Installing Solar_cells

[peterb]

nice photos of the panels in situ by the way

Yes, and if you look at the top panel on the right, you will see that the two top retaining clips are missing, the installers left them off! They are coming back to fit them!

[Noxvayl]

From the photo you've posted, using its orientation, it looks like the top left panel from the shady side of the roof and the bottom left panel on the side with sun on it... I'm guessing you are talking about it when looking at the roof from the ground, or swapping the picture orientation 180°, but I can spot it now that you've mentioned it; would of missed it otherwise

[peterb]

They are missing from the top edge of the right hand panel at the top of the shady side (the right hand one in landscape orientation)

[peterb]

OK, so clips have been refitted and all is working well. Not surprisingly, the energy I am harvesting is dropping as the sun gets lower in the sky and the days get shorter. My first feed in payment will be in December.

however, I have been monitoring energy usage from the grid, and according to my supplier, I should be reducing my monthly direct debit for gas and electricity by about £30/month. This is slightly complicated because I had built up a credit on the account, and the reduced payment takes that into account to wipe that out over the next seven months, and i have switched t a slightly cheaper tariff. But that indicates a saving of perhaps £300/year - and the savings should be better when the days start getting longer in the new year.

In practice, I'll probably request a refund of the credit and use that to reduce the outstanding loan, and of course I'll use the FIT tariff for the same purpose.

In december, I'll look at comparative energy usage from the grid over the same period last year. Of course, without an export meter, I don't know how much of the energy I produce is being used by me - the assumption will be the difference between the two figures, although my pattern of energy usage will have changed slightly.

[peterb]

It is now just over 3 months since the panels were installed, so I have some comparative energy figures.

From 5/9/13 to 5/12/13 I used 2,571 kWh of gas, and 805kWh of electricity. Cost before discounts and VAT was £260.93 Total energy consumption from external source was 3,376 kWh

From 9/9/14 to 9/12/14 I used 2,046 kWh of gas and 434 kWh of electricity. Cost before discount etc was £156.18. Total energy from external source was 2479 kWh.

In addition I generated 472 kWh of energy. It is hard to estimate how much of that I used, and how much I exported, but assuming I used all of it, I used less energy this quarter than the previous one. Now that could be down to the fact that it has been a milder autumn than last year, but I have been taking some steps to reduce energy consumption, so a realistic estimate might be that I used 80% of the energy I generated, making my energy consumption around 2,720 kWh.

So i have saved around £150 in energy costs, and I expect to receive around £80 in FIT payments, so net saving is £230 this quarter. Next quarter should be similar, depending on weather, but the two quarters after that should see greater generation and reduction in energy use as the days get longer and overall energy consumption reduces. I anticipate not using any gas at all in the summer.

The interest payments on the loan are around £17/month so over the quarter comes to £51 so overall I seem to be £180 better off. Of course, it isn't that simple, because I am also paying back the loan as well, so in the short term, I am worse off by about £200 over the quarter, but again that figure will change as the days get longer. The FIT will also increase slightly with the RPI, and any changes in energy costs will also affect the calculations, but overall, I am quite pleased with the result. My aim is to pay off the loan well before I have to, so the interest payments will effectively reduce as well.

So thats the update for this quarter!

[TeePee]

Your estimation of cost savings was 200GBP/year, or 50GBP/quarter, while your actual figure shows a 600GBP/year cost saving.

Your estimation of income was 620GBP/year, or 155GBP/quarter, while your actual figure shows a 320GBP/year income.

What do you think is the biggest cause of the deviation from both estimates? I am please to see you're doing better than hope for!

10,000GBP invested in the S&P500 would have shown you a profit of ~325GBP for the quarter.

[peterb]

I was very cautious in my initial estimate, and the autumn has also been very mild. I have also taken positive steps to make maximum use of the power I generate, so I will use high energy consumption devices sequentially (for example, run washing machine, then dishwasher, rather than both at the same time} and delay running either until the sun is shining (where I can). In terms of cost, I have switched to a slightly cheaper tariff, which is why the energy savings are probably the best measure.

In terms of monthly cost, the tariff change has accounted for about £3/month, while the solar cells and energy saving measures account for about £15/month.

