Greenhouse reading By Eliot Coleman

 

 

 

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Taken from, “The Winter Harvest Handbook”

Inner Mongolia in the news: “heavy security”

http://www.bbc.co.uk/news/world-asia-pacific-13592514

Tibetan Agriculture

http://www.tibet.net/en/pdf/diirpub/environment/4/chap-3.pdf

Passive Solar Greenhouse: Design Criteria

From RD:

This is a basic overview of the greenhouse section of the book. I wasn’t able to post it to the blog or couldn’t figure out how. The examples for the greenhouses were typically A-frame construction or a slight modification, which allows for the largest southern exposure glazing wall. I believe the A-frame configuration would be a the most efficient approach to the construction and we would be able to incorporate the basic ideas of thermal storage outlined below.

• The greenhouse should be elongated along the east-west axis.
• The north wall should be opaque and consist of 2-3 inches of insulation.
• Making the back wall a light color will allow for reflective backlighting of the plants to encourage vertical plant growth.
• The southern wall should consist of double-glazing for maximum increase in indoor temperature.  A tilt of 40-70 degrees form horizontal is recommended.
• The greenhouse must contain enough thermal storage mass (http://en.wikipedia.org/wiki/Thermal_mass) to decrease temperature swings from day to night.  Masonry or rock walls alone are not sufficient to provide an adequate thermal mass, therefore water storage is recommended.  The volume of water may be related to the area of southern glazed wall. This ranges from 0.33 – 1.33 cu ft of water (1 cu ft water = 62.4 pounds or 7.48 gallons) for each square foot of glazing surface with temperature fluctuations of 40 – 20 degrees F respectively, i.e. the more water storage in the greenhouse the lower the temperature fluctuations.  The storage tanks should be a dark color and be exposed to absorb sunlight. Rock piles may also be used when water tanks are unavailable.

Mazria, Edward. (1979). The Passive Solar Energy Book: Expanded Professional Edition. Emmaus, PA: Rodale Press.

Greenhouse: Mountaintop Montessori School

As an example to reference for “kit” greenhouse a team member went to the greenhouse at the Mountaintop Montessori school located in the Pantops area in Charlottesville, VA.

They used this company:   Check out their website!

http://www.geodesic-greenhouse-kits.com/about_our_greenhouse_company.php

Volunteers at the school built it themselves – (mostly – one father owned a contracting company that helped with the heavy dirt moving and some construction)  It was a very functional and interesting looking design.  I was told they built it with about 5 volunteers  every weekend for about 2 1/2 months.  They leveled the ground and placed a landscaping film over it with gravel on top and a more fine gravel in the interior.

the structure is made of polycarbonate – their standard is a double pane and they come in many sizes.
3 important things I learned from this visit =>

1.  we have not discussed the triangle as the strongest shape to work with it would be nice to keep triangular shapes in mind as we think about stability
2. these greenhouses are “smart” and temperature regulating.  this is something that people can do too (instead of the automatic window opener)
3.  A key concept of their design is a HUGE water tank.  Since one site of interest has geothermal resources it is something to consider.  We could make a small tank and have an interior heat source.

Cool stuff to think about.  The company’s designs work in high altitudes in the Rockies.

Whole Bottles with Wire

Date of Testing: April 21

Here are images from recent testing using whole bottles with embedded metal wire.  The thought is to have a more simplified construction unit that would be attached to the structure using steel or copper wire or mesh.  The technique would use less energy since it’s a lower melting temperature to just collapse (slump) the bottle.  The bottles could then function as tiles or perhaps slumped into a hemi-cylinder shape aka italian roofing tiles.

Explanation of results (From Bill)

• Overall, the technique seems worth pursuing… especially with wire mesh and using multiple bottles.  There was a crack on the sample using this technique and the bottles only partially joined to the mesh.
• The bottles did not crack with the rapid heat to slumping temperature (something I was wondering about).  I thought there would be more cracking from the steel wire (due to incompatible coeff of thermal expansion).
• Labels burned off cleanly for the most part, except where ash is captured by melted bottle.
• You can see slaking (heat corrosion on the wire samples). Corrosion
  reduced the wire diameter.  We’ll need to assess strength and evaluate
  how long the mesh would last outside.

