Performance modeling of low cost solar collectors in central asia
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Performance Modeling of Low Cost Solar Collectors in Central Asia. Project Presentation. Steph Angione, Zach Auger, Adrienne Buell, Suza Gilbert, Emily Kunen, Missy Loureiro, Alex Surasky-Ysasi, Amalia Telbis. Problem Definition.

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Performance Modeling of Low Cost Solar Collectors in Central Asia

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Performance Modeling of Low Cost Solar Collectors in Central Asia

Project Presentation

Steph Angione, Zach Auger, Adrienne Buell, Suza Gilbert, Emily Kunen, Missy Loureiro, Alex Surasky-Ysasi, Amalia Telbis


Problem Definition

  • Goal: Design a performance model for a solar collector in central Asia

  • Specifications:

    • Heat water for domestic use

    • Be low cost

    • Use local materials

    • Be efficient

    • Be easily maintained

    • Be sustainable


Step 1:Background Research

  • Background Research:

    • Region and climate data

    • Materials and availability

    • Heat transfer

    • Testing and modeling process


Geography, Climate and Housing: Tajikistan

  • Latitude of 34°00’N and longitude of 68°00’E

  • More than half of the country lies above 3,000 meters

  • Climate

    • Highlands similar to lower Himalayas

  • Housing

    • Built into the mountains

    • Multifamily/ multistory

  • Construction

    • Raw bricks, plaster & cut straw (horizontal layers)

    • Where available: wood used for roof beams

    • Cement often used for roof


Geography, Climate and Housing :Afghanistan

  • Latitude of 33°00’N and longitude of 65°00’E

  • Includes three distinct areas:

    • central highlands, southern plateau, and northern plains

  • Climate

    • hottest in southwest, coldest in northern regions with waves of intense cold and temperatures below zero

  • Housing

    • Construction Materials: stone, coniferous wood, plaster, straw, and brick

    • Terraced Housing


Materials

  • What to look for when choosing a material:

    • Thermal Properties

    • Durability

    • Availability

    • Construction Methods

    • Maintenance

    • Costs

  • Materials Specified by EWB:

    • Sheet Metal

    • Wood

    • Glass

    • Black Paint

    • Horsehair

  • Regional Materials:

    • Clay, Cement, Brick, Sheep Wool, Straw, Plaster


Sheet Metal

  • Variety of metals available

    • Best heat capacity – Aluminum [903 J/kg*K]

    • Best conductivity – Copper [401 W/m*K]

  • Durability and Construction Methods:

    • Cutting tasks only require aviation snips

    • Pieces are easy to bend

  • Copper Sheet:

  • Can be shaped into any form easily

  • Doesn’t not crack when hammered, stamped, forged or pressed

  • Resists corrosion and does not rust

  • Can be recycled

  • Easiest metal to solder

  • Aluminum Sheet:

  • Excellent conductor of heat

  • Light (about 1/3 weight of copper)

  • Withstands wind, rain, chemicals, pollution

  • Excellent durability

  • Can be recycled

  • Soldering requires specialized reaction fluxes and tools


Wood:

Used for construction

Easily cut

Hand-tools sufficient

Durable insulation

Readily available

Black Paint:

Used to absorb solar energy by changing the absoptivity

Absorptivity = a = 94%

Radiates back 90% of solar radiation

Glass:

Used as glazing

Reduces losses

Has to be tempered and have high transmittance

Horsehair and sheep wool:

Used for insulation: lasts for over 200 years

Material readily available

0.3 million horses in Afghanistan

11-14 million sheep in Afghanistan

Other insulation:

Bousillages – mixture of moss and clay

Outer layer is a mixture of horsehair, water, and clay


Hot Material

Heat Transfer Formulas

  • Conduction

    • Fourier’s Law: dQ/dt=-kA(dT/dx)

    • Through a material

  • Convection

    • Newton’s Law of Cooling: dQ/dt=hA(Ts-Tf)

    • Fluid flowing past a solid

  • Radiation

    • Stephan-Boltzman Law: dQ/dt=εσATb4

    • Heat emitted by an object


Components of a Solar Collector

  • Absorber Plate

  • Absorber Surface Coatings

  • Glazing

  • Insulation

  • Casing


Testing and Modeling

Determine All Variables and Constants

Visualized Design/Schematic

CAD software:

SolidWorks, ProE

Free-hand sketches


Calculations

  • Use of MatLab or Excel

  • Use of possible simulations

    • F-chart!

