Solar Adsorption Heating Ventilation and Air Conditioning System

ET-493 Senior Design Project I Spring 2013

Final Report

By: Justin Cifreo, Benjamin GabrielMechanical Engineering TechnologySoutheastern Louisiana University

Advising Instructors: Dr. Junkun Ma

Dr. Cris Koutsougeras

Submitted May 10, 2013

Introduction

In this senior design project, our group is researching and designing a solar powered

heating ventilation and cooling (HVAC) system.

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Abstract

The objective of this senior design project is to build a self-sustainable, solar-powered heating, ventilation and air conditioning system that would provide the desired heating and cooling for the sustainability center. The system would also be used for demonstrative and instructional purposes for students as well as university visitors. In addition, the system will provide an economical solution to the financial burden imposed by recent budget cuts to educational institutions such as Southeastern Louisiana University. The project serves to further knowledge of alternative energy sources while at the same time bringing positive publicity for Southeastern’s blossoming engineering program.

OverviewSolar energy is free and sustainable. Therefore, capturing solar energy for use in heating

and cooling applications is an economically sound objective. Mr. Byron Patterson, Southeastern’s Physical Plant Director, and Dr. Junkun Ma, Assistant Professor of Engineering, have worked on green technologies together at Southeastern for quite some time. Mr. Byron and his team have saved the university one million dollars in energy costs just last year, 2012. This remarkable achievement is a testament of the cost saving potential that can be accomplished here at Southeastern with green technologies.

Purpose The objective of this project is to research and design a solar heating, ventilation, and

cooling system that will reduce Southeastern Louisiana University’s reliance on gas and electric energy. This report consists of the background, justification, research, methodology and design of a solar adsorption HVAC system. In addition, this report discusses the objectives of the design, the challenges faced by the designers, and the solutions to those challenges.

Background At the beginning of the semester we met with Dr. Ma to discuss potential senior projects

that we could complete. Dr. Ma informed us that he and Mr. Patterson had in mind to phase out the horticulture building to utilize it as the future site of the sustainability learning center. At this new facility students and supporters will have the opportunity to learn about solar energy firsthand.

Southeastern has recently installed solar absorption panels on two campus facilities; the kinesiology and biology buildings. The buildings both have solar panel arrays that are only used for heating purposes. Mr. Patterson stated that the solar panel systems are so efficient, that at times they produce a surplus of energy. A surplus may sound beneficial, but in terms of usability a surplus in heat energy equates to the production of steam within the system. The university mitigates this surplus by disabling a number of arrays depending on severity.

Due to the success of previous solar heating systems at Southeastern and untapped potential of solar energy, the university has solicited our help via the engineering technology department. Our task in this endeavor is in the designing and constructing of a solar-powered, heating, ventilation, and air conditioning system that can be integrated into the horticulture facility. On the following page is a schematic view of our proposed Solar HVAC system for the Sustainability Center.

The schematic on the next page presents the overall nature the system we have designed in response to the university’s specifications. The placement of system components is not representative of the actual system. Rather, that final layout will be determined from further design and research over the course of the project. The diagram does offer the reader an idea of how our design will be integrated into the existing facility. We believe that this system will serve the needs of our customer. We also hope that our design may aid future solar technology projects at Southeastern.

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JustificationRecently, Southeastern has installed solar panels on the top of two of its major buildings.

The kinesiology and biology buildings both have multiple solar panel arrays which are used for heating purposes only. These solar panels provide sufficient energy to heat the buildings in the winter and maintain the desired water temperatures in the Olympic-size swimming pool. There is actually quite a bit of excess heat generated by the arrays on top of the kinesiology building. It is easy to see the feasibility and soundness of this project given the success of these solar heating systems which have already been installed. Solar absorption panels last longer than Photovoltaic panels. This allows the university to get back what they invest in them.

At this point the reader may be unclear about what type of solar panel the author is referring to. To clarify, the author is speaking of a solar panel that absorbs heat from solar radiation called a serpentine absorption panel. The principle behind the solar absorption panel is similar to a heat radiator, but in reverse. Instead of transferring heat to the surroundings, solar absorption panels absorb solar energy and transfer the heat to the system by way of convection fluid flow through the panel’s capillary plate.

