ELTR 1223
Survey of Renewable
Energy Technology
Overview of Solar Thermal
Applications
Unit 5
Source:
Use Policy

This material was developed by Timothy J.
Wilhelm, P.E., Kankakee Community College,
with funding from the National Science
Foundation as part of ATE Grant No. 0802786.

All materials in this presentation are designed
and intended for educational use, only. They
may not be used for any publication or
commercial purposes.
Source:
Author, Editors/Reviewers
Author: Timothy J. Wilhelm, P.E., Kankakee
Community College
 Editors/Reviewers / Modifier:
 Chris Miller Heartland Community College

Source:
Objectives
Students will be able to describe, in very simple
terms, “black body” absorption and radiation
and their relationship to solar thermal
applications.
 Students will be able to list the basic residential
applications for solar thermal technology.

Source:
Objectives
Students will be able to discuss the basic
requirements for passive solar architectural
design.
 Students will be able to discuss and describe how
active solar thermal technology works.

Source:
Thermal Applications = Using Heat

Typical Thermal Applications in Daily Human
Living – Residential Dwelling Applications:

Space Heating

Water Heating

Cooking
Contemporary Thermal Sources
•
The Heat Energy Necessary for Space Heating,
Water Heating, and Cooking is typically
Converted from:
–
–
–
–
–
–
–
Electricity
Natural Gas
LPG
Fuel Oil
Coal
Wood
Other Combustible Fuels
Challenges Regarding our Conventional Sources
of Thermal Energy
Limited, Finite Supply
 All (except nuclear-fission sourced electricity)
pump CO2 back into the atmosphere
 All result in one or more additional,
environmental pollutants
 The cost of all is continually increasing
 Most are not locally available and must be
transported in

Moving Heat Energy to
Where We Need it…

Heat is directed and moved via…



IR Radiation
Conduction
Convection
Conduction, and Radiation
Convection
Source: http://cobblearning.net/rlimpert/files/2010/02/a3a421b29aedfa72.jpg
Conduction, Convection, and Radiation
Source: http://cobblearning.net/rlimpert/files/2010/02/a3a421b29aedfa72.jpg
The Sun as a Source of Thermal Energy
•
•
•
•
•
“Black Body” radiation and absorption!
We see only reflected light
When we see “white” light, the “white” surface is
reflecting all frequencies of visible light
When we see “red” light, the “red” surface is only
reflecting the “red” frequency of visible light, and is
absorbing all the other frequencies of visible light
When a surface appears “black” it is absorbing all
the frequencies of visible light and reflecting none
“Black Body” Radiation and Absorption
“Black Bodies” absorb ALL frequencies
 At temps below 200o C, “Black Bodies” (all
bodies) radiate InfraRed frequencies
 InfraRed radiation is HEAT!

Source:
http://www.popsci.com/files/imagecache/article_image_large/files/articles/colorfire_485.jpg
Solar Thermal Technologies
•
The basic ideas behind solar thermal energy are:
–
–
Convert solar radiation into heat energy via Black
Body absorption
Trap the captured heat energy
•
•
•
–
Limit IR radiation losses
Limit Convective losses
Limit Conductive losses
Direct the captured heat energy into the desired zone
or material via IR radiation, and/or convection,
and/or conduction
Solar Thermal Technologies

Solar Space Heating vs. Solar Domestic Hot
Water Heating vs. Solar Cooking

Passive vs. Active Solar Thermal Applications

“Flat Plate” Solar Collectors vs. Concentrating
Solar Collectors
Solar Space Heating

Passive Solar Principles:






Insulate, insulate, insulate (especially the North wall)
Orient long axis of building E-W
Lots of South facing glazing
Thermal storage
Nocturnal insulation on South wall
Summer shading to avoid seasonal over heating
Passive Solar Principles
Source: http://www.energysavers.gov/images/five_elements_passive.gif
Passive Solar Principles
Source: http://www.solarbuildings.ca/c/sbn/img_db/alstonvale.JPG
Passive Solar Principles
Passive Solar Principles
Passive Solar Principles

Thermal Storage Media

Solid Thermal Mass

Trombe Wall

Water Columns, jugs, and barrels

Eutectic Salts
Passive Solar Principles
Passive Solar Principles
Source: http://www.solar-components.com/BLUETUB.JPG
Passive Solar Principles
Source: http://knowledgepublications.com/heat/images/Solar_Air_Window_Box_Collectors.gif
Active Solar Space Heating Principles

