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  ABOUT UI SD07:   Mission, goals & history | Illinois team | Original concepts | Project details | Data | Progress in D.C., Week 1

About UI Solar Decathlon 2007 - Project details

Modular concept

The concept for the University of Illinois' Solar Decathlon house is a flexible modular system that can provide utility-independent housing for temporary or seasonal use.

In the very early stages of the design process, the devastating effects of Hurricane Katrina were weighing heavily on the minds of the organizers at Illinois. They wanted to develop a prototype for disaster relief to be used as temporary housing or as mobile office and command centers. The pictures of FEMA trailers and tent cities and the thoughts of families traveling hundreds or thousands of miles away from their homes were quite vivid.

The Illinois team developed a system based on replicated 12' x 16' living and service modules. The modular system allows for highway deployment and flexibility of floorplans, and they could be delivered to locations not accessible by larger units. In a real-world application, each module would be constructed in an assembly plant and then packaged for transfer. The modules can be transported on an individual chassis or grouped on a combined truck-trailer chassis. Every module carries its own solar collectors and space conditioning systems. Upon assembly, multiple systems can be connected on site to provide power for lighting appliances, space conditioning, cooking, laundry, toilet and shower.

The 12' x 16' modular unit allows a considerable number of self-contained living combinations to be used. The flexibility of the modules provides for an interesting and varying architecture resulting from standard elements. The solar units, of course, offer the flexibility to inhabit the space while "off the grid," or in a net-zero energy situation. As a re-inhabitation unit, the houses could be installed prior to the complete restoration of utilities. In order to be highway transportable, the roof could be low-pitched with adjustable collectors above. The elementhouse the team brought to Washington, D.C., employs a collapsible and deployable pitched roof made from the solar array, and it also serves as a shade for the south side of the house.

The Solar Decathlon competition has been used by the UI team as a catalyst for design exercises in undergraduate and graduate classes for each of the allied disciplines involved. While a central core of students and faculty has developed, constructed, transported and operates the home, undergraduate and graduate students continue to investigate alternative design solutions, especially in anticipation of the house's return to the Illinois campus, where it will eventually be used for further research.

Transportion and assembly/disassembly

One of the aspects of elementhouse in which the team takes particular pride is the deployment system, especially because it helps keep the project within the idea of building "green" as much as possible. The house was originally constructed, one module at a time, in a warehouse on the Illinois campus. Each module was built in an assembly-line manner on a steel rail-and-roller system sitting on adjustable jack stands that allows the modules to be moved with relative ease and using only human power. Transportation of the modules of elementhouse uses the same system: A module is raised via heavy-duty jacks, the rails and rollers are removed, a tractor-trailer is backed underneath and the module is lowered and secured onto the trailer. No external power systems such as cranes and forklifts are used — it's human power that puts the modules in place.

Net-zero or off-the-grid energy efficiency

A net-zero energy house is one that produces all the energy it requires over the course of a year. At any given time of the year, the energy produced by the house's systems (e.g., solar, wind, hydro, etc.) may exceed or may be less than that required by the house. Net-zero houses are still connected to the electrical grid so that energy can be added or removed from the electrical grid as needed. "Net metering" allows the electrical meter to run forward and backward, with energy purchased and sold to the grid throughout the day and year.

The Energy team at Illinois created numerous computer calculations using a solar house model that simulates a house powered by photovoltaic (PV) solar collectors that convert solar energy into electrical energy. The energy powers all systems in the house (water heater, refrigerator, air conditioner, heat pump, etc.), and various parameters are assigned by the user (e.g., location, minimum window area, number of people).

Optimization of the house design requires using the predictive analyses (written in an Excel spreadsheet), subject to the assumed parameters, to find a net-zero house design. Three "independent" variables — the insulation thickness, PV collector area, and window area — can be changed to determine a net-zero energy house condition. Minimizing (optimizing) the "lifecycle" cost of the house is the objective. There are an infinite number of combinations that yield a net-zero energy house, but a limited (possibly only one) condition that results in a minimum lifecycle cost.

Such a model was created by the University of Illinois 2007 Solar Decathlon Team and used for developing the elementhouse design, and the house was built to resulting specifications. The model has been validated with Energy Plus, a detailed simulation model used internationally by building energy professionals, and the team offers an Excel worksheet to anyone who wants to develop their own energy simulation model.

Download the Sample_EnergyModel_Illinois.xls file (Excel, 484k), follow the instructions and visit all of the tabs to see what's possible.


Is elementhouse marketable? The Illinois team thinks it is. The house was constructed at a total project cost of $500,000-600,000, but that figure includes promotional, transportation and other costs associated with the competition. At an estimated $100-120 per square foot, the building costs are similar to traditional homes and afforable for many people. The solar panels account for approximately $60,000 of the total cost, but energy rebates and annual energy savings could offset that outlay, depending on the amount of incentives available in any given area. The flexibility afforded by using self-contained modules means a family can expand their home by adding the needed modules and using modules recycled by people who downsize after using the system. And the use of bamboo in furniture and floors, reused items such as the kitchen countertop and recycled ones such as the dining tabletop — made of plastic coat hangers — demonstrate creative ways to conserve natural resources, save money and still have a beautiful, comfortable home.

Comfort and computerization

The house is designed to completely eliminate forced air climate control by going with a simple, elegant radiant and natural convection system for both heating and cooling. Radiant conditioning naturaly feels better and takes less energy than forced air, while eliminating the possibility of mold growth and allergen transport. The Illinois house also allows users to have remote access to the comfort systems through the house's computer system. All of the technology is user-friendly and easy to use. The systems include a weather station that collects data outside the house and displays it online for remote access (anytime, anywhere). Indoor temperatures and airflow are monitored by sensors that send data to the computer system, and alarm systems alert the occupants of abnormal situations. elementhouse also monitors power systems and allows a user to decide when to run items that consume power for efficient use of power.

Also take a look at the house details in the "Data" link, above.

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University of Illinois at Urbana-Champaign
Mechanical Science Engineering
1206 W. Green St., Urbana, IL 61801
© 2007 University of Illinois

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