Greenhouse at Asheville-Buncombe Technical Community College

South-side of greenhouse
-located at Sycamore Bldg., A-B Tech
-approximately 1200 sq. ft.
-construction with 1 ft. thick cement blocks and single layer glass
-heated with 2 steam unit heaters
-forced air ventilation on outside west wall, windows open and shut

Winter CSAs'

    Is there anything bad about being part of a CSA?  You receive a variety of super fresh, locally grown, vegetables and fruits, directly from the farm to the consumer.

   The only part that takes a little bit of thought, at least for me, is having to come up with new recipes for veggies and fruits that I don’t normally buy and eat.  But really, is adding variety and vitamins to our diets a negative thing?  How terrific would it be to have CSA’s all year round even in winter?  Winter Sun Farms is doing this through Blue Ridge Food Ventures and local farms.  Check them out at http://www.wintersunfarmsnc.com/

   A great way to to grow winter vegies in WNC is to grow indoors in greenhouses.  WNC winters can be harsh and we often experience snow, frigid winds and temperatures.  Greenhouses provide shelter, heat and a controlled environment.  So, why don’t all farmers do this?  I assume it’s due to the difficulty and cost of building and maintaining greenhouses with heating as its highest energy expense.

    RGEES, LLC is currently working on developing a procedure for heat storage solutions in greenhouses by maximizing the thermal mass and using latent heat storage through phase change materials.  What is thermal mass and latent heat storage?  It is anything that absorbs solar heat and energy during the day when the sun is out and then releases it at a later time.  Our main purpose is to design a practical and useful system that will dramatically reduce overall energy costs by decreasing fossil fuel consumption.

   We welcome any and all input from farmers, greenhouse owners/operators and experts on greenhouse heating and cooling.

--We’d like to know what your biggest challenge is concerning temperature?
--What kind of return on investment you expect (less than 5 years, 5-10 years)    

If you already have a greenhouse, we’d like to know about:  location in relation to seasonal temps, square footage of gh, structural layout, coverings, insulation materials, thermal mass, time/seasons of operation, desired gh temperatures for summer and winter months, heat/cooling systems, fossil fuel consumption, annual energy costs.

   Please feel free to contact me at nina@rgees.com

Heating at Huckleberry Ridge Farm's Greenhouse

     Recently, I’ve been visiting local farms and nurseries to check out the how the locals have constructed their greenhouses and the creative ways in which they are heating and cooling them.

    My first visit was to a lovely, little dwelling in Old Fort called Huckleberry Ridge Farm.  The owners, Ken and Judy, have built a small greenhouse that they use to grow greens during the winter months.  There is an infrared system that heats the dirt the on table beds where the greens grow.  They supplement with a wood stove and small fan to circulate the warm air on cold winter nights which has substantially, lowered their heating bills.  They’ve cleverly, placed bubble wrap on the inside of the roof covering for added insulation as well as insulating the backwall and using bagged leaves on the edges of the greenhouse.  They’re always seeking more efficient ways to heat the space and to increase temperatures during winter to grow more food.  A phase change material of 70 to 80 degrees F would be a perfect fit to store the heat for later use,  for decreasing fossil fuel consumption and burning less wood.   

    Judy and Ken’s specialty is fine rabbit meat.  They have beautiful, healthy rabbits which they process themselves at the farm, chickens for eggs, various greens and vegetables and lively ducks and geese that roam the property!  I can attest that their rabbit meat is delicious and they’ve got the best tasting eggs we’ve had thus far!

Thank you for the visit, Judy!  
Huckleberryridgefarm@hughes.net

Indoor Agriculture

 The importance of temperature control:

    The science and practice of producing high quality, high quantity plants and veggies indoors is better understood and precisely controlled more today, than ever in the past.  I’ve been reading quite a bit on controlled environment agriculture (CEA) or hydroponically-based agriculture.  Although it may seem unnatural to grow plants in a such a manipulated manner, there are irrefutable advantages to hydroponics.  

PCM Trees at Das Tropenhaus, Berlin

   This is by far the most creative usage of phase change material in a greenhouse application, I’ve ever seen.

   Just a quick bit of history... Construction of the botanical gardens in Berlin began in 1897 with the purpose of exhibiting exotic plants brought back from the German colonies.  ”Das Grosse Tropenhaus”, a main feature of the botanical gardens, is currently the largest, self supporting, glass structure in the world.  

   This gigantic tropical greenhouse maintains a temperature of 30 degrees Celsius with high humidity.  Before its recent renovation, it utilized approximately 1,500 tons of coal a year.  After recent renovation, energy consumption levels are one-fifth of previous usage.  Wallboards, tiles and concrete containing PCM, were considered for energy storage inside the structure.

