A Design Model of Transient Temperature Performance for a Green Greenhouse

Abstract

Synergistic Building Technologies (SBT) built and monitored a
“green” solar greenhouse under the auspices of the Colorado Department of Agriculture in 2010. This greenhouse incorporates advanced
methods of energy conservation in an application that traditionally uses
only methods with very inexpensive capital expenditures. The SBT prototype accommodates year-round harvesting of summertime crops using
sunlight as its sole heat source. A comparable planting regimen would be
prohibitively fossil fuel-intensive using prevalent practices. This article
presents a thermal circuit model of SBT’s design with an emphasis on
winter energy performance. The model computes interior air and soil
temperatures given the greenhouse’s size, composition, and location. A
method is presented for reconciling the computed timing and amplitude
of temperature transients with those measured in SBT’s prototype. The
model thereby provides insight as to whether a proposed combination of
insulation, thermal mass, and insolation will achieve specified conditions
for plant growth. All modeled and measured results suggest that SBT’s
greenhouse design offers an energy-efficient alternative to wintertime
importation of fresh food in cold climates.