active solar thermal systems - …wtgzik.pairserver.com/courses/373f16/373-solarthermal.pdf ·...

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Ball State Architecture | ENVIRONMENTAL SYSTEMS 2 | Grondzik 1

ACTIVE SOLAR THERMAL SYSTEMS


Reminder—Solar versus Terrestrial Radiation

Heating, Cooling, Lighting: Norbert Lechner

shorter ……………… longer

wavelengths

not

to s

cale

the energy action is here

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Reminder—Solar Radiation Components

lots of energy

some energy


Reminder: Solar Paths

NORTHERN HEMISPHERE

orientation and tilt of a surface will affect magnitude of received solar energy

focus of sunpath diagrams is direct solar

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Possible Solar EnergyConversions

• Helio-chemical conversion– Solar radiation to chemical energy

• Photosynthesis: food, biomass

• Helio-electrical conversion– Solar radiation to electrical energy

• Photovoltaics (PV)

• Helio-thermal conversion– Solar radiation to heat energy

• Passive and active approaches


Active Solar Thermal Systems

Configuration Options• Water or air as the heat exchange medium

• Flat-plate or concentrating collector configurations• Fixed or tracking collector installations

Potential Applications• Domestic hot water (potable water)

• Space heating• Space cooling (via an absorption chiller)

• Process heat (product production)

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Solar Thermal System Components

These systems involve an energy SOURCE (solar radiation—a renewable resource with zero carbon emissions)

harvested by acollector with aperture (the aperture defines system “size”)

and absorber (to convert radiation to heat) that isconnected to heat storage (generally required by the nature

of the cyclical solar source) and often involving abackup heat source (for extreme conditions). The collected heat is moved via a heat transfer medium (air or water) that is part of the DISTRIBUTION and DELIVERY subsystems.

CONTROLS make the whole thing work well.

the focus herein is on active systems, with “dedicated-purpose” components


Example—Air-Based Collector

inlet duct

outlet duct

flat plate collector, fixed, used for space heating

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Air Collector System Schematic

solar radiation is captured and converted to heat in a collector—then conveyed via hot air (in ductwork) to storage in a masonry mass (rock bed)—and then delivered where the heat is needed

cooler air returns to the collector to be reheated, and the cycle continues

there is no solar heatingpotential at night; thus the need for heat storage

supply air

return air


Example—Solar Rock Bed Storage

air has virtually no thermal capacity, but hot air can transfer its heat to rocks; this type of storage seeks a balance between density (to provide thermal capacity) and porosity (to permit air flow without excessive pressure loss)

peop

le.u

mas

s.ed

u/

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Air Collector System Diagram

source

storagedelivery

distribution

controls

backupsource


Backup? Storage?The backup heat source shown in the previous schematic is

a necessary part of a solar thermal heating system—if space conditions need to be maintained under any and all

weather conditions. This adds to the first cost of the system (the system has both solar-source and

conventional-source components). The need for such a backup should be carefully considered.

The basic elements of a solar heating system (source, distribution, delivery, control) are common to all heating

systems. Storage, an additional element (and expense), is required to deal with the variable and cyclical nature of

the energy source (the sun). It is very difficult to eliminate thermal storage.

a first-cost analysis will seldom favor active solar thermal (more investment); a life-cycle cost analysis may often favor active solar thermal (reduced energy)

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Example—Water-Based Collector

housing

fluid outlet

fluid channels

(tubing)

insulation

glazing(aperture)

…it was that way

when I found it

collector surface(absorber)

flat plate collector, fixed, use not obvious (could be space heating or domestic hot water)


Water Collector System Schematic

solar radiation is captured and converted to heat in a collector … then conveyed via hot water to storage in a tank; a heat exchanger (radiator, etc.) is needed to get heating effect into the room

as with an air system, the water flows in a cyclical (but always closed) loop

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Water Collector System Diagram

showing common elements of source,distribution, and delivery—plus storage and a backup source typical of a solar system (controls would also be provided)


Example—Solar Hot Water Storage

one hopes (aesthetically) that this is a retrofit installation;

but in any case storage tanks can be large—especially in a residential occupancy where

times of greatest use (mornings and evenings) do not match time of greatest solar collection (daytime)

