History on the War of Currents
Thomas Edison and Nikola Tesla were involved in a war known as the War of the Currents that began in the late 1880s. Edison invented direct current, which continuously flows in a single direction, as in a battery or fuel cell. Direct current (abbreviated as DC) was the standard in the United States throughout the early days of electricity. However, there was a snag. It is challenging to convert direct current to higher or lower voltages. Tesla believed that the solution to this problem was alternating current (or AC). A transformer can readily convert alternating electricity to different voltages because it reverses direction a specific number of times per second (60 in the United States). Edison initiated a campaign to denigrate alternating current to protect the royalties he was getting from his direct current patents. He circulated false information about alternating current being more deadly, even going so far as to publicly electrocute stray animals to establish his point (Lantero 2014).
The World’s Fair in Chicago, commonly known as the World’s Columbian Exposition, was held in 1893, during the height of the Civil War. General Electric bid $554,000 to electrify the fair using Tesla’s alternating current for only $399,000. The Niagara Falls Power Company opted to award the contract to generate power from Niagara Falls to Westinghouse, licensed Tesla’s polyphase AC induction motor patent. Although others questioned whether the falls could power the entire city of Buffalo, New York, Tesla was confident that they could power Buffalo and the whole of Eastern United States. The alternating current from Niagara Falls lit up Buffalo on Nov 16, 1986. General Electric had also decided to join the alternating current train (Lantero 2014).
Although it appears that alternating current has nearly decimated direct current, the direct current has seen a resurgence in recent years. Today, our electricity is still primarily alternating current, although computers, LEDs, solar cells, and electric cars all use direct current. And technologies for converting direct current to greater and lower voltages are now accessible. Companies are developing ways to use high voltage direct current (HVDC) to carry electricity over great distances with less electrical loss since the direct current is more stable. As a result, it looks that the War of Currents is far from over. Rather than continuing the intense AC vs. DC struggle, it appears that the two currents will end up functioning in parallel in a hybrid armistice. None of this would have been feasible without Tesla and Edison’s brilliance (Lantero 2014).
1.1 What is AC?
The flow of electric charge that periodically reverses is known as alternating current, or AC. It starts at zero, increases to a maximum, declines to zero, reverses, reaches a maximum in the opposite direction, returns to the original value, and repeats this cycle indefinitely. The period is the time interval between the attainment of a specific value on two consecutive cycles. The frequency is the number of cycles or periods per second. The amplitude of the alternating current is the highest value in either direction. Low frequencies, such as 50 and 60 cycles per second (hertz), are used for domestic and commercial power, but alternating currents of frequencies around 100,000,000 cycles per second (100 megahertz) are used in television and several thousand megahertz in radar and microwave communication. The frequencies used by cellular phones are around 1,000 megahertz (1 gigahertz).
For decades, alternating current (AC) had the unique advantage over direct current (DC; a constant flow of electric charge in one direction). Due to resistance, it could transport power over long distances with minor energy loss. The power communicated is equal to the current multiplied by the voltage, while the power lost equals the resistance multiplied by the current squared (Britannica n.d.).
AC modules are primarily used on rooftops and buildings in Europe. As a result, the cost of repair will be significant. Furthermore, the PV module houses most of the inverters. As a result, it’s critical that the inverters have a lifespan equivalent to that of the PV modules, which can last up to 20 years.
1.2 AC Modules
Unlike traditional photovoltaic systems with a single central inverter, AC modules provide numerous benefits. Each AC module has a microinverter integrated into it. This allows the DC to be converted back to AC. AC modules are particularly appealing for building integration because their independent functioning prevents a PV system’s entire performance from being harmed by the shadowing of a single PV module. These concerns not only safety but also economics, particularly in smaller systems (Jong 1998).
In the early 1990s, research and development on AC module inverters began. The development activities have developed AC module inverters ranging from 100 to 250 Watts. The inverters that are currently available are all mature. Larger projects are being carried out to collect data about inverters in the field. In addition, safety guidelines are being developed to ensure the inverter’s safe operation (Jong 1998).
1.3 Why AC modules?
Traditional photovoltaic (PV) systems have intricate DC cabling, which causes numerous issues. High DC voltage levels have caused considerable problems in grid-connected PV systems with a single central inverter, including fire hazard and prevention, cable losses, DC arc risk.
Most of these issues can be solved with expensive cabling and installation technologies; however, such solutions raise system costs. Inverters, switchgear, and cables must all be chosen in accordance with the system’s size. This necessitates a unique design for each system and creates a barrier to the system’s expansion (Jong 1998).
1.4 The benefits of AC modules
The most significant benefits of using AC modules are the overall system’s simplicity.
- Each module is self-contained, so if one fails, the remaining AC modules will continue to supply electricity to the grid.
