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Before we get started, let’s set some ground rules for this article. 

1. I want to believe that everyone wants to do what’s right for the planet as long as they think their business can afford it, so we will not focus on energy efficiency and its impact on sustainability. 

2. In this article I will not post the name of suppliers or the price of the lights. The price of the light will definitely impact people’s decisions and will vary widely based on the volume of lights being purchased and the supplier providing it. 

3. This article is not about light quality or light spectrum. To look for information on spectrum please read this article: Why I Still Believe in Red/Blue LED Grow Lights

4. This article is written with commercial greenhouse produce growers in mind, but we do include a model which shows high output led grow lights running for long hours per day which could imply a greenhouse cannabis crop. 

5. We are fully aware that when you change the amount of energy going into the light as well as the type of electric light (HPS vs LED) one is using, it will have an impact on the climate in the growing/production area. Factors like heat and relative humidity would need to be taken into consideration if one was taking a holistic approach to energy savings on the farm. 

6. All lights have different output (measured in PPF.) In this article we are going to make the assumption that a grower is using the same amount of fixtures per acre regardless of output. For simplicity we are also going to assume that the grower is running the lights for the same amount of time. We are fully aware that this will have an impact on the potential yield of the crop. 

7. All greenhouses can require a different amount of lights per acre to achieve the target light intensities. I am using an average of the amount of lights per acre. Height of the greenhouse, width of the bays, placement of walkways, crop layout, crop density, as well as many other variables will impact the exact number of lights per acre. 

__________

There is a growing amount of discussion around the environmental sustainability of a greenhouse or a vertical farm. Much of this discussion is being driven by two or three big energy hogs inside these production facilities. This includes the grow lights and climate management equipment like heaters and cooling units. 

We all know that LED grow lights are more efficient than the older HPS lights that growers have used for decades, but do we know just exactly how to measure that? And do we understand how that will have a direct impact on not only energy savings but the operational cost at the farm? For those growing in a greenhouse, understanding these numbers during dark winter months can have a huge impact on electricity bills.

3 FOCUS POINTS 

1. Start by understanding the amount of light you need.
Urban Ag News recommends going to websites like Suntracker or the ESRI DLI maps site. These websites allow anyone to determine the historical DLI monthly averages for their individual locations. For this example I am going to use the area where my grandparents farm is located in southwestern Michigan. As one can see this is an area of the United States that has very dark winters. 

2. Work with a trusted advisor or extension specialist to determine the amount of hours your crop needs to grow consistently year round. Remember not all crops have the same light requirements and some crops have very specific photoperiods which can determine the amount of hours one can light their crops. Use all of this information to see when you will need supplemental light and how much light you will need to supplement with. 

For this example I am going to use 1 acre of greenhouse tomatoes in a glass greenhouse located in southwestern Michigan.

3. Now let’s calculate how much it’s going to cost you to run the grow lights for the estimated hours you and your advisor determined were needed per year to get the desired yields. 

• a) To provide a baseline, we started with traditional 1000w HPS lights which are highlighted in yellow. 
• b) Then we chose six different LED grow light fixtures. Because the light spectrum has an impact on how efficiently the lights run, we chose three broad spectrum fixtures and three that are red and blue only. 
• c) Since HPS is the baseline, the final column labeled “savings” shows how much the total savings per year one would achieve when replacing traditional HPS with the latest LED grow light technology. 
• d) We made a few important assumptions in this example. First, the cost per kwh is around the USA national average of $0.09/kwh. Second, the same amount of grow lights would be used even though there would be some relative differences in umols/m²/s measurements for two of the samples. We decided not to change them because that would have an impact on uniformity (the even spread of the light over one’s entire crop) and associated capital cost not addressed in this article.

IMPORTANT NOTES! 
It’s important to remember the 7 assumptions made at the beginning of this article and that lights are not equal. This chart only compares ppf (output) and w (watts). We elected to account for the difference in output by changing the amount of hours we estimated you would need to run the lights. Another way to look at this would be to remember the Golden Rule of Light in which 1% increase in light is equal to 1% increase in yield. 

Running these simple calculations will show you why you need to look at energy efficient lighting and in general the importance of researching energy efficient equipment in general. What these calculations do not show is the quality of some fixtures over others. Buyers must always be aware of the value of warranties, ease of returns, durability and quality of product plus accuracy of your vendor to create detailed information on the best way to use and install fixtures. We understand that this topic is intimidating for most, but this is a major purchase for your farm. Make sure to take the time to learn the math and do your homework before purchasing. 

Diving into these calculations will also highlight how much energy will be required to grow a wide variety of crops consistently with uniformed yields year round in climates with low light. Hopefully in articles to come we can discuss what this means for our environment and how we might develop additional ways to lower that ecological footprint. 

For help in calculating the energy efficiency of grow lights you are considering, please email us and we will connect you with professionals capable of helping you make an informed decision.

Chris Higgins is the founder of Urban Ag News, as well as General Manager and co-Owner of Hort Americas, LLC a wholesale supply company focused on all aspects of the horticultural industries. With over 20 years of commercial horticulture industry experience, Chris is dedicated to the horticulture and niche agriculture industries and is inspired by the current opportunities for continued innovation in the field of controlled environment agriculture. Message him here.

Simple answer, those with the most passion and perseverance.

As the controlled environment agriculture industry we spend a significant amount of time discussing how we are going to improve our communities, the environment, the farming experience and the quality of food we eat. By themselves these are major commitments. Together they are an enormous commitment. This got me thinking about a simple question, “who should be the leaders of this proposed revolution?” In this post I am going to discuss how we can learn from another industry that is historically conservative as well as providing three focal points I think we should concentrate on.

To find an answer, I started to think about other interests in my life. For those that know me well you know that I love being outside. (For those that don’t know me, hold on you are about to get some insight.) I started to think about my interest in fly fishing and I started to pay close attention to the challenges this niche industry is also experiencing.

In order to explain this better, let me “paint” a picture for you. Rarely, once a year (if I am lucky), I get to travel to one of my favorite places with one no more than two people on a remote saltwater flat. A saltwater flat is any area of shallow water with a relatively even bottom. You can find flats in freshwater, but for me I dream of a remote quiet flat with no people and no access to technology. The most iconic place nearest me are the excotic sands of the Bahamas. (See opening photo.) I am not necessarily there to “catch” a fish, I am more there to capture the experience. The beautiful and hopefully untouched and unpolluted gin clear ocean water provides me a feeling that has been unmatched in my travel. The colors of amazing sunset or dramatic sunrise (to me) are more valuable than the finest piece of art. The wildlife exist in a volume that one never gets a chance to experience in the majority of the USA. The pinnacle, if I am lucky, the chance to get to walk up on a tailing fish. I then have a choice, I can choose to simply watch or I can choose to grab my fly rod, a hook wrapped in some twine and feathers and then play a game of trickery with a very formidable competitor. Either way, my the perfect day has been had.

For those of us who live in the United States, one place you can still have this amazing outdoor experience of chasing a tailing fish is Florida. Luckily for me I have family in Florida, but the experience in Florida is getting more difficult to come by. The opportunity to capitalize on agriculture, tourism and other business has put the Florida coast in the state of constant development. With development you have increased pollution and a growing amount of people putting pressure on a limited resource. Development also means more and more fishermen, many of whom do not share my values of protecting the resource and the surrounding environment which if done correctly allows the many generations still to come the opportunity to enjoy this highly unique experience. Let me be clear, I do not believe in limiting access regardless of whether I disagree with their opinions. I think we should all have access to our nation’s natural resources regardless of one’s financial or political position. So what’s the difference between me and those other outdoorsmen and outdoorswomen? What’s their focus? Normally its land as many fish as possible, kill as many fish as the law will allow (because most everyone I meet does follow the local regulations), get a photo, share on Instagram and think nothing of the trail of trash and destruction they leave behind. It is now a fact that this approach is not sustainable if we want everyone to continue to have access.

