Solar PV

Renewable power encompasses a range of technologies that generate electricity from renewable sources such as sun, wind and water.

Solar photovoltaic or solar PV as it is commonly known is probably the most flexible renewable power technologies as it can be deployed almost anywhere in the country with a high degree of operational certainty and, with no moving parts, it requires practically no maintenance once installed.

Photovoltaics is the process by which a “semi-conductor” material turns light (“photo”) into a small amount of electricity (“volt”). When the semi-conductor material is formed into a cell and linked to many more cells to form a panel and that panel is linked to other panels the electricity generated can be harnessed by a solar PV system.

A solar PV system consists of a PV array (a number of connected solar pv panels) that generates electricity, and a dedicated electrical circuit (typically linked into the main building supply) that enables this electricity to be utilised within the building and any surplus exported to the grid.

PV arrays are often mounted on buildings, ideally facing due south, and more often than not with the panels tilted to be at or near the optimum angle for solar energy collection. Alternatively, an array can be mounted on a dedicated structure on the ground which may even be engineered to track the sun through the day and alter the angle of tilt with the seasons.

The key component of the electrical circuit is the inverter which converts the DC electricity generated by the PV array into AC electricity that can be synchronised with the buildings power supply and the National Grid.

The key benefit to a solar PV system is that the electricity it generates is 100% renewable, but they also have a number of other important benefits, particularly in comparison to other renewable energy generators:

Few planning restrictions
Easy to retrofit
Long system life (40+ years)
Low maintenance
Silent operation

Ecofirst is highly experienced in the installation of solar PV and with a nationwide contract to install domestic solar PV systems for RWE npower, one of the UK’s foremost energy suppliers, we are well versed in meeting the demands of our customers for very high standards of workmanship and customer service.

Other key solar PV customers include the Forestry Commission, Access Self Storage, and a wide range of councils, housing associations and private developers.

Building Mounted Solar PV Systems

Mounting a solar PV system on a building and connecting it directly to the incoming electrical supply enables the occupier to take full advantage of the power generated.

Solar PV arrays can be installed on a wide variety of building elements but roof mounted systems are usually the most efficient as they are naturally positioned to capture the most sunlight without being subject to shading by other elements of the building.

Pitched Roofs
On pitched roofs the angle of tilt of the module is generally dictated by the pitch of the roof. On very low pitch roofs it is sometimes worthwhile using a mounting system that raises the tilt of the panels closer to the optimum but additional cost and/or loading restrictions may preclude this. On most pitched roofs the mounting system will consist of a series of aluminium rails onto which the panels are fixed. The spacing and length of the rails is dictated by the type and number of modules.

The rails are held in place by mechanical fixings, normally referred to as roof anchors. The appropriate type of roof anchor will generally be dictated by the type of roof covering. Most roof anchors pass through the roof covering and are fixed into structural elements below, i.e. rafters, but some metal roofs have sufficient inherent strength to allow the anchors to be screwed or clamped directly onto the metal sheets thus avoiding the need to create penetrations.

Tile / slate roof fixing

Profiled metal roof fixing

Standing seam metal roof fixing

Flat Roofs
Where a PV array is installed on a flat roof, it is generally recommended to raise the angle of tilt of the PV panels by fixing them to a pitched mounting system. These mounting systems typically take the form of metal framed structures or plastic “trays” and are usually mechanically fixed or ballasted. There are also specialist “tray” type products available that use aerodynamics to significantly reduce the amount of ballast that would normally be required.

Where having a mounting system is not possible (usually due to planning restrictions or limitations on loadings etc.) an alternative is to lay flexible PV laminates directly onto the roof and glue or weld (heat seal) them in place.

Ballasted "trays"

Aerodynamic (low ballast) "trays"

Mechanically fixed or ballasted frame

Façades & Glazing
Installing a PV array on the roof of a building is generally the most practical and efficient solution but if required (usually for reasons of enhancing visibility or making an architectural statement) PV panels can be mounted on a building’s façade or incorporated in areas of glazing.

On solid façades solar PV panels can be mounted over an existing cladding or as an integral element in their own right. Panels may also be incorporated in a façade as “bolt-on” elements such as brise soleil, louvers or canopies. Glass-glass PV laminates can be used instead of traditional glazing in almost any situation where glazing is specified. As the majority of glass-glass laminates are bespoke it is usually possible to specify the spacing of the cells in order to maximise either the amount of light or shading the panel will provide.

A significant downside to both PV façades and PV glazing is their cost effectiveness. The output of a vertically mounted PV panel is significantly lower than that of a pitched or even flat mounted panel so for an array of a given size (kWp) the amount of electricity produced per annum will be relatively low. Whilst an area of glazing may be more suitably pitched, the bespoke nature of glass-glass laminates typically makes them significantly more expensive than standard modules so the size of PV system you get for a given capital outlay is relatively small.

Ground Mounted Solar PV Systems

Introduction
Ground mounted solar PV systems offer an alternative solution in situations where a building mounted installation isn’t an option.

Systems can vary in size from small, single-figure kilowatt arrays built within the grounds of a building to multi-megawatt “solar parks” or “PV farms” constructed on large areas of brownfield or low grade agricultural land. Regardless of scale, the design and construction principles of ground mounted solar PV systems are usually the same with the PV array being fitted to a dedicated mounting structure fixed directly to the ground and the inverters installed either immediately below or within a dedicated enclosure constructed nearby.

Mounting structures
Mounting structures can take many forms but most consist of a metal framework set at the optimal pitch and orientation and fixed to a suitable foundation. To maximise system output the structure can be made to be adjustable such that the PV array will track the path of the sun during the course of the day and/or the angle of the sun across the seasons. These adjustable structures can be mechanised and are commonly referred to as trackers.

Maintaining land use
Ground mounted solar PV systems installed in fields can be constructed in such a way that sheep can graze below the mounting frames. This has the two-fold benefit of retaining an agricultural use for the land and keeping the grass down in order to avoid shading. Ground mount structures can also be designed to provide additional amenity such as shelter as in the case of solar PV “carports”.

Foundations
Wherever possible Ecofirst use ground screws to anchor the mounting frames as these are more environmentally friendly than concrete pile or raft foundations. Additionally, when in future the system is decommissioned the screws can be easily removed and the land returned to its original use with minimal reparation work.

Where ground screws are not appropriate, there are a number of alternative methods of anchoring ground mount frames and Ecofirst engineers can tailor solutions to meet most ground conditions.