   

The Eden Project

   Last week, a friend of mine who lives in England, sent me a link to this outrageous park in Cornwall, called the Eden Project.  It’s basically an elaborate construction of domes (Yes, I’ve fallen in love with dome sturctures) transformed into gigantic greenhouses that sustain a global collection of plants; some, very peculiar.  It is a multi-purpose park that holds gardening and educational courses for all ages to music festivals, theatre productions, art exhibits, etc.

   These biomes sit on a foundation of granite.  Eden’s plan is to build the UK’s first geo-thermal power plant  utilizing the heat from the radioactive decay in the granite, deep inside the earth’s crust.  Although, drilling a hole 3 miles deep into the Earth must have an outrageous cost, the park experts are estimating that Eden, itself will need only a quarter of the green power generated.  The other three-quarters would feed back into the local community/National grid and possibly, supplying 10% of England’s future electricity needs.

   I wasn’t able to find information about the actual construction of the biomes or how they maintain suitable temperatures for plants and people.  And having no knowledge of power generation, I don’t know if there is even a need for thermal energy storage  in such a park that’s powered geo-thermally.  But I’m sure the power needs for Eden are immense and they seem to be headed in the right direction.

http://rgees.com/index.php

dome, di dome, dome

     I’ve been looking at a lot of greenhouses.  I’ve decided my favorite ones on the market are “Growing Spaces,” created by a couple in Colorado who began their venture 20 something years ago.  These greenhouses are beautiful.  They are essentially dome structures, well built and well insulated.   I assume the majority of people who own these greenhouses are using their indoor pool of water as their thermal mass to store the sun’s heat.

    So, I was recently reading one of the articles on their blog and someone asked what winter temps the dome would be able to endure if one were to install solar water heat exchangers.  They answered that with the solar hot water addition, the inside of the greenhouse could maintain temps 50 degrees (Farenheit) warmer inside than out.  This is truly significant when you’re talking about growing plants and veggies.  Think you can’t make this any better?  But you can.

    Regardless of whether you feed the hot water into piping underneath the dome or back into the indoor pool itself, using PCM in the hot water tanks can store the heated water for longer periods of time and you could probably downsize to smaller storage tank as well.

    This is how it would work.  Your solar hot water heat exchanger heats the water during the day when the sun is out.  I’ve seen solar collectors that follow the direction of the sun to receive optimal light.  But as soon as the sun goes down and the water cools, there is some kind of backup generator that switches on or other alternative heating source to keep the water warm in order to heat the greenhouse.  If you put PCM of an appropriate temperature  into the storage tanks, it will conserve the sun’s heat for a longer duration.  And to top it off, you’d be saving money and fuel due to less usage of your backup heating source.  Again, totally advertising here, but this basic idea of utilizing PCM to store heat is feasible with ANY solar hot water system.

    Check out these geodesic domes.  Wish I had an extra $15,000 laying around…

    This doesn’t have anything to do with greenhouses although I’m sure you could use some of his micro-houses for the purpose of a greenhouse (heat storage would still be an issue).  This guy’s clever.  Goes to prove, you can pretty much recycle anything.  

Derek "Deek" Diedricksen featured in the New York Times gives a tour of his “gypsy junker”.

storing the sun's heat...

    I recently developed a personal interest in Greenhouses which led me into a world of structural, glazing, binding, and sealing materials.  Not being much of the builder/designer type, I then, gravitated towards the thousands of different kinds of pre-fab kits.  Most curiously though, my on-line research of greenhouses, directed me straight back into my area of work, which is, thermal energy storage using phase change materials or PCM.
   
    My desire was to build our greenhouse on Mom’s property in Haywood County that currently flourishes with tasty veggies that grow from Spring to early Fall.  So, I thought “how great would it be if we could grow tomatoes and other summer edibles during the cold months”.  I found that if you’re in an area with mild enough winter temperatures and can get away with just a passive solar system, you still need some sort of thermal mass to keep the warmth through the night.  A greenhouse is just a big solar collector.  And as with all solar heating systems, they share the same problem.  How do you store the sun’s heat for later use at night?  PCM based thermal energy storage systems is the answer, of course.  Back to greenhouses.  Savvy gardeners have been successfully using all sorts of materials for thermal mass; the most common being, barrels of water, rocks, concrete, bricks, tiles, wet dirt and basically, any mass that stores heat.  These materials are all heavy, bulky and take up a lot of the greenhouse space that could be utilized for growing space instead.
   
    If I were not a small business partner of a company that produces PCM, and just wanted to build a greenhouse for my family, I would probably ask such questions as:

--how does the PCM store thermal energy?
--how much PCM is needed?
--what temperatures would be appropriate?
--what is the cost?
--how is it installed?
--what are the advantages and disadvantages of PCM next to the other types of thermal mass?

    There are many factors and variables to consider.