These reports may be ordered, free of charge, from the Simulation Research
Group at Lawrence Berkeley National Laboratory.
Kathy Ellington
MS: 90-3147
Lawrence Berkeley National Laboratory
Berkeley, CA 94720
USA
Fax: 510-486-4089
Email:
info@gundog.lbl.gov
LBL-33906
RECENT IMPROVEMENTS IN SPARK: STRONG COMPONENT DECOMPOSITION,
MULTIVALUED OBJECTS, AND GRAPHICAL INTERFACE
Abstract:
The Simulation Problem Analysis and Research Kernel (SPARK) environment
for simulation of nonlinear differential algebraic systems has been
revised to improve modeling convenience, modeling flexibility, and
solution efficiency. Solution efficiency has been enhanced by
automatic decomposition of the problem into strongly connected
components, characterized as separately solvable subproblems. The
normally-constructed data flow graph in SPARK allows such components to
be identified and placed in the correct order for sequential solution
resulting in significant speed-up for problems that are not strongly
interconnected. Modeling flexibility has been enhanced by adding
Multi-valued Objects. Whereas conventional SPARK objects represent
single equations and produce a single result, this extension allows
more complex objects which themselves solve simultaneous sets of
equations for multiple results. The need for such objects arises
when submodels are to be solved independently of the SPARK solver;
e.g., to use a specially tailored algorithm. With regard to
modeling convenience, the graphical user interface now allows model
definition by selection and placement of object icons in a
graphical window in an X-windows environment. These objects can be
connected with macro links comprising multiple problem variables.
The resulting problem is then translated into a Network Language
Specification file for SPARK processing.
LBL-32616
OPTICAL PROPERTIES DATABASE
Abstract:
The optical properties of glazing materials are essential to any
evaluation technique for calculating the performance of glazing
materials and window systems. Furthermore, the basic nputs for
calculating system performance and comparing evaluation
techniques must be the same. An optical properties database
provides consistent data to researchers and eliminates an
unknown in attempts to reconcile inequalities between evaluation
techniques.
LBL-32617
SWITCHABLE WINDOW MODELING
Abstract:
Switchable glazing, or smart glazing, has variable optical properties.
The
photochromic lenses in sunglasses that become darker as the
surroundings become lighter are one common example of switchable
glazing. The switching material incorporated into the glazing is
known as a chromogenic device. There are electrochromic,
thermochromic, and photochromic devices whose properties vary from
a high transmittance "bleached" state to a low transmittance
"colored" state. The optical properties of electrochromic devices
change with applied current, those of thermochromic devices change
with temperature, and those of photochromic devices change with
the amount of incident radiation. Ineffective control of the
amount of incoming solar radiation and visible light can render a space
practically uninhabitable. Shading systems and sun control glazings
have been developed to avoid excessive solar gain is without
excluding the daylight completely.
LBL-32815
AUTOMATIC CODE GENERATION IN SPARK: APPLICATIONS OF
COMPUTER ALGEBRA AND COMPILER-COMPILERS
Abstract:
We show how computer algebra and compiler-compilers are used for
automatic code generation in the Simulation Problem Analysis and
Research Kernel (SPARK), an object-oriented environment for
modeling complex physical systems that can be described by
differential-algebraic equations. After a brief overview of SPARK,
we describe the use of computer algebra in SPARK's symbolic
interface, which generates solution code for equations that are
entered in symbolic form. We also describe how the LEX/YACC
compiler-compiler is used to achieve important extensions to the
SPARK simulation language, including parameterized macro objects
and steady-state resetting of a dynamic simulation. The application
of these methods to solving the partial differential equations for
two-dimensional heat flow is illustrated.
LBL-33192
MODELING WINDOWS IN DOE-2.1E
Abstract:
The most
recent version of the DOE-2 building energy simulation program,
DOE-2.1E, provides for more detailed modeling of the thermal and
optical properties of windows. The window calculations account for
the temperature effects on U-value and update the incident angle
correlations for the solar heat gain properties and visible
transmittance. Initial studies show up to a 35% difference in
calculating peak solar heat gain between the detailed approach and
a constant shading-coefficient approach. The modeling approach is
adapted from LBNL's Window-4 computer program, which is used in the
National Fenestration Rating council's U-value rating procedure
#100-91. This gives DOE-2.1E the capability to assess the annual
and peak energy performance of windows consistent with the NFRC
procedure. The program has an extensive window library and algorithms
for simulating switchable glazings. The program also accounts for
the influence of framing elements on the heat transfer and solar
heat gain through the window.