As alternative energy shoulders its way into the electrical industry, it increasingly plays by the same rules as the standard electric grid, making installation more straightforward. While photovoltaic (PV) panels, wind power, generators and other distributed systems are largely safe for both users and electricians, misuse is where trouble may occur. Most misapplication of alternative energy takes place on the residential level.
Contractors with a basic understanding of hydrogen, natural gas and distributed system installation will be ahead of those who don’t delve into alternative power sources.
UL 1741.1 (revised in 2005) covers guidelines for power systems that combine independent power sources with inverters, converters, charge controllers and interconnection system equipment (ISE) in system-specific combinations. Used in conjunction with the Standard for Interconnecting Distributed Resources With Electric Power Systems, IEEE 1547, and the Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems, IEEE 1547.1, UL 1741.1 gives contractors a basis for construction of a variety of alternative systems.
The most recent federal budget includes more funding for alternative energy, and states are offering incentives and some mandates for companies, manufacturers, large distribution centers and even residences to draw their power from a variety of sources.
The plethora of choices comes with a variety of players installing all kinds of distributed energy intended to offer reliable or cheaper power. Contractors who work with distributed power sources, especially solar, wind and microturbines, know where their hazards and installation challenges lurk. Here are some of the basics.
Traditionally, the solar power market has been focused merely on PV panels, which come out of the box and begin drawing energy the moment the sun strikes them. An alternative to that traditional method has emerged in recent years; some businesses and homes have begun installing solar building materials—building integrated photovoltaics (BiPVs)—a film or curtain that can go over a wall, window or roof and provide a direct feed of solar power to the facility. Solar electric generation or PVs can be integrated into the weathertight outer skin of a building during construction or renovation. Although this technology is in its infancy, it is getting increasing media coverage and drawing interest from a variety of sources, mostly in the sunny areas of the United States.
Just who installs these systems has not yet been fully decided—roofers, glaziers, electricians or all three. The International Brotherhood of Electrical Workers (IBEW) is vying for that business and, in some cases, providing training for installation. However, Dr. Thomas E. Glavinich, associate professor in the department of Civil, Environmental and Architectural Engineering at the University of Kansas, cautions that contractors would be best served connecting these building materials to the electric system and leaving the installation to someone else.
For one thing, the curtains, if not connected properly, can easily allow water penetration leading to mold growth—a difficult problem the electrical contractor would then have to deal with.
“There’s a lot of risk in getting into the installing,” said Glavinich, who also is a regular contributor to Electrical Contractor. Most of the solar materials will be integrated into glass or roofing, and “that’s not something electrical contractors should get into. If I were an electrical contractor, why would I want to take on that liability?” Instead, he said, builders can install the system and then, “We can come in and connect them.”
However, some contractors are taking on the entire installation, including penetrating roof frames. Vendors are finding ways to make the materials easier to install. Contractors have found crystalline PVs—silicon cells mounted in a rigid frame—to be more accessible.
“I’m always amazed at what some contractors are out there doing,” Glavinich said.
Wind energy is more popular as turbines are getting bigger and more efficient. In addition, at least 20 states have passed laws requiring utilities to generate a percentage of their energy from wind power.
Only a few specializing contractors handle the bulk of commercial or utility wind power installations.
Residential or small-scale wind power is another story. Most commonly found in remote, off-grid locations where conventional methods of supply are expensive or impractical, small wind turbines generate direct current (DC) electricity. Off-grid systems require battery storage and an inverter to convert DC electricity to alternating current (AC).
Residential wind turbines also need a controller to divert power to another useful source, such as space or water heaters when the battery is fully charged.
It is common to combine a system such as this with a diesel generator to provide power during periods of low wind speeds. With a combined wind and diesel system, the user has more flexibility and efficiency than with a diesel-only system. It allows the generator to be used at optimum load for short periods of time to charge batteries when there is little wind, rather than by constant use at varying loads.
Wind systems also can be installed where there is a grid connection. Contractors install an inverter and controller to convert DC electricity to AC at a quality and standard appropriate for the grid. In this way, no battery storage is required. Instead, any unused or excess electricity exports to the grid and the local electricity supply company.
Businesses choose distributed power and generated power solutions for several reasons. The first is the constraints of an area where there may be no power supply. In other cases, manufacturing sites or data centers may need the redundancy in the event of a power failure.
