They seem to have the right idea, but don't quite get it. What is useful is passive solar (not solar electric) and that applies to a house or greenhouse. Mostly that requires lots of insulation and thermal mass, and ways to keep from overheating in the summer. I think the ideas here are great, but the article sounds like it was written by theoreticians.
I have almost everything i need, but needto shore up food stocks.
The author hasn’t read the book, “The 500 dollar tomato”. I grew a garden last year. It cost me about three hundred dollars for dirt, fertilizer, fence to keep the dogs out, plants, and pesticides. I managed to can 8 quarts of tomatoes and 4 quarts of chili peppers. The squirrels got the beans and a lot of the tomatoes. Worms destroyed the cucumbers. Coons, borers, and drought got the corn.
Mom bought me a greenhouse about 15 years ago when I bought my farm. 12x10x8, double door, two vents; it really rocks. It was a floor sample at a lumberyard that was going out of business. It was $3K, she got it for $300 AND they delivered it! Deal of the century. I laid the brick floor myself, but it needs a little work; a few heaved bricks due to gophers...
I use it to start and harden off veggies, and also to extend the season with salad greens and stuff if I need to. There have been years when I’ve had fresh tomatoes, peppers, salad greens, etc. up until Thanksgiving. But, it is useless in the heat of the summer; unless I wanted to grow agave for tequilla, nothing can survive those 100 degree days in there. :)
In winter I give it up and grow greens indoors for the winter (55-degree fieldstone basement, grow-lights, etc.) because shoveling a path out to the greenhouse under 100” of snow is just not a ‘priority’ for me! :)
Regarding greenhouses, your observations are consistent with what I've read. Sure, you can heat a greenhouse, but that adds expense and vulnerablity (if power source is unavailable).
When weather is cold, during the daylight hours you open up the translucent surfaces to heat the greenhouse; at night you close the surfaces with blinds or whatever. Thermal batteries (such as jars of dark liquid) will store the heat to be released at night. Insulation keeps the heat it.
When weather is hot, you ventilate to avoid overheating. You can also limit the hours of sunlight with blinds if necessary.