The Highs and Lows of a year of Solar

Yesterday (20th April 2013) we surpassed all expectations and managed the best solar day since we had them installed, so it got me wondering about which days were good and bad. Having done the maths, I thought I'd put a table up:

Month	Expected       daily amount	Best day amount	Date	Worst day amount	Date
Mar-12	6.3	15.85	27/3	4.23	31/3	part month
Apr-12	8.7	16.05	1/4	1.21	29/4
May-12	9.8	18.75	25/5	1.73	1/5
Jun-12	9.8	16.95	19/6	2.21	11/6
Jul-12	10.0	18.56	23/7	4.17	13/7
Aug-12	9.1	16.10	9/8	4.63	15/8
Sep-12	7.5	15.59	7/9	0.86	24/9
Oct-12	5.5	12.09	6/10	0.73	23/10
Nov-12	3.4	8.61	11/11	0.03	21/11
Dec-12	2.0	6.86	2/12	0.07	14/12
Jan-13	2.9	7.45	27/1	0	14/1, 19/1-25/1	snow!
Feb-13	4.6	10.91	17/2	0.63	11/2
Mar-13	6.3	11.24	30/3	0.61	8/3
Apr-13	8.7	19.16	20/4	3.63	11/4	part month

And while we are at it, my last post did not account for the FIT payment so this is what we got from March 2012-March 2013 (about 5 days more than the year) = £609.50 total for 4 quarters for a total 2650 units generated. 

The first year of Solar

We have today arrived at our solar panels' anniversary. so here are the figures:

2605.87 kWh (as read on the sunny beam yesterday) although Mike would like me to add half of the 22nd of this year as we got the meter turned on at lunchtime on 22nd last year! This makes the absolute total for the year 2607.14 kWh. Our meter for sending readings to the electricity board is only reading 2591 kWh, I am therefore going to round to 2600 anyway for all the rest of the calculations.

The original estimated generation figure given to us by Hereward Solar was 2190 kWh for the year so we have far surpassed that :) Mike then used an estimating site to generate some monthly amounts - he thinks it was the European Commission Joint Research Centre of the Institute for Environmental Sustainability, Renewable Energies Unit so we then plugged these into pvoutput.org and are using these to see if we are running to target.

Month	Estimate	Actual	Above or Below estimate
April ’12	261	255	below
May	305	328	above
June	295	301	above
July	311	336	above
August	284	326	above
September	226	278	above
October	171	181	above
November	101	104	above
December	63	75	above
January '13	89	68	below
February	129	123	below
March	195	93 in 2012	above total for both part months
		116 in 2013	likely to be below for rest of March
Total	2430	2607

so we have surpassed their estimates as well :)

The more techie toys and monitoring ability Mike gets for me, the more OCD I get about looking at trends, and we started using pvoutput.org to graph our usage as well as our generation in December. So I worked out what we use as a baseline amount over the day. There is an interesting waggle approximately every hour which seems to be the freezer or fridge turning on and off, but basically our low point now is approx 150watts of always on stuff, most of which can be accounted for by the always-on server and hub, router, and WiFi points.

There is an interesting note from one of the points in the office which if you plug a 4-way with a light on it in and leave it on, it seems to use about 30 watts of electricity! - we have turned this off now.
I will put 2 graphs up for the hours from midnight to 6am to show this. The first is from 29/12/12 giving a total usage for 6 hours of 1.73kWh, with a low point of 189W and a high point of 490W:

and the second is from 23/03/13 giving a total usage for 6 hours of 1.46kWh with a low point of 153W and a high point of 450W:

so using a calculation of 1.5kWh for 6 hours, this makes 6kWh for 24 hours or the whole day, assuming we are not in and therefore no kettles, washing machines or televisions are being used.

Given a reasonable sunny day in March - well we did have ONE this year ;) - we can get levels above 400W from 8am till 5pm or 9 hours saving us 2.25kWh during daylight. If I can also arrange for washing machines and tumble driers to be matched up with the really sunny times then I can reasonably ensure free electricity for these items as well, but it does take guesswork and sometimes I am not so good at that, or the weatherman is not specific enough. Now a simple money note is that 1 watt always on is £1 per year and 1kWh costs 12.5p to buy so we were spending 75p per day on baseline or £275 per year, now we have saved 28p per day that it is sunny enough - say 300 days per year or £85 just on having sunshine. 

We appear to have used 3864 units of electricity in 1 year to today. and the year before we used 5708 so all our (my) OCD turning off of unnecessary power/lights etc PLUS the solar has saved us 1415 units or £177 assuming direct translation from units read on the meter into kWh charged on our bill. 

Anne's end of year natter

This is my 3rd posting to this blog...

We have had our first zero day on our energy production since the solar panels went in. It is most likely due to the 4 inches of snow on the roof - which is not very photolucent!! (radiolucent is the X-ray equivalent word so I reckon that photolucent is the correct description)

However it has made me think about the year end figures so here they are:

2010 we used an average of 22 units per day electricity.

2011 we turned the very hungry computer off in April reducing our usage to approx 17 units per day saving 1200 kWh in the year.

2012 we put in our solar panels late March and reduced our average daily consumption of electricity to 12 units per day saving 1700 KWh in the year. 

This at a cost of 12ish pence per KWh makes a saving of £200.00 on our bills

We have also had 2 payments from the feed in tariff of £441.43 and £85.43 = £527.00 for 9 months of generation. If we assume that the jan-march payment will be approx £80 then our FIT payment for the year will be £600 and a saving of £200 on energy means that total saving approx £800.

At £8000 for the cost of the panels it will take 10 years to get our money back (not that we are in it for the money).

Our 'middle of the night' power usage runs at somewhere around 200-400watts depending on freezers and fridges doing their thing. so for 6 hours we use approx 1.8KWH. If our panels can generate at least 300 watts for 6 hours then our 'day when we are not in' power usage is covered by the panels. Even during the rainy weather in December we were getting about 200 watts generated, and averaged 2.5KWh per day although some days we generated between 0.5 and 0.8 KWH.

We have just bought a new power supply, case and UPS for our server as they lost all their magic smoke this week. The new system takes 30 watts more than the last one to run, but Mike is in the process of 'fixing' this. 

While we are at it I would like to rant about the gas calculations. 

If you look at our EON gas bill it says a number of items which you are then supposed to use to work out how much you need to pay. For example - a part gas bill went like this

previous	27637 estimated on 12/10/2012
Gas current	28273 read by you on 31/12/2012
	Difference - 636 units - with multiplier value 1.0, conversion value of 1.02264, calorific value 38.8
	Converted into - 7010 kWh (kilowatt / hour) used

Obviously you can all do the maths from this information can't you? It's so simple that a 12yr old with a calculator could do it!

NO it is not obvious! With the information in front of you there is no way of getting from 636 units to 7010 KWh. The essential "and then you divide by 3.6 for no apparent reason" is missing. It takes 3 levels of searching through the help file to find this missing figure. Presumably it is the conversion from watt-seconds to kilowatt-hours but why can they not put that in each gas bill in an obvious place.