Generation updates

You'll probably be pleased to hear that I'm well aware of the fact it could get very dull very quickly if I post updates for every single day's result. Seeing as I'm posting anyway, I'll post yesterday's total - wall to wall solid white cloud all day long meant it was the poorest result yet at 3.9kWh for the day.

For future updates, I'll go to a week-at-a-time, eventually dropping to month-at-a-time (as the novelty wears off).  I'm keeping the totals on a spreadsheet with some actual vs predicted comparisons, which I'll post as and when.

Feed in Fusspots

I've been having fun and games applying for the Feed-in Tariff:

I was warned by the installation company that the energy companies are notoriously tricky when it comes to applying for the FiT.  They recommended I post off my application recorded delivery - they have a habit of 'losing' the paperwork.

So I pored painstakingly through the application forms, and the boss bloke from the solar panels company confirmed it was all filled in correctly.

We're with npower for our elec/gas, so it is with npower's application form that I have experience (they vary from energy company to energy company).

At the end of the form, it asks for you to supply 'supporting documents'.

I am already an npower customer, so I didn't need to supply a photocopy of my driving licence and two utility bills addressed to me at my address.

But I did have to supply:

• the EPC certificate for our house, showing at least band D (to qualify for maximum FiT rate)
• the MCS certificate from the installer showing the installation is complete and has been carried out to regs
• the invoice from the installer showing my home address to confirm my relationship with them having installed it

I sent all these off on Tuesday, recorded delivery, with the forms, thinking I've dotted every i and crossed every t.

But I thought I'd better ring npower's FiT team this morning to check they've received the application and that everything is ok.

The 'helpful' lady at the other end of the line confirmed that they had indeed received my application, but they had had to reject it because the invoice does not state that it has been paid in full, and have returned it to me second class post.  She said that if I can get another invoice from my installer showing that it has been paid in full, I can re-apply and all will be fine.

*steam*

I rang the Low Carbon Energy Company this morning and explained the situation. The chap had a steam also, ranting a bit about how picky the energy companies are becoming about these FiT applications. He's posting me out a fresh invoice, showing that it has been paid in full, so I can re-apply.

I'm now thinking, 'have npower really posted my application back to me? She did say "second class"... perhaps that's code for 'You've not received it? Oh it must have been lost in the post'.....

Ah well, have to wait and see... I'm half expecting to have to fill out a brand new form again.  Good job I only sent scans of the original documents, and not the original documents themselves...

Clouds

Cloud cover has meant today has not been as good as yesterday for solar generation.  The day started reasonably bright, with horizon-to-horizon white cloud, slightly drizzly.  By 10am the solar array was only just managing 0.5kW.  The clouds hung around all over lunchtime, which meant it was only pulling about 0.6-0.7k during peak time. But the clouds started breaking up about 3.30pm, and between 4-5pm, the rig was pulling a more healthy 0.9-1kW during breaks in the cloud.

It's now (practically) 6pm, and it's down to about 300W in bright sunshine. I may get a bit more today, but not much.

Total for 29th August 2013:  5.1kWh

First full day

Well, the panels have had their first (practically) full day.  It's twenty to eight and the sun is just disappearing behind the houses at the end of the road.  The inverter is showing the princely sum of 6W currently being generated by the array. That's about as much as I'm going to get today.  I've found the aurora has a cool little graph to show the energy generated throughout the day.

More to the point, the inverter is showing the very princely value of 8.3kWh for the total generated today. This, I am very happy with indeed.

I have done a bit of rummaging around the t'interweb, and have found a great web page on the met office showing the average sunlight (amongst other things) for Blackpool over the years 1981 - 2010, broken down into months.

http://www.metoffice.gov.uk/climate/uk/averages/19812010/sites/blackpool.html

Note this is not all daylight hours - this is hours of actual direct sunlight, excluding hours when the sun is behind cloud. Very useful for solar panel calculations... I have crunched this with the predicted yearly total kWh to give the predicted monthly average kWh for each month.  I've then broken each month down into days simply by dividing by the number of days in the month. For August, I should be generating an average of 5.98kWh per day to achieve the predicted monthly average of 185.39kWh. At 8.3kWh, this is 139% of the predicted average.  I know this is only one day, but we are at the end of August, and I would expect this to be the worst end of the month for sunlight. The beginning of the month would have yielded higher values. 

