ImmerSUN=Smiley House=Happy Pat!

This is my new favourite toy. My electrician Eoin (EK Electrical) connected the ImmerSUN controller last Friday and installed a new storage heater. ImmerSUN will divert excess electricity from my PV system to designated devices such as the storage (space) heater and immersion (water) heater before exporting to the grid. I’m doing this with the aim of increasing my ‘own use’ and reducing my exports as the cost of electricity goes up and with uncertainty hanging over the buy-back contracts for micro-generators like myself. It’s much more sophisticated than I expected and I’m still learning it’s full range of functions. It will also produce more recordings to work into my spreadsheets!


This is the home screen yesterday morning when it was nice and sunny. It shows 1.2kW of electricity going from the house (my PV system) to the storage heater which I have designated as my number 1 priority. The ‘Savings’ at that point yesterday amounted to 0.6kWh. Zero electricity is coming from the grid into the house – that’s why it’s smiling!

PV System Update – 2015

Despite the fact that we had the coldest May in twenty years there was reasonable sunshine and I’ve had the best start to a year since 2011. Nevertheless, for the second year in a row the output for May was less than that for April – not what should be happening. My system has now generated 5650 units of electricity of which 4422 units (78%) have been exported to the grid and I am about 68% self-sufficient with regard to my electricity needs.

I’ve put some data together – here is the output data from my solar system for the last four years:

2011        1360 kWh

2012        1235 kWh

2013        1275 kWh

2014        1179 kWh

Target      1452 kWh

Graph of PV output JPEG june 2015


PV System Update – Monthly Intensity

I was playing around with some of the data in my spreadsheets and came up with this indicator which I think gives a good picture of average monthly intensity of solar energy especially when graphed. I simply multiply the output for each month (kWh) by 1000 and divide it by the number of hours clocked up by the system in that month so obviously the unit for this indicator is Watts.

Graph of solar energy intensity JPEG 2015

PV System Update – Summer 2013

11 June 2013. The forecast output was reached in May after 22 consecutive months below forecast. There’s also been a good start to June – the mini heatwave of the last 6 days produced 63.6 kWh (of which 58 was exported); this compares with the mini heatwave at the end of May last year which produced 61.6 kWh (of which 55 was exported). Postscript: the aforementioned good start provided the basis for my best June yet and target output reached again.

July 2013. This was the warmest July on record in many stations and produced my highest monthly output yet of 211 kWh. Casement Aerodrome, the nearest station to me, had 150% of average sunshine (for the period 1981-2010) and touched 28.5 degrees C on the 12th July!

PV System Update – Daily Variation

A strange thing occurred this week, several days of cloudless skies. This afforded me an opportunity to measure the variation and trend in PV output over a day without the interference of cloud. The fact that this happened in the middle of February is surprising but less onerous than having to get up at the crack of dawn in mid Summer! I was not surprised at the basic results – I always assumed that the output over a day would be non-linear and I also expected my peak output to occur in early afternoon as my panels are facing SW. In the event, I was pleasantly surprised at the perfect curve I got and the peak output came about 2 hours after true noon. The falloff in late afternoon was more sudden than the slow build-up over the morning.

PV daily variationfev2013

PV curve

PV System Update

Since my inport-export meter was installed by ESB Networks in February 2011, I have imported 2242 and exported 1918 units (kWh). This would indicate that I am 86% self-sufficient. However I think this is a bit flattering as this is at the end of summer and I prefer to use a rolling 12-month indicator = [output/(import + own use)] where (import + own use) represents total home electricity usage. The actual figures currently are 1234/(1644 + 253) which is 65% – still not bad!  As I log PV output and export data daily in a spreadsheet, ‘own use’ comes from this and is simply output kWh less exported kWh.