Ralf Bischof, published in SOLARZEITALTER 2-2024
This article was originally written in German and has been translated by EUROSOLAR.
Solar infarction through uncontrolled solar power plants?
According to numbers from the Bundesnetzagentur (German Federal Network Agency), in October 2024 around 96 gigawatts (GW) of solar generator capacity (peak, p) were installed in Germany1. Every month around 1.5 GWp or 1500 megawatt (MW)p will be added. In the past in extreme cases, around 70% of the installed generator capacity has appeared as actual output in the grid. The soon to be expected 100GWp will therefore correspond to around 70GW of grid supply. The minimum demand in Germany is however only around 40GW. On sunny days with less demand like Easter or Pentecost, the generation from photovoltaic could clearly surpass the use. Due to the strong expansion of photovoltaic in our neighbouring countries, exporting in such situations is often no longer possible. The storage possibilities are also limited. Pump storage and large batteries can currently absorb a maximum of 11GW2. Flexible loads are also lacking. Is there consequently the threat of a “solar infarction” – the overloading of the electricity market and grid – as much of the media is saying?
Absolutely not. Among others, a study for the Federal Ministry for Economic Affairs and Climate Action (BMWK) shows that around two thirds of the output of all PV-facilities are controllable – even if they do not directly mark their electricity directly. At facilities with over a 100 Kilowatt (kW) peak, remote control for supply management was already introduced with the renewable energy law (EEG) of 2009. For new facilities from 100 kW, these requirements also apply due to the direct marketing obligation. Additionally, since many years facilities with a generator output above 30 kW and 25 kW from 2012 and 2021 respectively, must be controllable through the grid operator – even if they receive a fixed supply tariff.
Only around a third of the installed facilities with a nominal output under 30 kWp – currently around 30 to 35 GWp – are not yet controllable. However, these facilities currently have a clearly reduced effect on the grid than the average. In extreme cases, only around 50% of installed generator capacity is actually used in the grid and the trend is downwards. That can be said with certainty, as the projected supply capacity of solar and wind power plants in the supply tariff is published by the transmission system operators (ÜNB)3, as is the installed capacity in direct marketing.
There are many reasons for the reduced grid load through small facilities: own consumption, home storage and controllable appliances like wall-boxes, heat rods or heat pumps. In the twelve months from October 2023 to October 2024 alone, 3.2GW of home storage was realised. Furthermore, smaller systems on roofs have a wider range with regards to disposition and facing the sky in comparison to ground-mounted systems. For this reason or as a result of the so-called “70% rule”, many inverters are designed to be clearly smaller than the generator output.
Assuming around 30 to 35 GW peak uncontrolled PV-systems at the end of 2024, this will provide a maximum 15 to 18 GW to the grid. This lies clearly under the minimum load in Germany and leaves enough room for other small systems and the necessary must-run-power plants (system services, industrial heat and power). The number of existing PV-facilities with secure output is therefore not a threat to the electricity system.
Two other circumstances should really worry us:
- Direct marketing does not do what it promises. A large share of the systems do not react to the market prices4. The transmission system operators have secured that even on a day with extremely negative prices in 2023, only around half of the 58 GW directly marketed wind energy systems are adjusted5. In individual cases, there might be reasons provided (for example, technical failures), but not to this extent. Biomass, which is lauded as flexible, also feeds into the grid more or less constantly, although we spend over 200 million Euros every year on the so-called “flexibility bonus”6.
- Additionally, it is not certain how many of the systems over 25 kW peak that are controllable and receive a feed-in tariff according to the EEG, would in fact be adjustable by the grid operators in an emergency. Apparently this would be best checked during installation, and then never again. Why many grid operators act so negligent is difficult to understand. It raises the question of whether auditors may approve the rollover of EEG payments, although the fulfilment of the legal requirements is not free from doubt. Exactly this raises the question of whether the Bundesnetzagentur doesn’t need to check if the relevant distribution system operators fulfil their obligations to operate the grids safely.
So the problem is not small systems without control, but systems controllable by law, whose control through electricity providers or network operators are not happening in cases of doubt. Therefore, it is not understandable when even the professors and scientific advisers to the BMWK call for more “direct marketing” instead of “feed-in tariffs” as the decisive way forward. In view of the facts, the isolated calls for an end to subsidies of private solar installations can only be seen as obscure.
