Coronavirus, effects on electricity supply.

[vtsnowedin]

Update here,
https://www.bbc.co.uk/news/technology-52331534

Total demand has fallen, but daytime use has increased.

"Households are consuming 21% less electricity than usual at 07:30, as fewer people commute to work, and are taking back the time to sleep later instead," a spokeswoman for Bulb Energy said, based on data from more than 2,000 smart meters.

Having taken back this time they may be reluctant to have it taken
away again.

Reluctant yes but I can tell you from working summers with winters off, semi retired, that it only takes about three days of getting out of the house on time to get back to your old habits. It does take longer as you pull out of the driveway at daybreak to not ask yourself "do I really want to do this? My answer is not really but I want the money and drive on.

[Potemkin Villager]

Motivation in going to work I suppose depends on if you must to meet basic financial needs or if you may to provide for "extras". Of course if your habitual source of employment goes tits up permanently that is another matter.

I find it interesting how electrical consumption mirrors social changes (and changes in the weather) . A renewable energy project I installed many years ago featured a logging KWh demand system for the whole site, a sort of attempt at a "smart" energy meter. It was easy to spot who had good and bad timekeeping, which enterprises were running flat out and which were not. It also allowed us to spot the "secret" under desk electric heaters that appeared the first winter the district heating scheme was tried and found wanting.

[adam2]

One reactor at Sizewell B has been shutdown at the request of the national grid, due to the virus induced reduction in electricity demand.

https://theenergyst.com/national-grid-c ... -to-panic/

[PS_RalphW]

Strong winds, bright sun and the lowest peak demand of just 28GW yesterday that I have ever seen. NG was down to 3GW

[Potemkin Villager]

One reactor at Sizewell B has been shutdown at the request of the national grid, due to the virus induced reduction in electricity demand.

https://theenergyst.com/national-grid-c ... -to-panic/

“Great Britain relies on us to keep the lights on and I want to reassure everyone that we have robust plans in place to keep our system working throughout the coronavirus outbreak,� said ESO head of national control and chief engineer, (and UCD graduate) Roisin Quinn."

Fair play to her.

[BritDownUnder]

One reactor at Sizewell B has been shutdown at the request of the national grid, due to the virus induced reduction in electricity demand.

https://theenergyst.com/national-grid-c ... -to-panic/

“Great Britain relies on us to keep the lights on and I want to reassure everyone that we have robust plans in place to keep our system working throughout the coronavirus outbreak,� said ESO head of national control and chief engineer, (and UCD graduate) Roisin Quinn."

Fair play to her.

She looks much younger than the average 54 years of age for the average engineer in the UK, and, I suspect, gets paid a lot more than the average 24,000 pounds that the average British engineer gets paid.

Actually if she is a graduate of an Irish university then she is probably working there because the UK engineering graduates in short supply for the reasons given above.

[Potemkin Villager]

According to New Power Report May 2020, https://www.newpower.info/wp-content/up ... y-2020.pdf , weirder and weirder things are having to be done to maintain system stability with record low demand and record high renewable generation.

" National Grid ESO will start procuring a new ‘footroom’ product, ‘Optional Downward Flexibility Management’, on 7 May to help it manage the system during periods of very low demand.........

ODFM will pay providers to increase demand or reduce generation so that NGESO has enough generating assets in operation to maintain frequency and voltage control........

On Easter Monday, demand fell to15.2GW, compared to the previous record of 15.8GW. The system operator admitted it had not predicted such low levels: its prediction was 17.4GW, but it had overestimated consumer demand and underestimated the effect of warmer weather and embedded wind generation. With such low levels of demand, NGESO brought 17 generating units on line to maintain system stability, a level of intervention it would not normally expect until the June or July during summer lows.

The system operator is continuing to investigate whether it can source inertia from “non-traditional sources� – it usually calls on thermal plant with large rotating masses to provide the service – but said that work would not be implemented this summer."

[clv101]

The system operator is continuing to investigate whether it can source inertia from “non-traditional sources� – it usually calls on thermal plant with large rotating masses to provide the service – but said that work would not be implemented this summer."
[/i]

I read something about solar farms being able to offer this service, including at night, by using their inverter hardware.

[vtsnowedin]

The system operator is continuing to investigate whether it can source inertia from “non-traditional sources� – it usually calls on thermal plant with large rotating masses to provide the service – but said that work would not be implemented this summer."
[/i]

I read something about solar farms being able to offer this service, including at night, by using their inverter hardware.

