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Why Do Solar Cells Need An Inverter? What You Need to Know!

Photovoltaic Solar Cell

Sometimes referred to as a photovoltaic cell, a solar cell has the ability to convert energy drawn from sunlight into electrical energy. That whole operation is made possible by an effect called the photovoltaic effect.

The photovoltaic effect is not only a chemical effect, but also a physical phenomenon. And it’s both of those things in the sense that it allows for the production of electric current and voltage within a device when light gets absorbed, hence triggering the electron excitation to a superior energy state.

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What type of current does a solar cell generate?

Solar cells have the ability to produce one type of current, and that is Direct Current (DC), which is very different from Alternating Current (AC).

Even though both of them are electrical currents, the former only flows in one direction while the latter switches back and forth at regular cycles. This is why we need an inverter—to convert DC into AC for use with regular household appliances.

How exactly is solar current produced?

The minute the sun’s rays hit the solar cell’s surface, electrons start flowing, and once they do, a current is generated. However, since these electrons keep flowing in one direction, the type of current produced during that whole process is DC. If the cells could also generate alternating current, we wouldn’t need an inverter.

flexible solar cells
Image Credit: LuYago, Shutterstock

What’s the total amount of power that can be generated using solar cells?

Theoretically speaking, we could generate an astronomical amount. To explain this, we would have to stop talking about solar cells for a minute and talk about sunlight in its purest form. According to scientists, on a cloudless day, the amount of raw solar power that hits the Earth’s surfaces is approximately 1000 watts per square meter.

But of course, all that’s based on theoretical assumptions. In practice, after incorporating all the factors including the time of day and planet’s tilt, we get approximately 100 to 250 watts per square meter.

Now, depending on where you are, that equates to about two to six kilowatts per day, and 700 to 2500 kilowatts of pure energy per square meter annually. And this is just an estimate of what to expect in regions that experience warm climates. Those experiencing hotter climates get even more.

Sadly though, solar cells are still not as efficient as we would like. They usually give us about 15% efficiency, meaning the fraction of energy captured at the end of the day is insignificant compared to what’s being supplied.

A single cell will only capture 4–10 watts of pure energy for every square meter and generate 3–4.5 watts of current. That’s why they have to be arranged into large groupings, commonly known as arrays.

An array of 40 cells will be enough to form what we call a solar module, and 4 modules will form a solar panel. A single module is only able to produce 100–300 watts, but multiple panels have the ability to generate enough power to meet your daily household needs.

What’s an inverter?

If you’ve ever come across a device that’s compact and powered by a 12v or 24v battery, chances are you’ve already seen an inverter.

As mentioned earlier on, inverters usually help us convert direct currents into alternating currents. What you might not know is that the conversion process is actually crucial to us, in more than one way.

You see, ironically, even though alternating power systems produce alternating current, they rely on batteries that are only capable of storing direct current.  That means we need inverters to convert that current into a form that’s useful to the systems—our electrical fixtures and household appliances have been designed to operate on AC power.

Types of Inverters

Primarily, we have only two types of inverters:
  • The Modified Sine Wave
  • True Sine Wave

In some circles, you’ll hear people use the Modified Square Wave in reference to the Modified Sine Wave, and the Pure Sine Wave when referring to the True Sine Wave. All you need to know is, they are referring to the same gadgets.

Supposing you’re looking to improve or replicate the power quality supplied through the main gird, we would recommend you go for True Sine Wave. It should also be your go-to inverter if you’re thinking of powering equipment that solely relies on high energy. Equipment such as computers with high processing requirements or microwave ovens.

A Modified Sine Wave inverter will adequately serve a household looking to power ordinary stuff. We’re talking about things like small power tools, kitchen appliances, etc. Unfortunately, it won’t be strong enough to power air-conditioners, laser printers, or any equipment that typically consumes high energy.

Size

There’s a general rule of thumb that often dictates the size of the inverter that’s appropriate for whatever you’re planning to use it for—your solar panel’s direct current rating should NOT be different from that of an inverter.

In other words, if the system that you’ve installed has a 12 kilowatt power rating, your inverter rating should be around 12,000 watts. It’s that simple.

Ratings

With an inverter, you’ll either get:
  • A 30-minute rating
  • A continuous rating
  • Or a surge rating

An inverter with a surge rating will be designated for appliances that draw a high power surge the moment they are switched on, but consume low power while running. The perfect example being the refrigerator.

Continuous rating means the inverter can comfortably support a specific amount of power, without shutting down due to thermal heating. And if that power is too low for the appliance to function effectively, you’ll have to go for the 30-minute rating inverter.

Related Read: 9 Solar Energy Facts, Statistics and Data

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Why are our homes using AC?

Well, to answer this question, we’ll have to go back to the beginning. Far back when Thomas Edison discovered electricity.

After that discovery, firms responsible for the production of electricity quickly realized that they could profit more if they supplied power to every home in the country. This was direct current, by the way, and it was the main form of electricity for close to 20 years.

In 1896, Tesla came along and invented a device that could easily and quickly convert that current into alternating current. A current that, unlike the direct current, could move back and forth. Because efficiency is one of the most important aspects of any operation, Tesla was able to convince homes and businesses to stop relying on direct current and adopt one that was more efficient.

With the AC, you could transfer high voltages without losing too much energy. And that high voltage will give you lower currents, which aren’t affected by the heat generated due to resistance.

Also, working with AC was a lot easier and less dangerous. All these were selling points taken into account back then and that’s how to this day, we’ve relied on alternating current.

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Final thoughts

Today’s society cannot function with one type of current. We need both AC and DC to operate different appliances and run different operations. A solar cell would not be as effective or as valuable as it is now if we didn’t have the inverter to convert the current.

You might also be interested in: 10 Renewable Energy Myths and Misconceptions


Featured Image Credit: Dave Weaver, Shutterstock

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