Learning To Conserve by A.J. Both

Learning To Conserve by A.J. Both

Rising energy costs this century have had a particularly severe impact on the greenhouse industry because structures are generally designed for maximum light transmissions and not maximum heat retention. While fluctuations in future energy prices are likely, the general consensus is that prices will remain high.

Energy use and management will continue to have a significant impact on our industry. While it is likely conventional and alternative energy sources will continue to be used by the greenhouse industry, new improved energy collection and storage technologies offer the potential for future commercial greenhouses to be net energy producers rather than energy consumers.

Conservation

The past three decades have shown that before considering the installation of new energy equipment, it literally paid to operate existing energy systems as efficiently as possible. Over the next decades, it is likely the cost of implementing energy conservation measures will continue to be less than the cost of installing new high-efficiency energy technologies. These conservation measures include, but are not limited to:

– Installing twin-layered covering materials.

– Using energy curtains.

– Installing insulation where appropriate.

– Reducing unwanted air exchange through unintended openings in walls and roofs.

– Periodically verifying that environmental control systems and strategies are operating as intended, and keeping track of energy usage and expenses.

Technology

Recent heating technology developments enable growers to further reduce their energy consumption. These technologies include high-efficiency direct-fired unit heaters that mix and discharge heat and carbon dioxide with ambient air and condensing boilers that recover heat by allowing condensation of the exhaust gases. Another improvement is the use of combined heat and power (CHP) systems that generate electricity for use in the greenhouse while excess electricity is exported to the local utility grid, and heat from heat exchangers incorporated in the exhaust system that removes the combustion gases.

Heat pumps are reversible refrigerators that can heat or cool the greenhouse environment with a single system depending on the flow direction of the refrigerant. Designing heat pump systems for the maximum heating and cooling loads of greenhouses results in reduced overall system efficiencies, but reasonable efficiencies can be attained for systems designed to handle the first few heating and cooling stages.

The use of heat pumps, heat exchangers and insulated water storage allows for closed greenhouses that no longer require air exchange with the outside environment for cooling purposes. The benefits of closed greenhouses include increased production from higher carbon dioxide concentrations, reduced insect pressures and reduced water use because transpiration water can be recovered.
Finally, the use of light emitting diodes (LEDs) for supplemental lighting of greenhouse crops promises to significantly reduce the overall energy use of year-round greenhouse production that relies on artificial lighting during the darker winter months.

Storage

The energy efficiency of greenhouse systems can be greatly increased by adding capability to store excess energy for later use. “Later” can be later in the day, later in the week or even later in the year. Excess energy is typically stored in insulated water tanks or in underground aquifers. Combining a heat pump with heat exchangers and energy storage makes for a particularly efficient energy system, because the heat pump can operate at its highest efficiency over long periods of time. Excess energy can also be stored in phase-change materials (eutectic salts) that are selected for their characteristic melting points. Eutectic salts absorb significant quantities of energy during their liquid phase and release it during the freezing process. For greenhouse systems, eutectic salts with melting points in the 50-100°F range would be particularly useful.

Controls

While new sensor technology and calibration procedures typically improve the control of the greenhouse environment, additional gains can be realized by developing advanced control strategies that better incorporate economic implications of control actions.
For example, while lowering the greenhouse temperature by a few degrees during a hot summer day may be technically feasible, it may not be economical when the costs associated with dropping the temperature are larger than the return expected from improved crop production and/or quality. This approach requires inputs from all greenhouse system components as well as external influences such as weather, energy prices and marketing.

In order to better understand the energy usage of individual greenhouse system components, energy usage meters can be installed so that the impact of different control strategies can be monitored instantaneously as well as over longer periods of time.

Leave a Reply

One comment on “Learning To Conserve by A.J. Both

  1. Do you have a formula for Eutectic salts that could be stored in 2 gallon jugs stacked along a South facing wall?

More From Structures...

February 15, 2017

Growers Planning to Invest in Structures in 2017

Data from this year’s Greenhouse Grower State of the Industry survey indicates that growers are planning to make major investments in structures and facility upgrades this year.

Read More
NVAC Greenhouse prototype

February 15, 2017

New Greenhouse Cooling System in Development for Hot-Climate Regions

Researchers at McGill University in Quebec have developed an alternative evaporative cooling solution for greenhouses in warm climates, and are now seeking commercial partners.

Read More

February 15, 2017

Registration Open for NGMA Spring Meeting

The annual gathering of the National Greenhouse Manufacturers Association will feature a look at green industry trends, emerging market opportunities, and more.

