Thermocouples are expensive and inefficient. Replacing them with standard high power density solar cells would produce several times more power from the same solar collector setup.

What actually happened here was a couple of scientists were looking through some old papers with today’s green perspective. They saw something mildly interesting and speculated whether it could be adapted to be useful by today’s standards. That’s not worthy of the headline you gave it.

Actually, I’m going to pick on another bit of the article. 20mW is not just small. It’s minuscule. Scientists and engineers are known for understating things in conversational articles. It’s important that you understand this when reading articles written by scientists.

To illustrate just how small 20mW is, we receive roughly 1KW of energy from the sun per square metre. In order to capture 20mW of electricity using conventional solar panels at 20% efficiency you would need a single solar panel that was 3mm x 3mm. There is no indication of how large this device is but I’m guessing that it is larger than 3mm x 3mm. If we’re generous and call it 10cm x 10cm then it has an efficiency of 0.2%. Daisy chaining enough of them together would cover the earth several times over which is somewhat impractical.

When the scientist summed up at the end of the PhysOrg article, the main point he was making is that we should be getting energy directly from the sun, not that this device was the one that was going to make that goal feasible.