Cold stores: cooling on fixed setpoints whatever power costs

Cooling runs on fixed setpoints whatever the power price

What happens. The store is held at a fixed air temperature day and night. The compressors run when the temperature asks for it, in cheap hours and in expensive ones. Meanwhile the goods, the walls and the air hold a lot of cold that could serve as a buffer.

What it costs. Power bought at the highest prices, load peaks that raise the connection charges, and compressors that start and stop more than needed.

Why the usual fix fails. Lowering the setpoint by hand before the expensive hours is a risk for the goods and depends on the person on shift. A fixed night-time schedule ignores weather and filling level. Building a cold buffer tank is a large investment when the store itself is already one.

How a fixed-price remote diagnosis checks it. From temperature logs (air, product where available), compressor runtimes, door openings and your power prices I look at how much the temperature can swing without harming the goods. The fixed-price remote diagnosis tells you whether pre-cooling in cheap hours, within the product limits, is worth the effort.

Background: Economic predictive control

Narrow product temperature bands need stricter evidence

What happens. Pharmaceutical and sensitive products must stay in a narrow temperature band, and customers and inspectors want proof. The probe in the air shows the air. The product inside the pallet follows more slowly.

What it costs. Goods written off after an excursion that may not have reached the product, audit findings, and extra margin in the cooling that costs power.

Why the usual fix fails. More probes document more points and still do not show the core. Setting the air colder gives margin and costs energy. Argument after an alarm rests on opinion.

How a fixed-price remote diagnosis checks it. From air and wall temperatures, door events and trial pallets with probes I look at how the core temperature follows the air. The fixed-price remote diagnosis tells you whether a core temperature computed from air and wall values is good enough as evidence.

Background: Computed measurements

The ammonia plant runs on a fixed suction pressure

What happens. An ammonia refrigeration plant keeps the suction pressure at a fixed value and the condensing pressure at a safe level. Compressors and condensers are controlled separately, and the plant does not seek its best point as outside temperature and load change.

What it costs. More compressor power than needed, condenser fans that run when they do not pay, and a plant that is stable but not efficient.

Why the usual fix fails. Floating pressure rules help in some seasons and cause problems in others. Individual retrofit measures such as drives save at one place and move the load to another. Nobody has time to retune the plant each month.

How a fixed-price remote diagnosis checks it. From pressure, temperature and compressor data across seasons I look at where the plant sits relative to its best operating point. The fixed-price remote diagnosis tells you whether economic control of compressors and condensers together would save power.

Background: Economic predictive control

Power is traded in quarter-hours, plans are still hourly

What happens. The day-ahead power market now trades in quarter-hour products. Many plants still plan their flexible loads by the hour. Within the hour, the load jumps and the quarter-hour prices differ.

What it costs. Savings left unused because an hourly plan averages away the cheap quarter-hours, and deviations inside the hour that have to be balanced at a price.

Why the usual fix fails. A planning tool built for hours cannot simply be run more often. Switching manually at short intervals does not work for shift staff. Contracts and schedules with the energy supplier still use the hourly form.

How a fixed-price remote diagnosis checks it. From load profiles, the flexibility of the store (temperature band, compressor limits) and quarter-hour price series I look at what a quarter-hour schedule would gain against an hourly one. The fixed-price remote diagnosis tells you whether a quarter-hour schedule optimisation is worth it.

Background: Trajectory optimisation and setpoint generation