There could soon be a new member of the group of ‘clean’ renewable energy sources able to pick up the mantle from polluting fossil fuels. UCLA scientists are developing technology they hope will eventually become efficient enough to generate significant amounts of electricity from low temperatures of space. The research has recently been published in science journal Joule and details how ‘radioactive cooling’ that originates in space could be used to generate electricity.
The process that the research is exploring is one we regularly see the effects of but will have given little thought to. Early morning frost forming on grass and leaves despite night time temperatures not having fallen below zero is perhaps the most obvious manifestation of radioactive cooling we are all used to seeing. It turns out that happens because surfaces that face the sky, such as those of grass and leaves, lose energy as infrared light leaves them. This brings their temperature down to a lower level than that of the surrounding air – resulting in the formation of frost.
As explained by Aaswath Raman, who co-wrote the paper published in Joule:
“Some of the heat effectively escapes to some place much colder: the upper atmosphere and even outer space.”
The difference in temperature between two ends of a wire results in a process known as the Seeback effect – which refers to the generation of an electric current as electron move between the warmer and colder ends, creating a voltage. If a thermoelectric generator can efficiently enough harness that process, the scientists believe that could lead to an alternative to solar power. And one that compliments solar installations by generating electricity at night.
Thermoelectric devices are not an entirely new technology. They’ve already been used to generate electricity from the dissipating heat produced by power plants. There have even been attempts to build them into clothing and watches, to generate small amounts of electricity from the temperature differences resulting from body heat. But generating electricity from a source of cold as vast as the night sky would represent a new level to harnessing the Seeback effect.
Source: The Times
The prototype device developed by the researchers features a black aluminium disc with a 20 cm diameter, attached to a thermoelectric generator placed in a tray, which insulates it by keeping the ambient air temperature stable. The disk serves as the sky-facing surface. The original prototype generated enough energy to light an LED bulb but there is confidence that future attempts could quickly improve the efficiency of the engineering enough for the generator to become 20 times more powerful.
Dr Raman commented:
“What’s different here is that instead of finding a source of heat, we’re using a source of cold that’s ubiquitous and accessible: the night sky, and effectively the cold of space which lies beyond it. We then use the immediate surroundings and the air temperature as the source of heat.”
Perhaps counterintuitively, the technology would be expected to work best in the same kind of hot, dry environments that are ideal for solar power, potentially dovetailing with daytime power generation during the night:
“Our work highlights the many remaining opportunities for energy by taking advantage of the cold of outer space as a . . . resource. We think this forms the basis of a complementary technology to solar.”