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Solar panels are gaining popularity as people shift to renewable energy. If you have questions about installation, cost, or maintenance, this Solar Panel FAQ blog can help. By the end, you’ll have a better understanding of solar panel technology and its...
Proton Energy Solutions Ltd offer expert solar panel installations in Bromley, South East London & across Kent, London and surrounding areas. For those who care about the future and the environment solar panels are the most energy efficient solution you can utilise. They will cut your carbon footprint, cut your fossil fuel dependence and dramatically cut your energy costs. Take advantage of the suns energy for free and stop releasing CO2 into the atmosphere. You can massively reduce your reliance on the electricity grid to your long-term benefit.
Proton Energy Solutions Ltd only offer high performance solar panels that will give you the highest efficiency and longest life span combined with the lowest degradation of output over their lifespan.
You need to be careful considering efficiency as the most important feature of a solar panel. In fact what matters is real world performance, reliability, history and the warranty on offer.
HOW SOLAR PANELS WORK
They first utilise solar energy that is converted into DC power using the photovoltaic effect.
Light particles produced by the sun are called photons, they are the most basic, fundamental particle of light. It is these photons in natural daylight that are converted by solar panel cells to produce electricity. This small bundle of electromagnetic energy is constantly in motion. A solar panel works by allowing photons to bounce into electrons in the solar panel setting them free from atoms, generating a flow of DC electricity.
The DC power can then be stored in a battery storage system or converted into AC by an Inverter for direct use in your home. A solar panel system that is connected to the grid is known as on grid system. One that is also connected to battery storage is known as a hybrid system. These functions rely on the type of inverter you decide on.
Solar panels are made up of many silicone based photovoltaic cells (PV Cells) and these generate DC electricity directly from sunlight. These are linked together within the panel and are connected to adjacent panels with cables. The amount of electricity generated depends on solar panel efficiency, shading losses, dirt, ambient temperature and the installation orientation. They can still generate electricity during cloudy weather, but this depends on how much light can pass through the clouds.
Solar panel efficiency is a measure of the percentage of sunlight that the panel converts into electricity. The cell types are PERC, IBC and HJT and these can all provide efficiency of over 22% with outputs of over 400W per panel up to 600W depending on the panel size.
The N type silicone cells in all the panels we offer will lose no more than 0.25% of power output per annum over 25 years. They will still produce at least 90% of their output after 25 years.
THE ISSUES THAT MAINLY EFFECT PANEL EFFICIENCY ARE
Irradiance– This varies depending on clouds, latitude, time of year and shading. Slight shading over several cells can have a big impact on that solar panel and on the entire string by say 50%. This is because the elements are connected in series and the shading effect on one panel affects every panel. An add on device such as an optimiser or micro-inverter stops the effect being carried beyond the affected panel. In the UK there is a lot of diffuse light that is bounced off building surfaces and even clouds and this produces useful light for the production of electricity.
Orientation– If you have a large, un-shaded, predominantly south-facing roof space, you are fortunate as this is ideal for solar panels, either for heating water or for generating electricity. A south-west or west-facing roof would also be suitable, though a little less productive. Even a direct North roof produces 55% of the output of a South roof so all orientations are considered in the design of a system.
Temperature– The power rating temperature that solar panels are tested at (STC) is 25C . In sunny weather the internal cell temperature can be 20 to 30C above the ambient air temperature and the output is then reduced by 8 to 15%. The nominal operating cell temperature (NOCT) performance is tested at 45C. In colder weather with good levels of sunlight the PV cell output will increase. HJT cells are the best performing in higher temperatures with IBC close behind.
PERC CELLS
PERC solar cells improve cell efficiency by depositing additional passive coating and laser grooves on traditional cells. LONGi launched its mono-PERC modules in 2016, featuring integrated PERC technology on monocrystalline silicon and low light degradation. Its cell efficiency has increased from 21% to 24.06%.
Bifacial Solar panels
The vast majority of solar panels are monofacial, which means that they only generate energy from the front of the module.
Bifacial solar panels expose both sides of the cells to sunlight, increasing total energy generation. They use either a reflective backsheet or dual panes of glass rather than the opaque backsheet that is used in monofacial solar panels.
Most bifacial solar panels are frameless and are also a little thicker to ensure structural integrity.
Monocrystalline cells are used in bifacial solar panels as they are the most efficient. Combining monocrystalline cells with a clear path for the light to get through on both sides helps to generate more energy.
Bifacial solar panels can generate 30% more energy than monofacial solar panels.
As you would expect, the front of the panels still takes in the most sunlight but the rear is still able to generate anywhere between 5% to 30% of that absorbed by the front.
