues locally, using local flexibilities to mitigate their impact. This calls for simple and effective signalling that enables interaction among local stakeholders, including local producers and customers. According interfaces and information formats appear to not yet exist. In this article, we propose a traffic-light-like system that enables the local grid operator to trigger situation-aware customer behaviour, supporting grid stability when needed and, in return, allowing customers to fully exploit temporary grid capacity when no safety or stability issues persist. The applied intuitive deduction method based on existing coordination mechanisms and objectives indicates, without proof, that the proposed granular traffic light system can enable the distribution grid flexibility required to facilitate more renewable energy being produced and inserted by local customers, to relieve grid levels above from transporting and equalising volatile energy shares, and to improve the economics of distributed renewable energy sources.

Steel production is one of the biggest emitters of greenhouse gas in the industrial sector with about 8% of total global CO2 emissions. Although the majority of emissions can be attributed to primary steel production, there is also potential for reducing CO2 emissions in downstream steel processing. Large industrial furnaces, which are necessary for heating steel, are currently primarily fired with natural gas and by-product gases from primary steel production, offering great potential for heat recovery measures from exhaust gases. However, switching to alternative climate-neutral fuels could change this potential and thus jeopardize the economic viability of heat recovery measures. In the present work, it was therefore examined to what extent a change in energy sources in industrial furnaces affects the potential use of heat recovery in steel processing. For this purpose, an optimization model was used that takes into account heat recovery by means of direct heat transfer, heat pumps and heat distribution systems. Potential future changes in energy supply for industrial furnaces were examined using different storylines. Two different energy price scenarios were also considered to address uncertain developments in energy markets. The results show that heat recovery is a cost-effective and definitely recommendable measure. Switching to alternative fuels has little impact on the use of heat recovery. Electrification and thus the elimination of flue gas, on the other hand, greatly reduces the potential for heat recovery.