If I were to (probably quite foolishly) extrapolate this increase across the whole year, my revised predicted total kWh generated would be 1645 x 139% = 2286kWh.  I think it is probably a bit rash to be expecting this much, but I am cautiously looking sidelong at 2000kWh... Today's actual v predicted kWh does seem to correlate very nicely with the "about a third more" quotes I was getting regarding these 3rd gen HIT panels. Only time will tell....

The boss bloke from the solar panel installation company has been today to sign off on the rig so I can apply for the feed in tariff (and so he could collect his cheque...!)   I have posted off the FIT forms, and he tells me it takes about 2 months for them to process them.  They backdate the payments to the commissioning date, so I don't lose any payments, they just make you wait for it.  

The official documented maximum supply of my 8 panel array is 1.92kW (each panel is actually only 240W, not 250W), although it's referred to as a 2kW array.

So how much of that maximum did I see today? Today has been a bit overcast, with some broken cloud and hazy sun.  You can see on the little graph on the photo there's only a narrow peak in the middle couple of hours around lunchtime when I'm getting the maximum out of the system.  Although the peak in the middle could have been wider, it's just that the broken cloud cover today meant it wasn't maintaining it's maximum as long as it could have.  I looked at the screen around 1pm.  Whilst the sun was behind hazy cloud, it was hovering around 1.6-1.7kW. When the sun popped out of the broken cloud and the array received direct sunlight, the meter peaked temporarily at 1.90kW.  I'm guessing that this is as high as it's going to get in August - I assume it could only hit its theoretical maximum at midsummer (end of June) when the sun is at the optimum angle in the sky.

Update on the drop in voltage on being connected to the grid:   Rubbish. This was just me being a plantpot (not the first time).  What actually happened is that whilst the bloke was tinkering with initialising the inverter, a good 10-15 minutes passed between him connecting the array and the inverter finally getting connected. It was during this 15 minutes that the voltage dropped off, simply due to the sun dropping in the sky.  As described in the paragraph above, it has hit very close to its theoretical maximum at times.

One final note that is worth making - this aurora inverter runs practically silent.  I had to put my ear onto it to make out a faint hum. 

So that's that... Feel free to ask q's - the future updates will be less wordy, I'll post actual vs predicted values at regular intervals.

The first drops of juice

The panels going in.

All 8 in their final resting place. Long may they generate.

And the inverter showing the juice coming in.  The boss bloke has emailed and he's coming round tomorrow to go through the feed-in tariff paperwork and approve the system for MCS.

The large numbers show the input power being delivered at 517W (just over 1/2 kW).  It is a sunny day today, so I assume the system is running at maximum power. This puzzles me as it is a 2kW array. What is happening to the other 1 1/2 kW?  Will get back to you on that one... Question for boss bloke tomorrow methinks.

The input voltage of the solar array is steady at 338V (42.25 Volts per panel). I noticed that when it was first powered up and began initialising, the inverter showed the array input voltage at 399V (50V per panel) which is the absolute maximum, as I would expect on a sunny day. Once the inverter had finished initialising, it clicked into 'ready' mode and connected the solar energy to the grid. The input voltage of the array immediately dropped to about 338-340V, and steadied there.  It appears that putting the array under load decreases its output voltage.  

Not sure what the little graph on the left of the screen is for.  I guess it will show the increase and decrease in energy generated over the day.The first row of small numbers below the large numbers is how many kWh generated today (currently 0.2kWh). This will reset every 24 hours (at midnight I assume). The second row of small numbers below is how many kWh generated in total, since installation (currently showing 0kWh - I assume this will update once a day at the end of every day).

Finally the panels go up

The installers are hard at work. The retiling of the roof is complete (you can tell the difference in colour between next door's roof and ours). The panels are currently leaning against the conservatory awaiting their final journey. All tested, all producing about 50 volts each. I had a brief chat with the gaffer about the HIT panels and about how I could expect them to perform compared to standard panels. He said that in full, direct sunshine, they generate about 10% more than a standard panel, but that I'll notice the difference most in 'diffuse' sunlight. For example, on an overcast day, they'll produce pretty much full whack, whereas the output of a standard panel will drop more noticeably.  Also, in the morning, as the sun rises, these panels will rise to maximum output earlier, and also as the sun sets in the evening, they'll remain at maximum output longer. So they're operating at maximum output for more hours each day. He says that in England's weather/sunlight patterns, this translates to approximately 1/3 more kWh over the year compared to a standard panel.

