History of Passive Solar Energy - Scott Barber

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History of Passive Solar Energy
                                                                                  Scott Barber
                                                                         East Carolina University
                                                                Faculty Mentor: Michael Behm
                                                                         East Carolina University
ABSTRACT
Passive solar design, an idea within the growing trend of green building, is a creative way to use
the sun to our advantage, both for heating and cooling, based on the design of buildings. As green
building has continued to become more popular, many changes have been made to make the design
and construction of our buildings more environmentally and economically sustainable. This review
focuses on the development in passive solar applications, from its earliest appearances in ancient
Greek buildings to current designs that take advantage of radiation convection or acrylic panels.
There have been many passive solar developments that can be explored, and the innovative technol-
ogy today has brought about great advancements in the past few decades alone.This review presents
a compilation of information from a variety of sources that provide knowledge regarding the his-
tory of passive solar energy. As the popularity of green building continues to grow, it is essential to
develop an understanding of passive solar design, and other green building techniques, in order to
be equipped for the years to come.

                                                     and natural gas. This type of deterioration
P    assive solar systems are used to
     “collect, store and distribute thermal
energy by natural radiation, conduction
                                                     is not only evident in natural gas, but
                                                     also in many other common sources of
                                                     energy. Though many are aware of the
and convection through sophisticated                 decreasing amount of oil, most people
design and wise selection of building                assume there is an endless supply of coal,
materials” [9]. This definition, provided            nuclear, and other energy sources. It has
by J.K. Paul, sufficiently explains that             been estimated that there is enough coal
the idea of passive solar energy is the use          to last about 250 more years[14], enough
of natural processes, such as radiation,             oil to last approximately 44 years[5], and
conduction, and convection, to distribute            nuclear fuel to last 23 years[12], if the cost
thermal heat provided by the sun. Passive            is kept somewhat higher. Even if these
solar energy also involves blocking the sun’s        numbers are a low estimate, and enough
rays in order to provide cooling during the          energy sources remain for several more
summer. Incorporating solar energy into              centuries, there is still a need to find cleaner
our buildings will decrease the amount               sources of energy. What many people are
of money we spend on energy as well as               unaware of is the damage that our current
extend the time other sources of energy              energy sources cause to the environment[4].
will last.                                           The pollution and other byproducts of
  Due to increasing oil prices, rising gas           manufacturing usable energy from these
prices have become a common sight not                raw materials have dramatically affected not
only in the United States, but around the            only the atmospheric quality, but they have
world. The exploitation and misuse of our            also damaged the surrounding ecosystems,
natural resources is rapidly depleting our oil

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Scott Barber
whether they are forests, prairielands, or      manner. It is also helpful to understand
water habitats. Ron Jones, an architectural     specific savings in cost for buildings that
expert for sustainable building, explains       use passive solar energy. According to a
that humans have begun to further explore       document provided by Appalachian State
and understand the relationship between         University, a passive solar home could
the built environment and the natural           save as much as $160 per year by using
environment. In the past, we simply were        simply using movable insulation and low-
concerned about the effect of nature on         emissivity glass, glass that radiates low
buildings, but now are realizing the impact     levels of radiant thermal energy 11].
our buildings have on the environment.            In this paper, I overview the history
This is the key to sustainable design[6].       of passive solar design as well as review
   There is a plethora of renewable             and analyze technological information
energy sources that provide energy that is      regarding the use of solar energy. The
much better for the environment. While          goal of this review is to inform the reader
the mining and burning of coal and              of historical passive solar energy uses and
uranium leads to smog, acid rain, and air       to explain in greater detail what passive
toxins, renewable energy, including solar,      solar energy is and how it is applied.
wind, hydropower, geothermal, or even
renewable materials such as agricultural        CATEGORIZATION             OF     PASSIVE
products or biomass, results in little, if      SYSTEMS
any, pollution. These types of renewable
sources are becoming a pivotal aspect of the      To have a better understanding of
increasingly popular “green” movement.          passive solar energy, it is helpful to know
There are three parts of being green: being     how to categorize passive systems used for
acceptable economically, ecologically, and      this type of solar energy. While there are
socially. These three pillars make up the       specific techniques and systems that use the
sustainability movement, and help direct        sun’s energy in a passive way, they are all
decisions so that processes and materials       defined as being either direct gain, indirect
used are suitable in each of these areas. For   gain, or isolated gain.
example, when installing wind turbines,           Direct gain is the simplest application of
to completely fit within sustainability, one    passive solar energy, where the space of the
must take into consideration these three        building is directly heated by the sunlight,
ideas to ensure that the turbines will be       which most often enters through windows
economically efficient, environmentally         within the south-facing wall for buildings in
friendly, and socially acceptable. While a      the northern hemisphere[7]. Ideally, in this
wide variety of renewable sources exist,        approach, the materials within that space
they are not developed enough currently         ought to be capable of storing heat and
to provide materials and systems that           the air flow throughout the room should
are beneficial within the three pillars         distribute the heat. A representation of
of sustainability. However, one type of         direct gain is shown in Figure 1, which also
renewable energy does have the necessary        depicts the difference of the angle of the
progress to be used and still be considered     sun during the summer and winter, and
sustainable: passive solar energy. While        how an overhang can be incorporated into
many people are aware of active solar           the building design for further temperature
energy systems, such as solar panels, passive   control.
solar energy is a division of solar energy
that uses the sun’s energy in a more natural