- The system’s high modularity makes it simple to expand.
- Individuals can start their PV plant with a small minimum system size of one AC module, lowering entry barriers.
- Standard AC installation materials are used, lowering installation costs, and simplifying system design.
- Conduction losses are low, and cable costs are low.
- There are no system-wide mismatch losses because each AC module runs at its own Maximum Power Point (MPP).
- String diodes are not required.
- Bypass diodes are not required.
- Because of the compact DC system configuration, lightning-induced surge voltages are low (Jong 1998).
All these characteristics (Jong 1998) make AC modules a viable alternative for integrating solar systems into structures. Especially the independent operation of AC modules prevents a PV system’s entire performance from being harmed by the shadowing of a single PV module.
For photovoltaic junction box integration, a series-connected, low-voltage universal micro inverter architecture is proposed, enabling Universal AC modules with microinverter benefits such as global voltage compatibility, excellent energy harvest, and state-of-the-art power quality at photovoltaic string inverter costs.
1.5 The future of AC modules
The market for AC modules will develop rapidly, especially as more private individuals enter the market. It is predicted that there will be around 50,000 – 100,000 AC modules or even more to be deployed in the future. Customers will sort the wheat from the chaff, and only the best inverters will compete in the market. In addition, potential customers and users of AC modules will have increased expectations, particularly in terms of installation and monitoring. Standard AC cabling assemblies will be designed at a low cost, allowing straightforward system installation. All inverters will have extensive monitoring capabilities. These will become more intelligent, with features such as automatic signaling when AC modules fail. The software will be improved and made more user-friendly, and low-cost monitoring displays with fault indication and diagnostics will eventually replace it (Jong 1998).
1.6 Maxeon 5 AC module
For the Maxeon 5 AC Module, there is an integrated microinverter at every module. If the microinverter (or the related PV module) fails, only that PV module is turned off. The rest of the system continues to function normally – a significant advantage of AC modules. Unlike conventional solar modules like DC panels. The solar array’s output is controlled by a single inverter, creating a design with a single point of failure. Moreover, each Maxeon 5 AC module is self-contained, ensuring that your entire system is more reliable and your rooftop is more productive. The system only performs as well as its weakest panel when using traditional technologies due to shadow or other real-world difficulties, such as tiny particles like leaves (Technologies n.d.)
2.0 What is DC?
DC stands for direct current, an electric charge flow that does not change direction. Batteries, fuel cells, rectifiers, and generators with commutators all produce direct current. Because it was uneconomical to adapt direct current to the high voltages required for long-distance transmission in the late 1880s. It was replaced by an alternating current (AC) for standard commercial electricity. Direct current is now transferred over very long distances, even though it must normally be converted to alternating current for final distribution, thanks to techniques established in the 1960s (Britannica n.d.).
2.1 Why DC solar module?
DC Solar modules are still heavily reliable due to their ease of storing energy into batteries (DC). Why can’t we store AC in batteries? Well, because AC changes polarity up to 50 (when frequency = 50Hz) or 60 (when frequency = 60Hz) times per second, we can’t store it in batteries. As a result, the battery terminals change, i.e., Positive (+ve) becomes Negative (-ve) and vice versa; however, the battery terminals cannot change at the same rate, which is why we can’t store AC in batteries (Technology n.d.).
3.0 Which is best for you?
For customers who only want to install a solar panel, it is recommended that they go with AC solar modules. But, when it comes to installing a solar panel and a battery, opting for an AC solar module is probably not a wise option. The drawbacks of the AC solar module are that they can’t store energy in batteries. This fact might be a huge blow for one, but the benefits of the AC solar module overshadow the DC solar module in terms of labour, maintenance, warranty, and power quality. Although AC solar modules are expensive and cost more due to the integrated micro-inverter, they are easier to install and require less labour.
- Britannica, The Editors of Encyclopaedia. n.d. “Alternating current .” Britannica|Electronics.
- Jong, H.Oldenkamp and I.J de. 1998. “AC modules: past present and future .” Workshop Installing the Solar Solution .
- Lantero, Allison. 2014. “The War of the Currents :AC vs DC Power.” Gov.18 November . Accessed December 20, 2021. https://www.energy.gov/articles/war-currents-ac-vs-dc-power.
- Technologies, SunPower from Maxeon Solar. n.d. SunPower Maxeon 5 AC Modules.Accessed December 20, 2021. https://sunpower.maxeon.com/au/solar-panel-products/ac-modules/maxeon-5-ac-modules.
- Technology, Electrical. n.d. Why Can’t We Store AC in Batteries instead of DC?Accessed December 20, 2021. https://www.electricaltechnology.org/2013/06/why-we-cant-store-ac-in-batteries.html.