Solar Greenhouse Notes

Solar Greenhouse Notes
1. Insulate north facing wall
2. Insulate your foundation’s outside perimeter with Styrofoam board- 1"-2" thick; placed vertically and extend down to a minimum of 1 foot
3. Dense thermal mass material in which to store the incoming solar heat:
     Use dark colored oil drum filled with water along the north wall (pain white in summer to reflect light/not over heat house) pg 27
4. To help the plants grow, paint/cover everything (except thermal mass) white
5. "A night curtain is an option for people in very cold areas. It is not for everyone. A night curtain is usually an insulating cover you roll across the inside of the greenhouse glazing at night like a blanket to prevent excess heat loss." (author is skeptical)





Source: 
http://www.greenhousegarden.com/energy.htm cited book:

Greenhouse Gardener's Companion, Revised: Growing Food & Flowers in Your Greenhouse or Sunspace by Shane Smith

Science behind the greenhouse:
The determining energy characteristics of the solar greenhouses are as follows: maximal solar radiation input to the greenhouse; minimal heat losses; maximal storage of the heat of the solar radiation energy entering the greenhouse.


Scholarly article: Raising the Efficiency of Solar Greenhouses
http://www.springerlink.com/content/a73666h334u25260/fulltext.pdf

Update: Hybrid System

Hybrid System:
Thermal Mass, insulation, and insulating curtains for overnight use


Thermal mass: metal oil drum filled with water
approx 300 gallons of water according to:
http://www.greenhousegarden.com/Material%20properties.htm#Suggested%20Gallons%20of%20Water%20(thermal-mass)%20to%20Assist%20with%20Solar%20Heating%20of%20Greenhouses


To cover the north facing wall, would need approx 100 sqft of material
possible material: "Reflectix" found at Home Depot (approx. $60)
Night curtain: mylar material- still need to figure out a working design


**need a self sustaining (solar?) fan

Meeting with Professor

Last week Ritesh and I met with a MechE professor about pyrolysis and these are some of the notes I took:

-He recommends a gas-to-gas heat exchanger to heat the greenhouse- closed circuit; 2 loop

-The problem with using biochar is that it would be difficult to maintain-- the oxygen to fuel ratio has to be just right to have a successful stove

-Highly recommends an opaque curtain to be used overnight

     *Planning on using Mylar

Research

Stove Notes:

article: "Improved...Stoves" by Bill Stewart

-Make the combustion process as efficient as possible

-Heat transfer to room should also be as efficient as possible

Analysis of Bagasse: Carbon (48); Hydrogen (6); Oxygen (46)

Analysis of Peat: Carbon (60); Hydrogen (6); Oxygen (32)

Combustion heat value of Bagasse: 19.26 MJ.kg

Combustion heat value of Peat: 23.3 MJ.kg

Three main modes of heat transfer= Conduction; Radiation; Convection

Info on heating:

Calculate heat system capacity

http://www.wvu.edu/~agexten/hortcult/greenhou/building.htm#Heating

Insulation:

[The Walnut Hill Greenhouse will be oriented North-South]

article: "Effect of greenhouse design parameters on conservation of energy for greenhouse environmental control" by Gupta & Chandra

This study was for greenhouses in the north Indian cold climatic region.

 "The use of night curtains reduced the night time heating requirement by 70.8% and daily requirement by 60.6%... An internal rock bed thermal storage/retrieval system met the remaining heating energy requirements of the energy-conserving greenhouse."

"Hartz et al. [11] found that a prototype greenhouse (5.5×9.0 m) with a reflective wall (Plywood painted with a highly reflective white coating capable of reflecting 93% of incident radiation) with a conventional greenhouse, required 14% less energy for heating between October and March"

Performance improved when the northern wall was opaque.

Recommends north side insulation & the experiment had a transparent southern side

Thermal screens/night curtains:

"70% heat conservations can occur in greenhouses with night coverings

The greatest savings of (more than 50% at night) were obtained using a double layer of the non-woven polyester material, floratex 80, aluminum-backed air cap (bubble film) and a double layer of black polyester film.:

 "night time heat loss from a double acrylic greenhouse could be reduced by 60–70% with a polystyrene pellet shading system"

Basically: it was "reported that just drawing any screen during the night resulted in energy saving of at least 20%."

