In Part I and II, we discussed how solar simulations in Energy3D can be used to decide where to erect a new building in a city block surrounded by existing buildings. Now, what about putting multiple buildings in the block? The optimization problem becomes more complex because students will have to deal with more variables while searching for an optimal solution.
Suppose students have to decide the locations of two new constructions A and B such as the ones shown in the first image of this blog post. The horizontal solar radiation heat map shows that the southeast part is a cold area that should be avoided. Now they have six options to layout the new constructions. Namely, they can either place A or place B in the northwest, northeast, and southwest parts. The second image in this blog post shows the results calculated from the solar simulations. Placing the buildings in the northeast and northwest parts (row 1 in the image) seems to be the optimal solution and we can either put A or B in each of the areas and vice versa -- the sum of the solar energy they will receive doesn't seem to change much. This is not surprising because this layout creates large south-facing areas that will get a lot of solar energy in the winter.
What is a little surprising to me is that the last set of layout, i.e. the layout of A (or B) in southwest and B (or A) in northeast (row 3 in the image) produces less solar heating than the layout of A (or B) in southwest and B (or A) in northwest (row 2 in the image). This is counter-intuitive because in the latter configuration the south-facing area seems to be less. Without the solar simulator to give me the exact numbers, I would have predicted the wrong thing using the simple-minded south-facing rule.
The sun is lower in the winter and higher in the summer. How does the sun path affect the solar radiation on the city block in our urban design challenge? Is solar heating different in different seasons? Let's find out using Energy3D's solar simulator. Energy3D has a nice feature that allows us to look at the 3D view exactly from the top. This kind of reduces the 3D problem to a 2D one once you complete your 3D construction and want to do some solar analysis. The 2D view is clearer and the drag-and-drop of buildings is easier.
First, we added a rectangular building to the city block and moved it to four different places -- northwest, northeast, southeast, and southwest -- in the city block and set the month to be January and the location to be Boston, MA (which is our hometown). Not surprisingly, the solar radiation on the building is the lowest at the southeast location, almost half of the radiation heating the building receives at the southwest and northeast locations and about 40% of the highest radiation heating at the northwest location. This is because to the southeast of the block, there are three tall buildings that shadow the southeast part of the block.
Next we set the month to be July and repeated the calculation.This time, the solar heating on the building does not seem to change much from one location to another. This is because the sun is high in July and the shadow of a building is short. This result means that we probably should only consider solar heating in the winter when we design our city block.
Now, what about the orientation of the building? Let's rotate the building 90 degrees and redo the solar analysis in January. The results show that the southeast location remains the coldest spot, but the difference between northeast and northwest are much less. This is because the building has a larger south-facing side in this orientation than in the previous one.
In sustainable architecture, passive solar design refers to searching for optimal strategies to maximize solar heating on a building in the winter and minimize solar heating in the summer in order to reduce heating and cooling costs of the building. A passive solar design challenge is a typical optimization problem that requires many important steps of engineering design to solve, such as analyzing data, considering constraints, and making trade-offs.
For urban design, site layout has a big impact on passive solar heating in buildings as neighboring tall buildings can block low winter sun. Energy3D’s heliodon tool can compute, visualize, and analyze solar radiation in obstructed situations commonly encountered in dense urban areas.
The solar urban design project we have developed challenges students to use Energy3D to construct a square city block surrounded by a number of existing buildings of different heights, with the goals to maximize solar access for new constructions and minimize obstruction of sunlight to existing buildings. The existing buildings, which cannot be modified by students, serve as constraints for the design challenge. This design challenge is an authentic engineering problem as it requires students to consider solar radiation as it varies over a day as well as over seasons and apply these math and science concepts to solve open-ended problems using a supporting heliodon simulation tool. This distinguishes it from common computer drafting activities in which students draw structures whose functions cannot or will not be verified or tested.
Energy3D can generate solar radiation heat maps on the walls of buildings and the ground (see the first two images in this blog post). These heat maps show the cumulative heat of solar radiation on a surface over a certain period (a day or a month). They are calculated by summing up the solar energy projected onto each unit area of the surface while the sun moves cyclically in its path at the given location. The total solar heating result, summing from all the unit areas of all the walls, is shown on top of each building. This number will go up and down as students move or reshape the building. This calculated result is more accurate than shadow and shading, which only reflects instantaneous solar heating at a particular moment.
The horizontal radiation heat map can be used to identify the hot and cold areas of the empty city block. With this heat map, students can find out where the new constructions should be in order to have maximal solar heating in the winter. Once they put in a new building, they can move the building around within the construction site to experiment how much solar energy the building will gain. As an example, the third image shows that a rectangular high-rise building will receive the highest amount of solar radiation in January if it is placed at the northwestern part of the square and it will receive the lowest amount of solar radiation if it is placed at the southeastern part.
