AC vs DC: What is the difference between Alternating Current and Direct Current

The standard household electricity we use every day is Alternating Current (AC). What many people don't know, however, is that there's also another type of electricity called Direct Current (DC). So, what exactly is the difference between these two types of currents?

In the guide below, we'll delve deeper into the technical difference between AC and DC power and discuss their practical applications and implications.

Tips: The terms direct current and alternating current are often mentioned in connection with solar systems. The solar energy produced is direct current, which must first be converted into alternating current before use or feed-in. This task is usually carried out by inverters.

What is AC Power?

Alternating Current, often referred to as AC, is a form of electrical current characterized by its periodically changing direction and strength of flow. This periodic change is usually due to the alternating positive and negative poles of the voltage source. These regular changes in direction are also known as cycles and are measured as frequency. 

Frequency, expressed in Hertz (Hz), refers to the number of cycles per second. The stipulated frequency for alternating current in Germany, as well as in most other countries, is 50 Hz. In contrast, some regions like the USA operate at 60 Hz. Alternating current is recognizable by its sinusoidal waveform.

Advantages and Disadvantages of Alternating Current

Pros

• Alternating current enables efficient transmission of energy over long distances, as it can be easily transformed to minimize losses.

• This type of current can be produced cost-effectively and household appliances are designed for alternating current.

Cons

• At high voltages, alternating current can be more dangerous as it can cause stronger electric shocks.

• Alternating current may be less efficient for some electronic devices, as many electronic circuits require direct current and therefore need conversion, which can lead to energy losses.

How is Alternating Current Generated?

Alternating current is generated by alternating voltage sources, such as power plants or generators. These sources use mechanical energy, such as steam or water turbines, to rotate a coil of wire within a magnetic field. This rotation induces an alternating flow of electrons in the wire, creating an alternating current.

What is Direct Current (DC)?

Direct current (DC) is the flow of electric charge in only one direction. This type of current is commonly used in electronic devices, such as batteries and solar cells. Unlike alternating current, direct current does not change direction periodically and instead maintains a constant polarity. This consistency in direction and strength makes direct current particularly suitable for applications requiring a stable and uniform power supply. However, there can be pulsating direct current where the current changes strength but not direction.

Advantages and Disadvantages of Direct Current

Pros

• Direct current is more efficient for electronic devices that require a constant and stable power supply, such as computers or phones.

• This type of current is less dangerous at high voltages compared to alternating current.

Cons

• Direct current cannot be easily transformed for long-distance transmission, making it less suitable for large-scale energy distribution.

• Producing direct current can be more expensive than producing alternating current, as it requires additional components such as rectifiers.

How is Direct Current (DC) Generated?

Direct current is commonly produced in everyday life through solar cells or the output of corresponding power storage systems. The distinctive feature of these voltage sources is that their polarity remains constant at all times. When such a direct current source is connected to a circuit, the positive pole attracts the free electrons in the electrical conductor. This results in a constant movement of the charge carriers, which is referred to as direct current.

What is the Difference Between AC and DC Charging for Electric Vehicles?

Electric cars can only be charged with direct current. Therefore, household electricity, which is typically alternating current, must be converted to direct current. This conversion from AC to DC can take place either via the on-board charger in the electric vehicle or directly at the charging station. Depending on the method, this is referred to as AC or DC charging.

Both AC and DC charging have their advantages and disadvantages. On the one hand, DC charging allows for a faster charging process, thus reducing waiting time at the charging station. On the other hand, charging with high voltage and power using DC can cause the battery to age faster. Slower AC charging, in contrast, treats the battery more gently.

When Is Direct Current or Alternating Current Used?

Direct current is primarily used in devices such as computers, mobile phones, and televisions, as these require a constant voltage and current direction. The same applies to batteries, accumulators, solar cells, and electric cars.

In contrast, alternating current functions differently and is, therefore, mainly used in household power supply, lighting, and numerous industrial machines and devices.

Note: Direct current (DC) is primarily used in devices that require a constant voltage, such as batteries and solar energy systems. On the other hand, alternating current (AC) is used for general power supply and is ideal for applications where efficient transmission and transformation of energy are necessary.

Alternating Current & Direct Current in Solar Systems

Solar energy systems, such as photovoltaic panels, produce direct current. This is because sunlight produces a constant flow of electrons in one direction within the solar cells. In order to use this electricity for household appliances or to feed it into the grid, an inverter is needed to convert the DC into AC.

The good thing today is that there is more accesibility to smart inverters that have improved conversion efficiency and can also be used for storing solar power in batteries. This allows for more efficient utilization of solar energy and greater control over household electricity consumption.

How is Direct Current Converted to Alternating Current?

To convert direct current to alternating current, an inverter is used. These devices utilize electronic switches, such as transistors, to periodically change the direction of the direct current. This process creates a pulsating direct current, which is then smoothed by filter networks to produce a sinusoidal alternating current wave. If necessary, a transformer adjusts the voltage to the desired level. All modern inverters are also equipped with intelligent control electronics that monitor and adjust the output frequency and voltage as needed to ensure a stable power supply at all times.

What Type of Current Comes from the Household Socket?

The current that comes from a standard household socket is alternating current, also known as AC or Alternating Current. In Germany and most other European countries, this alternating current has a frequency of 50 or 60 Hertz (Hz). The voltage varies depending on the region, with 230 volts in Europe and 120 volts in North America.

DC vs AC - Frequently Asked Questions

What is AC?

AC stands for alternating current. In this type of current, the flow of electrons periodically changes direction. Alternating current is commonly used in most households and industries.

What is DC?

DC stands for direct current. Unlike alternating current (AC), direct current flows in one direction. Direct current is commonly used in batteries, solar cells, and other electronic devices such as computers or mobile phones.

What is mixed current?

As the name suggests, mixed current combines direct and alternating current. Mixed current occurs when alternating current is converted to direct current by a rectifier. In mixed current, electrons flow continuously in one direction, similar to pure direct current. However, the current strength varies, distinguishing it from conventional direct current. Because of these fluctuating properties, mixed current is often referred to as pulsating direct current.

Conclusion: What is the Difference Between AC and DC Power?

The primary difference between alternating current (AC) and direct current (DC) lies in the direction of electrical flow. In direct current, the current flows continuously in one direction, making it ideal for devices that require a constant voltage, such as batteries, solar panels, and electronic circuits.

In contrast, alternating current periodically changes direction, which makes it particularly efficient for transmission over long distances since it can be easily transformed to minimize losses. AC is the standard in most households and industrial applications, while DC is commonly used in portable devices and specialized applications like computers.

The choice between AC and DC depends on the specific requirements of the application. Each type of current offers its own advantages and disadvantages, which need to be carefully considered.