Dear Colleagues,

The last decades have demonstrated that in the sector of energy generation from renewable sources, there has been (and there is) room for technological improvements in concordance also with the Circular Economy view. As an example, the efficiency of biogas generation from food waste has improved significantly in real-scale plants, also thanks to the increased efficiency of modern selective collection strategies that can guarantee an input with few impurities. The biogas sector has also evolved towards enhanced solutions such as the upgrading of biogas to biomethane (similar to natural gas) and to the refining of the remaining off-gas in order to extract CO₂ (for technological uses). Another case is the start of a new stage of electrification, which took place during the Industrial Revolution 4.0, which means a massive saturation of various industries with electrical technologies and opens up new opportunities for using renewable energy sources in industry and smart urban infrastructure. Apart from these examples, the technological evolution concerned the whole sector of renewable energy but with different levels of penetration: in some cases, the techniques are still available only at lab-scale, like the capture of electrical current that bacteria generate through their metabolism. Prospects for the use of renewable energy sources (wind, solar energy, geothermal, tidal, ocean thermal, wave energy) stimulate interest in devices for separating the processes of energy generation and consumption. A reversible fuel cell is an electrochemical energy conversion device with the functions of both a fuel cell and an electrolyzer. Functioning sequentially in power generation mode and fuel electrolysis mode, this device functions as a running battery and, as a promising energy storage system, can serve as an economical solution to the problem of energy management. Thus, the development of energy based on renewable sources stimulates the development of distributed energy and hydrogen production technology.

A comparison should be done between renewables and traditional energy and fuels with regard to the national priorities and environmental and economic efficiency of the investment projects. A combined application solution is acceptable, with accents on the energy efficiency and sustainability of improved hydrocarbon fuels and increasing the availability and competitiveness of renewables.

In this frame, it is important to give to economic sustainability a clearer role, faced with environmental sustainability. Moreover, the social acceptance of some facilities changed year by year, making more difficult the implementation of a few options in some contexts: as an example, the landscape impact of wind energy fields plays a key role in the authorisation of new plants in some regions; moreover, the emission of ultrafine/nano particles from wood combustion sparked controversies on the related health impact. Looking at the sector on the whole, it is clear that the strategies of management of this energy sector are expected to contribute to the mitigation of climate change, but their economic sustainability and ways of financing should be analysed deeply in order to correctly orientate the future investments. Specifically, the business process has to be re-engineered. Another aspect concerns the impact of the sector evolution on the human resources management and their qualification in a sector that is more and more automated thanks to the enhancement of software and hardware. In this regard, the organization of advanced training for managers and engineers, as well as the formation of multidisciplinary teams to work in projects of technological modernization and creation of complex, smart energy systems of the future, becomes a fundamental task.

The present issue will focus on all the above-mentioned aspects and is open both to specialised works and to interdisciplinary articles.

Prof. Dr. Elena Cristina Rada
Prof. Dr. Elena Romenovna Magaril
Dr. Larisa Ivascu
Guest Editors

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• Biomass to energy
• Climate change
• Circular economy
• Economic sustainability
• Environmental impact
• Environmental sustainability
• Geothermal energy
• Hydropower
• Innovation
• Advances in fuel cell technology
• Hydrogen production
• Gas electrolysis
• Environmental monitoring systems
• Management
• Options
• Photovoltaics
• Social impact
• Solar thermal
• Renewable energy
• Strategies
• Waste to energy
• Wind energy
• Electrification
• Smart energy systems and cities
• Educational issues