Nursery Root Heating System [RE-wrenches]

[Dean T. Newberry]

Hi Jeff,

I have worked in the radiant/hydronics/PV marketplace for several years.
I am quoting a 1.5 acre greenhouse for cogen/hydronic heat/solarPV.
They have radiant floors, and root heating without air heating burned the
roots,
Thermal conductance to the soil bags was more efficient than radiation to
the leaves.
You have to be very careful to balance air temperature and soil temperature.
They have many propane fan convectors to heat the air, and are not using the
radiant floor.

My proposal will include a temperature limiting scheme on the floor.
Replacing the Gas Convectors with Hydronic fan convectors to heat the air.
Replacing the Boilers with Cogen fuel/hot water for electricity and hydronic
water.
PV will be used to offset the total kWh.

Keep in mind on the electric side that in net metering commercial rate E-7,
there is a demand charge, PGE uses the largest monthly demand and annualizes
it, because it is an annual billing rate. Staged motor and lighting starting
controls to spread the startup demand over several minutes can make a big
difference in annual demand.

Good luck with this project  cul  deant at dcn.org


-----Original Message-----
From: Jeff Yago [mailto:jryago at earthlink.net]
Sent: Friday, June 13, 2003 12:07 PM
To: RE-wrenches at topica.com
Subject: RE: Nursery Root Heating System [RE-wrenches]


We are currently working with a client building a large solar heated
greenhouse with both passive thermal heat and photovoltaic to power his fans
and lights.  The Greenhouse is constructed with massive masonry walls (over
16" thick) and floors with major insulation, and we have multiple thermal
water holding "wells" at a low point across the 80 foot front.

The system is not completed yet, but includes large raised fish tanks and
combines the waste water with the plant fertilizing process - I wont go into
that now, but I do know that heating the roots of his plants allows them to
grow even when the space is fairly cold.  I never understood why all
greenhouses didn't do this, as it is easier to heat a small diameter piping
loop than a big room totally walled with poorly fitted glass windows.  I
also know that his hot water does not need to be super hot, since it is
close to the plant roots.  Hopes this helps and check with me off line for
more info.

Jeff Yago

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