Skip to main content

How does direct current power work?

There are two main types of electrical current that flow through your home: Alternating and direct. The vast majority of devices around you are powered by alternating current.

By allowing electrons to ebb and flow through your home’s wires, it’s possible to quickly meet shifting electrical demands. However, once upon a time, direct current was the standard, and it wasn’t until the conclusion of a decade-long feud between Nikola Tesla and Thomas Edison that the world settled on AC.

Related Videos

How does direct current work?

Direct current is fairly straightforward. DC power strictly flows in one direction. That means the electrons get pushed in from the power generator, and keep going forward through the wire until it gets to your device, does its work, then continues through the outlet to complete its circuit.

DC power is typically generated by spinning a wire coil within a magnet. There’s loss of efficiency here due to sparks and heat caused by the friction of certain moving parts. The current of the DC power generated is tied to how quickly that motor is turning, and is kept consistent. Appliances have to be operating at the same current to avoid being overloaded or underpowered. When DC power was a part of the grid, this resulted in multiple overlapping electrical providers each generating certain voltages, compatible only with appropriately-rated appliances. It was a mess.

How does alternating current work?

A graph demonstarting the difference between direct current and alternating current.
Veichi

Alternating current has electrons moving forward and backwards through a wire. This is caused by a change in how power is generated. AC power is typically generated by spinning a magnet inside a wire coil. As the magnet spins, its poles take turns alternately pushing and pulling the electrons in the surrounding coil.

While direct current would look like a single straight line when measuring current over time, alternating current looks more like a sine wave: Climbing, reaching a peak, then dropping and eventually backtracking.  The benefit here is that the intervals between peaks and valleys can be shortened or lengthened in order to change the final current and meet demands. This made transmission of power more flexible than DC, since devices of varying voltages could all benefit.  Power was lost whenever AC power needed to be converted to DC back at home, however.

Where is direct current most useful?

If AC is so great, why bother with DC at all? Even though most of our home devices have erratic enough power demands for AC to be useful, there are a few applications where direct current is more efficient. The big one is charging batteries. Batteries typically have a single high voltage at which they charge and discharge. (Yes, some of the fancier batteries out there have microcontrollers to tweak that, usually used with vaping pens.) When you charge standard AA or AAA batteries, the charger is converting the AC voltage from your wall to DC.

A graph demonstrating the relationship between DC and AC currents in a solar-powered home.
Clean Energy Reviews

As mentioned, there’s a loss of efficiency in these conversions, but if you were able to get power from a direct current source, you would be able to enjoy enhanced electrical efficiency. Solar panels are a fine example. Solar power generates DC, and there is a loss of efficiency in converting that to AC for immediate use. However, pumping DC solar power into a battery maximizes the amount of electricity the can be captured. A solar charge controller in between the two ensures the most efficient transfer given solar’s variable output.

Unfortunately, that battery power will still need to be converted to AC at some point in order to play nice with most of the appliances around the house. Some appliances that have a singular, steady energy draw can reliably tap directly into DC power. Direct current freezers and fridges in particular are popular in off-grid homes since they can avoid a loss of efficiency in the conversion to AC. Some enterprising folks have even been able to design a DC-powered home. Beyond consumer applications, you’ll also see high voltage direct current lines feeding into transformers where they’re converted into AC before going to residential areas.

In the end, direct current gets you closer to the power source with higher efficiency than alternating current, but since our electrical demands tend to change, AC gives us the flexibility we need to switch gears quickly.

Editors' Recommendations

Topics
Self-emptying robot vacuums: Do you really need one?
The iRobot Roomba i3 Plus dirt disposal unit.

Many robot vacuums are smart enough to automatically clean your home, but most lack the ability to empty their dustbins. That means you’ll still be fussing with a dirty robot vacuum -- which sort of defeats the entire purpose. However, if you step up to a premium model like the iRobot Roomba j7+, you’ll benefit from a device that knows how to empty itself when its dustbin is full.

The capability can even be found on some midrange models, but is a self-emptying robot vacuum necessary? Or should you save the extra cash and opt for an entry-level robot that lacks the feature? Here’s a closer look at the benefits and drawbacks associated with self-emptying robot vacuums.
What is a self-emptying system?
As a robot vacuum cleans, it pulls debris into an interior storage system -- usually a relatively small dustbin. Depending on the size of your home and how dirty the floor is, you may have to empty the dustbin every two or three cleaning cycles.

Read more
Arlo extends end-of-life support for legacy cameras and doorbells
Arlo Pro 4 Spotlight Camera casing

It looks like households equipped with older, legacy Arlo products won’t have to rush out and buy new gear after all, as the company has changed course on its end-of-life policy that was revealed last month. Previously, several aging cameras and video doorbells in the Arlo lineup were expected to lose access to seven-day cloud storage, notifications, and future updates -- but after reaching out to its community, the company has decided to extend coverage instead of roll it back.

As products age, it’s standard practice for companies to stop supporting them. The time and resources needed to manage outdated products aren’t insignificant, and newer products that are pegged as their replacement quickly become the new focus. However, there was a bit of backlash when Arlo announced its original plans, as a handful of the devices scheduled to be sunset had been released just over five years ago.

Read more
New Ikea air quality sensor arrives just in time for spring
The Ikea air quality sensor on a stack of books.

Ikea might be best-known as the place to buy affordable furniture, but the company also has a surprisingly robust lineup of smart home products. The newest addition to the Ikea smart home family is the Vindstyrka smart indoor air quality sensor -- a tiny device that measures particulate matter (PM2.5) -- and it's slated to arrive this April.

The upcoming Vindstyrka air quality sensor features a minimalist, rectangular design that offers nothing more than a few buttons and a simple display highlighting PM2.5 levels, temperature, humidity, and total volatile organic compounds (TVOC). The sensor is built to work all on its own, although you’ll get more mileage out of the device by pairing it to the Ikea smartphone app. Doing this will allow you to activate other devices based on the current air quality, including Ikea's own Starkvind air purifier.

Read more