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Think tank report says German solar-plus-storage breakthrough is imminent, warns of challenges

Optimising household self-consumption using battery storage will be key to a network that can cope with "huge amounts" of PV being added to it. Image: Sonnenbatterie.

One research firm has welcomed predictions from a think tank that Germany’s electricity network could cope with the addition of “huge amounts” of solar-plus-storage and even benefit, but also agreed that policy changes will most likely be required to enable that scenario.

A new briefing by think tank Agora Energiewende presents a “what if” scenario in which Germany could have as much as 150GW of PV by 2033, including 80GW on residential rooftops. Co-authored by two of the think tank’s directors, Matthias Deutsch and Patrick Graichen, it assumes that in this scenario, especially given falling costs and price pressure exerted by Tesla’s low benchmarks, among other factors, around 40GW of household batteries would be installed.

The expansion in the numbers of residential solar-plus-storage systems would be “massive” in the instance of this kind of battery “breakthrough”, the authors claimed.

An Agora spokesman confirmed to PV Tech Storage today that the headline findings of the report, which is yet to be translated into English from its original German version, essentially state that the country’s grid could cope with a cumulative PV generation capacity of 150GW and around 70GW of wind power using storage. As with other regions, there appears to be a growing recognition also that storage can benefit the network by providing grid services. However, the spokesman for Agora said, it will depend on “how it [the storage] is controlled”.

Research firm EuPD agreed with many of the assertions made by Agora Energiewende, including the fact that barriers remain to achievement of this “best case” scenario.

“There is no doubt about the potential for energy storage…however the potential described in the report from Agora can only be reached with the right framework conditions. Currently, not even the annual expansion targets of 2.5GW (of PV) will be reached,” Saif Islam, a senior analyst at EuPD told PV Tech Storage today.

Others in Germany’s solar industry, including trade association BSW Solar, have also said that the slowing of the market, caused in part by drastic feed-in tariff reductions, will mean the former global leader in solar deployment will miss even that modest expansion goal.

Solar installations at residential level have dropped significantly on previous years, but the proportion of new systems installed in conjunction with energy storage is increasing. However, it seems this boost may not be enough.

Think tank report says German solar-plus-storage breakthrough is imminent, warns of challenges

Testing times: storage has been seen as providing a 'silver lining' for Germany's PV industry, but the warnings are that this might not be enough. Image: TUV Rheinland.

Recommendations made on policy and technical measures

Agora Energiewende, originally founded by former Green politician and now state secretary for the economic affairs and energy Rainer Baake, has recommended a mixture of technical measures and regulatory changes that will enable this high renewable energy deployment scenario to occur. Ultimately, key to this would be optimising self-consumption from household batteries.

At a technical level these recommendations include a look at charging strategies for batteries. For instance, it would be an “unfavourable strategy”, the authors said, for many batteries to be run simultaneously without being smart metered to co-ordinate charge and discharge. One example cited would be that excess PV electricity running back into the grid could cause sharp peaks in feed-in, leading to imbalance.

Conversely, a favourable charging strategy for PV-linked-storage would include using forecasting of demand and supply at individual user and system level, while capacity from grid-connected households could also provide grid-balancing services. This would contribute flexibility to the network, reduce residual demand and adapt to the addition of variable renewable energy sources.

In terms of policy, Deutsch and Graichen’s brief report picks four areas that they felt require reform.

  • Regulations should be put in place that further limit the amount of power that can be fed in to the grid from 70% from a 30kWp PV system at present, to 40% or 50% of installed capacity. This would properly incentivise system users to self-consume their energy. Technical guidelines on how to tie systems in to the network should be developed as a priority.
  • Greater regional flexibility for distribution networks would allow network operators to manage distribution bottlenecks that result from high volumes of electricity being fed in or out of regional networks.
  • Germany’s legislators should make plans to prepare for the possible ‘150GW of PV’ scenario, perhaps including the development of a long-discussed north-south national power line network.
  • The think tank also expressed a concern that the current system of levies and surcharges for renewables will cause higher charges for individuals without the option of solar self-consumption. While Agora saw this in itself as an incentive for households to get solar to avoid charges and stated that at present levels of deployment the surcharges and levies are not a significant burden, this is likely to change in the medium to long term. Financing Germany’s Energiewende (‘Energy Transition’) would only be possible with comprehensive reforms, the group claimed.

Saif Islam said EuPD broadly agreed with Agora’s conclusions, including fears over swelling surcharge and levy commitments.

“There is no doubt about the potential for energy storage in Germany; however, the legal framework for the predicted expansion needs to be cleared, because there will be larger cost components in form of taxes and levies.

“Should the amount of self-consumers increase significantly, then the government will claim taxes and levies, which will have a negative impact on the attractiveness.”

PV Tech approached the German federal ministry for economy and energy this morning for comment, but did not receive a reply in time for publication.

2014 report questioned short-term network need for storage

In 2014, Agora Energiewende published a report stating that in the short term, the role of energy storage in allowing the grid to accept more power from renewables would not be critical - at least not until the contribution of renewables to Germany’s energy mix neared 90% and balancing with storage became necessary.

The latest document approaches the topic from a different angle, looking at what will happen if the energy storage sector starts to see increased volumes of activity as a result of market forces and consumer choice, rather than a look at the need for storage from a system level.

Tags: solar-plus-storage, renewables integration, grid stability, residential, battery, grid connection, grid services, germany, rainer baake, energiewende, agora, eu pd research