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A Solar PV system generates electricity that is supplied direct to the building’s distribution board where any load such as lighting, TV, washing machine etc. immediately consumes that electricity when required.

 

During times of excess generation of electricity, due to low electrical loads for example, the electricity will flow past your meter to the grid outside and can be sold to your local electricity suppler. It must be noted here that if you have an old-fashioned mechanical electric meter, the meter will turn backwards when this occurs, resulting in a lower meter reading than should actually be so. If you wish to sell the excess electricity then your local supplier will require that you replace the meter with a digital version whereby such double counting will not occur. Solar PV systems are simple semi conducting devices that require any form of light to generate electricity. This relationship is proportional.

Diffuse overcast days with grey, miserable sunlight will generate electricity regardless of cold and rain. However, glorious sunny days will ensure that the Solar PV system performs more efficiently, although energy can still be produced in overcast or cloudy conditions. The solar PV panels that we sell are generally blue or grey in colour and will operate successfully in all parts of the UK, offsetting your reliance upon conventional grid electricity and so reducing your electricity bills.

Our systems consist of semi conductor cells connected together to form modules. Each module is then connected together to form a panel. The panels generate Direct Current (DC) electricity that is

converted to Alternating Current (AC) via an inverter and fed into the buildings mains supply.

 

Photovoltaic panels have a very long life of 20-25 yrs and very low maintenance costs, requiring little more than the occasional cleaning. The DC/AC inverters however, have shorter lifespans of 10-15 years and replacements will be required during the lifetime of the system. Enviko have found that during system inverter replacement our customers have preferred to replace the panels with better, higher efficiency devices to maximise the contribution from the sun in their home.

 

Basic Layout of Grid Tied PV system

 

 

Other tehnical issues to take into account:

 

• Solar PV panels should ideally face between south-east and south-west, at an elevation of about 30-40° although arrays pointing east or west are acceptable (albeit at lower performance) especially for roofs inclined at a low angle to the horizontal.
• Arrays should NOT be horizontal as the rain will be unable to wash them clean.
• Systems should be in locations that will be un-shaded at all times of day if possible. Gable roofs, chimneys, cables, TV aerials, trees and other buildings in the vicinity should be identified as potentially shading the modules, particularly in the early morning or early afternoon. The performance of a whole panel will be affected even if only part of it is shaded.
• Solar PV systems need to be ventilated so that they don’t heat up - their efficiency decreases as their temperature rises. Suitable ventilation is easier to ensure for bolt-on systems. Rear ventilation is less important for some thin film modules which can be mounted directly onto the roof cover. Regardless of system type this is not usually a problem, Enviko can ensure that suitable natural ventilation will take place when installing the system.
• If retrofitting systems to existing buildings, the system must be carefully positioned on the roof to take account of the loading capacity of the roof.
• Unfortunately, the potential for vandalism should be assessed if the system can be seen from the ground or if it is accessible due to raised pavements or other buildings. Sometimes it is necessary to cover panels with heavy duty Perspex to protect them from thrown objects.
• Care must be taken if the systems are to be fitted to social housing properties (or other properties) with pre-payment meters as some meters do not allow the export of electricity and can be damaged by attempted export.
• If a photovoltaic system cannot be installed at time of build, the electrical systems of the building should be prepared to facilitate later retrofitting. This would include an extra 3 ways in the fuse board and an extra fuse spur extending into the roof space. The design of a building should always, where practicable, be suitable to support solar technologies at a later date.

Grid connection

There are no licensing requirements relating to photovoltaic systems, however the consent of the local Distribution Network Operator (DNO) is required to connect the system to the grid (in the London area this is EDF Energy).

The DNO is an entity licensed to distribute electricity through cables and has a duty to provide connections to premises. In London the DNO is EDF Energy, with a small part of the west of London covered by Scottish and Southern Energy. Enviko undertake all necessary paperwork and submissions for connection to the grid.

For further outline details, however, you can consult OFGEM guidance ‘How to get connected to electricity supply’.

or consult ‘A Technical Guide to the Connection of Generation to the Distribution Network’ published in February 2004.

There is generally no charge currently for small (household) photovoltaic systems due to changes in standards. There is likely to be some charge for bigger schemes and this will be dependent on the size of the scheme and the nature of the network that the installation is being connected to.

Since April 2005, the regulator has given an incentive to DNOs to connect embedded generation schemes to the grid. (Embedded generation schemes are energy generating systems such as small-scale renewable energy systems which will only export to the grid when they generate more than their base-load requirement).

 

Please feel free to get in contact with us by email or call 0845 189 9894 to discuss any of your requirements.