Tag Archives: photovoltaic

How Do Solar Cells Work?

Power Grid, Solar Energy, , , , , ,
In the last two decades, the contribution of solar energy to the world’s total energy supply has grown significantly. This video will show how a solar cell or photovoltaic cell produces electricity. Energy from the Sun is the most abundant and absolutely freely available energy on planet earth.

In order to utilize this energy, we need help from the second most abundant element on earth sand. The sand has to be converted to 99.999 % pure silicon crystals, to use in solar cells. To achieve this, the sand has to go through a complex purification process as shown.

The raw silicon gets converted into a gaseous silicon compound form. This is then mixed with hydrogen to get highly purified Polycrystalline silicon. These silicon ingots are reshaped and converted into very thin slices called silicon wafers.

The silicon wafer is the heart of a photovoltaic cell. When we analyze the structure of the silicon atoms, you can see they are bonded together. When you are bonded with someone, you lose your freedom.

Similarly, the electrons in the silicon structure also have no freedom of movement. To make the study easier, let’s consider a 2d structure of the silicon crystals. Assume that phosphorus atoms with five valence electrons are injected into it.

Here, one electron is free to move. In this structure. When the electrons get sufficient energy, they will move freely. Let’s try to make a highly simplified solar cell only using this type of material.

When light strikes them, the electrons will gain photon energy and will be free to move.. However, this movement of the electrons is random. It does not result in any current through the load. To make the electron flow unidirectional, a driving force is needed. An easy and practical way to produce the driving force is a PN junction. Let’s see how a PN Junction produces the driving force. Similar to n-type doping, if you inject boron with three valence electrons into pure silicon, there will be one hole for each atom.

This is called p-type doping. If these two kinds of doped materials join together, some electrons from the N side will migrate to the P region and fill the holes available. There. This way, a depletion region is formed where there are no free, electrons and holes.

Due to the electron migration, the N-side boundary becomes slightly positively charged. And the P side becomes negatively charged. An electric field will definitely be formed between these charges.

This electric field produces the necessary driving force. Let’s see it in detail. When the light strikes the PN Junction, something very interesting happens. Light strikes the N region of the PV cell and it penetrates and reaches up to the depletion region. This photon energy is sufficient to generate electron hole pairs in the depletion region. The electric field in the depletion region drives the electrons and holes out of the depletion region.

Here we observe that the concentration of electrons in the N region and holes in the P region become so high that a potential difference will develop between them. As soon as we connect any load between these regions, electrons will start flowing through the load.

The electrons will recombine with the holes in the P region after completing their path.. In this way, a solar cell continuously gives direct current. In a practical solar cell you can see that the top N layer is very thin and heavily doped, whereas the P layer is thick and lightly doped. This is to increase the performance of the cell. Just observe the depletion region formation here. You should note that the thickness of the depletion region is much higher here compared to the previous case.

This means that, due to the light striking the electron hole, pairs are generated in a wider area compared to the previous case. This results in more current generation by the PV cell. The other advantage is that, due to the thin top layer, more light energy can reach the depletion region.

Now, let’s analyze the structure of a solar panel. You can see the solar panel has different layers. One of them is a layer of cells. You will be amazed to see how these PV cells are interconnected. After passing, through the fingers, the electrons get collected in busbars. The top negative side of this cell is connected to the back side of the next cell through copper strips. Here it forms a series connection.

When you connect these series connected cells, parallel to another cell series, you get the solar panel. A single PV cell produces only around 0.5 voltage. The combination of series and parallel connection of the cells increases the current and voltage values to a usable range.

The layer of EVA sheeting on both sides of the cells is to protect them from shocks, vibrations, humidity and dirt. Why are there two different kinds of appearances for the solar panels? This is because of the difference in the internal crystalline lattice structure.

In polycrystalline solar panels, multi crystals are randomly oriented. If the chemical process of silicon crystals is taken one step further, the polycrystalline cells will become monocrystalline cells.

Even though the principles of operation of both are the same. Monocrystalline cells offer higher electrical conductivity. However, monocrystalline cells are costlier and thus not widely used. Even though running costs of PV cells are negligible.

The total global energy contribution of solar voltaic is only 1.3 percent. This is mainly because of the capital costs and the efficiency constraints of solar voltaic panels which do not match conventional energy.

Options. Solar panels on the roofs of homes have the option to store electricity with the help of batteries and solar charge controllers. However, in the case of a solar power plant, the massive amount of storage required is not possible.

So generally, they are connected to the electrical grid system in the same way that other conventional power plant outputs are connected. With the help of power. Inverters DC is converted to AC and fed to the grid.

