Energy is one of the biggest expenses in greenhouse production. Anywhere from 65% to 85% of all energy consumed by greenhouse operations goes toward heating, according to a greenhouse energy conservation strategy bulletin produced by Michigan State University’s Erik Runkle and Rutgers University’s A.J. Both.
Wasted or lost heat, maintaining an ideal greenhouse temperature, and inefficiency in heating systems are three of the most common problems growers face when it comes to heating. Here’s a look at some ways to overcome these challenges:
Problem 1: Lost Heat
Solution: Runkle and Both suggest inspecting greenhouses for leaks and patching any holes in plastic coverings or side walls. In glass houses, replace any broken or missing panes. Also, make sure all greenhouse doors close completely. You may want to weather-strip doors, vents, and fan openings for added protection against drafts. And consider shutting off some of your greenhouse’s exhaust fans from late fall through early spring and covering those openings with plastic.
If you want to make a greater investment in energy-savings, consider insulating side and end walls. According to Both and Runkle, the knee wall or curtain wall (often made of concrete block or brick) can be insulated to reduce heat loss.
Problem 2: Finding The Ideal Temperature
Solution: Runkle and Both recommend managing greenhouse temperatures based on specific crops and their finish dates. When greenhouses get too cold, plants will stop developing. However, overheating can lead to wasted energy. So how do you find the sweet spot (or optimum temperature) where plants will grow as fast as they can?
Researchers from Michigan State, the University of Florida, and the University of Minnesota have developed a tool to help growers determine just that. The Computer Decision-Support Tool for Floriculture Crop Producers allows growers to select a specific crop and finish time at a particular temperature based on past experience, starting plant size, and finished crop specifications. Then, the tool predicts the effect of increasing or decreasing temperatures.
Problem 3: Inefficient Heating Systems
Solution: To get the most out of your heating system, you must perform regular maintenance. Flush boilers to remove scale and deposits, and check the burner combustion efficiency of unit heaters and boilers with a flue gas analysis kit. It also helps to clean heat exchangers with a wire brush and vacuum. Be sure to repair or replace any malfunctioning steam traps, and check insulation on outside pipes. Finally, clean fan blades and check jet tubes for leaks.
If your heating system is still inefficient after a thorough tune-up, it might be worth considering an upgrade. Some of the newer, condensing boilers, for example, are highly efficient. The Infinite Energy 2 condensing boiler from Delta T Solutions offers up to 98% efficiency.
You might also consider investing in radiant bench or floor heat. These systems heat starting at the soil level, allowing for faster germination and quicker turns. In addition, less heat is lost in the air compared to forced-air heating units, resulting in more energy dollars saved.