We think rocks and minerals helped early life get their energy. These were rocks and minerals that had electrons mobile enough to transfer energy to early life forms. Microbes that get energy this way are called 'lithotrophs.' Here's a wikipedia article about some lithotrophs living today: lithotrophs

Researchers are growing some microbes on electrodes. I heard a woman give a talk at a conference in Chicago 2 yrs ago, and different microbes grew on the electrodes when there were different voltages between the electrodes. It was an exciting talk. Here's a news article about this type of research: electric life forms

I think mechanical energy was one of the earliest forms of energy at the origins of life, before there were living cells as we know them. Enzymes tend to move open-and-shut to do the work they do on their substrate molecules, and I think that open-and-shut work may have been an endless energy source at the origins of life. You can read about this in the 2 links below:

hhansma mica
life evolved mica