The 2002 house was built for entry in the very first U.S. Department of Energy Solar Decathlon in Washington D.C. The 2002 competition team consisted of a joint venture between students of Missouri S&T and Rolla Technical Institute. Engineering students from S&T designed the home while students from RTI contributed hands-on expertise in much of the construction. The goal of the team during the design process was to create a home that the average consumer would find comfortable and familiar. This impression of comfort was embodied in the traditional ranch home that would easily fit into the average American neighborhood.
The home consists of one bathroom, one bedroom and the common area which has a kitchen, desk, and living room, all in under 800 square feet as required by the competition. The U.S. Department of Energy Solar Decathlon 2002 takes place in Washington D.C., meaning that the house must be designed to be transported. This home was built in three sections that could be easily transported on tractor trailers, and a hinged roof that was designed to meet road safety height requirements.
The interior of the home features a traditional look to match the exterior. The cabinets and light fixtures are common to what can be found in most houses. However, some unique features give this home its edge. The dishwasher was disguised to match the surrounding cabinets and convey a sleeker look. The bedroom is cut off from the living room with a movable wall in the shape of a bookshelf. The wall can be closed for privacy or opened up to create one large room.
Passive Solar Design
Time-tested design techniques introduced thousands of years ago were utilized to cut energy costs. These passive solar design methods include the orientation and the shape of the home as well as the position of windows. The house is elongated along the East to West axis with most of the windows positioned on the south side. This allows enough daylight in to replace electric lighting until nightfall. It also contributes to passive heating and cooling. The roof overhangs along the south side of the home are specifically designed to block nwanted light, and therefore, heat, during the summer when the sun is higher in the sky. These same overhangs allow that heat and light to enter the home during the winter when the sun is lower.
The south facing sunroom is a major passive heating element of the house. The room is covered with ceramic tiles which act as a thermal mass. Since the overhangs are designed to only allow light to enter the house during the cooler months, in the winter the tile collects heat from the direct sunlight during the day, and slowly releases that heat at night when the surrounding temperature begins to drop. The sun-room also acts as a thermal buffer zone, controlling the temperature changes between the main living area and the outside, much like a vestibule that is found in most commercial buildings.
An active use of the sun can be found on the roof. The angle of the roof is designed to optimize the generation of electricity and the absorption of heat for domestic hot water use. Powering the entire home is a photovoltaic array of 32 solar panels that generate over 5 kW of electricity. Because the local utility allows the house to be “net-metered”, when the house is producing more electricity then it is using, the meter actually turns backwards and the occupant is paid by the utility company.
Also seen on the roof is an array of evacuated tubes. The tubes contain a vacuum in order to more efficiently absorb the energy from the sun and convert it to heat. The heat gained by the tubes is then transferred to a hot water tank via a heat exchanger and a closed-loop liquid system to be used as a domestic hot water supply.
In this competition, S&T placed first in the Refrigeration contest. The team chose to use a DC refrigerator, rather than the typical AC type used in most homes. In most photovoltaic systems, the solar panels are connected to an inverter, that converts the direct current, generated by the solar panels, to the alternating current used for most items. The refrigerator bypassed this conversion, and the inefficiencies associated with it, and made the entire refrigeration system more efficient.