Solar cold rooms so farmers stop losing a third of the harvest

A third of it rots before it is sold

Post-harvest loss for tomatoes, peppers and leafy vegetables on the Jos plateau runs at somewhere between thirty and forty-five per cent depending on the season. A farmer picks on Monday, carries the crop to market, and has until roughly Thursday before it is worth nothing. That deadline is what gives traders their leverage: everyone knows the farmer cannot wait, so the price on offer at midday Wednesday is the price.

This is not a farming problem or a yield problem. The crop is grown, harvested and brought to market successfully. It is a temperature problem for three days, and it costs the farmers on this plateau more than any pest or drought in the last decade.

What we are installing

Six walk-in solar cold rooms, each about twenty cubic metres, at six market sites. They run entirely on their own solar array with thermal storage rather than batteries, so they hold temperature overnight and through cloud. Critically, they are run as businesses: farmers pay a small daily rate per crate, the co-op collects it, and the income covers maintenance and eventually the replacement unit.

• Six 20 cubic metre cold rooms, each serving between 120 and 300 farmers.
• Solar direct with phase-change thermal storage — no battery bank to replace in four years.
• Run by the market co-ops as a paid service, at a rate the co-ops set themselves.
• Each unit is expected to cover its own maintenance and build a replacement fund by year three.

The budget per site, times six

A single installed cold room comes in at about $12,900. The rest is the training, monitoring and spares that determine whether it is still working in five years.

• $46,800 — Six cold room units Insulated panel construction, assembled on site, with a two-year warranty from a supplier with installations in three states.
• $21,600 — Solar arrays and thermal storage Sized for the worst month of the rainy season rather than the average, which is why this line is larger than people expect.
• $7,900 — Site works, foundations and security fencing Slabs, drainage and a fence at each of the six market sites.
• $5,400 — Co-op business training and first-year support Pricing, bookkeeping and maintenance training for two people per site.
• $4,300 — Spares pool and three years of maintenance Compressors and controllers held centrally in Jos, with a technician on a retainer.
• $2,500 — Monitoring, evaluation and platform fees Independent measurement of loss rates and farmgate prices before and after.

The trader is not the villain here. He simply knows the tomatoes will be worthless on Friday, and so does the farmer. Change that and the conversation at midday on Wednesday changes with it.

Who is behind this

Tidewater Climate Trust is funding and coordinating; the units are installed by a Nigerian supplier who has thirty-one similar installations running, and they are owned by the six market co-ops from the day of commissioning. We hold no ownership stake and take no share of the usage income. Our only ongoing role is the monitoring, which is contracted to an agricultural economics team at a Nigerian university so that the numbers are not ours to flatter.

Risks and challenges

The risk that has killed similar projects is what happens when the first compressor fails and nobody has money to fix it, which is why maintenance is funded for three years and why the units are run as paying businesses from day one rather than as free infrastructure. Usage pricing is genuinely difficult: too high and farmers do not use it, too low and the replacement fund never builds. The co-ops set their own rate and two of the six may get it wrong in the first season. Grid-free operation removes the biggest failure mode but the arrays are a theft risk and each site is fenced and insured. If we fund short, we install four sites properly rather than six marginally.