How to solve two contradicting issues: bright sunlight from S. window and warmth with humidity for growing orchids?

I have large south-facing window (~65" wide, starts at knee height), but near it is quite cold at night or in windy cloudy weather. Window is winterized by transparent plastic. In clear sunny days temperature raises quickly and humidity drops to 24%.

I moved plants into two indoor greenhouses (covered by transparent vinyl, on wheels), added fluorescent lights (not enough) and PC fans, and placed all this in the middle of the room (4.5' from window).

Now temperature and humidity are good, but less light.

It is better to avoid moving at daytime to window, an at night in the middle of the room, this is living room, not a spare room. Adding enough recommended artificial lights makes this hobby too expensive for me at the moment.

Is it possible to heat indoor greenhouses locally, from inside, with less wattage than the whole room 650W oil heater?

Or find inexpensive fluorescent light fixtures, ready- or self-made? There are total 5 shelves 27"long. Short fixtures have low watts, multitube sets are very expensive, CFL are using a lot of vertical space.

Any ideas or links? Thanks.

Here is a link that might be useful: Tip to use sunlight when it's possible