Wednesday, April 30, 2008 at 3:07 AM
For most backyard gardeners, a greenhouse is a fairly low-tech investment. A wooden frame and some plastic sheets or panels are sufficient to help tropical or frost sensitive plants survive the long mid-west winters. But for commercial growers, mere survival isn’t enough. They must produce healthy and thriving plants year-round and that means big heating bills. In Cleveland, scientists are pioneering a high-tech method for bringing those bills down. ideastream®'s Gretchen Cuda reports.
Cuda: Two years ago, Natalie Ronayne of the Cleveland Botanical Garden did what any good Chief operating Officer would do– she looked for ways cut costs. And one of her biggest bills comes from heating their 18,000 square foot glass house during the winter months.
Ronayne: We were taking a look at how to curb our demands on our energy bills and we were talking with some folks in the renewable energy field in Cleveland – and we were talking about designing a smart greenhouse.
Cuda: In other words, a computer controlled greenhouse capable of optimizing growing conditions, while maximizing energy savings. But in order to build a smart greenhouse – they needed a smart new technology – and researchers at Kent state had just the thing – a glass made from liquid crystals that could go from opaque to transparent simply by flipping a switch.
SOT: switch flipping … brief talking
Cuda: Sandwiched between two panes of glass is a thin film of liquid crystals. In their natural state the crystals are randomly arranged, diffusing the light and giving the windows a milky white appearance. But when an electric current is passed across the panel the rod shaped crystals in the film line up so that light can pass through them and the window becomes instantly transparent. Oleg Lavrentovich, and his colleagues at the liquid crystal institute at Kent state University liken the process to tailor-made weather conditions.
Lavrentovich: What we have is kind of a switchable fog. You know fog is scattering light because you have little droplets of water in air. Here you have little droplets of a liquid crystal in a polymer matrix and that produces the scattering effect but also it gives us the opportunity to tune the transparency by the electric field.
West: Basically we have the ability to switch between a cloudy and a clear day.
Cuda: That’s John West – another liquid crystal expert. He says smart glass is not an entirely new concept. It’s been used as privacy glass in interior applications like bathrooms for a number of years, but has rarely been used in exterior windows. This is the first attempt to use it in a greenhouse application. In the first phase of the project, two 8x10 foot greenhouses on the Garden’s grounds– one with smart windows and one without- will be used to evaluate the energy savings, as well as compare the effects of the liquid crystal windows on plant growth. Mark Druckenbrod, a horticulturist at the garden, hopes they’ll be able to optimize the two most important aspects of Greenhouse growing: Heat and light.
Druckenbrod: That’s the beauty of this glass – we can control the light intensity in order to maximize plant growth and the second thing we can do is control the amount of heat that is permitted to either enter the greenhouse or leave the greenhouse – and you can see the advantage of controlling that seasonally, especially in Cleveland, OH.
Cuda: Much like photosensitive sunglasses, on warm sunny days the windows will become cloudy and provide relief from intense light and heat, but on cool cloudy days the glass will remain transparent during the day, but adjust at night to trap the heat inside. And light and heat may be just the beginning – Variations in the amount of blue or red light can make the difference between a tall and spindly flowers or full and lush ones. The ultimate goal is to be able to tune the windows to specific wavelengths to boost plant growth.
Druckenbrod: We’ve never had the ability to filter out light waves, so that’s part of the exciting part of this research. Wouldn’t it be wonderful if we could maximize the exact light that these plants require and allow a commercial grower to bring a crop to harvest, let’s say one week earlier than ordinarily is possible. That is a significant improvement.
Cuda: Like all green buildings, green greenhouses are a bit more expensive than conventional ones – 100 dollars a square foot. But researchers are quick to point out that prototypes are always expensive, costs always come down – and in the long run, the energy savings could well be worth it. Gretchen Cuda 90.3