I found a way to emulate this.
Explanation:
The trick is the placing of the accumulator! You need to place the accu in two networks - you see how I hover it with the mouse.
It is in the main circuit and in this small circuit with 3 poles on the right.
This accu keeps the small net "on-line". It is not much power needed: The thing on the top is the controller. There are about 10 woods cycling round and round. In the chest are always between 4-5 woods.
The control-accu covers only this inserter and the three lamps with energy!
So this is how it works: In the night, all accus get unloaded. But the control accu unloads much faster, because he is in two networks. See the info on the right: The accu begins to unload and is about 80% empty. All others only about 95%. The sense of the lamps is, that they need more energy and so they unload the control-accu a even little bit faster.
When the accu is empty, the control inserter stops. But the others are working on. The slow output inserter puts all wood out of the chest and the big switch on the left is turned on: All coal is put on the belt! The fast belts are needed here, because the way down to the steam engines is otherwise too far and I don't wanted to rebuild everything. This is also the usage for the other coal belts down, I put an inserter directly before the kettles to avoid situations, where the engines don't restart themselves and for that as much coal as possible is needed. I tried it this way, but see down!
When all steam engines have full power, the accus are about 20% full. The discharging is stopped.
Pro:
Works really great! I reduced the coal needed from about 1000 every day down to 50 or so...
Not too complicated to build
Cons:
No cons found, this is a really cool idea.

It's a little bit tricky to tune this right: As mentioned you have the lamps but also the number of wood and you can program, when the smart inserters should begin to work (You have minimum 4 woods in the chests here. This means, that you can either say "work when < 4 wood" or you can lower this. Then, because the normal inserter moves a wood per second, you have 4 seconds before it begins to work. In this case this is very much time and not needed.
I found no way to spare the second smart inserter, cause when you try it with only one, you have to set him so, that the poles are automatically connected.
Tip: Too long till the coal gets down to the kettles! I recommend to replace the kettle-inserters with smart inserters and switch them on with this controller, this would be an immediate reaction.