Selling one's own green electricity to the energy supplier is becoming less attractive as feed-in tariffs fall. So it is not surprising that many new systems today are already delivered with a battery storage system. The topic of self-consumption optimisation is becoming increasingly important and many manufacturers have also recognised this trend in the market. Instead of temporarily storing the energy in a battery first and thus accepting conversion losses, it can make sense to consume it directly with the help of switchable devices. Or as a practical addition, if the battery storage itself cannot absorb the desired amount.
The functional principle is identical to that of a storage system. The excess energy is recorded with the aid of a meter device at the grid feed-in point and transmitted to the inverter so that it can switch on or off intelligently defined devices. As a rule, the switch-on and switch-off power limits can be freely defined, as can the time windows in which consumers may or must run. Although this area of application is still somewhat in its infancy, there are already a number of feasible solutions in the following.
The classic consumer. Almost all household appliances can be connected to standard household sockets. So it is obvious that suitable solutions are already available from several manufacturers. Depending on the energy generated, the radio socket is switched through, i.e. this is an ON/OFF circuit. Use in connection with a pluggable electric heater would typically be conceivable.
The control of a heating rod is obvious, as it also represents an energy storage, but in the form of thermal instead of electrical energy. Due to its high power ratings, it is particularly suitable for peak-shaving applications. Corresponding heating rod controllers can regulate the energy continuously and are therefore able to use the excess energy more dynamically and precisely.
Some consumers, in particular heat pumps, can often be switched on via a simple control signal. This pulse can be generated by a so-called potential-free contact (also referred to as a dry contact), which inverters have sometimes already integrated. Comparable to the radio socket, this is an ON/OFF control.
The Mennekes charging station communicates directly with the SMA Home Manager via the network and does not require a direct electrical connection to the inverter. SolarEdge's EV charger, on the other hand, will be a hybrid system of inverter and charging station that can charge the generated power directly into the connected vehicle. This involves a 5kW inverter with an extension for the charger and is expected to be available Q2 2019.
Comprehensive energy management is an enormous challenge because devices are often not based on the same type of communication. A standardised and cross-product communication protocol is required for integral control in order to enable intelligent control independently of the manufacturer. For this reason, the EEBUS Initiative was founded with the aim of establishing a communication interface based on standards and norms.
In future, intelligent consumers such as dishwashers/washing machines and heat pumps will be able to exchange data directly with the generation system and thus increase energy efficiency. Today, only a handful of devices from Bosch and Stiebel Eltron, for example, can be connected to PV systems, but this list will grow steadily in the coming years.