Effects of alternative energy souces

I just finished reading Clean tech revolution.  Good book, excites me to think of technology advancing green initiatives and the role that a technologist can play.

When thinking about tapping into renewable energy sources – solar, geothermal, wind, tidal, etc. – I can’t help but wonder what the effects on nature will be when harvesting these natural sources.  I’m clearly a novice when it comes to geo-physics but you’d have to think these energy sources have huge roles in heating the earth, conducting air and ocean current, controlling weather, etc.  Would we be using so little of this energy that it doesn’t make a difference?  I’d love to read more research on this.

To me, it’s still pretty simple.  Humans demand WAY too much energy from the earth.  Whether you’re taking energy locked away in fossil fuels, or from wind blowing by your house to power an automobile … it’s going to have an effect on our ecosystem.  Ultimately, the only real clean watt is the Negawatt … the watt you don’t use.