The Problem
High tunnel growers come to know through trial and error and some hardship that their success depends on managing the temperature and other conditions inside the high tunnel with care. That is, that maximum yield and quality are possible only when conditions inside the tunnel and near the crop are optimal as often as possible. High tunnel growers also come to learn that achieving optimal conditions round-the-clock and day after day is difficult and costly in various ways. For example, it is difficult because crop needs and conditions outside the tunnel can change dramatically and quickly, especially during key points in the crop cycle in spring and fall. Reacting to changes in crop need and other must-dos on the farm can be challenging. Managing temperature and other conditions inside the tunnel usually also requires undesirable investments in time, effort, and money. Of course, conditions inside the tunnel are usually set by controlling the extent to which sidewalls, vents, and/or doors are open, with the height of sidewall rollbars being particularly significant. The trouble is that the position of most sidewall rollbars is set by hand. This requires the grower or another person to stop what they are doing, travel/go to the high tunnel, and reposition the rollbars manually. This commitment and expense are unfortunate enough. However, the fact that it may need to be done multiple times per day for many days in a row for conditions near the crop to remain optimal becomes problematic for many high tunnel growers. They are required to choose between: (a) continually repositioning sidewall rollbar heights (“babysitting” the tunnel) at some direct cost and at the expense of engaging in other activities or (b) setting sidewall rollbar position at a “compromise” height and accepting the consequences of conditions (e.g., temperature, wind) being above- or below-optimal for potentially lengthy periods. In our view, high tunnel growers should not be required to have to make that choice.
Existing and New Solutions
Various companies (e.g., https://www.advancingalternatives.com) agree and offer automated ventilation control systems involving sensors, a control panel, and sidewall motors. We have had a version of the Advancing Alternatives system on a moveable Rimol high tunnel since 2015 and have been very pleased with both (control system, high tunnel). The high tunnel’s sidewall motors, endwall vents, inflation fan, and control panel are all powered by a standard 12-volt battery charged by one medium-size solar panel. It’s an impressive system. However, we are also aware that fully automated approaches to ventilation can cost more than some growers are willing or able to pay and place control of the high tunnel conditions largely in the hands of the control panel, not the grower.
Therefore, we have been working to develop a low cost, DIY way to control sidewall motors remotely that keeps the grower directly in control of sidewall position (e.g., to account for conditions that a fully automated system may not monitor, at least without additional cost).
Alex Herridge will soon complete his undergraduate degree in Computer Science and Engineering at The OSU and his contributions to the effort have turned the idea for this alternative, grower-friendly system into reality. Full plans for the system will be available in a separate publication soon but its key features include:
1. Standard sidewall motors powered by a battery-solar panel combination, as described above;
2. A standard voltage-regulating unit converting 12 volts from the battery to 24 volts needed by the motors (approx. $80.00);
2. A motor controller (available at electronics stores or online for approx. $15.00);
3. An off-the-shelf, WiFi-enabled microcontroller to act as the brains of the system (approx. $5);
4. WiFi already present on the farm property or wireless access with a hotspot or similar ($0 to monthly charge typical of a mobile phone plan); and
5. Code for the motor controller (no charge).
To proceed, motors are attached to sidewall bars and powered and a basic network connection linking the grower’s phone (or other device) and the microcontroller is established. The entire process can be completed in approximately four hours once all materials and WiFi are on site. Thereafter, the sidewall motors can be controlled with one’s mobile phone or other linked device using a simple interface setup for the purpose. Pictures of the preliminary, bare-bones version of the interface we used to raise and lower a sidewall bar on a high tunnel at OARDC on December 13 are given here. The bottom-line of this approach and system is that it will allow growers to raise and lower sidewalls from wherever they have internet access using low cost, off-the-shelf hardware. Watch for additional posts regarding this system at VegNet and other locations and contact me (Matt Kleinhenz; kleinhenz.1@osu.edu; 330.263.3810) if you are interested in learning more about or testing the system on your farm.
(OSU Computer Science and Engineering student with the motor and micro controllers and standard battery charged by a solar panel.)
(Exterior of the Rimol moveable high tunnel and the solar panel used to charge the battery powering rollbar motors, endwall vents, inflation fan, and control panel.)
(Simple, password-protected interface for controlling sidewall rollbar position. Usable from anywhere the owner has internet access and allowing them to control sidewall rollbar height remotely.)
