Solar Explained
Photovoltaic System
The Sun
The genesis of all our energy sources is the sun.* One thing we have in abundance here in South Africa, is sunlight. It's time to harness this resource to power our lives.
* With the exception of nuclear energy.
Solar Panels
The solar panels directly convert sunlight into electricity - no detours. About 1m x 2m in size, they consist of glass, silicon and an aluminium frame. They last for up to 30 years with a very small degradation.
Direct Current
As the sun doesn't shine by night and the grid goes down regularly, most of our customers choose to include a battery. It stores the surplus energy generated by the panels and releases it, when you need more than the sun provides.
Battery
In electricity, there is either direct current (DC), or alternate current (AC). Solar panels, like batteries, generate electricity as DC, while appliances use AC.
Inverter
The inverter is the heart of the system. It's primary job is the conversion from DC to AC, so that all your devices can be powered by the electricity coming from the panels. Another task for some inverters is the managing of a battery and providing backup energy, when the grid goes down.
Alternating Current
The electricity in the grid and coming from the sockets is alternate current (AC), therefore your devices and appliances are designed to work with AC.
Distribution Board
In the distribution board, we connect the cables coming from the inverter to the main house line, which is connected to the grid. Here we also secure your system via SPDs and breakers.
Grid
The grid connects your house with the neighborhood, as well as with Eskom. During load shedding, the electricity is turned off by the provider. Your system then automatically switches to backup-mode and continues to power your house.
How photovoltaics were discovered
As early as 1839, the French researcher Alexandre Becquerel observed that certain materials conduct electricity when exposed to light. However, the "photoelectric effect" was so weak that it was often doubted and attributed to measurement errors.
It was not until the beginning of the 20th century that Albert Einstein provided a plausible explanation. He received the Nobel Prize in 1921 for his work on light quantum theory. He was able to explain why certain substances, e.g. silicon, change their charging properties under the influence of light.
Finally, in 1954, the first silicon solar cell was produced. It had an efficiency of less than 6 percent. A few years later, the first technical applications followed, e.g. for light meters and space flight.
For a long time, photovoltaics was considered complicated, ineffective and expensive. Today, it is simple, clean, versatile energy that is also the cheapest. It plays a key role in achieving all climate goals.
Albert Einstein
How photovoltaics work
A solar cell consists of a thin layer of silicon that is only 0.3 mm thick. Silicon is pure sand. Four electrons move on the outer electron shell of the atom. Eight are optimal for a solid crystal formation and so the atom shares two electrons each with four neighbouring atoms.
Phosphorus atoms are mixed into the upper, very thin silicon layer. Phosphorus has five electrons on the outer shell, four of which form a bond with the surrounding silicon electrons. The fifth electron remains bond-free. It is called the n-layer (n as in negative) because of the excess electrons that are not bound in the lattice.
In the lower layer, which is a hundred times thicker, it is exactly the opposite. Boron is added there, which only has three electrons on the outer shell. In the solid silicon lattice, however, four electrons would be optimal for stable crystal formation. Since one is missing, it is therefore called the p-layer (p as in positive).
In the border region between boron- and phosphorus-doped material, something remarkable now happens: Excess electrons from the n-layer migrate into the p-layer to the boron atoms. This charges the silicon electrically. As electrons migrate from the top, the layer becomes positive. The lower part, where the electrons migrate, becomes negatively charged.
If the silicon plate is irradiated with light, the rays penetrate through the very thin upper layer into the transition area. There, the electrons that have attached themselves to the boron atoms are blasted out again and pulled upwards by the positive charge of the upper layer. At the same moment, a lack of electrons becomes noticeable at the bottom.
All you have to do now is connect the top and bottom with a conductor and you have a current flow.
The solar cell is a small power station. It is not powered by fossil or nuclear fuels, but solely by the sun's rays. A 15x15 cm cell produces a voltage of 0.5 volts. To increase the voltage, a module has several cells connected in series. In most photovoltaic modules, 60 cells are connected in series to produce a module voltage of around 30V and outputs of around 270Wp up to 400Wp.
Phosphorus-doped silicon lattice
Licence
How a solar cell is built
The bottom of the cell is an aluminium foil that serves as a metal contact. Above this is a layer of silicon, which is usually only 0.3 mm thick and corresponds to the width of a hair. This layer is doped with boron atoms. On top of this is an even thinner layer of silicon, which is doped with phosphorus atoms. This layer is only 1/1000 mm thick.
The blue shimmering anti-reflective layer above it is supposed to protect against environmental influences and light reflections. Above this are the conductive pathways, which must be as thin as possible because light is supposed to penetrate into the cell between them. These "fingers" lead to the metal contact that receives the electrons.
Solar Cell
Source :Solaranlage.de
Why we need an inverter
There is a wide range of PV cells and the research in this area is going strong. Only two types of cells are commonly used in photovoltaic systems, both based on silicon. This is due to their longevity, efficiency and component materials. It is important, that cells aren't made up of any toxic or rare substances, as this would counter their purpose in being an ecological alternative to conventional electricity sources. Mono- and polycrystalline cells differ in appearance and characteristic.
Monomodules have a higher efficiency in low light than polymodules. Therefore, monomodules have a slightly higher output compared to polymodules with the same size.
Visually, the cells differ only slightly. Polymodules tend to look blue, while monomodules look black or dark blue. Monomodules can be recognised by their strongly rounded corners and polycells by their marbled cell structure.
