| Scientists have known for at least 200 years that electricity can be generated from a temperature gradient, a phenomenon called thermoelectric generation. Recently, researchers have developed thermoelectric conversion technologies by changing material parameters and introducing new principles. |
| For example, researchers have found that magnetic materials can generate thermoelectric voltage by inducing a flow of electron spins along a temperature gradient, called the spin Seebeck effect, and that increasing a device’s length perpendicular to the gradient boosts voltage. |
| Scientists would like to fabricate more efficient, thin thermoelectric devices based on the spin Seebeck effect. However, the thinner the device, the more difficult it is to maintain a temperature gradient between its top and bottom. |
| Satoshi Ishii and Ken-ichi Uchida of Japan’s National Institute for Materials Science and colleagues have solved this problem by making a device with magnetic layers that continuously cools at the top and absorbs heat from the sun at the bottom. In this way, the device harvests two types of energy. Radiative cooling occurs at the top, as heat is lost from a material in the form of infrared radiation, while solar radiation is absorbed at the bottom. |
