Advocates say higher voltage photovoltaic systems have a lower percentage of voltage drop and a lower cost-per-watt due to improved efficiency, reduced use of copper and other factors.
Sean Kenny, CEO of Fresco Solar, says his Morgan Hill, Calif.-based firm has installed over a megawatt-worth of 1,000 V PV systems on rooftops, mostly with standard connectors and tools.
Two rooftop PV installations recently completed components approved for 1,000 V include a 440 kW array on an industrial building in Hayward, Calif., and a 102 kW array on the roof of an office building in San Jose, Calif. The Hayward solar array has over 1,400 ReneSola 300 W panels on the roof and 15 ABB PowerOne Trio inverters. It uses over 15,000 feet of 1,000 V PV wire.
Last year, ABB (as PowerOne) presented a study it commissioned comparing 600 V centralized inverters with an installation using 1,000 V commercial string inverters. The results suggested a 7% reduction in costs using the latter approach.
Kenny says that while there is 1,000 V rated equipment and PV wire, there are not many connector offerings designed specifically for the high-voltage rooftop. Nevertheless, such products would be welcome. In particular, he would very much like to see connectors that were “less fiddly” than industry-standard 4 mm solar connectors. “How about a version that bites the wire and has the contact preloaded?” he says. “Everyone would go for that.”
Opening up
Most of the National Electric Code (NEC) has been developed for voltages up to 600 V because that is the voltage range most commonly used in buildings. NEC Article 690, which specifies electrical requirements for PV systems, says systems rated over 600 V may be installed on any building that is not a single- or two-family dwelling, such as commercial buildings and offices. Thus, 1,000 PV is allowable for rooftops, but the connector products have not yet caught up.
There is no specific prohibition against using 1,000 V for rooftop PV systems. The standard practice has been to use 600 V systems, and the market has responded to this demand.
Installers pioneering the 1,000 V PV rooftop have generally used industry-standard equipment with appropriate voltage ratings. However, manufacturers have not yet marketed their products extensively for installers in this niche.
This is not to say that no connector products have been developed for 1,000 V PV applications. Some applicable commercially available PV connectors are as follows:
- Amphenol Industrial Products manufactures its Helios H4 PV connector that is UL certified to 1,000 V. According to the company, the UL rating allows Helios connectors to be used in existing systems as well as in new ones that require more voltage, without having to increase cable size.
- Automation Series Interconnect (ASI) manufactures its APV4-series of solar connectors rated at 1,000 V according to IEC and TUV specifications and 600 V according to UL. The cable-to-cable connections for solar PV installations are compatible with 4 mm connectors, such as the MC4 and H4 series.
- Multi-Contact’s MC4-EVO 3 PV connector - originally rated for 600 V - has received UL certification for 1,000 V. The connector also meets IEC standards for 1,000 V and 1,500 V.
- Phoenix Contact’s SUNCLIX series of one-piece DC connectors are available in voltages up to 1,100 V and 1,500 V, depending on the model.
- Shoals Technologies Group has received ETL certification to UL9703 standards for its Shoals Interconnect System family of 1,000 V PV harnesses.
Sunny Rai, regional vice president for Renewable Energy at Intertek, points out that in order for PV installers to fully realize the efficiencies of 1,000 V systems allowable under ANSI/UL 1703, component manufacturers must have their products approved and their product certification listings updated.
“The majority of certified PV modules and balance of system components - inverters, combiner boxes, wiring harnesses, connectors, etc. - have been tested and certified for use at a maximum system voltage of 600 volts,” Rai says. “For system installations at 1,000 volts, all components must be listed to 1,000 volts,” Rai says.
Intertek’s Menlo Park, Calif., labs evaluate PV components, including junction boxes, cables and connectors, to verify that they are acceptable for use in 1,000 V systems.
Installers pioneering the 1,000 V PV rooftop have generally used industry-standard equipment with appropriate voltage ratings.
“Higher voltage operation allows the inverters to run at a more efficient operating point, and therefore, more electricity will be generated,” Rai says. “Installation costs are reduced because fewer inverter and combiner boxes are needed, which also reduces maintenance costs.”
Standards certification is not the only factor limiting options on higher-voltage rooftops. California-based solar design and engineering firm Blue Oak Energy points out on its blog that commercial installations may still run into difficulty with the authority having jurisdiction (AHJ) on the installation of rooftop systems over 600 V.
This has been the experience at Fresco Solar. Kenney says his company’s engineers had to involve the local fire departments in their designs. PV systems with 1,000 V are more common for ground-mount installations, where access can be restricted and safety ensured with fences. Such provisions usually are not possible on rooftops.
Nevertheless, AHJs can be satisfied if they are involved and understand what the installers are doing. R
Marketplace: 1,000 V PV Connectors
Installers Looking To Connect On The 1,000 V Rooftop
By Michael Puttré
Lack of demand had held back specific PV connector products, but that could be changing.
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