The Sun Emulator is
a powerful tool for promoting the use of solar responsive design. This
particular heliodon is useful for both the initial teaching of solar geometry
and for the actual design of buildings and communities that are in harmony
with the sun. Its conceptual clarity as a teaching and design tool comes
from the fact that it is a simulation of our everyday experience of how
the sun relates daily and seasonally to a building. The use of physical
models makes the experience both interesting and understandable for everyone.
The Sun Emulator can be used by architecture schools, building schools,
science museums (especially the hands-on type), energy resource centers,
and practicing professionals (architects, builders, and developers).
What
is a Heliodon?
Many different heliodons
exist and almost all utilize one light to simulate the sun. Since the
three variables of latitude, time of year, and time of day determine sun
angles, a heliodon must be adjustable for all three factors. Only a few
heliodons exist where the model is fixed and the light moves along three
axes to adjust for all variables. In most heliodons, however, the model
is rotated about one, two, or three axes instead of only moving the light
(Fig. 1). The disadvantage of these types of heliodons is that they do
not match our real world experience and therefore such heliodons are not
"conceptually clear." They are neither very convincing to the
uninitiated nor do they effectively teach the basic pattern of solar geometry
as related to a building.
Fig. 1
This type of
heliodon tilts the model for the latitude
adjustment, rotates the model for the hourly adjustment,
and moves the light vertically for the annual adjustment.
Fig. 2
This type of heliodon uses
multiple lamps to simulate the daily and annual motion of the sun. For
latitude adjustment the
model table can be tilted a maximum of 10 degrees each way.
More
than twenty years ago, the author built a heliodon with about 130 lights
to simulate the sun every hour of the 21st day of all twelve months (Fig.
2). Thus, electrical switches control for the variables of time of day and
year. The model table was still tilted for the latitude adjustment. Although
"conceptual clarity" was greatly improved, there are a number
of problems with tilting the model. With too much of a tilt, some of the
conceptual clarity was lost, some lights moved below the horizon, and, of
course, the model had to be carefully glued together and fastened to the
table to keep it from sliding. Recognizing the weakness of a tilting table,
the author developed over the last ten years a heliodon where the model
of the building is placed and remains stationary on the table, while the
light moves to simulate the sun's travels across the sky (Fig. 3). Although
Copernicus would be upset, this situation fits perfectly with our daily
real-world experience, and thus it allows us to form a mental model of the
solar geometry that can be used for the design of buildings. While some
heliodons accomplish this same goal with the use of only one light to simulate
the sun, it turns out better to use seven lights to simulate the sun at
different times of the year.
Fig. 3
The Sun Emulator
simulates our real-world
experience by keeping the building model
stationary while the lights move to simulate
the sun's apparent motion across the sky.
Why
Heliodons?
Energy consumption
is the primary cause of global warming, and buildings use over a third
of all the energy consumed in the United States, which is primarily used
for heating, cooling and lighting. Solar responsive buildings can significantly
reduce this energy demand. They can harvest the winter sun for heating,
they can reject the summer sun to reduce the cooling load, and they can
collect a small amount of quality daylight year-round to replace most
of the electric lighting during daylight hours. How do we teach developers,
builders, and architects the basic concepts that will allow them to design
solar responsive buildings rather than buildings with energy guzzling
mechanical equipment and electric lighting, and how do we convince owners
to request such buildings? Heliodons are powerful tools for demonstrating
the potential and logic of solar design to people of any age or education
level.
The
Sun Emulator
The author has developed a
new kind of heliodon, called the Sun Emulator, which is especially useful
for both the initial teaching of solar geometry and for the actual design
of buildings and communities that are in harmony with the sun. It is an
exceptionally powerful teaching tool because of its conceptual clarity
in the use of physical models that makes the experience both interesting
and understandable for everyone. The Sun Emulator can be used by architecture
schools, building schools, K -12 schools, science museums (especially
the hands-on type), energy resource centers, and practicing professionals
(architects, builders, and developers) .
Because the Sun Emulator uses
seven rings to simulate the 21st day of all twelve months, the heliodon
is a 3-D model of the sun paths. At an instant, one can tell that the
sun comes only from a part of the sky often called the solar window. It
is also easy to see which part of the sky the sun shines from during the
overheated period, which part of the sky in the underheated, and equally
important which part of the sky the sun never shines from. It is also
easy to show how these regions of the sky move up and down with changes
in latitude. It is most important to understand that any specific sun
angles are not very meaningful and potentially misleading. For example,
June 21 at 12 noon is not representative of the summer condition although
frequently used in graphical approaches to solar design. Rather, it is
very important to understand that the sun must be rejected whenever it
comes from the summer region of the sky. The size of this region is a
function of climate. Similarly, the sun angle of Dec. 21, 12 noon is not
especially meaningful because we want to collect the sun when it is coming
from the winter region of the sky.
By rotating the cradle holding
the rings, it is easy to understand how to design a solar responsive building
anywhere from the equator to the poles. It is instantly obvious that at
the equator, north and south windows receive equal amounts of sun over
a year, while north, south, east, and west windows all receive equal amounts
of sunlight on any day at the north and south poles. Thus the Sun Emulator
is a powerful teaching tool even before its lights are turned on.