Now let’s remember that there is a complete, complex industry that makes money off trying to provide me with this experience– airlines that get me there, the hotels that keep me there, the guides that take me there or retailers that sell me all the necessities I “must have” to be there. These companies and the individuals they employ need these shared resources to continue to make a living, pay taxes and support their families.

And this is where the talk gets oddly political. Not all of those heavily invested in making these experiences possible agree on the best way of protecting these resources.Heck, not all of those individuals even agree that these resources need to be protected.

This leads me back to the basic question, “who’s responsible” for protecting these precious resources?

I started digging deeper into the outdoors industry to see what was actually happening. For those not interested in outdoor activities, it is easy to think that hunters and fishermen/women only really care about going into the wilderness to kill stuff. I realized quickly that within the industry there is a clear difference between a hunter, a fisherman and an outdoorsman. And it’s interesting to see that more and more the outdoorsmen/women who are leading the fight to protect the environments are the same ones that not only cherish it but use it to make a living. They are changing the narrative by encouraging people not to be focused on killing as many fish as they can catch. They are building platforms like Captains for Clean Waters that allow your voice to support science-based solutions and empower your dollar to fight for water quality and hold elected officials accountable. They are better educating themselves by creating entities like Bone and Tarpon Trust to support fisheries through collecting data by using science-based methods supported through collaborations with institutes and governments.

Most importantly I noticed that these individuals are also by far the most passionate about their careers, their hobbies and the natural resources. They are motivated because they see the importance of making change now. They are political, but not in the way you would think (I am still trying to figure this one out so I will hold off on additional comments.) They are motivated by money (this is their living), but the money is not directly derived from the actions they are taking to create change. They have convinced their industries biggest personalities to take a stance while promoting science backed solutions in their most popular venues (tv shows, podcasts, movies and retailers.) Most interesting to me they have convinced these personalities to do this even though it might go against the beliefs of their typical customer base. They realize that offending their customer base is not as important as protecting the resources that allow them to actually have a client base.

Now let’s get back to one of my earlier questions, “who should be the leaders of these changes in our industry?” I think we can learn from other industries by saying, that those whom are most passionate should be our leaders and we as an industry need to find ways to work together to give those passionate individuals a platform that will help to attract new talent to our industry and better educate those individuals interested in our industry or the consumer eating the produce we so proudly grow.

We need to remember that we don’t need to solve every problem, because that’s not realistic. We need to know that if we all work to solve small manageable problems, collectively we will solve big problems. We need to remember that it’s important to encourage those individuals tackling these problems as they will be the ones that create opportunities for all of us.

So what problems can we solve as the controlled environment agriculture industry?

1. Education: The environmental impact that occurs as farmers feed the world. 

We have all read, watched or heard the statistics on how “bad” traditional farming is for the environment. I for one think it’s unfair to put this all on the farmer, even if the facts support much of the rhetoric. It’s unfair because of economics. Traditional farmers do an amazing job of providing “us” with inexpensive food options because that’s what “we” as the consumer have asked them to grow. This creates a big problem for many farmers I know who spend a significant amount of time contemplating how to best steward their land while producing enough yield to pay the bills. We are asking much of these individuals and their relatively small family business.

REMEMBER:  FARMING IS A BUSINESS.

This is our opportunity to support voices that educate. We need to encourage voices that can show or present positive environmental outcomes for the future of farming. One which allows the farmers to become excited for their future and that of their families. For certain crops and in certain geographies, controlled environment agriculture practices can allow farmers solutions to problems like nitrogen run-off, high pesticide usage and inefficient water use. This technology will also allow the farm to become more labor efficient while extending their selling seasons. Success will be based on how well we take the science based data coming out of universities like Wageningen, Ohio State and North Carolina State and then turn it into something that the farming community, local government and ultimately the consumer can use to change the way they grow and purchase food.

Warning:  Our industry needs to be careful that we don’t over promise while at the same time focus on the positive impact we can make while not creating other possibly larger problems.

2. The Platform: Rebuilding of blighted rural and urban communities.

Not historically an “ag” or “hort” conversation, community development is becoming a popular part of many new ventures’ pitch decks. It’s obvious that local politicians in certain areas are interested in this concept, but the reality of controlled environment agriculture (CEA) businesses creating many jobs with good salaries is still yet to be proven.

The current interest, global attention and spotlight may well mean it’s our best opportunity at creating a platform with real stakeholders financially committed to helping us drive opportunity forward.

In order to do this, we will need to open up and think like a community. We will need to:

• Create platforms that support developing an industry within an industry.
• We will need to educate innovators with the problems that truly need to be solved.
• We will need to think about how we work together to build up a variety of businesses that have the same focus and shared missions.
• We will need to think creatively about what business makes sense in what settings.
• We will need to think about investing in our industry to create ways of educating the next generation of workers and leaders.
• We will need to lobby to get the support of both the financial and political communities.
• We will need to focus.

Most importantly we need to understand it’s not our businesses that will alone strengthen the community; it’s the creation of opportunities that lift up families giving them the economic means to further their education, improve their diets, become property owners and invest in their own futures.

“Today, our very survival depends on our ability to stay awake, to adjust to new ideas, to remain vigilant and to face the challenge of change.”
– Martin Luther King.

3. Changing the Narrative: Health and wellness of individuals in our communities.

For most, the food we eat becomes the center of our social universe.  Think about it.  Where do people gather when they visit your house?  The kitchen.  When you think about some of your best memories what is one of the things you remember?  The food and drink you enjoyed.  When you need to feel at home, what do you turn to?  Comfort food.

That’s why for me, this is a no brainer.  We grow fresh produce.  We create the fuel people put in their bodies.  We have an opportunity to be part of the memories the consumer makes.  We need to be proud of this.  We need to motivate consumers by educating them to understand why fresh produce is an important component of creating a long healthy happy life filled with good memories surrounded by family, friends and happiness.  

We need to promote diets high in fresh vegetables and produce which means challenging the animal protein industry for space on plates.  We need to work with chefs to make sure our product is the centerpiece and not a side dish.  We need to promote these diets as fashionable and desirable.  Not encouraging the stereotypes of meatless diets, but the benefits and enjoyment that comes from a plant based lifestyle with animal proteins as the side dish.  We need to look at our own homes and look at the dollars we are spending on our plates.  We need to ensure that we are supporting those that support us.

Finally, the exact solutions will not be provided by one person.  My colleagues and I continue to work to do what we can to play a small role in improving the environment around us.  But, for us to ultimately succeed we will need to identify multiple individuals that have grit, then support them and their passion to solve specific problems.  Join me in starting this journey and remember its most important to start now as its only getting harder and harder to protect what we love.

Indoor Ag Science Café is an outreach program of our project OptimIA, funded by USDA SCRI grant program. The café forums are designed to serve as precompetitive communication platform among scientists and indoor farming professionals. The Café presentations are available from our YouTube channel: https://www.youtube.com/playlist?list=PLjwIeYlKrzH_uppaf2SwMIg4JyGb7LRXC   

Contact Chieri Kubota at the Ohio State University (Kubota.10@osu.edu) to be a Café member to participate. 

Miami, Fl., October – This month’s Sustainability & Digitalization Leaders forum is the exclusive, comprehensive conversation every thought leader in agtech should be a part of. The SDL agenda demonstrates critical awareness of the most relevant sustainability issues across the agtech landscape, from regenerative agriculture to carbon sequestration and soil health; responsibly investing in the latest innovations to ensuring a traceable, transparent food system for consumers. 

The Miami forum, 22-24 October, also sees the introduction of breakout workshops tackling issues in a collaborative, discussion-based format led by industry seniors. Delegates will be invited to drop in on the 30-minute sessions and engage with topics such as global warming in relation to food systems, and corporate strategy for urban agriculture. 

