Providing the market with 800 tonnes of red onions annually, and storing up to 12,000kg at a time, off-site storage was a costly solution and at times logistically problematic for Roper & Sons Ltd. A firm, crisp restaurant-quality onion needs to be kept at around 1.4°C. As onions give off heat, consistent temperature control is crucial. The company’s expansive, barren building had possibilities, but it was deemed unusable with its own limitations.
However, the eureka moment happened when owner/operator Lance Roper read about existing building conversions using the unique insulating properties of foam. Two months after consultation, a cost-efficient, functioning operation was in full swing. He now reaps the benefits and opportunities from storing produce on site. NZ Foam Insulation and Snow Temp Heating and Cooling Solutions collaborated to create the only possible solution on an economically viable budget.
"Snow Temp and NZ foam worked together to provide cooling solutions for the storage of 240,000kg of Red Onions at 1 °C," explains Graham, SnowTemp. "An old chicken shed was available which NZ Foam spayed with 80mm of foam and Snow Temp supplied a division wall and the main door constructed of 100mm polystyrene panel to create an insulated environment."
NZ Foam sprayed the inside of the concrete walls and the tin roof with 80mm of permanent, inert, airtight rigid closed cell polyurethane spray foam to greatly prevent heat entering from the outside. The foam in isolation saw a rise of only .9° over a 20-hour period. So when combined with the Snow Temp air-conditioning system, an even cool temperature is retained by the two 7HP, air-cooled, three-phase, hermetically sealed condensing units, and four ceiling-mounted evaporators for even air circulation — a system with a 27,000-watts at -5°C ET total capacity. Snow Temp created two spaces, with separate digital-controlled temperature, for storing other produce like pumpkins that need a warmer environment.
"Our design model was based on refrigerant R407F coupled to four matching evaporators, providing the condensing units which were located outside on the ground for easy servicing and cleaning," explains Graham. "There are four evaporators mounted down the centre of the room to allow for air distribution and circulation around the products. Each room has two evaporators and individual digital temperature control. With this set up we are able to control each space individually or as one."
"During the commissioning phase the product temperature was down to 2°C and with the refrigeration equipment isolated, the temperature rise of the product was 0.9°C over a 20hr period proving the performance of the insulating properties of the spray foam," says Graham. "This was the first project where we have used foam in this type of application and have been most impressed with the results and the application."
Lance from Roper & Sons says when there’s a rise in temperature, especially when new onions are brought in, it is now possible for the room temperature to lower back to the ideal temperature within three hours. Condensation and carbon dioxide are also kept to a minimum. Lance says he couldn’t have achieved this amazing result any other way.