Energy analyst Ian Knisely, who works at Energy Bridge Advisors, writes that greenhouse growers should treat grid reliability as an operational risk rather than only a utility cost. He points to a detail on California utility bills: the rotating outage group or block that shows where a site stands in line if the grid runs short. Federal reliability standards, known as NERC EOP-011, require grid operators nationwide to maintain emergency plans for cutting load. California is unusual in printing that information directly on utility bills.
Utilities across the country keep emergency plans for cutting power when supply cannot meet demand. When such a plan is implemented, power is systematically shut off, often with only minutes of warning. Hospitals and other critical facilities are protected where possible, but almost everyone else, including greenhouses, is at risk. Rolling outages have hit several regions in recent years during heat waves and winter storms.
For a greenhouse, an outage can stop fans, pumps, irrigation, heating and controls at the worst possible time. Knisely draws a distinction between an outage and a curtailment: control. In an outage, everything stops at once. In a planned curtailment, the grower decides in advance which loads drop, by how much, and which stay on to protect the crop.
A written playbook in four steps
Knisely describes a curtailment plan as a written playbook for the hours when the grid is stressed. He outlines four steps.
- Inventory the loads. List major equipment and roughly how much power each piece draws, including supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and cold storage.
- Sort equipment by criticality. Some loads can drop entirely for a few hours without harming the crop. Some can be reduced, such as by dimming lights, staggering fans or adjusting a setpoint a few degrees. Others must stay on, including controls, alarms and whatever keeps the most sensitive crop alive. The sorting depends on the crop and its stage, so it can change through the season.
- Treat forecasts as a trigger. An outage order may arrive with minutes of notice, but heat waves and cold snaps are forecast days ahead, and grid operators usually issue public alerts before an emergency. In summer, growers with a plan can pre-cool in the morning, irrigate early and close shade curtains before the afternoon peak. In winter, they can heat ahead of the cold peak, close thermal curtains early and make sure backup heat is fueled and tested. Either way, the crop enters the hard hours with some margin.
- Assign roles and automate where possible. Decide who receives the alert, who makes the decision and who carries it out. If the environmental controller can run the sequence automatically, program it and test it. Knisely says a plan that depends on one person answering a phone on a weekend afternoon is not a plan.
Once those steps are completed, a grower should know how many kilowatts can be given up, for how long, and at what cost to the crop. That number is what the grid is willing to pay for, according to the article.
Before ordering outages, utilities and grid operators will pay customers who agree in advance to cut load, because a megawatt that disappears on request is cheaper than one bought at emergency prices. That market is demand response. It exists in most of the country, largely so the outage plan never has to be used.
Knisely advises growers to ask their utility where their site falls in its plan, then start making their own. The practical takeaway is to turn forecast signals and equipment priorities into tested actions before an emergency, rather than improvising when power is cut.