Test of technologies for affordable solar greenhouses (Тестирование технологий для дешевых солнечных теплиц) PDF
Preview Test of technologies for affordable solar greenhouses (Тестирование технологий для дешевых солнечных теплиц)
TEST OF TECHNOLOGIES FOR AFFORDABLE SOLAR GREENHOUSES A Thesis by YONATAN DOV STRAUCH Submitted to the Graduate School Appalachian State University In partial fulfillment of the requirements for the degree of MASTER OF ARTS August 2008 Major Department: Technology ! ! ! ! TEST OF TECHNOLOGIES FOR AFFORDABLE SOLAR GREENHOUSES A Thesis by YONATAN DOV STRAUCH August 2008 APPROVED BY: Marie Hoepfl Chairperson, Thesis Committee Brian Raichle Member, Thesis Committee Jeff Ramsdell Member, Thesis Committee Dennis Scanlin Member, Thesis Committee Jeffrey Tiller Interim Chairperson, Department of Technology Edelma Huntley Dean, Research and Graduate Studies ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Copyright by Yonatan Dov Strauch 2008 All Rights Reserved ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ABSTRACT TEST OF TECHNOLOGIES FOR AFFORDABLE SOLAR GREENHOUSES. (August 2008) Yonatan Dov Strauch, B.A. Mount Allison University M.A. Appalachian State University Thesis Chairperson: Marie Hoepfl The problems with solar greenhouses-high installation costs and performance shortcoming such as low light levels due to thermal mass and solid walls-can be addressed by the use of innovative technologies within the same solar design parameters. Liquid foam insulation used between two layers of polyethylene film has been studied before as a retrofit insulation which can be inserted and removed when appropriate and provide insulation without solid, building-style construction. It has previously not been tested within a highly insulated passive solar design. Heat storage using tubes buried in the subsoil can be used instead of thermal mass to allow space and light in the greenhouse to be used for plants. These two technologies were combined in small, unheated greenhouses. The effect of these technologies was measured during a moderately cold winter climate. Results showed that both technologies can be good substitutes for solid insulation and thermal mass thermally, but that subsoil heat storage can increase water vapor in the greenhouse at night. ! ! ! ! ! ! ! iv! ! ! ! Acknowledgements I would like to thank those without whom this work could not have been completed. I would like to thank my family and my spouse to be Jannah Tudiver, who supported me through two and a half years of tireless work, and who helped with construction at the test site many times. My parents deserve all the credit for more than I can mention here. Specifically, my parents enabled me to focus on my academic work by helping me cover the costs of tuition. My father also traveled a long way to help with the site construction. I would not have been able to begin this research project without the help of dozens of my peers who volunteered during the site construction and subsequent renovations. They embodied the best of the Appropriate Technology program at Appalachian State University. A few students stand out in particular for their deep dedication to seeing through the wider project of which this thesis work was a major part. They are David Fulton, Brian Taddonio, Roscoe Oswald, Matt Fedorko, and Joe Rinehart. I also owe a debt of gratitude to my thesis committee for going beyond the call of duty in supporting me in this work, which falls outside any of their personal research interests. Another essential prerequisite for this research was the funding agencies. I am thankful to the United States Environmental Protection Agency P3 Student Sustainable Design Competition for two rounds of generous funding, as well as, to the Sustainable Agriculture Research and Education (SARE) program of the USDA for awarding me its Graduate Student Grant. Last, but in no way least, I am thankful to Charles Church, owner of Watauga River Farms, for providing the space for the experiment, and for the extensive backhoe work he did pro-bono during construction. ! v! ! ! ! Contents List of Tables...……………………………………………………………………………………X List of Figures...…………………………………………………………………………………...X CHAPTER 1: Introduction & Overview!.........................................................................................!1! Introduction!..................................................................................................................................!1! Greenhouses and Energy!..............................................................................................................!3! Thermodynamic Considerations!..............................................................................................!3! Economic Considerations!........................................................................................................!4! Ecological Considerations!.......................................................................................................!5! Toward More Energy Efficient Greenhouses: A Very Brief History!..........................................!6! Emerging Technologies for Energy Efficient Greenhouses!.........................................................!8! Statement of the Problem & the Purpose of the Study!................................................................!9! Liquid Foam Insulation!..............................................................................................................!11! Sub-soil Heat Storage!................................................................................................................!13! Description of the Study!............................................................................................................!15! Significance of the Study!...........................................................................................................!16! Chapter 2: Literature Review!.........................................................................................................!17! Economics of Greenhouses!........................................................................................................!17! The Greenhouse Industry!.......................................................................................................!18! Solar Greenhouse Economics and History!............................................................................!19! The Science of Greenhouse Energy!...........................................................................................!22! Modeling Greenhouse Energy!...............................................................................................!23! Practical Greenhouse Energy