Sustainability truly interests me, so when I saw this course offered it really grabbed my attention. What I found most interesting about Mr Vales presentation far back these different contraptions have gone. I had no idea that some of these engines were used as substitutes for steam engines. All of them, the Sterling Engine, the Hot Air Engine and the Pelpier device were all so cool and unique. I think that the Pelpier device was probably the coolest mainly because of the fact that it can generate electricity through it. But all in all it was cool to find out the history and how far technology has come.