Alongside SDL speakers including Wells Fargo, Rabobank, AeroFarms and Microsoft, the next round of international thought leaders have been confirmed: 

• Chris Higgins – General Manager, Hort Americas
• Claire Kinlaw – Director Innovation & Commercialization, Donald Danforth Plant Science Center
• Andy Knepp – VP, Environmental Strategy & Industry Activation, Bayer Crop Science
• Cristina Rohr – Vice President, S2G Ventures
• Kenneth Zuckerberg – Senior Partner, Carlan Advisors
• Wayne Honeycutt – President & CEO, Soil Health Institute
• Pipa Elias – Director of Agriculture North America, The Nature Conservancy
• Erica Riel-Carden – Principal, Global Capital Markets
• Paco Vélez – President & CEO, Feeding South Florida
• Kasper Vesth – General Manager USA, The Meatless Farm Co. 
• Chiara Cecchini – Executive Director, Future Food Americas 

For a full list of speakers visit: https://www.sdleaders.com/speakers 

Occupancy for the forum is near capacity and organizers urge attendees to secure their ticket before registration closes. 

For more information on SDL and to purchase tickets visit: https://www.sdleaders.com/ 

About Sustainability & Digitalization Leaders SDL is a series of events that address our planet’s most pressing issues, bringing together the decision-makers who directly impact global change and can implement the necessary strategies to move the conversation forward. 

A core advisory board oversees and advises on partnerships. For enquiries please email lyndsey@sdleaders.com. About Keynote Hosting international events since 2012 across Europe, North America and the Middle East, Keynote has curated forums for emerging technology industries, launching high profile fintech projects and acting as a platform to raise significant funds, connecting and enabling companies to reach their potential. For more information about Keynote’s upcoming conferences visit www.keynote.ae

Press Release, 08/05/2019 (Miami, Fl.) – SDL, an independently organized event series, announced the second round of speakers to conduct presentations during the inaugural event this October 22-24, 2019, featuring CEOs, directors and other pioneering figures in sustainability strategy and agtech. 

The forum will take place inside the James L Knight Center in Miami, Florida. Featured topics include: long term sustainability across our supply chain sectors; soil health and its climate impact; the role of ground level farmers in a fast moving, innovative agricultural future. 

SDL introduces new drop-in roundtables for the October Miami forum. The goal for these first come, first serve conversations is to encourage attendees to drop into a free-thinking conversation, delving into new ideas and cooperative solutions. Tables will be scheduled pre-event and each based around a headline topic, curated and led by leaders in the AgTech community. Topics and table hosts will be announced in the coming weeks. 

Alongside SDL’s already confirmed speakers including MARS, Airbnb and Microsoft, a second round of international thought-leaders have been confirmed: 

Ken Russell – Miami Commissioner
Arama Kukutai – Partner, Finistere Ventures
Megan DeYoung – Strategic Partnerships Consultant, Aerofarms
Miku Jha – CEO, AgShift
Sara Eckhouse – Executive Director, FoodShot Global
Amy Yoder – CEO, Anuvia Plant Nutrients
Chris Higgins – Co-owner, Hort Americas
Anna Rath – CEO, Vestaron Corporation 

For a full list of speakers visit: https://www.sdleaders.com/speakers 

Occupancy for the event is limited and organizers urge attendees to secure their registration early. 

For more information on SDL or to purchase tickets visit: https://www.sdleaders.com/ 

About Sustainability & Digitalization Leaders SDL is a program of events that address our planet’s most pressing issues, bringing together the decision makers who directly impact global change and can implement the necessary strategies to move the conversation forward. 

A core advisory board will oversee and advise on partnerships. For enquiries please email lyndsey@sdleaders.com. 

About Keynote Hosting international events since 2012 across Europe, North America and the Middle East, Keynote has curated forums for emerging technology industries, launching high profile fintech projects and acting as a platform to raise significant funds, connecting and enabling companies to reach their potential. For more information about Keynote’s upcoming conferences visit www.keynote.ae 

For media partnership enquiries: amandah@sdleaders.com For partner and sponsorship enquiries: amy@sdleaders.com 

Press Release – Manitowoc, WI – Dramm is pleased to announce that they are partnering with Vifra, the specialists in humidity management, to offer their solutions to North American customers. Vifra focuses on helping growers optimize their greenhouse humidity. Founded in 1994 by Vincenzo Russo in Rome, Italy, Vifra produces high quality systems designed for easy maintenance and long life. Dramm is pleased to offer Vifra’s high-pressure fog and dehumidification systems to North American growers to help them optimize their growing climates. Vifra’s systems work to increase or decrease humidity as conditions demand. Often, these systems can be used in coordination with each other to adjust humidity levels throughout the day, allowing for the right climate for any crop at any time of day. Vifra offers High Pressure Fog Systems that operate between 1,000 and 1,800 psi, depending on the existing humidity and crop needs. These high-quality systems utilize specialized nozzles and stainless-steel construction. Specially designed fittings and connections prevent the need for guide wires make installation easy. Vifra systems use custom pumps, running at lower speeds, to reduce wear and ease maintenance. Vifra Dehumidification Systems utilize a decentralized approach to removing excess moisture from the greenhouse atmosphere. Dehumidification systems can aide in transpiration and reduce energy usage caused by reheating the greenhouse air during cold weather venting. By positioning the dehumidification units throughout the greenhouse, a more uniform result is achieved.

Dramm is pleased to work with Vifra to help North American growers manage their humidity. For more information, visit www.dramm.com or contact us at 800-258-0848. The Dramm Corporation has produced quality products and solutions for growers for over 75 years. Founded in 1941 with the invention of the 400AL Waterbreaker, the Dramm Corporation continues to innovate to help its customers flourish. Dramm manufactures over 35 different sprayers for indoor agriculture, offering a wide variety of choices for every spraying need.

Sessions will focus on climate, insect management and pollinators, biostimulants and much more.

Speakers include Dr. Annette Wszelaki from Tennessee, Dr. Lori Hoagland from Purdue and Dr. Matt Ruark from Univ. of Wisconsin, and Purdue’s own team of experts.

If you are interested, please visit https://www.inhortcongress.org/

Daily light integral (DLI) is the amount of photosynthetically active radiation (PAR) received each day as a function of light intensity and duration. DLI maps display the ambient light delivered daily during each month across the entire United States. The original maps released in 2002 were researched and developed by Jim Faust at Clemson University and Joanne Logan at the University of Tennessee.

These researchers developed a series of monthly DLI maps to provide a tool for horticulturists to estimate the potential growth and flowering responses for various plants throughout the year. At least 40 research articles studying plant responses to DLI have been published since the original DLI maps were released. Most of this research focused on greenhouse ornamental production.

The original DLI maps were based on solar radiation data from 239 sites recorded from 1961 to 1990. New maps were created from an updated database that included data from 1998 to 2009. This updated information provides higher resolution data modeled from satellite images of cloud cover. The new maps provide more geographically precise data reflecting recent weather patterns.

Milwaukee, WI, USA – Desert Aire, a Milwaukee-based manufacturer of commercial and industrial humidity and climate control systems, has published a new technical resource that explains how carefully defining grow room Vapor Pressure Deficits can produce maximum yields and have favorable impacts on the capital and operational costs of HVAC systems.

“Application Note 28 – Vapor Pressure Deficit and HVAC System Design” is a 6-page publication that helps growers, consulting-specifying engineers and mechanical contractors understand the impact of Vapor Pressure Deficit (VPD) on plant growth processes, protecting crops and maximizing yields.

Vapor Pressure Deficit is a metric that indicates the evapotranspiration potential of grow rooms based on current temperatures and humidity levels. The expressed value is the deficit or differential between the pressure exerted by the moisture at a specific room condition and the pressure at the surfaces of plant leaves.

