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Solar PV FAQs

Whatever the solar PV question, we have the answer.

A. General questions:

What does solar PV mean?

Solar PV is an abbreviated name for solar photovoltaic silicon panels. The ‘P’ refers to Photo indicating that photons of light radiation are used in the process and the ‘V’ refers to voltage, indicating that electricity is produced.

How does a solar PV system work?

Solar panels generate electricity, using energy from the sun. Because the panels produce electricity from daylight and not solar radiation they can still work on cloudy days. The direct current (DC) produced by the panels is converted to alternating current (AC) by an electrical device called an inverter. The electricity produced is either consumed directly by appliances in the building or, if more power is generated than required, it is exported to the National Grid. At night or when the system is not producing enough electricity, the National Grid supplies power to your home in the normal way.

Do the panels need direct sunlight to work?

Solar PV works from daylight and not direct sunlight, but more power is produced on a sunny day as opposed to an overcast or cloudy one. The more hours there are in a day, the more energy the system can produce, such as in northern areas of the UK. There are many more daylight hours in the summer than there are in the winter, however it is possible for CR Smith to calculate an estimate of the performance as an average over the course of the year.

How does shade affect a solar PV system?

Shading can have a very big affect on a solar PV system. Partial shading can also cause significant loss of energy because the panels are connected in line with each other. The panel with the lowest illumination determines the output of the whole system. CR Smith will generate technical drawings to estimate the optimal position of the panels on your roof to minimise the effects of shading.

What happens if there is a power cut?

If there is a power cut, the system automatically switches off as a safety measure to ensure power does not leak onto the mains, which could harm personnel working to restore the power supply. As soon as the power is restored the inverter will sense the presence of the electricity from the grid and within 3 minutes will automatically start producing electricity again. Battery back up systems are available, however batteries of this size are very expensive, highly environmentally un-friendly and can only be expected to last between 5 and 10 years.

What happens at night?

PV panels do not produce energy in the dark, so electricity is drawn from the Grid in the normal way.

Are there different types of solar products?

There are two distinct systems available:

Solar Thermal – Which is used to heat up water and so reduce the need to buy conventional fossil fuel energy sources.

Solar PV – Which is used to generate electricity and so reduce the need to buy power form the National Grid.

How to apply for the Feed -in Tariff?

Once CR Smith has has installed, tested and commissioned the Solar PV system, we will register the system with MCS. In the mean time you can contact your energy provider and ask for a Feed in Tariff application form. Once you receive the MCS registration certificate you can use the information on the certificate to complete your application form. Your system will not be registered with MCS until payment has been made in full. Your feed-in tariff payments will be made under your electricity provider’s terms and conditions. Please note that these conditions may be different depending on the supplier.

B. Installation

Is Planning Permission required?

Roof mounted solar PV systems fall under Permitted Development Rights, so as long as the system is not installed more than 200mm (8”) from the roof and does not protrude higher than the ridge, Planning Permission is not required. However, if the building is listed, in a conservation area or in a World Heritage Site then Planning Permission will be required.

Is a Building Warrant required?

CR Smith will carry out a risk assessment on all properties before designing a Solar PV system. If we believe your roof is not capable of withstanding the extra weight or wind load we will commission a Structural Engineering Report from a third party chartered engineer. If the engineer deems the roof incapable of supporting the load then CR Smith can carry out the required modifications to make the installation possible. The Scottish Building Standards division require a building warrant if modification to the roof truss is required. CR Smith will carry out the whole application process for you.

Will the building need reinforcement?

Most roofs are strong enough to support a PV installation without reinforcement. However in Scotland and areas with high wind and snow loads, reinforcement may be required. We have also identified that in general, modern new built houses have not been designed to withstand the extra load from a Solar PV system. A chartered engineer will identify how much reinforcement is required. Based on the roof timber specification, layout of the roof truss, height of the building, location, topography and roof covering type.

Do I need to inform the electricity supplier?

