British Potato 09: Install sub-meter to save energy costs in store

Spending less than £500 on a sub-meter for your potato store could immediately trim up to 10% off your electricity bill, Adrian Cunnington told potato growers during a seminar on storage costs.

Very few growers knew how efficient their store was, he said. “By putting in a sub-meter, which cost from about £300, growers would instantly get a picture of how much energy they are using. And because they were thinking about energy use, they would immediately seen gains of up to 10%.”

The meters would also pinpoint how efficient stores were and help growers improve performance, he said.

A joint Sutton Bridge Experimental Unit and Farm Energy project has been monitoring stores over the previous two seasons to help investigate stores’ energy costs.

The results for processing stores showed a three-fold difference in energy use ranging from 17kWh/t to 55kWh/t, Mr Cunnington said. “You’re looking at £2/t for the most efficient store up to £8/t. That’s a dramatic difference.”

Optimal stores were likely to feature technology advances such as inverter drives, adiabatic cooling, as well as high-quality insulation and sealing, he said.

Inverter drives, which cost about £3000 to install, offered significant savings if fans were suitable. “If you can run the fans at 80% of the maximum speed, it uses 50% of the power.”

Adiabatic cooling was more expensive, costing between £15,000 and £20,000, but allowed store managers to bring air in from outside at the same temperature as the store, reduce its temperature by putting it through a humidifier, which then could be used to cool the crop.

Store managers should also consider whether it was possible to run the store at 1-1.5C higher temperatures than currently, which would increase the number of days ambient air could be used.

In cold stores, making sure the air circulates fully around the store by building a plenum around the fridge to prevent air from short circuiting back to the fridge could improve performance. A simple tarpaulin to separate the air being delivered to the store from the returning air could also achieve the same effect, he said.