This paper presents a novel obstacle and inclination detection technique for Macao world heritage district photovoltaic system using a 920-MHz Ultra-High Frequency Radio Frequency Identification (UHF RFID). The solar panel is tagged with a UHF RFID tag and a 3D printed hollow substrate covered by a defected microstrip resonator for the larger solar energy capacity required for heritage protection and development. Its tag antenna effective area can be significantly affected if an obstacle is placed between the tag and reader. The 3D hollow substrate is filled with water, and the water flows with panel inclination establishing a perfect conductor plate (PEC) for the tag antenna slot. An experimental trial of the tag's Received Signal Strength Index (RSSI) reports more than 18 dB difference with and without obstacles. The inclination detection with 90 degrees variation is verified by RSSI change from -68 dBm to -57 dBm. This property is a simple and economical solution for a photovoltaic system to detect obstacle shadowing or covering of the solar panel, and efficient inclination detection can be easily integrated.