Earth Notes: A Note On Data and Graphs

Here is a selection of the data collected and used; I intend to organise and collect more of it here, and graph it (and the tools to graph it). Please say if there is anything that you'd like me to do sooner...

This also contains selected circuit diagrams/schematics.

16WW Data

I've collected much data for our house at 16 Willingham Way (16WW) referred to in the various documents on this site.

SAP and Air-Leakage

SAP cert extract

To set a baseline and understand better what needed fixing, I had SAP, air-leakage and other tests done in early 2009.

Tests/results/certificates by Tophouse 2009/03/30 for us were:

Grid-Tie PV Generation

Daily PV Output Since 2008

This data is collected a year at at time, though there is a chart for the whole data set, and collated daily kWh generation records with smoothing. (See the gnuplot commands.)

See the 2008 daily PV generation logs for 2008 as .csv and .png chart.

See the 2009 daily PV generation logs for 2009 as .csv and .png chart.

See the 2010 daily PV generation logs for 2010 as .csv and .png chart.

See the 2011 daily PV generation logs for 2011 as .csv and .png chart.

See the 2012 daily PV generation logs for 2012 as .csv and .png chart.

See the 2013 daily PV generation logs for 2013 as .csv and .png chart.

See the 2014 daily PV generation logs for 2014 as .csv and .png chart.

(See the gnuplot commands for annual plots, and the current awk 'V2' smoothing code ('V1').)

See other system performance records, including per-string outputs.

Intraday Data

Rob Ferber of ElectronVault wrote to me looking for intra-day generation data (with 10 minute sampling intervals), of which I had so far exposed very little because of data-cleanup issues (bizarre time offsets in the Sunny Beam apparently attempting to correct to German civil time even though I keep it on UTC, serial numbers, corrupt data, slight drift of Sunny Beam from true UTC, etc).

I capture these intraday samples manually after dusk about twice per month, and possibly on particularly 'interesting' days, of late using the SunnyBeamTool c/o Michaël Peeters on my SheevaPlug ARM Linux system. I don't do this continuously because I have not been able to stop the Sunny Beam drawing considerable power via the USB port, and because I do not currently have a 'spare' USB port: I disconnect the USB I/O board temporarily to connect the Sunny Beam.

Rob produced lovely tweaked graphs from my raw data up to September 2012. Thanks, Rob: great job!

Prior to Rob's analysis I had made public but not announced these intraday samples from SMA's Windows application, with no explicit time correction: 2008/03/24 2008/04/01 2008/04/09 2008/04/17 2008/05/08 2008/09/13 2008/09/14 2008/09/19 2008/10/11 2008/12/13 2009/03/15 2009/04/08 2009/05/11 2009/05/24 2009/06/29

The entire raw data set is now available, including new samples as I take them, though with many caveats (beware timestamp wobbles in particular).

PVGIS Prediction

Here is an extract of the numbers from the PVGIS estimate not knowing anything about our local trees, etc!

Solar radiation database used: PVGIS-classic
Nominal power of the PV system: 5.2 kW (crystalline silicon)
Estimated losses due to temperature: 7.3% (using local ambient temperature)
Estimated loss due to angular reflectance effects: 4.1%
Other losses (cables, inverter etc.): 14.0%
Combined PV system losses: 23.5%

Fixed system: inclination=23°, orientation=-90°
Jan 2.7886.00.7322.6
Feb 5.361501.3437.4
Mar 8.832742.1666.8
Apr 14.404333.57107
May 17.805524.51140
Jun 18.205454.65140
Jul 18.205644.69145
Aug 15.604834.02125
Sep 10.703222.7281.7
Oct 6.572041.6751.7
Nov 3.431030.8926.8
Dec 1.9460.10.5216.2
Yearly average 10.3 315 2.63 80.0
Total for year 3780 960

Ed: Average daily electricity production from the given system (kWh)
Em: Average monthly electricity production from the given system (kWh)
Hd: Average daily sum of global irradiation per square meter received by the modules of the given system (kWh/m2)
Hm: Average sum of global irradiation per square meter received by the modules of the given system (kWh/m2)

Meter Readings

Monthly meter readings and comments.