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Explorations | Biology and Biotechnology
                                                and temperature regulation.
                                                   Isolated gain, depicted in Figure 3, uses
                                                solar collection and thermal storage that
                                                are separate from the actual living space,
                                                moving heat to the living space through
                                                natural or forced convection. Ventilation
                                                is also essential in this method of passive
                                                solar heat gain. An advantage to isolated
                                                gain systems is that they can be added to
                                                new and existing buildings[2].

    Fig. 1. Direct gain passive solar energy.

  For indirect gain, sunlight is most often
received by a south-facing wall, and as air
moves throughout the internal space, the
heat will then be transferred from the wall
to the living space[7]. For increased control
of indoor temperature, ventilation at the
top and bottom of the wall or other thermal
mass is included, assisting in regulating
the temperature. Figure 2 clearly displays        Fig. 3. Isolated gain passive solar energy.
indirect gain, the use of a thermal mass for
solar heat gain, as well as vents integrated        Regardless of the type of heat gain
into the thermal mass for air circulation       utilized, passive solar energy provides heat
and heat distribution.                          at little to no cost, aside from the slight
                                                variations in the design and construction
                                                of the building.

                                                HISTORICAL APPEARANCES OF
                                                PASSIVE SOLAR

                                                   Solar power has benefited civilizations
                                                for centuries, and the knowledge from our
                                                past provides foundational understanding
                                                of the sun’s energy to bring about our
                                                current understanding of solar power.
                                                The earliest known application of solar
                                                energy arose during the 15th century
                                                B.C. by the Egyptian ruler Amenkotep
                                                III, who “supposedly possessed ‘sounding
                                                statues’ that operated when the air in their
 Fig. 2. Indirect passive solar energy.         base pedestals expanded after exposure
Thermal wall with ventilation for airflow       to sunlight”[3]. Though this was merely

