Is My Property Suitable?

Q: Does Green Planet service the whole of the UK?

A: Yes, we service all of the UK except Northern Ireland.

Q: How long will it take to install my system?

A: PV systems can be installed and ready to produce electricty in 2-8 weeks from the time the design has been agreed.

Q: Can I use photovoltaics (PV) to power my business?

A: PV systems can be blended into virtually every conceivable structure for commercial buildings.  You will find PV being used outdoors for security lighting as well as in structures that serve as covers for parking lots and bus shelters, generating power at the same time.  Indoors, PV systems are used to offset and operate all kinds of electrical systems, including lights, cooling systems, and appliances.

Today’s modules can be built into glass skylights and walls.  Some resemble traditional roof shingles.  Architects can use building-integrated PV to design buildings that are environmentally responsive, aesthetically pleasing, and produce their own power.  Building-integrated PV provides a dual-use building material, reduces PV system costs by using the building as the mounting or support structure, and reduces utility bills through on-site power production.

Q: Can I use photovoltaics (PV) to power my home?

A: PV can be used to power your entire home’s electrical systems, including lights, cooling systems, and appliances. PV systems today can be blended easily into both traditional and non-traditional homes. The most common practice is to mount modules onto a south-facing roof or wall. For an additional aesthetic appeal, some modules resemble traditional roof shingles or can be built right into glass skylights and walls. This building-integrated PV provides a dual-use building material, reduces PV system costs by using the building as the mounting or support structure, and reduces utility bills with on-site power production.

Q: What sort of projects are suitable for solar installations?

A: A project with a brief incorporating social and technical innovation is an ideal candidate for building-integrated PV (BIPV).  The most important aspect to consider is the location of the site.  The solar installation must receive as much light as possible.  Shadows cast by tall trees and neighbouring buildings must be kept in mind during the design process.  The best location for solar PV is on the south-facing roof or side of a building.

Q: How big a solar energy system do I need?

A: The size of solar system you need depends on several factors such as how much electricity or hot water or space heat you use, how much sunshine is available where you are, the size of your roof, and how much you’re willing to invest.  After talking through your exact needs we will be well placed to recommend the size of system you use.

Q: How do I know if I have enough sunlight for PV?

A: A photovoltaic (PV) system needs unobstructed access to the sun’s rays for most or all of the day. Climate is not really a concern, because PV systems are relatively unaffected by severe weather. In fact, some PV modules actually work better in colder weather.  Most PV modules are angled to catch the sun’s rays, so any snow that collects on them usually melts quickly. There is thus enough sunlight to make solar energy systems useful and effective nearly everywhere in the United Kingdom.

Even hail won’t damage most PV systems. Most homes have adequate roof space for a PV system, but you will have to size your system first to discover how much space is required. If you don”t have adequate roof space, look at other options such as integrating the system into a wall or putting the system in the backyard. You could also use the system to cover a porch or patio in the backyard or mount the system on the roof or wall of a garage. Remember: an energy-efficient building requires a smaller PV system.

Q: What are the effects of shade?

A: Shading is critical.  Minor shading can result in significant loss of energy.  This is because the cell with the lowest illumination determines the operating current of the series string in which it is connected.  This is one of the areas covered in the survey carried out before any installation.  We use modern arrays that can bypass the affected diodes to minimise shade effects; but these effects must still be considered.

If shading is unavoidable, or poor light is expected on a regular basis, then we will modify our designs and possibly even the type of cell we use.  This can obviously only be taken on a case by case scenario.

Q: How can the energy outputs of the different products be estimated?

A: The following energy outputs can be used as a rough rule of thumb for the UK (assuming a reasonable tilt, orientation and system efficiency).  The panels shown in the products section all give the size dimensions and the maximum expected power for each panel.  For every 1kW of maximum production, it can be estimated that, in Britain, 800kWh of energy will be produced over an average year.

Q: How is the angle of optimum panel inclination found for different latitudes within the UK?

A: The maximum total annual solar radiation is usually at an orientation due south and at a tilt from the horizontal equal to the latitude of the site minus approximately 10-15 degrees. For example 30 degrees is an optimal tilt in Southern England, increasing to almost 40 degrees in Northern Scotland.

Q: How do the panels perform at different angles and orientations?

A: If the optimum angle is not achievable, over 90% of the maximum annual energy can still be achieved at 10 degree and 50 degree tilts. South-facing vertical facades generate around 70% of the maximum.

Q: Can I design and install a photovoltaic (PV) system myself?

A: Maybe! However, unless you are very handy or experienced in home wiring, we suggest using experienced professionals to design and install anything more than the simplest application, for the following reasons:

• You have to pay 15% VAT on the PV cells rather than the 5% accredited dealers.
• You might void the manufacturer’s warranties.
• You might not have a functional system after spending your hard-earned money on the system.
• Electricity can be dangerous; you might get hurt.
• You might damage your home or appliances during installation.

The goal of a stand-alone system designer is to assure customer satisfaction by providing a well-designed, durable system with a 20-year life expectancy (or more). This depends on sound design, specification and procurement of quality components, good engineering and installation practices, and a consistent preventive maintenance program.

A thorough knowledge of the availability, performance, and cost of components is the key to good system design.  Price/performance trade-offs should be made and re-evaluated throughout the design process.  When you start your design, obtain as much information as you can about the components you might use.  After studying all the issues, you can do an initial sizing of the PV system and get some ideas about specifying system components.  Extra points to remember are:

• Method of fixing/ integration into the fabric must be detailed.
• Ensure that the fixing does not cover or shade any part of the PV cells.
• PV laminates are often constructed with only a narrow border.
• The fixing must allow for thermal expansion without breaking the glass.
• Weather sealing involves standard construction practices but all materials must be suitable for the temperatures likely to be met (i.e. temperatures at the back of the modules can rise to 80ºC if they are poorly ventilated or higher if they are directly insulated).
• The mounting option must allow for safe maintenance and possible replacement of individual modules.
• The life of the support structure must be at least that of the PV array. The preferred materials are aluminium, stainless steel or glass-fibre. Protection from corrosion is important especially as residual currents may be present.
• Wind loading
• Any extra weight
• How and where to run electrical wiring ( this may penetrate the waterproof skin)
• Where to place junction boxes.

Q: How can the energy benefits of the PV cells be maximised?

A: Orientation, shading and the temperature of the PV elements all impact on their output and must be considered at the design stage. Of course, the more energy efficient the building, the greater the overall benefit of the PV cells.  Some PV products have now been designed to provide thermal insulation as well as electricity – eg flat roof systems and solar metal roofing systems that include insulation and solar glass laminates with low emissivity glass.

Q: What are the relevant codes of practice and articles of legislation?

A: British Standards
BS EN 61215
BS EN 61646
The Electric Supply Regulations 1988
The Building Regulations 1991 (and amendments)
The Construction (Design and Management) Regulations 1994
A ‘Power purchase agreement’ will need to be negotiated if electricity is to be sold.  This is not as tricky as it sounds as electricity networks and supply companies are legally obliged to cooperate with solar installations.   This is also something that Green Planet will help with.