Horticulture Principles and Practices

This system was demonstrated in a 58,000 square foot section of greenhouse at
Kube Pak Garden Plants, Inc. in Allentown NJ. Experience with this complete system
quickly showed that the major benefits, on a commercial scale, to both energy conservation
and improved plant growth, were the curtain system and the floor heating.
While the solar collectors did make a significant contribution to the savings of fossil
fuel, the major energy savings were derived from the curtains and floor heating for
those crops grown on warm floors with reduced air temperatures. As noted earlier,
curtain insulation systems and root zone heating are widely applied in commercial
greenhouses but use of solar collectors as a source of warm water for root zone heating
has not been widely adopted. As the cost of gas and oil continue to escalate the
economics of utilizing solar collectors for this type of application are likely to
improve. A portion of the 58,000 square feet of the first crop of fall Poinsettias grown
on the warm floor under the energy saving curtain are shown in Figure 2. Figure 3
illustrates the low cost solar collectors used to warm the water in the floor. The energy
savings due to the greenhouse construction, warm floor, energy saving curtain and
solar collectors are documented in Figure 4.
Partly as a result of the technical success of the large commercial solar energy
demonstration project, interest in the use of industrial waste heat led to the design and
construction of a 3-acre commercial greenhouse facility in 1980. The performance of this
first block is fully described by Manning et al., (1983). Like the solar demonstration project,
the first and most important aspects were to design an energy efficient multi-span
greenhouse with insulating curtains and a floor heating system. The first floor heating
system incorporated the flooded floor for heat storage capacity as well as maximum heat
transfer capability with warm water from the power station circulating through plastic
pipes on one foot centers embedded in the under floor gravel. Waste heat could also be
circulated through finned pipe in the greenhouse and there was a coal fired back-up
system that could be used to provide additional heat in the coldest weather. During the
first years of operation there was only connection to one of two cooling towers at the
power plant seen in Figure 5, so the back-up system had to be used when that unit was
FIGURE 2
Poinsettias.
D.R. Mears)
First crop of fall
(Source: A.J. Both and
FIGURE 3 Low cost solar
collectors. (Source: A.J. Both and
D.R. Mears)
12.3 Internal Environmental Control 413