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ProgressDue to on foreseen challenges in selecting a system design, we are only able to offer an

overview of the selected materials, equipment, and reasoning for their selection. Our theoretical customer, Southeastern Louisiana University, demanded that we research multiple solar HVAC systems for their final selection. Our team, which at the time consisted of Justin Cifreo and Benjamin Gabriel, set out on the task of researching and reporting system designs and their advantageous attributes as well as costs. For weeks our team met with Mr. Byron Patterson and our advisor Dr. Junkun Ma. Much information was gathered and the customer desires were recorded and taken into consideration for a final system selection. At the suggestion of our advisor, we created a rough schematic of a system which we considered to be appropriate for the application. At the next meeting the customer -being one of great knowledge in the field of heating and ventilation- proceeded to explain us the basics of heating and ventilation systems as well as the current course of affairs at Southeastern. The customer’s lesson was very informative, but lacked the necessary components we as a design team were looking for and so desired.

Here is where our design process ran into some setbacks. It was unknown to our team that the customer had chosen a system/ various system components in various degrees of finality even as we the theoretical employees researched for and queried them various systems for weeks. On multiple occasions we asked the customer if they had selected a system and if so what components were specified and of what quantity. We did this not out of laziness, but rather because we did not understand the path for which our advisor wished us to take. In defense of our advisor, this semester has been very laborious for him and we dare not put our setbacks on him.

Upon realizing our misunderstanding of our task and seeing our blatant determination Dr. Ma pointed our team -which at this point consisted of the previous members with the addition of Nathan Taylor- in the direction of total heat load and flow rate calculations. This was suggested, as we learned, to specify a tonnage value for the design space. Not fully understanding the concept of flow rates and heat load design, we endeavored to find answers in the form of anything resembling a heating and ventilation calculation manual. Countless nights were spent scouring the web and asking for such documents. Vague representations of the equations and concepts needed to calculate heat load and flow rates were found but not fully understood.

At last, our team found the necessary materials for specifying an accurate system tonnage from heat gain, heat loss, and various other factors. This discovery, however, seems to have come a cost; time. Doing what we could with the limited knowledge and resources available this semester we managed to get a lot done. Nonetheless, we have as of yet not been able to specify a full system design for the Sustainability Center.

Our current progress to this date is as follows:1. Researched existing solar heating and cooling systems on the market2. Came up with a theoretical solar HVAC system schematic 3. Specified excavating a retention pond for efficient condenser heat sink application4. Measured interior volumes for heat load calculation5. Measured areas of exterior walls for heat values 6. Measured windows and doors for heat values7. Logged present and future equipment for heat gains

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8. Obtained heat load and flow rate equations9. Made excel spreadsheet for heat load calculation and flow rate analysis10. Researched heat exchangers and designed simple heat exchanger in COMSOL11. Researched duct flow rate calculation, material selection, and geometry specifications12. Designed and analyzed simple solar heating panel in COMSOL13. Took pictures of current system components for control design and layout14. Designed system control layout and flow charts for system

Research

Solar Absorption Panel: The absorption panel, also referred to as a solar thermal absorption panel, is composed of

four basic parts: the metal frame, the coated glass face, a capillary tube plate, and insulation. The frame is usually made of aluminum alloy for weight savings and corrosion resistance. The glass is composed of a highly efficient, proprietarily coated, polycarbonate. The design permits solar radiation to enter, but prevents it from leaving. This one way design of the glass maximizes efficiency. The solar absorption panel we chose has a rated efficiency of 79.2 % as stated on Schueco’s website. The capillary plate is composed of a specially coated, copper plate whereby capillary tubes run vertically to enable fluid flow via convection. The insulation in the panel serves the purpose of keeping heat loss to the surroundings to a minimum, while also maximizing efficient heat transfer to fluids within the system. Below is a simulated cutaway and actual view of the Schueco solar absorption panel.