The panels attach onto pairs of rails, which are fixed to the roof on brackets. You can see two of the rails on the photo - all the brackets are installed, and the top rail has yet to go in. For each bracket they lift out a tile and fix the bracket to a roof joist, and seal up the gap in the tiles with a lead flap to prevent rain getting in.

Each panel has two watertight connectors, to allow them to be daisy chained together, and the first and last one then connect to the two DC cables that run through the roof, into the loftspace and down into the under stairs cupboard.  You can just about see on the photo where the two cables disappear under a tile.

Where it all began

This is my blog about our solar panels.  I first looked into solar panels about 3 years ago when the UK feed-in tariff was launched. Back then, the householders who generated their own electricity were earning 41.3p per kWh (solar or wind).  Sticking a thumping great turbine up at the bottom of the garden would not have helped our good relationship with our neighbours, and besides would certainly not have received planning permission, so that left us with solar.  I asked for a quote from a local specialist, and it came back at 'about £15,000'. We didn't have that kind of cash, so I reluctantly had to let it go.

A few months ago, I decided to look into it again. The government are now offering a feed-in tariff of 14.9p/kWh for installations that are commissioned before October 2013 (http://www.energysavingtrust.org.uk/Generating-energy/Getting-money-back/Feed-In-Tariffs-scheme-FITs#rates)

• A little aside about the feed-in tariff system:  You have an electricity meter installed with your system that measures just the electricity you generate from the panels. You get paid (by whichever energy company supplies your electricity) for every kWh your system generates. The early adopters are still getting 41.3p for their electricity - and will continue to get that until their tariff expires. Each feed in tariff runs for 20 years from date of commission. The price you earn is 'locked in' from day 1 of your tariff. So we'll fall into the pre-October 2013 tariff, which means we'll get 14.9p for every kWh we generate from now until 2033.  Another important note is that since 2012, the government have introduced a restriction to feed in tariffs - to be eligible for the full rate (14.9p currently) your house must have an Energy Performance Certificate (EPC) of at least band D.

But what's a kWh and a kW?
Every panel generates a certain amount of kW (kilowatts). Usually 1/4kW each. If you have 4 panels, then your system will generate 4 x 1/4 = 1kW. If you have 8 panels, then your system will generate 8 x 1/4kW = 2kW.  These values are the absolute maximum power they can generate, in full, direct sunshine. Overcast days or panels in shade will generate less than this. Obviously, at night time, they generate nothing at all (duh).

But you don't get paid for kW, you get paid for kWh (kilowatt-hours). The longer you leave them 'turned on', the more kWh they generate. If you leave a 2kW system running for an hour, it will generate 2kWh. If you leave a 2kW system running for two hours, it will generate 4kWh. Leave it running for 3 hours, 6kWh, and so on and so forth.  Remember, these are maximum values - you will not get the maximum out of your panels from sun-up to sun-down (more on that below - see prediction calculators).

14.9p per kWh? But you're getting so little compared to the early adopters?
Yes we are. But, 3 years down the line, solar panel technology has rapidly developed, with 3rd generation ("HIT") panels now available for a lot less than the 1st generation panels. For the same amount of sunlight, each of my panels (http://www.evoenergy.co.uk/wp-content/uploads/2012/05/Datasheet-HIT-240W.pdf) will generate about 1/3 more electricity than the panels I could have bought 3 years ago. And they're smaller, so I can fit 8 of them where I could only fit 6 of the 1st gen panels. Another point to note is that all solar panels degrade over time. Even the 3rd gen panels are quoted as generating only 80% of their original power after 20 years (90% after 10 years).

Prediction calculators.
There are a number of online forecast calculators (eg http://www.energysavingtrust.org.uk/Generating-energy/Getting-money-back/Solar-Energy-Calculator) that will predict how much energy (kWh) per year you are likely to generate. They take into account things like: how many kW of panels you're putting up;  the direction your roof points; how long the sun is in the sky each day; where abouts you are in the UK (southern homes will get more sunlight than northern homes and so therefore generate more electricity); the angle your roof is at (about 30-40 degrees is the optimum angle so I believe - panels laid flat or vertically generate less, something to do with reflectivity).  Our rig has been predicted at 1645kWh per year using the above calculator.  I've chatted with two solar panel installers, and both told me that every single installation they have put in has generated more than the predicted amount. But they are not allowed to give a more accurate estimation, they have to use the gov't figures. They added that it's better to get a pleasant surprise than be disappointed!

