This detail is an array of vacuum tubes from a solar thermal collector. As opposed to the more common fluid filled flat plate collectors, these transfer solar energy through a Sol-Titanium coated copper heat pipe. The heat pipe heats the solar fluid in the manifold at the top of the collector. From there the solar fluid circulates the solar energy to heat the domestic hot water. The image below is the array during installation(6 panels in total). Notice the photovoltaic array on the roof too! The PV and Solar Thermal arrays are part of the renewable energy systems at the Teal Farm Vermont. See more photos here.