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Scott Barber
an accomplishment of aesthetic value,            Code commenced “sun rights” in order to
solar energy has also been used to distill       guarantee everyone would have access to
water as well as dehydrate agricultural          the sun. The last known use of solar energy
plants. Solar energy has been used in even       before the 1700s appears in North America.
more advanced, practical ways by many            The Anasazi Native Americans built their
civilizations to provide heat for homes,         homes in the side of the cliffs in what is
light fires, and even cauterize wounds. In       now known as the Colorado Plateau, where
the 5th century A.D., Socrates realized that     Utah, Colorado, Arizona, and New Mexico
“in houses that look toward the south, the       meet[9]. These south-facing buildings were
sun penetrates the portico in winter, while      placed within the side of the cliff to avoid
in summer the path of the sun is right over      the sun in the summer, but make use of
our heads and above the roof so that there is    the sun during the winter. It is clear that
shade”[8], and that initiated the use of solar   there was an early understanding of using
energy to heat homes.                            the sun for energy, and this knowledge
   Though the first recorded application of      and technology surrounding it increased
solar energy is in the 15th century B.C., the    significantly beginning in the seventeenth
next appearance wasn’t for several hundred       century.
years, where the historian, Plutarch,               Up to that point in history, through the
documented that virgins used cone-shaped         1200s, passive solar energy was used by
metal objects to start ritual fires during the   Egyptians, Greeks, Persians, Hindus, and
7th and 8th centuries B.C.[3]. During this       the Native Americans, following ancient
time the sun was used to distill water and       architectural teachings of           Aristotle,
dehydrate agricultural plants. A famous          Xenophon, and Vitruvius [9]. In the ancient
use of solar energy, while the event is still    historical appearances of passive solar
surrounded with reservations and disbelief,      energy uses, the architecture was geared
occurred in 212 B.C., when Archimedes used       towards using the sun and wind to alleviate
a “burning mirror” to set invading Roman         the extremes of the climate, but due to a lack
ships on fire. A similar story was recorded      of glass, they were unable to utilize the sun
in the 12th century, where Proclus, a Greek,     to the extent we can today. However, though
supposedly accomplished this achievement         most ancient civilizations lacked glass and
during the siege of Constantinople when          other technology that we use today, they
the Bitellius fleet was invading, using many     still made significant progress and provided
mirrors.                                         understanding and a good foundation for
   While there is no sure way to know whether    future developments regarding the use of
or not these feats happened, the recording of    solar energy.
this event sparked much curiosity, and soon           Beginning in the 17th century, interest
more applications of the sun’s energy were       grew in regards to using the sun as an
being recorded in history. For example, in       energy source, and though there was not a
77 A.D. Romans used “burning glasses” to         large amount of development within passive
cauterize wounds and light fires[3]. Another     solar techniques, significant progress was
one of the earliest applications of passive      made in active solar systems. The increased
solar energy was in the Roman atrium and         awareness of solar energy brought about
heated bathhouses in the first through the       by the experimentation with solar energy
fourth centuries, where large south facing       served also to make people conscious of the
windows let in the sun’s warmth to heat the      use of solar energy passively, as well, though
pool[9]. Solar energy became so well-known       there isn’t as much historical recording of
in the 6th century A.D., that the Justinian      passive solar energy during this time. In

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Explorations | Biology and Biotechnology
regards to active solar energy systems, the         It was in the late 19th century that passive
first “solar engine” was invented in 1615 by      solar energy began appearing more often
Salomon de Caux. This engine used glass           and in more noteworthy means. In 1880,
lenses to heat up an airtight metal vessel        theories surrounding solar houses began to
with water and air to produce a small water       appear, and it was in Salem, Massachusetts
fountain[3]. Though this lacked practical         that the idea of a glazed, south-facing wall,
use, it is significant because it was the first   as well as incorporating the requirements
published documentation of solar energy           for air flow between the glazing and the
after the fall of the Roman Empire. Also          wall first arose. Not only that, but professor
in the 17th century, physicist Athanasius         E.L. Morse was approved for a patent “for
Kirchas experimented with starting fire           the combination of a dark colored massive
with mirrors, and German mathematician            wall, an air space, glazing…and adjustable
Tschirnhaus worked with lens-type items           dampers by which the flow of air could be
to concentrate solar energy to melt various       controlled”[9].
materials[3]. Overall, the 17th century             A few years later, in 1896, the
included various experiments from                 thermosyphon water heater was invented,
different specialists who sought practical        the oldest and most widely used passive
applications of solar energy.                     solar device in the world, which was utilized
   In the 18th century, there was more            in World War I in Southern California
experimentation from many various                 to provide hot water to army camps[9].
professionals around the world. French            Many other southern states adopted this
scientist George Buffon worked to                 technology, as well as Japan and Australia,
determine whether or not the Archimedean          but the extension of natural gas lines and
feat could have been accomplished,                the cheap availability of electricity resulted
and determined that setting ships on              in a nearly complete elimination of its use.
fire was possible, but not very probable          However, due to increased prices in other
considering the lack of technology in             energy sources for providing hot water, this
212 B.C.[3]. Another Frenchman, Claude            device and its “active but similar offspring,"
Poillet, provided significant information         and the forced circulation solar water
that would assist in the development and          heater, are beginning to be used more[9].
application of both active and passive            These new developments provided more
solar energy. He determined the intensity         information, but also created specific
of the sun in reference to the geographical       ways that passive solar energy could be
position, and it is this association which        implemented into people’s daily lives. For
has been regarded “at least as important in       example, a home built in Massachusetts
solar utilization as the hardware itself ”[3].    was one of the greatest steps in passive
It was in 1767, just a few decades later,         solar design during the last few centuries,
that the first solar collector was invented,      providing a concrete and successful use of
built by Horace de Saussure, a Swiss              passive solar energy. Overall, the 1800s
scientist. This collector was used to heat        provided more research in solar energy than
food, and was used by Sir John Herschel in        perhaps any other time in history. However,
the 1830s, during his expedition in South         the following centuries resulted in a greater
Africa[13]. There continued to be a variety       diversification of the applications and uses
of research and investigation in regards to       of solar energy.
solar energy during this time, all providing
more information that would serve useful
in years to come.