Such an analytic tool provides data for students to make their design decisions.
We are adding some new features to our Energy3D software that will allow the user to carry out passive solar design of one or multiple buildings (or even an entire city block). These new features will calculate the distribution of solar energy density over an area such as the vertical surface of a wall of a building or the horizontal surface area of open space. The results will be visualized as color heat maps overlaid to the surface. The information in these color maps can be used to help students make decisions when they are searching for optimal passive solar designs.
These new analytic tools will be used in our Passive Solar Urban Design Challenge that requires students to design a city block with new buildings that have maximal solar heating in the winter and minimal solar heating in the summer, without severely obstructing solar access of existing buildings in the neighborhood.
These new features are integral parts of the existing heliodon simulator in Energy3D, which allows the user to adjust the sun path. The video in this blog post demonstrates this.
We are proud to release Energy3D version 2.0, available for download from our website. Energy3D is a computer-aided design and fabrication tool for making small model green buildings. This version added new energy assessment features that allow students to evaluate the energy performances of their designs and investigate the effect of passive solar heating. Currently however, this energy assessment tool is limited to only 12 selected cities around the world.
The next release will feature powerful passive solar heating simulation that can be applied to a wide variety of settings ranging from a single family house to a dense urban area.
Energy3D runs on both Windows and Mac OS X. Java 7 is required. It may also run on Linux (some of our users actually got it to run on Linux), but it has not been thoroughly tested on Linux.
In a pilot study conducted in December 2012, high school students in an engineering class used our Energy3D CAD tool to do an urban solar design project -- they must consider the sun path in four seasons and the existing buildings in the neighborhood as the design constraints to optimize solar penetration to the new buildings and minimize obstruction of sunlight to the existing buildings.
Energy3D can log any student actions and intermediate steps, which provide extremely detailed information about student design processes. With such a high-resolution lens, we could characterize student patterns and analyze how they solve the design challenge closely. For example, the CAD log allows us to reconstruct the entire design process of each student and show it in an unprecedentedly fine-grained timeline graph. A timeline graph may show how students went through different iterative steps while shaping their designs. For instance, did they consider the interactions among the buildings they designed? Did they go back to revise a previously erected building that may be affected by a newly added one? The timeline data we have collected show that the students' designs demonstrated more iterative features as they moved on to explore and design alternatives following the initial attempts (perhaps encouraged by the gained familiarity with and confidence in the CAD tool).
A design timeline (click to enlarge)
Our analyses also suggest that there appears to be a significant gender difference in both design products and processes. The main differences are: 1) The boys tended to push the limit of the software and produced unconventional designs that looked "cool" but did not necessarily meet the design specifications; and 2) The girls spent more time carefully revising their designs than building new structures. While these findings may not be surprising to some seasoned educators, the significance is that this may be the first time this kind of gender difference was revealed or confirmed by empirical data from CAD logs. Using CAD logs may provide a fairer basis of assessing student performance based on the entire learning process rather than just looking at their final products or self reports.
Summary of the results
The implication of this study is that if we can identify patterns in student design learning and understand their cognitive meanings, we could devise a software system that can provide real-time feedback to help students learn in the future. For example, could the software prompt students to consider the design criteria more when it detects that students are ignoring them? Could the software stimulate students to think out of the box more when it detects that students are underexploring the design space?
We were in a school these two weeks doing a project that aims to understand how students learn engineering design. This has been a difficult research topic as engineering design is an extremely complicated cognitive process that involves the application of science and mathematics -- another two sets of complicated subjects themselves.
Two types of problems are commonly encountered in the classroom. The first type is related to using a "cookbook" approach that confines students to step-by-step procedures to complete a "design" project. I added double quotes because this kind of project often leads to identical or similar products from students, violating the first principle of design that mandates alternatives and varieties. However, if we make the design project completely open-ended, we will run into the second type of problem: The arbitrariness and caprice in student designs often make it difficult for teachers and researchers to assess student thinking and learning reliably. As much as we want students to be creative and open-minded, we also want to ensure that they learn what is intended and we must provide an objective way to evaluate their learning outcomes.
To tackle these issues, we are taking a computer science-based approach. Computer-aided design (CAD) tools offer an opportunity for us to move the entire process of engineering design to the computer (this is what CAD tools are designed for in the first place for industry folks). What we need to do in our research is to add a few more things to support data mining.
A sample design of the city block.