Gas Consumption

Monthly Gas Consumption Since 2007

Gas consumption for hot water, central/space heating, and cooking, (manually) converted to monthly kWh/d figures, suitable for gnuplot to digest. (See the gnuplot commands.)

Yearly Gas Consumption Since 2005

Annual gas consumption in kWh, suitable for gnuplot to digest. (See the gnuplot commands.)

Gross Electricity Consumption

Monthly Electricity Consumption Since 2007 (gross)

Gross electricity consumption, ie compensating for microgeneration from PV, as if the PV were not there, in monthly kWh/d, suitable for gnuplot to digest. (See the gnuplot commands.)

Yearly Electricity Consumption Since 2005 (gross)

Gross annual electricity consumption in kWh, suitable for gnuplot to digest. (See the gnuplot commands.)

Footprint From Electricity and Gas

Yearly E+G Carbon Footprint Electricity and gas (eg heat+light) annual carbon footprint in kgCO2e, suitable for gnuplot to digest. (See the gnuplot commands.)

Heating Degree Day Data

Partial monthly summary of local HDD12 (base temperature of 12°C) data suitable for gnuplot to digest.

See annual data too.

Off-grid Battery Voltage/State

Battery Voltage

I log some aspects of my off-grid system such as live values for voltage, calendar month chart, and historic stats.

(See the gnuplot commands for live voltage plotting.)

Water Mains Inlet Temperature

Measured at kitchen tap in fast-flowing stream with probe up inside tap but tip not touching anything if possible, with typically upwards of 20s wait until readings steady before value taken.

19°C 2008/08/30 11:00 UTC approx
14°C 2008/11/19 08:36 UTC
10°C 2008/12/03 19:00 UTC
17°C 2009/06/02 10:00 UTC
20°C 2009/06/27 20:47 UTC
20°C 2009/08/30 11:00 UTC
16°C 2009/10/22 12:25 UTC
11°C 2009/12/07 10:00 UTC
10°C 2009/12/15 12:00 UTC
6°C 2010/01/09 21:12 UTC
8°C 2010/01/20 07:38 UTC
10°C 2010/04/03 10:38 UTC
13°C 2010/04/25 15:00 UTC
15°C 2010/05/23 11:00 UTC
19°C 2010/06/26 11:46 UTC
21°C 2010/07/17 10:00 UTC
19°C 2010/09/12 16:15 UTC
15°C 2010/10/18 11:03 UTC
15°C 2010/11/06 16:40 UTC
11°C 2010/11/28 19:00 UTC
9°C 2010/12/03 08:42 UTC
8°C 2010/12/20 10:10 UTC
The temperature of water going to homes from reservoirs in the Thames Valley and London has dipped to a record low, officials have revealed. Thames Water said due to freezing weather water had cooled to a "staggeringly chilly" 1.8C. Until now the coldest water temperature recorded was 4.9C in 2001 - the average is 7.3C.
8°C 2011/01/01 17:26 UTC
9°C 2011/02/14 10:25 UTC
11°C 2011/03/28 08:37 UTC
12°C 2011/04/09 17:15 UTC
17°C 2011/05/27 20:07 UTC
18°C 2011/06/21 16:30 UTC
20°C 2011/07/04 09:08 UTC
20°C 2011/08/13 10:10 UTC
19°C 2011/09/10 12:00 UTC
15°C 2011/10/23 16:25 UTC
15°C 2011/11/09 22:00 UTC
13°C 2011/11/27 14:30 UTC
10°C 2011/12/12 14:20 UTC
10°C 2011/12/28 10:25 UTC
11°C 2012/01/15 13:20 UTC Temperature higher than previous even though outside temperatures have been much closer to freezing for several days.
10°C 2012/02/01 19:30 UTC Outside temperatures again around freezing for several days.
9°C 2012/02/08 09:00 UTC Outside temperatures again around freezing for several days.
12°C 2012/04/09 08:15 UTC
18°C 2012/05/28 06:06 UTC
19°C 2012/06/30 18:23 UTC
19°C 2012/07/09 09:30 UTC
22°C 2012/08/19 15:00 UTC Measurement taken by Ellie; alternating between 21 and 22.
16°C 2012/10/08 06:26 UTC
15°C 2012/10/14 16:12 UTC
14°C 2012/10/28 18:20 UTC
13°C 2012/11/15 18:53 UTC
11°C 2012/11/30 12:00 UTC Reading alternating between 11 and 12. Outside below freezing overnight.
9°C 2012/12/15 08:45 UTC
10°C 2012/12/31 12:00 UTC ~11°C outside.
10°C 2013/01/06 18:13 UTC ~8°C outside.
10°C 2013/01/15 12:15 UTC ~2°C outside.
8°C 2013/02/15 11:52 UTC ~8°C outside and sunny.
9°C 2013/03/15 11:53 UTC ~7°C outside.
9°C 2013/04/05 17:42 UTC ~7°C outside; has been a very cold March.
10°C 2013/04/15 11:00 UTC ~14°C outside.
14°C 2013/05/15 13:00 UTC ~11°C outside.
16°C 2013/06/15 16:00 UTC ~16°C outside.
21°C 2013/07/15 13:15 UTC ~27°C outside.
22°C 2013/08/11 08:50 UTC ~17°C outside.
18°C 2013/09/15 11:05 UTC ~13°C outside.
16°C 2013/10/17 12:34 UTC ~16°C outside.
10°C 2013/11/15 18:53 UTC ~7°C outside.
11°C 2013/12/08 09:52 UTC ~7°C outside.
11°C 2013/12/15 11:47 UTC ~11°C outside.
12°C 2014/01/15 21:25 UTC ~10°C outside.
9°C 2014/02/15 12:00 UTC ~10°C outside.
11°C 2014/03/15 09:40 UTC ~10°C outside.
14°C 2014/04/14 12:00 UTC ~14°C outside.

