Cutting energy cost in an energy intensive process

Nothing determines a factory array more than when the machines are running. A single day shift, roughly seven until four, tracks the generation curve almost exactly, and a well sized array on that pattern will self consume nearly everything it produces.

A double shift extends into the evening and captures most of the output while adding demand that solar cannot reach after dark. A continuous three shift operation consumes everything an array can make at any hour, but the array covers a much smaller share of a far larger annual total, so the headline percentage looks modest even though every unit is used.

Seasonal and campaign production complicates it further. A plant that runs flat out for four months and idles the rest of the year has to be sized against that reality rather than against an annual average, or the model will flatter itself.

In most sectors the building is the consumer. In manufacturing the building is a rounding error next to the process. Compressed air, motors and drives, extraction, ovens, chillers, injection moulding, welding and heat treatment dominate, and they behave nothing like lighting and ventilation.

Compressed air deserves particular attention, because it is often the largest single electrical load on a site and frequently the least efficient. Leakage, over pressurisation and poor control routinely waste a share of it, and fixing that usually pays back faster than any generating asset.

This is why an energy cost audit alongside the solar feasibility is worth having. If a site can cut consumption cheaply first, the array that follows is smaller, cheaper and better matched, and the combined result beats a large array bolted onto an inefficient process.

Energy intensive sites are usually on high voltage supplies with their own transformers, sometimes with a dedicated substation. That is an advantage, because connecting an array of significant size is a more familiar exercise than on a small low voltage service.

Power quality is the recurring question. Variable speed drives, welding plant and rectifiers create harmonics, and poor power factor attracts charges. Modern inverters comply with the relevant grid connection standards and can support reactive power, but any harmonic sensitive process should be flagged at design so it is assessed properly rather than assumed to be fine.

Spare capacity headroom is worth checking at the same time. Many plants pay for agreed capacity well above their actual peak, or are close to their limit and about to electrify a process. Both change what should be built and in which order.

The unit rate is the visible part and the part an array reduces. It is not the whole bill. Capacity charges, distribution charges banded by time of day, transmission charges linked to peak winter periods and the site's own peak half hour all contribute, and none of them are addressed by generation alone.

A winter evening peak, in particular, occurs when an array is producing nothing. Reducing it requires load scheduling, storage, or simply not running the largest process at the wrong time, and the saving from that can rival the saving from generation.

Any indicative figure we show uses standing assumptions for installed cost and import rate, which are set out on the proposal itself. Those are averages for illustration. A manufacturer buying on a contract with a different structure should expect their real numbers to differ, and the assessment is a starting point for a proper analysis rather than a substitute for one.

Factory roofs vary enormously. Modern portal frame units are simple. Older buildings often have north light saw tooth roofs, multiple bays, heavy roof plant, extraction stacks, and coverings that may contain asbestos cement, which cannot be fixed to.

Structural capacity has to be confirmed for the specific building, particularly where the frame was designed decades ago to a lighter load case. Where headroom is tight, lower ballast and lightweight fixing systems reduce the added load.

Production rarely needs to stop. Roof work happens above the process, and the only shutdown normally required is a short planned outage to make the connection at the main switchboard, which is scheduled around your maintenance calendar. NRG Solar does not install. We assess the site, produce indicative figures and match you with one vetted installer with industrial experience.