One of the biggest highlights from the 2007 Solar Decathlon comes from reigning victor University of Colorado- and the design is proving once again that the team has what it takes to be solar design champions. Committed to defending their 2002 and 2005 titles, the 2007 CU Solar Decathlon team has brought a versatile, modular design that integrates “shining” examples of solar technology, recycled shipping containers, and a super cool aesthetic.
Putting a twist on the competition criteria, CU has designed a 2,100-ft2 house with a central 700-ft2 core. The smaller version meets the Solar Decathlon guidelines and functions as a complete house on its own. However, the team decided to design “a full-size house to make our story more relevant to homeowners as well as the building industry”, said Michael Brandemuehl, an associate professor in CU’s Department of Civil, Environmental, and Architectural Engineering.
At the National Mall solar village, the team has built the smaller version of it’s CORE concept and delineated the full house outline with decking. The larger version uses two conventional shipping containers to take advantage of modular, prefabricated materials. The competition module houses the kitchen, bathroom and a centralized area for mechanicals. The additional module will be constructed after the Solar Decathlon adding space for laundry, a master bathroom and a guest bathroom. The complete concept will become a research, education and outreach facility for Xcel Energy, the team’s primary sponsor.
CU’s design uses a building integrated photovoltaic thermal (BIPV/T) collection system, a building integrated photovoltaic (BIPV) system and a battery bank. The thermal system collects heat from the backside of the PV array and transfers the thermal energy to storage tanks for a water-to-water heat pump. The PV system was sized to meet electricity needs in Washington, D.C., and Colorado with a battery bank that allows for four days backup during zero PV power.
High Efficiency Water to Water Heat Pump
The EnergyPlus building energy simulation program was used to size an efficient water-to-water heat pump with two thermal storage tanks. More energy-efficient than air-to-air or air-to-water systems, the chosen system also allows use of refrigerant R410A which has zero ozone depleting potential.
Inside, the CU team’s CORE solar house uses environmentally friendly Marmoleum® flooring, formaldehyde-free Plyboo Strand® 100% bamboo cabinetry, Richlite recycled paper countertops and Ecogress mosaics made from eco-friendly porcelain. Several walls and doors are eco-resins from 3Form Material Solutions with 40% post-industrial reclaimed material. The decking is made from reclaimed redwood planks sourced from Boulder-based building material recycler ReSource2000.
Designed to reduce energy loads, the entry from CU minimizes system needs with a well-insulated building envelope, high performance windows, natural daylighting, natural ventilation, energy-efficient appliances and an efficient HVAC system. Even without the BIPV systems or the specified HVAC, the team estimates that the design would use 40% less energy than a conventionally built home of the same size.
Insulation, passive solar design and windows create a 73% savings in heating and a house that requires 60% less electricity throughout the year. As a grid-connected home in sunny Boulder, Colorado, the design would produce 38% more energy than it needs to operate. Even under cloudier skies in Washington, D.C., the home is still a net-zero structure that would produce an energy surplus.