New Insights into Hybrid Renewable Energy Systems in Buildings
1
Nuclear Department, ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development), 40121 Bologna, Italy
2
Faculty of Civil and Industrial Engineering, Sapienza University of Rome, 00184 Rome, Italy
3
Department of Electrical and Energy Engineering, Sapienza University of Rome, 00184 Rome, Italy
*
Author to whom correspondence should be addressed.
Energies 2026, 19(3), 767; https://doi.org/10.3390/en19030767
Submission received: 23 January 2026
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Accepted: 30 January 2026
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Published: 2 February 2026
(This article belongs to the Special Issue New Insights into Hybrid Renewable Energy Systems in Buildings)
This book collects papers published in the Special Issue of Energies on “New Insights into Hybrid Renewable Energy Systems in Buildings”.
The built environment is crucial in the global energy transition, accounting for a significant share of worldwide energy consumption and greenhouse gas emissions. The increasing deployment of renewable energy technologies in buildings is widely acknowledged as a key strategy to reduce energy consumption and environmental impact and support decarbonization goals. The complexity of energy management and energy systems in buildings calls for attention towards integrated, hybrid approaches.
Hybrid, renewable energy systems in buildings combine multiple energy sources, storage technologies, and control approaches to bring out flexibility, reliability, and performance. The successful integration of diverse generation and storage technologies, possibly including electric mobility, demands appropriate design and control. The interaction between users, buildings, and the wider energy system makes it more challenging.
Topics of interest for the call included, but were not limited, to the following: integration of diverse renewable-energy-generation technologies in the building context; innovative control strategies for optimizing the performance of hybrid energy systems; integration and management of energy storage systems within building structures; synergy between electrical mobility solutions and buildings; users’ behavior and influence on the design and operation of buildings; advances in energy storage and conversion technologies; and environmental impact and sustainability of solutions.
Recent scientific research has dealt with the integration of multiple, renewable energy sources (e.g., solar, wind, and geothermal) coupled with energy storage technologies and smart energy management systems (including electrical mobility) to increase effectiveness and flexibility while mitigating limitations of individual technologies (e.g., intermittency). The main finding in the literature is that the promising trend is towards hybrid systems (hybrid renewable energy systems, HRES), consistently outperforming individual technologies in terms of efficiency, resilience, and sustainability [1,2] towards the concept of “multi-energy building” [3].
However, notwithstanding important advances, the path is not straightforward and several challenges remain. Persistent research gaps are inconsistent application of life-cycle assessment and techno-economic indicators, limited empirical data for commercial and high-rise buildings, and insufficient attention to policy mechanisms that drive adoption [1]. Persistent challenges are real-time control strategies for multi-objective optimization, uncertainty in renewable generation, dynamic load, system interoperability, limited empirical data from real installations, economic feasibility, lack of standard evaluation methods, and policy and institutional barriers [2,4,5].
The Special Issue features eight papers, with six of them being research articles and two of them being reviews. The contributions of this Special Issue address some of these challenges from multiple points of view: advanced control strategies (contribution 1–2, and 7–8), modeling (contribution 2–3), forecasting (contribution 3–4), design optimization (contribution 2, 5–7), and applications of artificial intelligence (contribution 7).
Hedayat et al. (contribution 1) propose a physics-informed reinforcement learning framework for HVAC optimization that embeds thermodynamic constraints directly into the control policy, tested on a multi-zone thermal model, achieving significant reductions in energy consumption and peak demand while maintaining thermal comfort.
Kapsalis et al. (contribution 2) propose a multi-scale predictive and optimization framework to optimize behind-the-meter energy storage strategies alongside rooftop photovoltaic penetration in European urban contexts, accounting for prosumer behavior and regulatory and economic scenarios.
Chicherin (contribution 3) develops a methodology for hydraulic balancing in low-temperature district heating systems, to improve operational efficiency and thermal comfort in buildings, supporting the implementation of fourth-generation district heating.
Abdi et al. (contribution 4) investigate sky temperature forecasting using measured climatic data and artificial neural networks to improve the accuracy of building energy performance assessments, improving modeling of radiative heat exchange.
Papadopoulos et al. (contribution 5) present multi-objective optimization of insulation thickness in residential buildings considering on-site renewable energy generation.
Beblek et al. (contribution 6) present a user-centric digital platform for optimizing heating system operation based on perceived thermal comfort, integrating behavioral feedback into energy management, to reduce energy consumption, maintaining comfort.
Filippova et al. (contribution 7) review advances in artificial intelligence and digital twin for bioclimatic building design, highlighting their role in improving sustainability and energy efficiency, discussing how data-driven methods can support climate-responsive design and decision-making across the building lifecycle.
Michailidis et al. (contribution 8) provide a comprehensive review of reinforcement learning applications to optimize renewable energy utilization in buildings, summarizing control architectures, algorithms, and use cases, outlining opportunities and challenges.
Among research articles, Papadopoulos et al. is a feature paper. Among reviews, Michailidis et al. is the Editor’s Choice. The geographical distribution of authors is as follows: Greece (11), Germany (5), Italy (4), Djibouti (2), Belgium (1), and France (1).
