New Communication Standards for PV Hybrid Systems The &quot;Universal Energy Supply Protocol UESP&quot;, which we developed at Fraunhofer ISE for innovative energy management of PV hybrid systems, has been further standardised. We have equipped the &quot;Energy Dispenser&quot; devices, designed for load management and energy distribution in PV hybrid power supplies for villages, with an interface for manufacturerindependent communication with a higherlevel energy management unit. Georg Bopp, Matthias Vetter, Jakob Wachtel, Michael Zillgith, Günther Ebert<br/><br/>Fig. 1: &quot;Tarom&quot; PV charge controller from the Steca company for 24 V / 70 A with a UESP interface. The UESP interface consists of a small embedded system from the SSV company with a 32-bit coldfire processor (to the lower right of the photo). Fraunhofer ISE has implemented the UESP protocol including the network management under the Linux operating system in this interface. The same embedded system is used for the CANopen interface of the Energy Dispenser (Fig. 2).<br/><br/>On the initiative of Fraunhofer ISE and several photovoltaic companies, the new Special Interest Group (SIG) on &quot;Battery-Based Decentralised Energy Supply Systems&quot; was founded within the CAN (Controller Area Network) in Automation (CIA) Organisation in 2007. The SIG is preparing a standardised and manufacturer-independent communication protocol for off-grid PV-hybrid systems. It is based on the Universal Energy Supply Protocol (UESP), which Fraunhofer ISE developed in co-operation with industrial partners including the Steca company. UESP allows the networking and optimal energy management of system components, simplifies the planning and installation of photovoltaic hybrid systems and simultaneously leads to cost-optimised and reliable system operation. UESP already communicates via the CAN bus, but still uses a manufacturer-specific network management system. Within the standardisation process, the network management system will be replaced by the industrial standard, CANopen, and the application scope will be extended to all types of off-grid energy supply systems with battery storage. In 2007, we set up two PV hybrid systems with UESP and programmed a CANopen interface for the &quot;Energy Dispenser&quot; made by the Spanish company, TTA. The Energy Dispenser is an intelligent electricity meter and serves to distribute limited amounts of energy fairly and to optimise the usage of the available solar energy in PV hybrid systems. We replaced its proprietary communication bus by a universal CANopen interface. As a consequence, in future the Energy Dispenser can be used in every PV hybrid system, independent of the manufacturer. The work is being carried out within projects that are supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and the European Union.<br/><br/>Fig. 2: The Energy Dispenser distributes a certain amount of energy per day. If a large amount of energy is available to the system (e.g. during sunny periods), the users can consume twice as much energy for the same price. Conversely (e.g. during the night, when the battery capacity is almost exhausted), only half as much energy is supplied for the same price. We replaced its proprietary communication bus by a universal CANopen interface with standardised commands for input and output devices.<br/><br/>68­Fraunhofer ISE Annual Report 2007