Radiant Roots

Phase 2: Research/Develop

02.01 Narrative Analysis / Project Viability 

Our product is a possible solution to food insecurity. Food insecurity is a major problem in North Carolina, As more than 1 million people experience food insecurity. The majority of those people who experience food insecurity come from rural communities due to the few resources and transportation.  Our product attempts to combat this problem. Our product is a self-sustaining garden that will allow for little human input, while also providing produce to people. Our garden may not be needed in urban areas but would be very beneficial to rural areas as well as to low-income communities. We firmly believe that making this product will help those suffering from food insecurity. 

The self-sustaining garden (SSG) has many electrical tools. The main energy source for our product is solar panels. Working with solar panels can be dangerous and complex. But we will ensure to carefully work with solar panels. Our garden also is designed to have timers, therefore, there will be a lot of electrical movement. We plan on making this garden as safe as we can with safety features. We also intend to make the design simple for people and very little input from them. There are many things that can go wrong with our product, we need the timers to work, and we need the irrigation system to be functional and powered by solar panels. On top of this, we also need to make a comfortable environment for the plants to grow. 

Our product is not a product that can be bought rather we are a non-profit organization that intends to put these gardens in rural areas and low-income communities. The main reason we think this is useful and important is because the self-sustaining gardens will allow these communities to have easy access to produce and a higher chance to live a healthier life. Eating garden vegetables rather than store-bought is proven to be healthier. So far, the materials are expensive but in the future, we would like to make these gardens cheaper and easily accessible for everyone.  This product can be created in factories and easily distributed. The materials are easily accessible we hope to make an easy design to build. 

So far our team has been able to meet deadlines. So far we have tried to work ahead to meet deadlines and if there is any feedback or criticism beforehand, we try to fix anything we need. We have a complete team. Although not everyone has experience with the different aspects of this project, each of us brings something to the team. Julian has experience with solar panels, Alejandro and Nolan have been on top of documentation. Angel has experience with greenhouse. Our prototype is likely to be a miniature version of what we intend for our final product to be, we also plan to include what we want this product to be in the future.

02.02 Research Book

Book Title and Summary

The Year Round Solar Greenhouse: How to Design and Build a Net-Zero Energy Greenhouse

Fresh, local nutrient-dense fruits and vegetables are hard to find in winter in cold climates. Growing warm-weather crops like tomatoes, bananas, avocados, and other perennials is nearly impossible using conventional structures. The solution for millions of backyard and small-scale commercial growers is self-heating solar greenhouses. The Year-round Solar Greenhouse is the one-stop guide to designing and building greenhouses that harness and store energy from the sun to create naturally heated, lush growing environments even in the depths of winter, covering principles of solar greenhouse design and siting, glazing material properties and selection, controlling heat loss, ventilation, and construction methods. Additionally, an in-depth section covers sustainable ways of heating the greenhouse without fossil fuels, including using thermal mass and storing heat underground with a ground to air heat exchanger. Variations include attached solar greenhouses, earth sheltered greenhouses, plus integrating hydroponics and aquaponics. More than a dozen case studies from across North America provide inspiration and demonstrate specific challenges and solutions for growing year-round in any climate. Grow your own food, anytime, anywhere using the power of the sun!

Book Annotations

Nolan Hunter

Section I

Chapter 1: 

• What is a Solar Greenhouse: 

  • Greenhouse uses the sun’s energy not only for growth but also for passive heating, maintaining suitable growing temperatures without reliance on fossil fuels. 

  • During the day sun is used for heat and growth with greenhouses and at night, most greenhouses quickly lose all that heat due to the poor insulation qualities of the materials. 

  • During the winter, a normal unheated greenhouse is slightly warmer than the outdoor temperature. Unless it’s ventilated or artificially cooled, the greenhouse traps enough heat that it can overheat. 

  • A tent offers limited protection and insulation which can overheat during the day if uncontrolled and heat is let out at the end which can result in wild temperatures that can stress or kill plants. 

  • The inefficiencies relate to the principles of the design. Traditional greenhouse design focuses on maximizing light by maximizing glazing. 

  • Glazing is for any light-transmitting material, like glass or clear plastic.

  • Traditional greenhouses are normally 100% glazed. 

  • Glazing materials are extremely poor at retaining heat.

  • During the summer, solar greenhouses had comparable efficiency to fully glazed structures. 

Chapter 2:

• Growing Indoors: History and Future Trends 

  • During the Roman Empire, the doctor of Emperor Caesar ordered him to eat a cucumber every day, and to provide this vegetable, growers had a strategy of growing the vegetable underneath thin layers of a translucent stone (mica) to protect the crops. 

  • 1400 years later, a greenhouse was created and developed. 

  • North American Greenhouses mimicked the European designs. The difference was North America had harsh winters and higher light levels. 

  • After WWII, there was more development for the greenhouse designs. 

  • Solar gardens haven’t caught on because of reluctance with the greenhouse.

  • Fossil fuels have been thought of as not usable in current years and solar greenhouse production is catching on. 

Chapter 3:

• Planning for the Greenhouse

  • Solar greenhouses are designed to stay warmer than outdoor temperatures, which enables growers to grow and experiment with crops normally ungrowable in their climates.

  • Hoop houses all provide a single layer of crop production and are normally used as season extenders.

  • There are different season structures for solar greenhouses for winter, summer, and other seasons. During the winter, some greenhouses can get close to frost to enable cold-tolerant vegetables and plant-organism growth. 

  • Some hothouses can permit the growth of heat-based crops and these greenhouses require more insulation, multiple layers of glazing, and significant thermal storage. 

Section II

• To maximize light year-round and particularly in the winter, greenhouse glazing should mainly be facing the sun and south if in the Northern Hemisphere. 

• Solar greenhouses normally have long rectangular shapes, with the long, glazed side facing south.

• Morning light allows greenhouses to warm up faster, reducing stress on plants.

• The angle of elevation and azimuthal angles are used to locate the direction of the sun.

• Permits are normally required for extension greenhouses and commercial greenhouses.

• Chapter 5:

  • Light quality is used to describe the spectrum of wavelengths, or color, which can be affected by a glazing material.

  • Lumens measure the intensity of the visible spectrum. Calibrated to measure the wavelengths we are most sensitive to. 