all 4 traces for first fortnight or so

Local Temperature Monitoring

See a graph of local internal temperature at 16WW collected from an OpenTRV unit tethered to the Web server.

iButton Temperature Monitoring

See: A Note On iButton Temperature Logging of Insulation Performance.


I look up the offer at MyJoulo to place a small widget on top of my thermostat for one week to analyse our heating. Our unit arrived 2012/12/17 and ran until Christmas Eve.

See the generated analysis page (local copy) and the raw CSV data. (Also note that this sensor was about 2m away horizontally from button 3 in the iButton mission 5.)

snippet from temperature graph

The take-home message from the analysis is that it believes that we have our living room at the average UK 19°C and that our living room temperature varies between about 16°C and 21°C generally in a sawtooth pattern. (Note that 18°C in the morning before school seems to suffice.)

Note that from early evening 2012/12/19 I lowered the radiator flow temperature from about 60°C to about 45°C, independently of this, to see if the i30 PRC/eTRV could work with a lower heating rate. The reduced flow temperature seems to help reduce overshoot both in the target bedroom and in the living room, though the motivation was to try to test at typical heat-pump temperatures.

Note that we don't leave our house thermostat in the living room alone; we keep it lowish unless we feel cold and/or we want to force the heating on for the children's bedrooms before they go up. The latter action would be unnecessary if we had zoning with each bedroom able call for heat independently and those wasteful and soporific peaks >19°C could probably be trimmed. In the interim we should probably make sure that we get the thermostat down to ~18°C as the children go to bed to minimise overshoot.

A friend has generously provided his raw CSV data and chart too (from somewhat east of London), for comparison. In his case there is evidence of much tighter temperature control, at a similar mean level to ours, even with lower external temperatures.

