system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't we convert all the heat energy on our super hot pavements and streets into useable energy?
gpt
In order to make use of the heat, the heat needs to have somewhere to go.

There needs to be a temperature difference, the bigger the difference the more energy you can extract from it.

If there was a source of cool water, like a stream, then you could use that temperature difference to run a stirling cycle engine, or a thermal - electric generator.

The main thing is that the there needs to be a difference in temperature. Simply laying a thermal electric generator on the hot pavement won't do much unless you can cool the other side of it.

The other issue is that even if the pavement was 150 degrees and the water was 40 degrees, that is only a 110 degree temperature difference. It is enough to extract some energy, but not a lot.