Controlling All Possibilities
Top tips from the experts on making the best use of environmental controls.
June 20, 2008
Environmental controls can do a lot these days, so how can growers better utilize controls? What are the latest technologies and tips for greenhouse controls? We asked environmental controls suppliers these questions and here are their responses.
Open Systems & Keeping Histories
by ALEC MACKENZIE
With the release of our new Titan control platform, Argus has extended the power and flexibility of automated equipment control for commercial growers. Our system anticipates the need for new ways of operating greenhouses to minimize energy and water use, and for increasing productivity. It is designed to handle the new structures, equipment and growing practices that we foresee will be needed in response to increasing energy costs and tighter margins.
Accordingly, we have taken an open systems approach to configuring equipment control capabilities. We provide a suite of programs designed for the efficient operation of typical greenhouse equipment such as vents, mixing valves, etc. We include many features to anticipate all types of operating requirements and constraints. At the same time, we build in a level of safety that respects the physical limitations of the equipment such as duty cycles, wear and tear, etc.
We also include a powerful collection of generic programs that can be used to configure practically any type of equipment control decision or response. We do this because it is impossible to anticipate every control requirement and operating constraint our customers may need, and also because we just hate saying no to anyone.
One of the many control concepts we have developed is the ability to make control decisions based on recent historical events. For the most part, traditional control decisions are based on instantaneous or near instantaneous information such as the current climate temperature. However, there are times when it can be useful to steer the climate by using information gathered over the last few hours or days. This can provide a more complete picture of where a crop might be in terms of its development, current photosynthetic capabilities and stored energy reserves. You can then use this information to influence control decisions. For example, you might decide to elevate the temperature on nights that follow bright sunny days. This can help ensure the full assimilation of the energy stored through daytime photosynthesis. For crops where timing is critical, you can also use this information to either accelerate or slow down the growth rate by automatically adjusting the average daily temperature.
The new Argus Titan system has enhanced monitoring and data recording capabilities. This functionality is becoming increasingly important as greenhouse equipment systems become more complex. The control system must be able to monitor itself, as well as the connected equipment and the processes that are being controlled. It must also be capable of conveying this information to the operator as clearly as possible. Continuous data recording is an indispensable tool for spotting subtle problems, evaluating long-term trends and visualizing the interconnected effects of parameters such as heat, light, humidity and equipment operations.
Our aim is to put the grower in charge of the climate. We know how to operate equipment safely and efficiently; growers know their crop and what it needs. Within the limitations of structures and controlled equipment, the control system must be capable of automatically adjusting all controlled production variables such as temperature, humidity, light, water and nutrients. Only then can growers consistently achieve optimum crop performance and productivity.
Cooperation Between Grower & Supplier
by KORNEL STRZALKOWSKI
Every greenhouse operation is unique and each grower has his own views on ideal growing conditions. Ideally, you want to see an immediate return on every new investment made, as well as ongoing positive returns on existing investments. In order for this to happen, your control system needs to be optimally integrated within your operational process to provide the information you need to create the perfect climate. Each grower grows his own crop in a distinctive environment at a unique location. In the operation, the needs and ideas of the grower have to be combined. Priva has a wide program of controllers available. Priva can deliver the modular Maximizer controller, which is easy to use, up to sophisticated, tailor-made Integro systems with electrical panels.
One solution to utilize controls better is cooperation at the start between the grower and installer for the specific greenhouse operation. This is what we call the "Optimahouse" approach. We conceive, manufacture and optimize (thinking, making, perfecting) a system so the best possible climate prevails in the greenhouse. Together, we make the next step with you. The Priva project engineers are available at the start of the thinking process.
Secondly, the control systems have a lot of unused possibilities. The software is available, the hardware is there, but how do you use this and improve quality and quantity? Two immediate areas in which a control system can be very effectively utilized are energy and crop strategies. This will improve the quality and quantity of your product and save you money in energy costs.
Energy costs for a greenhouse operation can be as much as 33 percent of the total operating costs for growers. There is an interrelationship between the three aspects of a greenhouse operation: type of greenhouse installation, computer controls and crop. This interrelationship has to be optimized. There are many possibilities in setting up the controls, but not all growers have the time to do this. Priva, working with the grower and their consultant, can optimize the climate and energy strategy. The Priva advisor will bridge the gap between the required cultivation strategy, automation and energy consumption. The advisor will work with the grower to help determine how to optimize the climate controls for the grower's own situation. The initial energy savings, after the visit of the energy consultant, can be 5 percent of your energy cost.
Lastly, visits are not always possible by consultants and support technicians. At times, it is best to have someone on site for the first meeting, but further support can be done by remote access. Priva has developed a new service called Web Services. Through the use of the Internet, it is now possible to provide advice and support and avoid expensive travel costs.
Maintenance Is Key
by PATRICIA DEAN
Fall is an excellent time to fine tune your controls to ensure you're getting the best performance.
No matter what type of control you have, you can refine it to maximize energy efficiency.
- Have you checked their calibration? Running warmer or colder than you intend to because of a thermostat that's out of calibration costs you money. According to the U.S. Department of Energy, every 1 degree of improved accuracy reduces energy consumption by 3 percent.
- Can you shade or aspirate your thermostats? When warmed by the sun, they will read a temperature higher than the real air temperature. Your fans will stay on too long and your heat will come on too late.
- Check on investing in a simple four-stage control with a centralized temperature sensor. It'll pay for itself in one winter.
- Check calibration.
- Ensure the control is optimizing crop production and energy savings as it switches between day and night settings. If not, you might be impacting the savings of running your greenhouse at a lower night temperature.
- Check calibration annually.
- Because of their variety of features, there are added opportunities to make sure you are getting the best out of your control.
- Are you taking full advantage of its scheduling features?
- Day length: perhaps you can transition to day temperatures 30, 60 or even 90 minutes after sunrise, or slow down the ramp time between day and night, allowing the sun to help warm the house to day temperatures.
- Energy curtain cover/uncover times: You might choose to cover earlier than sunset or uncover later than sunrise to extend the time that the curtain insulates your house.
- Pad pumps can be scheduled to turn off two or even three hours before sunset to allow them to dry out every day. This practice discourages algae, which lessens the need for chemical treatments and extends the life of the pad.
- If you have both roof vents and fan-and-pad cooling, is your sequence of operation set to let the vents handle as much of the cooling as possible? Many users set fans to sequence on only 2 to 3 degrees above the set point, which gives the vent little room to operate.
- Have you put your pad pump at an energy-efficient place in your sequence of operation? Having the pad pump cycle on before the last stage of fans can delay or even save the fan stage from being turned on. The small pad pump provides enough extra cooling to save several horsepower of fan motors in the spring and fall, when cooling loads are less demanding.
- If you use supplemental CO2, are you using your integrated control's features to delay ventilation and air conditioning to get maximum CO2 dwell time? Have you set your ventilation interlocks correctly so that the CO2 is shut off when you need to ventilate?
- Are you using the humidity monitoring and control features of your control? Did you know when the weather is not too severe, you can run your pad pump to add a little humidity to a dry house? Have you used the control to keep humidity from rising above 90 percent where condensation and disease problems are most likely?