In the bleak mid winter

My monthly update is late as I wanted to see how the weather situation resolved, particularly with respect to the effect of snow on the panels. First is a graph of the past 34 days.


Notice how ten days are at zero. No appreciable power was generated because of the shading effect of snow on the panels, even when the Sun shone. If there is no more snow, then perhaps the recent fortnight might be the lowest point. What was remarkable was that a large portion of the panels could be clear but it took only a few percent coverage to completely short out the panels. A steeper roof would have cleared them more quickly. It has been an unusually snowy winter so far - and earlier than we are used to. Now on to the bigger picture:

This graph shows all generation since the beginning. The red line is the panels' 30-day average and the recent paucity of power has brought that figure down to only 1.54 units per day. The yellow line is the average daily power since installation. With ten days to the solstice, this figure is at 8.43 and continues to drop as expected. My hope is that by 18 May, it will be above 6.85. That would mean I had beaten the prediction of 2,480 units annually. I must say, it's starting to look like a close-run thing.

Hitting the bottom

Five days ago, winter came early to the UK and I learned what effect the snow has on a solar PV array. Basically, for me at least, it means zero power - even in bright sunlight. In the relative warmth of the day, the blanket of snow on the panels melts slightly and moves down the incline to expose up to 50% of their area. Yet apparently just having a portion of a panel shaded shorts out the whole panel and dramatically reduces its effectiveness. A trickle of power is generated but even after four days, it has not been enough to make my generation meter tick over one tenth of a unit.

Perhaps if the inclination of the panels had been greater, they would have shed the snow easier. As it is, I will just have to wait it out.

Having just got the payment for September's FiTs readings, EDF sent me an email for December's. We'll see if they pay this one faster. Only £130 is due this time.

Zero point one!

This is October's report though it's now 5th November - Fireworks are going off all around. In the summer, I tried to predict what my lowest figure for a day's generation would be. I seem to remember guessing it would be one or two units. Yesterday came in at a paltry 0.1 kWh! Wow. It can hardly get any less. There have also been other days with 0.2 and 0.3 units and sunny days have peaked around seven units. Amazing how a heavy Atlantic front cuts out the light. Here is the graph of production thus far:

The profound reduction as we head into late autumn is very apparent. My 30-day average to today is 3.68 units while the average since I started has just gone below ten at 9.84 units. Still hoping it stays above 6.85 units come 18 May. Overall, I think the panels are performing to expectations or better. It will be interesting to see how much the deepening winter will cut the power further.

One other thing. I sent a meter reading to EDF on 13 September which should yield over £550. This has still to appear in my account. I phoned them after six weeks and it was nicely pointed out that payments can take up to 90 days. I hadn't expected that. At this rate, my summer peak will arrive in time for Christmas.

September's report

This month's graph shows that a combination of shortening days and autumnal weather has heavily cut into the amount of power my solar panels can generate.

There is a very noticeable dip on the right side that began on the 13th September when a weather system cut my power to less than one unit (0.9) of electricity. This was repeated two weeks later and the 30-day average (orange line) has made a strong dip to 7.22 units. The overall average (yellow) is sliding more gently, as would be expected, and is now at 11.19 units a day since the panels were installed.

I'm still waiting for EDF to send my first payment after I sent my meter reading. It is now three weeks. I'll need to chase them up.

Where'd the light go?

Two interesting things happened coincidentally today. There was an email waiting for me when I got the computer on. It was from EDF and it was asking me for my FiTs meter reading. FiTs meter readings are supposed to be taken every three months but the timing of my start in the system means there is an extra sunny few weeks tagged onto the front of this set. Therefore, from 26 May to 12 September, I generated 1,306 units and this should realise £539.38. Additionally, half of these units should attract the £0.03 export tariff which adds another £19.59.

Amazingly, on the same day, a huge weather front passed over the UK today depositing a lot of rain. It also blocked the Sun rather well. Before today, my worst daily generation had been 3.4 units about 3 weeks ago. Today's return was a measly 0.9 units; astonishingly low and an indication of how poor a wet December or January day will be.

Improving weather and free power

It is a measure of our poor summer that even as the days shorten dramatically, my averages are improving. Of course, this is helped by the end of August being blessed by a true indian summer that looks to continue into the first few days of September. As the graph shows, even my annual average, which had been declining steadily (yellow trace), is showing a distinct upturn.

At the end of August, my total average as measured from installation was 12.3 units daily, well clear of the 6.85 figure that the predictions gave for my installation over the course of one full year. In fact, Given that the prediction was for 2,480 units annually, I reached the halfway mark of 1,240 units on 26 August. That's just over 3 months since installation.

The total earned from the Feed-in Tariff was £493 from 1,200 units since the scheme began. That excludes any addition made for the 3 pence export tariff. Since half of those units will be deemed to have been exported, that should add 600 x 0.03 which is an added £18. What happens next is that during September, I expect a letter from my energy company requesting a reading from my generation meter. My actual payment for the summer will be based on that.

I'm very happy with the performance of the installation thus far. In fact, I view it as a small part of my pension. Like a pension, I make an investment while I'm earning which realises a return when I'm not. There was an item on the BBC which shows that I'm not the only person who views it as a long-term investment. A company in England has seen a very clever opportunity to make a profit.

What they do is lease space on a homeowner's roof to install an set of panels. The owner gets access to the electricity and will therefore save money on their bill if they use the power when it is available. The company gets the Feed-in Tariff, which is the really profitable part. I guess it's a good system for those who are not able to access the cash to install panels themselves. It gives them the benefit of free electricity when the Sun shines. Yet I feel that what's good for that company will be good for me and my family. I am much happier having made that investment now.

Gloomy summer

In late June, the Sun shone well and my array of panels were reaping over 20 units of power daily. Since then, the Scottish summer has broken and wave after wave of Atlantic maritime fronts have washed over us. We get a front every two to three days and the associated cloud has kept a lid on power generation.

On 20 June, my 30-day average peaked at 15.7 units. Now at the start of August, the 30-day average is down to 10.4, helped in large part by poor Glasgow weather for the two weeks we were away in the Western Isles, when daily power averaged only 9.4 units.

Another interesting figure is that my daily average since the panels were installed is at 12.57 unit and gently falling as the days begin to shorten and the Sun gets lower. A good heatwave would help but there's no sign of it. Still, I'm well clear of the 6.85 average that the government estimated. Here's a chart of daily usage since I started. The two smoother displays represent the 30-day average (orange) and the overall average (yellow). The straight line towards the right is the generation over the 14 days we were on holiday. Since I wasn't there to take a daily reading, I've had to take the total generation over the two weeks and divide it by the number of days. Its low value indicates how poor the weather was at home while we enjoyed the sunshine in Lewis.

There's not really any other news at the moment. The next reading to go the FiTs people will be in September and I expect it will yield £450.