Windmills are large composite structures, usually located at difficult-to-access sites, bearing strong dynamic loads in a harsh environment. In-service inspection involves dismounting the blades, a very costly process. Instead of inspecting the windmills regularly, they are usually overdesigned. Furthermore, the design of a windmill is based on estimated wind conditions, while the real wind is seldom measured. The main inconvenience for it are the characteristics of the conventional equipment needed to carry out the measurements. The substitution of traditional sensors for Bragg gratings and piezoelectronics to measure the strain field and vibrational frequencies adds the advantages of a smaller size, no drift, no EMI and the possibility of embedding them while manufacturing, so the windmill is fully equipped when installed. Long-term measurements are possible to check both the in-service conditions and the degradation of the structure. Two possibilities were tested: embedding of the sensors while manufacturing with low disturbance of the process and surface-bonding of the sensors. Windmill qualification test were carried out to check the survivability of the Bragg gratings and the piezoelectric sensors under extreme environment are presently running. Results are hopeful. The next step could be a permanent connection via modem to a remote controller that can use the acquired data to map the wind conditions and/or the structural health.