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PV panels: 'solar so good'

PV array

A solar panel installation in the Littleworth area of Stafford might seem an unlikely setting for the attentions of those fictional sleuths Holmes and Watson, but they are on the case day and night. As houseowner Geoffrey explains, in this case 'Holmes' is actually a software program that analyses the readings taken diligently by 'Watson', a compatible wireless energy monitor. Working together, Holmes and Watson allow Geoffrey to see just how much electricity is being generated by his array of solar photovoltaic (PV) panels, installed on the roof of his house in June 2010, and store the data on his PC. Geoffrey is one of a growing band of people who recognise the benefits of the new feed-in tariffs (FITs) for electricity generated by solar panels, both for the environment and as an investment.

The installation

Following a survey, Solar Logic, a local company based in Great Haywood, was commissioned to install the array of seven panels on the south-facing aspect of the house roof. The panels were arranged to maximise their number and avoid shading by the front dormer. Each of the ET Solar monocrystalline scaffoldingmodules measures 1580 x 808 mm and is rated at 185 watts peak (Wp), giving a total power rating for the array of 1.3 kilowatts peak (kWp). The electricity feeds into an inverter in the loft, which converts it from direct current (DC) to alternating current (AC), so it can power domestic appliances or be exported to the grid.

Under the stairs there is an output meter, which measures the cumulative output of the panels, and also the import/export meter, which keeps tabs on how much electricity is drawn from the grid and exported to the grid. This enables the electricity supplier to calculate the export tariff element of the payment, over and above the payment for each kilowatt hour of electricity generated. Solar Logic produces a detailed personalised user manual, containing full specifications of all the components, and has guaranteed the panels for 25 years.

Close-up of the solar PV modules

Performance: 'exceeds expectations'

At the outset, Solar Logic estimated that the panels would generate 1000 kilowatt hours (kWh) per year on average. In the 6 months since the installation in June, the cumulative total is 566 kWh, so at this rate the panels will exceed the 12-month forecast. The digital import-export meter tells 'Watson' what's going on

'Elementary' Watson!

For those keen on following the performance of the panels, Holmes and Watson can keep you amused for hours. Indeed, Watson the monitor takes wattage readings from the panels every 5 minutes, besides checking on the electricity being imported or exported at any time of the day or night. Meanwhile, Holmes can display Watson's readings in any manner of forms, create spreadsheets and graphs, compare different months, days, etc. and calculate financial returns.

Geoffrey would recommend Solar Logic, and found them to be 'helpful and efficient'. However, he has discovered that the panels do not operate when covered in snow, although they do still work with a coating a frost. Also, there is some unforeseen shading of the panels from a tree in the front garden when the sun is at a low angle in mid-winter. One piece of advice that Geoffrey would give is: 'be sure to register the installation with your energy supplier as soon as it is working'. This means you will start getting the FIT payments from the earliest possible date.