efficient orbital vehicles

So here's my idea for creating more environmentally friendly
orbital vehicles.

Create a launch platform that could be raised or lowered, say
50 miles, on which the orbital vehicles are attached.  The accent
of the platform can be slow - and it would be raised like
a hot air balloon heated by concentrated sun light.  Then,
when the launch platform was not in use it could also function
as a power plant - supplying electricity/power.

The orbital vehicles would be dropped from the platform,
developing acceleration, then turning upward to attain orbital
velocity.  The actual trajectory would need to be analyzed,
but at there most efficient, they would be able to use something
like electric jets/rockets.

Ideally, these orbital vehicles would be able to return to the launch
platform, and the whole unit would gradually descend toward
earth.

There are many ways to design, in detail devices of this type,
the issue being how long can you maintain a concentrated
beam of sun light.  There are addition design factors to consider
such as -

1) batteries.
2) orbital " winches " - as for example
Arthur Clarke style - elevators.
3) other stuff - I haven't or can't think of.

For example, the actual orbiting vehicles could be launched upward,
from the launch platform, as in some kind of balloon, and then at
a higher altitude, drop, then use engines of some type to attain orbital velocity.