Award-winning photovoltaic system: solar power system as backup system offers protection against blackouts

The last large-scale power failure (blackout) in Europe affected about 10 million people: on 4 November 2006 at 22:09 pm parts of Germany, France, Belgium, Italy, Austria and Spain were without power for two hours. Even in Morocco the effects could be felt. In the event of a power failure or a network interruption, solar power systems are separated from the electricity network according to law. So far it was thus not possible to use one’s own solar power system as a backup for essential household appliances in the event of the public electricity network suffering a failure. This loophole has now been closed with the "Sunny Backup System" developed by SMA Technologie AG: in the event of a power failure the system fully automatically switches to “stand-alone power supply”. The Solarserver June 2007 wishes to present this innovative photovoltaic backup system as the “Solar System of the Month”. It maps the route to stand-alone supply safety with the help of network-coupled solar power systems.

Solar Energy System of the Month as PDF-Document

Innovative synthesis of solar power stand-alone PV system and connection to the network

Most of the approx. 330 000 photovoltaic systems in Germany that were installed up until the end of 2006 feed the direct current generated by solar modules on the own roof into the public network via an inverter. For alternating current that is compatible with the network, operators receive compensation in terms of the renewable energy law. Up to 54 cent per kWh is what network operators must pay for solar power from systems that are connected to the network in 2007. For economic and technical reasons solar power is not stored; to a certain extent the electricity network serves as storage. Also for private and industrial operators of solar power systems, electricity comes from the power sockets – provided the network is up and running.

By contrast, solar power systems that are not dependent on the network, also called stand-alone photovoltaic systems or solar home systems, provide consumers with power directly or from batteries if the sun is not shining. Such stand-alone PV systems can be found in cabins in the mountains or on holiday premises in Germany and, even more so, in rural regions of developing countries where no access to the electricity network is given. There the required supply of solar power is regulated by intelligent electronics around the clock and, depending on the need, direct or inverted current consumption devices are driven with power from the PV generator or from solar batteries.

In the past, blackout implied that solar power systems were off too

In the light of an increasing frequency of blackouts, solar power producers are asking themselves why their system linked to the network must be switched off for security reasons when the network is not supplying any electricity. And this is no longer a seldom experience: large-scale and long-term power failures occurred in Europe in November 2005, in November 2006 and, as a result of hurricane Cyrillos in January 2007. In the USA the centralised electricity network broke down almost completely on 15.08.2003. It is expected by experts that blackouts and temporary power failures will continue to increase. The result: no light, no heating, no electricity for the refrigerator and the computer – and all this in spite of the fact that solar modules on your own roof as a small decentralised power station could provide electricity for your own consumption needs.

Synthesis of stand-alone PV system and network connection closes supply loopholes

This is where the pioneering concept of the company SMA Technologie AG comes into play. The company was awarded the prize for the “Most Innovative Solar Product 2007” in March 2007 at the 22. Symposium of Photovoltaic Solar Energy in Bad Staffelstein. With the new Sunny Backup System owners can use their solar power systems even if the network is down and can supply essential electrical appliances with their own power. Within 30 milliseconds Sunny Backup will switch over to stand-alone power supply, even during the night or when the residents of the home are on holiday. The backup technology can be added to new as well as existing solar power systems easily and cost-efficiently without any negative impact on the photovoltaic degree of efficiency.

Solar power even when the network’s down

The solar backup system by SMA is based on over 25 years of experience in the development of network-linked photovoltaic systems and over 1 000 solar power stand-alone PV systems installed worldwide. Sunny Backup includes the first backup inverter certified in terms of DIN VDE 0126-1-1. The completely pre-configured sets including the automatic switching device and suitable batteries are available for three performance categories.

Simple, intelligent and reliable: the "Blackout Blocker" by SMA

During normal operation, solar power is fed into the public network through one or more inverters. Only when the network fails, the backup inverter supplies consumers inside the house directly, by forming a stand-alone network within split seconds. The central component of the solar emergency power system is the additional inverter “Sunny Backup 5000” that manages the entire system. Other components are the automatic switching device (AS box) that separates the photovoltaic generator from the network according to the respective standard in the event of a network failure, as well as a set of batteries. In the event of a network failure Sunny Backup co-ordinates all switching, e.g. the separation from the network and the switching of the PV system.