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

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 Sheet Metal 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 million sheep in Afghanistan Other insulation: –Bousillages – mixture of moss and clay Outer layer is a mixture of horsehair, water, and clay

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 Hot Material

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 1.2 Closed Loop Drain Down One Liquid Unreliable Freeze Protection Drain Back 2 Liquids Antifreeze Solution Good Freeze Protection Heat Exchanger Less Efficient 1.1 Open Loop Use Pump Direct Water Heating More Efficient Cost Less Drain-Back Freeze Protection UNRELIABLE

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 Members: Melissa Loureiro Emily Kunen Suza Gilbert Zach Auger Team Drain Back

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 2 nd 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 Total Cost: US$ –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 Efficiency:

What’s Next Performance Modeling –Several days of testing –Slight variations in model Prototype –Improve construction techniques –Compare to performance model

Team Thermosyphon Amalia Telbis Alex Surasky- Ysasi Steph Angione Adrienne Buell

–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 33 o –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

Thermosyphon: Working fluid: 40.5% ethanol-water mixture Boiling Temperatures: 84 o C Freezing Temperature: -24 o C 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 (20 o C) 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

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 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 Design Comparison

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

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 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

ACKNOWLEDGEMENTS Dr. Chris Bull Peter Argo – US Embassy in Tajikistan Professor Chason Professor Hurt Professor Tripathi Professor Breuer EWB!