- How do PV panels work?
- How many panels are needed?
- Is my roof suitable for PV panels?
- How much space does a typical PV array take up?
- Why are PV panels rated in Wp and not Watts?
- Do I need to get planning permission?
- What are the main components of a PV system?
- How effective are solar trackers?
- Do PV panels generate electricity when it’s cloudy?
- How long do panels last?
- Is there much maintenance required in maintaining my PV panels?
- Can I install PV panels myself?
- Do the solar panels have to be installed on the roof?
- How long does installation take?
- Which panels should I choose?
- Will solar panels damage my roof?
- What is the payback period for a PV panel (money and energy)?
- How long do wind turbines last?
- Do I need planning permission?
- Do I need an inverter?
- What size turbine do I need to power my house?
- How strong does the wind have to be for my turbine to work?
- Will the turbine cut out at high wind speeds?
- Will it be noisy?
- How strong must the wind be for a turbine to be viable?
- Can I put a wind turbine on my house?
- Do turbines get struck by lightening?
- How much maintenance will be required
- Do turbines kill birds?
- Will the system still generate power during a power cut?
- How much does it cost?
- How much energy does it produce?
- What sort of batteries do I need?
- Who do I sell my surplus electricity to?
- What is the Feed-in-Tariff?
- Do you have to pay tax income generated by the Feed-in-Tariff?
- Is it possible to claim FITs for off-grid renewable energy systems?
- What about my Surplus Energy?
Solar PV systems consist of modular panels made of silicon, which react directly to sunlight by generating an electric current by something called the Photovoltaic Effect. .
Any number of PV panels can be connected depending on the available space, to provide as much electricity output as required.
An un-shaded roof which is south facing will provide the best performance for PV panels. Panels can also be sited on east or west facing roofs and will have a slightly reduced performance. The ideal angle of elevation, in the UK, for a roof facing due south is 30–40° which is close to a lot of UK roofs. Systems facing East of West will lose efficiency but are still viable.
Q. How much space does a typical PV array take up?
A typical 2 kWp array will take up about 16m2 and will provide approximately half the electricity needed to power the average home.
Q. Why are PV panels rated in Wp and not Watts?
The performance of a PV panel is measured in Wp and means Watts peak. It is the amount of power a panel could produce if under perfect conditions.
Q. Do I need to get planning permission?
As PV panels are silent in operation and visually unobtrusive planning permission, in most cases, is not needed. If you live in a listed building or within a conservation area you should check with your local council.
Q. What are the main components of a PV system?
The main components of a grid connect PV system are the array of panels and mounting system, inverter, fuse box, meter and connecting cables.
For ground or flat-roof mounted panels you can buy mounting systems made to provide the optimum angle of elevation. There is also the option of using solar trackers which maximise exposure to the sun by following its path.
Q.How effective are solar trackers?
Solar trackers give 30-40% more power than a fixed array. Output power is not only maximised but is uniform – an advantage for applications such as pumping water. Trackers give substantial benefits in summer whereas benefits in winter are marginal.
Q. Do PV panels generate electricity when it’s cloudy?
On cloudy days, solar panels will still generate electricity but at a reduced rate, the amount of electricity actually generated will depend on the quantity of cloud cover.
Q. How long do panels last?
PV panels can last 40 years. A performance warranty for quality solar panels (eg. REC Alpha) will guarantee up to 92% rated production for up to 25 years. Performance will diminish slightly as the panels age (roughly about 0.25% to 1% per year - depending upon model used).
Q. Is there much maintenance required in maintaining my PV panels?
For a grid tied system where no batteries need to be replaced there is usually little maintenance required, unless there is an equipment failure, as there are no moving parts. It is a good idea to carry out a periodic check to ensure no debris (leaves, dirt etc.) has collected on the panels which will reduce performance.
Q. Can I install PV panels myself?
Not usually. Installation of PV systems involve working with high voltage DC & AC electricity and often working at height so the services of an experienced professional installer should be used.
Wind & Sun can recommend suitable installers. Find out more
Q. Do the solar panels have to be installed on the roof?
Usually the most cost effective installation will be on the roof however if there are issues with shading, it may be worthwhile putting them on a wall, on the ground or on a pole. Your installer can help you review other options.
Q.How long does installation take?
For an average domestic system, the installation process rarely takes more than two days.
Depending on the available space you will need to select panels according to yield (specific to your location), size and cost. It is also very important to consider factors such as strength, potential for debris build up, any performance warranty that might be sold with the panels and the amount of light intensity degradation, specific to each panel. Choose good quality panels that will add to the value of your home by looking good, being installed properly and produce reliably over the long term rather than simply being of lowest cost.
Q. Will solar panels damage my roof?
Solar panels attach to rails which fix onto brackets. These pass under the tiles and fix to the rafters in the roof. This is the only method of mounting solar panels that we advise since it is very secure and provides better load distribution. It will be necessary to remove some of the tiles in order to attach the brackets but your installer will replace these after the bracket has been attached. It may be necessary to make a small groove in the overlaying tile but this depends on the tile shape and size. With slate roofs, a roofing specialist may be required to remove some of the slates and replace them with lead sections moulded around the brackets.
Solar panels can also be integrated into the roof to provide a more aesthetic appearance.
