TRNSHD-A Program for Shading and Insolation Calculations
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Date
1996Author
Hiller, Marion D.E.
Publisher
University of Wisconsin-Madison
Metadata
Show full item recordAbstract
For analyzing systems with high solar gains it is important that design tools have a
reliable and accurate means of predicting the solar radiation on surfaces. Since solar
radiation on a surface is often greatly influenced by self-associated facade obstructions,
neighbor buildings and the surrounding landscape, a prerequisite of solar modeling is the
ability to predict shaded and unshaded parts as a function of solar position and geometry.
The objective of this thesis is to improve the shading and insolation calculations for
simulating buildings simulations with TRNSYS.
In order to select the appropriate shading and insolation algorithms for TRNSYS, a
literature search was carried out on calculation techniques and their implementation in
software applications for thermal building simulation. Based on the results of the
literature search a computer program called TRNSHD was developed. In this program,
surfaces are projected onto a plane and appear as a series of polygons. The heart of the
program is a "polygon clipper" that determines the boundary of subpolygons when two or
more polygons overlap one another. For a given geometric configuration, TRNSHD
performs shading calculations of external surfaces. In addition, TRNSHD can determine
the distribution of beam radiation that passes through a window and onto inside surfaces
of a room. The results of an analysis with TRNSHD are sunlit fractions which are defined
as the ratio of the radiation on a surface including shading effects to the radiation on the
surface without shading. The radiation source can either be beam radiation or diffuse sky
radiation. Although TRNSHD was developed for building simulations with TRNSYS, it
is a stand-alone tool that is not restricted to either buildings or TRNSYS and thus can be
used to solve other shading problems.
For validation, the results of TRNSHD were compared with other algorithms. The
major assumptions of TRNSHD and their effect on the results are discussed. The major
assumptions concern the number of "patches" for diffuse sky radiation calculations and
the frequency at which the beam radiation shading calculations are performed. The
conclusion is that a total number of 72 sky patches are needed and a frequency of 24 hours
(one average day) of each month is sufficient for an annual simulation. The comparative
validation process showed that TRNSHD functions correctly and the results of TRNSHD
are in good agreement with expected values. The external shading procedure for beam
radiation has been validated against an ASHRAE algorithm for overhang and wingwall
shading and against a proposed European standard. In addition, comparative calculations
with another software application developed by the Danish Building Research Institute
were performed. For validating the external shading procedure for diffuse radiation,
results of TRNSHD have been compared to those of TRNSYS's TYPE 34 (overhang and
wingwall shading) for different shading configurations. A comparison of TRNSHD with
experimental measurements and computer simulations from the University of Michigan-
Ann Arbor has been performed for the internal solar distribution procedure.
A complex shading study of a building with atrium has been performed by using
TRNSHD. The study gives an example of the use of the program and demonstrates its
capabilities.
Subject
Thesis (M.S.)--University of Wisconsin--Madison, 1996.
Dissertations Academic Mechanical Engineering.
University of Wisconsin--Madison. College of Engineering.
Permanent Link
http://digital.library.wisc.edu/1793/7765Description
Under the supervision of Professors William Beckman and John Mitchell; 125pp.
Citation
Hiller, M.D.E. (1996). TRNSHD-A Program for Shading and Insolation Calculations. Master's Thesis, University of Wisconsin-Madison.