. . .
even if some engine can convert heat into electricity maybe by peltier, i dont think its economically feasible to do .
Nitinol springs that operate with heat difference, would probably be veeeery economically feasible.
It doesn't matter what technology you use. Unless your miner operates at 500 C, the amount of electricity you can generate is very small.
Even boiling coolant water could at best give you 25% energy recovery, even with a perfect system.