A thermal tracking system for a concentrating photovoltaic system is disclosed. A wireless network can therefore include multiple APs, each of which will automatically choose a channel such that channel usage is optimized. The request may be included in a message to the IM server from a client, or the request may be in the form of IM session parameter, for the client, that authorizes an offline chat as the preferred type of IM session under certain conditions. The optional central porous tube can also be used as a bearing surface or, if attached to the inside edge of the ribbon, a power take-off shaft. The ciphertext may include a component to authenticate the sender once the ciphertext is received and decrypted by the recipient using the private key of the recipient.