By Vvon Engineering Team | Published | Updated
Fibre fly mats on glass in a way rain will not clear, and many mill roofs are older than the business case. What to survey, where the inverter room goes, and what a 575 KWp plant asks of a site.
Solar EPC & street lighting RFQ checklist (TXT)
A jute-mill roof can combine settled fibre, corrosion, fragile areas and existing suspended services. Calculate the actual added weight from module, mounting, cable and other equipment schedules, and verify the complete load path. A generic weight per square metre is not a structural assessment.
Vvon's published portfolio includes 575 kWp at Ahad Jute Mills. That capacity is a project reference, not evidence of a particular string design, cleaning result or financial return. The checks below explain what a comparable site should investigate.
Softening, carding, drawing and spinning all throw fine jute fibre into the air. It leaves through ridge ventilators, turbine vents and extraction discharge, and it settles on every horizontal surface within reach, including glass.
Ordinary urban dust is a nuisance that rain mostly deals with. Fibre fly is different in a way that matters to the array. It is filamentous, so it catches on frame edges, clamps and cable ties rather than sliding off, and it mats. Once matted it traps ordinary dust and forms a felt that sits along the lower edge of a tilted module where water runs off. Rain will not clear it. In some conditions rain makes it worse, because a wet mat compacts and then dries into a crust.
The failure mode is not a general loss of yield across the array. It is a strip of shaded cells at the bottom of the affected modules, which forces bypass diodes into conduction and puts heat where the module was not designed to have it. String monitoring shows it as one or two strings drifting below their neighbours. Module-level thermography during an O&M visit finds the specific panels.
Price cleaning access and documented maintenance responsibilities before purchase. A difficult or unfunded maintenance task is more likely to be deferred.
Survey before you quote, and open up a bay to do it. What the drawings say a 1960s shed has and what is actually up there are frequently different things.
Treat suspect fibre-cement, damaged sheet and rooflights as fragile until assessed by competent specialists. Identify possible asbestos before disturbance. Do not drill, sample or walk on suspect material as part of an informal survey; establish a safe access and investigation plan.
On a light sheet roof the load case that usually governs is not the weight of the array. It is wind uplift. Modules on a shed roof form a surface that the wind gets under, and the uplift at edges and corners is far higher than in the middle of the roof. Get the wind speed for the site's zone from the national building code and have a structural engineer check dead load plus uplift together. Where the truss will not take it, an independent structure standing on the columns, or a ground mount alongside the shed, is a legitimate design decision rather than a defeat.
String inverters breathe. They pull air across heatsinks and, on larger units, through filtered intakes. Put them on a wall inside a carding or spinning hall and the fans load up with fibre, the filters block, the unit derates on temperature and then trips, and the plant loses generation on the hottest and sunniest days of the year, which are precisely the days it should be earning most.
Select inverter location and dust control using the manufacturer's temperature, ingress and ventilation requirements. Any filtered or conditioned enclosure needs a heat-loss calculation, service access and a funded maintenance schedule.
Compare DC and AC routes for loss, cost, voltage limits and fire safety. Keeping one side short is not a universal design rule.
Jute dust burns. A rooftop array puts live DC cabling above a building with a real combustible dust load inside it, and DC arcs do not self-extinguish at a zero crossing the way AC arcs do. This is not an argument against the project. It is an argument for the details being right.
Measure demand across production shifts, weekends and stoppages. A multi-shift operation may consume much of its PV generation, but only interval modelling establishes the share.
Two things to insist on before sizing. First, twelve months of bills, not one, because a single month taken in a slack period will undersize the plant and a single month taken at peak will oversize it. Second, an actual load profile logged at the incomer over at least a full working week, so the design is set against a measured curve rather than an average derived from a kWh total.
Use a site-specific monthly generation profile alongside production and cleaning records. Seasonal output depends on local irradiance, temperature, soiling and outages.
At 575 KWp the project stops being a roof job and becomes a small power plant on an existing electrical installation. The questions change accordingly.
Consult the relevant edition and the documents for the exact equipment and site: JinkoSolar: model datasheets, certificates, installation manuals and warranties; IEA PVPS: operation and maintenance in different climates; HSE: planning work around fragile roofs; IEC 62548-1: PV array design requirements.
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