I look forward to the day when renewables provide >90% of our energy, and old men on the Internet are still bloviating that it can't be done. As for me, I'm looking at pallets of solar panels on eBay to expand our PV system.
We're not waiting on anything groundbreaking, no heroic technologies are needed. There is no magic. It's just a matter of manufacturing/install capacity and funds. It's like insulation for buildings: not sexy, but it works and it's a known quantity. Work backwards from first principles based on how much energy the Sun delivers to the planet.
US: https://gspp.berkeley.edu/faculty-and-impact/news/recent-new...
Australia: https://www.sciencedirect.com/science/article/pii/S036054421... | https://doi.org/10.1016/j.energy.2017.05.168
Europe: https://www.energyplan.eu/smartenergyeurope/ | https://www.irena.org/publications/2018/Feb/Renewable-energy... | https://www.sciencedirect.com/science/article/pii/S030626191...
Central/South America: https://journals.plos.org/plosone/article?id=10.1371/journal... | https://doi.org/10.1371/journal.pone.0173820
(if anyone has other resources for geographies I didn't mention, please comment with them to contribute to the knowledge graph!)
Why would this be necessary except in extreme environments (which don't exist in Germany)?
If solar produces 0 watts in Germany for an entire month we're all dead anyways.
Right now https://app.electricitymap.org/zone/DE as an indication, Germany is at around 30% production of their solar capacity.
At the end yeah you can get out of all of these issues by building 10x the required capacity, but that is reflected on the price and the space to build all of this though.
First there is a bit stability issue: when a load start to consume (zero feed in or on-battery/autonomous scenario) the solar inverter demand time (seconds!) to ramp up, when the load stop the solar inverter still feed too much power and we do not have ready available "super-condenser" (when a load pops-up) and "energy sponges" (when a load stop), the result is a not stable microgrid. IF we have a large enough grid where spike loads are not really spike than perhaps we can have stability but such kind of grid for solar and wind it's not there, the so called "smart grid" do exists only on paper.
Secondly all p.v. systems I know are sold as commercial product, but they prove to be more like initial prototypes, to make the microgrid stable software is much used, and in general it's correct name should be crapware. ModBUS RTU is the most monitoring-and-control universal protocol, in most cases with a crappy load of various kind of "bridge" (generally from classic serial to USB or to TCP) and being pull-based it's normally not suitable at microgrid scale. CanBUS is used for quicker communication and is used much like car's ODB: there is a standard, but almost all vendor "extend" it as they wish so interoperability is crappy. Even the most open of the p.v. systems I know of (Victron, witch base it's system on Debian and publish all the code) is an incredible pile of python glue code and scripts that can't be really considered "production ready". All such systems also are designed to live connected to the OEM, some are even hard to use without internet connectivity to their "home". Some even have hard-coded passwords with non-deactivable wifi, hard-coded per entire model series, like BYD batteries, an ideal target for a casual wardriver.
First: something can be "stored", for instance I have enough hot water to heat it just with solar (as long as there is enough day-to-day production), that's very good and ultimately easy, it's just about have enough space for a big boiler. Electricity on contrary can't be stored much: batteries are hyper-expensive and do not really last that longer. Most stressed batteries last 5 years, most 8 years, few perhaps can arrive at 10 but I'm not much convinced. Long story short, there is enough tech to power up few homes, built with proper insulation and implants etc to run that way, there is almost nothing at industry demand scale, not even to made such systems themselves.