Temperature and Relative Humidity Data from Thermal Discomfort Study

At the end of 2012 I participated in a UCL Energy Institute/LoLo study on responses to thermal discomfort, in return for access to the raw data collected by them on temperature and relative humidity at 16WW, which overlaps with some of my iButton mission 4 data collection.

Three draught plots (based on the sensors at 4 heights in each room):

were made available first, right at the end of the year. (The visible codes are: C04 Bedroom, C05 Living Room, C06 Kitchen.)

See the underlying raw data (note the room codes above on the filenames) in Mac .csv file format (with lines CR terminated, not CRLF or LF), c/o Stephanie Gauthier of UCL whose project this was for, here.

Relative Humidity

This is bound to be a fairly random sampling initially, until I find out what is relevant to measure and when.

Kitchen Living Room Front Bedroom Bathroom Outside Notes
Date/Time °C%RH °C%RH °C%RH °C%RH °C%RH
2010/09/12 16:15 UTC 2243 2340 2341
2010/09/13 16:45 UTC 2267 2263 2165 2166 2378 Dull and chilly and spotty rain outside.
2010/09/15 18:00 UTC 2183 Warm bath in progress.
2010/12/24 14:45 UTC 1573 In small bedroom after running dehumidifier ~2h: 15°C, ~50%RH.
2011/12/21 12:50 UTC 16.875.6 Immediately after completion of installation of MHRV in bathroom, after the windows have been open all morning on an overcast and damp day.
2011/12/21 17:43 UTC 15.985.2 With six people in the house (including two small children running around) and some cooking, the fan cut in, so I adjusted it a little so as not to come on until ~85%RH.
2011/12/21 18:41 UTC 18.092.9 Bath run, children in it, fan on boost, and RH staying below 100%, so no condensation on mirrors, though some on the window. After a few minutes the RH was dropping a little (to ~90%) and the temp rising (to ~18.4°C).
2011/12/22 09:30 UTC 19.981.7 Fan has been running for a few minutes after being completely off all night; no windows open.
2011/12/22 12:41 UTC 17.479.2 External air temp ~15°C, fan running on low, central heating off.
2011/12/22 13:44 UTC 17.377.3 Fan running on low, central heating off.
2011/12/22 18:51 UTC 17.783.8 Fan running on low, supper finished (ie cooking), external RH ~85%.
2011/12/23 07:30 UTC 16.786.3 11 Fan running on low all night, ~11°C outside, some (but not much) condensation on bedroom windows.
2011/12/23 15:00 UTC 20.1>95 After an hour's hot bath with the fan managing to keep the room from customary steaminess.
2011/12/24 09:50 UTC 15.376.0 4 Fan running on low all night, ~4°C outside, some condensation on bedroom windows.
2011/12/27 13:30 UTC 13.573.1 House unoccupied since about noon on 24th, fan turned completely off at mains, external temperature ~10°C.
2011/12/27 19:27 UTC 17.465.3 Have had central heating on at ~16°C.
(cont) Kitchen Living Room Front Bedroom Bathroom Outside Notes
Date/Time °C%RH °C%RH °C%RH °C%RH °C%RH
2012/01/06 12:00 UTC 16.280.4 776 Fan on low, incoming air 14.7°C; ~7°C and 76%RH outside. In small rear bedroom (boy's) at 12:40, 17.2°C and 71.4%RH.
2012/01/06 15:30 UTC 15.879.0 880 Fan on low, incoming air 14.9°C; ~8°C and 80%RH outside.
2012/01/13 11:30 UTC 14.664.3 15.665.4 15.667.8 690+ Windows had been open while MHRV was being worked on; outside ~6°C and 90+%RH. Kitchen measurements an hour later with laundry drying on clothes horses but portable dehumidifier operating for an hour. Kitchen warmed up, because rad had been on when people in there, but RH fairly constant over next few hours and dehumidifier extracted a a decent glassful of water. By 4pm bathroom was up to ~77%RH but with temperature little changed.
2012/01/13 20:15 UTC 19.656.5 Kitchen warm, humidity low even after some cooking, etc; laundry reasonably dry. Dehumidifier running about 9h at 180W (as previously measured) or ~1.7kWh, and removed ~1.5l of water from the air.
