Demand for space cooling systems is growing worldwide. The main reasons are socioeconomic developments such as the growing world population and the rise of economic wealth, especially in developing countries. These developments run simultaneously with global warming effects, increasing the need for cooling. This study introduces the development of the Cooling Demand Market Index (CDMI), which indicates the demand for cooling appliances worldwide at a spatial resolution of 1 km. It is based on population density, Gross Domestic Product (GDP)/capita and Cooling Degree Days (CDD) per climate zone. The CDMI is calculated for 2020 and 2050 in four different future scenarios in accordance with the Spatial Socioeconomic Pathways (SSP) and Representative Concentration Pathways (RCP). Further, the Solar Thermal Cooling Index (STCI) was developed to spatially estimate the worldwide potential to use solar thermal cooling systems based on solar availability and limitations due to maximum heat rejection temperature. Results of the CDMI show that the economic demand for cooling solutions is increasing, especially in developing countries, and that India will be by far the largest market by 2050. Countries such as Burundi and the Democratic Republic of the Congo show the strongest national increases in CDMI. The STCI indicates that ammonia absorption chillers and zeolite adsorption chillers can serve the vast majority of the market thanks to their capability to run at high condenser temperatures.

This paper presents the results of the activities related to the subtask “Building and process optimization” of the IEA SHC Task 65. The main topic of this activity was the integration of solar cooling in retrofitted HVAC systems. Based on the current conventional HVAC systems, the integration may present difficulties concerning cold distribution and refrigerants. Cold supply systems can also reduce airflow in air-based systems and enhance thermal comfort in buildings. The best technical actions for specific scenarios were mentioned considering both technical and economic aspects. Unfortunately, not all the analyses that were planned provide useful data. Results show that there are few recent projects that consider the application of solar cooling systems in buildings and most of them are based on simulation. Moreover, not much data about the characteristics of the buildings (envelope, other cooling systems, comfort conditions, etc.) are reported in the studies. This is because many of them are more focused on the plants’ configurations, and the performance of the different plants is in general assessed by testing the prototype in a single room. Despite this, the information provided could be used as baseline cases in order to study the potential energy savings achievable by applying solar cooling systems.

Currently, the European development and manufacturing of renewable and sustainable technologies are both critical and crucial. The EU-funded H2020 project REGEN-BY-2 demonstrates the manufacturing and testing of an innovative tri-generation technology that can simultaneously provide electricity, heat, and cold. The novel unit mainly operates using two-phase flow, demanding special requirements for individual components, mainly expanders and compressors. However, this technology has not been demonstrated; it is already relevant to identify later user types and investigate their future mechanisms in the heating and cooling demand. This analysis presents the four most important user types and various combinations of these, the joint use cases. The industrial, retail, office, and residential user types are first described in terms of their general characteristics, potential dependence on climate, and daily operation schedules. The results show that office and residential user types lack simultaneous demand for heating and cooling, as they are mainly influenced by seasonal weather conditions. Industrial and retail users, on the other hand, require both heating and cooling throughout the year with only daily variations. A system approach of the tri-generation unit coupled with thermal energy storage (TES) and additional auxiliary units, such as boilers and chillers, seems most promising for later applications. In addition, the availability of potential heat sources to drive tri-generation was verified. Industrial users are not only promising end-users, but also potential heat suppliers with a focus on untapped waste heat. This analysis follows a generalized approach. The next step would be to identify real use cases and examine the dimensioning and adaptation of the tri-generation unit in a complete system concept.

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.