System Types

The electricity used in the vast majority of domestic and commercial premises is known as AC (Alternating Current). The electricity produced by PV modules is the other sort; DC (Direct Current). Although it is possible to get electrical appliances that run on DC there is a limited choice and they are not very common. The solution is a piece of equipment called an inverter, this changes DC into AC with minimal (electrical) losses and is nearly always used in both stand alone and especially Grid connected systems.

STAND ALONE or GRID CONNECTED?

There are two ways of using the (clean, environmentally friendly) electricity produced from PV Modules. Either you can store the electricity they produce in batteries and use that energy to run your electrical appliances (Stand alone system). There is no facility to export your generated electricity back to the National Grid with a stand alone system. Or the electricity produced can be used to displace some of the electricity you would normally buy from the National Grid (Grid connected system). In times of low generation/high consumption this is supplemented by electricity drawn in the normal way from the National Grid through your energy supplier, and in times of high generation/low consumption it is sold back to them (more about this later), effectively using the National grid as a giant storage area.  
In reality it’s only remote areas (or special locations such as boats or recreational vehicles) that would consider a stand alone system, in cities and towns where a conventional supply is straightforward, a grid connected system is usually the logical choice. That covers the types of systems, now we come on to:

Available Systems

Ecovolt offers five basic types of systems:
Retro-fit:

Retro-fit means the PV modules are mounted on an aluminium frame just above (max. 150mm) your existing roof.
There are a number of advantages to this type of system. There is minimal disturbance to the roof structure and is therefore one of the quickest and easiest ways of installing modules on a pitched roof. This also means the system is more easily removed, although these systems are not really designed to move house with you. It is modular and is therefore easy to add to or change. Also, it costs less than most other installation methods.
Briefly, on tiled or slate roofs aluminium roof-hooks are fitted under the tiles. This is done in a number of different ways; fixing them to the rafters or securing them around the battens being just two. The tiles remain in their original places. These roof-hooks then have aluminium rails fixed to them, the rails are what the PV modules themselves are fixed to.
There are a number of different fixings available for modern commercial roofing materials.
There are no real disadvantages to this installation method.

Flat roof:

There are many installation options with flat roofs, the simplest being pre-formed recycled PVC ‘boxes’. These ‘boxes’ are not actually fixed to the roof but are weighed down with ballast (min. 55kg each, depending on size and the height of the building) for stability. The advantages are that they are at optimum tilt angle and can be orientated exactly due south. They are also the cheapest and quickest installation method
The disadvantages are that they are quite heavy and they need quite a bit of room (1.5m approx.) between rows to avoid shading each other in times of low sun.
If a new flat roof is required bespoke mounting brackets can be utilised to give strong mounting points for the modules. Ecovolt work with a partner who is a flat roof expert. This option is especially useful where there is a new dormer loft extension and space and/or load bearing are limited.

Semi integrated:

This method uses the same type of PV modules as retro-fitting, the difference being that where in a retro-fit your original roof stays in place, in a semi integrated system the tiles or slates are removed from the area in which the modules are to be fitted. These are then replaced with PVC undertrays which maintain the integrity of the weatherproofing and also become the fixing points for the modules.
The modules will be much closer to the original line of the roof that in a retro-fit but will still be slightly proud.
Semi integrated systems are more expensive than the same size retro-fit system due to more specialised kit and the extra roofing work involved, they are however cheaper than an equivalent size re-roof with PV tiles.

PV Tiles (Re-roof):

PV tiles are the most elegant, neatest and aesthetically pleasing type of installation, but also the most expensive.
A number of different types of tiles exist, most of which can be integrated with your existing tiles (some ordinary [non-PV] tiles have to surround the PV). In practice it is not often that the existing tiles can just be removed and replaced with PV tiles, or a roof can accept PV tiles without some re-battening. The best option is to remove everything and fit tiles that are designed to go with the PV.

Non-roof installation:

These are what they say, installations that are not on roofs. They can be ‘ground mounted’ i.e. bolted to a frame that sits on the ground, which has the disadvantage of taking up a lot of room, or pole mounted. Poles can either be static or motorized in order to take advantage of optimum positioning.

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