The emerging LoRa technology is quickly becoming the de facto standard for Low Power Wide Area Networks. Herein, the LoRaWAN medium access sets up a lightweight network architecture able to connect very low power devices to the Internet. Several periodic reporting applications conveyed by LoRa require the collection of an increased amount of sensor information during the daylight hours, e.g. monitoring air pollution or sun intensity. However, the expected increase in the network throughput is currently limited by the default LoRaWAN Pure ALOHA access scheme. In such a context, even a time synchronized Slotted ALOHA access would double the achievable throughput. On the other hand, the power consumption would be increased for synchronization duties. The goal of this paper is to leverage Slotted ALOHA to increase the data collection rate range of such applications and to determine which access scheme maximizes their energy efficiency for a given frame periodicity. Results show that a proper skip of synchronization beacons is crucial to handle efficient and scalable LoRaWANs.