Sonnen — Connecting the renewable energy community in Germany and beyond
Sonnen was founded in 2010 by Christoph Ostermann and Torsten Stiefenhofer with the goal to provide clean and affordable energy to everyone. Ten years later, the German manufacturer of smart home energy storage systems is one of the fastest-growing tech companies in Europe. The multiple award-winning company advances the digitalization of the global energy transition by operating several virtual power plants in the USA, Australia, Italy, and Great Britain besides Germany. Moreover, sonnen installed over 60.000 smart home energy storage systems worldwide as seen on this impressive map:
Some of the key milestones along the way were the launch of their first battery for small-scale PV system operators called sonnenBatterie in 2011 which was digitalized one year later to optimize the self-consumption of individual customers by, for example, taking the weather forecast into account. This step towards digitalization was expanded in 2015 with the establishment of their first virtual power plant (VPP) in Germany. The sonnenVPP connects individual sonnenBatterie users in the so-called SonnenCommunity in which members share self-produced electricity with each other.
In 2017, Sonnen introduced an innovative concept to its sonnenCommunity members, namely the sonnenFlat. Sonnen guarantees an electricity bill of theoretically 0€ if the members install a suitable combination of a PV system and a sonnenBatterie in their homes. In the case of a typical small family with a yearly consumption of 4000kWh, the requirements would be a 6.3kWp PV system with an 11kWh battery. The combination is set up to provide a self-sufficiency ratio of 75%. The members receive a free allowance for the remaining 25% of necessary electricity (e.g., 1000kWh for the exemplary family) which is supplied by other sonnenCommunity members who are producing surplus electricity in the moment of need.
The sonnenFlat participants will get a refund of 24–31 cents/kWh depending on their location if they do not consume all of their free allowance. Conversely, additional electricity can be purchased for a lower-than-average electricity price if more than the estimated yearly free allowance is used for some reason. Moreover, sonnenCommunity members have the option to earn some extra money by providing their home storage system for grid flexibility services managed by sonnen who became an official participant in the German energy balancing market in 2018. The above-mentioned setup would amount to a yearly income of 119€. Members with larger PV systems can receive a maximum of 178.50€ per year [1].
The sonnenVPP helps to reduce the curtailment of renewable energy by charging the batteries during times when more green electricity is produced than needed. So far, the TSO often curtailed wind energy in this scenario to prevent an overload of the power grid. 5.4 TWh of renewable energy was lost due to those curtailments in 2018 [2].
Recently, Sonnen introduced a slightly modified version of their sonnenFlat contract for solar PV system owners who lost their Feed-In-Tariff (FIT), labeled sonnenFlat direkt. It is estimated that around 18.000 solar PV system will lose their FIT in Germany in 2021. 176.000 solar PV systems with a capacity of 2GW will lose their FIT by 2025 [3]. The operators of PV systems without FIT are supposed to sell their own electricity via direct marketing under current regulations. However, this is often rather complicated and economically unfeasible, especially for small-scale operators. The worst-case scenario from an environmental point of view and for the advancement of the energy transition would be if these operators decide to dismantle their functioning but unprofitable PV systems.
SonnenFlat direkt, therefore, tries to offer an alternative for small-scale pioneers who operate PV systems with a capacity of 3–29.9 kWp by including them into the sonnenCommunity if they are willing to install a suitable sonnenBatterie. This way, the produced surplus electricity of the participating post-FIT systems will be directly marketed in the sonnenCommunity and the small-scale operators will receive their corresponding electricity free allowances for the days in which they do not produce enough electricity for themselves. The pioneers can continue to use their PV systems in an economically feasible and unbureaucratic manner [4].
This innovative concept can serve as a good example for countries that will soon face similar problems when the FIT will run out for their first renewable energy projects.
References
[1] https://sonnen.de/stromtarife/sonnen-flat/
[3] https://www.enbw.com/unternehmen/presse/kleine-direktvermarktung-solaranlagen.html
[4] https://sonnen.de/stromtarife/sonnen-flat-direkt/
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Text by Christian Doedt
