Well, before I follow the conversational drift, I agree that there should be a means of unloading the cars one accumulates, even if it's just a 'ditch the junker' Action similar to dumping bodies.
NOW, on to the 'energy sources' tangent:
One thing to remember is those ol' Laws of Thermodynamics; you can't get something for nothing, and well-nigh invariably, you always get less back that what you paid in.
Another thing to remember is
every change has consequences:
Fossil fuel? Increased waste CO2 and greenhouse gases, reduction of relatively non-renewable resource (unless you're willing to wait for a few million years for fresh stuff to be created
)
Nuclear power? Waste materials from fission, as well as greater consequences if accidents happen than with a coal power plant, or a diesel locomotive breaks disastrously, and even MORE
non-renewable fuel. Fusion takes a huge overhead to get started, is very difficult to continue stably, and when becomes unstable has a huge potential for an equally huge initial disaster, although with far less long-term 'irradiation' consequences than fission.
Hydroelectric? A) Radically changing environment surrounding the dam (flooding a valley upstream, and turning a river into a trickle downstream) and B) potential disaster waiting downstream (See "Force 10 From Navarone"
)
Wind Power? All those propeller-dynamos are being 'pushed' by the wind, and some of the air's kinetic energy is being transformed into electrical potential...and so there's LESS WIND leeward of the big prop farm. Climate is altered by the 'theft' of this energy from the equation.
Tidal? See Wind, just in a different medium.
Solar? Well, if you are using ground-based collection, you're stopping that light energy from reaching the planet itself. Climate changes because less heat reaching ground, quite apart from the clearing swaths of land to place the solar cell array.
Now, if you're thinking of space-based collection, you're starting to pique my interest. Lagrange Points (apart L3 being waaay too far away, and L2 being in the Earth's shadow, and L1 actually shading part of the Earth...besides, the first 3 Lagrange points are pretty unstable, anyway) would be a good place to situate a HUGE solar collector array, and L4 & L5 would be collecting energy that would almost certainly be heading for deep space, and not the other planets, and couldn't possibly have any consequential effect on them due to the relatively minuscule amount of energy we're leeching off...honest...
Then you only have the issue of transferring that stored energy from the solar collection satellite to the Earth itself - SAFELY, mind you; no transmitting a microwave signal that misses the expected reception site due to unexpected high-altitude weather altering air density, and a city gets torched by mistake.
In short, when it comes to Mother Nature, you can still 'cheat the house', but only temporarily, and the punishments are rarely in a foreseeable manner.