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
• 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
• Glass:
– Used as glazing
– Reduces losses
– Has to be tempered and have high
transmittance
•
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 heatabsorbing solar thermal collectors
1.1 Open Loop
Direct
Water Heating
Use Pump
– 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:
Drain-Back
Freeze
Protection
Cost Less
More Efficient
UNRELIABLE
1.2 Closed Loop
Drain Down
One Liquid
Unreliable
Freeze Protection
Drain Back
2 Liquids
Heat Exchanger
Closed Loop
Antifreeze Solution
Less Efficient
Good Freeze Protection
•
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
– 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:
Efficiency
90.00%
89.80%
89.60%
89.40%
Efficiency
• Total Cost:
US$1167.02
89.20%
89.00%
Sheep wool
Bousillage
Clay
88.80%
Straw
88.60%
88.40%
Jan
Feb
March
Apr
May
June
Month
July
Aug
Sept
Oct
Nov
Dec
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 SuraskyYsasi
Steph Angione
Adrienne
Buell
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:
•
Efficiency (%)
92
1/5inch pipe
90
3/4inch pipe
88
86
84
82
80
78
0
10
20
30
40
50
60
70
Mixt Tem p (oC)
Temp of Plate vs Temp of Mixture
160
140
120
Temp Plate (oC)
•
– 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
Efficiency vs Mixt Tem perature
94
100
80
1/5inch pipe
60
3/4 inch pipe
40
20
0
0
10
20
30
40
Temp Mixt (oC)
50
60
70
Results:
Annual Output Temperatures of both the water and the antifreeze:
The water reaches
The antifreeze reaches
▪ app. 30°C in the winter
▪ app. 58°C in the summer
▪app. 65°C in the winter
▪above boiling point in summer
Antifreeze
End
Temperature
in Kabul
Performance
in Kabul
AnnualDaily
Performance
in Kabul
100 100
100
90
90
90
Temperature at Start of Hour (C)
70
70
70
60
60
50
50
60
50
40
40
40
3030
30
December Antifreeze
2020
December Water
20
June Antifreeze
1010
June Water
10
2
Ju
ly
Ju
ly
Ju
n
Ju e
ne
M
a
My
ay
Ap
April
ril
4
6
Au
gu
Au s t
gu
st
Se
pt
Se em
pt ber
em
be
r
O
ct
ob
O er
ct
ob
er
No
ve
m
No be
ve r
m
be
De
r
ce
m
De be
ce r
m
be
r
0
M
a
M rch
ar
ch
0
Fe
Febr u
br ar
ua y
ry
00
Ja
Janu
nua ry
ar
y
Output Temperature of Water (C)
Temperature (C)
80
80
80
8
Hour
Month
Month
10
12
14
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
DRAIN BACK
THERMOSYPHON
Freeze protection = draining system
Freeze protection =working fluid: ethanol-water
mixture
Powered by pump
Uses natural convection
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
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
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!