• General Notes:

  • Greenhouse shape, Climate, and Summer heating. 

  • Different fans

  • Shade cloth is a simple, low-cost, highly effective alternative and during warm months the cloth can prevent potential overheating. 

Alejandro Herrera

Section 1 (THE BIG PICTURE) 

1. “On a winter morning, a standard unheated greenhouse usually is only a few degrees warmer (if at all) than the outdoor temperature. Moreover, unless it is ventilated or artificially cooled, a standard greenhouse traps so much heat during the day that it will drastically overheat” (Schiller 2).

1. These here raise valid concerns about greenhouses, especially when it comes to more extreme temperatures such as it being too hot outside causing the greenhouse to overhead, or if its winter the greenhouse being too cold. This shows the importance we need to take into out design about how we will handle extreme temperatures in order for our product to be able to thrive. 

2. “Designers use glazing strategically , placing and angling it to maximize light while reducing the glazing area as much as possible to minimize heat loss” (Schiller 4).

2. Glazing, as decided in the book, is a term that relates to the idea about being a term relating to light transmitting materials, such as glass or plastic. In terms of greenhouses, any glazing materials have to be placed strategically to not overheat a greenhouse, but also minimize heat loss, this of course is something that we should keep into consideration for our product. 

3. “Greenhouses can include solar panels to generate renewable electricity; however, a much wiser use of the sun’s energy for heating is through passive solar design” (Schiller 5).

3. Almost ironic in a way as this book says for greenhouses solar panels aren't the best way to go about having a greenhouse, which may seem to go against what we are trying to do. But, this isn't entirely going against what we want, as we aren't really building a big greenhouse nor are we building something meant to be worked on by a person as we want our item to be self-sustaining. 

4. Active and Passive Solar Greenhouses (Schiller 5).

4. I wonder if there is a definitive way, which yields the best results, for a greenhouse. I.E. Going the active way or the passive way to maintain a greenhouse. 

5. Principle 4 (Maximize light and heat in the winter) and 5 (Reduce light and heat in the summer) (Schiller 6).

5. These are both principles that are important and worthy of discussion, we as a group do need to think of an effective way to do both these things if we want our community garden to actually be able to last year long and not during specific months of the year. 

6. “Though greenhouses created a local food supply, they increased the total demand for fossil fuels” (Schiller 10). 

6. It's an interesting thing to note, what one would assume would help the environment, greenhouses, only actually end up harming the environment more through its overuse of fossil fuels. 

7. “The energy savings of an insulated north wall, for example, become much lower when the square footage of the greenhouse is increased by a factor of one hundred. Thus, part of it has to do with the predominant system of growing monocultures at immense scales, rather than distributed growing in smaller farms” (Schiller 14-15).

7. In a way this has me a bit worried, our item is exactly like this in the fact it's supposed to be a more energy efficient product, but very much smaller compared to large less energy efficient greenhouses. Because of the fact our product is smaller, does that mean it won't be a popular product to use if it was released to the public? 

8. Page 21

8. This page discusses different types of greenhouses found in different areas of the world. This makes sense as different places in the world can have vastly different weather. Our project is focused on NC, so really we only have to worry/think about the type of weather here, but what if we did try and make this a world wide type of product? Would we need multiple different designs to fit with other weather types from around the world? 

9. Page 22

9. This page is overall just a great page to keep tabs on as it allows the reader to determine the climate in the area they live in, very helpful information for us to then in turn determine the climate found in our area. 

Summary

Overall this first section was really just an introduction section. It allows the reader to gain a basic understanding as to what greenhouses are, what different types there are, and why we need ones that actually help keep the environment healthy and not harm it. As the section describes there are many examples of greenhouses out there that instead of actually being beneficial to the environment, harm it due to the overuse of fossil fuels, which is why the author heavily advocates for passive greenhouses as they rely more on the sun and less on electricity. Aside from that the section also goes a bit into the history of greenhouses and how to even make/startup one. Everything from this section will definitely prove to be useful for us as a team as we continue to develop our product. ______________________________________________________________________________

Day 2 Annotation

1. “North America, 85%–90% of solar radiation comes from the south” (Schiller 29)

1. This is just an important thing to keep in mind as we work on our on project. When it comes to actually testing our product and putting it down somewhere we need to keep in mind that if we want the suns energy, we of course need our product to face the South. 

2. “A compass is needed to identify due south at your site” (Schiller 32)

2. This is yet just another thing to keep in mind as a group as orientation is an important thing we should remember to work on while working on our project and a compass would be a really effective tool in terms of making sure our product is oriented correctly. 

3. “Azimuthal angle” (Schiller 34). 

3. An unknown term to me, but what this essentially  means is simply the angle of the sun on the horizon due North and what makes this important to note for a greenhouse is this is what's able to explain the position of the sunrise and sunset each day. 

4. “The best shading obstructions are deciduous trees that drop their leaves in the winter, providing light when you need it, but shading when you don’t” (Schiller 35-36). 

4. Potentially a solution to a problem we have in which during the summer seasons it could be too hot, instead of wasting resources buying a fan for our garden we use a tree like this i.e. placing our garden near this type of tree to provide shade from the heat during the more hot months. 

5. “Permits are typically required for attached greenhouses…commercial greenhouses” (Schiller 40). 

5. Greenhouses typically require a permit, what this means is we as a group should consider and look into if our product would need a permit to be put into an area. Our product is not a greenhouse but more-so a garden bed, despite that, do we still need a permit if we want to place our item into a community? That is something we should research further into. 

6. “If you have 10 square ­meters of solar panels on your roof, and the panels are 15% efficient, you could estimate that the panels would produce 1,500 watts” (Schiller 44). 

6. While I admit this isn't something I understand too much about, this is something we as a group need to look more in depth about, our whole project is about solar panels so what that means is that as a group we need to consider how much energy we want our solar panels to be producing each day for the garden and where that power is then split up too. 

7. “a DLI” (Schiller 45).

7. This was an unknown term for me, but essentially from my research I found out it means “Daily Light Integral” which is just the photosynthetically active protons, this is different for every plant and is something we need to consider as a group when it comes to what we want to actually grow in our product. 

8. “Don’t crowd plants” (Schiller 48).

