The increasing heat in cities poses a significant challenge to urban quality of life and human health. Existing measures to mitigate urban heat islands include both nature-based solutions, such as greening roofs and facades, but also technical approaches, such as reflective surfaces and improved urban ventilation. However, these measures are in several cases insufficient or not applicable, especially in densely built urban areas where space is limited and structural and climatic conditions impose specific requirements. This is exacerbated by competition for space in existing built-up areas due to different usage requirements.The study which will be presented, proposes a new technical solution: Active Bottom Surface Cooling (ABSC). Unlike passive methods that rely on humidification, shading or radiation reflection, ABSC uses mechanical and thermodynamic processes to enhance thermal comfort for pedestrians. The goal of this method is to lower surface temperatures in urban areas by installing pipes in the top layer of the ground surface, through which a refrigerant (primarily water) circulates. As a result, the technology reduces the energy contained in the surface.The implementation of pipes into the ground for heating purposes to de-ice surfaces during wintertime has been investigated in some studies. However, the approach of using this technology for cooling purposes has not been examined so far. Thus, numerical analysis of the physical processes involved in ABSC and its impact on the urban climate will be presented. The study will demonstrate how this technology can contribute to reducing temperatures in urban areas and improving thermal comfort in those spaces.

The accelerating global demand for renewable heating, cooling and electricity, driven by climate change and rising living standards, presents both a challenge and an opportunity for sustainable energy transitions. This paper introduces the Initial-Aid Cashback (IAC) model, an innovative business model designed to finance renewable energy solutions, with a focus on space cooling, by leveraging citizen participation and collaborative financing mechanisms. The model incentivizes private investors through discounted energy prices, while system operators benefit from reduced upfront capital requirements and minimised financial risk. Through two case studies, an office building in Romania (small-scale case) and the application of the REGEN-BY-2 technology in a mixed housing–office area (large-scale case), the paper demonstrates the model’s potential to accelerate the adoption of renewable cooling technologies, enhance profitability for operators, and provide attractive returns for investors. The findings highlight the model’s adaptability to diverse stakeholder needs, its scalability, and its role in fostering the clean energy transition (CET). However, challenges such as the need for a minimum number of investors, legal complexities, and trust-building among stakeholders are identified as critical barriers to implementation. The paper concludes that the IAC model offers a promising pathway to integrate citizens and small investors into the CET, while emphasising the importance of supportive policies, clear governance structures, and practical testing to ensure its success.

Rising urban temperatures due to climate change, limited green spaces, and dense urban areas impact public health and human well-being, highlighting the need for innovative grey infrastructure solutions where conventional green spaces are not feasible. This study aims to bridge the gap between objectively measured and perceived benefits of urban heat mitigation by combining social and technological methods within socio-ecological systems. First, a literature review of 759 articles, with 64 meeting the review criteria, and a bibliometric analysis examined the recent extensive research on participation and the connections between participation, resilience, and sustainability. Second, a chain of evidence as a qualitative method demonstrated how Active Bottom Surface Cooling (ABSC) can enhance outdoor thermal comfort (OTC). This emphasised the importance of participatory innovation and novel cooling technologies for urban resilience: hybrid (digital and analogue) participation can raise the awareness, acceptance, and effectiveness of such technical innovations. It revealed the need for an integrated framework, leveraging synergies: (1) community engagement tailors solutions to urban needs, (2) adaptability ensures effectiveness across diverse settings, (3) improved thermal comfort enhances citizen well-being, and (4) resilience strengthens the climate change response. By conceptualising cities as urban systems, the integrated framework fosters reciprocal socio-ecological benefits between people, nature, and the environment. Through hybrid participation and ABSC, it boosts community engagement, OTC, and well-being for sustainable urban development.