Materials that absorb sunlight well include dark surfaces, water and metal. The sun's light energy arrives as a mixture of visible light, ultraviolet and infrared; some materials absorb all these wavelengths well, while others are better suited to a certain restricted types of light. Most materials convert absorbed sunlight into heat energy; living things, however, turn the sun's rays into chemical energy and the building blocks of life.
Water: Global Heat Reservoir
All water absorbs a lot of energy from the sun, with the amount absorbed directly dependent on how large the body of water is. For example, an ocean will absorb more energy than a lake. Water releases the energy back into the surrounding air very slowly. This is why when you go to the beach, temperatures are generally a few degrees cooler than they are further inland, as the water takes in much of the heat.
Spirulina: Efficient Algae
Spirulina, an algae found in open sources of warm, fresh water, absorbs energy from the sun. Called the "sun food," spirulina contains phycocyanin which helps the plant absorb the entire light spectrum, enabling it to absorb more sun energy than other plants. It is often used as a dietary supplement as it stimulates red blood cell production and can also protect cells against aging.
The Concrete Jungle
Concrete absorbs solar energy well, which is why sidewalks tend to get so hot under direct sunlight. Partly for this reason, concrete is not a popular building material for homes or office spaces. Painting concrete can make a slight change in solar energy absorption. For example, white paint will deflect more light while black paint will absorb more. However, the difference is minimal, particularly if the concrete is in direct sunlight.
Darker Means Hotter
Darker colors tend to absorb more energy from the sun than objects with lighter colors. Someone wearing a white T-shirt in the summer will find that he is cooler than someone wearing a black or dark-colored shirt. This is true of all materials which have dark colors. Other dark surfaces include blacktops, paved roads or rooftops.
Warming up to Metal
Most metals absorb solar energy well, as anyone who has touched a car sitting outside in the sun for some time should know, although you may notice that a white car is a tad cooler to the touch than a black one thanks to the lighter color. Building features made of copper, stainless steel or other metals retain the sun's energy.