Further testing:

• Testing with slightly higher temp on the mesh sample to see if bottles can better capture mesh- you can see mesh is only partially captured in the sample shown.  Also, worthwhile to test efficacy of forming the hemi-cylindrical shape for the italian roof idea.
• Still working on shortening the time for a full kiln firing.

Bottle Arrangements

Interesting Bottle Arrangements for a greenhouse!

Source: http://inspirationgreen.org/plastic-bottle-homes.html

Plastic bottle greenhouse on Blue Rock Station, Ohio

This one sits on old tires and is made from 1000 2-liter plastic soft drink bottles.

Energy-efficient Greenhouses

This is a project from the STS: Interdisciplinary Food studies 2011 J-term class in UVA about how to make greenhouses more energy efficient. Their research could be helpful as we think about the greenhouse for Hasu Shivert.

Researchers for Project: Rebecca Clemo, Hershil Patel, Andrew Revelle, and Benjamin Fitts

Final Project video: http://www.youtube.com/watch?v=BgkOegSwD2s

Executive Summary: 

Background :

A greenhouse provides a warm environment to help plants grow and is most helpful during the cold winter months. During the daytime, a greenhouse gains heat from the sun’s rays; light comes in through the plastic or glass walls and is then contained inside the plastic insulation. As long as the sun is out, this keeps the greenhouse well above fifty degrees Fahrenheit. However, when the sun sets and the temperature drops, the greenhouse begins to lose heat. To account for this, another source of heat is required to keep the greenhouse warm throughout the night. Heaters powered by gas, such as propane, are effective at warming the greenhouse but are often expensive. Because a plant’s root temperature is more critical than its leaf temperature, it is not cost effective to pump warm air to the ceiling of the greenhouse. As such, greenhouses need a more cost-effective and energy efficient method of supplying warm air to plants. We developed solutions to help reduce these heating costs, with a specific focus on the propane-heated greenhouse at the Local Food Hub’s educational farm in Scottsville, Virginia.

What the project does

Our project seeks to decrease the energy costs of heating the Local Food Hub’s greenhouse. We began by conducting preliminary research on how a greenhouse works and sustainable solutions to mitigating heating costs. This research provided us with baseline knowledge as well as many possible design solutions to explore. These solutions included thermal materials to retain heat, increased insulation, solar power, solar hydronics, wind energy, thermal blankets, methane gas digester, vermiculture, phase change materials, and geothermal heat sources. We provide a full list of these solutions and a short description of each in our “Checklist for Improving Greenhouses.”

We then visited the educational farm in Scottsville to investigate the Food Hub’s greenhouse and discuss design solutions with the farm manager. The manager Steve Vargo gave us a tour of the farm and graciously answered all our questions about their greenhouse. The greenhouse is a 110’ by 45’ structure consisting of a metal frame and plastic walls. The walls themselves consist of two layers of pliable yet sturdy plastic containing a layer of air in between to provide insulation. Currently, Steve uses propane gas to power a heater inside the greenhouse that warms the structure at night. The farm typically spends between $3,000 and $4,000 on propane per year.

We then discussed ideas for modifying the greenhouse. Steve explained how, because the Local Food Hub is only in its second year, the experimental farm has dozens of new projects that require his attention. He advised us to be creative but to strive for solutions that do not require constant manual labor. Despite financial constraints, Steve explained how he had used grants to help pay for other projects on the farm. Steve also explained his biggest concern with the greenhouse: trees that cast a shadow over the greenhouse from sun up until 9 am. This limits the amount of sunlight and heat the greenhouse absorbs in the morning. Steve suggested the idea of cutting down a portion of these trees to allow full morning sunlight to reach the greenhouse.

