1. Piezoelectric sidewalks - PowerLeap is developing a flooring material which they hope may generate 1 watt-hour per square foot for a cost of 100 to 200 USD per square foot. They project a dance floor made of the material may generate 10 watt-hours per square ft.
2. Solar panels on anything without the correct orientation - as solar panels can only use direct sunlight anytime they are not in the direct sun the output lowers substantially. PV panels with their low efficiency need a good location to have any chance of generating useful power. Car surfaces offer a very low area with the correct orientation at any given time.
Say a typical car takes about 0.8 kW per per km. In Izmir for July 2009 we are averaging about 7.5 kW/m2/day according to my weather station. All this comes to the point that 2 m2 of PV panels on a car roof top (which will be in less than the optimum orientation some if not most of the time) should power the car for approximately 2.8 km - really valuable!
3. Wind turbines that are advertised with a rating of say 1 kW in 25 mph winds but generate maybe 50 watts in the more typical 10 to 12 mph winds that most places receive.
4. Sources that rely on the 'subsidies and incentives' to become even marginally useful. The wind turbine described in item 3 is a case in point.
5. Wind turbines on cars that rely on the wind generated by the cars speed to capture power. That wind is generated by the primary fuel of the car and the turbine generates additional drag which causes the car to use more fuel.
6. 'Green energy' sources that utilize more hydrocarbons in their generation than they return for a net negative energy value. Reforming CH4 (even CH4 from biogas) to make H2 is energy negative (takes more energy to produce the H2 than the H2 produced contains).
Additions or disagreements?
Added detail to #2 & 6 on July 12 09
Edited by Russ - 7/12/2009 at 01:04 pm GMT