Dear Colleagues,

The usage of solar energy has steadily increased over the last decades with the large diffusion of solar thermal systems, such as domestic, commercial, and industrial appliances, which led to a considerable expansion and development of the solar industry. Among all of the established applications, solar thermal systems can generate heat for domestic hot water purposes, zone heating, cooking, water treatments (i.e., desalinization), and industrial processes (i.e., drying and maturation). At a larger scale, concentered solar collectors can enable the exploitation of solar energy to produce electricity by means of thermodynamic cycles.

Over the last few years, several innovative configurations have been developed and tested in order to improve the overall performance of solar thermal collectors. For instance, hybrid photovoltaic (PV/T) solar panels allow for the production of both thermal and electric energy by coupling PV panels with a set of cooling pipes that extract heat while reducing the temperature of the solar cells with a consequent improvement in the electric conversion efficiency.

Moreover, coupling different energy sources with solar systems can enable the deployment of integrated systems with high thermal performance, which, despite the higher initial system cost, can lead to remarkable energy savings compared with standard systems. Solar-assisted heat pump (SAHP), ground-source solar-assisted heat pumps (GSSHPs), photovoltaic solar-assisted heat pumps (PV-SAHPs) are examples of hybrid system configurations with potential high efficiencies.

Notwithstanding, outstanding challenges and research opportunities still occur in order (i) to make solar technologies cost-effective; (ii) to reduce the environmental impacts of their production, installation, and disposal processes; (iii) to allow for the integration with existing facilities and infrastructures; and (iv) to implement smart controls in order to optimise their design and management.

In this context, this Special Issue aims to gather significant research contributions on emerging technologies and applications for thermal and hybrid solar collectors. Comparisons between market-ready solar technologies and promising innovative solutions for hybrid systems, novel materials and processes, smart control, and optimisation are particularly welcome. Potential topics include, but are not limited to, the following:

• Novel technologies, materials, and manufacturing process for thermal/hybrid solar collectors
• Solar collectors and hybrid multi-source energy systems
• Emerging techniques for heat transfer and efficiency improvement
• Advanced smart control algorithms, demand side management, and energy flexibility of solar energy technologies
• Innovative numerical modelling and assessment methods for thermal\hybrid solar collectors
• Life-cycle analysis and environmental impacts of solar collectors
• Future applications of thermal/hybrid solar collectors (e.g., built environment, industrial processes, and transport)
• Thermal and electrical storage for solar applications
• Investment, markets, and policy assessments for solar thermal/hybrid collectors.

Dr. Mattia De Rosa
Dr. Francesco D’Ettorre
Prof. Martino Marini
Guest Editors

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• solar collectors
• materials
• smart control
• conversion efficiency
• storage
• hybrid renewable systems