Utilities across the country maintain emergency plans for cutting power when supply cannot meet demand, but a greenhouse still has a place in the outage order. In the article, energy analyst Ian Knisely of Energy Bridge Advisors writes that growers should prepare their own curtailment plans instead of relying solely on the utility's schedule.
Federal reliability standards, including NERC's EOP-011, require grid operators nationwide to keep emergency plans for shedding load. California is unusual in printing a customer's rotating outage group or block directly on the utility bill. The article notes that every grower occupies a place in that sequence whether or not the number appears on a bill. When the plan is triggered, power can be shut off systematically with only minutes of notice. Hospitals and other critical facilities are protected where possible; most other customers, including greenhouses, are not.
Rolling outages have affected several regions in recent years during heat waves and winter storms. For a greenhouse, the consequence is immediate: fans, pumps, irrigation, heating and environmental controls can go dark at the worst possible time.
Knisely draws a distinction between an outage and a curtailment. In an outage, equipment stops at once. In a planned curtailment, the grower decides in advance which loads to drop, how much to reduce and which systems must remain on to protect the crop.
Four steps to a curtailment playbook
The article describes a curtailment plan as a written playbook for hours when the grid is stressed. It can be organized around four steps.
- Inventory the load. List major equipment and estimate how much power each item draws, including supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and cold storage.
- Rank equipment by crop risk. Some loads can be switched off for a few hours without harm. Others can be reduced by dimming lights, staggering fans or shifting a setpoint a few degrees. Controls, alarms and systems that keep the most sensitive crop alive must stay on. The ranking depends on the crop and its growth stage, so it may change during the season.
- Act before the peak. 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, the article advises pre-cooling in the morning, irrigating early and closing shade curtains before the afternoon peak. In winter, growers can heat ahead of the cold peak, close thermal curtains early and confirm that backup heat is fueled and tested.
- Assign decisions and test automation. Decide who receives the alert, who makes the call and who carries it out. If an environmental controller can run the sequence automatically, program it and test it. A plan that depends on one person answering a phone on a Saturday afternoon is not a plan, according to the article.
After those steps, a grower should know how many kilowatts can be shed, for how long and at what cost to the crop. That figure is also the basis for participating in demand response, a market in which utilities and grid operators pay customers to reduce load on request.
The article explains that such payments exist in most of the country and are intended largely to keep emergency outage plans from being used. A megawatt that disappears on request is cheaper than one bought at emergency prices, so grid operators will pay customers who agree in advance to cut load before ordering outages.
Knisely's closing advice is practical: ask the utility where a site falls in its plan, then start writing a plan for the greenhouse.