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Scott Barber
MODERN DEVELOPMENTS                            In various adaptations and improvements
                                               that were made to these designs, double
   Since the twentieth century, there has      glazing, windows that could be opened,
been a great variety of fairly modern          and ventilating fans were used to maintain
passive solar developments. Though the         comfort. Unfortunately, there was a
deliberate practice of using solar energy      slight break in research and development
for heating within buildings was apparently    concerning solar energy during World War
forgotten outside of agricultural, the         II, even though there were still companies
1930s reintroduced this practice in the        practicing these methods.
relatively colder climate of Minnesota[1].        After World War II, despite the revival
The sudden increase in the application         of interest regarding solar heating, most
of and interest in passive solar energy        people were focused more on active
was a result of sealed, insulating windows     systems for solar energy and therefore
becoming available at a much more              passive solar heating was largely neglected.
reasonable cost. Due to the necessity of       The American Society of Heating,
windows within the application of many         Refrigeration,     and     Air-Conditioning
passive solar techniques, easily available     Engineers (ASHRAE), however, continued
windows allowed passive solar methods          to research the gain of solar heat through
to appear in residential architecture just     window placement, which has provided
before World War II[9]. The Keck brothers      foundational information for today’s
in Chicago were forerunners within the         strategies for determining solar heat gain
new appearances of passive solar energy,       through windows, and has resulted in
providing prefabricated buildings in the       multiple direct gain passive solar houses in
1940s. These buildings used large, south-      New Mexico[9].
facing windows with overhangs to admit            These homes implemented newer
sunshine in the winter but block it in the     technology      which     improved     them
summer months. They also included flat         significantly from their fairly inefficient
roofs that were made to be flooded during      predecessors built in the 1930s and 1940s.
the summer to decrease the amount of           For example fairly consistent temperatures
solar heat gain[9].                            were gained through concrete or adobe
   Though these and similar houses were        floors which absorb heat. Also, movable
being designed and constructed, they           insulation protected the house in times of
lacked the full potential and were less        exceptionally cold weather or when there
effective, mainly because the common           were extended days where clouds blocked
heating and cooling systems were readily       the sun[9]. The improvements in these
available at a much lower cost. Another        structures significantly increased their
notable progression within solar energy        practicality and effectiveness.
use in homes was the book entitled Your           In the decades following, there were
Solar House, funded by Libbey-Owens-           continued discoveries and inventions
Ford Glass Company. This book included         regarding solar energy. In 1954 photovoltaic
forty-eight designs for homes to utilize       technology was first revealed, as Daryl
direct gain solar energy, one design for       Chapin, Calvin Fuller, and Gerald Pearson
each state within the United States at that    invented the first solar cell that converted
time[9]. Again, these designs were not ideal   energy from the sun to provide electrical
applications of solar energy, primarily        power. The following year, Western
because there was no consistent way to         Electric began selling licenses for silicon
control temperature within the buildings.      photovoltaic technologies. It was during

