When a Solar PV system is being installed there are only three goals: outstanding system performance, aesthetic appeal and a watertight finish. As everyone’s property is unique, the only way to achieve these goals is by understanding the obstacles at the very start of the process. Richard Swords explains.

Specification

The location of your home, the incline and size of your roof, your energy usage and your budget are key in determining the overall size of your Solar PV system. It’s the role of the design engineer to take this into account when conducting the technical survey. S/he will recommend the optimum system to suit your needs, while ensuring that the design is also in sympathy with the overall look of your property.

Within a few days of the survey you will be able to see the detailed specification, which will show an illustration of the Solar PV panel layout together with the expected performance of your microgeneration system (which has been calculated using SAP criteria*). This will include precise roof orientation and inclination measurements, module size (in Watts), power rating of the array (in kWp) and estimated annual energy production (in kWh).

You need to be comfortable with the specification as you are making a large financial commitment. If you want it altered, then new drawings and calculations will be produced and re-submitted for your approval.

Your Energy Provider

Once the installation date is agreed, or even before, you must inform your energy provider who will send you the Feed-in Tariff (FIT) Application Form. This form must be completed and returned after installation and once you have received your MCS certificate. The date this application form is received is called the FIT Eligibility Date, and you will only receive the tariff from that date.

Installation

Residential installations rarely take longer than two days, and most can be completed in one. There are two distinct phases: the first phase involves the roof and the second the electrics.

Phase 1 – the roof: solar panels can be fitted in a portrait or landscape position and on virtually any type of roof: slate, clay, concrete, even flat (using specially constructed A-frames), but it’s the condition of the roof that matters. It has to support at least four panels and their roof anchors and rails for 25 years; if the structure is too weak, the installation won’t go ahead unless or until the relevant repairs have been done.

The best time to install the panels is when your property is being built or re-roofed as the rafters are exposed and it also gives you the opportunity to have recessed panels, rather than roof-mounted, for a flush fit.

Keeping the roof watertight is critical, so disruption to the tiles and felt is kept to an absolute minimum. Some tiles will need to be removed so that the roof anchors (which form part of the mounting system) can be screwed to the rafters at specific intervals, and are then replaced. The position of the roof anchors is important; if they are inaccurately placed, the rails, which sit on top of the tiles, will not be parallel and the panels will look uneven.

Phase 2 – the electrics: once the panels are connected to each other, the wiring (also known as strings), must first be connected to the inverter, which converts the direct current from the panels to alternating current. To get the wires to the inverter in the loft space a tile is removed and lead flashing put down. A hole is made in the flashing and a watertight grommet (also known as a gland) is inserted, through which the wires are fed. It is important that the wires enter the loft space through the overlap in the felt, not through the felt.

The wiring is connected to the PV generation meter, then to your consumer unit and finally to the National Grid. As soon as the system is commissioned, providing it’s daylight, you should see the light on your generation meter flashing red, which means you’ve just started generating your own electricity and lowering your carbon footprint.

*SAP is the Government’s Standard Assessment Procedure for Energy Rating of Dwellings. SAP 2005 is adopted by Government as part of the UK national methodology for calculation of the energy performance of buildings. It is used to demonstrate compliance with building regulations for dwellings – Part L (England and Wales), Section 6 (Scotland) and Part F (Northern Ireland) – and to provide energy ratings for dwellings.

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