How Solar Systems Cut Durian Cold Storage Costs

Solar Peaks Align with Durian Harvest Shifts

Durians fall in the morning. Harvest crews in Raub and Bentong finish the orchard by 1pm, and the fruit moves into the dehushing line within four hours. That is why a blast freezer pulls maximum load — screw compressors at 30HP each, ammonia-charged — between 11am and 4pm. The PV production curve of a 480 kWp rooftop array peaks at exactly those same hours. There is no time-of-use mismatch to solve: the energy the panels produce coincides with the energy the refrigeration compressors burn. This is the single reason solar economics work for durian cold storage and not for, say, an overnight bakery proofer.

TNB Tariff Math and NEM 3.0 Banking

The facility sits on TNB’s Tariff B (Low Voltage Commercial): RM0.365/kWh, with a maximum-demand charge of RM28.60 per kVA per month. Under NEM 3.0 — valid through 2025, with a ten-year crediting window — every kilowatt-hour pushed to the grid at noon earns a one-to-one offset against a kilowatt-hour pulled out at 2am for pulldown. Most new exporters assume export rates are discounted. They are not, for C&I connections below 1MW. The net meter simply runs backwards. So the night shift’s cold-room load runs on solar energy banked earlier that afternoon. That is the literal mechanics of how the cost cut happens.

Sizing Blast Freezer vs PV Capacity

A 20-ton pulldown from 15°C to -30°C means moving roughly 1.8 GJ of heat out of the fruit mass. A 60 kW cooling-capacity blast cell with a 22.3kW compressor working 18 hours per day draws about 400 kWh per day. A 480 kWp array in Peninsular Malaysia produces roughly 54,000 kWh per month, using a conservative 1,300 kWh per kWp per year. The array is about 3× the cell’s own running demand. The excess goes up the NEM meter and comes back the same night. Size below 2× the compressor load and the night pulldown stays exposed to full tariff rates. Size above 4× and the exported excess stops producing any bankable credit.

Battery Storage for Overnight Pulldown

An exporter needs the stored fruit at a clean -18°C before the reefer truck arrives at 6am for the Port Klang run. The inverter — in this case a Huawei SUN2000-100KTL hybrid coupled to a Luna2000-215 battery bank — must absorb the compressor’s inrush without tripping. A screw compressor draws roughly 6× full-load amps on a direct-on-line start; without a soft starter or battery buffer, the inverter disconnects and the chamber starts defrosting. Many Pahang operators use the 215 kWh battery as a reactive-power compensator too, keeping displacement power factor above 0.85 and avoiding the TNB surcharge that drags down the whole monthly bill when induction motors sag below it.

Pahang Business Case: RM0.42 to RM0.25/kg

A 480 kWp ground-mount array at a durian processing shed near Chenor, Pahang, runs about RM1.95/Wp installed — RM936,000 turnkey. It generates 54,000 kWh/month, displacing RM19,710 of TNB purchases at the RM0.365 tariff. The facility’s previous total TNB bill was RM50,000/month (packhouse, sorting line, blast cell, holding room). That bill drops to RM30,290 — a 39% reduction. At 120 tonnes of frozen whole durian shipped per month, energy cost per kg slides from RM0.42 to RM0.25. Payback lands at 47 months before applying MIDA’s Green Investment Tax Allowance (GITA), which credits qualifying solar capex against statutory income and compresses that to roughly 31 months. Solarvest and Ditrolic both quote comparable C&I installs across the Bentong–Raub corridor, and the PVsyst 8.1 models match the measured meter data closely enough that Malaysian banks fund the capex against the verified TNB history.