Inverters are needed to convert Direct Current (DC) to Alternating Current (AC) via transformers, switching, and sine-wave corrections. Most sources of grid power are designed to generate AC, and most household, workshop, and office appliances are designed to be powered by AC.
A solar inverter is designed for the sole purpose of converting solar-generated DC to useable AC to feed into the grid or power AC appliances. Normal inverters are used to convert other sources of DC to usable AC. An Uninterrupted Power Supply is an example of a device converting battery DC to AC.
Inverters are essential to convert power from DC sources into a usable AC format:
- Normal inverters and where they are used
- Solar inverters and when they are used
Let’s look at these two inverter applications and see when to install a normal inverter and when a solar inverter is needed.
What does An Inverter do To Convert DC To AC?
An inverter switches and smooths direct current to a pure sine-wave-shaped alternating current through switching and charge capacitors. The resultant AC output is generated at a fixed switching frequency, and the abrupt switches are smoothed to create gentle polarity transitions.
Imagine having a mechanical switch wired to a battery supplying a direct current of charge flowing through a circuit. If the switch is flipped to alternate the polarity of the direct current, you will effectively be doing the job on an inverter.
The DC will be chopped and flipped at the same frequency the switching is done. Our domestic AC-powered devices require a frequency of 60 switches per second or 60 Hertz (Hz).
Waves and Current
In a purely mechanical switching inverter, the AC output current is shaped like square waves of alternating sections of constant current. This type of AC wave pattern is not very efficient at driving electrical AC appliances as it forces very sudden polarity changeovers.
With charge capacitors, the switching can be dampened, and the wave pattern that results is a pure sine-wave alternating current. The gently rising and falling polarity transfer switching is more conducive to making AC motors and appliances run efficiently.
Inverters can also be used in conjunction with transformers to adjust the output voltage and current to that required by the AC device.
How Did We End Up With AC and DC Powered Devices?
Until recently, the name Thomas Edison was more well-known than Nikola Tesla due to Edison’s light bulb invention.
Tesla proposed the generation and use of AC due to numerous advantages in power transmission, while Edison proposed DC as the better system. Tesla was right, and AC became the dominant generation, transmission, and use format.
It is really sad that Tesla sold his patents to his partner Westinghouse and died almost penniless. Elon Musk has resurrected the Tesla name and has made it the most valuable brand in the automotive industry today with a valuation higher than Ford and GM combined.
The competition between Edison and Tesla made headline news, and they both went to great lengths to prove that they were right and that their proposed power format should be implemented. Edison went as far as electrocuting an Elephant to death to prove that AC was dangerous.
Direct Current Examples
All large-scale power plants were designed to generate AC power transmitted over hundreds of miles via high voltage overhead powerlines. DC power was not forgotten and widespread application in car batteries to power the starter motor.
All devices powered directly by batteries are DC, and batteries take power to an off-grid location to power lights, fridges, and power tools. However, most electrical devices were designed to function with AC, creating the need for inverters.
Emergency backup power is required to keep critical equipment such as computer systems and life support systems functioning in a power outage.
Power inverters were designed to convert battery backup DC to AC in a power disruption.
Why Did Solar Inverters Become Relevant?
As the efficiency of solar power generation rapidly grew as a means of generating clean, renewable energy, we need the solar DC to be converted to AC to power our domestic appliances. We needed Solar Inverters to make our electrical AC systems continue to function.
The advantages that made the world select AC as the dominant power format were still true, but now we had the means of generating all the power to satisfy humanity’s needs but in DC format.
The biggest challenge the power generation industry now faces is finding efficient ways to store the endless solar energy supply. Lead-acid batteries are not very efficient or durable as energy storage solutions, and all the lead could pose a serious health risk to humans and the environment.
Metal Halide battery technology rapidly advanced due to the boom in powering cell phones. The first cell phones were the size and weight of brick but rapidly reduced in size with advancements in battery chemistry.
The battery breakthroughs also led to the development of the electric vehicle and have made the name Tesla ubiquitous.
In as little as twenty years, Tesla EVs have become the market leader in designing, engineering, and manufacturing advanced battery packs and electric vehicles.
Solar power is the clean, renewable energy of the future. To fully utilize the benefit of this endless supply of DC, we will have to invert the power to AC for long-distance transmission.
The solar inverter was a necessary development from the normal inverter and was designed to convert solar-generated DC to a user-friendly AC format exclusively. In grid-tied solar installations, the solar power generated by the solar panels cannot be fed into the power grid directly.
The DC-generated solar power must first pass through a solar inverter to be switched and smoothed into a pure-sine wave AC. This AC will flow via the electricity consumption meter to the grid during the day.
At night AC power is drawn from the grid via the same consumption meter, and the system records the net power usage of the household.
With sufficient solar panels on your roof, you can generate enough power to satisfy your demand and sell the surplus to the utility company.