A greenhouse may have a place in its utility’s emergency outage plan even if the grower has never checked. A guidance article for controlled-environment growers says that place matters when the grid runs short, because fans, pumps, irrigation, heating and environmental controls can go dark with only minutes of warning.
In California, utility bills include a rotating outage group or block that shows where a customer stands in line if the grid cannot meet demand. Federal reliability standards, including NERC’s EOP-011, require grid operators nationwide to maintain emergency plans for cutting load. California is unusual in printing the information directly on the bill, the article says, but the underlying risk is not limited to one state.
Utilities across the country plan for supply shortfalls by systematically shutting off power. Hospitals and other critical facilities are protected where possible; most other customers, including greenhouses, are not. Rotating outages have affected several regions in recent years during heat waves and winter storms. For a greenhouse, the loss can hit ventilation, cooling, irrigation, heating and controls at the worst possible time.
Outage versus curtailment
The difference between an outage and a curtailment is control. In an outage, everything stops at once. In a planned curtailment, the grower decides in advance which loads to drop, how much to reduce and which systems must stay on to protect the crop. The article describes a curtailment plan as a written playbook for hours when the grid is stressed, built around four steps.
- Inventory equipment and loads. List major equipment and roughly how much power each item draws, including supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and cold storage.
- Sort loads by crop risk. 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 by a few degrees. Controls, alarms and systems that keep the most sensitive crop alive may need to stay on. The ranking depends on the crop and its stage, so it can change through the season.
- Act on forecasts before the emergency. 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. In summer, growers with a plan pre-cool in the morning, irrigate early and close shade curtains before the afternoon peak. In winter, they heat ahead of the cold peak, close thermal curtains early and confirm backup heat is fueled and tested.
- Assign roles and automate. Decide who receives the alert, who makes the decision and who carries it out. If an environmental controller can run the sequence automatically, it should be programmed and tested. A plan that depends on one person answering a phone on a Saturday afternoon is not a plan, the article says.
After those steps, 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.
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. That market is demand response. It exists in most of the country, largely so the outage plan never has to be used, according to the article.
The practical next step is to ask the utility where a site falls in its emergency plan, then build a curtailment plan around the crop, equipment and staff available.