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darnrus

Geo thermal heat

darnrus
9 years ago

I thought some might like to know about our project on the high plains of western Nebraska. We have a harsh climate, lots of high dry winds, extreme cold days many 20 below zero in the winter and above 100 degrees in the summer. Or elevation is 3700 feet and we have tons of sunshine in the winter.
Over the past 35 years I have developed a structure and growing system that incorporates what we call "low grade Geo-Aire", the original unit is 78' x 16' and 12' high in it we used 7 6" perforated drainage tile tubes with a total length of 1100'. We bury this tube at an 8' depth where the temperature is a constant 52 degrees. The tubes leave the unit at one end wrap around about 30' from the south side of the greenhouse and enter at the other end. Our only source of heat energy is a 1/3 hp motor (7 amp) on a blower the blower is on top of a box holding the end of the 7 tubes. The air is forced through the tubes at one end and enters at the other end. This is an air tight system in the winter and the unit must be sealed very well. everything is controlled by a thermostat that closes at 50 degrees. We only keep the temperature above 28 degrees as this is the point of damage for the plants we grow.
The structure is designed to take advantage of a minimum air volume, insulated back north wall that is slanted at an angle to reflect the low winter sun into the designed 4' pit with raised growing planters on the north and south sides. The original greenhouse is 22 years old and houses thousands of plants and trees mostly sub tropical and tropical. We have 12' in ground orange, lemons and fig trees each producing and average of 150 lbs. of top quality very large fruit each year. at this time we have more than 16 citrus trees of all types. We have tried every type of plant we could find over the years to see how or if they would grow in this environment I am surprised at the results probably 80% of the the plants lived and over 60% thrive. Among the best results are any ;root vegetable but it is too warm in the winter to grow the cabbage family. Any vegetable can be grown through the warm months and in our new units tomatoes and about any other crop. The perennials that produce heavy are 9 types of warm weather grapes, blackberries, Feijoa, cymbidian orchid, hundreds of epiphyllum, bromeliad ,camellia, roses, etc.
last winter we built a 78' unit at the Alliance High School in which we incorporated a lot of the improvements learned from the original greenhouse and since then have built several more with even better improvements. The high school unit in the first year has averaged less than 40 cents a day for energy at their rate of 7.4 cents a KWH.
There are several internet sites showing photos and videos of our project Google Russ Finch Nebraska.

Comments (2)

  • fruitnut Z7 4500ft SW TX
    9 years ago

    Mr Finch:

    I'll offer a few comments on your greenhouse after reading about it now and several years ago.

    I think the design takes advantage of your climate and soil temperature to produce a very energy efficient system. Probably about as good as it gets anywhere in regards to energy efficiency.

    My reservations are that to me energy efficiency is wonderful but it's not the be all and end all in greenhouse design. I'm a crop scientist so look at things from the crop viewpoint. My thought is a greenhouse should be designed to maximize crop yield and quality. And for fruits it's eating quality that's most important to me.

    The most energy efficient greenhouse is going to provide an optimal environment for something but certainly not for everything. This is obvious just from your remarks. You built the most energy efficient system and then went in search of crops adapted to that system.

    I'd rather build a greenhouse to optimize the crop production factors I'm most interested in, namely eating quality of stone fruits. This requires not only winter chilling but proper light, temperature, and humidity during the growing season. I can't do that by building the most energy efficient system.

    My 1728 sq ft 16ft tall greenhouse was optimized for fruit crop production. Heating and cooling costs run about $900 per year with $0.12 KWH electricity cost and $15 per MCF natural gas, both pretty high. That puts my structure on par with yours in my estimation when you consider installation and energy cost. And it's designed to meet my crop goal. Yours is an efficient system in search of a crop.

    In short a greenhouse should be designed around the requirements of the target crop in the environment at hand rather than finding a crop for an efficient design.

    Thank you for posting.

    This post was edited by fruitnut on Tue, May 13, 14 at 9:01

  • darnrus
    Original Author
    9 years ago

    Early in our development experiments we closed of 35' of the unit and planted all northern trees that required on the average of 800 hours of chill. It required 2 blowers on thermostats to attain 45 degrees. The first part of December we would close the area off and cool until the middle of January. At that time we allowed the geo thermal to take over and within 2 weeks all the trees Peach, nectarine, plum black cherry and some berries all come into bloom at the same time. We had fruit in June, the problem was there was no interest in the project and the nectarine although dwarf took over the whole area but it produced heavy crops of excellent fruit. We replaced those trees with citrus. Our original citrus production for an 8' circle is 150 lb. @ $3.50 yields $ 525 we grow other crops in the ground under the trees and grapes above. The average Eureka lemon in our stores are around 7 ounces ours average over 10 probably due to waiting for them to mature and enhance the lemon flavor over the citric acid.
    In the latest units we have developed a growing system that allows for tomato production year around and we have picked ripe tomatoes in February. We are now working on using the new type LED panels that are very affordable and require only 14 watts. this looks very possible as we are now using them under the citrus to help with Photosynthesis on the north side of the plants in winter. It seems to be working.
    The climate we have attained with the geo is pretty close to the winter climate of San Diego and our sunshine is very close to San Diego.
    Everything we have done for over 35 years is experimental and trial and error but at this point we can safely say if these units are built on the high plains and the design is adhered to they can open up this area to 12 month growing which hasn't been profitable until now. The cost of a typical 78' automated unit would be under $20,000 if a person could do some of the construction man power. These are units that can be left unattended for 3 or 4 weeks in the winter and a week in the summer.