The UD Solar Team incorporated many features into the house in order to make it more energy efficient than typical residences. The efficiency of the house starts with the design and the orientation. Images of the UD Solar House

Delaware's geographical latitude dictates that our photovoltaic panels must be inclided at least 20 degrees to the horizontal to maximize exposure to the sun. The house itself is orientated southward so that the slope of the roof maximizes photovoltaic collection.

Since the house is oriented south, many other factors were taken into consideration. The eastern faces of the house have large windows in order to allow the early morning sun into the house. The sun should begin to heat the large thermal mass in the floor. The western faces have small windows so as to cut down on the unwanted thermal gain created by the setting sun. The south and north faces have few windows, since the windows' lower insulation value (as compared to a solid wall) create heating and cooling loads, while providing little benefit. The southern/northern windows exist merely for passive ventilation and aesthetic purposes. The large vertical windows on the east and west break the semi-circular front from the boxy back. They also provide indirect sunlight and ventilation, when needed.

Above the large sets of window on the front facets, there are blinds. These blinds are designed such that they block the higher declination and unwanted harsh summer sun from infusing the house with thermal radiation, while allowing the lower declination and much needed winter sun to heat the house passively. They are also designed to allow heat through so that there is no thermal buildup near the windows.

The semi-circular shape of the house, while not tied to energy efficiency, is linked to the livability and aesthetics of the house. The unique shape allows us to fit many photovoltaic panels on the roof. More importantly, however, is the fact that the shape lends itself to the flow of the living areas. The bedroom is barely separated from the living room, which is itself located near the kitchen. This design allows the occupants to easliy move without restriction between the many parts of the house and between the many different aspects of their lives that are contained within the house. The bedroom was placed on the west side with the small windows to increase privacy. The bathroom was placed near the bedroom to allow quick access at night. The office/living area was placed on the east side so that the occupants could enjoy the maximum amount of sunlight possible while they are awake. The mechanical room is situated behind the living area in order to cut down on the noise heard by occupants trying to rest and in order to shorten the distance from the power generation systems and the main loading, like the TV and computer. The kitchen area was designed to be near the living area so that the two blend into each other.

The thermal mass discussed earlier is merely the large mass of the floor itself. The purpose of the thermal mass is to maintain a constant temperature. For example, on a cold winter day, the sun would heat the floor through the windows. During the night as the temperature drops, the floor would aid in maintaining a constant inside temperature, since it would release the heat that it built up during the day. Also, the physically more massive the substance, the longer it takes that substance (in this case the floor) to change temperature between extremes.

The southern entrance to the house is a rudimentary airlock. The double door system is used because of its ability to protect the interior from the conditions of the exterior. The space between the doors is semi-conditioned space, so that it forms a buffer between the conditioned inside and the harsh environment. The system severly cuts down on the ability of wind and any precipitation it is carrying to shear through from the outside straight to the inside. The system also allows any unconditioned air from the outside to mix with conditioned air from the interior and reach equilibrium, all without compromising the integrity of the conditioned living area.

Key technologies incorporated into the UD solar home include:

AstroPower PV system: The PV power system is based on an AstroPower SunUPS 40 system with expanded batteries. The PV Array consists of 40 Astropower AP 120 panels, wired into 10 strings of four panels, providing approximately 4.8 KW of power, at a system voltage of 48 volts. For storage, an array of 20 Concorde SunXtender PVX 2580 L batteries can provide approximately 3 days of reserve power for the house.

Ecothermal wall/roof panels: The walls and the roof are made of pre-fabricated panels using rigid planks of solid expanded polystyrene (EPS), reinforced with tubular galvanized steel struts and angled steel top and bottom corners. The wall is 7.5 inches thick and roof 11.5 inches thick, with rated R values of 30 and 50, respectively. This probably represents the lowest cost per R-value available on today's market.

Hardcore composite floor: The floor is made of an 8" sandwiched composite material by Hardcore Composites. These composite panels are typically used for bridge and marine structural applications and are extremely strong and durable. The strength comes from fiber-reinforced polymer network and can be varied by the density of fiberglass bottles. The network is filled with solid polyurethane foam. The average R value for the floor is about 17. Although this material is not recommended for typical building applications due to its high cost, the advantage is the compact integration of strength and insulation.

Traco windows: All windows are made by Traco; they are titanium coated, heat mirror inserted, and krypton filled windows with rated center of glass R value of 8.3 and a total window R value of 5.3. This level of insulation is two to three times the average window insulation for a typical home.

Exterior Rhino finishing: Exterior finishing is made of Rhino-coated plywood panels. Rhino is a polyether based, solvent free, flexible, elastomeric coating which can be applied to almost any surface. Its typical applications are for surface protection for pick-ups, trailers, vans, and open-air off-roaders. This method allows for easy transport and quick assembly.

Geothermal heat pump: A FHP GP010 geothermal heat pump from BSS is used to cool the house in the summer and to provide supplemental heating in the winter. For the competition a 400 gallon tank is used to simulate a geothermal reservoir.

ThermalMax tubes: A ThermoMax evacuated tube system is used to generate hot water for DHW, as well as to supply warm water for the radiant floor system.

Warmboard radiant floor heating: A radiant floor system is used for winter heating, using Warmboard floor panels and IPEX tubings. The system acquires thermal energy from the Thermomax solar thermal collector described above.

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