I found a company online called the Low Carbon Energy Company.  They've been installing solar panels for about 15 years, they're MCS registered (Micro Generation Certification Scheme) which means they're approved for commissioning the installation for the feed-in tariff (essential).  I was quoted £5270, all in, to install the system (8 panels - 2kW) and commission it.  Where do I sign, I said (after checking with the wife and the savings account, naturally.)

Financial aspect
From an investment point of view, using the official generation prediction, we'll be generating 1645 kWh x 14.9p per year. This is £245 per year, which equates to a 4 1/2 % return on the investment, worse case scenario. You'll struggle to find 2% on even a locked-in deposit account so it makes great sense from a purely financial point of view. But it doesn't end there. I am perfectly entitled to use the electricity I am generating. I still get paid for every kWh I generate, even if I use it all myself. The only proviso being that it has to be used as it is being generated, ie, during daylight. But it doesn't end there. The government assumes I am going to use half of the solar generated energy myself, and I get paid again at 4.64p per kWh for the remaining half I'm sending back to the grid. Which is another £38 per year. A pittance, but still.

I work from home, and my office has 3 computers, 21 downlighters and an air con. The dishwasher and washing machine are in regular use during the day. I don't know how much of the solar generated energy I will use, but it'll be a large portion of it.  All my home-grown energy I'm using is energy I'm not having to buy from the grid. So I'm making a saving on my electricity in addition to the money I'm being paid from the feed-in tariff. If I estimate that I am using half the energy I'm generating, that equates to 822.5 kWh per year. I'm paying 15.1p per kWh for my electricity at the moment, so that is a yearly saving of £124. So we'll be better off to the tune of £245 (f.i.t.) + £38 + £124 = £407 a year.  This gives a total time to repay the £5270 investment of just under 13 years, so it's a long term investment. However, I'm cautiously optimistic that the actual figures will be a lot better than these, but only time and the sunshine will tell. In addition, as electricity prices go up (and you can bet your bottom dollar they will), the savings we're making will increase.

We're in the fortunate situation that the back of our house faces due south, which is ideal for solar panels, because they're collecting direct sunlight all day long.  From the conversations I've had with installers and proponents of the industry, you can put solar panels on west- or east- facing roofs, but they will only generate significant amounts of power in the morning or evening.  That doesn't mean you can't put solar panels on east or west facing roofs, but they won't provide as high a return. North facing roofs are not worth the bother.

Rear of our house with the scaff up ready to install. Half a day's work for three scaff men. Would have been quicker but they had to do a bridge over the conservatory.

The complicating factor
Our house has an original roof - this means that when the tiles were laid back in the 1930s, they were laid directly onto the wooden roof battens, without a layer of felt between the two (as they do nowadays).  The previous owners of the house, in their infinite wisdom, decided to insulate the loft on the underside of the roof with that spray on insulation foam stuff that sets hard (looks a bit like cinder toffee).  Because it was sprayed directly onto the underside of the tiles, it welded them all together, absolutely welded them. When the roofers came to examine the roof, every time they tried to remove a tile to fit the brackets for the panels, it would crack all the tiles around it. And when they tried to removed the cracked tiles to replace them with good tiles, they would crack all the tiles around it.

Anyway, after a discussion with the company, they said the best thing to do was to remove all the old tiles (and insulation foam underneath) and re-tile the south face of the roof prior to installing the panels, which I agreed to since they gave me a very competitive price to do it.

The electrics are all in. You need space for an inverter (the heffing big box) which converts the DC energy from the panels into AC energy that it compatible to be fed into the national grid. You also get a little digital meter to show how much energy you've generated, and the whole thing is topped off with two isolator switches to shut it off.  You also need a spare slot on your main electricity consumer unit which is how the power gets fed back into the grid.

These are the 8 panels themselves. They're Panasonic HIT-N240SE10 and represent the cutting edge in solar power generation.  They're going up later this week (all being well) after which I'll update the blog.