Stirling Engine 15W Electric Generator - Upgrade1- to 25W with Helium

Test of the new modification with air and helium. Efficiency measurement : Running with air at 12 W (900mA,13,35V) during 30min. Amount of gaz (butane 70%-propane 30%) : 21g (42g/h) = 540W. Eff.=12/540=2.2%.