Local situation
Although grids in Spain and Portugal are connected to each other, they have limited contacts. The only sources of external force up to the grid come from France and Morocco, which are small contacts, but they can be used to help start some plants. Both blackout countries have significant hydropower, with Spain covered 10 % of its demand and Portugal 25 %. This is useful because hydro plants need very little in the way of external power supply to start operating.
Beyond, the two countries have invested a lot in renewable sources, Portugal closed its last coal plant in 2021 and closed its last coal plant. Spain has currently received about 40 % of his electricity from renewable sources.
The grid is not an ideal source of solar energy to start black, provided it is not available for a significant part of the day. But the solar panels directly produce the current, with the electronic systems that match the alternative of the grid. With the right electronics, it can play a key role in keeping the frequency stable as the grid classes are reproduced. In productive areas, air can provide black start power to other plants, and it does not require much external force to start work. However, it is unclear whether the local wind hardware is equipped with black launch, or if the local weather will cooperate (quick examination of the weather in different cities suggests that it is relatively calm calm).
The batteries have the ability to be incredibly helpful, as they also provide direct currents that can be used for launching power plants or for frequency stability as the grid sections are brought back online. Unfortunately, no country has yet installed a grid scale battery hardware. It is expected that dramatically expanded solar energy will change in parallel in the next few years. But, at this time, the batteries will not help greatly.
Regardless of how grid operators manage to handle this work in Spain and Portugal, they are currently facing a memorable challenge. If you are seeing several days of estimates to restore power, the reason is that failing to meet the challenge will leave things in which they are still present.