The fluid running through the absorption panel is composed of a mixture of propylene glycol and water. Mixture ratios vary according to the application and the climate demands of a particular region. The fluid mixture reduces internal corrosion and permits the system to use fluid temperatures below thirty-two degrees Fahrenheit. The diagram below exemplifies the fluid flow principle discussed earlier. The capillary tubes within the thermal panel are connected in parallel from the input pipe to an output pipe.

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This configuration is important because not all parts of the panel heat up at the same rate. Therefore, each capillary tube does not experience the same flow rate. The design allows each tube to experience differential flow while also permitting maximum flow through the inlet and outlet pipes. The panels are connected together in series with hot connecting to hot and cold to cold. There are copper insulated pipes that run from the outputs of the panel array to a heat exchanger and back to the panel array input. According to Mr. Patterson the mean output temperature of the water-glycol mixture in these pipes is around 178 degrees Fahrenheit.

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Heat Exchanger:After the fluid is heated up by solar energy, it flows into a heat exchanger. As the name

implies, this unit transfers heat from the fluid to the unit and then from the unit to the conditioned water that leads to the adsorption chiller or evaporator / air handler. The heat exchanger is also manufactured by Schueco USA.

Latent Heat Storage Tank: This is a 1000 US Gal. tank that

stores the heated water from the absorption panels. The tank serves as a heat bank from which heating or cooling -via the adsorption chiller- may occur on overcast days or at night when solar energy is not available. The tank is manufactured by Lochinvar.

Chiller Units:We researched and analyzed two

plausible chiller systems for our application. First, we learned about absorption chillers and noted their advantages and disadvantages in terms of efficiency. Second, we learned and noted the advantages and disadvantages of adsorption chillers. Absorption is passage of one substance into another. An absorption process creates a solution that is difficult to distinguish the two

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substances that are combined. In addition, the solution created by an absorption process is harder to separate into initial components; therefore requiring a greater thermal energy input.

Adsorption is the adhesion of molecules of one substance to the surface of another. One advantage of an adsorption unit is its ability to utilize a lower and broader temperature range of hot water than the absorption chiller. This is made possible because in the process of adsorption molecules only loosely adhere to the surfaces of the substances. As a result, separate of the substances requires less thermal energy input.

Adsorption chillers are also more durable than absorption chillers and have an average lifespan of about 30 years. Typical maintenance is necessary only once every 3 years. This attribute of adsorption chiller units makes them an economical choice for a customer.

Adsorption chillers use water as a refrigerant and a proprietary, permanent silica gel as an adsorbent. The evaporator section cools the chilled water by evaporating the refrigerant water by the adsorption of silica gel. This occurs in two adsorbent chambers within the adsorption chiller. The hot water then regenerates the silica gel in the second of the two adsorbent chambers. This process alternates between the two adsorbent chambers. Water vapor that is released from the gel condenses in the condenser. The condenser is cooled by an external device such as a cooling tower or an auxiliary geothermal heat sink.

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Heat Sink Pond: In addition to the adsorption chiller, a cooling tower or geothermal heat sink needs to be

designed or obtained in order to utilize the adsorption chiller’s condenser cooling process. This increases the efficiency of the chiller by transferring the heat from condensing unit to the exterior environment. The location of the geothermal heat sink will be near the bottom of a 6 to 9 foot deep pond pictured below.

Green House Heaters:The two greenhouses located behind the sustainability center only require heating for the

winter season. In the summer their temperature is regulated with ventilation fans that are outside the realm of our project. The design of the winter heating units is currently being researched, but the mode of heating is known. The greenhouses will be heated by natural convection heating units called radiators. The source of heat for the heaters will come directly from the latent heat storage tank.

Building Material:The horticulture building consists of two main building

materials; concrete masonry units (CMUs) and insulated metal panels (IMPs). These particular concrete masonry units are a standard nominal size of 16x8x8 inches and contain two hollow cavities. The insulated metal panels are 2 ½ inches thick and feature 26 gauge metal on both the exterior and interior. Polyisocyanurate rigid foam is sandwiched between the two metal sheets to serve as insulation.

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Ducting and Ventilation:Ducting and ventilation are currently being researched. To design the ducting and

ventilation for this project other aspects such as total heat load and flow rate numbers need to be computed. Sensors for indoor and outdoor temperatures and relative humidities are currently being setup for such calculations. Below is a diagram of ducting geometries that we are learning how to incorporate in our design.