The Sun Emulator clearly shows not only the daily symmetry of the sun's
travels across the sky but also the annual symmetry where the sunpath
for Nov. 21 is the same as Jan. 21 and May 21 is the same as July 21,
etc. It is for this reason that only 7 rings (sunpaths) are needed to
simulate the 12 months. This heliodon also shows how for six months of
the year the sun shines into north windows at all latitudes even if it
is only for brief times and at very glancing angles. Many people erroneously
believe that the sun never shines into north windows. For hot climates
this fact is of great importance as the north shading sails of Will Bruder's
Phoenix Central Library beautifully show. It is also easy to understand
how the length of day is a function of not only time of year but also
latitude, except of course, for the two days each year called the equinoxes.
All this can be understood within minutes by any person, of any age, and
any educational level.
Unlike graphical, verbal, or mathematical explanations, learning from
a "conceptually clear" heliodon is easy, quick, leaves a profound
understanding, and will be retained far better because it does not depend
on rote memory but a god's-eye-view of the relationships of a building
with its constantly changing solar environment.
Applications
The Sun Emulator is an effective
tool for:
· teaching solar responsive design principles
· teaching solar geometry
· designing shading systems
· designing for solar access
· designing for the direct-beam component of daylighting
· designing site plans for solar responsive communities
· presentations that convincingly demonstrate the soundness of
a solar design
Although the Sun Emulator was
developed primarily for architecture students it is appropriate for a
much wider audience, as will be discussed below. For architecture, landscape
architecture, planning, and interior design students a heliodon has three
separate applications: the initial learning of concepts and principles,
the design process, and presentation. As was described above, the Sun
Emulator is an excellent teaching tool. As a design tool, it can be used
to actually assemble a design as, for example, when the length of an overhang
is determined on the model by a trial and error method. Or the heliodon
can be used as an analysis tool where a design developed away from the
device is tested for its performance. In my own classes, I have students
test models of designs developed previously in studio. After the analysis
establishes what works and what doesn't, the students redesign their projects
to be more solar responsive. Next, fast and dirty study (not presentation)
models are built and again tested on a heliodon to determine what weaknesses
remain for further redesign. The most popular application among the students
is for presentation purposes. They photograph their models to document
their designs' solar responsiveness for juries and their portfolios.
Homebuilders are another major
user group. Most homebuilders are in fact designers. They often decide
which building design will be used, what its orientation will be, where
it will be located on a lot, what trees will be left standing or where
trees will be planted, etc. Each of these decisions would benefit greatly
from the understanding of solar responsive design principles. Developers
are even more in need of this knowledge because street orientation has
major consequences, since it will usually determine orientation of the
buildings which are almost always aligned with the street rather than
the sun. One of the most successful developments in the second half of
the twentieth century, Village Homes in Davis, California, was designed
by means of physical models tested for solar responsiveness.
If homeowners and architectural clients are not interested in solar responsive
design, then there is little incentive for building professionals to provide
such designs. Thus it is imperative that all who finance or control the
design of buildings should be knowledgeable about the potential benefits
of working with the sun, and ironically, many of these benefits are free.
In effect almost everyone should understand and thus believe the financial
and environmental benefits of solar responsive design. This widely held
understanding, I believe, is best accomplished by means of a "conceptually
clear" heliodon. If the hands-on science museums for children had
heliodons, children would understand early on and in a lasting manner
the logic of designing with the sun. Schools too could use heliodons in
their earth science or physics courses. If children routinely learned
about these principles, we would have future generations that would demand
the benefits of solar responsive design because they would know that they
are real and achievable.
Description
The Sun Emulator consists of
a circular cradle supported at two pivot points on a rigid frame. The
cradle can rotate 90 degrees to adjust for latitudes from the equator
to the poles. The cradle holds seven hoops that simulate the sun's travels
on the 21st day of each of the 12 months. The hoops are turned by hand
to adjust for the hours of each day. In its storage mode (Fig. 4), the
overall dimensions are 74 inches long, 70 inches high, and 28 inches wide.
For more specifications, see www.hpd-online.com.
Fig. 4
The Sun Emulator
in its storage mode. The
cradle with the 7 rings is set for 0 latitude,
as it would be to simulate solar geometry at
the equator.
Fig. 5
The cradle is rotated to
select the desired
latitude.
Directions
for Use
Printed directions for the
use of the Sun Emulator are extremely brief and almost unnecessary because
this heliodon is a model of our everyday reality. First, the model to
be tested is placed at the center of the round table, its south orientation
aligned with that of the heliodon. Then the cradle holding the seven rings
is adjusted for the correct latitude by means of a single locking knob
(Fig. 5). Next, a twelve position rotary switch is used to choose the
sunpath for the 21st day of any desired month (Fig. 6). To simulate the
daily motion, the appropriate hoop is rotated by hand from sunrise to
sunset (Fig. 7). Other hoops are then rotated to investigate solar access
and shading patterns at other times of year. To see what happens through
the year at a particular time of day, the lights of all the hoops are
aligned and the rotating switch is turned to simulate the annual travel
of the sun up and down the sky.
Fig. 6
The time-of-year
adjustments are made with the 12 position rotary switch. The 21st day
of each month can be selected.
Fig. 7
The hourly adjustments are
made by
manually rotating the appropriate hoop.
Additional
Information
For more information contact:
Norbert Lechner
119 Dudley Hall
Auburn University, AL 36849-5315
334-844-5378
lechnnm@auburn.edu
How
to Buy
The
Sun Emulator can be purchased through the manufacturer,