New installations must bring contributions
The argument to the contrary is however, not correct. The problems concerning control and direct marketing of large existing installations must be tackled quickly. Marketing and controllability of small PV-installations must be improved regardless.
For one, new photovoltaic installations on 20 GWp per year growth and if, as is currently the case, a third of these installations could not be controllable if there is an oversupply on the market or local networks and so the current security buffer is foreseeably quickly eroded. Conversely, the expansion of plug-in solar and other small installations should continue to be possible.
The suppression of grid feed-in during hours with oversupply no longer has to lead to a loss of energy. Battery storage has become so cheap that no financial disadvantages are to be expected. The electricity can be saved and avoid expensive grid consumption in the morning and evening hours. In the winter, the battery can be used in the hours with large supplies of wind energy to create cheaper prices in the grid. Regulatory hurdles for this mixed supply should be lifted in the near future. Furthermore, summer-induced surpluses of solar energy can also be used for very affordable heating rods for warm water and thereby save on natural gas and oil. Wall-boxes and heat pumps may also be time-managed.
In connection with the rollout of intelligent measuring systems – smart meters – it makes sense to set the threshold of control for new PV-installations at 2 kWp instead of the previous 7 kWp. That corresponds to the generator size with the plug-in devices (up to 800 watt inverter capacity) to still be sensibly equipped. In any case, the typical private roof tiles should be included, of which millions in Germany are still needed. As these are already covered by the regulations for controllable consumption facilities with a large storage system according to Article 14a of the Energy Economy Law (EnWG), no duplication of effort is to be expected here.
Smart ÜNB-Marketing instead of direct marketing for small installations
It is not necessary and also not economically sensible to reduce the limit of a direct marketing obligation from 100kW, as is currently planned by the BMWK. The expenditure for the marketing of surplus electricity from small installations increases disproportionally for direct marketing. It is substantially more efficient for the forecasts and the sale of electricity from fixed installations through the ÜNB. It makes little sense to allow cheaper EEG-electricity with a set feed-in tariff onto the market at extremely negative prices at a cost to the taxpayer, as has been the case. Especially as this would worsen the conditions of the directly market installations. Even old installations, which are still entitled to a share of the premium market at negative prices, record economic losses at spot-prices which are so small, that they overcompensate for the monthly market premium. In hours with negative spot-prices no entitlement should be given to new installations to the feed-in tariff and they should be able to be regulated from network operators except for their own consumption.
Smart ÜNB marketing is necessary regardless, as in the future private and industrial new installations will be below a reasonably workable threshold for direct marketing. The call for a direct marketing obligation for all PV-installations is unfounded, regardless. Direct marketing must first its trial with larger installations. Here, too, legislators will not be able to apply the hope principle, but rather will have to make operators and direct marketers more accountable.
There is therefore no reason that the setting up of small PV-installations will not continue to be possible. They are the best security against incalculable electricity prices and make economic sense due to their closeness to operators. With plug-in solar and batteries (commonly known as balcony solar and batteries), this is also possible for many rented and condo apartments.
In new residential constructions, fossil-fuelled heating systems have now become a marginal phenomenon.
Share of heat pumps in heating sales is growing
A further media phenomenon is the allegedly growing public scepticism against heat pumps. The fact that this scepticism exists is undisputable. The claim that it’s growing however, contradicts the sales trend. As the total sales of heating in the last years has been heavily influenced by the energy price crisis from Russian aggression against Ukraine, one should pay attention to the relative numbers.
The Bundesverband der Heizungsindustrie (Federal Association of the German Heating Industry) regularly publishes the sales figures of different heating systems (natural gas, oil, heat pumps, biomass)7. The share of heat pumps in the total sales figures of heat generators continues to increase. In 2020 that share was 14.3% (120,000 of 842,000), in 2023 already 27.2% (356,000 of 1,308,500). In the months from May until September of 2024, the share of heat pumps was on average 30%.
Weak sales numbers at the start of 2024 were especially linked to the rocky subsidy policies of the BMWK. In contrast to political proclamations, the federal funding was changed in terms of content and process (from the Federal Office for Economic Affairs and Export Control to the KfW investment and development bank) in the winter. Due to the hole in the federal budget following the ruling of the Federal Constitutional Court, there are further delays. It was not until 27th February 2024 that owner-occupiers of single-family homes were able to apply for funding again as the first group of applicants. The final group followed in August 2024.
