The basic concept is to combine a conventional gas turbine with a modified one, which has a heat exchanger instead of burners. Since gas turbines are pretty expensive, I'll try to modify/design 3D printed turbos for compression and decompression. So the project will be limited to temperatures of around 50-70°C. The heat exchangers are planned to be made of two nested copper pipes in crossflow configuration. In total I plan to have two heat exchangers, one to be heated by several candles (which should have a thermal output around 40W each) and the crossflow exchanger, which carries the heated exhaust gas in the inner tube and the fresh and compressed air in the outer tube. They are connected in series, so I only need one compressor/decompressor which will be connected to a regular BLDC Motor and generator. The generator will then be rectified to around 12VDC, and transformed to 40V by a DC-DC stepup converter. These 40V will then be sufficient for a grid tied inverter for mains connection.