We believe that the Special Issue has contributed to disseminating emerging innovations to address some of the relevant challenges in the implementation of hybrid renewable energy systems for a transition towards sustainability. We are thankful for the opportunity to be guest editors and we thank the Staff and Reviewers for their commitment and effort.
Author Contributions
All authors have read and agreed to the published version of the manuscript.
Conflicts of Interest
The authors declare no conflict of interest.
List of Contributions
- Hedayat, S.; Ziarati, T.; Manganelli, M. A Physics-Informed Reinforcement Learning Framework for HVAC Optimization: Thermodynamically-Constrained Deep Deterministic Policy Gradients with Simulation-Based Validation. Energies 2025, 18, 6310. https://doi.org/10.3390/en18236310.
- Kapsalis, V.; Mitsopoulos, G.; Stamatakis, D.; Tolis, A. Multi-Scale Predictive Modeling of RTPV Penetration in EU Urban Contexts and Energy Storage Optimization. Energies 2025, 18, 5715. https://doi.org/10.3390/en18215715.
- Chicherin, S. Hydraulic Balancing of District Heating Systems and Improving Thermal Comfort in Buildings. Energies 2025, 18, 1259. https://doi.org/10.3390/en18051259.
- Abdi, H.; Idris, A.; Tran Le, A. Sky Temperature Forecasting in Djibouti: An Integrated Approach Using Measured Climate Data and Artificial Neural Networks. Energies 2024, 17, 5791. https://doi.org/10.3390/en17225791.
- Papadopoulos, A.; Polychronakis, K.; Kyriaki, E.; Giama, E. Multi-Objective Optimization of Insulation Thickness with Respect to On-Site RES Generation in Residential Buildings. Energies 2024, 17, 5609. https://doi.org/10.3390/en17225609.
- Beblek, A.; Sehr, F.; Grinewitschus, V.; Baedeker, C.; Wolber, A. Development and Application of a Platform for Optimising Heating System Operation Based on the Building User’s Temperature Perception. Energies 2024, 17, 4468. https://doi.org/10.3390/en17174468.
- Filippova, E.; Hedayat, S.; Ziarati, T.; Manganelli, M. Artificial Intelligence and Digital Twins for Bioclimatic Building Design: Innovations in Sustainability and Efficiency. Energies 2025, 18, 5230. https://doi.org/10.3390/en18195230.
- Michailidis, P.; Michailidis, I.; Kosmatopoulos, E. Reinforcement Learning for Optimizing Renewable Energy Utilization in Buildings: A Review on Applications and Innovations. Energies 2025, 18, 1724. https://doi.org/10.3390/en18071724.
References
- Kaldeh, S.N.; Yousefi, H.; Noorollahi, Y.; Abdoos, M. Integration of renewable sources in buildings: A review of energy savings, feasibility, and challenges. Energy Rep. 2025, 14, 3905–3934. [Google Scholar] [CrossRef]
- Shahid, M.N.; Shahid, M.U.; Irfan, M. Advances in Building Energy Management: A Comprehensive Review. Buildings 2025, 15, 4237. [Google Scholar] [CrossRef]
- Canale, L.; Di Fazio, A.R.; Russo, M.; Frattolillo, A.; Dell’Isola, M. An Overview on Functional Integration of Hybrid Renewable Energy Systems in Multi-Energy Buildings. Energies 2021, 14, 1078. [Google Scholar] [CrossRef]
- Lipu, M.H.; Rahman, M.A.; Islam, Z.U.; Rahman, T.; Rahman, S.; Meraj, S.T.; Hossain, Y.; Mansor, M. Review of energy storage integration in off-grid and grid-connected hybrid renewable energy systems: Structures, optimizations, challenges and opportunities. J. Energy Storage 2025, 122, 116629. [Google Scholar] [CrossRef]
- Wang, S.; Li, Y.; Cui, Y.; Yu, J.; Zhou, C.; Ametefe, D.S.; John, D.; Darboe, T. Integrating renewable energy into building energy systems: A systematic review of strategies, barriers, and policy interfaces. Discov. Sustain. 2025, 6, 1116. [Google Scholar] [CrossRef]
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MDPI and ACS Style
Manganelli, M.; Moscatiello, C. New Insights into Hybrid Renewable Energy Systems in Buildings. Energies 2026, 19, 767. https://doi.org/10.3390/en19030767
AMA Style
Manganelli M, Moscatiello C. New Insights into Hybrid Renewable Energy Systems in Buildings. Energies. 2026; 19(3):767. https://doi.org/10.3390/en19030767
Chicago/Turabian StyleManganelli, Matteo, and Cristina Moscatiello. 2026. "New Insights into Hybrid Renewable Energy Systems in Buildings" Energies 19, no. 3: 767. https://doi.org/10.3390/en19030767
APA StyleManganelli, M., & Moscatiello, C. (2026). New Insights into Hybrid Renewable Energy Systems in Buildings. Energies, 19(3), 767. https://doi.org/10.3390/en19030767
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