Solar photovoltaics (PV) are materials that convert light directly into electricity, using no moving parts. It is made out of semiconducting materials, most usually silicon.
The heart of the panel is made of wafers of semiconducting material, usually silicon – 95% of the market for PV is silicon panels. Other compounds such as gallium arsenide and copper indium diselenide are available. Plastic PV is just coming to the market although conversion efficiencies are still low. In future, materials called perovskites look to be a promising low-cost solar conversion technology.
Apart from the solar material itself, modules also contain a glass front surface, an aluminium frame and polymer resins to seal the panel and prevent water getting inside.
The size of a solar system is measured in kWp (kilowatt peak). It is the amount of power produced under standard laboratory test conditions, which broadly equate to bright sunshine. So a 2 kWp system will produce 2 kW of electrical power in bright sunshine. For standard modules of 16% efficiency, each kWp takes up about 6.25m2 of roofspace. More efficient modules are available, and because they convert light more efficiently, they take up less space. 1kWp of high efficiency 20% modules only take up 5m2 of roofspace.
Click here for our thoughts on the most efficient solar panels currently available.
The kWh produced by a solar array depends on the size of the PV array, and the amount of light received (which depends on location and orientation). In terms of location, a solar panel in the UK will produce between 700 kWh (Scotland) to over 1000 kWh (Cornwall) for every kWp of panels installed. We will model the output of your proposed system at the design stage.
Solar PV produces electricity from all light that lands on the surface. The majority of electricity is produced from direct sunshine, but light from the sky (diffuse light) and reflected from the surroundings (albedo) is also important. The former is dependent on orientation, but the others produce electricity at any angle.
Adding all this together, the optimum orientation is facing due south at a pitch of 30 degrees. However, because of the contribution of diffuse light from the sky, there is a very large hotspot of high performance. Roofs between SW to SE, and 10 to 50 degrees will be producing 95% of optimal. East or west facing arrays will also produce about 85% of optimal. So whilst south facing orientations are best, almost any roof will generate substantial amounts of electricity.
Generally, solar panels can be installed on any roof or free terrain with enough space to accommodate them, whilst trying to avoid shady places.
Solar can be installed on virtually all rooftypes – tiles roofs, slate roofs, flat roofs, trapezoidal metal roofs, standing seam roofs, and even integrated with turf roofs.
It is possible to install on other structures as well – we see solar carports, canopies, walkways, louvres, facades and pergolas.
Solar panels can of course also be installed on the ground as well, from back-garden arrays to solar fields.
View our solar case studies to see some of the installations that we have carried out on a variety of different roof types.
Shading can be very detrimental to solar PV performance. First, any shade will reduce the amount of light landing on an array and reduce output. Second, because panels are wired together in a chain (called a string) the performance of that string is only as good as its weakest link. So shade, (eg from a chimney) can affect not just the one panel that is shaded, but the whole string. As designers we use software to estimate the effects of shading for a particular building, and modify the design to minimise shade.
This really depends on how much electricity you use within the home. An average house uses about 3500 kWh of electricity per year, but with energy efficient lighting and appliances it is possible to use half of this (1750 kWh per year.) A typical rooftop array in the UK is 3 kWp in size, and produces about 2500 kWh per year. So yes, it is possible to produce more than you use on an annual basis, and you can be a net exporter of electricity. The caveat here is that generation does not perfectly coincide with demand in the house – PV produces less electricity in winter, and of course none at all at night-time.
We should also point out, that the above is electricity for lights and appliances only -it does not include demand for hot water or space heating (which are typically fuelled by gas in the UK, but not always). Increasingly we are seeing customers wishing to use solar to meet demand from electric vehicles as well, which is an additional electrical load.
The main advantages are that electricity produced is zero carbon, and therefore does not contribute to climate change. The electricity is free once the system has been paid for, and you will be paid a premium for all the electricity you produce called the feed-in tariff. Over the lifetime of the system, the cost of electricity produced is far lower than purchasing from the grid. There is the satisfaction of generating your own electricity, and not being as reliant on your electricity supplier anymore.
If installed correctly in accordance with IET regulations the PV is perfectly safe. The same could be said of any electrical circuit.
Yes, you can. Flexible solar panels are lightweight and versatile, and useful if a portable solution is needed. They can even be found in rolls. However, they are not well suited to most rooftop applications apart from standing seam metal roofs, to which they can be bonded. Flexible panels are most commonly used for portable applications such as caravans, boating and camping.
An entire solar PV system including panels and inverters, will repay the energy needed to manufacture it within 3 years operating in the UK.
The inverter is the brains of the system. It converts the DC electricity produced by the solar panels into AC electricity for use within the building. It also matches the phase of the AC electricity produced to the phase of the grid, ensuring complete compatibility and the ability to export excess back to the wider electricity network.
This is an issue for commercial properties rather than residential, and depends on the mounting system you use on the roof you have. There are roofing manufactures that produce solar PV mounting systems too. If you use a solar PV mounting system produced by the same roof manufacturer then the warranty should not be affected, and there are the cases where your roof warranty get extended for another 25 years to match the warranty of the solar panels.
However if this is not the case, and this happens most of the times you can lose the roof warranty by installing solar panels.
Pigeons nesting under your panels and fouling your property is one of the most frustrating issues faced by solar households. But it has easy solution, and it isn’t to kill them!
Pigeons, as other birds, are always looking for perfect places for nesting. The most preferable places are covered ones, where they can leave the eggs on safe, and the best option is a warm one to avoid freezing during the winter. That’s the reason that under your solar panels, which are orientated to receive all the solar energy which they can, are the perfect place for them.
To prevent this, solar panel manufacturers have designed extra covers to surround your panels, leaving out of under them any kind of bird without disturb the panel function at all.
This is one of the most common questions about PV. If you are investing in solar energy you need to know if we are going to be paying more money to repair them.
Generally PV does not need maintenance during its effective life. Unlike other technologies, solar PV has no moving parts, so there is nothing to wear out or need lubricating. Solar panels are warrantied to work for 25years, and may last even longer than that.
Solar panels have a surface coating on them to help water and dust run away, and they are considered self-cleaning if pitched at greater than 10 degrees.
However, in some locations there is too much dust, plant debris (leaves etc) or bird excrement, so the panels can get dirty. You can clean it with hot water if you want to keep them perfectly clean, but use no abrasives or chemicals, as these will damage the specialist coating.
Click here for more information on solar PV maintenance.
The value of your property is very much down to the opinion of the prospective buyer. However, solar PV will increase the energy performance rating of the property (EPC rating), and we are seeing a correlation between energy performance and house price for properties in the same location – that is to say an efficient home is seen as more desirable.
If you move out of a property that has had solar PV installed at the very least the new owner/occupier will benefit from reduced energy bills which should be seen as a plus. However the quality of the installation is also important. To give yourself the best chance of increasing the value of your property with solar it is important that you look for a reliable installer who will be available in the future to respond to any questions or issues.
Without getting too deep into the quantum physics of semiconductors (though do ask if you are interested!) solar photovoltaic cells consist of a positively charged and a negatively charged layer of silicon. As the sunlight hits the solar cells, it frees the electrons from the negatively charged silicon. The negatively-charged free electrons are attracted to the opposite surface of the cell. Collector wires on the front and back of the cells complete the electrical circuit and allows a flow of electric current, via your appliances!
This will depend on the size of the installation. Typically a residential installation of solar PV will take 1 day to complete, though more complex systems may take longer. This excludes the installation of scaffolding which will typically take 1 day to erect in advance and 1/2 a day to remove for a residential installation.