Greenhouse growers should know where their operation sits in their utility’s emergency outage plan and prepare a controlled curtailment strategy before the grid is under strain, according to Ian Knisely, an energy analyst at Energy Bridge Advisors.
Knisely said California utility bills often include a rotating outage group or block that indicates a customer’s place in line when supply falls short. Even where that number is not printed, he said every grower has a position because federal reliability standards, including NERC’s EOP-011, require grid operators nationwide to maintain emergency plans for cutting load.
Those plans can shut off power systematically, sometimes with only minutes of notice. Hospitals and other critical facilities are protected where possible, but Knisely said almost everyone else, including greenhouses, remains at risk. Recent rolling outages have occurred during heat waves and winter storms, he noted, potentially taking down fans, pumps, irrigation, heating and environmental controls at the worst time.
Outage versus curtailment
The distinction, Knisely argued, is control. An outage stops everything at once. A planned curtailment lets the grower decide in advance which loads to drop, by how much and which must stay on to protect the crop.
He described a curtailment plan as a written playbook for hours when the grid is stressed, built around four steps.
- Inventory loads. List major equipment and estimate its power draw, including supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and cold storage.
- Sort by criticality. Some loads can be shut off for a few hours without harm; others can be reduced by dimming lights, staggering fans or adjusting a setpoint a few degrees. Controls, alarms and whatever keeps the most sensitive crop alive must remain on. The ranking depends on crop and growth stage, so it can change during the season.
- Act before the emergency. Outage orders may arrive with little warning, but heat waves and cold snaps are forecast days ahead and grid operators usually issue public alerts. Growers with a plan can treat those signals as triggers: pre-cooling and irrigating early in summer, closing shade curtains before peak demand, or heating ahead of a winter cold peak and testing backup heat.
- Assign and automate. Decide who receives the alert, who decides and who carries out the steps. If an environmental controller can run the sequence automatically, program and test it. Knisely said a plan that hinges on one person answering a phone at 4 p.m. on a Saturday is not a plan.
Once those steps are complete, a grower should know how many kilowatts can be shed, for how long and at what cost to the crop. That figure, Knisely said, is what the grid is willing to pay for.
Demand response as an option
Before ordering outages, utilities and grid operators will pay customers that agree in advance to cut load, because a megawatt that disappears on request is cheaper than one bought at emergency prices, according to Knisely. That market is demand response, and he said it exists in most of the country, largely to help ensure the outage plan never has to be used.
His advice to growers is to ask their utility where their site falls in its plan, then start making their own.