8. Considering our product is a smaller replica of what we actually want to build, we might have to reduce the amount of plants we grow in order to prevent them from being crowded. 

9. “Considerations When Choosing a Glazing Material” (Schiller 49). 

1. This is a potential decision matrix to be made with our group as we figure out what potential glazing material we should include for our product as there are multiple different types of them with their own pros and cons.

Julian Echevarria Galarza

Chapter 1: Pages 1-10

• Section 1 (What is a Solar Greenhouse?):

  • Solar energy will not only help the carbon footprint of the greenhouse but also help with energy efficiency in heating.

  • Passive solar design: The practice of using solar energy for heating without relying on any electrical or mechanical devices 

  • “The term passive solar greenhouse is often used to more explicitly describe a greenhouse that uses passive solar heating and has no electrical components at all— ​so it uses no electricity.”

  • Seven Principles of Solar Greenhouse Design

    • Orient the Greenhouse toward the sun

    • Insulate areas that don’t collect a lot of sunlight

    • Insulate Underground

    • Maximize light and heat in the winter 

    • Minimize light and heat in the summer

    • Use thermal mass

    • Ensure sufficient Ventilation

  • “Made out of double-­layer polyethylene plastic on all sides, the conventional greenhouse served as the control. The experimental solar greenhouse, called the Brace greenhouse, featured an insulated north wall, a double-­ layer plastic south wall and several other efficiency features.”

Chapter 2: Pages 10-18

• Section 2 (History and future trends):

  • While their has been evidence that greenhouse like structures existed during the Roman Empire, they didnt resemble modern greenhouses until the 1700’s

  • “If we were to give this era another name, it could be “pomp and glass.” Greenhouses were not used for serious food production. Rather, they housed exotic plants and served as status symbols for the incredibly rich, or centers of education.”

  • With the creation of polyurethane plastic in WWII, greenhouses become more affordable and allowed for more growers to adopt them into to their produce production

    • Possible goal for greenhouse: uses recycled plastic for covering?

  • If greenhouses have been showed to lower energy cost, why aren’t they more popular?

    • They’re often built as temporary structures

    • Comercial greenhouses are often to large for passive solar energy to be effective

    • “Yet another reason is economic, or cultural, depending on how you look at it. Heated greenhouse operations rely on cheap, fossil-­ fuel heating. Greenhouses have been heated for many years with low-­ cost propane. Until recent decades, there was no major incentive to curtail energy use.”

    • “well. The term vertical growing can be interpreted as growing stacks or trays of plants in single-­story buildings, or multi-­ story greenhouses… However it is applied, vertical growing is part of a trend of maximizing yields in small spaces.”

Chapter 3: Pages 18-26

• Section 3 (Planning for the Greenhouse):

  • Typical Greenhouses simply use heat storage and insulation to increase and temperature for a specific season, while solar greenhouses are designed to function year round.

  • “Understanding Your Climate One of the reasons traditional greenhouses perform poorly in most climates is that they use a “one-­ size-fits-­ all” approach. The same plastic box will operate very differently in Maine than it will in Texas. Solar greenhouse design applies a different mindset: by tailoring the structure to the local environment, one can work with the elements, rather than against them.”

  • For greenhouse function optimization it is important to keep Light and Temprature for your region in mind.

    • Charlottes plant Hardiness is in the “8a” category with a range of 10-15 degresses F (2023 USDA Plant Hardiness Zone Map | USDA Plant Hardiness Zone Map).

  • DLI (Daily Light Integral): Measures light intensity over a period of time.

  • The indoor climate is just as important to consider as the outdoor climate. Some questions to help guide the creation of the indoor climate include:

    • What do you want to grow and when?

    • Why do you want a greenhouse?

    • Have you considered other uses for your greenhouse?

    • What is your time commitment?

    • What is your budget?

Chapter 4: Pages 29-41

• Section 4 (Siting and Orientation):

  • “ Fact: On average, on a clear sunny day in North America, 85%–90% of solar radiation comes from the south; less than 15% is diffuse light coming from other directions.”

  • The two primary features of a Solar greenhouse”

    • South Facing Glaze

    • Insulated North Wall

  • To increase solar gain, maximizing the south-facing dimensions should be the top priority of construction. Usually, a greenhouse should be twice as long as it is wide.

  • “That means the ridge of the greenhouse runs along the east-­west axis, a common way to describe a greenhouse’s orientation.”

  • Typically, an aspect ratio of 3:1 or 2:1 is most advantageous when constructing a solar greenhouse. Heights of 9’-10’ are also recommended (however this is for much larger greenhouses).

  • For us on the east coast, we should orientate our houses towards the southeast instead of directly to the south in order to maximize the energy collected.

  • Southeast orientation also allows for the maximization of “Morning light” which is more beneficial for plants.

  • “An extra step for precise growers is to use a magnetic field calculator like the one available from NOAA (ngdc.noaa.gov/geomag-­web) to find the ­variation between true south and what a compass will read.”

  • The Solar Path is the trajectory of the sun on any given day, which can be fortunately estimated. The sun's position is affected by:

    • The angle of Elevation: How high the sun is in the sky in reference to the ground plane. It changes depending on the season, with more drastic changes occurring the more you move from the equator. Some important measurements for the angle of elevation include:

      • At Solar Noon: 90 minus the local altitude

      • At Winter Solstice: 23.5 less than the equinox

      • At Summer Solstice: 23.5 Higher than the equinox

    • The Azimuthal angle: The angle of the sun on the horizon, relative to due north. This impacts the location of the sunset and sunrise. Changes from a narrow arc in the summer to a much more wide arc in the winter.

    • Sources that can help track these angles:

      • SunCalc.net 

      • solardat.uoregon.edu

  • Understanding the placement and development of shadows on the site of the greenhouse is also crucial to maximizing the collection of crucial winter light. The best approach is using an elevation gauge and trigonometry to determine the length of the shadows on crucial dates such as the winter solstice. 

Chapter 5: Pages 41-69

• Section 5: (Controlling light and heat gain: glazing)

  • “Historically, greenhouses have given primacy to getting the maximum amount of light possible while sacrificing energy efficiency. Smart greenhouse design relies on using glazing more carefully. By maximizing the light coming through the glazing area, you limit the amount of glazing necessary, allowing for more insulated wall area, and a more thermally stable structure overall.”