I would think that would require major investments in battery banks to store the solar power to when needed.
That can probably be done eventually but it is not on line now so they have a current problem.

[clv101]

The system operator is continuing to investigate whether it can source inertia from “non-traditional sources� – it usually calls on thermal plant with large rotating masses to provide the service – but said that work would not be implemented this summer."
[/i]

I read something about solar farms being able to offer this service, including at night, by using their inverter hardware.

I would think that would require major investments in battery banks to store the solar power to when needed.
That can probably be done eventually but it is not on line now so they have a current problem.

No, not storing energy, but using the inverter hardware to provide 'inertia', can't remember the proper term, adam2 might be along soon...

Edit: This is what I'm thinking.

[vtsnowedin]

I read something about solar farms being able to offer this service, including at night, by using their inverter hardware.

I would think that would require major investments in battery banks to store the solar power to when needed.
That can probably be done eventually but it is not on line now so they have a current problem.

No, not storing energy, but using the inverter hardware to provide 'inertia', can't remember the proper term, adam2 might be along soon...

Edit: This is what I'm thinking.

Perhaps during the day when the panels are making power but after sundown the inverters would have nothing to invert unless there was a battery bank attached. Just my non electrical engineer layman thought. Will be happy to be shown wrong.

[clv101]

Forgot to add the link in my edit above!

https://www.pv-magazine.com/2020/04/06/ ... -controls/

[BritDownUnder]

Forgot to add the link in my edit above!

https://www.pv-magazine.com/2020/04/06/ ... -controls/

Looks interesting! From memory the traditional inverters were 'grid-following' meaning they could not provide control of the grid frequency by forcing the frequency to go faster or slower by some means. I suspect is something to do with the timing of the voltage on the inverter versus the voltage on the grid. These new 'grid-forming' inverters appear to have this ability. How a solar farm can do this at night I am not sure but maybe some kind of battery or capacitor storage is used.

In traditional rotating electrical machinery such as steam, gas or hydro turbines the frequency of the grid can be adjusted by increasing power, in effect pushing harder, to speed up the frequency and the opposite to reduce frequency. In engineering terms this is done by changing the magnetic field angle of your generator voltage very gradually with respect to the voltage angle of the grid.

How this is done by a 'grid-forming' inverter I am not sure. Maybe the voltage (and current) produced by the inverter is also changed with respect to the voltage and current on the grid. I am open to explanations on this.

In Australia the solution to lots of solar farms and their lack of 'inertia' has been to install synchronous condensers (a.k.a. syncons) to provide the necessary inertia and also some voltage control. These syncons are basically normal rotating generators that are freewheeling along with the grid. They don't actually generate any power under normal circumstances (they actually absorb some) but are useful in the event of faults.

Here is some information about syncons in Australia.

[adam2]

Forgot to add the link in my edit above!

https://www.pv-magazine.com/2020/04/06/ ... -controls/

I am very doubtful as to the utility of the ideas proposed in the above link.
Frequency on a grid system can only be increased by supplying more power, or by reducing the demand.
If a PV array is producing say 100Kw, then that will tend to very minutely increase the grid frequency, and I doubt that a "clever" inverter can improve on existing designs.
To improve stability means supplying extra power, beyond the installed PV capacity, if the frequency drops.
This could be done only if some ADDITIONAL source of energy, or energy storage is available. AND IF the PV grid tie inverters can handle this extra power, or if this extra power can be put into the grid by dedicated inverters, separate from the grid tie inverters.

Batteries are the obvious choice, and are already being applied.

[adam2]

There is a lot to be said for synchronous condensers for assisting with grid stability.
A synchronous condenser is basically a standard alternator, not mechanically coupled to a turbine or other prime mover.
It consumes electricity in order to supply the copper losses and the iron losses, and to over come friction in the bearings, and air friction.
For a large machine these losses sound a lot, but in percentage terms are relatively small. A 500MVA synchronous condenser might absorb about 1% to 2% to supply losses. Say 5 or 10 Mw.

By adjusting the field current, the power factor may be altered, hence the name synchronous condenser, since a similar effect is obtained to that resulting from connecting actual static condensers to the circuit.

In case of a sudden drop in grid frequency, then power can be supplied into the grid, thereby limiting the drop in frequency due to the inertia of the rotating mass. Only very short term, for about one second, as the rotating mass soon slows down to match the lower frequency. When the frequency increases, extra power is absorbed in order to increase the speed of rotation.
Fitting a large flywheel increases inertia and can assist for some seconds.