Sensors & transducers
Water is constantly recycled at all of the JFC facilities with continuous measurements of pH and conductivity helping to ensure the regulation of plant nutrients with dissolved fertilizers. The Vaisala sensors measure temperature, humidity and carbon dioxide; all of which have significant impacts on the growth of plants. “We chose the Vaisala sensors because we need long-term accuracy and reliability, and the control system can only be as good as the sensors, so it makes sense to use the best,” Au explains. JFC’s control systems have been designed by head of Engineering, Christoph Grundmann, who’s past experience includes work in satellite communications with the BBC and Arqiva, and in the design and implementation of power station control systems. The monitoring and control systems at all of JFC’s facilities are working very well, with no significant downtime. JFC’s Innovation Centre control systems were programmed and commissioned by Luke Grundmann who was particularly impressed with the prompt and proactive support provided by Vaisala engineers to connect and configure their modbus RTU sensors using a generic USB to RS485 converter and freeware software. “The special programming lead had not arrived but even so, the Vaisala engineer skilfully guided me through the process using what I had to hand,” Luke explains. Christoph utilises Vaisala sensors as standard, following previous experience with them in a grain dryer control system. He says: “At JFC, we are seeking to produce crops as cost-effectively as possible, but it would be a foolish economy to purchase low-cost sensors, because the cost of failure would be high, and the reliability of the Vaisala sensors means that the cost of ownership is low.
“It was also important for the sensors to have MODBUS communications capability, which saved a significant amount of time and money
during installation, and means that any future changes will be quick and simple to implement.” Temperature and humidity at the JFC facilities are controlled by a separate HVAC system, but Christoph says: “The HVAC at JFC1 came with its own sensors, so we have replaced them with Vaisala’s. At JFC2 we will use the Vaisala sensors to check and validate the measurements being made by the HVAC system, and intervene if necessary.” The first harvest for JFC2 is due in the summer of 2023, and with 15 layers, every acre becomes 15 times more productive. The roof of the new facility is entirely covered with solar panels, and 100 per cent of energy will come from renewable sources. Rainwater will be harvested and filtered, and almost 95 per cent of water will be recycled.
In order to maximise the efficiency of growing conditions in JFC2, the entire facility will be
monitored by a network of Vaisala sensors
including: 46 RH/Temp sensors; 12 CO2 sensors; 10 Temp/RH/CO2 sensors; two atmospheric pressure sensors, and a Vaisala
WXT 530 series multiparameter weather station. Commenting on the monitoring system,
Vaisala’s Antti Viitanen says: “The accuracy and reliability of these sensors will be crucial to the efficiency of the ongoing demand- controlled management of plant growth conditions, because accurate measurements help maximise crop production, whilst avoiding waste and minimising costs.”
SUMMARY
The principal advantages of vertical farming over traditional methods almost all relate to sustainability. Soil and biodiversity are unharmed; greenhouse gas emissions are substantially lower; water efficiency is dramatically improved with no unnecessary evapotranspiration, borehole depletion or leaching. Space is used efficiently to accommodate an urban setting where necessary, and to lower food miles. Importantly, fresh produce can be available on any day of the year, no matter what the weather or season. However, escalating food production costs mean that the success of new vertical farms will hinge on their ability to monitor and control inputs effectively, which is why sensor quality is so important. Looking forward, Christoph plans to further enhance JFC’s sustainability credentials with
initiatives such as utilising CO2 from anaerobic digestion, and employing compostable growing media that could undergo anaerobic digestion. He is also evaluating the calculated dew point output of the Vaisala sensors to determine whether this would be a smarter way to control the HVAC systems. In addition, with the help of Vaisala’s experts, he is looking at enthalpy measurements for the inside and outside environments to determine the most efficient HVAC re-circulation (fresh air ratio).
Vaisala 30
www.vaisala.com May 2023 Instrumentation Monthly
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