Wireless power transmission in a variety of closed environments are considered in this article to realize high-efficiency, high-stability, and high-security power transmission applications. Considerations for EM compatibility, energy loss, multipath effects, and other issues unique to closed environments must be made. Wave propagation can be altered to select the receiving targets of WPT in a closed cavity by controlling the emission frequencies. Characteristic weak microwave leakage from a cavity allows for small transmitting and receiving antennas that can achieve high transmission efficiency. WPT in enclosed environments find potential applications in industrial automation to enhance efficiency and safety, and in consumer electronics for convenience and improved user experience.