Couldn’t we have a lead box lined with these radiation to electricity converters with a small amount of radioactive material in the center, and have an energy generating device that would last for thousands or even millions of years? Imagine putting the sun in a box lined with solar cells, but on a much smaller scale.
Is there a reason this wouldn’t work?
This article has a good breakdown. The biggest issue is efficiency. RTGs are around 5-9% efficient. Standard steam cycle generators are around 30% (see this article ) . You get much more usable energy from fuel used in a commercial reactor vice a RTG.
Can you ELI5 why the efficiency is so low on the RTGs?
They take the waste heat from nuclear decay and convert it to electricity through the use of a peltier device. Those work off of differential temperature and are pretty inefficient to begin with. Unmderated Nuclear decay doesn’t produce a lot of heat at one time, which is why reactors use a moderator to increase the power output.
From the article it looks like RTGs are just converting the heat energy into electricity. Seems like there’s a lot unused potential being missed.