Science!...................................................................................!26! Energy Saving Practices in the Greenhouse Industry!................................................................!27! Traditional Strategies for Saving Energy in the Greenhouse Industry!..................................!27! Advanced Strategies for Saving Energy in the Greenhouse Industry!....................................!32! Best Practices Applicable to Small Scale Solar Greenhouses!...............................................!35! Fitting Passive Solar Design to Greenhouses!............................................................................!36! Passive Solar Methods as a Design Guide!............................................................................!37! Reconciling Thermal and Agronomic Performance!..............................................................!39! Solar Energy Input!.................................................................................................................!45! vi! ! ! ! Incident Angle!........................................................................................................................!47! Subsoil Heat Storage!..................................................................................................................!49! Kinds of Heat Storage Systems!..............................................................................................!49! Subsoil Heat Storage Systems!................................................................................................!50! Key Dynamics and Parameters Affecting System Performance and Optimization!................!53! Performance Metrics, System Optimization, and Subsoil Heat Storage Summary!................!65! Liquid Foam Insulation!..............................................................................................................!68! The History of Liquid Foam as Insulation!.............................................................................!70! Understanding Aqueous Foam!..............................................................................................!71! Functionality of Foam Insulated Greenhouses!......................................................................!78! Economics of Foam Insulated Greenhouses!..........................................................................!79! Summary!................................................................................................................................!80! CHAPTER 3: Methods!..................................................................................................................!81! Hypotheses and Research Questions..........................................................................................!81! Experimental Design and Construction!.....................................................................................!83! Location and Site!...................................................................................................................!83! Greenhouse Structures!...........................................................................................................!83! Subsoil Heat Storage System!.................................................................................................!85! Liquid Foam Insulation System!.............................................................................................!86! Data Acquisition System!............................................................................................................!87! Structural Features, Winter 2007!...............................................................................................!89! Structural Modifications, Winter 2008!..................................................................................!90! Experimental Methods!...............................................................................................................!91! Period 1: January 25 - February 1, 2007!..............................................................................!93! Period 2: March 3 - 13, 2007!................................................................................................!93! Period 3: December 29, 2007 – January 8, 2008!..................................................................!93! Period 4: February 13 – March 4, 2008!................................................................................!94! Period 5: March 15 - 26, 2008!.............................................................................................!95! Analytical Methods!....................................................................................................................!95! Correction Factor for 2008!...................................................................................................!95! Analysis of the Effects of SHCS!.............................................................................................!96! Analysis of the Effects of Liquid Foam Insulation!.................................................................!98! vii! ! ! ! Analysis of the Effects of the Combination of LFI and SHCS!................................................!99! CHAPTER 4: Results!..................................................................................................................!100! Results for Greenhouse with SHCS subsoil heat storage system!............................................!100! Correction Factor for trials during 2008!............................................................................!101! Effect of SHCS on Nightly Low Air Temperatures in an Unheated Greenhouse!.................!101! Effect of SHCS on Daytime High Temperatures in a Sealed, Unheated Greenhouse!.........!108! Comparing Soil Temperature Evolutions for SHCS at 225 cmh and 675cmh!....................!109! Comparison of Heat Transfers for Thermal Mass and SHCS at 225 cmh During Periods 3 and 675 cmh During Period 5!.............................................................................................!113! Soil Temperature Gradients!.................................................................................................!120! Factors Affecting Plants!......................................................................................................!121! Summary of Results for SHCS!..............................................................................................!123! Results From Greenhouse with Liquid Foam Insulation!.........................................................!125! Effect of LFI on Nightly Low Air Temperatures for an Unheated Greenhouse!...................!125! The Effect of LFI During the Day on Light and