It is widely accepted that the increase in so-called greenhouse gases, such as carbon dioxide (CO2), from the burning of fossil fuels, is having a major impact upon the planet’s climate and there is now a growing imperative to reduce our dependence on fossil fuels and the amount of carbon dioxide within the Earth’s atmosphere. Solar PV addresses this problem.
Solar hot water systems use the heat of the sun to warm a liquid that flows through solar collectors (usually situated on the roof) which in turn heats water in a storage cylinder producing hot water at the taps or for a shower. Solar electricity systems use solar cells to convert the energy from the sun into electricity to power electrical appliances within a building or to be exported to the National Grid.
Solar electricity generates electricity from daylight. When two different conductor materials touch, and light shines on them, a potential difference is created. This is known as a voltage, and is what creates the current which flows along a wire and causes the transmittance of electromagnetic energy. The more light that shines on the panel each year, the more electricity it produces.
An inverter converts the electricity from DC to AC for use in the home. When the solar electricity system is producing more power than is needed within the home it is exported to the grid and you receive money from your electricity company. At night, when the solar system is not producing any electricity, or at a time when more electricity is required within the home than is being produced by the solar system, electricity is imported from the grid in the normal way.
A more technical explanation: a PV cell is made up of two thin layers of semi-conducting material (silicon) that generate electricity when exposed to daylight and when light shines on a PV cell the material absorbs some of the light particles called photons. When a photon is absorbed, an electron is released within one layer of the semi-conducting material. These ‘free’ electrons will be attracted towards the other layer of semi-conducting material so they move across the boundary between the layers and this movement creates a flow of electricity between the two layers within a cell.
Solar electricity is a proven technology that has a long history and a relationship to many of mankind’s greatest technological achievements, including space vehicles such as Sputnik III and Explorer VII. Germany in particular has been at the forefront of a solar cell revolution for many years. The German government has invested in a number of major solar electricity programmes and in 2000 they introduced a means by which people could earn money from photovoltaic arrays. This is known as a Feed-in Tariff (see Q14.). The policy is the benchmark by which other countries measure their own Feed-in Tariff policies.
Both Direct Current (DC) and Alternating Current (AC) are a flow of electrons, but direct current is steady, flows in one direction (hence, it flows directly) and remains at a constant level while alternating current rises and falls as the electrons continually change direction (hence, it alternates). A simple way to think of AC and DC is to consider an upside down bicycle wheel. DC would be you spinning the wheel in one direction very quickly, while AC would be you spinning the wheel quickly one way and then the other. Either way, the energy generated by this movement will make your fingers hot when you touch the wheel.
• Reduce and future-proof your fuel bills – once you have paid for the initial installation your bills for producing electricity will be significantly reduced (depending on the size of the system) for the lifetime of the system (potentially up to 35 years).
• Earn an income – with the introduction of the Government’s Feed-in Tariff in April 2010 you can be paid by your electricity company for the electricity your system generates at above-market rates (see Q.14 relating to Feed-in-Tariffs).
• Long lifespan - PV cells are estimated to have a lifespan of 30 to 35 years on average, therefore repaying their embodied energy tenfold over their lifetime.
• Cut your carbon footprint – solar electricity uses the renewable resource of the sun and does not release any harmful carbon dioxide or other pollutants.
• Solar electricity requires very little maintenance, has no moving parts and is silent in operation once installed.
A solar electricity system is made up of a number of different components including the solar electricity or PV panels themselves (usually located on the roof of a building) plus the framework on which it sits; an inverter that converts the direct current (DC) produced by the solar panels into alternating current (AC) required by the electrical system within a home, a total generation meter, some switchgear and some wiring
The standard type of panels that we offer through the scheme are poly-crystalline cells, which are effectively a slice cut from a block of silicon, consisting of a large number of crystals. The panels have a speckled reflective appearance. These cells are an affordable option, ideal for domestic residences.
However, on request we can supply mono-crystalline cells, which are cut from a single crystal of silicon and have a smooth texture. These cells are slightly more efficient than the poly-crystalline panels but are usually more expensive. They tend to be the types used on schools and commercial buildings.
NB: All panels are rigid and require mounting in a frame which, in most cases, is mechanically fixed to the roof of a building.
This is dependent on a number of factors, especially the total size of the solar panels installed, the type of panels used, the orientation of the solar panels (due south facing is best), the angle of the solar panels from the horizontal (ideally 30°-45°), and whether the proposed location for the solar panels is subject to any shading. According to the Energy Saving Trust, the average 3-bedroom house uses 3,300 units or kilowatt hours (kWh) of electricity per year although this is an average and will vary from property to property. Each kWp (kilowatt peak) of solar electricity produces between 800 and 1,200 kWh per year depending on the factors listed above. Therefore, to produce all of the electricity required for an average household, the PV array would need to be around 3-4 kWp. However, it is not essential to provide all of your homes electricity needs from a solar electricity system as you will still be connected to the national grid.
No, the system is connected to the national grid. During the night, when the cells are not generating energy, electricity is imported from the national grid in the normal way. Any excess electricity generated during the day, for example when you are at work, is exported back to the grid.
This will all be done for you as part of the installation. Permission is required to connect a system to the distribution network but this is usually not a problem for any system up to 4kWp
Yes you get paid. All electricity suppliers in the UK are obliged to provide more and more of their electricity from renewable sources and will purchase the electricity generated by householders. The government has introduced a new ‘feed-in tariff’ which came into effect in April 2010 and requires electricity suppliers to buy renewable electricity at fixed above-market rates.
