Not for space craft if what @MilderRichter says is right. To generate power from a peltier you need a temperature differential between the two sides. It is very hard to bleed off heat in space since it's a vacuum. That means a temperature differential is very difficult to achieve and it takes power to do that. Which would necessitate more of these, which means a bigger or additional heat removal system, which means you need more of these, which means a bigger or additional heat removal system, etc, etc, etc.