But on most days, during daylight hours, I generate enough to power the 'background' load, fridge, freezer, server and the like, and while they are low power devices, they are on 24x7 so the energy consumption mounts up.

I also expect the income from generation to increase during the summer, with longer days and better weather, so the annual income should be more than £320. For example, from 23 August to 9 September, I generated 157kWh, worth £22.50 or just over £1.50/day. If I average that over a year, then that is £550.

On the best day, I generated 15kWh, which is £2.40 worth. If I can generate that for 90 days over the summer that is £240. But I won't know until next August!

Hope we have a good summer!

[oldboy47]

I have just seen this thread for the first time and have to say that I find it most inspiring. I notice near me a lot of new builds are including solar panels on their rooves and wondered whether or not it was just another marketing gimick (possibly is with only 4 or six panels per property).

I would appreciate knowing some idea of the fixing method and weight loading of the panels - I live in a converted barn with 100m2 of roof.

Thanks in advance

[peterb]

Depends on the roof, but in my case, with standard clay tiles, a few tiles are lifted and supporting brackets fixed to the rafters. The tiles are then replaced, with arn arm protruding. Rails are fitted to these brackets, and the panels are fitted to the rails.

This means that the load is taken by the roof sub structure. Each panel weighs about 21 Kg. It's similar on concept to a car roof rack!

From the installation aspect, the maximum installed capacity for a domestic installation is 4kW. Which in my case is 16 panels. 4kW is the maximum under optimum conditions, so there will only be a short period in the day when that power will be generated, but that is the baseline.

You can install more, but the FIT drops slightly in terms of payment for energy generated, and domestically, 4kW is probably more than you can use, excep for brief peak demand, and as the payment for energy you feed in is based on 50% of what you generate, and is a relatively small amount, it probably isn't worth installing more, unless you go big time and have 30kW or more, when the energy you export is metered.

On the other hand, as installation is quite a large proportion of the cost, it probably isn't worth installing less, even if the installation isn't optimum. I have 10 panels facing South East, and 6 facing South West, dictated by the size of my roof.

So I never generate maximum power, but I generate for longer during the day as the sun swings round, at least in the summer. In winter when the sun is lower in the sky, output is lower.

My system uses one low power inverter per panel, so I generate AC power per panel, which minimises the effect of shading. In systems where several panels are connected in series to one high power inverter, shading of one panel can reduce the output of the whole array. That can be mitigated by splitting the array into several parts, with one inverter per array, but that puts the price up, and the inverters are quite big. My inverters are mounted on the roof rails under the panel that feeds it.

So there is a lot to think about. Technically, I think the micro-inverter is the way to go, and install the maximum you can up to 4kW. Panels don't need direct sunlight, but for maximum efficiency should be generally South facing. However there will never be a position that is always optimum throught the year because of the varying height of the sun throughout the year. However, although my panels have only been in for 4 months, I have usually met or exceeded my background load for at least part of the day.

[peterb]

Just noticed this morning that I have generated 700kWh since the system was installed last August. With the day's getting longer, I' m looking to see greater production in the next seven months.

Next FIT payment date is March.

[Moby-Dick]

Nice one - Winter hasn't been great for PV generation for me, but I dont have fancy micro invertors in my setup

I just calculated I did 776kWh since august ( which was my peak month at 277kWh generated - the lowest month was November with only 73kWh worth of generation )

I have 20 x 120W panels on my roof with a single invertor.

[peterb]

You panels sound as if they are more optimally positioned than mine, I have 10 facing south east and 6 northwest. The northwest array hasn't generated much in the winter, and the South East are shaded first thing with the sun low in the sky. The highest daily generation was the day after installation, just over 3kWh!

[Moby-Dick]

yeah mine are all south east facing - it doesn't do much for afternoon generation though.

[peterb]

Well apart from the fact that my SE facing roof only had space for 10, I did think that I would generate later in the afternoon. and that seems to be the case, so peak power is lower, but average is probably better, particularly in the summer.

[guido123]

unfortunately the subsidies are now what they used to be in the uk - shame

[1stRaven]

I've just ordered a full 4kw system for my house. Luckily, I have enough room on the house and garage roof to allow the full system a complete south facing view. Looking forward to reduced bills in the future.