    • TRNSYS


Step 2: Identify the Situation

  • Specified Situation:

    • Domestic hot water heating for average household size of 7 people

    • Water use per person per day: 25 liters

    • Region: rural, mountainous

    • System output temperature: 60 °C

    • Year round functionality

    • Storage tank water capacity: 1-2 days

    • Delivery system: either batch or continuous flow


Step 3: Selected Designs To Model


Solar Heater Types and Designs

  • Passive vs. Active Solar Heaters

    • Active

      • use pumps to circulate water or an antifreeze solution through heat-absorbing solar thermal collectors

    • Passive

      • The water is circulated without the aid of pumps or controls

  • Open Loop vs. Closed Loop

    • If the liquid that needs to be heated is also the one being circulated:Open Loop

    • If antifreeze or another solution used in a heat exchanger to heat the water:Closed Loop


Possibilities and their +/-…what we ended up picking

  • Active

    • Open Loop:

      • (+) cost less

      • (-) pump controlled

      • (-) only possibility for freeze protection: manually draining X Second one OUT !!!

    • Closed Loop:

      • Drain Down:

        • (-): not reliable !!! X First one OUT !!!

      • Drain Back:

        • (+) good freeze protection

        • (+) can use water/water instead of antifreeze

        • (-) pump and 2 different storage tanks

  • Passive

    • Batch

      • (+)easy (can even be a tank painted in black)

      • (+) offers freeze protection because the water is only present in the tanks and the areas are large; the water cools off slowly

      • (-) takes long to heat the amount of water

    • Thermosyphon

      • (+) no need for pumps

      • (+) offers good freeze protection

      • (-) heavy tank placed above the collector

      • (-) efficiency decreases when using indirect heating

  • We voted between: Drain Back, Batch and Thermosyphon

    • Systems chosen

      • Group I (Suza, Missy, Emily and Zach): Drain Back System

      • Group II (Stephanie, Adrienne, Alex and Amalia): Thermosyphon


Team Drain Back

Team Members:

Melissa Loureiro

Emily Kunen

Suza Gilbert

Zach Auger


Drainback

  • Solar collector located above storage tank

  • 2 liquid system

    • Both can be water

    • 1liquid water and 1an antifreeze solution

  • Active closed loop system

    • Uses pump

  • Pump circulates water through collectors when collectors are warmer than stored water

  • Heat exchanger used in storage tank

  • Heat transfer between circulating fluid and potable water

  • Circulating solution drains to a 2nd tank when pump shuts off

  • Tank is placed on a tilt for complete drainage


  • Team Drain Back System

    • Collector

      • 28 parallel copper pipes

      • Copper plate

      • 1.13m^2 area

      • Soda lime glass glazing

      • Sheep wool insulation

      • Black interior

    • Housing

    • Heat Exchanger

      • Heat transfer fluid flows through exchanger

      • Exchanger within storage tank containing working fluid

    • Pump

    • Drain back Reservoir


    Model

    • Software: Microsoft Excel

    • Spreadsheets for:

      • -Materials

      • -Energy Input and Output

      • -Collector

      • -Heat Exchanger

      • -Sunlight

      • -Efficiency


    Efficiency and Costs

    • Efficiency:

    • Total Cost: US$1167.02

      • Soft Copper Tubing for Heat Exchanger: $83.26/100 feet

      • Copper Sheet: $147.30/ 2 sheets

      • Copper Feeder Pipes: $26.00/12 feet

      • Glazing: $320.00/ 2 sheets

      • Black Paint: $30/gallon


    What’s Next

    • Performance Modeling

      • Several days of testing

      • Slight variations in model

    • Prototype

      • Improve construction techniques

      • Compare to performance model


    Team Thermosyphon

    Adrienne Buell

    Steph Angione

    Alex Surasky-Ysasi

    Amalia Telbis


    Thermosyphon

    • Area 1.85 m^2: standardized according to available glazing

    • Absorber Plate: 0.02” thick copper sheet bent around the parallel pipes

    • Glazing: 1/8” thick single glass sheet with 0.01% iron-content

    • Parallel Flow Pattern: Copper piping

      • Header and footer 1.5”

