  Intelligent Reflecting Surface (IRS) utilizes low-cost, passive reflecting
elements to enhance the passive beam gain, improve Wireless Energy Transfer
(WET) efficiency, and enable its deployment for numerous Internet of Things
(IoT) devices. However, the increasing number of IRS elements presents
considerable channel estimation challenges. This is due to the lack of active
Radio Frequency (RF) chains in an IRS, while pilot overhead becomes
intolerable. To address this issue, we propose a Channel State Information
(CSI)-free scheme that maximizes received energy in a specific direction and
covers the entire space through phased beam rotation. Furthermore, we take into
account the impact of an imperfect IRS and meticulously design the active
precoder and IRS reflecting phase shift to mitigate its effects. Our proposed
technique does not alter the existing IRS hardware architecture, allowing for
easy implementation in the current system, and enabling access or removal of
any Energy Receivers (ERs) without additional cost. Numerical results
illustrate the efficacy of our CSI-free scheme in facilitating large-scale IRS
without compromising performance due to excessive pilot overhead. Furthermore,
our scheme outperforms the CSI-based counterpart in scenarios involving
large-scale ERs, making it a promising solution in the era of IoT.
