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FAQ
Q: What is the difference between a kilowatt (kW) and a kilowatt hour ( kWh)?
A: A kW is a thousand watts and a unit of power. It measures the rate of energy conversion.
A kWh is the amount of work done, or energy used, when a kW of power works for one hour.
Q: What is a kWp, and how does it relate to kW and kWh
A: A kWp is the kilowatt 'peak' of a system.
This is a standardised test for panels across all manufacturers to ensure that the values listed are capable of comparison.
The test conditions for module performance are generally rated under Standard Test Conditions (STC) : irradiance of 1,000 W/m2, a module temperature at 250C and a solar spectrum of AM 1.5.
Q: How does the system work?
A: Daylight hits the photovoltaic cells and is converted to clean electricity. The inverter converts the electricity from direct to alternating current, for use in the home.
When the solar energy system is producing more power than is needed it is exported to the grid.
At night, power is imported from the grid in the normal way.
Q: Will they work in the UK and during the winter?
A: Yes. Solar panel suppliers have enhanced the efficiency of solar power systems to the extent that it is now a very viable option even in cloudier climates.
The important thing to bear in mind is that solar power depends on intensity of light, not necessarily direct sunlight. So even when it's overcast, your solar panels will be producing clean electricity to help power your home.
Q: What happens if there is a power cut?
A: Our photovoltaic systems for homes are mostly grid connected.
If there is a power cut your system is automatically switched off. This is a safety measure designed to stop electricity leaking on to the national grid and to protect individuals who may be working to restore the power supply.
Q: Does the system need batteries?
A: No, the system is connected to the national grid.
In the night, when the cells are not generating energy, electricity is bought from the utility company in the normal way. Any excess electricity generated during the day, for example when you are at work, is sold back to the utility company.
Batteries are only required if you want a truly off-grid solution and independence from any power cuts that might occur.
They are also required if you own a property which is not attached to the grid in order that power produced during the day can be stored for use in the evening.
Batteries add significant costs to a solar system so are normally only offered on specific request.
Q: How much energy do I need?
A: According to the Energy Saving Trust, the average 3 bedroom house consumes 3,300 units of electricity (kWh) a year (cooking and heating using non electric supply).
However, we always recommend that you look at your last few bills or call your electricity supplier to find out how many units you consume, you can then compare this to the output of the system we recommend.
Q: What if I produce more energy than I need?
A: Whenever your panels are producing more electricity than your home is using, it will flow back into the grid for other homes to use.
As long as you have an arrangement with your energy company, you'll be paid for this power so you can be sure your energy bills will be even less and none of your clean, green electricity will be wasted.
Q: What is wrong with wind power?
A: Wind power is an excellent technology and vital in the renewable energy mix required to wean Britain off its unsustainable fossil fuel addiction.
However, it requires a lot of space and is only practical when there is an average wind-speed of around 6m/s.
This means that it is rarely suitable within an urban landscape. Even when placed rurally it is still constrained by planning permission.
Q: Can I get a grant from the government for my panels?
A: No, grants have been replaced with the much awaited Feed In Tariffs (FIT's) which came in to affect in April 2010
Q: What are FIT's?
A: Fit's stands for Feed In Tariffs. This is the Tariff that came in to effect in April 2010 and replaced the previous grant system. FIT's is designed to pay the producer of the green energy a tariff for all the electricity produced whether it is used or not, once the system has been installed and commissioned by a MCS affiliated contractor you will be paid for all the electricity produced for the next 25years.
Q: How long will it take to install my system?
A: PV systems can be installed and ready to produce electricity in a few weeks from the time the design has been agreed. Depending on the size of your system our technicians should have it up and running within a few days after arriving on site.
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 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 recommend the size of system for you.
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 more than 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 part of the garden, or you could also use the system to cover a porch or patio.
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.
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).
For every 1kW of maximum production, it can be estimated that, in Britain, 900kWh of energy will be produced over an average year.
Q: How is the angle of optimum panel inclination found for different latitudes in 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:
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You have to pay 17.5% VAT on the PV cells rather than the 5% using an accredited dealer.
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You might void the manufacturer's warranties.
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You might not have a functional system after spending your hard-earned money on the system.
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Electricity can be dangerous; you might get hurt.
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You might damage your home or appliances during installation.
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You will not be able to claim the FIT unless the system is installed by a MCS accredited installer.
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.
Q: How long do photovoltaic (PV) systems last?
A: A PV system that is designed, installed, and maintained well will operate for more than 20 years.
The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years.
Q: What maintenance and cleaning do the systems need?
A: Solar photovoltaic panels are silent in operation, have no moving parts and require very little maintenance.
Most of the time the rain will keep the modules clean. However, a build up of dirt can affect system performance. The degree of soiling will depend on the location but usually dust accumulation and self-cleaning reach a steady state after a few weeks if the array tilt is at least 15 degrees. In extreme cases dust may cause a power reduction of about 10%.
At low tilts horizontal-glazing bars can trap debris, which could lead to shading of part of the array. The design of the system should aim to minimise uneven soiling.
The modules can be cleaned with either a hose or, if possible, soapy water and a non-abrasive brush.
Q: Doesn't the glazed front reflect light away from solar photovoltaic (PV) modules?
A: Not really, no. Solar PV modules constructed with a glass front have two characteristics that reduce light reflection.
In order to optimise electrical yield the glass is treated with an anti-reflective coating which greatly increases the transmittance through the glass so to maximise the amount of light reaching the solar cells.
Secondly the outer face of the glass has a slight granular texture.
The result is a matt like finish rather than a mirrored, again this is actually intended to maximise yield.
These two characteristics greatly reduce reflection from the glazed front face of solar PV modules when compared with conventional glazing
Q: Will I ever have to go without power?
A: Your home will still be connected to the National grid. If at any time your solar panels are producing less electricity than your home is using, or at night time, you will just receive electricity in the normal way.
Only if there is a power cut will you not be able to generate electricity.
Q: How long do PV systems last?
A: A well-designed PV system will operate for more than 20 years.
The PV module, with no moving parts, has an expected lifetime exceeding 30 years.
Experience shows most system problems occur because of poor or sloppy installation. Failed connections, insufficient wire size, components not rated for dc application, and so on, are the main culprits.
The next most common cause of problems is the failure of electronic parts included in the Balance of Systems (BOS) - the controller, inverter, and protection components.
The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly.
It is estimated that performance will decrease by under 1% per year, which would mean that in 50 years they'd still be 60% efficient, but nobody really knows past the guarantees given.
We only use MCS accredited parts and simply do not have problems after installation, it is a fit and forget product.
Convert sunlight to electricity ~ Home solar panels ~ Photovoltaic solar panel ~ PV solar panel
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