Same as Passive principles, but…


Add on external solar collectors
Add on fans or pumps to move fluid




Air or water or other FLUID
Different configurations of heat storage
May incorporate heat pumps
May be flat-plate or concentrating
Active-Solar Air-Heating Principles
Active-Solar Air-Heating Principles
Source: http://www.yoursolarlink.com/blog/wp-content/uploads/solar_air_heater.jpg
Active-Solar Air-Heating Principles
Active-Solar Space Heating
with Liquid Working Fluids
Source: http://www.solarage.co.uk/res/embedded/swhsystem.gif
Solar Domestic Hot Water Heating
•
•
Can be active or passive (thermo-siphon)
Can be open loop
–
•
Open loop can be drain-down configured for freeze
protection
Can be closed loop
–
–
Closed loop can be drain-back configured for freeze
protection
Closed loop can be freeze protected by using
antifreeze as the working fluid
Passive Solar DHW Heating
Batch Tank Heating
Thermo-siphon
Passive Solar Water Heating

Batch heaters
Passive Solar Water Heating

Batch heaters
Passive Solar Water Heating

Batch heaters
Source: http://www.byexample.com/library/photos/projects/batch_collector/bc_01697.jpg
Passive Solar Water Heating

Thermo-siphon heaters
Source: http://www.altensol.com.ph/?404=Y
Schematic diagram of a thermosyphon solar
water heater
Hot water
outlet
Storage tank
Auxiliary
Cold water
inlet
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Laboratory model
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Typical thermosyphon solar
water heater
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Active Solar DHW Heating
System Design Governed by Need for System Efficiency
and Freeze Protection
Active Solar Water Heating
Source: http://www.amecosolar.com/waterheat.jpg
What type of system would I use in my area?

Warm climates



systems similar to those shown previously
systems will differ in design
Cold climates

freeze protection becomes critical


Indirect systems with heat exchangers
Drainback and draindown systems
Warm climates
•Fluid in tank is
heated in collector
•Most common system
in temperate climates
Warm climates
This system is called a thermosiphon
system. It does not have pumps,
controllers, or any moving parts.
Water is heated and the density of the
hot versus cold water takes over from
there.
Works off natural thermosiphon
actions in moving the water heated in
the collector back to the tank and the
cold water in the tank to the collector.
Direct circulation system
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Cold climates
•Freeze protection
•Reduce Scale
•Non-potable fluids
Cold climates
Indirect system with heat
exchanger that contains
fluids in collector that do not
freeze. Heat exchanger is in
the water heater.
Drain-down system
When a freezing condition or a power failure occurs, the system drains
automatically by isolating the collector array and exterior piping from the
make-up water supply and draining it using the two normally open (NO) valves
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Indirect water heating system
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Drain-back system
Circulation continues as long as usable energy is available. When the
circulation pump stops the collector fluid drains by gravity to a drain-back
Intensive program: ICT
tank.
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Cold climates
Indirect system with heat
exchanger that contains fluids in
collector that do not freeze. Heat
exchanger is external to the water
heater.
Cold climates
In this system all the water in the
collector drains back into a reservoir.
T
M
P
PT
C
T
Drain Back Tank
Solar Tank
Cold Supply
Drainback system
Cold climates
In this system, all the
water in the collectors
drains out of the
collector.
Draindown system.
Cold climate
Another thermosiphon
system similar to the one
used in warm climates, but
this one has a heat
exchanger incorporated in
the system to protect the
collector during freezes.
Source: http://mashav.com/solar-energy/sirt.jpg
Stationary Collectors for
DHW
Flat Plate Collectors
“Paint” or Selective Surface
Evacuated Tube Collectors
Flat-plate collector
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Flat-plate Collectors
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Types of flat-plate collectors
Water systems
A
Glazing
Riser
Absorbing plate
C
Glazing
Riser
Absorbing plate
Insulation
Insulation
B
Glazing
Riser
Absorbing plate
D
Insulation
Glazing
Riser
Absorbing plate
Insulation
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Schematic diagram of an evacuated tube
collector
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Evacuated tube collectors
Source:
http://www.lightheat.com/home_heating/images/the
rmomax3.jpg
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Swimming pool heating -Another water heating application
Source: http://build-it.hit.bg/solar.html
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Concentrating Collectors
Non-Imaging Concentrators
Tracked, Imaging Concentrators
Refractive vs. Reflective
Refractive Concentrators
Refractive, Imaging Concentrators