  • Plants consume light at around the range that the human eye can detect light, especially benefiting from light that is present within the blue and red spectrum. This light is referred to as (PAR) light.

    • Light quality: The intensity of light.

    • Photo-period: The duration of useable light.

  • When it comes to describing light, it is commonly broken down by what it will be used for. The most common categories are Light for people, systems, and plants.

    • Light for People: “Lumens , lux and foot-­candles all measure the intensity of the visible spectrum. They are calibrated to measure the wavelengths we are most sensitive to. Thus, they are limited tools for measuring light for plants; they don’t measure the PAR spectrum, and they only measure light at a single point in time. Ft-­ candles are useful for comparing light conditions, as shown in Fig. 5.2, and are commonly used to rate grow lights.”

• Light for Systems: “Sunlight can also be measured in watts , a measure of power. Watts can measure the full spectrum, including the IR and UV wavelengths, ­ going far beyond the visible or PAR spectrum. Watts per square meter is commonly used to rate power systems, like solar photovoltaic panels. For instance, on a bright day the total amount of solar radiation hitting the ground is about 1,000 watts per square meter. If you have 10 square ­meters of solar panels on your roof, and the panels are 15% efficient, you could estimate that the panels would produce 1,500 watts, or 1.5 kilowatts at that time (10 square meters × 1,000 watts × 0.15 = 1,500 watts). Watts can be converted to Btus/hour , another common metric for rating the heat gain of buildings (1 watt = 3.4 Btu/hour).”

• Light for Plants: “The most important term for greenhouse growers is the daily light integral (DLI). DLI measures the PAR spectrum (using a unit called a micro­ mole). More importantly, the DLI measures the total amount of light over the course of a day. Conceptually, it’s is like a rain gauge; it combines both intensity and duration (a 24-­hour period) to get a single cumu­ lative metric for light. That makes it very useful for comparing light levels and describing how much light plants need, making it the most common metric in the horticultural industry, and the most helpful one for any grower to use. The first map in the color section shows the average DLI values by month across the US. They vary from 0– 60 depending on location and time of year. By looking at the DLI numbers for your location, you can see the huge fluctuations in light levels. On average in the US, the winter months have only 10%–20% of the light as the summer. Higher latitudes will experience greater variations. This presents the basis for one of the main principles of solar greenhouse design: maximize light and heat in the winter. If a plant that evolved to grow during the long days of summer is in an environment with only one tenth the light levels, there will obviously be repercussions. Transmitting enough light and heat in the low-­ light months is a main goal of glazing in a year-­round greenhouse.”

• The amount of light that plants need is dependent on the type of plants, the necessity of the plants, and the robustness of the growing prospects.

• “Many commercial growers consider a DLI of 12 to be the minimum threshold for good growth of most crops. For high-light crops like tomatoes and peppers, commercial growers often shoot for a DLI of 20. (Many fruiting crops like tomatoes survive given warm temperatures, but do not set fruit in low-light.) However, home growers, and even many commercial growers, can grow year-round with much less light than this, going down to the low single digits of DLI levels.”

• When growing year-round, the most important factor is light, so, to maximize the light collected by the growing plants is is most important to ensure that the crops are continually rotated to crops that are beneficial to the environment they will grow in, as well as:

  • Don’t let the greenhouse overheat in the winter

  • Don’t crowd plants

  • Reflect light

• Cloudiness is another factor that impacts the amount of light in an area at any given time. Some of these conditions include:

  • Clear Days: Create intense direct light

  • Overcast Days: Features uniform cloud coverage, creating diffused light.

  • Partly cloudy Days: Light alternates between several conditions.

• Typically greenhouses aren't insulated and are 100% glazed over structures. However, for efficiency, a ratio of insulation to glazing is necessary depending on the condition of your local. Some ways to remedy this include:

  • Mild and Cloudy: require a larger area of glazing exposed to the sky dome for light levels to be sufficient inside. Optimizing glazing for a specific sun angle or time of year (as discussed below) is less relevant because light is more uniformly distributed throughout the sky dome. Thus, a shallow roof slope and glazing on the south, east and west opens the “aperture” of the greenhouse up to the whole sky. Due to milder temperatures, less insulation is required. Greenhouses may only have the north wall insulated. Or, this is one of the few instances that might justify a fully glazed structure.

  • Cloudy and Sunny: require a larger area of glazing exposed to the sky dome for light levels to be sufficient inside. Optimizing glazing for a specific sun angle or time of year is less relevant because light is more uniformly distributed throughout the sky dome. Thus, a shallow roof slope and glazing on the south, east and west opens the “aperture” of the greenhouse up to the whole sky. Due to milder temperatures, less insulation is required. Greenhouses may only have the north wall insulated. Or, this is one of the few instances that might justify a fully glazed structure.

  • Cold and Cloudy: This is where it gets challenging. Both glazing for light transmittance and insulation are needed. Generally, we recommend using a moderate ratio and ensuring that the glazing has a good R-­ value.

• When placing glaze, it's important to consider areas that are obstructed by shade or other factors. These areas would benefit from insulation rather than glazing.

• When choosing a glazing material, it is important to consider:

  • Light Transmittance: Light transmittance is how much of the available light a material transmits, described as a percentage of indoor light compared to light hitting the outside of the greenhouse.

  • Insulation: Glazing materials are rated by their R-­value, which measures their resistance to heat transfer, or simply insulating quality. They can also be rated by their U-value, the inverse of an R-value. Compared to standard insulation or wall materials, glazing materials are very poor insulators: most greenhouse glazings are below R-­ 3. Importantly, the R-­value is inversely correlated with light transmission— ​ the higher the R-­ value, the lower the light transmission. Thus, choosing a glazing material is often a balancing act between light and insulating quality.

  • Cost: Both upfront and lifetime costs.

  • Durability and UV stability: Susceptibility to snow, wind and hail is an important factor, particularly for harsher climates. Additionally, plastic glazing materials will degrade with exposure to UV rays, some much faster than others.

