Sensor node life-time limitation in wireless sensor networks has long become an issue, preventing it to become a reliable ubiquitous network. In this paper, a new concept called wireless grid, which includes a fusion of wireless sensor network and wireless power transmission is introduced. By doing this, battery life-time problem can be avoided, hence, providing high network reliability. Wireless power transmission scheme adjusted to the sensor network operating environment is proposed to satisfy power requirement at the sensor nodes. Simulation results show that by using the proposed schemes, two power transmission nodes can supply the energy required for sensor nodes operating in a square room of 25m2 with 99% reliability.