      • Parallel pipes 0.5”

      • Free floating array supported by wood risers every 10”

    • Housing: Wood frame that slides into the mounting stand at 33o

    • Insulation:

      • dead air between plate and layer of

        plywood

      • boussilage clay, water, and horsehair

      • 1m high stand with brick walls encasing

        dead air

    • Back flow prevention: one way valve

    • Pressure relief valve needed at high

      antifreeze temperatures


    Thermosyphon:

    • Working fluid: 40.5% ethanol-water mixture

      • Boiling Temperatures: 84oC

      • Freezing Temperature: -24oC

  • Heat exchanger:

    • Countercurrent

    • Bendable copper tubing: 1”outer diameter

      • Length: 9m

      • 11 loops- 0.25m diameter spaced at 1.05”

  • Storage tank: placed above the solar collector

    • Dimensions: 0.5m x 0.5m x 1.05 m steel casing

    • Insulation: sheep wool, boussilage and brick


  • Modeling:

    • Software used: Excel

    • Governing Equations:

      • Heat transfer in the solar collector

      • Mass flow rate calculation

      • Heat transfer in the heat exchanger

    • Collector plate efficiencies at a constant ambient temperature (20oC) for parallel pipes of different sizes vs. the temperature of the antifreeze

    • Collector plate temperatures at a constant ambient temperature (20°C) for parallel pipes of different sizes vs. the temperature of the antifreeze


    Results:

    • Annual Output Temperatures of both the water and the antifreeze:

    • The water reaches The antifreeze reaches

    • ▪ app. 30°C in the winter ▪app. 65°C in the winter

      • ▪ app. 58°C in the summer ▪above boiling point in summer


    What’s next?

    • Use computer programming software

      • F-chart method to analyze efficiencies

      • Matlab to ease the process of iteration

    • Optimize design

    • Model different regions

    • Change the working fluid during the summer or use a different antifreeze solution

    • Make a business plan and try to implement


    Design Comparison

    THERMOSYPHON

    Freeze protection =working fluid: ethanol-water mixture

    Uses natural convection

    Price ~ $1250 US

    Collector Area = 1.85 meters^2

    Parallel pipes in collector = 21

    Parallel pipe outer diameter = .5 in

    Single Glazing

    Length of Heat Exchanger = 9 meters

    DRAIN BACK

    Freeze protection = draining system

    Powered by pump

    Price ~ $1167 US

    Collector Area = 1.13 meters^2

    Parallel pipes in collector = 28

    Parallel pipe outer diameter = .625 in

    Single Glazing

    Length of Heat Exchanger = 3.01 meters


    Implementation: The need for sustainable development


    What is Sustainable Development?

    • Meeting present needs with out compromising those of the future

    • Goals

      • Improve quality of life

      • Promote further economic growth

      • Improve social conditions and equality

      • Protect and improve environmental and human health


    How can our project be made sustainable?

    • Use local resources, knowledge, and skills

    • Include local involvement in

      • Planning

      • Design

      • Implementation

    • Have education and training to foster an understanding of and appreciation for the technology

    • Develop renewable energy markets to encourage further research and economic growth, making the technology competitive and desirable


    What Comes Next


    If only we had more time…

    Designing

    -Solar collector designs limited to those in existence that have been tested

    -Overlooked Possibilities

    -Collector plate designs

    -Materials


    Modeling

    -Optimizing values of the collector using computer

    programs

    -Designing a program where a user enters desired parameters and the output is their personalized collector

    Prototyping and Testing

    -Theoretical model vs. Prototype

    -Need to construct and TEST a real model

    -Compare theoretical and experimental values

    -Construction techniques can be simplified


    ACKNOWLEDGEMENTS

    • Dr. Chris Bull

    • Peter Argo – US Embassy in Tajikistan

    • Professor Chason

    • Professor Hurt

    • Professor Tripathi

    • Professor Breuer

    • EWB!

    Thanks!


    Questions?


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