  • Transparent Vs. diffuse: These two terms are often misused. When glazing is transparent , it allows a unidirectional ray of light through. You can clearly see detailed objects through transparent materials, like glass. However, most glazing materials are translucent : they refract light into many rays (also called scattering, or diffusing the light). Studies have shown that crops grow better under diffuse light conditions because when light is refracted into many rays light, it penetrates deeper into the leaf canopy.

  • Thermal Expansion: Another factor is how the material reacts to dramatic temperature fluctuations (which occur daily in a greenhouse). Materials will expand and contract with temperature swings and shift over time. This, in turn, causes air infiltration and water leaks. The measurement of this quality is called the “coefficient of expansion,” and it is usually specified on a materials spec sheet. If a material has a high coefficient of expansion, this needs to be considered when installing the material; special screws or attachments that allow for shifting should be used.

  • Sealability: How well can the material act like a sleek marine mammal? No, we don’t mean that kind of seal. “Sealability” is how we describe the ability of a material to seal tightly to the frame of a greenhouse.

• The angle of a ray of light relative to the perpendicular is called the angle of incidence, When that angle is 0 (perpendicular) the maximum amount of light is transmitted. (This is about 87% for a single pane of clear glass. The other 13% is reflected or absorbed.) When the angle of incidence increases, more light is reflected instead of being transmitted.

• Importantly, this relationship— ​between the angle of incidence and light transmission— ​ is not linear. For polycarbonate and some other materials, there is almost no decrease in PAR light transmission when the angle of incidence is less than 45 degrees. In other words, as long as the glazing is within 45 degrees of perpendicular, the decrease in light transmission is insignificant. This is true for all glazing materials: going from a perpendicular angle to an angle of incidence of 45 degrees typically reduces light by only 1%–5%. With triple wall polycarbonate, for example, there is virtually no change (about 1%) in light transmission when the material is perpendicular to the sun and when it is tilted 45 degrees away from perpendicular. Thus, as long as you stay away from very shallow roof angles, there is little effect on light transmission due to reflectance. For roof angles at 40 degrees latitude, then, the minimum threshold is greater than 15 degrees.

• To find the perfect range for your location simply:

  • 1. Take your latitude and add 20 degrees to create a perpendicular angle that is most beneficial in the winter months.

  • 2. Subtract 45 degrees from the result of step 1 to find the practical angle of incidence during the winter months.

• When considering glazing angles however, it is important to keep in mind:

  • Greenhouse Shape

  • Climate

  • Summer Heating

  • Snow Loads

• It is also recommended to us more than one glazing material to have variety.

Chapter 6: Pages 69-87

• Section 6 (Controlling Heat loss: Insulation):

  • The purpose of insulation is to reduce conductive heat losses through the surface of the greenhouse

  • The two biggest losses of heat in greenhouses are:

    • Conduction: The movement of heat through a material

    • Air infiltration: When warm air leaks through gaps and lets cold air seep in.

  • Two avoid these and further heat loss, it is important to avoid sitting the greenhouse in windy areas and to caulk all cracks in order to create an air tight structure.

  • Heat loss can be represented with the heat loss formula

  • Insulation and R-values are not linear and only drastically change in effectiveness within lower levels than higher levels. Thus for construction, an R-value of 2 is recommended more than a R-value of 21.

  • Builditsolar.com has a “Home Heat Loss Calculator” which can be used to find these calculations.

  • Across the US, average soil temperatures below the frost line are around 40°F– 50°F (4°C– 10°C). The exact range varies by climate. You can find data for many areas by using the National Resources Conservation Service (NRCS) database, called the Soil Climate Analysis Network (wcc.nrcs​ .usda.gov/scan/).

  • When insulating the roof and walls of a greenhouse it is similar to a house in the materials and implementations used, such as:

    • Batts and Rolls (Fiberglass and Mineral Wool): Fiberglass is ubiquitous in every type of construction for a very simple reason— ​ it is cheap and easy to install. However, you get what you pay for. The “field performance” of fiberglass is much lower than its rated R-­ values because it can easily wick moisture. For that reason, we don’t recommend it for greenhouse applications (because moisture is a constant factor). A similar, but more effective material is mineral wool batts. Mineral wool includes rock wool and slag wool (different materials formed into the same mineral wool batts). In contrast to fiberglass, these batts are semi-­ rigid: they come in boards that are firmer and thus easier to cut and get a secure fit. The R-­values are also significantly higher, at 3– 4 per inch. Finally, mineral wool is more water resistant than fiberglass, making it a viable candidate for insulating greenhouse walls. The drawback is that at the time of this writing it is not as readily available as fiberglass (it must be sourced through distributors or certain retailers), though this is changing quickly as its popularity— ​ particularly among green

    • Rigid Foam Board (Polystyrene and Polysio): Rigid foam board is another very common type of insulation that can be used in walls and underground. Foam board has a higher moisture resistance than fiberglass, giving it better performance over time. There are three types: extruded polystyrene (XPS), expanded polystyrene (EPS), and polyiso. Because that is a lot of “polys” we normally use their non-­ technical names as references. Extruded polystyrene is normally called “pink” or “blue” board due to brands’ characteristic colors. It is very common both for walls and below-­ grade applications. The advantage of pink/blue board is that it has high insulation values for its cost, and it is very moisture resistant. The latter makes it a very good material for using in humid environments like greenhouses and also underground. It’s commonly used to insulate around the foundation of a greenhouse. Unfortunately, it is not the “greenest” material— ​making it creates ozone-­depleting compounds and, as mentioned above, it currently includes a fire-­retardant chemical called HBDC in the US. Using a different manufacturing process, companies also make expanded polystyrene (EPS). Commonly called “beadboard,” these rigid boards are made of a conglomerate of white beads (the same material as Styrofoam cups). Though more sustainable than its extruded counterpart, EPS has a lower R-­value per inch and worse moisto ture resistance. For those reasons, it is less common than pink/blue board for greenhouse applications. Polyiso (full name polyisocyanurate) is another type of rigid plastic insulation. It has a higher inin sulation value, usually R-­ 6 per inch. Though the total cost per board is higher for polyiso boards, the cost per R-­ value is the lowest among rigid inpolyiso sulation products. For that reason, this tends to be our top choice when insulating the walls of the greenhouse, as it has the greatest insulation value per dollar spent. It absorbs moisture slightly more readily than polystyrene, but still has adequate-­toof good moisture resistance. Polyiso boards come with a reflective foil backing. The predominant brand name is R-­Max.