For systems less than 4kw peak power we will inform your electricity supplier once your installation is complete. For larger systems, permission will need to be gained in advance from the Distribution Network Operator.

How much roof space do I need?

CR Smith systems start at 1.3kW peak power, which will occupy around 9m². A 4kW peak power system can cover an area of up to 25m^2.

How long will the installation take?

Installation will take from 1 to 3 days depending on the size of the system, easy of access, reinforcement required and weather conditions.

What are the optimum conditions for a solar PV system?

Panels can be installed at different angles on west or east facing roofs. However they work best when installed at an angle of 30^o to 40^o from horizontal, on a south-facing roof. A site survey will determine the best option for your property.

Can anyone buy and install a PV system?

PV systems are available from specialist distributors, electrical wholesalers and renewable merchants and must be installed by an MCS accredited installer. If the system is not installed by an MCS accredited installer, it will not be covered by a warranty or be eligible for the Feed-in Tariff.

What is MCS?

The Microgeneration Certification Scheme (MCS) was set up to ensure all products and services related to the installation of renewable energy products complies with internationally recognised quality assurance scheme. To be eligible for the Feed in Tariff, both the products used and all installers, whether subcontracted or not must have MCS certification.

Does the system need batteries?

Solar PV systems are designed to be connected to the grid and do not require batteries. Excess electricity generated during the day is fed back to the National Grid. An automatic switch and battery pack can be integrated into the system for use in remote areas, however it can add significant cost.

C. Maintenance

Do the panels need cleaning?

If the panels are installed at an angle of more than 15^o then rain should be sufficient to clean the panels. In areas of heavy pollution or when soiled with organic material, a power reduction of about 10% can be experienced.

How long do the panels last?

As an example, Schuco PV panels come with a 5-year product warranty but can be expected to last for up to 40 years. They come with a 90% performance warranty for 12 years and this output is guaranteed not to drop below 80% over 25 years.

Do any of the parts need servicing?

There are no moving parts in a solar PV system so regular cleaning or lubrication is not required. The inverter is an electronic device and may not last the life of the system. You should anticipate having to replace the inverter at least once during this time. In areas of heavy pollution or when soiled with organic material, a power reduction of about 10% can be experienced.

D. Costs & Benefits

How much does it cost?

The total installed cost depends on the size or peak power of the system and ease of installation. The premises must be surveyed to determine how much scaffolding and reinforcement is required. PV Systems can range from £7000 - £13,000. Economies of scale allow us to reduce the price per kilowatt significantly, the larger the system gets.

Is VAT included in the price?

VAT is included in the price however it is currently only charged at 5% for the installation of renewable energy systems.

How much energy will a system generate?

There are 5 main factors, which affect how much energy a PV system will generate:

Total peak power size of the solar PV system
Latitude and location
Direction the panel faces
Angle the panels are mounted at
Any shading factors

What is the Feed-in Tariff and how does it work?

It is a financial incentive backed by the government and funded by your energy supplier, to encourage people to create their own renewable electricity. Every unit of electricity generated currently earns a fixed amount of 21p/kWh and additionally any electricity not consumed in the property can be sold back to the grid for 3.1p/kWh. For systems smaller than 4kW your energy provider will estimate that you will export 50% of what you make. These payments are indexed linked to the Retail Price Index so they are adjusted to inflation each year.

Will the system be eligible for the Feed-in Tariff?

All solar PV components fitted by CR Smith Energy are MCS certified and are installed by MCS accredited personnel. This means you will be able to claim the Feed-in Tariff and we will assist you with this.

What kind of return and savings can I expect?

The feed in tariff can pay out, as much as £800 in the first year and this payment will increase with inflation year on year. As you will be paid for exporting 50% of the electricity, it is possible to generate an extra £50 a year from this, this payment will also be subject to inflation. Depending on how much of the power from the system you use, it is possible to save up to £400 on your current electricity bill. The more expensive electricity gets, the better insulated from its effects you will be.

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