Lenses!
Source: http://3.bp.blogspot.com/_vaXUruXsufA/SxOLacmQNyI/AAAAAAAAB5s/0mTAthc_JnI/s200/F_23_2.gif
Refractive, Imaging Concentrators

Lenses!
Source: http://oscar.iitb.ac.in/images/weeklyimages/Physics/single_lens.jpg
Refractive, Imaging Concentrators

Lenses!
Source: http://artofmanliness.com/wp-content/uploads/2008/04/magnifying-glass.jpg
Refractive, Imaging Concentrators

Lenses!
Reflective Concentrators
Non-Imaging…
Tracking not needed.
Flat plate collector with flat reflectors
Sun rays
Flat plate collector
Flat reflector
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Schematic diagram of a CPC collector
θc
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Reflective Concentrators
Imaging…
Tracking Required!
Parabolic Solar Concentrators

Reflective Imaging Concentrators


Specially-shaped, highly polished surfaces that
“reflects” light rays, focusing them to a very sharp
point on the light-source-side of the
reflector…MANY more W/m2 into a VERY small
mass or space = MUCH higher temperatures.
These are all based on the geometry of the parabola.


Line focused = HOT…single-axis tracking required
Point focused = HOTTER…dual-axis tracking required
Line-Focus Reflectors
Source:
http://www.reuk.co.uk/Oth
erImages/parabolictrough2.jpg
Source:
http://cache.io9.com/a
ssets/resources/2007/
11/suncollector.jpg
Source: http://teamsuperforest.org/superforest/wp-content/uploads/2010/10/parabolic-trough-500x334.jpg
Parabolic trough collectors
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Parabolic Trough System
Source: http://www.volkerquaschning.de/artikel/konze
nson2/abb2.jpg
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Parabolic trough collectors
Source:
http://www.tristategt.org/im
ages/NREL-Solar-Troughs02.jpg
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Parabola detail
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Receiver detail
Source: http://erenovable.com/wpcontent/uploads/2009/05/solarpower
plant-thumb.jpg
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Schematic of a parabolic dish collector
Sun rays
Receiver
Parabola
Two-axes
tracking
mechanism
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Point-Focus Reflectors
Source: http://keetsa.com/blog/wpcontent/uploads/2008/06/solar-dish-1.jpg
Solar-Thermal Process-Heat Applications
Solar cooking
 High temperature boilers for steam engines
 Low temperature boilers for ORC engines
 Stirling-cycle external combustion heat engines
 The Minto Wheel
 …and, MORE

Solar Cooking – Non-imaging
Source: http://www.builditsolar.com/Projects/Cooking/BillsPage.jpg
Solar Cooking -- Imaging
Source: http://wohnen.pege.org/2005-afrika/solarkocher.jpg
Solar Cooking, Single Hot Dog Scale
Source: http://westernpower.com.au/pluginkids/
Village- Scale Solar Cooking
Very High Temp Power Tower!
Source:
http://ec.europa.eu/energy/res/se
ctors/images/solar_3.jpg
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Schematic of central receiver system
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Tower detail
Source:
http://earth2tech.files.wordpres
s.com/2009/07/solarthermalge
nericnrel.jpg?w=250&h=159
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Heliostat detail
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Mini-Boiler
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Mini-Boiler
Source:
http://tonto.eia.doe.gov/energyexpl
ained/images/stock/solarth.jpg
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Central receiver-3
Source:
http://www.energy.gov/im
ages/gallery/25Years19961998/album_photo962_rdax_253x202.jpg
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Central receiver-4
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Central receiver-5
Source:
http://www.ecotec2000.de/gr
afics/10kW.jpg
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Mini-Boiler
Source:
http://bayern.zentru
mspartei.de/images/
flugzeug_sbp.jpg
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Mini-Boiler
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Mini-Boiler
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Organic Rankine Cycle Engine
Stirling Cycle Engine
The Minto Wheel
Design Problem
Commercial-size Solar Greenhouse
 Challenges:






Maximum sunlight means minimum structure
They typically melt off the snow load!
Nocturnal insulation in a 2,000 square foot building?
Thermal storage?
What would you do?