YOUR INDUSTRY
REDUCING DEMAND FIRST STEP IN ANY ENERGY STRATEGY Words by Andrew Bristol
EECA Business Products Manager, Glenn Wellington discusses energy with Rob Lindsay
Understanding energy use and reducing demand should be the first step in any energy strategy, was the advice to covered crop growers at TomatoesNZ and Vegetables NZ’s covered crop energy workshops in May. “Start by saving energy by determining a temperature regime that is economically optimal,” said Elly Nederhoff, the greenhouse specialist who has been contributing to the NZGrower since late last year (see page 60 of this NZGrower for Elly’s latest article). Elly addressed the workshops along with several growers and representatives of TomatoesNZ and Vegetables NZ. “In the past year, we have reduced our fuel consumption by 10% just by making small changes, while at the same time we have increased our yield and fruit quality,” said Rob Lindsay of Island Horticulture, who grows two hectares of cucumbers under cover near Kaiapoi (see also NZGrower February 2021, pages 20–21). “We have eight different growing structures – both glass and twin skin greenhouses, ranging in age from five years up to 35 years old. We have two boilers, one that’s been converted to run on re-refined oil and a new boiler that’s used re-refined oil from the outset.
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We wanted to make efficiency gains through small investments, to make sure we are making the best use of fuel and are minimising energy loss.”
Rob focused on three areas: 1 Better use of screens.
2 Reducing boiler water temperatures in response to
solar radiation.
3 Use of a ratio of temperature to radiation strategy.
“We have single screens in our glasshouses,” Rob explained. “The screens we use reduce energy loss by 47% and can also be used for 15% shading during periods of high solar radiation. We grow cucumbers all year round so we need the ability to save energy during the winter so we can continue production.”
Multiple triggers Rob said they use multiple triggers for their screens. “We use PRIVA as our climate control software. It gives us the ability to have up to eight time-based periods over 24 hours. For each of those periods, we have a number of triggers that prompt the screens to close: outside temperature, radiation, and inside/outside differential.