We came away from our visit to the farm with a focus for our project and an understanding of the needs of the Local Food Hub’s farm. Steve’s ingenuity and flexibility in trying new ideas inspired us to develop solutions beyond what we found in our research. We narrowed our solutions and further researched the more viable ones. We also decided to film a short video to discuss greenhouse management and depict our design solutions for the greenhouse. The video is an artful presentation of our design solutions to Steve and the Food Hub.

Conclusions

The key factors in shaping our solutions were cost, difficulty to implement, and effectiveness. The 7 solutions presented, which are not necessarily exclusive of one another, are generally organized by cost.

The cheapest solutions are the electric blanket, water barrels, waterbed, and removing trees. The electric blanket solution places a household electric blanket beneath the plants, eliminating the inefficient process of pumping warm air into the greenhouse that ends up near the ceiling. Disadvantages of this technique include needing multiple blankets, electricity costs, and keeping the blankets (that are designed for household use) in working condition. Water barrels placed around the greenhouse would heat up during the day, providing an additional heat source during the night. A waterbed would work the same way but would provide direct heat to the plants’ roots. Finally, removing the new-growth pine trees from around the greenhouse would improve solar gain in the morning hours. Losing these trees would not affect the environmental stability, but rather restore the land to its state before the trees were planted.

The more involved and expensive solutions are solar hydronics, a thermal blanket over the roof, and additional structural insulation. Solar hydronics involves pumping warm water through a series of pipes placed beneath the ground. A thermal blanket over the roof would provide heating insulation at night, but could be retracted during the day to allow for sunlight to enter the greenhouse. Finally, insulating the walls of the greenhouse that receive little sun exposure would trap warmth without sacrificing heat gain during the day. Unfortunately, all three methods would require significant labor to install and cannot practically be done by one person.

To conclude, the methods most suitable for the Local Food Hub are the inexpensive ones. Because there was not an opportunity to evaluate the solutions, these alternatives could be evaluated by the Local Food Hub on their own time. In general, the local food movement is not characterized by significant capital. As such, it is likely that the more inexpensive solutions will also be the most popular. This project suggests that there are methods of providing heat directly to the plants’ roots that are cheaper than heating an entire greenhouse with traditional methods, such as propane gas heaters. The more complex methods are more practical when they can be integrated during the initial construction of a greenhouse.

Information on resources/electricity

Electricity: HASU Shivert is connected to 35KB central electricity grid 24/7 (AC380/220V)

Kilns: No available in Mongolia

Resources in the Area (could be utilized for our Project):

• Bottle waste repository on site
• old greenhouses
• possibly use scrap metals/materials from abandoned buildings?
• Beetle wood

Other materials:

• Concrete- Some can be found in Arkhangai, some not depending on what kind of concrete might be needed
• Cement- Available in Arkhangai
• Sand- Can be found in 1-5 km
• Planting dirt- Soil is very good quality soil for any type of vegetable growing
• Ground cover/grasses- Available in Arkhangai
• Wood- Should be fine (need type, size, quantity)
• Shovels- They have
• Welding tools- They have
• Rock- Available in Arkhangai
• Truck – They have a truck
• Steel I-beam- Cannot be found in Arkhangai, should be bought in UB (need size, quantity)
• Screws- Should be bought in UB (need type, size, quantity)
• Nails- Should be bought in UB (need type, size, quantity)
• Nuts- Should be bought in UB (need type, size, quantity)
• Bolts- Should be bought in UB (need type, size, quantity)
• Saws- Should be bought in UB
• Power diamond saw & replacement attachments- Should be bought in UB
• Wheel-barrows or earth movers- Should be bought in UB
• Gloves- Should be bought in UB
• Glass bottles (amount up on the hillside and near the camp, amount in vicinity, amount in soum center)
• The market has many types of bolts, screws, I beam stills, angle stills etc.

Brainstorming Page

Brainstorming Page for things to do before we leave for Mongolia:

• Visit recycling plant here.
• Check out greenhouse prototypes here in Charlotesville (Montessori Greenhouse in Pantops)