Improperly applied PV string harnesses could cause down time, delays and substitute hassles. At their worst, they’ll current dire security dangers. Right here’s what you must know to maximise their efficiency and security.
Pressured by venture economics, many of us attempt to reduce solar energy system prices the place they’ll. Usually ignored, photovoltaic (PV) wiring string harnesses might look like a secure candidate to chop to dimension on the chopping block. However decision-makers don’t notice how dangerous that reduce nook will be: on account of their susceptibility to decay, improperly applied string harnesses may result in malfunctioning methods, expensive repairs and, typically, appreciable hazard.
Listed below are some ideas to remember to maximise string harness security and efficiency. Specifically, it comes right down to the significance of high quality merchandise, correct molding and bonding and rigorous testing.
What makes a superb PV harness?
Relying on an individual’s actual place within the photo voltaic provide chain, the reply could seem a bit murky. Certainly, a lot of the chance of PV string harness failure will be mitigated by understanding the position of the harness and what separates some harnesses from different choices.
First issues first: what’s a PV string harness? In short, the harness gives a conduit to switch direct present (DC) energy from arrays of PV panels to the following stage of energy transmission (a combiner field or inverter). Particularly, they supply environmentally sealed parallel connections between panels and the following stage.
As a part of the DC collector system, string harnesses are constructed from cable and connectors designed for photovoltaic functions, augmented with molded junctions and fuses. Inside a bigger solar energy system, a key efficiency metric of the string harness is minimizing energy loss over the appreciable size of cable. Given their dimension and scale, they typically ship on to websites with out interim warehouses, pre-kitted in containers or shipped on reels.
What makes a superb PV string harness? Reliably molded junctions and fuses, a design lifetime of 40 years, low resistance by way of all joints, and environmental sealing are all options to prioritize.
For system security, prioritize molding and bonding
Like many photo voltaic system elements, string harnesses are uncovered to harsh environments and will be vulnerable to decay. Within the discipline, string harness elements are subjected to UV publicity, temperature biking, chemical biking, humidity and precipitation. These environmental components contribute to materials degradation, together with shrinkage of the cable jacket alongside the size of the harness.
If not prevented or detected, this decay can shrink cables sufficient to go away inner wires uncovered, which might endanger photo voltaic system upkeep personnel or different finish customers, and in the end result in a failure in energy transmission.
Photo voltaic professionals can scale back the susceptibility of harnesses to environmental injury by choosing merchandise with correct molding and bonding, which preserves the protecting sheath across the wires inside. Conversely, they need to keep away from harnesses related with strategies extra weak to environmental components, together with mechanical compression or warmth shrink tubing.
Overmolds with everlasting bonding to cable jackets have superior longevity. PV harnesses that use bonding as an alternative of mechanical sealing eradicate jacket shrinkage and the potential failures from receding cable jackets.
In distinction, PV cables related by way of different sealing strategies can pull out of the junctions, displaying copper strands — a malfunction that endangers personnel and might result in arcing with any tall, dry grass rising close to uncovered wires. Moreover, wicking can simply happen if moisture will get inside an outer mould that isn’t totally bonded to the cable, compromising the efficiency of the fuse or junction.
For long-term sturdiness, look to rigorous testing
To maximise string harness efficiency and security, it is very important choose merchandise which have undergone thorough design and rigorous testing. Given the significance of fabric choice for product longevity, patrons ought to:
1. Select merchandise that choose supplies for top RTI worth
An necessary parameter to think about for fuse holder materials choice is the Relative Thermal Index (RTI). A temperature score for plastic, the RTI assesses the temperature a fabric can safely face up to for prolonged durations of time with out compromising important materials properties.
Supplies with excessive RTI values are particularly necessary for surfaces in direct contact with fuses.
Fuse holders constructed with excessive RTI polymers expertise a lot larger longevity than these surfaced with rubber alone.
2. Search for photo voltaic elements examined to probably the most stringent attainable interpretation of requirements.
Though an RTI normal exists, their writing is open for interpretation, which means {that a} product might carry out in another way — even throughout the pointers — relying on how the take a look at is run. For full confidence in materials sturdiness, photo voltaic part patrons ought to look to merchandise examined by probably the most stringent normal interpretations. In the meantime, scrutinize the rankings offered by third events, which typically take a look at interpretations that fulfill the letter of the usual however not the spirit — with sturdiness penalties.
Sturdy PV harnesses, sturdy photo voltaic methods
Now, regardless of the place you might sit within the photo voltaic business, you recognize a bit bit extra in regards to the significance of PV string harnesses. Whether or not you’re an installer questioning how greatest to navigate your subsequent venture, an EPC contractor sourcing new materials, or a web site host questioning what inquiries to ask operations personnel, keep in mind: in relation to PV string harnesses, prioritize high quality and correct implementation.