2012/01/16 18:30 UTC 19.063.2 18.264.1 17.471.9 16.076.4 370 MHRV running again since early this morning, crisp and close to freezing outside all day, and dehumidifier was running in kitchen much of the day to contain moisture from laundry drying. Rear small bedroom at 16.3°C/70.3%RH.
2012/01/31 22:30 UTC 19.158 080 Had put heating up to ~19°C in all upstairs rooms for afternoon with room doors open to encourage air circulation.
2012/02/01 07:15 UTC 16.358 14.363 080 Had front bedroom window open a crack (and breezy all night outside) to encourage air intake there and flow to bathroom; much less condensation there and on other bathroom windows than normally expected with this external temperature.
2012/02/10 15:30 UTC 17.055.6 18.550.5 16.960.5 15.964.4 152 Has been cold outside (around or below freezing mainly) and low RH for about a week now. (Readings taken over span from 15:30 (sunny) to 17:50 (after sunset) in order LR, K, FB, B with exterior temperature dropping to -1°C.)
2012/03/30 13:30 UTC 19.847.2 1655 Has been warm and sunny for several days and we've had windows open during the day (and the MHRV off except at night).
2012/07/09 09:30 UTC 22.764.5 22.561.5 22.363.7 22.165.8 1780 Some laundry drying in kitchen as damp and dark outside (has been a very wet three months) though internal %RH has been more typically 40--50.
2012/09/10 16:25 UTC 28.337.5 2545 Sunny and warm, patio door open!
2012/10/12 18:25 UTC 2062 2063 2066 1073 Testing two new temp/RH displays; I don't trust any to better than +/- 1°C/1%RH but otherwise good!
2012/10/14 11:07 UTC 1665 1667 1066 Now bright and sunny outside; had been near freezing overnight. After a long hot bath the bathroom temperature was up a couple of degrees, with the MHRV keeping humidity under some sort of control, ie walls not dripping, mirrors misting and unmisting; outside the condensate could be seen dripping as designed.
2012/10/28 16:21 UTC 1466 1470 988 House has been empty for a day, with outside temperatures between about 2°C and 10°C and heating had probably stayed off (was set at ~11°C as frost protection). MHRV has been on. Boy's bedroom 67%RH @ 14°C.
2012/11/26 15:22 UTC 1772 1872 888 New Vent-Axia Lo-Carbon Tempra just fitted in kitchen earlier today; laundry drying nearby (RH reading went up to 74% when laundry right next to meter). Dark and damp outside. Girl's bedroom 16°C and 75%RH; house was aired during fan-fitting work.
2013/04/05 17:12 UTC 1840 1939 1840 1840 944 Windows open for the first time in a while, given the sunshine. MHRV seems to have been consistently keeping RH in range ~50--70%.

Note that exterior temperatures may be directly measured, or may be approximated from (often conflicting!) local weather reports.


2011/07/25: current off-grid power system circuit diagram .SHX, PDF.

Logging (k8055)

All historic logging data from the k8055, mainly off-grid numbers, is available under data/k8055/YYYY-MM.gz, and a log of system changes is at the end of the historic stats.


A few random facts that are useful for rules of thumb, etc:


GB Grid Intensity

Code used to collect and compute GB grid intensity numbers, live and historical, published under an BSD-style free/open licence.

20110124: initial snapshot of Eclipse project:


Just for giggles, note that there's nothing secret about the makefile used to build this site, though note that for tidiness not all of the supporting scripts are in public view. If anyone really cares I can make some or all of them visible too.


The machine that serves this site is powered by local off-grid solar and wind renewable energy as far as possible, backed up by on-grid renewables including as of 2008/03 a substantial grid-tie solar PV system, and 100% renewable grid power (mainly wind) from Ecotricity; power draw is ~4W.
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Copyright © Damon Hart-Davis 2007-2013.