Chapter 7: Pages 87-105

• Section 7 (Ventilation):

  • “Cooling” describes anything aimed at lowering temperatures in the greenhouse, including shade cloths, evaporative coolers, and misting systems. The easiest, most energy-­ efficient method (by far) of cooling a greenhouse is exchanging the greenhouse air with cooler outdoor air (“ventilation”). In addition to cooling, ventilation serves other vital functions that keep the greenhouse healthy, such as circulating air, adding CO2, and reducing humidity.

  • Passive vents: Passive vents rely on devices called solar vent openers to open and close vents. These contain a wax cylinder that expands when heated, opening the vent. When the temperature drops, the wax contracts and closes the vent. The cylinder can be set to operate at a certain temperature (within a set range).

  • When locating vents it is important to keep in mind:

    • Wind Directions At Your Site: Ideally, the exhaust vent should be on the leeward (downwind) side of the greenhouse. Wind blowing against an exhaust vent will impede airflow.

    • Snow and Ice Buildup: Many people consider building exhaust vents in the roof. It’s possible, but much more complicated given that snow and ice can build up on top of a vent and prevent it from opening, possibly breaking the vent opener. Additionally, roof vents create exposed edges where water runoff can leak down into the greenhouse. Roof vents require more careful construction, normally raised above the roofline so that water runs around the lip of the vent, not down into cracks (the same way skylights are installed).

    • Snow Shedding: For intake vents, snow buildup at the front of the greenhouse can be a problem. A vent trying to open into a mound of snow will break. You can disable some vents when they are not needed in the winter; build overhangs into the roof; or go above and beyond, creating special awnings above intake vents to protect them from snow

    • Interior Layout: layout: When locating intake vents, sketch out the location of growing beds or any equipment inside that could block a vent. Typically, intake vents are located in the south wall above the growing beds. In winter, though, plants can be “shocked” with bursts of freezing cold air when the vent opens. To avoid this, consider disabling some vents during the winter. The east and west corners are also good places for vents.

    • High Winds: Vents protruding from the greenhouse have the tendency to act like sails; they can get torn off in wind gusts. Most vents have a “safety cord,” but these are not fail proof. If you are in a very windy location, consider building a windbreak around the greenhouse. Locating intake vents as low as possible and putting exhaust vents on the leeward side of the greenhouse keeps them out of the strongest winds.

  • Exhaust fans offer precise control over the temperature of the greenhouse. They determine when colling is necessary by using a thermostat at plant level which, when a certain temperature is reached, activates the fan. While extremely effective, it creates a lot of noise which can be a detriment. 

  • Using exhaust fans requires three components: a fan, an intake shutter and a thermostat. The fan exhausts hot air from inside the greenhouse to the outside. An intake shutter is a simple vent covered with louvers; it’s needed to provide a source of incoming air when the fan is running. These can be motorized, or they can be allowed to freely flap open when the fan turns on. The motorized versions allow for more controlled airflow (the flaps don’t blow open in a strong wind) but are more expensive.

  • Exhaust fans can be a source of heat loss, so it is recommended to cover them with something during winter months to prevent heat from escaping.

  • There are several backup strategies we recommend to help maintain a healthy greenhouse environment when ventilation isn’t advisable. These include:

    •  Air circulation: is essential for a healthy growing environment, particularly in the winter.  

    • Heat Recovery Ventilators (HRVs): are air-­ to-air heat exchangers, devices that can provide dehumidification and CO2 supply ­ without overcooling the greenhouse. They preheat incoming air using the outgoing air of the greenhouse. The two air channels pass by each other, without mixing, in a box installed in the wall. HRVs work much like an exhaust fan except that, instead of drawing in 30°F (−1°C) air in the winter, the HRV pre­ warms the air to say, 45°F (7°C). In this process, it also lowers the relative humidity of the greenhouse. As the incoming air is warmed, it’s able to hold more moisture, reducing humidity levels. The major drawback is the cost. Most units are over $600 before installation (many much more). Additionally, they tend to have lower flow rates than exhaust fans, so an additional exhaust fan is typically required. HRVs are good extra step for growers who want to provide winter ventilation and humidity control as energy-­efficiently as possible. They also have applications in attached greenhouses in which humidity control is more of a concern.

    • A Ground-­ to-Air Heat Transfer (GAHT): A GAHT system stores heat from the greenhouse in the soil underground. As it does so, it circulates and dehumidifies the air. This is possible because the warm, humid air from the greenhouse is circulated through the cooler soil during the day. The air is cooled underground, and, when it reaches the dew point, the water vapor condenses underground. Perforated pipes allow the water to drip into the soil, near plants roots. In this way, a GAHT system helps take humidity out of the air and moves condensed water into the soil. Though its primary purpose is temperature control, these are great corollary benefits. 

    • Dehumidifiers: forgo ventilation and just provide dehumidification within a closed environment. They are rare in residential applications, but reasonable for commercial greenhouses that require a tightly controlled growing environment. More expensive machines simultaneously dehumidify and heat the greenhouse through a process

Angel Zapata-Dominguez

Section 1: The big picture 

• Chapter 1: What is a solar greenhouse 

  • Seven principles of building a greenhouse 

    • Orient the greenhouse toward the sun  

    • Insulate areas that don’t collect a lot of sunlight 

    • Insulate underground 

    • Maximize light and heat in the winter 

    • Reduce light and heat in the summer 

    • Use thermal mass 

    • Ensure sufficient ventilation 

  • (Glazing is a term for any light-­transmitting material, like glass or clear plastic.)

  • Passive solar design : the practice of using solar energy for heating without relying on any electrical or mechanical devices 

  • The term passive solar greenhouse is often used to more explicitly describe a greenhouse that uses passive solar heating and has no electrical components at all 

  • Solar greenhouses hold tremendous potential as a way to reduce both food miles and fossil-­ fuel use, for commercial and home growers alike. 

