Does the National Electrical Code (NEC) stand in the way of implementing new technology? In the words of Michael Johnston, chair of the NEC Correlating Committee, “The NEC’s purpose is to ensure the safe but sound implementation of technology.” The Code-making panels and correlating committee do their best to address new technology. Examining various pieces of technology, I believe their track record is impressive.
Solar PV systems
It might appear that photovoltaic (PV) systems were a recent addition to the NEC. However, Article 690 first appeared in the 1984 edition of the NEC. The Ad-hoc Subcommittee on Solar Photovoltaics assembled the proposal that resulted in Article 690. Many of the first systems were small, consisting of a few panels that charged batteries. Many of the pioneers were experimenters who used them to offset their utility bills and some stand-alone applications. Eventually, they became popular to power electronic signs used along roads.
Over time, the systems grew. Certain national retail store chains, including some convenience stores, have incorporated PV into their standard store designs. Some of these installations are designed for net-zero utility demand, and many states have amended regulation to provide consumers with powerful financial incentives to install PV systems in their homes and businesses. Fewer of today’s systems have included traditional storage batteries; however, new energy storage technologies are becoming more popular. Many systems supply power through interactive inverters to the premises, as well as to the utility—a win-win scenario.
Closed-loop and programmed power distribution
Article 780 first appeared in the 1987 edition of the NEC. The system required the installation to use unique receptacles and compatible equipment. In other words, compatible technology had to be built into all equipment used in the smart house. The downside was that it could mean none of a homeowner’s existing appliances and electronic equipment could be brought into a new smart house. Further, since there were limited licensing agreements for use of the technology, there were fewer choices for most appliances.
A few houses were built. However, interest in the technology waned, and Article 780 was deleted from the 2011 Code. “Smart” power technology will become a reality. However, it looks like Article 780 was actually a concept ahead of its time.
Because electric vehicles (EVs) have gained widespread consumer acceptance and availability over the last decade, this might appear to be a new topic. However, EVs first appeared in the 1996 NEC. In fact, a prototype EV—the General Motors Impact—was demonstrated at the NEC panel meetings in San Antonio in December 1994.
Many of the initial batteries in these early EVs were the lead-acid type, which release hydrogen when charging and prompted the inclusion of ventilation tables in Article 625. After this article was written, more exotic batteries were developed, many of which did not produce hydrogen while charging. The development of hybrid vehicles initially slowed the development of pure EVs, but new battery technologies have sparked renewed interest in them. To accommodate new designs, Article 625 has continued to evolve. The Code has developed to recognize wireless power transfer as a means to charge the batteries, and it recognizes EV power export, in which the vehicle can be used as a power source for premises wiring.
Many people first heard the term “fuel cells” during the Apollo 13 mission. However, the first fuel cells date back to 1838. The space program was the first well-publicized practical application. Fuel cells first appeared in the 2002 NEC.
Fuel cells do not generate electricity through mechanical means; they instead use an electrochemical reaction. They differ from batteries in that they require a continuous source of fuel and oxygen. Some use natural gas and biogas through a solid fuel cell. Fuel cells are growing in popularity among high tech firms and were added in the 2017 NEC as a permitted alternative power source for hospital essential electrical systems.
Wind electric systems
Article 694 originally came into the 2011 NEC as “Small Wind Electric Systems,” which were limited to 100 kilowatts (kW) per machine. At the time, I asked a committee member why that was the case. He said it was simply because the original proponents were more familiar with the manufacturers of the smaller wind turbines. There is an economy of scale in wind turbines, so by the next cycle, the size limitation was removed. Newer wind turbines tend to be much larger than the 100-kW machines, and the cost per kilowatt is much lower. Wind farms are springing up everywhere from cities, to rural areas, to offshore locations.
Large-scale PV electric power production facility
The 2017 Code was pivotal for renewable energy. After the publication of the 2014 Code, our attention shifted to a trend of building very large-scale PV installations. Article 690’s existing requirements were primarily geared toward PV systems installation on buildings. Some of these requirements might not be needed for a system consisting of ground-mounted arrays.
The first system we looked at was a 550-megawatt (MW) system in the Sonoran Desert in California. The panels were installed in racks that extended for several miles in each direction. When completed, the installation would consist of 6 million panels. These systems were usually very large scale and limited in size only by the available real estate. Often, they are located on old landfill and other brownfield sites. A new Article 691 was developed to address these large-scale installations. Code-Making Panel 4 decided this new article would apply to systems that were 5,000 kW and larger and not under utility control.
Energy storage systems
PV and wind power systems provide a clean source of renewable energy. The problem is both types rely on the weather. I recall being at a meeting where some U.S. Department of Defense officials mentioned they had a large solar farm on a large military installation. On a hot summer day, clouds over the solar farm caused a reduction in output, which resulted in the utility demand rising and an on-peak demand charge penalty.
To improve the usefulness of PV and wind technology, we need a method of storing the energy. Article 480 on storage batteries has been in the NEC since 1897. However, it was deemed necessary to create a new article to address the more complex subject of energy storage, which is not limited to batteries. With energy storage, the generating capacity of a PV system can be available during nighttime and on cloudy days. The limitation then becomes the storage system capacity. The same is true of a wind-powered system. Its generating capacity can be used when there is no wind and it is limited only by capacity.
Interconnected electric power production sources
This was introduced in the 1987 Code, which was the next cycle after the introduction of PV systems. The use of this article has grown with the increase in the different types of standby and renewable energy sources. In the 2017 Code, microgrids were added to the requirements of Article 705.
Microgrids are defined in 705.2 as “a premises wiring system that has generation, energy storage, and load(s), or any combination thereof, that includes the ability to disconnect from and parallel with the primary source.”
This definition, along with a new Part IV, were timely additions to the Code requirements to recognize the new era of renewable energy systems, which often include a variety of interconnected sources and can include PV and wind along with energy storage. Article 710 was added for stand-alone systems where a microgrid may be arranged to be connected to the grid, with the ability to island from the grid and continue to operate, or where there is no interconnection with the grid at all. Because most PV systems in Article 690 are interconnected with a utility source, this interface is subject to Article 705.
The 2017 Code also saw the introduction of direct current (DC) microgrids that supply DC power, typically from renewable sources. It can be used as DC, or it may supply alternating current (AC) loads via an inverter.
Section 712.2 states, “A direct current microgrid is a power distribution system consisting of more than one interconnected dc power source, supplying dc-dc converter(s), dc load(s), and/or ac load(s) powered by dc-ac inverter(s). A dc microgrid is typically not directly connected to an ac primary source of electricity, but some dc microgrids interconnect via one or more dc-ac bidirectional converters or dc–ac inverters.”
Does the NEC stand in the way?
Looking through the 54 editions of the NEC, one sees the evolution of electrical system and equipment technology over more than 120 years. These new methods and systems have improved the end-user’s experience. From a global standpoint, many of today’s new technologies reduce our carbon footprint, making us better neighbors.
Clearly, the NEC has been responsive to emerging technology. Many of the related Code requirements were written when the technology became commercially viable, and they continue to evolve as the technology matures with application experience. The NEC has always benefited from the lessons learned when these new technologies are put into our homes and businesses. However, as the NEC has evolved to keep pace with advancing technology, it has done so with the safety of the end-user as the primary focus.
Returning to Johnston’s earlier words, “the safe but sound use of technology,” aptly describes the NEC Committee’s prudent approach to developing each Code edition.
About The Author
EARLEY, P.E., is an electrical engineer. Retired from the National Fire Protection Association, he was secretary of the National Electrical Code Committee for 30 years and is president of Alumni Code Consulting Group.