This blog post reports a timeline tool that we have developed to measure student activity levels while engaged in using a CAD tool (our Energy3D CAD software in this case) to solve a design challenge. This timeline tool is basically a logger that records the number of the learner's design actions at a given frequency (say, 2-4 times a minute) during a design session. These design actions are defined to be the "atomic" actions stored in the Undo Manager of the CAD tool we are using. The timeline approximately describes the user's frequency of construction actions with the CAD tool. As the human-computer interaction is ultimately driven by the brain, this kind of timeline data could be regarded as a reflection of the user's "brain wave."
There are four things that characterize such a timeline graph:
A sample timeline graph.
The height of a spike measures the action intensity at that moment, i.e., how many actions the user has taken since the last recording;
The density of spikes measures the continuity and persistence of actions over a time period;
A gap indicates an off-task time window: A short idling window may be an effect of instruction or discussion;
The trend of height and density may be related to loss of interest or improvement of proficiency in the CAD tool: If the intensity (the combination of height and density of spikes) drops consistently over time, the student's interest may be fading away; if the intensity increases consistently over time, the student might be improving on using the design tool to explore design options.
Timeline graphs from six students.
Of course, this kind of timeline data is not perfect. It certainly has many limitations in measuring learning. We are still in the process of analyzing these timeline data and juxtaposing them with other artifacts we have gathered from the students to provide a more comprehensive picture of design learning. But the timeline analysis represents a rudimentary step towards a more rigorous methodology for performance assessment of engineering design.
The above six "brain wave" graphs were collected from six students in a 90-minute class period. Hopefully, these data will lead to a way to identify novice designers' behaviors and patterns when they are solving a design challenge.
Looking for free tools to teach engineering design in K-12 classrooms? We are pleased to announce that Energy3D Version 1.0 is now available for free download at http://energy.concord.org/energy3d. Energy3D is a computer-aided design and fabrication tool for designing and making model buildings. With it, your students can easily conceptualize a dream house on the computer, print and assemble a real model, and take it home to show to their parents!
Energy3D works just like Google's SketchUp: You can create a 3D structure by drag-and-drop -- no number crunching is required. But unlike SketchUp, it is tailor-made for building design, evaluation, and fabrication to support engineering design learning in K-12 schools. One of its great features is the "print-out" functionality, which allows students to print out the houses they designed using a regular printer and then cut out the 2D pieces for 3D assembly (see the second image in this blog post). You can imagine how Energy3D may work for your students by looking at the houses designed by a class of high school students in the third image of this blog post. The tool is very easy to use and works well even for young kids. So if you are teaching in an elementary school, give it a try and tell us how it can be improved for younger students.
The development of Energy3D has been funded by the National Science Foundation under the Engineering Energy Efficiency Project. Dr. Saeid Nourian, a computer scientist with a Ph. D. from the University of Ottawa, has been the primary developer since joining the project in 2010. The software is based on the open-source scene graph game engine, Ardor3D, which requires Java to be installed.
Energy3D is our signature software program for designing and making buildings. It actually can be used to sketch up a street or a village. The three images in this post show this capacity.
With the built-in heliodon, students can study if a new construction will cast a large shadow on a neighboring building and affect its daylighting (be nice to your neighbors :-)). Students can also take a virtual walk of the street they design to feel about it. The villages can be uploaded to the web and shared with others.
They can even "print out" the entire street to assemble it. The example shown in this post has 68 pieces to assemble, probably not too much for a class of 20 students. Collaborating on designing and building a village may offer some great opportunities of learning to everyone.
In just a few hours, two students were capable of designing ten houses using our Energy3D software, about which they had no prior experience at all. Among them there is one with a floor plan of the shape of a heart and another the shape of a sea star.
We were excited about the ease of use of Energy3D for designing complex houses. However, there are a few concerns. First, these two houses have complicated shapes that take a long time to scale up on cardstock and assemble from the cutout pieces. With a powerful CAD tool like this, students' creativity can be unleashed--they are capable of coming up with sophisticated designs. But computer models are not the final destinations. They are thinking and visualization tools that help students conceptualize their designs. Our goal in engineering projects is to have them make real systems after computer models. If a computer model is too complex, students may not be able to make the real system within a given amount of time in the classroom. On the other hand, if a computer model is inflexible and few variations are feasible, students will quickly be bored. It may be a bad idea to limit the design capacity to simple models with only a handful of features and options. So where is the balance point?
Another thing we should watch out is that students who are too focused on designing the fancy shapes like these may pay less attention to the science and engineering principles we hope to teach in this engineering design challenge--we want them to think about designs that can achieve maximum livability and be energy-efficient. What kind of intelligence can we build into our CAD tool to provide just-in-time instructions that guide their designs?
In Part I and II, we discussed how solar simulations in Energy3D can be used to decide where to erect a new building in a city block surrounded by existing buildings. Now, what about putting multiple buildings in the block? The optimization problem becomes more complex because students will have to deal with more variables while searching for an optimal solution.
