Solar radiation and heat
Pro Research Analysisby 
Searched over 200M research papers
Solar Radiation: Source and Spectrum
Solar radiation is the primary source of energy and heat for Earth, originating from nuclear fusion in the Sun. This energy is emitted as electromagnetic waves, primarily in the wavelength range of 0.30 μm to 3 μm, which includes visible light and infrared radiation. These wavelengths are responsible for both lighting and heating the planet, making solar radiation essential for sustaining life and driving all renewable energy sources on Earth 1210.
Solar Radiation and Heat Transfer Mechanisms
Solar energy reaches Earth and is absorbed by surfaces, where it is converted into heat. This process involves several heat transfer mechanisms: radiation, convection, and evaporation. When solar radiation strikes a surface, it increases the kinetic energy of molecules, raising the temperature and causing heat to be transferred to the surrounding air and objects 12. In buildings, solar radiation entering through windows can significantly alter the indoor thermal environment, affecting both air temperature and the distribution of heat within rooms 347.
Impact of Solar Radiation on Indoor Environments
Temperature Regulation in Buildings
Solar radiation can increase the average indoor temperature, especially in winter, reducing the need for artificial heating. Studies show that the presence of solar radiation can raise the average room temperature by about 2.5°C, allowing for a reduction in heating system load 34. However, the distribution of heat is not always uniform, and areas exposed to direct sunlight may experience local overheating, while shaded areas remain cooler 79.
Heat Transfer in Building Systems
Solar radiation can be harnessed in building systems, such as ventilated floors or radiant heating systems, to improve energy efficiency. For example, integrating solar air collectors with ventilated concrete floors can increase the total heating capacity by up to 63%, although it may also cause local overheating of floor surfaces . Proper management of solar heat gains is crucial to optimize comfort and energy use 479.
Effects on Human Thermal Comfort and Health
Physiological and Psychological Responses
Exposure to indoor solar radiation affects human thermal comfort by increasing skin temperature and altering heat exchange with the environment. Direct solar radiation can raise local skin temperatures by up to 3.3°C and overall mean skin temperature by 0.6–1.6°C, leading to higher rates of thermal discomfort and physiological changes such as increased pulse rate and decreased blood oxygen saturation 56. The proportion of heat loss through convection, radiation, and evaporation also shifts, with radiation accounting for nearly half of total heat loss in neutral thermal conditions .
Work Performance and Comfort Limits
Strong solar radiation can reduce the upper limit of comfortable indoor temperatures by about 3°C compared to conditions without direct sunlight. This means that people may feel uncomfortable and less productive at lower temperatures when exposed to direct solar radiation, highlighting the importance of managing sunlight in workspaces and living areas .
Solar Radiation in High-Temperature Applications
In industrial and energy applications, concentrated solar radiation is used to generate high temperatures for electricity production, chemical fuel synthesis, and material processing. Efficient heat transfer is critical in these systems, involving advanced methods such as the use of liquid metals and engineered particle flows to optimize energy capture and distribution .
Conclusion
Solar radiation is the fundamental driver of heat and energy on Earth, influencing everything from global climate to indoor comfort and industrial processes. Its effects on heat transfer, building environments, and human comfort are significant and multifaceted. Proper understanding and management of solar radiation can enhance energy efficiency, improve thermal comfort, and support the development of advanced solar thermal technologies 12345678+2 MORE.
Sources and full results
Most relevant research papers on this topic