A black metal surface can absorb significant energy from direct sunlight, with an estimated total incident energy of about 8 kilowatt-hours per square meter per day. Conventional black paints reflect 5% to 10% of incident light, leading to an effective absorption of around 0.9 kW/m² at worst. The discussion highlights the importance of minimizing heat loss through reflection and convection to maximize water heating efficiency. Specialized ultrablack coatings can achieve much lower reflectivity, enhancing energy absorption further. Understanding these factors is crucial for optimizing the design of solar heating systems.