Temperatures!............................................!127! Effect of LFI on Thermal Mass Heat Storage!......................................................................!130! Factors Affecting Plants!......................................................................................................!131! Dynamic Insulation Efficiency and System Energy Consumption!.......................................!132! Summary of Results for Liquid Foam Insulation!.................................................................!138! Results for Greenhouse with the Combination of Liquid Foam Insulation and SHCS Subsoil Heat Storage!.............................................................................................................................!138! Effect of LFI/SHCS on nightly low air temperatures!...........................................................!138! Effect of LFI on Soil Temperatures in the SHCS Subsoil Heat Storage System Over Time!145! Effect of LFI/SHCS and SHCS in greenhouses on Thermal Mass!.......................................!148! Heat Exchange for SHCS with and without LFI!..................................................................!149! Summary of Results for the Combination of LFI and SHCS!................................................!149! Chapter 5: Summary, Conclusions, and Discussion!...................................................................!150! Introduction!..............................................................................................................................!150! Conclusions for Subterranean Heating and Cooling System (SHCS)!.....................................!151! SHCS and Nightly Lows!.......................................................................................................!151! SHCS Energy Exchange and Comparison to Thermal Mass!...............................................!152! SHCS and Soil Temperatures!...............................................................................................!155! viii! ! ! ! Findings for SHCS that are Inconclusive!............................................................................!155! Summary Conclusions for SHCS!.........................................................................................!156! SHCS Discussion!.....................................................................................................................!156! Best Practices and Optimization!..........................................................................................!156! Remaining Questions!...........................................................................................................!158! Conclusions for Liquid Foam Insulation (LFI)!........................................................................!160! LFI and Nightly Lows!..........................................................................................................!160! LFI in a North Wall and Daytime Highs!..............................................................................!161! LFI and Thermal Mass!.........................................................................................................!161! LFI Discussion!.........................................................................................................................!162! Discussion of Inconclusive Evidence and Further Research!...............................................!162! Best Practices and Optimization!..........................................................................................!163! Issues for Implementation of LFI!.........................................................................................!164! Conclusions for the Combination of LFI and SHCS!...............................................................!165! LFI/SHCS and Nightly Lows!................................................................................................!165! LFI, SHCS and Soil Temperature Evolutions!......................................................................!166! Discussion for the Combination of LFI and SHCS!..................................................................!167! Final Thoughts!.........................................................................................................................!168! Works Cited!.................................................................................................................................!171! Appendix A: A Summary of Site Visits and Interviews!.............................................................!176! Appendix B: Equipment and Costs for a Stand-Alone Greenhouse!...........................................!182! Curriculum Vita!...........................................................................................................................!183! ! ! ! ! ! ! ! ! ix! ! ! ! ! List!of!Tables! Table 1: Soil Temperature Evolutions Effecting SHCS Air-to-Soil Temperature Differences....106 Table 2: Difference in Daytime High Temperatures between Experimental Greenhouses one and two on Sunny Days……………………………………………………………………………...109!! ! List!of!Figures! Figure 1. Stand-alone (left) (Clovis Lande, 2008) and range (right) (Trade Note Net , 2008) greenhouses…………………………………………………………………………………..….....2 Figure 2. The “Ark” bioshelter on Prince Edward Island (Barnhart, 2007)……………….………7 Figure 3. Schematic diagram of foam system components in the greenhouse……………………12 Figure 4. Schematic diagram of Subsoil heat storage system installed…………………………...12 Figure 5. A typical passive solar greenhouse design (National Center for Appropriate Technology, 2008)………………………………………………………………………………..39 Figure 6: Cross section of greenhouse…………………………………………………………...85 Figure 7. Floor Plan with layout and sensor locations…………………………………………...89 Figure 8. Experimental trials……………………………………………………………………..92 Figure 9: Reference greenhouse (front right), greenhouse with LFI and SHCS (front left), and greenhouse with SHCS (back)……………………………………………………………………92 Figure 10. Correction factor does not apply when LFI is used…………………………………102 Figure 11. Raw data does not account for the effect of the wider glazing cavity in the experimental greenhouse (Period 3)…………………………………………………………….104 Figure 12. The effect of the SHCS at 225 cmh in January was slight regardless of the ambient low……………………………………………………………………………………………….104 Figure 13. Note that the coldest nights in Period 3, as shown in Figure 11 as January 1-3, the temperature difference between greenhouses increased each consecutive night………………..105 Figure 14. Raw data does not account for the effect of the wider glazing cavity in the experimental greenhouse (Period 5)…………………………………………………………….107 x! !
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