A new design and construction project for Piersons

Meadow Mushrooms’ production facility has benefited from Piersons’ expertise in the design and installation of new heating and cooling equipment

Located in Hornby on the edge of Christchurch, Meadow Mushroom’s production facility is where most mushrooms sold in New Zealand are grown. The site is split into two shelf farms and one packaging facility, with the work by Piersons Refrigeration & Air Conditioning focused on Shelf Farm 1.

“Shelf Farm 1, over the past few years, has been suffering from reliability issues and high power consumption, leading to the overall running cost of the farm being far higher than desired. With the previous setup, the cooling and heating for the farm were delivered by three 750-kilowatt chillers, two of which were heat-reclaimed units capable of supplying low-temperature hot water. The chilled and heating primary and secondary water loops were also serviced via fixed-speed hydraulic pumps, further adding to the inefficiency of the plant,” says Matthew Thomas, Managing Director of Piersons Refrigeration & Air Conditioning.

“The most notable issue and root cause of the main problems experienced on site was the use of the heat reclaimed chillers as the main source of heating. As the site has inherent varying heat load conditions due to the mushroom growing process, this causes a large imbalance between the heating and cooling demands.

“This is especially important when we have a simultaneous heating and cooling requirement.”

Due to the limited knowledge of how exactly the farm behaved from a thermal standpoint, the Piersons team suggested staging the design and installation, allowing calculations to be performed.

With the aim of the project to enhance efficiency and reliability, and reduce the carbon footprint of Shelf Farm 1, the solution included:

• Replacing all primary and secondary pumps with VSD-driven units to enable the control of water flow. This also included the installation of various measuring stations for data collection.

• Replacing two of the existing chillers with two 750-kilowatt Daikin screw chillers.

• Replacing the third chiller with a high-efficiency 690-kilowatt smart magnetic centrifugal chiller.

• Installing two 200-kilowatt water source Daikin digital screw heat pumps for the low-temperature heating requirements.

The main areas of efficiency gains are thanks to the configuration of the heat pumps and the selection of the smart chiller.

“The smart chiller has been installed for its outstanding efficiency and low load conditions,” says Matthew, with COPs of 26+ being seen.

“On the heating side, we have used the chilled water return as our heat source for the heat pumps, essentially meaning we are recovering a portion of the energy absorbed via the chillers that would otherwise be rejected to the atmosphere and reusing it for our heating. As Meadow Mushrooms are highly motivated with regard to reducing the CO2 emissions of their operation, all three chillers and both heat pumps operate on the very low GWP refrigerant R1234ze, which has a global warming potential of just seven. By contrast, the old units operate on R134, which has a global warming potential of 1430.”

Piersons Refrigeration & Air Conditioning has delivered an impressive design that has exceeded expectations, with the production plant already seeing power savings in excess of $10,000 a month.

piersons.co.nz