Using explanatory text as well as color figures, charts and tables, Application Note 28 provides readers with a thorough briefing on the control of indoor grow environments through the management of VPDs. Understanding the fundamental impact of VPDs and temperatures on growth and yield is an important starting point for the planning of indoor grow facilities. The Application Note also outlines how strategically selecting grow room VPDs favorably impacts the sizing of environmental control equipment and associated costs.

Application Note 28 is the latest in a series of technical resources from Desert Aire intended to inform growers, consulting-specifying engineers and mechanical contractors about grow room issues and HVAC equipment strategies. Previous documents in the series included: Application Note 27 – HVAC-Systems and Grow-Room Energy Usage; Application Note 26 – Grow Room Environmental Control; and Application Note 25 – Grow Room Load Determination.

The publication “Application Note 28 – Vapor Pressure Deficit and HVAC System Design” is available for download as a PDF document at desert-aire.com. To receive a printed copy of the publication, email sales@desert-aire.com.

Desert Aire is a Milwaukee-based manufacturer of commercial and industrial dehumidification systems, environmental control systems and dedicated outdoor air systems. Desert Aire systems provide healthy and comfortable indoor environments while saving energy in a variety of settings including grow rooms; commercial greenhouses; indoor pool facilities; indoor water parks; ice rinks; schools and universities; rec and fitness centers; office and retail buildings; and water treatment plants. Desert Aire is a subsidiary of Multistack, LLC. Desert Aire’s main office is located at N120 W18485 Freistadt Road, Germantown, WI, 53022, USA. Telephone (262) 946-7400; Fax: (262) 946-7401; Internet: Desert-Aire.com.

Trying to produce vegetables in hot, humid conditions can be difficult for controlled environment growers whether growing in a greenhouse or a warehouse.

“The challenges of greenhouse growing in Ohio and the Midwest are different than the challenges faced by growers in Arizona,” said Ohio State University horticulture professor Chieri Kubota. Kubota, who joined the faculty at Ohio State this past June will continue the controlled environment agriculture research she was doing while at the University of Arizona.

“Some people think I’m an expert at dealing with heat stress because I was doing my research in an Arizona greenhouse,” she said. “But in Arizona growers don’t really have to worry about the heat inside a greenhouse if they are using an evaporative cooling system to lower the temperature. In Arizona the outside temperature can be 110ºF, but the temperature in the greenhouse can be lowered to 75ºF-80ºF (25ºC-27ºC) as long as the air is dry enough and water is available. In Arizona the dryness can be a challenge, causing tip burn on sensitive crops such as lettuce and strawberry.

“I really didn’t have to deal with heat stress much in Arizona. But there are other parts of the country like the Midwest and East Coast that have to deal with hot, humid summer conditions and very cold winters. I would like to work on those issues and develop technologies, including climate control strategies that can mitigate the issues of growing crops year-round. In Ohio and the Midwest summer heat stress is a major issue for crops causing all kinds of physiological disorders including incomplete pollination and fruit ripening disorders. During the winter, heating and humidity can also be an issue. There is also an issue with low light levels so supplemental lighting is more important.”

Because of the limited optimum growing season in greenhouses in the Midwest, Kubota said using indoor productions systems makes more sense compared to Arizona.

“In this part of the country it is very difficult to maintain the optimum temperature range year round,” she said. “And because of the increased interest in vertical farming, I expect to put more effort in warehouse production systems, including the use of LED lighting.”

Improving vegetable grafting

Some of the projects Kubota started at the University of Arizona that she will continue to work on are vegetable grafting and hydroponic strawberry production. She is a member of a research team lead by North Carolina State University plant pathologist Frank Louws that is working on vegetable grafting.

“I am continuing my research on improving grafting methods and the handling of grafted plants so that they can be shipped long distances,” Kubota said. “I am also creating a simple tool for growers to schedule grafted plant production. Having the grafted plants ready at exactly the same size is always a challenge for growers. The research group is working to develop a simple plant growth model based on environmental conditions to predict how many days are needed to finish a grafted crop.”

Kubota said the grafting research team is looking at a variety of plants, including tomato, watermelon, cucumber, eggplant, pepper and muskmelon.

“Growers are commercially producing grafted tomato and watermelon plants, but there are many more crops that can use grafting technology to reduce loss from soil-borne diseases and to increase yields. My program is looking at all of these potential crops.”

Kubota said the grafting research also has application to greenhouse crops.

“The grafting technology was originally developed for soil-based production, but greenhouse vegetable growers discovered that even though they are doing soilless production, using grafted plants can increase crop yields,” she said. “In North America, greenhouse growers were the first group who started using grafting technology. The field growers are now more interested since they have fewer means to control disease. In terms of potential market, field production in the U.S. is much larger in terms of number of plants.

“Currently tomato accounts for the majority of grafted plants in greenhouses. Increased tomato yields have been the driver for greenhouse growers to use grafted plants. Some greenhouse growers have been trialing grafted cucumbers and some research has shown that grafted eggplants can increase yields.”

Improving strawberry production

Kubota who has been working on greenhouse strawberry production for nine years will continue working on this crop with an interest in the use of LEDs.

“Strawberry fruit production is not as productive as leafy greens or tomatoes in terms of dollars of return relative to the input of light,” she said. “I’m interested in studying the increase in yields relative to the increase in light. What is the dollar value of that increase of yield by adding for example, 1 mole of light? Unless there is an improvement in lighting technology, it may not make sense to grow strawberries under supplemental lighting.

“I would like to come up with a smart lighting system to reduce the lighting cost based on the understanding of strawberry physiology and how plants are grown in a greenhouse. I think we could reduce lighting energy use and costs quite a bit by doing that. Strawberries are physiologically unique in terms of light saturation and also in terms of the sink-and-source relationship of how much sugar can be translocated from the leaves so that the photosynthetic rate can be maximized.”

Developing new crops

Another area that Kubota would like to expand for CEA production is the development of new crops.

“Controlled environment growers whether they are growing in greenhouses or warehouses need to diversify and increase the number of crops they are producing,” she said. “Although I don’t have any new crop projects coming up, I am particularly interested in small fruits. Since Ohio and the Midwest have a cold climate, there may be an opportunity to do more with small fruit crops like raspberries, blueberries, blackberries and other berry crops for greenhouse production.”

Kubota is also interested in revisiting the study of spinach production in greenhouse and warehouses.

“Controlled environment growers seem to have a particularly difficult time managing diseases including Pythium on spinach,” she said. “I am interested in determining if there is a practical way to manage these diseases. Cornell University researchers had previously done a lot of studies on this issue years ago. I wanted to see what the difference was between the successful hydroponic growing of spinach in Asia and other countries and why U.S. growers can’t do that too.”

Expanding professional training, research programs

As part of her extension efforts at Ohio State, Kubota wants to expand the opportunities for growers to receive professional training.

“I want this training to go beyond Ohio and to go nationwide and even international,” she said. “I’m interested in training professionals with online courses and other programs at a reasonable cost.

“The heart of the horticulture industry is in this part of the country. There are many different types of growers, supporting vendors and technology providers here. They are well connected.”

Kubota said at the University of Arizona research in the plant science department was focused more on basic science such as how a particular gene functions in plants, but not necessarily horticultural plants.

“Here at Ohio State I am in the horticulture and crop science department so the other faculty members understand what horticulture is,” she said. “There are a number of people here working on controlled environment agriculture including horticulture, which covers floriculture, hydroponics and high tunnels, and ag engineering, entomology, plant pathology and food safety. There is a complete set of researchers and extension specialists who can work on a variety of controlled environment agriculture issues related to horticulture crops. This makes it advantageous for not only developing research projects together, but also professional training for commercial growers.”