• Chapter 2: Growing indoors: history and future trends  

  • the Roman Empire around 30 AD. ­ Harvested food was limited to grains and a few basic vegetables when they were in season. It was around this time that a doctor of Emperor Tiberius Caesar ordered the ruler to eat a cucumber every day for good health. To provide the cucumbers year-round, growers devised a strategy of growing them underneath thin layers of a translucent stone (mica) to protect the crops. That’s the first documented occurrence of a greenhouse-­like structure.

  • Northern European countries with greenhouses, by far and away the largest greenhouse-­ growing country is China.

Discussion Notes

Video Recording Discussions:

• Day 1

• Day 2

Book Reflection:

The book "The Year-Round Solar Greenhouse: How to Design and Build a Net-Zero Energy Greenhouse" by Lindsey Schiller and Marc Plinke provides an in-depth look into the construction and development of a Solar greenhouse and what it means for a greenhouse to be solar-powered. The book is in several sections that dive deeply into crucial aspects of a greenhouse, such as heating, irrigation, sunlight retention, and land position. The book goes into heavy detail for each section, leaving no information from their explanation to provide a thorough look at the process they are highlighting. The book also covers historical examples, highlighting how the specific method or time has evolved and how people have reacted to the process. The book also features an extensive appendix that covers specifics in even more detail, providing mathematical equations and graphs that give validity to the statements from the previous sections.

This book has given my team invaluable insight into what a greenhouse needs to succeed and how to achieve our situation concisely and effectively. Before reading the book, only one person in our group had extensive experience with a greenhouse, with everyone else having only ever heard of a greenhouse or having limited experience with products such as solar panels. With the book's information, we not only understood the importance and the histories of greenhouses, but we also understood each component to an extensive level, allowing us to apply what we were currently reading about to our plans. As we read, we continuously improved our greenhouse and improved our product more than we ever thought possible.

Despite the overall positive impact that the book had on our project, some negatives altered how our group approached our project. A majority of the greenhouses in the book were much larger than the models we intend to build for the expo. With this, some of the solutions provided aren't feasible, requiring us to conduct additional research with each chapter to gain an alternative that could work just as effectively within our constraints. While this challenge was an annoyance during our research with the book, without it, our team would've not learned of some new exciting methods that could make our model even more efficient than planned, and it also gave our team additional practice with spontaneous modification to keep the efficiency of the product at a maximum.

The age of the book was also a concern when it came to the reliability of the information presented in the book. Despite the book being a recent publication, it was still nearly ten years old. While ten years is not that much time in a field such as renewable energy, there are always constant improvements and inventions that could prove more advantageous to our product than those given to us by the book. However, the book provides reliable insight into known processes that are effective and may be cheaper due to their age compared to newly discovered methods that may be pricer due to their complexity. The book also provided enough timeless content, such as the history of greenhouses, to stay relevant to the demands of my group. 

Overall, the book has been beneficial to our research for our product. The information it has provided us on specific processes, history, and mathematics when it comes to greenhouses is invaluable and will continue to serve my group throughout and even possibly beyond the expo project. Though the book's age is a concern, The information provided still was able to turn our group, which was filled with a majority of novices when it comes to solar energy, into people who are competent enough to be able to bring our product to life. The book will be a constant reference throughout the rest of our project and will aid us in our hopes of succeeding and creating a product that can help solve our problem and possibly even become a commercial success. 

02.03 Annotated Sketches 

02.04 Decision Matrices

02.05 Surveys/ Interviews

Drafted Interview questions:

1. We are currently trying to build a self-regulating garden, do you have any input on where exactly you would want us to put the garden in your neighborhood? 

2. Are there any specific concerns you have with the security of our garden and if so what would you advise us to do?

3. Do you normally have means for food and if not what is your alternative?

4. We are planning to include a self-irrigation system, do you have any preferences for how we place the system in the garden? 

5. Are there any important features we are missing?

6. How would you compare our product with our competitors?

7. What other types of people could find our product useful?

8. Is our product easy to use?

9. Would you recommend our product to other peers?   

10. What would you pay to use our product if it went into the garden market?

Interview 1: Bill Kay at Oakdale greenhouses  

1.  How long have you been in the greenhouse industry? 

Mr. Bill Kay has been in the greenhouse industry for about 17 years. 

2. What are things that are necessary for a greenhouse to be functional?  

There needs to be a watering system, a heating system, and a cooling system.   

3. Are there any other cooling systems that are helpful? 

There are possible options such as swamp coolers. Swamp coolers are much more efficient than exhaust systems because they help cool the temperature inside greenhouses and use less electricity, making this method of cooling cheaper. The only issue is that swamp coolers do need higher maintenance. 

4. What would be the best water system? Do you think sprinkler from top would be good? 

Drip lines would best because they are much more efficient than sprinklers. With sprinkler, the water is not fully going to the tree and could potentially to other places, additionally sprinklers could cause mold and rotting in the tables and other materials around. With drip lines, the water is fully focused on the plant 

5. Have you ever heard of hydroponic gardening? 

Mr. Bill Kay has these materials available and willing to donate them to us. Hopefully we are able to implement these materials into our greenhouse. 

Interview 2: Juliya Coffey at Crooked Creek Park

1. We are currently trying to build a self-regulating garden, do you have any input on where exactly you would want us to put the garden in your neighborhood? 

In my opinion, a neighborhood garden should ideally be somewhere in the center of the neighborhood for ease of access.

2. Are there any specific concerns you have with the security of our garden and if so what would you advise us to do?

My neighborhood is surrounded by multiple farms, one for cattle and another for pigs, so a concern I’d have would be keeping rogue animals out of the garden. If I could ask you to do anything, I’d like tall fences or chicken wire to keep the garden safe.

3.  Do you normally have means for food and if not what is your alternative?

Yes, I have means for food.

4.  We are planning to include a self-irrigation system, do you have any preferences for how we place the system in the garden? 

If I could ask anything of you, keeping the system away from the ground/ keeping the ground clear would be ideal. There are lots of older people in the neighborhood with mobility issues, so avoiding any potential hazards on the floor would be ideal.

5.  Are there any important features we are missing?

I do not personally notice any missing features.

6.  How would you compare our product with our competitors?

From the competitor products you’ve shown me, Your product seem to be all-encompassing compared to these competitors and their singular features or single-use design.

7.  What other types of people could find our product useful?

I think this product works well in a suburban setting like neighborhoods, but consider pitching this idea to a senior citizen home or other community welfare centers, I think they could get a lot out of your product.