Increasingly, with rolling blackouts and the rising cost of energy, companies are turning to generators such as microturbines—especially for lighting—to reduce their dependence on the grid, both with more reliability and to save money.
Originally derived from aircraft auxiliary power units, today’s microturbines deliver about 30 percent electrical efficiency and, when the exhaust is used for thermal applications, a total fuel efficiency of 80 percent or more. According to Department of Energy (DOE) figures, the average fossil-fueled utility power plant is 33 percent efficient.
Safety issues with a microturbine are no different than with any other electromechanical device found in HVAC or generator set applications. As with any electrical device, contractors should always follow proper lock-out and tag-out procedures when performing any maintenance.
“An important area of focus for safety is gas safety, as the preferred fuel for microturbines is natural gas,” said John Holbrook, senior marketing coordinator, Elliot Energy Systems. “Elliott Microturbines are third-party certified to meet the Gas Appliance Directive 90/396/EEC. This directive is published by the European Union and governs the safety of gas appliances. There is no U.S. standard that is similar.”
“Many countries, including the United States and European Union, have cited microturbines in their energy policies as a technology that can improve the efficient use of fuel and reduce CO2 emissions,” said Holbrook. “The importance given microturbines in achieving energy policy goals has increased interest in all markets but especially in the combined heat and power market.”
The economic projects are based on prime power 24/7/365 operation. According to Holbrook, standby applications are not considered appropriate for microturbines since they take three to four minutes to start and are much more expensive than traditional options.
“That said, microturbines are capable of dual mode operation where, in the case of a blackout, the microturbine will switch from grid parallel to stand-alone mode,” Holbrook said.
“We are also seeing interest in trigeneration where one adds an absorption chiller to the system to provide cooling,” Holbrook said, describing a system known as combined cooling, heating and power (CCHP).
UTC Power, South Windsor, Conn., has made trigeneration capability the selling point of its PureComfort on-site power product.
“On-site power generation alone is not economical unless the waste heat is captured and used,” said John Fox, UTC Power product manager. “Then the system efficiency can increase from about 35 percent to 90 percent.”
Many microturbines come equipped with combined heating and power (CHP) or CCHP, making them considerably more efficient. With CHP, the exhaust from the turbine is used to heat water, for example, and with CCHP, the exhaust is run through a chiller to either heat or cool. In heating mode, said product manager John Fox, the UTP PureComfort generates 140 to 175 degree water, while in cooling mode, it can reduce water temperature to 44 degrees.
Installing microturbines means connecting to a natural gas line as well as to the switchgear. Fox estimated about half of the distributed generation installations are in new construction, with another half as retrofits.
“We rely on Carrier Corp. [a sister division of United Technologies Corp. that makes heating, ventilating, air conditioning and refrigeration equipment] or use local contractors as required for installation,” he said. However, contractors need to know and understand local permitting regulations, which can be different in each region.
Similar to a battery, a fuel cell creates an electrochemical reaction to create electric current. But batteries carry a limited supply of fuel internally, while a fuel cell unit will run as long as it has fuel.
Most microturbines and fuel cells have all safety and operational flexibility built in, but other than the UL 1741 interconnection standard, there is no existing nationwide set of rules and regulations specific to these generators. That may change, as fuel cells are becoming more common.
“Fuel cells are going to be a high-volume product,” Fox said. “In the years ahead, we will see significantly increased interest in on-site power and fuel-cell deployment due to the cost of energy, a desire for a positive environmental footprint and reliable, assured power,” he said.
“Every summer, we’re having rolling blackouts because the grid is overtaxed. With that problem alone, people are starting to pay more attention to sensible options such as distributed generation,” he said.
Inverters all are UL-listed. So if a building loses power, by virtue of an ice storm or any other problem, the output of the inverter shuts down, Glavinich said. For any alternative power, inverter requirements ensure there is nothing back-feeding into the utility.
“If you buy a good UL-listed converter, that’s built in,”
Much of the safety problem is solved by avoiding a leak of energy back into the utility system where electricians or linemen may be working, thinking the power is shut down.
Alternative power is a hot topic these days. Your company may be installing these systems already or may be called on soon to do so. As a growing area of profit for the electrical contractor, getting education in installation methods will prepare you to meet this alternative energy drive. EC
SWEDBERG is a freelance writer based in western Washington. She can be reached at firstname.lastname@example.org.