Solar PV
Many are today familiar with Solar Photovoltaic (PV) panels fitted to home roofs to save money on our electricity bills. Twelve years ago they were not so widely used and there were significant government grants and incentives available to promote their adoption. The systems were also very expensive compared to today.
In 2012 we took the decision to install the largest solar PV array we could fit on our available roof space. It was a 'massive' 3.6kW setup of 15 x 240W panels costing £11,000. This was the largest output permissible at the time. It was installed and commissioned in time to receive the higher Feed In Tariff (FIT) payable for 25 years. It took 12 years to break even. The FIT was withdrawn in 2019 relying instead on how much could be saved or exported.
Installation
Living in a traditional Scottish stone cottage with dormer windows we did not want to compromise the slate roof or have the panels visible from the lane at the front. Instead we decided fit them to the 13 degree roof of my log cabin photographic studio behind the cottage at the foot of the back garden.
The roof allowed us to install 3 rows of 5 240W panels totalling 3600W. These were connected as a single string - all the panels in series - with a single inverter and a generation meter. The output was routed via a buried armoured 6mm2 cable to the house distribution box.
The metal roof of the studio allowed slimline brackets to be used allowing the panels to lie falt with no gap.
Shadows
One disadvantage of solar PV panels is that they lose generating power if any part of a panel is in shadow. When connected to a single string the whole array is limited by the lowest output panel.
Running along the eastern side on our cottage is a headland of tall pine trees. These cast a shadow on the panels until 0930 which is very annoying as in summer the sunrise can be around 0400. I got permission from our farmer neighbour to reduce the height of some of these trees which improved matters..
An alternative to a single string is to use micro inverters for each panel so that the shadows only impact fewer of the panels.
Certification and Contractors
Our solar PV system was installed by Richard Irwin Renewables who provided MCS certification for our installation. This proved important when I came to transferring my FIT payments between suppliers recently. What I did not receive was a paid receipt on completion so ensure that get one.
Richard Irwin stopped doing solar installations several years later. When the inverter needed replacing I had to find another contractor who also stopped trading over COVID. When the replacement inverter also failed I was fortunate to find a local installer to carry out testing and commissioning of the warranty replacement.
The lesson here is to make sure you get all the certification, documentation and receipts at the time of installation. Solar PV system are said to have a life of 20 to 25 years but future support can not be guaranteed from the original contractor.
Investment and Returns
The FIT has made our investment worthwhile. The high initial cost has been offset by the £1100-£1800 / year FIT payments which covered the initial cost in 10 years leaving us with a similar net return over the next 15 years.
The FIT is paid quarterly by our electricity supplier based on the solar energy generated and a portion of what is exported. Initially the export was paid on 50% of that generated as 'assumed export'. When I transferred the FIT to Octopus Energy the export became based on our Smart Meter Export reading at 4p/kWh. A recent move to a separate Fixed Outgoing Octopus tariff now pays 15p/kWh monthly and taken off our electricity bill.
Unfortunately, FIT is no longer available but other income is now possible. With more powerful panels available today (300-400W) and innovative export tariffs some users can actually be paid for the the electricity they use and export. New solar PV installation are at least a third half to a third of the cost we paid.
Solar Power in Scotland
We live in North East Scotland on the Moray Coast at 57N. In winter our days are short with just 6 hours of daylight. By contrast in summer we are blessed with up to 18 hours of daylight. Our weather can be very variable and many days of cloud and rain. However, when the sun shines, it shines.
Solar generation therefore varies from as little as 1 kWh/day in winter to over 22kWh/day in summer. Over a year it balances out. We consistently generate over 2.7MWh / year.
Some say that solar is pointless in Scotland. I would beg to differ. The past 12 years have shown that the benefits over a year make it well worthwhile.
The rewards of Solar PV
Our journey with Solar PV has been rewarding. The extra power and income has helped offset the increasing energy costs over recent years. The power generated coupled with other investments (EV and batteries) have significantly reduced our monthly outgoings.
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