When you warehouse and ship billions of pounds of food in the U.S.—food that is sold in Walmart, Costco and your local grocery store—food safety is a priority. Product must be protected and in the most energy-efficient way possible.
That’s the challenge Lineage Logistics faces daily. A food processing, warehousing and distribution company, Lineage Logistics controls 20 to 25 percent of the U.S. third-party cold food chain, said Elliot Wolf, director of analytics at the San Francisco-based company.
“We move an average of 20 billion to 30 billion pounds of food through our warehouses each year,” he said.
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Food producers such as meat companies, strawberry growers and seafood importers use Lineage Logistics warehouses—of which there are 111 located in 26 states—to process and/or store their products. You can think of Lineage Logistics as a stepping stone between the food suppliers and the grocery stores and restaurants.
“We have 3,000 to 5,000 customers, and about 100 of them make up the bulk of the volume—they’re the who’s who of the U.S. food industry,” Wolf said.
Using IoT sensors to protect the food
To ensure the warehouses remain at the correct temperatures and that the refrigeration systems don’t fail, Lineage uses temperature and vibration sensors from Monnit Corp.
Temperature sensors ensure all parts of the warehouse remain at the desired temperature. For example, sensors help Lineage detect variations in temperatures within its warehouses. Due to various factors, such as doors opening and thermal load from the roof, one side of a warehouse can be several degrees warmer than the other.
"In order to keep the entire warehouse in spec, we would end up cooling some parts to several degrees lower than we need. Having visibility for temperatures in different areas of a warehouse allows us to adjust airflow to lower that gradient, saving us on cooling costs,” Wolf said.
The temperature sensors also allow Lineage to micromanage the cooling zones. Coolers have one temperature setting, while freezers have another. Micromanaging the zones helps prevent coolers from getting too cold and freezing the products.
And vibration sensors—measuring vibration magnitude and vibration count—help detect and prevent problems in the refrigeration system, Wolf said.
The vibration count sensors are on the refrigeration compressors. If a bearing in a compressor starts to go out, the compressor will vibrate. Having sensors on them, allows the crew to address the problem before the compressor breaks, preventing high repair costs.
Another common problem in refrigeration is what’s called liquid hammer, Wolf said. It’s a pressure spike caused when fluid flowing through the refrigeration pipes is forced to stop or change direction suddenly.
“All of that energy gets discharged into the piping, and it can damage the pipe, causing leaks and any number of not-very-pleasant problems,” he said. “So, we use accelerometers with the vibration sensors to detect liquid hammers. They can tell us if a valve is broken or something is wrong with the system.”
Wolf said it was a long process to find sensors that met the company’s three priorities. The sensors had to:
- Be inexpensive, so they could use a lot of them to get the best possible view of what is happening in the giant warehouses.
- Be battery-powered so they could be put anywhere. And the batteries had to be long-lasting.
- Function in an “extremely challenging radio environment.”
“We found a lot of sensors, but the batteries might run out every couple of months. That’s no big deal if you have easy access to the sensors, but if I have a 500,000-sq.-ft. warehouse with several hundred of these things in it—often very high up in the rack—I don’t want to be replacing batteries all of the time,” he said. “So, Monnit fit the bill. They were reasonably priced. They had good technology and weren’t trying to send so much bandwidth on a high-frequency radio signal.”
Lineage currently uses approximately 1,500 AA battery-powered wireless sensors from Monnit across a few of its facilities, and they look to expand that into many more buildings in the near future. A sensor is placed every few meters to create a matrix and produce live temperature maps. The sensors gather data and send it to Monnit’s cloud system. Monnit then pushes the sensor data to Lineage for it to create the temperature maps.
“Monnit’s cloud system basically executes a web address that has embedded data in it. So, we use that feature to send the data to Amazon Web Services. And in there, we do all of the processing and visualization,” Wolf said.
The process is automatic, he said. As the sensors report, the data gets updated and the maps get updated. One map is on a television in the building so the crew on site can see what the thermal condition of their building looks like.
Using temperature sensors to reduce energy costs
It costs hundreds of thousands of dollars to refrigerate a warehouse. Wolf said the power bill for Lineage’s biggest facility during peak months is $450,000. The energy usage during that time is about 9.5 megawatts, “which is a small city,” Wolf said.
The cost would be more if Lineage didn’t follow a process that allows it to purchase power when it’s cheap. The company buys power when the cost is low and pre-cools the warehouse. Then when the cost for power is expensive, they turn off the refrigeration.
“I have these giant frozen warehouses filled with water-based substances. I can turn off the refrigeration system, close the doors to our insulated structure, and the temperature will move only half a degree, which is pretty low,” Wolf said.
He couldn’t do that, though, if he didn’t have temperature sensors monitoring the warehouses.
“Imagine us, especially in southern California, which has massive intra-day power swings, we want to very precisely schedule to take advantage of that as much as possible,” Wolf said. “Now imagine, though, in doing that I’m thermocycling several billion dollars’ worth of food. I wouldn’t dare do that unless I had a sensor every 10 feet, making sure we were absolutely safe.”
Wolf said the process allows Lineage to turn its power bill into a profit center while ensuring the food is protected.
“The grid has this problem of too much renewables [creating surplus energy]. We have a solution in that thermally we can, with a reasonably high amount of impunity, decide when we consume power,” he said. “So, you follow the chain of what you need to have to take advantage of that capability—and sensors everywhere is high on the list.”
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