You could use a Stirling engine. There are also semiconductor devices that can convert those types of thermal gradients directly to electricity. Frankly, it would also make a good hot water heater for a building.
Ideally, you would run a turbine with 1000C steam, but many useful systems can live with the low thermal gradient if they only have to refuel every decade.
Even if you get a 99% efficient machine, you still only have a few kilowatts of heat at near room temperature operation.