The solar hot water heating system I saw in Tucson, AZ, back about 1979 or thereabouts, wasn't terribly sophisticated. It did use vacuum-insulated, transparent, coaxial glass tubing to contain the water surrounded by vacuum, factors that probably jacked it's cost up beyond profitability. Enclosing each mostly vertical pipe was an open trough section of a cylindrical quasi-eliptical lens. The pipes were actually tilted to an optimum summer angle for Tucson. The cylindrical lens was mounted on bearings that would allow it to rotate around the heat-collecting pipes, thus tracking the Sun from dawn until dusk and focusing the Sun's energy on the inner water-carrying pipe. I arrived on the site around mid-day and steam was already venting from relief valves. There was no provision for storing the heat during the day for use during the night. The builders said the solar hot water system added about twenty thousand dollars to the cost of the already expensive house. And it apparently was only effective in the low humidity, high daily temperature, environment of the desert surrounding Tucson... where the sky is not cloudy all day. Still, as a solar concentrator, I thought the design had promise if the inner pipe was covered in photovoltaic cells, and cooling water was circulated to control the PV temperature.
Back then, solar PV cells were quite expensive, although some work was being done on the manfacturability of amorphous silicon cells whose promise was a cheaper cell with comparable performance to monocrystalline silicon cells. I haven't investigated lately, but I think monocrystalline solar cells are now common as the market stepped up to fill the demand for off-grid power. So a cheap
solar concentrator might be a good way to improve output power and efficiency. It isn't necessary to move the solar panels around with an x-y drive mechanism. It is sufficient to move the light around with x-y driven mirrors. It isn't even necessary to use focusing mirrors. A lot of small flat mirrors, moving in unison, will easily approximate a large focusing mirror. Check out
these images of large solar thermal plants that generate steam to move turbines that generate electrical power. France has been at the forefront of this research, almost since the beginning, but the effort today is world-wide to capture low-quality solar energy and convert it into high-quality electricity. Efficiency is not as important as the capital investment required, which although cheap compared to, say, a coal or oil fired plant or a nuclear plant is nevertheless significant with no guarantee of payback in a reasonable time period, versus other "traditional" investments that may return a smaller gain but with less risk.
Bottom line is this: if you want to collect and use solar energy, avoid shade. Cut down trees and raze buildings if you have to, but don't cramp your efforts by providing
any deliberate or accidental shade. Building your array in orbit would be even better, but the financial and technical risks are high.