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Source : Youtube

Basics & Benefits of Going Solar | SCE & Solar Power

Clean Energy, Solar Energy, Solar Equipment, ,
Nowadays, more and more people are going solar and taking advantage of the benefits of a residential solar energy system. A solar energy system will produce much of the energy your home needs which can help to offset how much energy you need to buy from your utility company.

And you’ll reduce your carbon footprint as well which is something else to feel good about. If you manage and monitor your usage, your solar panel system may generate more energy than you need. So, you could earn credits for the surplus energy you export back to the grid.

This part gets a little science-y but all you really need to know is this. Solar panels or solar photovoltaic systems absorb direct sunlight and convert it into electricity. Every panel is made up of solar cells which produce direct current or DC electricity.

That means the electricity flows in a single direction. Your home and appliances run on alternating current or AC electricity, which means electricity currents can flow back and forth in two directions.

So, to put solar energy to work in your home, your system must include an inverter that converts DC electricity to AC electricity. When your solar energy system is not producing enough electricity for your home when it’s say, a really cloudy day or at night, your home grid-tie solar system is still connected to receive electricity from the grid so you’ll have uninterrupted power.

Before you install solar on your Maine home, there are a few things you’ll need to remember. Every solar installation needs to be permitted in advance by your city or county. This is primarily for safety reasons and your contractor can help you with this.

If you’re part of a homeowners’ association, you’ll need to first obtain approval from your HOA. Not all solar panels are alike. Your contractor can help you select a solar technology that’s best for your home.

For more information on solar technology, visit our solar knowledge base. Congrats on your first step to going solar.

Source : Youtube

How do solar panels work?

Power Grid, Solar Energy, Solar Equipment, ,

The Earth intercepts a lot of solar power: 173 thousand terawatts. That’s ten thousand times more power than the planet’s population uses. So is it possible that one day the world could be completely reliant on solar energy? To answer that question, we first need to examine how solar panels convert solar energy to electrical energy.

Solar panels are made up of smaller units called solar cells. The most common solar cells are made from silicon, a semiconductor that is the second most abundant element on Earth. In a solar cell, crystalline silicon is sandwiched between conductive layers.

Each silicon atom is connected to its neighbors by four strong bonds, which keep the electrons in place so no current can flow. Here’s the key: a silicon solar cell uses two different layers of silicon.

An n-type silicon has extra electrons, and p-type silicon has extra spaces for electrons, called holes. Where the two types of silicon meet, electrons can wander across the p/n junction, leaving a positive charge on one side and creating negative charge on the other.

You can think of light as the flow of tiny particles called photons, shooting out from the Sun. When one of these photons strikes the silicon cell with enough energy, it can knock an electron from its bond, leaving a hole.

The negatively charged electron and location of the positively charged hole are now free to move around. But because of the electric field at the p/n junction, they’ll only go one way. The electron is drawn to the n-side, while the hole is drawn to the p-side.

The mobile electrons are collected by thin metal fingers at the top of the cell. From there, they flow through an external circuit, doing electrical work, like powering a lightbulb, before returning through the conductive aluminum sheet on the back.

Each silicon cell only puts out half a volt, but you can string them together in modules to get more power. Twelve photovoltaic cells are enough to charge a cellphone, while it takes many modules to power an entire house.

Electrons are the only moving parts in a solar cell, and they all go back where they came from. There’s nothing to get worn out or used up, so solar cells can last for decades. So what’s stopping us from being completely reliant on solar power? There are political factors at play, not to mention businesses that lobby to maintain the status quo.

But for now, let’s focus on the physical and logistical challenges, and the most obvious of those is that solar energy is unevenly distributed across the planet. Some areas are sunnier than others. It’s also inconsistent.

Less solar energy is available on cloudy days or at night. So a total reliance would require efficient ways to get electricity from sunny spots to cloudy ones, and effective storage of energy. The efficiency of the cell itself is a challenge, too.

If sunlight is reflected instead of absorbed, or if dislodged electrons fall back into a hole before going through the circuit, that photon’s energy is lost. The most efficient solar cell yet still only converts 46% of the available sunlight to electricity, and most commercial systems are currently 15-20% efficient.

In spite of these limitations, it actually would be possible to power the entire world with today’s solar technology. We’d need the funding to build the infrastructure and a good deal of space. Estimates range from tens to hundreds of thousands of square miles, which seems like a lot, but the Sahara Desert alone is over 3 million square miles in area.

Meanwhile, solar cells are getting better, cheaper, and are competing with electricity from the grid. And innovations, like floating solar farms, may change the landscape entirely. Thought experiments aside, there’s the fact that over a billion people don’t have access to a reliable electric grid, especially in developing countries, many of which are sunny.

So in places like that, solar energy is already much cheaper and safer than available alternatives, like kerosene. For say, Finland or Seattle, though, effective solar energy may still be a little way off. Solar panels in Maine, however, are a wise investment.

Source : Youtube