For more: Chieri Kubota, The Ohio State University, Department of Horticulture and Crop Science, kubota.10@osu.edu; http://u.osu.edu/cepptlab; https://hcs.osu.edu/our-people/dr-chieri-kubota; https://www.facebook.com/CEPPTLAB.

This article is property of Urban Ag News and was written by David Kuack, a freelance writer from Fort Worth, TX.

Lucayan Tropical Produce has been growing greenhouse vegetables in The Bahamas for 12 years, but it has taken some adjustments to find the best crops to grow on an island in paradise.

Since Lucayan Tropical Produce Ltd. began producing greenhouse vegetables in 2004, the company has experienced three major hurricanes, including Hurricane Matthew, this past October. Matthew, which was designated a Category 5 hurricane, had sustained winds as high as 160 mph. The company, which is located on New Providence Island in The Bahamas, operates a 5.5-acre Dalsem glass greenhouse producing cucumbers, lettuce and leafy greens.

While residents and tourists may consider the island to be “paradise,” the climate, cost of electricity and availability of fresh water can make for challenging growing conditions.

“Unlike traditional greenhouse operations we began the company with a concept that included many different types of crops in the same greenhouse,” said company president Cameron Symonette. “We felt that what we gave up on efficiency we would gain back on price. Being on an island, the prices of highly perishable items are generally quite high. We started with five different tomato varieties and three different colored bell peppers in the initial phase of the operation. We had two separate irrigation systems across six irrigation zones. That set up failed to work for us for a number of reasons; mostly because of the inherent difficulty of managing so many different types of crops from both a production perspective and from a packaging logistics/distribution perspective.

“The peppers weren’t a problem, but for the tomatoes, having different varieties with different requirements meant having to change the irrigation strategies. That was a challenge in our environment with the amount of solar radiation and the temperatures. The monthly average differences between day and night temperatures on a daily basis are not really significant for over 50 percent of the year causing challenges with fruit set and germination. That is the number one reason why we changed our approach. Currently we are producing only cucumbers in the greenhouse.”

Best crops for the climate, greenhouse design

While Lucayan Tropical Produce’s core crop is cucumbers, the company is also producing lettuces and leafy greens.

“We chose to focus on cucumbers for two reasons,” said Symonette. “One, because in our environment we are unable to achieve the yield per square meter that is required for tomato production to be commercially viable. In our environment of a high relative humidity and plenty of sunlight, cucumbers grow well. It was just a better crop for us to grow.

“The second reason is the time between when we plant and harvest the cucumbers is much quicker than it is with tomatoes. Any issues that we might have related to a crop failure or if we need to replace old plants, the time to do that is much faster with cucumbers.”

Lucayan Tropical Produce is also producing a variety of lettuces, leafy greens and herbs that it sells domestically.

“Summer temperatures definitely limit the leafy greens we can grow,” Symonette said. “We find the most success growing leafy greens from the beginning of October until the end of May. We currently grow on ebb-and-flow tables, which were originally designed as a propagation area for the crops in the main greenhouse. We didn’t have the luxury of being able to buy our starter seedlings from another local grower so we built the propagation area so we could do it ourselves. Over the last two years we have been running trials with a NFT and a pond system to determine what is the best system for trying to extend our growing season into the summer months.”

Symonette said the company is also interested in building a controlled environment facility to produce lettuces and leafy greens.

“We want to expand our lettuce and leafy greens production during the first quarter of 2017,” he said. “That expansion will take the form of a temperature controlled system with artificial lights. It doesn’t mean vertical growing, but it does mean growing under lights. That system would be built inside our packing area.”

The company distributes its cucumbers, lettuces and leafy greens through two wholesalers.

“Our intention is to sell as much of our product domestically as we can before we export,” Symonette said. “The lettuce and leafy greens are only sold domestically through Bahamas Food Services. Since we’ve started to export the cucumbers, we have been working with Sun Produce in Florida that distributes our product in the United States and Caribbean.

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“The market acceptance of our products has been phenomenal. The taste and shelf life are great. We’re focused on supplementing what we grow in the greenhouses with some growing under lights to add product mixes that we couldn’t grow in our environment that would sell well in our market.”

Making improvements

The greenhouse was initially designed with two 250,000-gallon rain water holding tanks so water that falls on the greenhouse roof is collected and used for irrigation.

“Because of the monthly rainfall patterns, we also have a reverse osmosis system installed in the greenhouse that we only use during a six-week window during the year,” Symonette said. “We do not have access to fresh water, which is a problem with agriculture in general in the country. High property prices and no access to water limit potential growing operations.”

The company has made significant improvements to its irrigation systems over the last 10 years.

“We recently upgraded our water purification system to a combination of ozone and UV filtration which is really working,” Symonette said. “It leads to higher oxygen levels, which in turn leads to better root health.

“The second improvement is in employee training, which is a critical component. Because we have been in business for over 10 years, we have team members who are more experienced and have learned the systems we have developed, which has led to a more efficient operation than when we started.”

Symonette said the company looked extensively at improving climate management with its current greenhouse but determined it was not possible to improve the climate because the cost of electricity is cost prohibitive.

“Any technological solution in an open environment would not increase yields enough to justify the increased costs of electricity,” he said. “The greatest potential opportunity is in an energy-efficient closed growing system for producing leafy greens under lights where the temperature and humidity can be controlled.

“We also have a trial solar panel installation at our facility and are seriously considering expanding that to a size that would run the daytime requirements of the operation.”

Future expansion considerations

Symonette said the biggest issue to maintaining the proper greenhouse climate is the similarity between night and day temperatures.

“That would be the predominant factor, which basically influences what we are able to grow,” he said. “Looking back the greenhouse design focused on protecting the structure from hurricane damage, but ultimately negatively impacted airflow. As we expand greenhouse production we will think about using our growing experience to make some decisions. With the benefit of hindsight and experience, we will make some different choices that will generate greater airflow.”

Symonette said every time the company has experienced a major weather event, such as a hurricane, changes have been made in operations.

“We think about what happened and why it happened and put some thought into how we can prepare in a more sensible way,” he said. “Each storm has brought different learning experiences, but none of those major hurricanes or other weather events has caused us to change the construction.”

Symonette said the company will look at expanding its greenhouse growing area next year.

“We’re not sure what form that will take,” he said. “There are no government restrictions on making that expansion. The government is very supportive of us and encourages agricultural participation.”

For more: Lucayan Tropical Produce,
(242) 377-0125; info@ lucayantropical.com.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

Although it may be difficult to create the perfect greenhouse climate for growing plants, there are variables growers can control to maximize plant growth.

Regardless of the type of crop being grown in a greenhouse, the climate a grower is trying to achieve requires controlling the same variables.

“Greenhouse growers are trying to control temperature, humidity, light level, carbon dioxide, and in some instances, airflow and air distribution,” said mechanical and agricultural engineer Dr. Nadia Sabeh, founder of Dr. Greenhouse. “Depending on the crop, these variables have different set points. They also might have different acceptable maximum and minimum ranges or levels.

“Depending on the crop, these variables can be changed during different times of the day. For instance, a tomato crop wants a daily average temperature around 72ºF. If the plants experience high temperatures during the day, if the temperature is able to be cooled down during the night, as long as the average temperature is 72ºF, the tomato plants are happy. For lettuce, a grower may not be able to manipulate the day or night temperature to make up for exceeding the maximum temperature that occurs during the day or night. That’s one way these crops differ.”

Sabeh said when it comes to controlling the greenhouse environment growers usually focus first on temperature.

“The first line of defense against warm temperatures is not shading,” she said. “Growers are trying to maximize as much light into the greenhouse as possible. As soon as a shade curtain is closed the solar input is reduced. The first line of defense for cooling a greenhouse is ventilation, either natural or mechanical.