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Explorations | Biology and Biotechnology
this time that architect Frank Bridgers          monitoring, and rewarding sustainable
designed the first commercial office             building. In 1985, Austin Energy, located
building that used solar water heating and       in Austin, Texas, was the first residential
other passive solar designs[13]. It is worth     energy efficiency program[6]. In 1991, this
noting that these passive solar systems are      organization further developed and became
still in operation within this building today,   known as Austin Energy Green Building®.
and this office building has been recognized     Since that time, many more programs
in the National Historic Register as the         have begun, such as the Advanced Energy
world’s first solar heated office building.      Corporation located in Raleigh, NC, the
   Since these improvements, the most            Southface Energy Institute in Atlanta,
noteworthy addition to passive solar             GA, and the Solar Living Institute in
energy is the Trombe wall. Developed by          Hopland, CA. In 1995, the United States
Frenchman Felix Trombe, based on the             Environmental Protection Agency began
work of Edward Morse in the 1880s, this          the Energy Star program, which evaluates
wall faces the sun and essentially absorbs       the energy use and efficiency of buildings.
the sun’s heat and releases it inside the        Since the Energy Star program is limited to
building at night[9]. Aside from slight          energy, the United States Green Building
alterations, most passive solar techniques       Council (USGBC) was founded in 1993 and
have remained the same and have only             within that, the Leadership in Energy and
varied in regards to application. Figure 4       Environmental Design (LEED) program
shows a modified Trombe wall that utilizes       was founded in 1998[6]. These programs
a glazing material to collect solar heat and     have proved a key role in encouraging and
vents to provide air flow and distribute the     rewarding sustainable design, including
heat to the interior room. This type of          passive solar energy practices.
Trombe wall is a very efficient way to take
advantage of passive solar energy.               PASSIVE SOLAR APPROACHES

                                                    Although there are many different
                                                 aspects of passive solar energy as well as
                                                 the three pillars for producing sustainable
                                                 passive solar energy, there are five basic
                                                 approaches to forming these types of
                                                 passive systems: direct gain, thermal storage
                                                 walls, solar greenhouses, roof ponds, or
                                                 convection loops. These techniques can be
                                                 either direct gain, indirect gain, or isolated
                                                 gain, based on how they collect, store, and
                                                 transmit thermal energy [9]. These methods
                                                 are a result of the extensive research and
                                                 advancements throughout many centuries,
                                                 bringing us to the understanding we have
  Fig. 4. Modified Trombe wall using             today, allowing us to use the sun’s energy
exterior glazing and air vents for air flow.     efficiently and responsibly.
                                                    Direct gain is the simplest application of
  A noteworthy aspect of passive                 passive solar energy, and as such is the most
solar design is the many programs and            popular. Direct gain is beneficial because it
organizations devoted to encouraging,            is not only simple, but it also has a relatively