Polycells are a bit cheaper due to the less complicated manufacturing procedure.
The temperature coefficient is lower for polymer modules than for mono modules. This means, that polymodules lose less power than monomodules as module temperatures rise.
The inverter is the heart and the brain of every PV system. Therefore, we only install high quality inverters, that have proven their worth on an international level. Modern inverters carry out an array of tasks:
1. Inverting
Photovoltaic panels produce direct current. Since most electrical devices work with alternating current, the direct current must be converted into standard household 230V/50Hz alternating current (AC).
On top, they make sure, that the system always runs in the right gear to maximize the output power. Partial shading becomes a problem of the past, since some inverters monitor the system on panel level. Today's inverters work very efficiently. They convert 98 percent of the direct current into alternating current. The remaining 2 percent becomes heat, which is why the inverters need temperature management.
2. Battery Management
In addition to conventional inverters, more and more hybrid inverters are being used. A hybrid inverter is the combination of a photovoltaic inverter and a battery inverter and has the advantage that the direct current generated by the solar system can be stored directly in the battery. The energy is only converted into AC when it is drawn from the battery.
This saves space, is much easier to install and also has fewer conversion losses.
3. Backup Power
Load shedding is an issue and it looks like, that won't change any time soon. Modern inverters can power your home, when the grid is down. This works as long as the sun is shining and your battery is charged.
4. Power your Geyser
Nearly every household in South Africa has an electric geyser. This is by far the largest consumer in the house. It only makes sense to power the geyser with PV-generated electricity.
We therefore offer to include a smart geyser controller, that powers your standard heating element, no changes to the geyser required. This controller communicates with the inverter to push excess electricity into the geyser. This maximizes your consumption of self-generated electricity, instead of gifting it into the grid.
5. Charge your car
The future of mobility is electricity. A prerequisite to driving an electric car is the possibility to charge your car at home. We offer smart wall-boxes, that communicate with the inverter to use excess PV-electricity to charge your car.
Sigenergy Inverter with Batteries
Electrical Vehicle Charging
Electric Vehicle Charger
Source: wallbox.com
Let's take a look into the future of mobility here in South Africa. In Europe and North America electric vehicles are becoming as frequent as conventional ICE (Internal Combustion Engine) cars. With rising fuel prices and an increase in vehicle availability, you might consider electric vehicles as an alternative for your next car. The network of publicly accessible charging stations is growing, but you will want to be able to charge your car at home, because that's where it will be standing idle most of the time.
Wall charging stations are the most convenient, fastest and safest way to charge your e-car at home. Your car needs direct current (DC), but alternating current (AC) comes from the distribution network. The current must be converted by your on-board rectifier (AC charging) or by your charging station (DC charging).
"Can't I just plug my e-car into a wall outlet at home?"
The answer: You can, but charging takes a long time and connecting cables can overheat. Therefore, it's not recommended
Charging stations can be configured in two modes:
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Free Charging:
The charger will only use the excess solar energy to charge the car, reducing the electricity cost to zero. -
Fast Charging:
Get the car ready for the next ride in the shortest time possible, irrespective of solar electricity production -
As a company, you could offer your clients as well as your employees the service of charging their cars during working hours.
As a hotel, guest house or lodge, you could attract more guests by advertising the possibility to charge their cars, either during lunch, or over night.
Billing is made simple via an app, that monitors the consumption of each charging session. You will always keep control over who charges their car, by using NFC-cards that unlock the charger.
Batteries. Yes, or No?
Consumption Curve (green) and Generation Curve (Orange)
Electricity storage systems make photovoltaic systems really effective and boost the consumption of self-generated pv-energy.
The figures above show the electricity consumption and generation over one day. Usually, the consumption peaks in the morning, when the geyser is fired and in the evening during meal preparation, washing, etc. The sun however, shines strongest during the daytime when the consumption drops.
Without a battery, all the surplus electricity generated during day time will be fed into the grid. As of yet, many municipalities don't have an feed-in scheme yet. This means, that the system would export electricity to the public without rewarding you.
A battery stores the surplus electricity, so you can use it when you need it, regardless of the sun.
Our aim is to maximize your self-consumption while minimizing the amount of fed-in electricity.
So what about load shedding? A solar system rids you of the necessity of a Diesel generator. As soon as the grid goes down, the system will switch into backup mode. The house is disconnected from the grid to keep electricians safe, that may be maintaining it. The electricity from the panels is used directly in your house as long as the sun is shining. Next, the batteries are used to keep your lights on and your computer running.
This will only work with batteries installed.
It should be said, that backup supply is no given in PV-systems in general.
We exclusively use high quality lithium ion batteries, that are reliable and safe. There is no need for refilling the batteries and there are no toxic fumes released.
In the last decade, electricity storage systems have undergone rapid development. The prices have dropped and are continuing to drop as the quality increases. Research is still going strong in this field. Nonetheless, batteries are still the most expensive part in your system. Therefore it should be said, that systems without batteries may make sense in your individual circumstance. For instance, if you work from home and have your power consumption peak during day time.
We design your system battery-ready, so that you can upgrade at any later point in time.
TLDR (Too long, didn't read)
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Batteries make sense to maximize the consumption of your PV-electricity
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Backup power only works with batteries
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Batteries are expensive and can be added at any later point in time