NOVELTY - The solar-powered device comprises a pyrolysis reactor (130) selectively operable by solar energy for carrying out thermal decomposition into products of sludge introduced into the reactor via a dedicated sludge inlet, a unit (140) for continuously sensing sunlight radiation and immediately providing an output data indicative of the amount of solar energy corresponding to the sensed sunlight, and a control unit (150) for receiving the output data and operating or shutting down the pyrolysis reactor based on the amount of solar energy generated from the sunlight.    USE - The solar-powered device is useful in a system for converting sludge into products such as steam, char, tar, syngas including hydrogen, carbon monoxide, carbon dioxide, and methane (all claimed), where the sludge such as wastewater sludge or sewage sludge and any by-product is useful in urban waste treatment plants, industrial waste treatment plants, agricultural wastewater treatment plants, petrochemical industry, chemical industry, pharmaceutical industry, food industry and other biomass sludge sources.    ADVANTAGE - The solar-powered device is capable of reliably converting sludge into products by providing comprehensive solution relying on solar power without require continuous work.    DETAILED DESCRIPTION - The solar-powered device comprises a pyrolysis reactor (130) selectively operable by solar energy for carrying out thermal decomposition into products of sludge introduced into the reactor via a dedicated sludge inlet, a unit (140) for continuously sensing sunlight radiation and immediately providing an output data indicative of the amount of solar energy corresponding to the sensed sunlight, and a control unit (150) for receiving the output data and operating or shutting down the pyrolysis reactor based on the amount of solar energy generated from the sunlight and under performance conditions dictated by the amount of solar energy. The pyrolysis reactor comprises an outlet (136A, 136B, 136C) for discharging products from the reactor obtained from the sludge decomposition, and is operated at a temperature of 800-1200 degrees C. The sensor comprises a unit for transmitting the output data indicative to the control unit, and is an integral part of the pyrolysis reactor or a distinct part from the reactor. The performance conditions comprise rate of sludge input into the reactor, amount of sludge input into the reactor, rate of product discharge, amount of solar energy, and/or amount of internal heat in the reactor. The control unit operates the pyrolysis reactor at daytime, and shuts down the pyrolysis reactor at nighttime. An INDEPENDENT CLAIM is included for a solar-powered system for converting sludge into products.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a sludge treatment system.    Dewatering unit (120)    Condensing unit (122)    Pyrolysis reactor (130)    Sensor (140)    Control unit (150)    Outlets. (136A, 136B, 136C)