Solar Cold Storage for Farms - Post-Harvest Preservation in Pakistan

Key Takeaways

• Published estimates of post-harvest loss for fruit and vegetables in Pakistan are mostly 30-40% of production: the Asian Development Bank figure cited by the Pakistan Business Council, and the same range in a 2019 newspaper report of an ADB paper. A 2001 newspaper summary gave 25-40 per cent, and a trade-press attribution of 20 to 40% to the FAO could not be traced to an FAO document.
• In a 2008 kinnow survey, contractors listed losses at picking, handling, packing and transport. A farm cold room is one fix, not the whole answer.
• We found no published price for a farm-scale solar cold room in Pakistan, so this guide does not print one.
• "Up to 36 hours" of thermal backup is a vendor or agency claim for particular Indian products. Other sources give up to 30 hours, 24 hours, a few hours, or, in a press report of a draft Indian standard, two days.
• Set-points differ by crop in a 1995 FAO-hosted manual: 13 C for mango, 4 C for mandarins (kinnow is not listed by name) and 18-22 C for mature-green tomato.

Introduction

Pakistan has little cold storage at the farm gate. The Pakistan Business Council says farm-gate cold storage is the most critical missing link and proposes 5,000 solar-powered modular cold rooms at village and farm-gate level over five years. That is a recommendation, not an installed base. This guide sets out what the published sources do and do not show about solar cold rooms, so you can ask a seller better questions.

How much produce does Pakistan lose after harvest?

Estimates differ by crop, stage and source. None is a measurement of what a farm cold room would save.

A 2001 Dawn summary of a paper already put post-harvest losses of vegetables and fruits at about 35 per cent.

Where the loss happens matters. The 2008 CABI survey asked kinnow contractors where fruit is lost, in percent: picking 5, handling 2.5, packing at farm 5, transportation 5-20 and others 5. Storage itself is not one of the listed categories.

What does a solar cold room look like in practice?

The only peer-reviewed Pakistani solar cold room we found is a prototype at the University of Agriculture Faisalabad, published in 2021. Its abstract describes a 21.84 m3 cubical unit with a storage capacity of 2 tonnes. It is not battery-free and not fully off-grid: a hybrid system of 4.5 kWp PV, a 5 kW hybrid inverter and a 600 Ah battery bank powered the entire system, with 30% of power consumption from the grid and 70% from solar PV modules. Potatoes were stored at 8 C for three months, and total weight loss was 7.64%. For night cover it used three cooling pads filled with brine solution. The abstract gives no purchase cost.

Indian units show the scale of equipment, in Indian rupees, which we have not converted:

One lakh is a hundred thousand. In Pakistan, a commercial apple store in Killa Abdullah, Balochistan, reportedly invested Rs24 million in solar panels and batteries and still relies on diesel at night. The Pakistan Business Council says some commercial operators have installed solar to cut their electricity burden, but that the capital outlay puts it out of reach for most smaller investors. It also puts electricity at approximately 80% of cold storage operating costs, and says a conventional 1,000-ton cold room may cost PKR 150 million to build. A Pakistani cold-room supplier's page answers the price question without a price: it follows floor area, target temperature, panel thickness and the refrigeration unit.

How long does thermal storage hold?

Several designs store cold in thermal storage such as phase-change material instead of batteries. The hours quoted are vendor, agency or design claims, most without load, ambient temperature or door-opening conditions. We found no independent measured test.

A practitioner guide from Efficiency for Access and the International Institute of Refrigeration says a battery-free solar cold room will need thermal storage autonomy of several days in many tropical locations where cloudy rainy weather coincides with the season when product requires sustained cool storage. ColdHubs in Nigeria says its second-generation room uses phase-change materials in place of batteries but publishes no hours figure.

What temperature does each crop need?

The Pakistan Business Council notes that potato-optimized cold rooms, which typically maintain 2-4 C, are largely unsuitable for tropical fruits requiring different temperature and humidity regimes. An FAO-hosted manual (1995) gives these recommendations:

The manual is old and sets general values, not Pakistani ones. Ask a seller what set-point their room holds for your crop.

What do farmers gain from storing?

No source we found gives a payback period for a solar cold room in Pakistan. What exists is about prices and about other countries:

• Pakistan, potatoes. The Business Council says a 120 kg sack of potato fetched PKR 5,000-5,300 in 2024-25, then collapsed to PKR 1,200-1,500, barely above the PKR 1,000 cost of six months of storage. The brief does not say whether that storage cost is for a solar or a conventional room. It adds that when prices are high, farmers and traders have no incentive to store.
• Pakistan, kinnow. Contractors told the 2008 CABI survey that if the quantity to be sold is large, price goes down by as much as 50 percent. That is their perception, not a price series.
• India, rent saved. A paper on a 10 t air-conditioner-based store estimated the cost could be recouped from rent benefits within 2.1 years, assuming $20.46 of storage rent saved per tonne per week at an average 70% utilization of the 10 t capacity. That is rent avoided, not a higher sale price.
• India, a pilot. The TERI room in Karnataka earned Rs 40,000 in rental income in its first year, against Rs 14 lakhs for the equipment. The page does not count the spoilage the farmers avoided.

Which crops benefit most?

The Pakistan Business Council says losses are especially severe for mangoes, kinnow, tomatoes and potatoes, and that onions, tomatoes and other perishable vegetables collectively suffer the highest absolute losses. It adds that mangoes are extremely temperature-sensitive in the first 24 to 48 hours after harvest, so pre-cooling and transport matter as much as storage. In the FAO-hosted perishability table, mature potato sits in the least perishable class. Dairy is a separate system from a produce cold room and is not covered here.

Summary and Recommendations

• Ask for an itemised written quote showing capacity in tonnes, array in kWp, whether there are batteries or a thermal store, and the grid or diesel backup.
• Ask what holdover the seller has measured at your ambient temperature and door-opening pattern, not what the brochure says.
• Match the set-point to your crop. The Pakistan Business Council calls potato-optimised rooms largely unsuitable for tropical fruit, and the FAO-hosted table sets different temperatures for mango and tomato.
• Work out your own price swing against the cost of storage before you buy. The potato example shows storage can cost nearly as much as the price it protects.
• Look at picking, handling, packing and transport too: in the 2008 kinnow survey those were the listed loss categories.

Correction, 28 October 2026: earlier versions of this guide printed prices for 5, 10 and 25 tonne rooms, a loss rate of under 5 percent after storage, a single temperature range and a payback period. None could be traced to a source and they have been removed.