8.  Is our product easy to use?

I believe the product is easy to use.

9. Would you recommend our product to other peers?   

Yes, anyone looking for a new garden should consider your product in my opinion.

10. What would you pay to use our product if it went into the garden market?

Anywhere between $150~$200.

02.06 Expo Presentation Board

02.08 Product Life Cycle/ Environmental Impact

02.09 Design Specifications

Goal and Milestones:

• Goal: Have a finalized design with the proper measurements, materials, and items that will be included in the first prototype and the final build.

• Goal: Have a digital model that will serve as not only as reference for construction, but also as a point of reference for discussing with investors and our mentors.

• Goal: Have a scaled down, physical model that can be used as a piece of demonstration during the actual expo and other pitches during the project.

• Goal: Have materials and resources for our final prototype allocated and ready for it's construction.

• Goal: Have 

• Goal: Have

• Milestone: Obtaining our mentors approval of our design, allowing us to be able to pitch our finalized design with investors and our peers confidently. 

• Milestone: Having the small scale prototype fully constructed and perfected for what we need to present byt the deadline

• Milestone: Having all the materials for construction finalized and collected so that production can be started swiftly

• Milestone: Having the 3D model of our finalized prototype made so that conveying ideas with our mentor and with the team during meetings can be more efficient.

Unobtainable:

• Having the prototype be fully functional with everything we plan to include in the final prototype. 

• Having the first prototype be to full scale with the same materials as the final prototype.

• Having all the planned amenities in the final prototype, such as the self recycling water or the water line adapter.

• Have our product be fully “green”, or having a complete net zero carbon footprint 

02.10 Technical Drawings/ Storyboards

02.11 Peer Review

02.12 Prototype Mock-Up

Isometric View of Prototype 1:

Side View of Prototype 1:

Front View of Prototype 1:

Reflection: 

Prototype one is a smaller-scale prototype covered in foam to represent the final constructed look of the garden. This prototype also reflects how the solar panels attached to the side of the greenhouse can collect energy while maintaining the air-tight seal necessary for the house to function as intended. The prototype also features a mock-up of the placement of the exhaust fan, which helps with cooling and airflow for the greenhouse. By building this prototype, our team not only learned how the product fits in a physical space but also how our design translates into reality when it comes to the specific placement of products, such as the exhaust fan, which was tentative until the prototype construction. Our next steps from this prototype would be to scale the prototype up and create a larger scale prototype that does not have the covering over it to reflect the internal systems and how these systems work in tandem with each other.

Side View of Prototype 2:

Isometric View of Prototype 2:

Reflection: 

Prototype two is a larger-scaled model that is not covered to show the inner workings of the prototype. The model features a water basin that holds water and acts as the source for the irrigation technology in the garden. This prototype also features the sprinkler system running through the center of the bed, hidden by the covering in prototype one. We achieved these small details thanks to the increased size of this prototype and the completion of the 3d model, which allowed us to have multiple views of angles that we couldn't necessarily reflect through sketches. By building this prototype, our team learned not only how these small mechanisms work but also the amount of space that will be necessary for the final product. The lesson we learned on managing the space of the prototype is a big concern as we planned for the product to be sizeable. Once we increased the scale of what we were working on, we encountered some challenges we hadn't previously considered, such as workspace and transportation, which we are now trying to solve in preparation for our final prototype.

02.13 Phase 1 Changes and Amendments

Problem Statement: 

• The first problem statement went through several changes, we went through about three problem statements. Our first problem statement discussed the concern for hurricanes in North Carolina and how our product would attempt to combat this problem by implementing batteries in our solar garden.  

Design: 

• Our design is still relatively the same. There have been a few changes to the systems in place. We still have a table but we also have the greenhouse plastic going all around and have come agreed to on a watering system. 

Research: 

• We have continued to do more research. We have been able to read our first book and have discussion. With the book we have been able to think about more things that we can implement in our product. 

Appendix/Website: 

• Nothing major in terms of changes, but updates have been made such as adding new vocabulary words to these items  in order to keep it updated with new terms from phase 2. The team website has also been updated to feature the new phase 2 assignments as well making that up to date.

02.14 Phase 2 Summary and Reflections

A three-paragraph (minimum) summary of the project’s strengths and weaknesses at this point in the design process.

At this point of the project, we've gotten far past the brainstorming stages, and we've reached the point where we as a group have settled on a design that we like and want to continue working towards. During phase 2 we received feedback from a lot of people such as our mentor and those who work with greenhouses, along with that we've read our research book. All of these items have helped develop our project to be stronger than it was before making us be at a point where we are confident with how strong our project has become. We improved the design by separating the water immigration system and garden bed, we settled on the number of solar panels we would use, we worked out how our water irrigation system would work, and we even developed ideas for timers on our product in order to make sure our garden's water comes out at specific times.

Our project still has a couple of weaknesses at this point that we are working towards fixing. One of the major things is despite having our finalized idea of what we want to build, having the 3D model, prototype, and sketches, we still need to get the materials needed to build the actual product. Most of the materials won't be much of an issue for us to get. Items such as soil, wood, PVC pipe, and nails for example are easy for us to get. The main issue would be getting the solar panels. Solar panels are the most costly of the materials that we need which is what we as a group need to figure out. An effective way to get the solar panels we need. That is the biggest weakness of our project at this point which we as a group are trying to figure out. We've done things such as the list for Mrs. Brown which details the specific materials we need, we've been in contact with people who have potential solar panels for us to use, and even thought of potential ways to raise money if we do need to buy the solar panels. 

Overall our project is at a point where we don't have much of anything to worry about, the main issue that we are working hard towards is making sure we can get access to the solar panels. Along with that, we also have our mentor to help us develop the actual product since we don't have much experience working with solar panels alone, but with the help of our mentor, we will be able to effectively make the product that we need to make. With the help of our mentors, we will for sure be able to make what we have to make which is why going into phase 3, we aren't too worried about the weaknesses we have so far as our strengths outweigh the weaknesses. We are very confident in our project and where we will be in phase 3 as we are working hard to gain the materials we need and are working closely with our mentor to make sure we can build our product as effectively as it can be built.