When harnessing the power of the sun, solar cells need to convert that energy to a usable type of electricity. This process is known as inverting; taking one type of energy and changing it to another type.
The simple answer is that solar cells absorb sunlight (energy) and that produces a direct current, known as DC. Electricity in the form of DC is not usable for modern appliances, so it's inverted to the more commonly used AC (alternating current). Typically, this is for solar power to be used inside a home.
Solar cells that are used for DC appliances do not need to be inverted. Since the electricity being used is already DC, it can be used directly with the [DC] appliance. Let's talk more about what the benefits are for having an inverted approach.
The Workflow from Solar Cells to Alternating Current
Step 1: Solar cell absorbs sunlight
Step 2: The sunlight is turned into usable electricity as direct current (DC)
Step 3: Multiple solar cells are combined into solar modules
Step 4: Solar modules are combined to make one solar panel
Step 5: The solar panel is wired with a positive and negative wire
Step 6: Solar panel wires are hooked up to an inverter device
Step 7: Inverter changes the DC from the solar cell to AC
Step 8: Inverter has an AC outlet to plug a compatible device into
Solar cells need an inverter because our modern world relies mostly on AC electricity. Devices like TVs, lamps, and others that have a US two-pronged plug are designed to run on this alternating current.
However, there are still times when DC electricity is needed. A use case for this would be a smartphone. Think about the USB cable your smartphone came with. It contains the cable that plugs into the port of the phone along with a small adapter that plugs into a typical wall outlet.
This adapter actually transforms AC to a lower voltage to be used since a smartphone charger only needs 5V (V = volts).
Why Can't DC Be Used Instead of AC?
The truth is that it can be. What changes in this scenario is what is being powered. For example, if you are at home with AC outlets in every room, the practicality of using solar comes down to bringing the electricity to each one of those outlets.
In this case, it doesn't make sense to run all new wiring around your home just to use the electricity that is generated.
Let's look at a different scenario. Imagine taking a trip somewhere that doesn't have any power at all. You have a portable solar panel that can be used to harness the sunlight while available.
In the case of the trip where no power is available, a battery could be used to store the energy and output to something like a lamp that works on DC power.
Of course, this may be over-simplifying the process. Because solar cells require other accessories to be ready-to-use after being inverted, being more critical of the scenario is helpful.
Efficiency is another factor to consider after the solar is inverted to AC. We'll be covering that a little further in this post.
Can solar work without an inverter?
Yes, this is possible. The two situations presented above will help determine the choice of what type of power to use.
Let's just throw another example in the mix because examples help create visuals.
Using an RV with solar is a great example of how to make solar work without an inverter. Some RVs come with 12-volt appliances and there is no need to invert the power from DC to AC.
If you are a more visual person, take a look at this video: Can 400W Solar Panel Run 120V Power Tools? Find out!
Do you need an inverter to store energy to a battery?
The caveat here is that you will need something called a charge controller between the solar panel and a 12V battery. The controller maintains a consistent voltage from the solar cells.
Since varying amounts of sunlight hit the cells, output can be sporadic, so the charge controller helps steady the flow of electricity.
Once the electricity gets to the battery, it is stored directly with no need for an inverter. The 12V appliance can now be directly wired into the battery for power.
If an inverter is used with a battery, the upside is that now both DC and AC appliances can be run. The AC appliances can be plugged into the inverter and DC appliances directly hooked-up to the battery.
This is a common situation when you might be using both types of power in something like an RV or other vehicle. For example, using a 12V outlet for a USB device and also needing an AC hookup for a portable fridge.
Is a Solar Cell Less Efficient After Being Inverted?
The short answer to this question is yes. The longer answer is -- anytime energy is transferred or converted ( or inverted ) -- there is loss that occurs.
This doesn't necessarily make the solar cell itself less efficient, but what happens is the energy originally obtained from the cell is less efficient by the time it is used.
Efficiency can be an important factor to consider though when understanding how much electricity can be lost. Once the solar panel converts all of its energy, this could lead up to an 20% reduction in actual vs. collected.
That in turn makes a solar cell 80% efficient once everything is all said and done.
However, this does come with convenience in most cases because appliances someone may already own can be plugged in directly to an inverter and used.
Why do solar cells output DC (direct current)?
Common every-day batteries produce DC already, so solar panels are following this pattern. This is the same type of electricity that the batteries produce.
Direct current is more steady than AC and solar cells can output this current without additional electronics to regulate the electricity.
A more technical answer to the question:
Solar panels, in simplest term, are photo sensitive diodes. Since DC power is what is used in diodes, the generated current for solar cells is also in DC.
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Are solar cells also known as photovoltaic cells?
The two terms solar and photovoltaic are sometimes used interchangeably since they both have to do with converting energy from the sun. Photovoltaic is more specific and describes the process of the sunlight actually being converted to electricity.
From a marketing perspective, people usually enjoy shorter phrases over the more correct terminology – i.e. Buy Solar Cells vs. Buy Photovoltaic Cells Today!
How is an Inverter Different Than a Converter?
An inverter and converter both have to do with transformation of electricity and voltage. Here's the main difference between them:
- When converting voltage, AC (110V) is being changed to DC (12V). This is common for RVs.
- An inverter transforms from DC (12V) to AC (110V)
In essence, they both change the voltage, but in opposite directions.
An INverter increases voltage, while the CONverter decreases voltage.
It may help to understand the difference between an inverter and converter when thinking about using a power inverter.
These power inverters are commonly used in a car, hooked up to a cigarette lighter (why is it still called that?) and offering two outlets for light-load needs such as a laptop with an AC outlet.
Summary & Conclusion
There is a need for both DC and AC power in today's society. Cities run on AC while sensitive electronics require a more direct source of power.
Solar cells offer this inverted power approach and will probably continue to match the needs of things like a 12V battery since it's mainstream. However, keep in mind the scenario-based planning when deciding how to best use solar cells in your environment.
From an individual cell all the way up to a full-size solar panel, the inverter process can be beneficial and also less efficient if needing AC power.