Types of Solar PV System

Roof Mounted

Mounting solar PV arrays on an existing roof is generally the first possibility to explore when considering an installation.

• The roof must be generally South facing, have a clear horizon and not be substantially over shadowed by trees or other structures throughout daylight hours.
• The roof must be in good condition with the roofing material, slates, tiles, corrugated sheets or similar, having an expected life of a further 25 years or more. Installing a new PV system over a roof which requires substantial maintenance within a few years can prove to be very expensive.
• The roof structure must be strong enough to support the additional weight of the array and fixings.
• The roof area available must be large enough to accommodate the number of panels required to achieve the desired output.

The pitch of the roof is not usually critical as the angle of the array can be optimised for maximum light using angled brackets in the mounting arrangements. Even flat roofs and vertical walls can be suitable and are frequently used. The available roof area on domestic houses can usually provide between 1 kWp and 4 kWp of output. This size of installation generally comes within "Permitted Development” and subject to some constraints requires no Local Planning Authority approvals. The installation of solar panels on farm buildings is also generally categorised as "Permitted Development"

Much larger roofs like cattle or sheep sheds, barns, chicken houses and grain stores can offer sufficient area for 20kWp up to 250kWp. For larger projects the capacity and rating of the local mains electricity connection is an essential part of the survey and subsequent planning of the project.

Ground Mounted

Where it is not possible to use existing roofs to generate the required output then mounting the arrays on simple ground based support structures offers many advantages. System sizes can be from 1 kWp in a back garden up to Solar Farms of 1 MWp or more. Ground mounted systems are increasingly installed on farms utilising areas which are unsuitable for arable cultivation. Careful design and siting of the structures permit year round grazing under the arrays by sheep in particular. Steeply sloping South facing hillsides have been used to advantage providing that the connection to the national grid is within reasonable distance.

Tracking Systems

We all know that as our planet Earth rotates on its axis the Sun appears to rise in the East before passing overhead and disappearing again into the Western horizon. The actual track that the Sun follows depends upon the time of year, lower in Winter and higher in summer. A Solar tracking system has the PV array mounted on a structure which is capable of following the Sun’s path throughout the day and therefore optimising the output throughout daylight hours. These are usually ground mounted and each array can be between 1 kWp and 8 kWp depending on the application. In a two axis tracking system, a light sensor is used to direct the array towards the brightest light source which is not always directly towards the sun, especially on a cloudy day. The annual output of tracking installations can be as much as 35% higher than a fixed installation providing for an increased financial return even after the increased cost of the unit. Tracking systems are most popular in lower latitudes which experience longer daylight hours.

In some countries Solar PV "trees” are now commonplace. These are very efficient Solar trackers supporting a number of arrays, all disguised to look like an actual tree.