Read More
Latest Stories

February 15, 2017

Growers Planning to Invest in Structures in 2017

Data from this year’s Greenhouse Grower State of the Industry survey indicates that growers are planning to make major investments in structures and facility upgrades this year.

Read More
NVAC Greenhouse prototype

February 15, 2017

New Greenhouse Cooling System in Development for Hot-Cl…

Researchers at McGill University in Quebec have developed an alternative evaporative cooling solution for greenhouses in warm climates, and are now seeking commercial partners.

Read More

February 15, 2017

Registration Open for NGMA Spring Meeting

The annual gathering of the National Greenhouse Manufacturers Association will feature a look at green industry trends, emerging market opportunities, and more.

Read More
EFTE Film

January 18, 2017

Looking at Glass or Polyethylene for Your New Structure…

Ethylene Tetrafluoroethylene, also known as EFTE, is a fluorine-based material that looks like a standard polyethylene greenhouse film but offers high light transmittance.

Read More
Nadia Sabeh, CEAC

January 18, 2017

Upcoming Seminars to Focus on Managing the Greenhouse E…

The seminars, which will also be accessible online, are presented by the University of Arizona’s Controlled Environment Agriculture Center.

Read More

November 16, 2016

Stay Up To Date On Greenhouse Structures And Materials

eGro, an online resource for greenhouse growers, features a series of video lectures and tutorials on a wide variety of topics, including greenhouse structures and terminology, heating and cooling, and more.

Read More
Dual Atrium Greenhouse (Nexus)

October 12, 2016

Gibraltar Industries Acquires Nexus Corporation

The building manufacturer and distributor strengthens its position in the U.S. greenhouse market, complementing its RBI greenhouse company with the aquisition of Nexus Corp.

Read More
Gotham Greens Atrium Style Greenhouse Chicago

September 14, 2016

How An Energy Audit Of Your Greenhouse Can Save You Mon…

Is your greenhouse utility bill getting you down? Consider an energy audit to evaluate potential energy savings.

Read More
JGS Structure at Vineland

September 14, 2016

Take A Virtual Tour Of Canada’s Vineland Greenhouse Tec…

The one-of-a-kind research greenhouse project was completed by JGS Limited and features 40,000 square feet of horticultural research space.

Read More
Stuppy Greenhouse Manufacturing's Rainbow Super Structure

September 14, 2016

NGMA Contributes Revisions And Updates To Building Code…

The revisions cover the definition of a greenhouse, improved efficiencies in making greenhouse code changes, and more.

Read More
GrowSpan Light Deprivation Greenhouse

August 25, 2016

New Light Deprivation Greenhouses Help With Light Manag…

The GrowSpan light deprivation greenhouse from Growers Supply is outfitted with a blackout system that provides growers with control over the light cycle.

Read More
Cannabis Structure

August 23, 2016

5 Factors To Consider In Your Cannabis Structure

Along with the size and specs of your greenhouse, it's also important to focus on ventilation, light deprivation, benching, irrigation, and odor control.

Read More
Nexus Dual Atrium at Lucas Greenhouses

August 15, 2016

6 Ways Greenhouse Suppliers Are Partnering With Produce…

Greenhouse and equipment manufacturers share how they work with growers to provide customized solutions.

Read More
Cannabis Structure

July 28, 2016

How To Maximize The Efficiency Of Your Cannabis Structu…

The up-front costs of creating your cannabis facility may be high, but at least one expert says making the investment now will be well worth it down the road.

Read More
Floral Greenhouse at Vineland Research Centre

July 20, 2016

Research And Commercialization Unite At The New Vinelan…

The new, pre-scale commercial greenhouse facility at Vineland Research and Innovation Centre in Vineland Station, ON, will help accelerate the commercialization of innovative technologies and products coming out of research.

Read More
Geranium Injured By Ethylene

July 20, 2016

How To Prevent Greenhouse Heating Leaks

Ethylene from malfunctioning greenhouse heaters can lead to crop injury, while carbon monoxide can lead to worker illness. Know the symptoms and how to check greenhouse heaters to avoid these concerns.

Read More
GrowSpan Screen cap

July 18, 2016

Growers Supply Launches GrowSpan Website With New Conte…

The GrowSpan website will encompass the brand’s entire greenhouse structure line, and allows growers to quickly browse GrowSpan’s product offerings based on structure type.

Read More
Lisa Ruggiers, National Greenhouse Manufacturers Association

June 15, 2016

Meet The New Executive Director Of The National Greenho…

Lisa Ruggiers has been active in NGMA for several years, and will work closely with the group’s officers and board of directors.

Read More