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From engineering standpoint it is not an easy task to balance random load that comes and goes from solar, centralized solar plants is one thing but panels on the roof is another. While electricity is abundant running the grid is not such an easy task as it may seem. So this might explain why there is such push back from utility companies against uncontrolled user solar devices connected to their grid.

what does "balance the random load" mean in an engineering context? i would have thought electricity would balance itself?

Solar does weird things to the baseload.

Before solar, utility companies would install baseload plants (nuclear, coal, AFAIK) which output power at a constant rate for cheap. The idea is that your baseload plants would provide power right up to the trough of the demand curves.

Solar causes that trough to deepen but doesn't get rid of the peaks (see duck curve). That forces power companies to close down baseload plants, but add peaker plants (usually natural gas) which are generally more expensive to operate.

This is where grid storage enters for a green grid. It brings two benefits, it can raise the demand trough making baseload plants attractive. It can also drop the demand peak, decreasing the need for additional peakers plants.

The problem is that we don't have a lot of viable storage options. Best case for a region is having a lot of hydro available. Pumped hydro would make sense, but there aren't many places where you can install it (it requires a lot of water, land, local buy-in). Batteries work, but have cycle limitations. You could do flywheels, but they are expensive for the power stored. Heck, one even seen "fill a pit with gravel, heat it up, boil water during peaks to generate power". Which may make sense, particularly for colder regions where that heat could also heat housing.

This little gem has been exceeding expectations from the day it went into service: https://www.bbc.com/news/world-australia-42190358

Electricity absolutely does not balance itself. Passively, the energy that goes into the grid must come out somewhere.

Electrical utility companies manage this with two major levers:

1) Standby power plants, that are running but not producing at full load. The plant load is actively adapted to the monitored needs of the grid.

2) Hydroelectric storage, to soak up excess production, where hydroelectric dams with secondary reservoirs are available.

Grid load management is very much an active process, not a passive self-correcting one.

To add to this, when too much energy is fed into the grid, the net frequency increases slightly. Thus, the control variable is net frequency. There is lots of research on this problem.

When the net frequency increases so does the rotating speed of all turbines. The inertia of those turbines is one way how excess energy is buffered.

I'm no electrician myself, but I know that it's not easy to generate a really good sine wave with a constant frequency and match it to the grid.

While electronic componentes are making big steps in that direction, "classic" mechanical generators are still superior for this as they are running very constant.

That's why lots of people fear that solar panels with their sudden power generation (as in "clouds are gone, let's bring it on!") might be a danger to the grid as they are fluctuating quite a bit.

It's definitely a variable, but in the UK "domestic" sizing is up to 4kW. I can induce the same variability in the grid by making a cup of tea with an electric kettle.

You mean the sizing of solar panels? I think in Germany it's higher, at least my landlord spoke about something like 25 kW, but I'm not totally sure about that.

I take it to mean that sometimes you have lots of energy coming in (during daylight for example), then suddenly very little (during nighttime). Weather can affect it also.

So to balance the supply of electricity to customers you need a way to make sure there is an not too much and not too little.

Many years ago in Britain, it was predictable that at the end of the TV show Eastenders, people would all go to turn on their kettle for Tea. The surge was so big that someone had to monitor when the programme ended and initiate the additional supply of electricity to meet demand. That supply even had electricity from France as a backup.

I recall an interview where they had that energy available from a Hydroelectric Power Station where they could release the water and get an instant source of electricity.

All for tea.

[1] https://www.forbes.com/sites/quora/2017/09/06/britain-turned...

[2] https://www.geek.com/geek-cetera/tea-time-in-britain-causes-...

I interpreted the term “random load” to mean unpredictable supply given variable external factors like specific locations’ weather.

Edit: fixed wording

Random as in being many many houses with different setups that themselves consume power differently/ have differing logic when to dump extra power. Therefore despite there being roughly same weather in the area each house has different levels of extra power it can dump.

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