Khanya Cold Chain Business Plan — The Energy Strategy

Why electricity is the dominant operating cost in refrigerated storage, and how solar and storage convert a tariff risk into a margin advantage.

The Energy Strategy

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4.1 Why this section comes before operations
4.2 The thermal flywheel
4.3 Solar and standby generation
4.4 What this is worth, and what it is not
4.5 What the load-shifting day actually looks like

4.1 Why this section comes before operations

In most logistics businesses, energy is a line item. In frozen storage it is a design decision that determines whether the business is competitive, and it must be made before the building is specified rather than optimised afterwards. This section is placed ahead of operations for that reason.

The relevant fact is not the level of the electricity price but its shape. Eskom’s Megaflex tariff, the standard time-of-use tariff for larger industrial sites, charges 720.19 c/kWh for a unit drawn in a high-demand-season weekday peak block and 120.03 c/kWh for the same unit drawn overnight, both excluding VAT.

Figure 7. The Megaflex active energy charge across a high-demand-season weekday. The store's objective is to buy as much of its energy as possible in the low blocks.

4.2 The thermal flywheel

A frozen chamber holding 2 600 pallets of product at −25°C stores an enormous quantity of thermal energy. Product temperature moves slowly; the chamber can be driven down to the bottom of its tolerance band overnight when energy costs 120 c/kWh, and the compressors can then be substantially unloaded through the morning and evening peak blocks while the product drifts upward within specification. Nothing about this compromises the cold chain, provided the tolerance band is defined, monitored and logged, which the quality system in Section 8.2 requires in any case.

Design decision	Capital cost	Why it is required
Variable-speed drives and a well-zoned ammonia plant	R27 600 000	Fixed-speed compressors cannot modulate through the peak; they simply run or do not
An envelope specified beyond code	R16 900 000	Thicker panel, better vapour barrier, air locks and rapid doors reduce heat ingress, which is what makes drift through a two-hour peak block survivable
Battery storage of 600 kWh	R2 900 000	The battery is not there to run the plant. It manages notified maximum demand and covers the short peak overlaps that thermal mass alone cannot absorb

4.3 Solar and standby generation

A 700 kWp rooftop array at R9 100 000 supplies roughly a third of total consumption. The fit is unusually good: a cold store’s daytime load profile and a solar generation curve peak within a few hours of each other, so almost all generation is self-consumed at the standard-block price rather than exported at a lower credit. Standby generation of 1.2 MVA covers residual outages, modelled at 1.5 per cent of grid consumption at a diesel cost far above grid rates.

Strategy	Year 3 cost	Saving	Cumulative saving
Flat grid consumption, no shifting, no solar	R5 175 719	—	baseline
Time-of-use load shifting only	R4 152 612	20%	R1 023 107
Load shifting plus 700 kWp solar	R2 740 724	47%	R2 434 995
As modelled: shifting, solar and standby generation	R2 904 932	44%	R2 270 787

Figure 8. Electricity as a percentage of cold store revenue, with and without the strategy.

4.4 What this is worth, and what it is not

4.5 What the load-shifting day actually looks like

Block	Hours	Charge	Plant behaviour	Chamber temperature
Off-peak overnight	22:00–06:00	120.03 c/kWh	Compressors run hard; chambers driven to the bottom of the tolerance band	Falling to −27°C
Morning peak	07:00–10:00	720.19 c/kWh	Compressors substantially unloaded; battery covers demand overlap	Drifting up within band
Standard daytime	10:00–18:00	Roughly 280 c/kWh	Solar carries most of the load; compressors modulate to hold set point	Held at −25°C
Evening peak	18:00–20:00	720.19 c/kWh	Compressors unloaded again; no solar; battery supports demand	Drifting up within band
Standard evening	20:00–22:00	Roughly 280 c/kWh	Recovery begins as the tariff falls	Returning toward −25°C

Two features of this cycle make it work. The chamber is never operated outside the documented tolerance band, so the load shifting is invisible to the customer and to the certification auditor; and the daytime standard block is carried substantially by solar, so the highest-consumption hours draw the least grid energy. Neither is available to an operator with fixed-speed compressors and no on-site generation, which is the structural advantage described in Section 1.2.

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