1. http://www.perfect-home-hvac-design.com/ images/Basic-Duct-Layout.jpg

Two Speed Blower Unit:

2. http://www.aquaair.net/FlexAir_FX15-30_Blower_motor_assm.JPG

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Goals and Objectives1. Researched existing solar heating and cooling system s on the market 2. Came up with a theoretical solar HVAC system schematic 3. Measure interior volumes of all facility spaces for heat load calculation 4. Measure area of exterior walls for heat values 5. Measure windows and doors for heat values 6. Log present and future equipment for heat gains 7. Obtain heat load and flow rate equations 8. Make excel spreadsheet for heat load calculation and flow rate analysis 9. Research heat exchangers and design simple heat exchanger in COMSOL 10. Research duct flow rate calculation, material selection, and geometry specifications 11. Design and analyze simple solar heating panel in COMSOL 12. Design system control layout and flow charts for system 13. Calculate U values for heat losses and gains through exterior walls #14. Calculate U values for students #15. Calculate U values for equipment and miscellaneous #16. Calculate total heat load for cooling17. Calculate total cooling load for winter18. Calculate positive and negative CFM rates for all rooms19. Calculate and design ducting system 20. Calculate convection flow rate in green houses 21. Specify control components and locations according to specifications22. Calculate total efficiency of system23. Complete system specification

Methodology The project involves the following:24. Material Specification25. Material Selection26. Schematic Diagram Construction27. Heat System Design28. Chiller System specification29. Sensor Selection30. Control Analysis31. Thermodynamic Principles32. Fluid Mechanics Principles33. Thermal Expansion Analysis34. Flow Rate Analysis35. Heat Loss and Heat Gain36. Thermal Efficiency Analysis37. Energy Consumption Analysis38. Sun Path Positioning39. Seasonal Weather Analysis

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40. Fabrication and Assembly41. Setup42. Testing and Troubleshooting

Timeline

Date Task

1/22 Preliminary project meeting with Dr. Junkun Ma

1/25 System introductory meeting with Mr. Byron Patterson and Dr. Junkun Ma, obtained floor plan and area measurements

1/28 Solar HVAC systems researched

1/30 Researched different solar energy collector units, selected rough schematic system diagram

2/1 Collected height measurements at project site, calculated volumes for heat calculations

2/6 Visio schematic constructed to present to Mr. Byron

2/7 Meeting with Dr. Ma, discussed system components and operations of components

2/27 Brainstorming meeting Mr. Byron, Dr. Ma, Dr. Rode

3/6 Biology building system walkthrough

3/8 Calculate total heat of each volume section, learn heat flow analysis, take pictures Biology Building

3/13 Meet with Byron to solidify specifications

3/14 Calculate and Analyze individual system components

3/20 Meet with Byron and Dr. Ma to get input and take next step in design

3/27 Discussed back tracking, heat load and general duct work design,Researched duct work and sizing along with heat load factors

4/11 Created excel spreadsheet

4/20 Collected wall, window, and equipment loads

5/3 Calculate Total Heat Load

5/10 Set up Sensors ( Humidistat, Thermometer)

Summer/ Fall

Obtain and Learn Manual J for heat load

Summer/ Fall

Obtain and Learn Manual S for equipment selection

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Summer/ Fall

Obtain and Learn Manual D for duct design

Summer/ Fall

Obtain and Learn Manual T for duct design

Summer/ Fall

Analyze system design compared to available system components

Summer/ Fall

Control

References

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http://www.perfect-home-hvac-design.com/images/Basic-Duct-Layout.jpg

http://www.aquaair.net/FlexAir_FX15-30_Blower_motor_assm.JPG

http://www.schueco.com/web/us/residential_commercial/solarheat_solarpower/products/solar_thermal_systems/Solar_Collectors/Schueco_performance_series

Engineeringtoolbox.com

Modern Refrigeration and Air Conditioning 18th edition

Shuco USA

Lochinvar Corporation

Adsorptionchiller.com

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