New tool kit for better energy efficiency in the greenhouse

Energy efficiency is more than simply reducing the amount of electricity used on farm. It involves using electricity or fuel efficiently to get the most output from your equipment at the least practical cost. by DAVID HUNT

Energy, particularly electricity, has been a relatively cheap and readily available resource in the past. However, with a global push to reduce greenhouse gas emissions and the increasing costs of electricity and fuel, the protected cropping industry has seen profit margins eroded by direct and indirect energy costs.

Managing energy and environmental emissions is a major challenge for the protected cropping sector. These factors influence the industry’s capacity to provide a consistent, cost-effective supply of fresh, high-quality food, and will become increasingly important in determining profitability as energy prices continue to rise.

To address these issues and identify the options available to the industry, a project was developed with the support of the vegetable industry levy to investigate how energy use in protected cropping can be controlled or reduced, and to look at alternative systems to offset energy use.

Three main questions were considered:

• How and where is the energy being used?

• What directly and indirectly influences energy costs in protected cropping?

• What methods or options are there to reduce energy costs?

A self-assessment tool kit was developed to assist growers in finding answers to these questions. The tool kit consists of a questionnaire for recording equipment details and calculating energy use for different production systems, and a reference manual to provide explanations and examples of how energy can be saved across an entire facility. A website has also been developed as a central point for growers to access other information on equipment reviews and alternative heating technologies as well as links to other websites for further reading.

Together, these resources provide a simple, three-step process to identify all energy-using equipment and systems, calculating what they cost to run over a year, and the options or low cost methods that may be available to improve energy efficiency. This step-by-step method will help to target equipment or systems that can be easily improved for an immediate reduction in energy costs, or to highlight equipment that should be upgraded to more efficient technology.

Energy use in a greenhouse facility is broken down to four main areas or systems: the structure and covering material; the irrigation and water treatment system; climate control systems; and post-production or support systems. Although these areas are discussed as separate systems in energy assessments, each will influence energy efficiency in the other areas. The level of technology used in each area will also determine the extent of influence each has on the whole-of-farm energy use, as well as the potential level of energy savings.

For example, a high heating fuel bill may not be due to an inefficient heating system; it may be that the greenhouse covering has a high heat loss (high U-value), is torn and damaged or there are gaps around entry points, which allow hot air to escape. In this case, there is little benefit in installing a new boiler for heating without addressing the air leaks in the system. A new boiler would simply be burning fuel more efficiently to compensate for the lost heat. Instead, it would be better to consider the following options:

Hole in polytunnel

Hole in polytunnel

• replace the greenhouse covering with one that has a lower U-value (better insulation) to reduce boiler operation by 40%

• stop hot air (heat energy) loss by patching tears or holes in the covering and plugging gaps by installing weather strips around vents, louvers, pipe entry points or doors

• repair any damage to the insulation on the hot water distribution pipes to stop heat loss during distribution to reduce boiler operation times

• replace old or damaged thermostats with a new electronic thermostat to provide more accurate readings; a 10C improvement in accuracy can lead to hundreds of dollars in fuel cost savings

• calibrate thermostats to ensure readings are accurate

• check and adjust climate control parameters to stop or reduce clashes, such as venting while heating

• service the burner and clean the heat exchangers in the old boiler to increase burning efficiency by up to 10%.

By implementing these changes heat retention and energy efficiency can be increased within the greenhouse by reducing the workload and fuel required to maintain greenhouse temperatures. Fixing air leaks will improve the efficiency of the ventilation system and air circulation, creating a more uniform and stable growing environment, which in turn will reduce the work and energy required by the climate control system. These examples show how assessing a greenhouse facility and applying some simple, low-cost methods can have a large impact on the whole-of-farm energy use. Some simple changes or upgrading just one piece of equipment could provide an increase in productivity to pay for the maintenance.

Alternatively, the assessment might lead to a decision to install a new, high-tech solution as the more appropriate way to improve efficiency. The ultimate aim is to accurately identify the best course of action for each unique situation and operation.

Opportunities to increase energy efficiencies are as varied as the structures and equipment available to suit the different farming operations throughout our diverse Australian climate. Each greenhouse facility needs to be assessed individually in order to identify where energy can be saved or efficiencies implemented.

The new self-assessment tool kit will allow each greenhouse manager to conduct their own tailored energy audit, giving them the capacity and flexibility to discover innovative ways to make a big difference to their energy bills. With each greenhouse production system that becomes more energy efficient, another significant step will be made towards ensuring the sustainability and long-term future of the protected cropping industry.

About the author Formerly with Queensland Department of Agriculture, Forestry and Fisheries, David is now an environmental and horticultural research consultant who focuses on energy and water use efficiency for the protected cropping and lifestyle horticultural industries. Email:

For more information on the self-assessment tool kit or to learn more about energy efficient technologies for greenhouse production visit:  Ω

15 October 2013