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Scott Barber
low cost. However, direct gain struggles          could serve beneficial for both heating
because it cannot control temperature             and cooling by adding or removing the
as effectively due to of a lack of thermal        insulation during summer and winter, or
storage. Other potential problems that may        day and night.
arise include undesirable lighting during            The final approach for passive solar
the day such as glares, as well as discoloring    techniques is the convective loop, which uses
of fabrics due to extensive ultraviolet           a thermo siphon, a machine that circulates
rays[2].                                          water, to move heat from the collection
   The second common approach to passive          point to a storage area. Water heaters often
solar energy involves using a thermal storage     use this idea, as it is very inexpensive and
wall, which essentially uses a material that      reliable, more so than many other types
absorbs the sun’s heat after it has passed        of water heaters commonly known. This
through the glazing. The wall may be              system works well without needing pumps
black or another dark color to assist in its      or controls[9]. Air convention loops often
absorbing, or it may even consist of water        combine passive collection/storage with
held in masonry or other containers[2].           active distribution to provide a simple but
Regardless of the absorbing material, its         effective system to provide temperature
purpose is to absorb the temperature and          control for a building.
release it into the interior room. This assists      Overall, these five types of applications of
in controlling temperature and reducing           passive solar energy can be very beneficial
temperature extremes, as well as reducing         to include in many different climates and
the negative effects of direct gain: glare or     situations. When applying these ideas to
undesirable lighting and material damage          buildings, it is important to be aware of the
due to the ultraviolet light. While direct        strengths and weaknesses of each of these
gain can heat up a room much quicker, it          applications. It also may be very feasible to
is much more difficult to control, which is       combine a variety of these approaches in
a benefit of using a thermal storage wall.        order to utilize their strengths and develop
Often, windows are included in this wall          a well-rounded passive solar building.
to combine direct gain with the thermal              The majority of all passive solar energy
storage to incorporate the benefits of            techniques are applied during the planning
both[7].                                          and construction process of the buildings,
   Using a roof pond is the third common          because the most important aspect of
approach to passive solar techniques[2].          a building is its location and direction.
It may or may not include the physical            However, there are a few options that
presence of water on the roof, but where          provide heating from solar energy for
there is not water present, movable               pre-existing buildings. By adding larger
insulation is required on the roof.               windows or double-glazed, low-emittance
Essentially, this technique relies on             windows on the south wall, passive solar
gathering solar heat through the roof, but        energy can be utilized. The double-glazed,
with insulation that prevents too much heat       low-emittance windows have the ability
from collecting during the hotter summer          to allow heat to enter into the building
months [2]. There have also been studies          but reduce the amount of heat lost to the
and research in New Mexico and Arizona,           outside. Also, planting deciduous trees,
testing various active and passive systems        trees that shed their leaves in the winter,
to control the amount of heat transferred         on the south side of a home will provide
through the roof. This type of system             shade from the sun during the summer but
would be used for a flat roof, ideally, and       allow the sunlight to enter into the windows

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Explorations | Biology and Biotechnology
during the winter. Blocking in windows on         solar for heating or cooling. However,
the north side of a home may also assist in       pairing up passive solar aspects with a
solar heating, though doing so may not be         back-up heating system, shading devices
aesthetically pleasing.                           or operable windows will greatly increase
                                                  the amount of control one has in regards
PASSIVE SOLAR ENERGY: IS IT                       to temperature[2]. Also, passive solar
WORTH IT?                                         heating also maintains a warmer floor,
                                                  which is desirable. Most heating systems
   While passive solar energy is growing in       used today can lead to large floor-to-
popularity within the green movement and          ceiling temperature differences, resulting
has improved significantly in the last few        in discomfort at the floor level. On the
decades, there are still doubts surrounding       contrary, passive solar systems use materials
its viability and effectiveness. The primary      that absorb heat, and therefore the floor is
arguments that are made in favor of using         warmer and more comfortable[2].
passive solar energy are divided into                One of the greatest attractions of passive
economic, architectural, and comfort/             solar energy is the fact that it is very
health categories. In general, passive            environmentally friendly; it is a renewable
solar energy is very beneficial because it is     energy source and does no damage to the
inexpensive and has little, if any, impact on     environment around it[6]. By using passive
the environment.                                  solar energy rather than a common heating
   When observing the economic aspects            or cooling system, there is a great reduction
of passive solar design, it is important to       in the consumption of fossil fuels and the
remember that each building is different,         production greenhouse gases and other
depending on construction and materials           pollutants[6]. Overall, passive solar energy
used. However, the benefit to passive solar       has few disadvantages and its advantages
energy, as opposed to active solar energy         are both economical and environmentally
or other types of renewable sources, is           friendly.
that it requires no additional cost for
upkeep; the costs are the same as the             FUTURE TRENDS
general maintenance costs of any building.
It is possible to save money long-term              While there has been a dramatic amount
simply by taking passive solar systems into       of progress and development throughout
consideration for the design process[6].          history regarding passive solar energy, by
Changing the direction of the structure           observing where technology is today, one
alone, in order to gain more heat from the        can only wonder how much more progress
sun on the southern part of the building,         can be made. While there certainly will be
can make a huge difference in collecting          improvements in materials, it appears that
solar heat. Essentially, passive solar energy     the techniques have currently reached a
only requires a slight increase in cost, if any   plateau. However, when asked “What is it
increase at all, to incorporate these systems     that we really require from scientists and
into the design and construction of the           technologists?” economist E.F. Schumacher
building.                                         provided guidance into the improvements
   In terms of temperature within the             of passive solar energy: “We need methods
building, some people may be hesitant             and equipment which have the following
to use this technology, mainly because it         characteristics: they are cheap enough
isn’t easy to control the temperature of          so that they are accessible to virtually
a room which is dependent on passive              everyone, they are suitable for small scale