The government introduced a new feed-in tariff (FIT) in April 2010 to incentivise householders and businesses that install microgeneration technologies. Under this new feed-in-tariff, fuel utility companies are obliged to purchase renewable electricity at fixed above-market rates which are set by the government. The householder will receive a payment for all electricity generated, whether consumed within the home or exported to the Grid. The benefit of consuming the electricity you produce on-site is the avoided costs of electricity you would otherwise have had to purchase from the Grid. The cost of purchasing electricity from the National Grid varies from supplier to supplier but a current average is around 13 pence per kilowatt hour. For more information please use the link on our Homepage.
Each utility company is able to choose how it wishes to organise its billing and generation (FiT or cash back) and Export Tariff arrangements. For example, one utility company will deduct the amount from the amount owed on the electric bill, whilst others may bill as normal and provide a personal cheque for what they owe the householder in quarterly or six-monthly intervals. It is best to check with the utility company that you obtain your feed in tariff from, and obtain their policies in writing.
Whenever your panels are producing more electricity than your home is using, it will exported back to the National Grid. As long as you have an arrangement with your energy company, you will be paid for this electricity so you can be sure that your energy bills will be lower and none of your clean, green electricity will be wasted. You can speak to your electricity provider for details or visit www.uswitch.com to check which energy companies offer arrangements like this. Please note that under the new Feed-in Tariff all exported electricity will be paid at an agreed set rate irrespective of the energy supplier who purchases that electricity. This is in addition to the tariff for the total amount generated by the solar electricity system.
The installed costs of a solar electricity system will depend on a number of factors, especially the size of the system installed and the type of panel used. It should also be noted that most installations will require scaffolding to access the roof. With fuel costs certain to rise over its lifetime, a solar electricity system can be seen as an economic investment as well as an environmental one. Please note that prices will vary from property to property and a more exact quote can be provided for any specific dwelling once a full assessment has been carried out.
No, previously you could access a grant from the Low Carbon Buildings Programme, but the government has now stopped this and introduced the new Feed-in Tariff which offers longer term benefits.
Most domestic properties do not require planning permission. However, there are some exceptions to this if the property is a listed building or is situated in a National Park, an Area of Outstanding Natural Beauty or in a conservation area. In all cases you will need to contact the planning department of your local authority for clarification.
Each kWp requires an area of approximately 8 metres².
Shading is critical and even minor shading can result in a significant loss of energy being produced by the solar array, so it is best to avoid shading wherever possible, especially from any trees or buildings to the south of the array. This is because the cell with the lowest illumination determines the operating current of the series string in which it is connected and shading to even just one cell can reduce the power output to 50% of its full available value. This is one of the areas covered in the suitability assessment carried out before any installation, to ensure that the building is suitable for a solar PV installation.
Once a survey has been completed and the householder agrees to proceed, an average domestic installation takes approximately 1-2 days on site to install, depending on the size of the installation.
Most solar electricity system panels have a manufacturer’s warranty of 25 years with an expected lifetime of up to 40 years. It is estimated that the performance of the electricity system will decrease by less than 1% per year, with the manufacturers guarantee that the electricity system will still perform at 80% of its installed efficiency 20 years after installation. Inverters are generally guaranteed for at least 5 years, although this is extendable, and workmanship is guaranteed for 2 years.
Solar electricity systems are silent in operation, have no moving parts and require very little maintenance. However, during the lifetime of the system, the inverter (which converts the DC electricity produced to AC electricity) may need to be replaced.
In most cases solar electricity systems for homes are entirely grid connected. If there is a power cut the solar electricity system is automatically switched off as 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.
The PV system will have instructions on how to turn it on again if this is necessary.
If your demand for electricity should increase in future years a solar electricity system can be expanded with the inclusion of additional panels although some other components of the original system may also need to be upgraded.
The systems currently being installed will not be sufficient to provide space heating on their own. There is five times more energy from the sun in the warmest months of summer than in the coldest months of winter and the majority of the energy received is during the period April to September so current systems would be insufficient for space heating when required in the winter months.To provide any useful contribution to space heating when it is most required in the winter months a much larger system would be required. However, it may be possible to expand your system in the future to meet the higher demands. A technical assessment would be required to make sure your property is suitable.
Due to the seasons – longer summer days, and shorter winter days – solar electric energy output will vary. However all our calculations take this into account.
Yes, the important thing to bear in mind is that solar power depends on the intensity of radiation, not necessarily direct sunlight, and electricity will still be generated even on cloudy days though at a lesser rate than on days with full sun. The PV system will take in direct sunlight and diffuse (through cloud) sunlight. Even in mid-summer diffuse can actually be greater than direct, so clouds are not an issue.
By installing a solar electricity system you will be producing your own clean electricity, therefore offsetting the production of carbon dioxide from electricity generation using fossil fuels such as gas, oil and coal. The amount of CO2 saved is dependent on the size of the system installed - a typical 2kWp solar electricity system will save almost 1 tonne of carbon dioxide each year (based on the emission factor used by the UK government of 0.43kg of CO2/kWh).
Yes, you can have this arrangement. However it will be usually twice the price and you may need a slightly larger system to deal with the losses.
Yes, as long as the garage roof is suitable, the system can be fitted to the garage in most circumstances.
The Feed-in Tariff rate is set at the time that the solar electricity system is installed and index linked to the property - so it will increase with inflation. Should ownership of the property change hands, the FIT rate that the original system receives will remain the same for the remainder of the 25 years. The rate would only change if the original installed system changed. The current FIT rate, at the time the new system was installed would then apply to the new part of the system. For more information please use the FiT link on our Homepage.
Yes- You need to keep your meter in credit at all times to benefit from the FREE electricity from your solar panels. If your credit runs out then ALL your electricity will go off (including that from your panels) until you top up your credit. When you do the meter will use the FREE electricity first if it is available.