“If ventilation can’t achieve the temperature a growers needs, then some form of cooling is added. Typically cooling is done through evaporative cooling. This could be wet pads and a fan system, high pressure fog or a low pressure misting system in combination with mechanical and natural ventilation. If that doesn’t work, then a shade curtain can be pulled. A shade curtain is usually only drawn for two to four hours during the day. It’s pulled during the peak solar heat gain period. A shade curtain can cut the temperature by 2ºF-4ºF.”

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The challenge of reducing humidity

Sabeh said between controlling the greenhouse temperature and humidity, humidity is the more challenging variable, especially if it is for dehumidification.

“If a grower is trying to remove moisture from the greenhouse, that presents a lot of challenges,” she said. “The standard method of removing moisture from the greenhouse is through ventilation. But that assumes that the moisture level or the humidity outside the greenhouse is lower than it is inside the greenhouse.

“If a grower is looking to increase the humidity or humidification, for a greenhouse located in the southwest U.S. where it is very dry, moisture can be added to the greenhouse using evaporative cooling. Another benefit of evaporative cooling is a reduction in the temperature that cools the greenhouse temperature. Evaporative cooling works very well in a dry climate to do both of those things.”

Sabeh said growers in the Midwest and Southeast can experience more challenging climates because they have a high heat solar gain like growers in the Southwest experience, but they also have high humidity levels requiring them to ventilate.

“The climates in the Midwest and Southeast make it very challenging to grow plants in a greenhouse because of the humidity,” Sabeh said. “The only line of defense for growing plants in that kind of climate is ventilation. Growers want to exchange as much air as possible with the outside to remove moisture and solar heat gain during the day. Typically that is inadequate. If the outside temperature is 90ºF and the relative humidity is 90 percent, growers certainly don’t want those conditions in their greenhouses.

“If the temperature and humidity are high, growers don’t have the opportunity to use evaporative cooling because they can’t reduce the temperature enough,” she said. “They can shade the greenhouses, but that only lowers the temperature by 2ºF-4ºF from outside conditions. If it is 90ºF and 90 percent humidity, pulling shade results in 86ºF and 90 percent humidity, and that is not going to provide the vapor pressure deficit a grower is trying to achieve.”

Sabeh said growers might consider closing up their greenhouses to avoid bringing in hot, moist air, but that creates additional challenges.

“Closing the greenhouse can cause the greenhouse to heat up from the sun plus the plants are releasing moisture resulting in the greenhouse just getting hotter,” she said. “So far I haven’t really seen anyone come up with a very cost effective method to mitigate that heat and moisture. Certainly a grower could use a refrigerant-based cooling system similar to an air conditioning system that would provide dehumidification. But the size and scale of those systems are cost prohibitive.”

Maintaining the proper vapor pressure deficit

Sabeh said temperature and humidity are very closely linked through the vapor pressure deficit (VPD).

“As long as a grower is able to control the greenhouse temperature, that usually means he is able to control the humidity level to the point where the vapor pressure deficit is where it should be,” she said. “Even if VPD is not the target that a grower is going for, that is actually the target that he is trying to reach with temperature control with or without humidity control.”

VPD is the difference between the amount of moisture in the air and how much moisture the air can hold when it is saturated.

“There is an optimum level for VPD,” Sabeh said. “For leafy greens and culinary herbs, which prefer a lower VPD, the accepted VPD range is 0.65 to 0.9 kilopascal (kPa) with 0.85 kPA being optimum. Tomatoes, cucumbers and peppers tend to like it drier. The VPD range for tomatoes is 0.9 to 1.2 kPa.

“For leafy greens there is more surface area for moisture to escape the plants. The plants like to be in a more humid space so they don’t release too much moisture too fast.”

Providing adequate airflow

Sabeh said airflow in the greenhouse is really important for breaking up the layer of moisture around the leaf surface of the plants.

“If the leaves are transpiring water, the leaf surface itself is considered saturated,” she said. “The leaf surface is exchanging moisture with the air around it. The more moisture in the air around the leaf surface, the less tendency to transfer moisture from the leaf surface to the air around it.

“This is basically what the vapor pressure deficit is. It is the difference between how much moisture there is at the leaf surface at a given temperature vs. how much moisture there is in the air at that same temperature. If it is within the right range, then the plants are happy because the leaves are freely exchanging moisture with the air. If the vapor pressure deficit is too low that means the air has a lot of moisture in it so there is going to be less transfer of moisture from the leaves to the air. The plants can’t transpire as quickly and nutrients can’t be delivered as quickly to the rest of the plant. If the vapor pressure deficit is too high, the air is really dry, and the plants shut down. As a protection strategy, the plants will close their stomata so that they don’t transpire moisture to the air because it would occur too fast. The loss of water through transpiration would occur faster than the plants could take up water.”

Sabeh said horizontal airflow fans are the traditional method for producing airflow and air currents in a greenhouse.

“Horizontal airflow fans are usually suspended from the trusses or the structure of the greenhouse and blow air in a circular pattern over the tops of the plants without actually blowing directly down on the plants,” she said. “Just the circulation and motion is enough to create turbulence to cause air mixing around the plants to encourage transpiration and convection.

“By breaking up the little saturation pocket of air around the leaves, it facilitates that moisture transfer from the leaves to the air. Under more humid conditions, as air is blown over the leaf surface, a grower can facilitate more transpiration from the plants than if no airflow was blowing over it. Airflow is one of those variables not addressed as often as temperature and humidity control. It is sorted of neglected.”

With the increasing interest in vertical farms, Sabeh said growers are using large grow racks to try to create temperature and humidity conditions in three dimensions.

“Under these conditions it is very easy for air to get trapped over the center of a rack,” she said. “Vertical farmers are really cognitive of airflow because they see these hot spots or these wet spots in the middle of the grow racks so they know they need airflow.

“It is the same situation as if plants are grown in a greenhouse. If more airflow is provided in a greenhouse, more moisture could be removed from the plant surface and help the plant with cooling by convection.”

Maintaining the proper carbon dioxide level

Sabeh said although carbon dioxide is not necessarily impacted by the outdoor climate, greenhouse growers are controlling it relative to the outdoors.

“In a greenhouse where growers are burning fuel to generate carbon dioxide and ventilating at the same time there is a challenge of how much carbon dioxide should be delivered and how is it going to be retained? Is there a way to mitigate the carbon dioxide’s immediate loss to the outside air through greenhouse ventilation?

“One strategy for not overusing carbon dioxide is to provide plants with a boost from carbon dioxide enrichment. Carbon dioxide can be provided first thing in the morning during first light before the greenhouse vents are open. Basically the plants take a deep breath when the sun starts to come out and the stomata open. The sunlight or the supplemental lights are turned on and the plants take up that carbon dioxide. When a grower starts to ventilate because the moisture has built up overnight or the temperature starts to increase because the sun is rising, enrichment with carbon dioxide can be stopped so that it is not being blown out of the greenhouse through the vents and exhausted by the fans. Some growers use carbon dioxide enrichment all day as long as there is enough light from the sun or from artificial light.”

Sabeh said growers can mitigate the loss of carbon dioxide by trying to deliver it as close to the leaves as possible.

“Some growers use under-floor or under-bench ducts to deliver carbon dioxide,” she said. “Some growers may use PVC tubing or fish tubing to distribute carbon dioxide through the crop and directly to the leaves. This is ideal if a grower can find a way to deliver the carbon dioxide in an effective manner without getting in the way of all of the other equipment and people working in the greenhouse.

“This is why some people are looking at the potential advantage of growing in vertical farms. There is an enclosed space and in most cases it is being done in buildings that are not leaky. There are some growers who have considered closed greenhouses. The cannabis industry is really interested in this, but the problem is there is an outrageous energy bill to try and close the greenhouse and not use any ventilation or mechanical cooling.”