HALF-CUT MODULE TECHNOLOGY
Higher power & higher reliability: Traditional monocrystalline solar panels usually have 60 to 72 solar cells, so when those cells are cut in half, the number of cells increases. Half-cut panels have 120 to 144 cells and are usually made with PERC technology, which offers higher module efficiency.
Since the solar cells are cut in half, and are thereby reduced in size, they have more cells on the panel than traditional panels do. The panel itself is then split in half so that the top and bottom portions operate as two separate panels – generating energy even if one half is shaded. This means that if your home has some trees that cast shade onto your roof at certain times during the day, your entire solar panel will not be unusable, as it would with a traditional solar panel.
They improve the power output and performance of solar modules because they offer a higher shade tolerance due to their unique wiring system.
The key to half-cut cell design is a different method of “series wiring” for the panel, or the way the solar cells are wired together and pass electricity through a bypass diode within a panel. The bypass diode, indicated by the red line in the images below, carries the electricity that the cells generate to the junction box.
In a traditional panel, when one cell is shaded or faulty and does not process energy, the entire row that is within the series wiring will stop producing power. This knocks out a third of the panel. A half-cut, 6-string solar panel works a bit differently:
If a solar cell in Row 1 is shaded, the cells within that row (and that row only) will stop producing power. Row 4 will continue to produce power, generating more energy than a traditional series wiring because only one-sixth of the panel has stopped producing power, instead of one-third.
You can also see that the panel itself is split in half, so there are 6 total cell groups instead of 3. The bypass diode connects in the middle of the panel, instead of on one side like the traditional wiring above.
What is N-Type Mono?
How are solar cells made, and what is doping?
Silica sand is purified to produce silicon. After purification the silicon crystals can be exposed to minerals such as boron and phosphorous in a process known as doping, and then either melted and formed into bricks for cutting, to produce polycrystalline wafers, or grown into ingots for slicing with a diamond wire into thin monocrystalline wafers.
These wafers are then further treated to turn them into solar panel cells. Solar cells work by introducing a potential difference across the upper and lower layer – one surface has extra electrons while the other has a deficit creating an electrical field, and a fine conductive metal circuit allows electrons to flow between the layers when light photons hit the cell and displace the free electrons. This is what doping the silicon achieves. The wafers, whether sliced from a poly ‘brick’ or a mono ingot, will have a coating of doped silicon applied, which is the opposite to the doping of their base layer. This creates the P-N junction (positive/negative) which gives a solar cell its electric potential.
Positive p-type and Negative n-type
The most widely available kind of solar panels at the moment is based on cells where the main ingot and hence base layer is doped with boron. Boron has one less electron than silicon, which makes the cell’s base positivelycharged (hence P-type). The top layer is negatively charged (after having its coating of n-type silicon layer applied) establishing the potential difference outlined above.
N-type cells use phosphorous, which has one more electron and gives the base layer of the cell a negativecharge (hence N-type). These then have a coating of p-type silicon applied to create the P-N junction but by the reverse means. One thing this means is that the direction of flow of electrons is different for p-type and n-type panels. There are other differences though, that have a bearing on module performance.
Why does n-type lead to more power?
One of the disadvantages to boron doping is that boron reacts with oxygen which is a factor in cells and panels being more susceptible to Light Induced Degradation (LID). LID causes a solar panel to reduce in efficiency as a result of exposure to light – an amount of that degradation is expected and factored into the performance predictions on a panel’s datasheet and warranty. Phosphorous doping does not have this issue, meaning that n-type panels will have far better lifetime performance since they will degrade much less quickly. Output warranties on n-type panels therefore tend to be longer, and less steep in their decline, compared with p-type panels. Obviously, degrading less over their productive lifetime, makes n-type solar panels produce more power during that time overall than a p-type equivalent, even when their rated ‘nameplate’ output is the same. The graph above shows the additional warrantied power production our Jinko n-type solar panels would offer over their lifetime.
So why is p-type the standard?
N-type mono isn’t new – in fact the first solar cell made in 1954 was an n-type cell. P-type cells were found to perform better against radiation exposure though, and were therefore well suited to the use of solar in space – a lot of the early research and development of solar was intended for this application.
From that early point on, scale was in favour of p-type and n-type was reserved for use in premium solar panels. Many of the panels known for their efficiency by the likes of LG, Panasonic, Sunpower and REC use n-type in some form or another. Recently though, the lifetime power benefits of n-type mono and significant manufacturer emphasis on efficiency gains on monocrystalline cells in particular, mean that n-type mono is finding its way into mainstream products at lower cost.
Prices are already comparable to similar outputs in p-type products, and the slight uplift in up front cost is outweighed by more power (and thereby return) overall.
