The Future of Powering the World

­For those who have watched the TV series “The Big Bang Theory,” you may recall Sheldon’s character talking about the rivalry between Thomas Edison and Nikola Tesla. Their feud became known as the “War of Currents,” which occurred in the 1880s. Back then, as electricity was emerging as an essential service that needed to be delivered to every building, Edison was an advocate of delivering direct current (DC) for which he owned the patent. Tesla patented the polyphase system of alternating current (AC) and believed AC was the solution to power cities because it could deliver more power over longer distances.

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Figure 1b: Tesla

In 1888, George Westinghouse purchased Nikola Tesla’s patents. Although Thomas Edison continued to promote DC through Edison General Electric Company, it was clear by the mid-1890s that AC had won “The Current Wars.” Eventually, General Electric formed in 1892 as a result of Edison General Electric Company merging with Thomson-Houston Electric Company also focused on AC.

Growing up in the 60s, most of the electrical devices in the home used AC power. This included the refrigerator, washer, dryer, lights, television and radio. However, by the 80s as I left for university, there was already a change occurring. Although some other popular devices such as hair dryers used AC current, the beginning of demand for DC current was emerging. As I began my engineering studies, my school mandated all students to own a computer, which ran on DC current. Since AC was only available, all computers required a conversion from AC to DC to power the unit.

Every time AC is converted to DC current, there is a loss of power. Fast forward to today, many of the devices we rely on run on DC current. It is not only the obvious ones such as laptops, tablets and phones; most devices have an AC to DC conversion because they require DC power. This includes TVs, radios and stereos. Over time, the power loss from AC to DC for each individual device adds up to significant power loss. 

The question becomes how to deliver the most power efficiently to a building with the least amount of power loss? To understand the options, let’s first take a look at the classes of power that are available today.

National Electric Code Classes of Electricity

The National Fire Protection Association (NFPA) in the United States updates and publishes the National Electric Code (NEC) every three years. The NEC is highly regarded as the authoritative standard for electrical safety. Up until recently there were three classes of electricity:

• Class 1 - High voltage circuit up to 600V that must be handled by a certified electrician and run through a protective conduit
• Class 2 - Low voltage circuits capped at 100W, 30V AC or 60V DC no conduit or electrician required
• Class 3 – Greater than 30V and less than 100V capable of causing electrical shock with additional safeguards does not pose a fire hazard typically used in PA and security systems

Power over Ethernet Emerges

In the late 1990’s as IP Phones came onto the market, a new way of providing power through networks was introduced that came to be known as Power over Ethernet (PoE). PoE is a Class 2 power level that runs over Ethernet Cat 5/6/7 cable that does not require an electrician to install nor does it require it to be run through conduit.

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Figure 2: Power over Ethernet

Initially designed to provide DC power to IP phones over the same Ethernet connection that was carrying to voice, the technology was soon adopted by many other technologies such as wireless access points and IP cameras. There are many benefits that PoE offers including:

• International Power Standard– Based on IEEE 802.3 af/at/bt standards delivered through one interface, RJ45 connector
• Reduced Installation Costs- No additional infrastructures such as conduits are required and does not need a licensed electrician to install
• Flexibility and Scalablity- Easily run up to 100 meters of Ethernet cable and rerouted when needed alleviating the need to have a power source nearby
• Remote Power Management - Feature available on many PoE devices providing power, especially those with multiple ports, so power can be turned on and off when required
• Safe Power- Besides being low voltage and only up to 90W, PoE never delivers power unless a request is made from a device and turns off automatically if a fault is detected

A company called PowerDsine first introduced PoE and was acquired by Microchip Technology to form the Power over Ethernet business unit. There are hundreds of devices that can run on PoE and since PoE only delivers the exact amount of power requested, only when requested, it is highly energy efficient which makes it a sustainable technology.

However, PoE does have its limitations. The biggest being the 100-meter network length, which is the longest run of an Ethernet cable under current standards. To deliver beyond 100-meters, for example, to run power throughout an entire building, requires runs of longer than 100-meters. This is where Fault Managed Power comes in.

NEC Class 4 Fault Managed Power and Powering the Future

Recently, the NEC introduced a new class of electricity, Class 4 Fault Managed Power. This new category can carry up to 450V of power safely through continuous fault management.  Although not truly DC power, it is DC like in nature and can be converted to DC with minimal power loss.

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Figure 3:  AC Current delivered over Long Lines

Class 4 power is going to have an impact on how power is delivered, distributed and utilized. Today high-power AC transmission lines continue to be the most efficient method of delivering power to a structure. Some AC can be delivered to the devices that still run on AC; however, most can be converted to Class 4 Fault managed power.  Since Class 4 does not have the 100-meter limitation of PoE, it can be distributed throughout an entire structure. However, most devices are not designed to run on Class 4 power. This is where PoE can come in, since the Class 4 can be easily and efficiently converted to PoE and distributed the last 100-meters, taking advantage of many of the devices that run on PoE today.

Devices are also being redesigned to take advantage of this new infrastructure. One of the first applications of this approach was in the Sinclair Hotel in Fort Worth, Texas. Most of the devices in the hotel rooms can run on PoE including add devices here. Other devices in the rooms such as an iron require more electricity. One solution was to redesign the iron to incorporate battery storage. Since it is not used often, the iron can be placed on a charging station to charge and be ready for use when needed.

Today, there are several vendors working on Class 4 Fault Managed power In addition, the UL has defined the industry’s first Class 4 cabling system UL 1400-2.  Over time more companies will develop innovative solutions and the emerging market will expand.

As the world continues to find more efficient solutions to deliver energy, the combination of Class 4 Fault managed power and the efficiency of PoE will play a key role in how buildings and homes are going to be wired.

Microchip