Relationship between greenhouse climate variables

Sabeh said the optimum level of carbon dioxide varies for each crop. She said 700-1,500 parts per million carbon dioxide is the level that most growers are trying to use.

“Carbon dioxide is most useful to the plants when there is a lot of light and good temperature and humidity levels or a good VPD,” she said. “Carbon dioxide is transferred through the leaf stomata, the same as moisture through transpiration. At the right VPD the stomata are open to the maximum and are letting out moisture and gulping up carbon dioxide.

“The first thing is having the right VPD to maximize stomata opening. The second thing is photosynthesis, which is driven by light. If the air is being enriched with carbon dioxide, but the light level is very low, much of the carbon dioxide will be wasted. There has to be enough light to facilitate a high enough rate of photosynthesis or the plants can’t use the carbon dioxide. All three of these variables work together. A good VPD is needed for stomata opening. An adequate light level is needed for photosynthesis. And carbon dioxide is needed to maximize the photosynthesis cycle.”

For more: Nadia Sabeh, (916) 775-3724; nadia@doctorgreenhouse.com,
http://www.doctorgreenhouse.com.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

Proper HVAC Maintenance Delivers Savings and Reliability

By John Zimmerman

Learn what preventive maintenance should be done on a controlled environment agriculture heating, ventilation and air conditioning system and what it can cost you if it’s not.

In Urban Ag News Issue 11, I introduced Jeffrey Orkin, CEO at Greener Roots Farm, a hydroponic controlled environment agriculture operation in Nashville, Tenn. I was monitoring the power consumption of Greener Roots Farm’s heating, ventilation and air conditioning (HVAC) system as part of a case study, when one of the compressors in the system failed. Because I had a power monitor on the system before and after the compressor was replaced, I was able to determine how much energy and money the HVAC system was wasting as a result of the problems that led to the compressor failure.

Preventive maintenance schedule

Before I present data on why Greener Roots Farm’s compressor failed, I’m going to discuss a basic HVAC preventive maintenance (PM) schedule. I’ll also highlight the importance of each maintenance activity and provide variations to the schedule that make sense for indoor growing applications.

HVAC preventive maintenance basics

Three common factors that determine the makeup of an effective PM schedule are:

1. The type of HVAC system.

2. The application the system is serving.

3. The ambient conditions within which the system operates.

These factors determine the type of activities that are required as part of the PM schedule and the frequency with which they need to be performed.

The type of HVAC system used determines the components that require PM. For example, a chilled water system requires a relatively elaborate PM schedule because of the number of complex components in this system. Greener Roots Farm has a direct-expansion (DX) split-system, much like those used in residential applications.

Chilled water system components DX split-system components

Chiller(s) Air handler

Pump(s) Condenser

Cooling tower(s)

Air handler(s)

Based on the number of components that require PM, a DX split-system has a much less complex PM schedule than a chilled water system. However, the PM schedule for Greener Roots Farm’s DX split-system differs greatly from a residential application, primarily due to the difference in operation.

The HVAC system for an indoor growing operation needs to operate 24 hours a day and treats a very high latent load (very moist air). Compare that to a residential HVAC system that cycles on and off based on the relative comfort of the space and treats a much lower latent load, thereby reducing wear and tear on the components. Additionally, the high moisture content of the air in indoor growing operations opens the door for issues that residential systems rarely encounter. These include corrosion of metal parts including linkages and drain pans, clogged condensate lines and mold.

The ambient conditions in which a system operates can greatly impact the wear and tear of the system’s components. Greener Roots Farm’s case highlights this fact. The term ambient conditions refer to the immediate surroundings of the system or components of the system. For the purpose of this article, the focus is on the impact ambient conditions have on outdoor components. However, as described above, moist air indoors can negatively impact indoor components as well.

For most systems, components located outdoors are designed to reject the indoor heat to the outside air. In a DX split-system, like at Greener Roots Farm, the outdoor (and heat-rejecting) component is the condenser. In order to reject the heat, the condenser uses a fan to force air across the coil, allowing the heat from the refrigerant inside the coil to be transferred to the cooler outside air (See Figure 1).

When creating a PM schedule for a condenser, the surrounding dirt, dust and debris that can reduce the component’s ability to properly reject the heat must be taken into consideration.

Figure 2 shows how dirt, dust and debris can impact a condenser. Ambient conditions including annual rainfall, direct sunlight and wind have an impact on the life of outdoor components and must be considered when creating a PM schedule.

Sample PM schedule for a DX split-system

Greener Roots Farm case study

There were two reasons that the compressor failed at Greener Roots Farm, both of which are directly related to the system’s ability to reject heat.

1. The outdoor condenser coil was extremely dirty. A dirty condenser coil reduces the airflow across the coil, subsequently reducing the amount of heat that the forced air can remove.

2. The indoor air handler had a loose belt. A loose belt reduces the airflow to the indoor growing space, causing the overall heat content of the return air to rise.

To further complicate things, the condenser at Greener Roots Farm had a two-row coil. This means that even if the perimeter coil (the visible coil) was clean, there is still a possibility that the interior coil was dirty. This is what happened with the Greener Roots Farm condenser (See Figures 3 and 4). The perimeter coil is clean, but the interior coil had not been cleaned for a long time.

Greener Roots Farm was paying a local contractor to do PM on its HVAC system twice a year.

While the sample PM schedule above suggests PM should be done on an HVAC system in an indoor growing setting on a quarterly basis, the coil on the Greener Roots Farm condenser should not have gotten this dirty. Although the hired contractor may have cleaned the perimeter (visible) coil twice a year, it was obvious that that the interior coil had not been cleaned.

Some costs that result from poor PM on an HVAC system are easy to quantify, including the cost of a new compressor, the money wasted for a PM contractor and the downtime associated with fixing the problem. However, the increase in energy cost over time as a result of a slow degrading system is very hard to quantify. Luckily for Greener Roots Farm, a power monitor was placed on the system for three days (spanning four calendar days) before the compressor failed.

We continued to monitor the power for 27 days after the compressor was replaced, the coil was cleaned and the belt was replaced The power monitor took readings in 10 minute intervals.

Below is a summary of the results.

Total power (kW) used

Before: 2,498  |   After: 1,857  |  Delta: (641)

Total energy cost ($0.11)

Before: $274.78  |  After: $204.27  |  Delta: ($70.51)

Cost per day

Delta: ($23.50)

Greener Roots Farm power monitor data

Before presenting Greener Roots Farm power monitor information, there a few disclaimers about the data.

1. In a deliberate, controlled experiment, three days would not be an adequate time sample, especially to determine the increase in degradation over time. However, three days was the amount of time available.

2. Since the power was being monitored for the last three days before the compressor failed, it can be assumed that these were the most inefficient days and that every day before this three day period would have been incrementally more efficient.

3. Furthermore, the assumption was made that this indoor growing facility was operated the same for both time samples.

4. In order to make an accurate comparison, a four calendar-day sample of the post repair time period was chosen that had approximately the same outside air conditions.

Here is a summary of those conditions:

Temperature comparison (Fahrenheit)

Looking at the outside air temperature comparison, temperatures during the time sample after repairs were made were slightly higher, but the power usage was still less.

Lessons learned

The Greener Roots Farm HVAC case study is not a complex, scientific experiment. However, it is a simple example of how poor preventive maintenance can cost growers money in the long run. This case study should also serve as a reminder to ensure that contractors are performing the work they were hired to do.

Many of the preventive maintenance activities for HVAC systems, including cleaning coils, can be done by most employees with materials available at local hardware stores. I recommend growers do some of these activities. This will allow them to become familiar with the results should a professional HVAC technician be hired to do the maintenance.