Consequently, the subsidy commitments for heat pumps were: Zero in January 2024 and only 1738 in February 2024. By September 2024 however, there were already 15000 funding approvals for refurbishments8. Efficient air-to-air heat pumps that directly heat in the open air and transfer that heat to rooms are also eligible for subsidies. Commercially they are generally referred to as air conditioning units. They are often more affordable to install and are suitable as an extension of an existing heating system. In the federal funding, their share is currently over 25%, but they are not included in the statistics of the Bundesverband der Heizungsindustrie.
Meanwhile, fossil fuelled heating has become a side issue in new properly developments. From January until July 2024, almost 64% of newly erected residential buildings were fitted with heat pumps as the primary heat energy source. A further 24% use district heating. Less than 6% are heated with gas or oil – in 2020 it was still a third9.
Waiting on district heating or hydrogen?
The ongoing communal heating planning continues to be named as a reason as to why investments in heat pumps are being delayed. The shift from local and district heating networks is only economically viable in contrast to decentralised solutions if there is enough demand density. Additionally, except for urban areas or densely populated village centres, this is generally not the case. In most cases it is already possible to predict whether a heating network will be expanded, even if communal heating plans have yet to be finalised. In case one is mistaken here and has nevertheless invested into a warm pump, there are good prospects for protection. A legal opinion for the Bundesverband Wärmepumpe argues that you cannot be made to connect to a heat network10. In some federal states, this has already been legally clarified.
While heat networks could be an alternative to climate-friendly heating, one should never hope for green hydrogen for heating. Physics is against this: while through heat pumps three kilowatt-hours (kWh) of heat warmers could be generated from one kWh of electricity, while optimistic projections for hydrogen is just two thirds kWh. The share of the generated electricity costs therefore differs by a factor of 4.5 and this result will not noticeably improve for reasons of natural law.
Sources:
- Monatliche Ausbaustatistik für Erneuerbare Energien der Bundesnetzagentur: https://www.bundesnetzagentur.de/DE/Fachthemen/ElektrizitaetundGas/ErneuerbareEnergien/EE-Statistik/start.html ↩︎
- BMWK-Studie „Analyse der Ansteuerbarkeit von elektrischen Erzeugern und Verbrauchern“ des Fraunhofer IEE: https://www.bmwk.de/Redaktion/DE/Downloads/Studien/analyse-der-ansteuerbarkeit-von-elektrischen-erzeugern-und-verbrauchern.pdf ↩︎
- Hochrechnung der Produktion von Solar- und Windenergieanlagen mit fester Einspeisevergütung: https://www.netztransparenz.de/de-de/Erneuerbare-Energien-und-Umlagen/Freiwillige-Ver%C3%B6ffentlichungen/Wind-und-Solarenergie-Hochrechnung ↩︎
- Anlagen in der Direktvermarktung: https://www.netztransparenz.de/de-de/Erneuerbare-Energien-und-Umlagen/EEG/Transparenzanforderungen/Ausfall-und-Direktvermarktung ↩︎
- Statistik stationäre Batterien: https://www.battery-charts.de/ ↩︎
- Zahlen zum EEG-Finanzierungsbedarf: https://www.netztransparenz.de/de-de/Erneuerbare-Energien-und-Umlagen/EEG/EEG-Finanzierung/EEG-Finanzierungsbedarf ↩︎
- Absatzzahlen der Heizungsindustrie: https://www.bdh-industrie.de/presse/pressemeldungen/artikel/absatz-von-heizungen-stark-ruecklaeufig-waermewende-stagniert ↩︎
- Monatliche Antragsstatistik des BMWK zur BEG-Heizungsförderung: https://www.energiewechsel.de/KAENEF/Redaktion/DE/PDF-Anlagen/BEG/beg-antrangszahlen-2024.pdf ↩︎
- Entwicklung der Beheizungsstruktur im Neubau nach Baugenehmigungen: https://www.bdew.de/service/daten-und-grafiken/entwicklung-beheizungsstruktur-baugenehmigungen/ ↩︎
- Rechtsgutachten zum Anschluss- und Benutzungszwang: https://www.waermepumpe.de/politik/uebersicht/kommunale-waermeplanung-fernwaerme-und-waermepumpe/ ↩︎