A cold store's compressors never stop, which makes it an unusually good solar candidate and an unusually demanding one. What the flat base load means for sizing, for battery backup, and for the roof you are mounting on.
Bangladesh has over 400 registered cold storage facilities with a combined capacity of approximately 2.5 to 3 million tonnes, mostly holding potatoes and onions along with other agricultural produce, and the fish, fruit and dairy processing plants add a great deal more. They all share one characteristic that decides the shape of a solar project: the refrigeration compressors run 24 hours a day, 365 days a year, which makes electricity the single largest operating cost after labour. That flat base load is why a cold store is an easier plant to design than a factory, and why the mistakes cost more.
Most industrial rooftop projects in Bangladesh have to reckon with self-consumption: how much of what the roof makes at noon is actually used on site, and how much goes out to the meter at a lower value. A cold store largely removes that question. Compressors, condenser fans and circulation pumps are drawing at eight in the morning and still drawing at four in the afternoon, so almost every unit generated is consumed where it is made, at the full retail tariff you would otherwise pay.
The seasonal alignment helps too. Solar generation peaks in summer, which is exactly when refrigeration loads are highest and grid reliability is under most strain. The consequence for sizing is straightforward: on most cold store sites the constraint that binds first is the roof or the sanctioned load ceiling, not the load profile. Under the Net Metering Guidelines 2025, that ceiling is 100% of sanctioned load, or 80% of transformer capacity for medium-voltage consumers at 11 kV and above.
| Facility type | Capacity | Roof area | Solar plant | Annual saving |
|---|---|---|---|---|
| Small cold store | 500 tonnes | 20,000 sq ft | 260 kWp | BDT 32,76,000 |
| Medium cold store | 2,000 tonnes | 60,000 sq ft | 780 kWp | BDT 98,28,000 |
| Large cold store | 5,000 tonnes | 150,000 sq ft | 1,950 kWp | BDT 2,45,70,000 |
| Fish processing plant | Variable | 80,000 sq ft | 1,040 kWp | BDT 1,31,04,000 |
Those roof areas, typically 50,000 to 200,000 sq ft on a purpose-built store, are what make capacities of this order possible at all. Very few other buildings in Bangladesh offer that much unbroken plane.
For a cold store operator a power cut is not an inconvenience. A long enough outage in the wrong week can destroy an entire season's stored crop, and the loss is measured in the contents of the chambers rather than in kWh. Pairing rooftop solar with battery storage of the kind used on Vvon projects, such as Pylontech or BYD, provides 2 to 4 hours of backup power for the compressors through a grid outage. Solar, battery and grid together give the most resilient supply available to a cold store in this country.
The design question is which compressors sit on the protected bus. Carrying every machine in the plant room through a four-hour outage is a large and expensive battery. Carrying enough refrigeration capacity to hold chamber temperature within its allowable band, with the loading bay and the office deliberately left out, is a much smaller one. Have the plant engineer state the permitted temperature rise and the duration it must be held for before anyone quotes kWh of storage.
Cold store roofs are not ordinary industrial roofs. The deck usually carries an insulated envelope, and every fastener that passes through it is a potential thermal bridge and a path for moisture into the insulation. Condensation inside a panel roof is slow, invisible and expensive, so clamp-based mounting that grips the sheet profile without penetrating is strongly preferred here, more so than on a plain factory shed. Where the structure is a purpose-built store rather than a converted godown, the purlins were often sized for the insulation and sheeting alone, so the structural check is not a formality.