About Harvest Air

harvestairllc.com

Harvest Air was founded by Chris Whaley and John Zimmerman in July 2015. Both Chris and John are registered professional engineers with a combined 30+ years of experience designing, estimating and managing the installation of large-scale commercial heating, ventilating and air conditioning (HVAC) systems for a wide range of industries.

Controlled environment agriculture (CEA) requires a sophisticated farming process to ensure that crops receive the proper amount of water and nutrients in order to optimize yield. While it might appear that the farming techniques used in CEA are well designed and sophisticated, Chris and John discovered that many of the HVAC systems used in CEA are not adequate. By applying proven principles and knowledge gained from their experience, Harvest Air’s HVAC solutions are extremely efficient and reliable, allowing farmers to focus on their crops and not the infrastructure that supports them.

John Zimmerman, PE
Co-Founder and President
john.zimmerman@harvestairllc.com

John Zimmerman obtained a bachelor’s degree in mechanical engineering from the University of Texas-Austin and a master’s degree in building construction management from Purdue University. He is a registered professional engineer in Texas.

Chris Whaley, PE
Co-Founder and CEO
chris.whaley@harvestairllc.com

Chris Whaley obtained a bachelor’s degree in mechanical engineering from the University of Oklahoma and is a registered professional engineer in Texas.

Both John and Chris have spent their careers designing, selling and managing the installation of mechanical systems for large-scale commercial buildings for some of the largest mechanical design-build companies in the United States.

More predictable production levels and harvest dates are driving growers to adopt controlled environment agriculture.

Even though most greenhouse vegetable growers are producing fewer types of crops than ornamental plant growers, trying to control the environment of these food crops can be a much bigger challenge.

“The environmental control challenges for vegetables are much tougher because the produce is going to be consumed,” said University of Guelph professor Mike Dixon, who is director of the Controlled Environment Systems Research Facility in Guelph, Ontario, Canada. “The fact that they are destined to be a food commodity requires more attention to things like pest control.

“For vegetable production, since the margins are typically small for food crops, growers are trying to tightly control inputs as much as they can without compromising the quality and productivity of the commodity. This is a significant challenge and requires a great amount of detail to environmental control than for typical ornamental crops. Ornamental commodities, since they are not eaten, are not subject to the same kinds of stringent controls, especially with pesticide residues. But it’s more than that. The food safety regulations for food crop inputs and production outputs (e.g. nutrient runoff) are much tighter than they are for ornamental commodities. That means that environment control is a key factor in maintaining production standards and quality standards in a competitive market.”

Meeting market expectations

Dixon said part of the issue with trying to maintain the proper environment for vegetable production is consumer expectations for “perfect” fruits and vegetables.

“Consumers have been conditioned by generations of what today are considered environmentally unacceptable cultural management practices, using chemicals and pest management protocols, that occasionally leave residues,” he said. “Consumers don’t want peppers with spots on them. Consumers don’t want roses with blemishes on the flower petals. In the minds of consumers, they expect virtual perfection and don’t appreciate that the means to achieve this are not necessarily environmentally correct today.

“There is a transition between the old ways of doing things and the new ways of doing things. In terms of controlled environment agriculture, growers are transitioning to production practices that don’t compromise quality and productivity and yet meet environmental standards as well. That can be a tough balance.”

Dixon said that growing food crops in the northern latitudes year-round requires some type of controlled environment production.

“In Canada, six months out of the year food crops can’t be produced unless they’re grown in a controlled environment,” he said. “This requires that the growing has to be done in a nearly subtropical environment in which many disease pathogens and insects thrive. These pests gravitate toward these ideal controlled environment conditions. It’s the growers’ challenge to maintain some kind of balance and still meet the quality and production requirements of the market.”

Minimizing costs, maximizing production

Dixon said the degree of sophistication that is achievable with today’s technology should really be taken advantage of by growers especially in regards to minimizing labor.

“Labor is the top line in the cost of production in a controlled environment commodity,” he said. “Automation, including computer controlled environments and automated irrigation can mitigate the labor bill. Energy is a close second in regards to major costs.”

Dixon said the winter environment in the northern areas of the United States and in Canada is a major challenge for controlled environment growers.

“Winter production in these areas requires a higher level of technical sophistication than is needed for operations located further south,” he said. “The farther south an operation is located the issue then becomes heat extremes. In the middle latitudes, which include a large portion of the United States, environment control challenges are not as extreme as they are in Canada, Mexico and South America.

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“In more moderate climates, growers tend to be slower in adopting more sophisticated technology because the cost benefit is harder to justify. Labor costs will be the major factor that will drive the conversion to automation for a lot of middle latitude growers. Up until recently they haven’t been required. What has changed is that the capital cost requirements for a lot of technology enhancements or retrofits in older greenhouses have become very attractive. For example, the cost of LED lighting is not only energy conservative, but it can also enhance productivity with the appropriate technology and application information.”

More predictable, profitable production

Dixon said since the margins on food crops are relatively small compared to many ornamental crops, growers need to have relatively large greenhouse operations in order to be profitable.

“We’re talking on the order of 50-200 acres of controlled environment greenhouses,” he said. “To consider manually managing that scope of a greenhouse production system is prohibitive. It’s not realistic, growers couldn’t do it. It’s absolutely required that that they engage some form of automation, controlling especially irrigation, lighting and conventional environment control including opening vents, etc. The largest controlled environment food production area in North America is in the Leamington area in southwest Ontario. This area is typified by very large, highly sophisticated controlled environment agriculture systems for the production of tomatoes, peppers and cucumbers.”

Dixon said automating irrigation to reduce labor costs and automating basic temperature and humidity control in the greenhouse will significantly enhance the production system.

“It comes down to the cost benefits analysis,” he said. “Each grower has to look at it on the basis of their own specific case. It depends on the commodity. It depends on the local market and the margins growers can obtain with a more homogenous quality that they realize with automation. Automation offers more predictable production levels and predictable harvest dates. These are the kinds of issues that drive the adaptation to controlled environment computer automation and even robotic systems.

“Adding more sophistication gives more reliability in some cases as well as predictability in terms of production and quality. And that can only enhance a grower’s attractiveness to the market.”

Dixon said automating irrigation to reduce labor costs and automating basic temperature and humidity control in the greenhouse has been shown to significantly enhance the production system of a grower’s greenhouse.

“That’s really the goal,” he said. “Look at the capital cost requirement to obtain that level of technical sophistication and amortize over a reasonable three- to five-year period. Then look realistically at the labor savings, energy savings and the environmental impact savings including waste and runoff that would be realized by doing it. If it makes economic sense then there’s the answer.

“Sometimes it’s difficult to line up all of the things that need to be considered in a cost-benefit analysis. Depending on the size of an operation, if it’s a small-scale operation, it may not make economic sense to incorporate this automation because the cost-benefit is probably going to take 10 years to realize. But as the scale of the operation goes up, generally the justification for automating the system and reducing labor costs is greater.”

Bringing space technology back to Earth

One of the major elements of Mike Dixon’s research program at the University of Guelph’s Controlled Environment Systems Research Facility is the development of technologies for food production (i.e. life support) in the context of long term human space exploration missions. Dixon said the technologies being transferred from his program to the greenhouse sector are those that were developed for these missions.

“These technologies are being adapted to terrestrial agri-food sector applications in as economical a way as possible,” Dixon said. “Some of the technologies being developed include LED systems, environment control protocols, recycling systems, environment sensors and imaging systems for diagnostics.Terrestrial agriculture is benefiting greatly from research activities taking on the challenge of growing food on the Moon and Mars.”

For more: Mike Dixon, University of Guelph, Ontario Agricultural College, School of Environmental Sciences, Controlled Environment Systems Research Facility, Guelph, Ontario, Canada N1G 2W1; (519) 824-4120, Ext. 52555; mdixon@uoguelph.ca; http://www.ces.uoguelph.ca.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.