Reliability of data

fuzzy · Post by **fuzzy** » 27 Nov 2017, 01:15

I am always skeptical of IT supplied info, since you are at the mercy of unknown software and systems. At 1.10am GMT, this site:

http://clivebest.com/rgraph/Wind.html

claims we are using about 2.2 GW of solar power in the UK.

Once we see an error, why should we assume any of the other data is valid?

Post by **adam2** » 27 Nov 2017, 04:27

I have more faith in the data on the gridwatch site, the figures generally seem to be consistent with common sense and with that which would be expected.
Glitches and errors have been known on the gridwatch site, but are usually obvious if one views the site regularly and gets a feel for what may be expected.

If I quote figures on these forums, I generally mean figures from gridwatch unless stated otherwise. If I quote a figure from any published source, but have reason to doubt the accuracy thereof then I always make this clear by use of wording such as "reported as XYZ, but which looks like a mistake to me"

PS_RalphW · Post by **PS_RalphW** » 27 Nov 2017, 06:59

Overnight wind was the biggest single source of power. About 9.5Gw, more than coal and gas combined.

Mr. Fox · Post by **Mr. Fox** » 28 Nov 2017, 21:58

Source for the PV data is Sheffield Uni:

https://www.solar.sheffield.ac.uk/pvlive/

The Sheffield figure is only a model and based on a limited sample - seems offline, anyway.

That said, Clive Best's data doesn't tally with theirs, so I think his site is broken.

There is no UK wide PV SCADA system (nor will there be), afaik, so any figures you see will be extrapolated from installation records. Same for small wind.

Gridwatch (and others) use "Balancing Mechanism" Reports (for non-PV), which is real(ish)time grid data: https://www2.bmreports.com/bmrs/?q=eds/main

- straight from the horse's mouth, as it were.

Post by **clv101** » 28 Nov 2017, 22:17

Mr. Fox wrote:There is no UK wide PV SCADA system (nor will there be), afaik, so any figures you see will be extrapolated from installation records. Same for small wind.

Yeah, which is problematic as many installs are not performing as well as they might, trees grown causing shade, panels become dirty, some aspect of the system broken and not repaired...

That said, there are also a lot of PV systems that aren't on the installation record. I've had a 1.62kW system running since the spring, generated some 600kWh that no one has counted. I'm in the process of installing a 6.5kW system, similarly off the books.

Post by **adam2** » 29 Nov 2017, 00:29

PS_RalphW wrote:Overnight wind was the biggest single source of power. About 9.5Gw, more than coal and gas combined.

Are you certain that it was that high, on the gridwatch site ? If so then a new record has been set.
The highest recorded wind power that I have seen is 8.94 GW, this could of course have been exceeded when I was not looking ! The chart or record on gridwatch has too low a resolution to show the difference between 8.94 and 9.5.

vtsnowedin · Post by **vtsnowedin** » 29 Nov 2017, 08:54

clv101 wrote:
Mr. Fox wrote:There is no UK wide PV SCADA system (nor will there be), afaik, so any figures you see will be extrapolated from installation records. Same for small wind.
Yeah, which is problematic as many installs are not performing as well as they might, trees grown causing shade, panels become dirty, some aspect of the system broken and not repaired...

That said, there are also a lot of PV systems that aren't on the installation record. I've had a 1.62kW system running since the spring, generated some 600kWh that no one has counted. I'm in the process of installing a 6.5kW system, similarly off the books.

All that uncounted renewable power will eventually show up as reduced demand for traditional sources.

Post by **adam2** » 29 Nov 2017, 10:44

Indeed, this may be the reason that indicated demand has fallen in recent years.
All large electricity suppliers into the grid are metered in real time and the data appears on the gridwatch site.

Most PV is NOT metered in real time, the given figure is an estimate based on metering a small number of hopefully representative examples and then extrapolating. Note that the error between estimate and actuality could be positive or negative.

All large wind farms are metered in real time and the result displayed on gridwatch. Small grid connected wind turbines are not real time metered and are not included. Therefore the figure given for "wind" is CERTAIN to be LESS than the actual total production.
The degree of under reporting is open to debate, but must exist.

There is also a relatively small amount of private fossil fuel generation that is not metered in real time and therefore not reported on gridwatch. This also would show up as a reduction in indicated demand.

Post by **adam2** » 01 Dec 2017, 16:02

A good example of unreliable data occurred yesterday on the French gridwatch site.
At about 22-00, the indicated production from nuclear and other sources declined to a fraction of normal, as did the indicated demand.

This COULD happen in the event of some very unlikely grid failure, but in this case common sense wins !
If it HAD happened, much of France would have been blacked out. This clearly did not happen or it would have been widely reported.
Also, the indicated nuclear production recovered in an hour or two, nuclear plants do not re start that quickly.

fuzzy · Post by **fuzzy** » 10 Dec 2017, 10:04

While I'm asking about data, anyone know how our gas storage is nowadays?

Post by **adam2** » 10 Dec 2017, 12:39

fuzzy wrote:While I'm asking about data, anyone know how our gas storage is nowadays?

I have just posted about this in the long running "gas" thread. Here.

http://www.powerswitch.org.uk/forum/vie ... 206#288206

Post by **adam2** » 23 Jan 2018, 13:04

The gridwatch site is not working correctly at present, about 13-00 on 23/01/2018.

The figures have not changed for an hour or two.

This shows the importance IMO, of not relying on this or other sources of data without applying a "common sense test"

A quick look at the site could be misleading, but a more in depth look suggests that it has failed to update for some hours.
Both total demand, and CCGT output fluctuate almost continually, but have remained unaltered on the website.

woodburner · Post by **woodburner** » 23 Jan 2018, 19:34

Does the line at the bottm saying when the data were last recorded have any reliability?

Post by **adam2** » 23 Jan 2018, 19:57

woodburner wrote:Does the line at the bottm saying when the data were last recorded have any reliability?

Don't know, because I forgot to look at it.
Will observe next time.

Post by **adam2** » 14 Mar 2018, 11:00

Dodgy data on gridwatch at present, PV is showing as zero, which is clearly incorrect during daylight.
Total demand also looks suspiciously low for time/day/weather.