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Scott Barber
applications, they are compatible with           With this in mind, passive solar practices
man’s need for creativity, and they are not      within sustainable design will become more
heavily dependent on natural resources”[10].     common, and industry leaders around the
Passive solar energy certainly has the           world will incorporate sustainable practices.
potential for meeting these requirements.        It is important for the future of passive
   The design of passive solar buildings,        solar design that those involved in the
based on the materials and technologies          design and construction of buildings to be
available today, will remain consistent for      certified in sustainable design, for resources
the next several decades. The strategies         and products used to be sustainable, and
and techniques being used today will be          as a result, the structures will be more
replicated in various ways depending on          sustainable as well.
location and availability to maximize the
benefits of passive solar energy. One can        CONCLUSION
assume that when new technologies arrive,
the design of passive solar buildings will          Throughout history, mankind has
adapt to incorporate them to maximize            benefited from and worked to harness
their efficiency. However, the specific          the sun’s energy in order to create a more
design for buildings regarding passive solar     enjoyable living space and save energy. Solar
energy has climaxed for the present time.        energy has been used for centuries and has
   The further development of passive solar      only improved with time, as researchers
energy is reliant on new technologies and        and scientists have developed processes
the development of more appropriate,             and materials to improve the quality and
efficient resources. One of the newest           effectiveness of solar energy. Using solar
developments that will continue to grow and      energy, specifically passive solar energy, is a
improve passive solar use involves window        very cost efficient way to take steps towards
glazing. Low-emittance coatings, known as        sustainability, and as the green movement
low-E coatings, are metallic oxide films that    continues to develop and expand, passive
are installed on windows to reduce from          solar techniques will be utilized more and
within the building while still allowing solar   more throughout the United States and
heat gain. These coatings do not affect the      in nations around the world. It is helpful
visual aesthetics of the window, yet provide     to realize the history in regards to passive
valuable benefits. There are also double-        solar energy, and the benefits that can be
glazed windows filled with argon gas, which      gained by applying passive solar energy.
provide the same benefits as the coatings on        Overall, the various types of passive
the windows and can be used together to          solar energy have unique strengths and
increase efficiency. As these technologies       weaknesses. Direct gain, the simplest
continue to improve, passive solar energy        application of passive solar energy, provides
will become more beneficial and effective.       quick, economically friendly, inexpensive
   It is also important, however, to recognize   heating for a home. The main disadvantage
the role that green building programs will       is its difficulty in providing adequate control
serve in the continuation and expansion          of the environment. Indirect gain, a slightly
of passive solar practices. Certifications       more complicated use of passive solar
and recognition within these programs            energy, goes beyond direct gain and offers
are available for the buildings being            a more stable environment with better heat
constructed, the professionals who design,       control. However, indirect gain requires
build, and remodel those buildings, and the      greater planning and also takes longer
products used for the buildings as well[6].      to heat up a room or home. The third

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Explorations | Biology and Biotechnology
application, isolated gain, delivers even      passive solar energy requires an evaluation
more control and stability in controlling      for each building in regards to feasibility
the indoor environment. This, too, requires    and usefulness. They can certainly be
further planning and is more expensive to      useful in many applications, and are worth
construct.                                     considering in the planning process.
  The five strategies used for passive solar     Passive solar energy will continue to
energy, direct gain, thermal storage, solar    grow and change, providing inexpensive,
greenhouses, roof ponds, and convection        sustainable alternatives for common
loops, all have their own advantages and       heating and cooling systems. As technology
disadvantages as well. The main drawback       improves and awareness increases, passive
to implementing these strategies into a        solar energy will become more widely used
building is a need for further planning and    throughout the country and around the
specific materials. However, this increased    world. It is certainly a viable option for new
initial cost only increases the long-term      construction, and will continue to assist in
savings for a building using passive solar     saving energy for many.
energy. The use of these approaches to

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