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Example—Evacuated Tube Collectors

this type of collector provides some concentration, has low losses, high efficiency

www.solardecathlon.org/


Example—Custom Collector

aperture area = absorber area … this is the definition of a flat plate collector

the collector serves as roofing and structure (for a

mechanical room)

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Library, Los Alamos National Lab

a quite large flat plate solar collector array, integrated into a building usingcustom collectors (see previous slide)


Los Alamos Solar System

unde

rsid

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lect

ors

is r

oof o

f mec

hani

cal r

oom

;da

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yel

low

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men

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re fl

uid

head

ers

clos

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of c

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owin

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Active Solar Aestheticsspace heating systems


Building-ScaleTracking, Concentrating Collectors

Fresnel lens concentrating and tracking collector (one-axis tracking; only the orientation changes), may be used for space cooling and space heating

image shows small part of a large roof-mounted array

absorber tube (contains water)

faceted (Fresnel) lensconcentratesdirect solar radiationonto absorber tube

axis of rotation

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District-Scale Tracking, Concentrating Collectors

test

inst

alla

tion,

San

dia

natio

nal L

abs

concentrating and tracking collector,with one axis tracking(the tilt changes)

axis

of r

otat

ion


District-Scale Tracking, Concentrating Collectors

mun

icip

al p

ower

gen

erat

ion,

Aus

tral

ian

outb

ack

parabolic concentrating and tracking collectors (two axis tracking)

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Concentrating Solar Power (CSP)Collector Array

flat, concentrating and tracking (two axis) solar collectors with tower receiver; used for commercial electricity production

power tower with heliostats, Sandia (NM)


Concentrating Solar Power (CSP)Collector Array

CSP installation, Morocco)

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Active SolarAesthetics

one of the first actively solar heated buildings in the US; collector panels were site fabricated and are actually refrigerator “coil” panels


Active Solar Aesthetics

domestic hot water heating

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Active Solar Collector Efficiencies

note relative efficiency of various collector types and drop in efficiency with difference in fluid versus ambient temperature; compare these efficiencies to PV modules (≈18%)

sola

rpro

fess

iona

l.com


End note

A cat sunning himself in the doorway of a barn knows all about solar

energy. Why can’t man learn?

E.B. White

As quoted in The Return of the Solar Cat Book

Michael Toland Grondzik

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the DOE Solar Decathlon as a Showcase of Solar Homes

the following slides are provided as a window

into current design thinking about what a solar-powered

single-family residence might look like;

The majority of the collectors shown are PV (necessary to

reach the net-zero-energy goals of the competition), but

most of the homes also include solar

thermal collectors (to provide domestic hot water)

these projects will not appear on the quiz


2005 Solar Decathlon Entries

all 2005 images from USDOE WWW site:

http://www.solardecathlon.org/highlights_2005.html

all 2005 entries (buildings) had both solar thermal and PV

collectors; consider theaesthetics of the various building

designs and integrations

sited in Washington, DC

(National Mall)

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Cal Poly San Luis Obispo


Concordia and Universite de Montreal

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University of Colorado


Cornell University

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Crowder College


Florida International

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New York Institute of Technology


Pittsburgh Synergy

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Rhode Island School of Design


Universidad de Madrid

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Universidad de Puerto Rico


University of Maryland

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University of Michigan


Rolla (Missouri) Consortium

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University of Texas at Austin


Virginia Tech

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2009 Solar Decathlon: Illinois

sited in Washington, DC

(West Potomac Park)


2009 Solar Decathlon: Illinois

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2009 Solar Decathlon: Germany


2009 Solar Decathlon: Germany

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2009 Solar Decathlon: Cornell


2009 Solar Decathlon: Cornell

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2013 Solar Decathlon: Louisville / Ball State

sited in Irvine, CA

(Orange County Great Park)



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2015 Solar Decathlon: Buffalo


2015 Solar Decathlon: Buffalo

PV

solar

thermal

active solar thermal systems - …wtgzik.pairserver.com/courses/373f16/373-solarthermal.pdf ·...

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