Research

Mylar material- My thinking is that we would put this mylar material on the roof of the Greenhouse to capture the heat from the sun, not letting the heat escape.


I was also thinking of putting this material as blinds on a window but the material would be on the roof. If the Greenhouse gets too hot, pull off the mylar and let the Greenhouse "breath" if you will.


Mylar is available for $50 at Home Depot.
" It is reffered to as aluminized mylar and is readily available commericially. The upper lateral margins of surfaces are desginated by the numeral. The ourvature at margins is such that all radiant engery passing though transparent top adjacent margins will be reflected in the general direction of apex. This is true regardless of the angle at which the light enters and strikes margins."("Solar Collector." Google Books. <http://www.google.com/patents?id=Lwg8AAAAEBAJ>)

The mylar will capture the rays of the sun while containing the heat within the Greenhouse. The "blinds" idea came about to solve the problem that if there is too much heat within the Greenhouse someone can roll up the mylar, and allow the structure to cool down.




For the Biomass oven, the best way to go about this is to buy a funnel that has a sifter that is attached to the bottom. The Biomass will drop within the oven at a certain rate and at the same time the oven will have a sifter and the ashes of the char will drop within a bucket that can be dumped out every morning. 

Biochar

How much heat does pyrolysis produce?

33,320 to 42,00 kj/M&sup3

The following benefits occur with additions of biochar

• Enhanced plant growth
• Suppressed methane emission
• Reduced nitrous oxide emission (estimate 50%) (see 5.10 below)
• Reduced fertilizer requirement (estimate 10%)
• Reduced leaching of nutrients
• Stored carbon in a long term stable sink
• Reduces soil acidity: raises soil pH (see 5.01 below)
• Reduces aluminum toxicity
• Increased soil aggregation due to increased fungal hyphae
• Improved soil water handling characteristics
• Increased soil levels of available Ca, Mg, P, and K
• Increased soil microbial respiration
• Increased soil microbial biomass
• Stimulated symbiotic nitrogen fixation in legumes
• Increased arbuscular mycorrhyzal fungi
• Increased cation exchange capacity

 One method is to use a 55 gallon "jug" and fill that to make Bio char. Thats one way to do it.

Thermal Mass Wall Idea

In the winter: Allow thermal mass to absorb heat during the day from direct sunlight or from radiant heaters. It will re-radiate this warmth back into the home throughout the night.(PASSIVE SOLAR DESIGN - THERMAL MASS)

In the summer:

Allow cool night breezes and/or convection currents to pass over the thermal mass, drawing out all the stored energy. During the day protect thermal mass from excess summer sun with shading and insulation if required.(PASSIVE SOLAR DESIGN - THERMAL MASS)

The denser the material is the higher the thermal mass is.

Some material that can be used:

Water, Concrete, Sandstone, Compressed earth block, Rammed earth, FC sheet(compressed), Brick, Earth Wall (adobe), AAC

The type of material that you use for the thermal wall is very important, has to be at least 110 to 230 mm thick.

The thermal wall can be very expensive and labor intensive.

"PASSIVE SOLAR DESIGN - THERMAL MASS",  Sacramento: California Energy Commission , 2006. http://www.consumerenergycenter.org/home/construction/solardesign/thermal.html

Classification Trees & Conceptual Design

Classification Trees

Conceptual Design

Decision Matrix

Specification	Weight	1 Solar	2 Solar	Wind turbines	Biomass (Pyrolysis)	Thermal mass wall
Cost	5	2	2	1	5	1
Size	4	4	1	3	4	1
Durability *	5	3	3	1	2	2
Safety	3	4	4	5	3	5
Availability	5	2	2	3	5	5
Education	3	4	4	4	5	5
		18	16	17	25	19

Ranking: 1= least favorable     5= most favorable

Solar 1: panels on fruit stand
Solar 2: panels on/next to greenhouse
Wind Turbines: on top of greenhouse
Biomass: oven inside greenhouse, use waste from farm


Durability: how long will it last
Safety: risk to people
Availability: able to create power all year long
Education: use to explain to high schoolers, good learning opportunity
(+maintenance)