It occurred to me that solar thermal panels could be produced for much less that the $150 USD per square meter that current panels cost. This can be done by extruding the case and filling it with insulation at the same time. This reduces the cost for the case to $15-$20 USD.
Using plastic instead of glass reduces the cost even further. The cost per 48 x 96 inch sheet is between $65 and $100 USD depending on thickness.
Aluminum tubing and coil runs from $1.5 to $2.0 per pound. Large rolls of aluminum coil are $1.50 to $2.00 per pound. The amount of aluminum used for both the heat collector and the piping is under 10 pounds.
Total cost for a 4 x 8 foot (3 m^2) panel is approximately $100 to $140 USD. Making the cost per square meter $33 to $47 USD. Making these extruded panels cost less than 1/4 of the current commercially available panels.