Abstract: The radiation-selective absorber coating for absorber tubes of parabolic trough collectors includes two or more barrier layers (24a, 24b); an infrared reflective layer (21) on the barrier layers (24a, 24b); at least one cermet absorption layer (22) above the infrared reflective layer (21) and an antireflection layer (23) above the at least one cermet absorption layer (22). The two or more barrier layers (24a, 24b) include a first barrier layer (24a) of thermally produced oxide and a second barrier layer (24b) arranged above it. The second barrier layer (24b) is a cermet material including at least one oxide compound and at least one metal. The oxide compound is aluminium oxide, silicon oxide, nickel oxide and/or chromium oxide. The metal is molybdenum, nickel, tungsten and/or vanadium. The invention also includes an absorber tube with the absorber coating on it.

Abstract: A forced flue type combustion device in which an orifice is provided in at least one of an air supply passage and an exhaust passage, and in which the existence/nonexistence of a clog is determined on the basis of a detected pressure difference between the pressures on the upstream and downstream sides of the orifice, is arranged so that the existence/nonexistence of a clog can be determined with accuracy even during weak combustion with a low rotational speed of the combustion fan. Processing for increasing the rotational speed of the combustion fan is intermittently executed during weak combustion. During weak combustion, clogging determination processing based on the detected pressure difference value is executed only when the rotational speed of the combustion fan is increased. Clogging determination processing is started after the rotational speed of the combustion fan has become stable.

Abstract: The present application provides a primary reflector in a solar collection system. The primary reflector includes a first reflective section that can reflect solar rays onto a first focal line, a second reflective section on the left side of the first reflective section, and a third reflective section on the right side of the first reflective section. The second reflective section can reflect solar rays to the right side of the first focal line. The third reflective section can reflect solar rays to the left side of the first focal line.