Meeting your energy needs

Guillaume Braillard from Watlow discusses how to strike a balance between demand flexibility and supply availability when electrifying a process plant.

Questions around electrification are more practical than they once were. For example, one of the first questions asked at the start of an electrification project is whether the local utility grid can handle an increased load. This is not simply a question of power availability, but of balancing power demand and supply.

Will a grid meet a plant’s energy needs?

This question is trickier than it first appears because the amount of power supplied by the grid, and the amount of power demanded by the process in question, fluctuate over time. Issues arise not because the equipment exceeds the grid’s capacity, but because when multiple pieces of equipment run at peak capacity, it passes a threshold at a time when the grid cannot adequately support the demand.

The increasing loads that electrification projects place on the grid have spurred the call for better demand flexibility. On one hand, utility companies can take a much more moderate approach when it comes to adding generation capacity or making expensive upgrades to the grid. On the other hand, facilities reap the benefits of better cost control and more in-depth data analysis.

This win-win scenario assumes that plants are willing to invest in the kind of power control necessary to implement demand flexibility across processes, and throughout the plant as a whole. Specifically, it requires using modern power controllers that have Predictive Load Management (PLM) capabilities across a network.

Advanced power control

PLM is one of the key technologies for demand flexibility in process power control and consists of two main functions, load balancing (or load sharing) and load shedding. Load balancing involves equally distributing power of different loads to obtain an overall power consumption that is as stable and balanced as possible, eliminating instantaneous peaks and as a result ‘smoothing out’ the power consumption curve. Load shedding involves limiting and shifting the overall energy consumption altogether, or within user-defined priorities.

PLM is a feature of many of the SCR power controllers that Watlow manufactures. At the level of a single machine or device, a power controller with PLM can allow an operator to set a power threshold to ensure that the process will never draw power over that threshold. But the true benefit of PLM can be seen when multiple machines are in use and multiple controllers are connected in a network. Then, PLM-equipped controllers can uniformly distribute power loads, ensuring that at any given moment, the overall power is as stable and balanced as possible.

A plant’s process lines

Take for example, a plant that has ten process lines, each of which has a thermal array that draws power. Any individual machine has a power draw limit of 200 kw. However, the plant will receive some hefty charges from the utility company if it exceeds 1,000 kw during its peak period. Without any sort of networking or demand management, in the worst-case scenario, all ten lines could run simultaneously and draw peak power. To be safe, each machine would need to be limited to 100 kw.

Managing demand at the plant level

Alternatively, consider an additional power controller with PLM attached to a network of devices. The controller can set an overall network threshold, which in this case is over 1,000 kw. Now, the individual controllers will synchronise and communicate, providing a level of demand management at the plant level.

Without this kind of network capability, engineers are forced to make very cautious and conservative guesses as to what the peak power demands of each machine is separately, and this can effectively limit what the plant is capable of overall. But with networking, it is possible to measure power supply and demand dynamically, allocating power in the most efficient way possible. This helps to achieve the demand flexibility needed, resolving the issue of whether the grid can sustain electrification without decreasing throughput or creating downtime.

Electrification is not as simple as replacing fossil fuels with electric alternatives. In fact, the electrification of processes and process heating requires a change in power management. The issue is not just about power availability, it’s also about finding a balance between power demands and supply availability to enable a smooth transition.