It is advisable that if you are thinking of replacing your roof within the next 10 years that you do it before you install the panels as it would involve extra work removing and reinstalling them if they were installed before you were to undertake the work.
Q. What is the payback period for a PV panel (money and energy)?
Depending on the panel and the electricity yield of your particular site, energy is paid back in around 2-5 years. Money repayment is dependant on many factors as each individual case is unique.
Simple cash payback is not as important as long term value of the energy generated.
Q. How long do wind turbines last?
A well maintained wind turbine will typically last about 20-25 years. Some parts may need replacing during this time. The quality of the turbine makes a big difference due to the extreme conditions it will face over its lifetime.
Q. Do I need planning permission?
Planning permission varies for different areas of the UK. Generally, most planning departments require consent for structures over 4m high. It is advised that you contact your local planning authority before erecting your turbine. Find your local planning authority here by entering your postcode.
Q. Do I need an inverter?
Yes, if you are exporting electricity onto the gird or if you are using AC to power electronic appliances in your home, an inverter will be required to convert the generated direct current (DC) into alternating current (AC).
Even though some wind turbines generate AC current, it is classed as ‘wild’ AC, which means it varies in frequency. In order to be exported to the grid, or to be used on-site, the generated electricity will need to be converted to DC, via a rectifier, then back into AC with a standard frequency of 50Hz (within the UK), via an inverter.
Q. What size turbine do I need to power my house?
The average household uses around 4-5kWh per year. The following figures are useful as a guideline:
- 1.5kW turbine will produce an average 3,942 kWh per year
- 5kW turbine will produce 13,140 kWh per year
- 15kW turbine will produce 39,420 kWh per year*
*(Data from the BWEA website)
In order to find out how much energy your home uses, you can look at your previous energy bills.
Q. How strong does the wind have to be for my turbine to work?
Turbines have a specific ‘cut-in’ wind speed which is the lowest wind speed in which the turbine will produce usable power. This value depends on the turbine manufacturer and model but tends to be around 3-5m/s, since it is generally accepted that there is not much useable power in very low wind speeds.
Q. Will the turbine cut out at high wind speeds?
With big wind turbines, yes, this is a feature designed to avoid serious damage which can occur to the turbine in very high wind speeds. The cut-out speed on most large turbines will usually be around 25 m/s.
Small turbines however are designed so that they still produce power even in very high wind speeds, although the power will effectively be ‘capped’ at a maximum designed output. This is achieved usually by automatic pitching of the blades out of the wind to reduce the surface area, preventing the turbine from rotating too fast and allowing the turbine to continue producing power without stopping.
Q. Will it be noisy?
Turbines make a ‘swishing’ noise caused by the air turbulence around the blades. This noise is minimised through consideration during design and is subsequently usually masked by the sound of other everyday noises but in some cases can be noticeable.
Gear-less turbines minimise noises in the nacelle. Further noise minimisation is achieved by the use of insulation materials within the turbine.
The best way to get an idea of the noise a turbine makes is to stand next to one and experience it for yourself; you may be pleasantly surprised as to how quiet it is.
Q. How strong must the wind be for a turbine to be viable?
Generally the average wind speed on site should be 5m/s and above to make a turbine viable. It is important to consider that wind speed increases dramatically the higher up you get so it is always worth having your tower as high as is practically possible.
Q. Can I put a wind turbine on my house?
There are many problems with putting a wind turbine on a building. In terms of performance, turbines are best sited in open spaces open to the prevailing wind, away from any trees or buildings as these can cause turbulences, lowering performance. For it to be economically viable and to justify the cost of buying and setting up a turbine, it is important that performance is considered to get the best output from your turbine.
Also turbines will deliver constant vibrations to the building and can place additional forces on the building structure that haven’t been accounted for. This may weaken the building structure.
Q. Do turbines get struck by lightning?
Yes this does happen. Lightning looks for the route of least resistance to the ground and a tall metal pole is an ideal such path. To minimise the effects caused by lightening, turbines are fitted with grounding mechanisms. A wise precaution may be to insure the turbine against lightning damage.
Q. How much maintenance will be required?
A yearly check is what is most often required and this can be arranged through the turbine manufacturer. For the small scale turbines sold at Wind and Sun, turbines come with a 2-5 year manufacturer’s warranty (depending on the manufacturer) which will cover any faulty parts for the initial period of the turbine’s lifetime.
Q.Do turbines kill birds?
Experience and careful monitoring by independent experts has proved that birds are unlikely to get damaged by turbines. Birds do occasionally collide with turbines but the number of recorded deaths is small in comparison with other tall man-made structures especially glass buildings and communication towers. It should also be considered that a much more frequent cause of bird deaths is due to a loss of habitat owing to human infringement and environmental despoliation.
Q. Will the system still generate power during a power cut?
Normally with grid-connect systems, if the grid fails to supply electricity then the inverter will shut down the system. This is a safety feature to protect linesmen working on the grid.
Extra equipment together with battery storage can be included to provide back-up power if required.
Q.What about my surplus energy?
For domestic grid-connected systems, you will be eligible to sell any surplus electricity not used and export it to the grid. This is done by claiming a smart export guarantee (SEG) payment from your supplier.
Q. How much does it cost?
Q. How much energy does it produce?
Q. What sort of batteries do I need?
Q. Who do I sell my surplus electricity to?