Scientists with the Horticulture Innovation Lab are testing and adapting a range of technologies aimed at significantly improving the profitability of fruit and vegetable production throughout the world. Given the complexity of horticulture, technologies such as these can reduce constraints that limit the ability of small holder farmers to achieve maximum profitability with high-value horticultural products. The goal is to develop and test technologies that can overcome common limitations in land, labour, capital and infrastructure.

Problem: Post-harvest losses

In much of the developing world, rates of post-harvest loss exceed 50 per cent, and cold storage is virtually non-existent due to the high cost of equipment and limited electricity. Quickly cooling produce after harvest extends shelf life by reducing metabolic activity, water loss and microbial growth. Farmers who can store their produce longer can access better prices, as market prices fluctuate.

Problem: Poor seed quality

In tropical climates, high humidity causes rapid seed deterioration that results in poor stand establishment, lower productivity, reduced market value and a disincentive to invest in improved seeds.

Drying beads:

  • Provide a widely adaptable method for drying seeds and are reusable.
  • Maintain high seed quality during storage.
  • Lead to higher germination rates and increased yield capacity.
  • Increase farmer incentive to invest in improved cultivars.
  • Can be integrated with local seed systems to increase market for local and improved cultivars.
  • In many developing countries, the rate of post-harvest loss for fruits and vegetables exceeds 50 percent. Cool storage can greatly reduce these losses, but is virtually non-existent in many places due to the high cost of equipment. The CoolBot is one option for reducing the costs of a cold room, using a device that tricks an air conditioner into further reducing temperatures in a well-insulated room.

The ideal solution would be to use solar drier for drying the seeds under controlled condition so that the germination would be assured.

The next most important concern is about the post-harvest storage for long period or for short period till the producer gets proper value for his produce. Here the author has designed a very good technology.

The CoolBot

Converts an insulated room and an inexpensive, readily available window air conditioner into a cool room.

Substantially reduces the cost of cool storage for horticultural produce.

Overrides the air conditioner’s temperature gauge, maximising cooling power.

Makes cold storage a viable option for developing-world farmers, cooperatives and market groups to increase their competitiveness.

What is the CoolBot?

The CoolBot was developed by Store It Cold as an affordable way for small-scale farmers to cool crops on their farms. This electronic device overrides an air conditioner’s temperature gauge, tricking it into working harder while preventing components from freezing. With an air conditioner and a CoolBot, an insulated room can be converted into a cool room to store fresh produce before sale, to maintain quality and extend shelf life.

Researchers with the Horticulture Innovation Lab have now tested cool rooms equipped with the CoolBot on three continents, using a variety of configurations related to insulation and power sources for the cool room. Helping farmers find ways to access cold storage to reduce post-harvest losses and maintain fresh produce quality (and thus value) is one important way that the Horticulture Innovation Lab helps fruit and vegetable farmers improve their practices and increase income.

How does a Coolbot work?

Most importantly, when the CoolBot begins to lose efficiency when accessing BTUs of cooling power (when the air conditioner is close to freezing), it is programmed to shut off the compressor on air conditioner unit, so one does not need to pay for electricity to make BTUs that can’t be used.

What is the cooler temperature?

The ideal refrigerator temperature is 35F (1.6C). The user is not hugging the danger zone like he would be at 40F (4.4C), and the user is distancing himself sufficiently from 32F (0C) that he doesn’t freeze half the stuff in the refrigerator.

Because it is not absorbing enough heat, the refrigerant running through a dirty evaporator coil doesn’t warm up as much as it should. This very cold refrigerant causes water vapour in air to freeze rather than condense into a liquid. Eventually, the whole evaporator coil can frost over.

Commercial refrigeration systems are available in most parts of the world and are used for restaurants, stores and other small-scale cold room needs. The system consists of an air-cooled compressor or condenser unit installed outside and an evaporator unit (refrigeration coil) installed inside the cold room. A complete installation also requires electrical connections, a thermostat controller, refrigeration piping to connect the compressor or condenser with the evaporator, and a charge of refrigerant. A system installed in the United States costs about $7000 for 3.5 kW (1 ton) of refrigeration capacity. A small-scale option is to use a modified room air conditioner, a method originally developed by Boyette and Rohrbach in 1993. The control system of the unit is modified to allow it to produce low air temperatures without building up ice on the evaporator coil. The ice restricts airflow and stops cooling. Recently, a company has developed an easily installed controller known as the CoolBot that prevents ice build-up, does not require modifying the control system of the air conditioner (Store It Cold, LLC), and works by overriding the air conditioner’s temperature gauge, tricking it into working harder.

Design Options & Materials Needed

The better the insulation used to build a cold room, and the more air tight it is, the lower the operating costs will be for keeping the room cold. As a general rule, insulation with a minimum rating of R20 should be used in the walls, floor and ceiling. The floor can be covered with plywood or any sturdy surface covering that is easy to clean. Rigid polyurethane foam insulation (available in 4 x 8-foot sheets) or spray-on foam will provide excellent protection from outside heat if a thickness of 3 to 4 inches is used during construction or for retrofitting of an existing cold room. Three inches is enough insulation if the user intends to operate the cold room at 5C (41F) or above. Reflective metal foil bubble insulation (available in rolls in 24” or 48” widths) is a bit more expensive, but provides approximately R30 in insulation rating when using only a single very thin layer. Caulking and weather stripping can help seal any gaps and cracks. Don’t forget to insulate the door and check the door seals for air leaks.


Farmers can store produce to sell in the off-season when prices are higher.

Improved cold storage possibilities will stabilise fruit and vegetable prices, giving consumers access to nutritious fresh produce all year.

Farmers are better protected from erratic market prices.

Next step

The same above cooling system has been operated with solar PV power generation with LiFePO4 battery bank as energy storage devices. The author’s special patentented technology of cell balancing and intelligent charging system enhances the life of the battery to more than 10 years. Thus, the total system can be 100 per cent grid autonomous. According to the vision of Dr A P J Abdul Kalam, grid autonomy is the most essential to make the farmer proper in his agriculture or horticulture. The energy for irrigation or climate control for extended storage life or post-harvest value addition of produce must be totally based on renewable energy sources. Grid dependency has made their life miserable. Kalam also has said that, the experts and technologists must take latest innovative and cost-effective technologies to the doorstep of farmers adding to this his strong belief was “if farmer’s economy improves then and then only the nation’s economy will improve.”