Refrigeration demand response
Product-zone probes decide how much thermal headroom there is, the plant's electricity says what shifting it is worth, and the product limit always wins.
- Measure
- Product-zone and mapped temperatures, refrigeration electricity, compressor and defrost state
- Rule
- Cold storage load shifting is bounded by the mapping study, not by the tariff WHO
- Sensors
- TES-22 waterproof probes, ±0.2 °C in the normal range, ±0.5 °C to −40 °C TES-2X datasheet (PDF, opens in a new tab)
- On site
- ZGW-20 Gateway, eligibility, dispatch and the recovery record ZGW-20 datasheet (PDF, opens in a new tab)
Hardware for refrigeration flexibility
The same probes the cold store should already have, the plant's electricity, and a way to ask the refrigeration controller for a change.
The product zone and the warmest mapped point, which bound every event
2 waterproof probes, 2.5 m leads
±0.2 °C from −20 to 70 °C, ±0.5 °C from −40 to 105 °C
The refrigeration board, so a shed can be measured rather than claimed
- Choose the CT rating for the refrigeration board: 120 A split-core, or 300 A, 1 kA and 3 kA Rogowski coils
Class 0.5S to IEC 62053-22 with its CTs
Holds the eligibility rules, the dispatch request and the recovery record
Reads compressor, capacity-stage and defrost state, and writes a setpoint change where the design allows it
Modbus RTU over RS-485, read and write function codes
TES-22 and ZMB-31 share one enclosure with different terminals inside, so the ordering code is what you specify.
What bounds a refrigeration event
Thermal headroom is the difference between where the product is now and where it may not go. Everything else is detail.
| Position | What it tells you | Reference | Sensor |
|---|---|---|---|
| Product zone | How much thermal headroom is left before the product limit | Positions from a documented mapping study WHO | TES-22 (on this page), probe 1 |
| Warmest mapped point | The first place an event will show, which is where the veto comes from | From the same study, under a representative load WHO | TES-22 (on this page), probe 2 |
| Refrigeration electricity | The shed, the shift and the recovery, in the units a programme settles on | One meter on the board that carries the plant ZEM-63 datasheet (PDF, opens in a new tab) | ZEM-65 (on this page) |
| Compressor and defrost state | Whether the plant was already in defrost, or in a state that must not be interrupted | Controller registers, with the model and firmware recorded ZMB-3X datasheet (PDF, opens in a new tab) | ZMB-31 (on this page) |
Air recovers faster than product. Room air comes back within minutes of the plant restarting. The load takes hours, which is why the product zone decides and the air does not.
One test does not transfer. Thermal autonomy measured in an empty room in winter says nothing about a full room in summer with the doors working.
The product limit as a veto in Edge
The site's own rules decide whether a request is accepted. That decision runs on the Gateway, beside the probes it depends on.
- Eligibility from headroom
- A calculated sensor turns the distance between the product temperature and its limit into the minutes of shift that are available.
- The veto is unconditional
- If the product zone reaches its limit, or a probe goes stale, the plant returns to normal control whatever the request said.
- Defrost is never interrupted
- The controller state is a condition on the rule, so a defrost period is excluded from dispatch.
- Reduction and recovery, both measured
- The electrical measurement continues through the event and the recovery, at the interval the programme settles on.
Commissioning checks
Run these with whoever owns the stored product, before any capacity is offered.
-
Retain the mapping study
Confirm the mapping study covers the loading and season the flexibility will be offered in.
Pass when the study exists, matches the conditions, and the permanent probes sit at its points.
-
Prove the veto
Simulate a product-zone temperature above its limit while a request is active.
Pass when the plant returns to normal control immediately, and the record shows why.
-
Prove each controlled state
Exercise every state the dispatch uses, including a controller conflict and a lost connection.
Pass when each one ends in the declared safe state and is written down.
-
Run a supervised drift test
Hold the plant off under supervision and watch the product zone against the eligibility model.
Pass when the measured drift matches the model, or the model is corrected before it is used.
-
Measure a full event and recovery
Record the whole window, including defrost, door activity and production changes.
Pass when the reduction and the rebound are both quantified, with the context that explains them.
What monitoring does not replace
Flexibility is what is left after the product's requirements are met, never before them.
- Demand response does not replace food, pharmaceutical or process temperature compliance and its alarm procedures.
- Room air temperature may not represent the product's core, surface or worst case.
- Thermal autonomy measured in one loading, weather or door-use condition does not transfer to another.
- The refrigeration controller and its protection stay in charge of the plant.
Sources and related guides
Sources
- Temperature mapping of storage areas (opens in a new tab) World Health Organization. Risk-based mapping and what makes a sensor position representative.
- Measurement and verification for demand response (opens in a new tab) US Department of Energy and FERC. Interval baselines and how a programme evaluates a reduction.
- TES-2X Probe Temperature Sensor datasheet (opens in a new tab) EpiSensor. Specifications, ranges and ordering codes.
Related
- Refrigeration and cold store temperature monitoring Application guide Put the permanent probes where a mapping study says the extremes are, alarm on the product zone, and prove the alarm reaches somebody.
- Battery demand response Application guide Measure the connection and the battery separately, read state of charge and limits from the BMS, and record events at the resolution the programme wants.
- Demand-response event energy and rebound worksheet Engineering tool Measure the reduction delivered in a demand response event, any shortfall, and the rebound afterwards.
Reviewed by EpiSensor Engineering on . Revision 4.
Keep the product limit in charge of every event
We will work out the honest headroom, and make the product limit the thing that decides.