IRVINE, CALIF. — Collegiate teams from 19 universities from around the world opened their solar-powered houses to the public in early October as the U.S. Department of Energy’s biennial Solar Decathlon kicked off at the Orange County Great Park here. This was the first time that the Solar Decathlon was held here in a terrific location at what used to be the El Toro Marine Air Station. The contest had previously been held at the National Mall in Washington, but the Great Park looks like it’s a superior location — no shortage of space and endless sunshine.
The contest was unaffected by the government shutdown, as it really was too late — the students were in Southern California assembling their houses at the time of the shutdown and the teams from Austria and the Czech Republic had shipped their houses across the Atlantic in July.
In a tight competition, Team Austria, made up of students from the Vienna University of Technology, won top honors overall by designing, building, and operating the most cost-effective, energy-efficient and attractive solar-powered house. University of Nevada Las Vegas took second place, followed by Czech Republic, comprised of students from Czech Technical University, in third place.
The Austrian house used two clever technologies, including a floor grid system that incorporates PEX tubing combined with air channels. Air flowing through the channels picked up heat or coolness from the PEX tubing and exits out slot diffusers in the floor at either side of the house. The arrangement allows both radiant heating and cooling. The Austrians also used a Swiss product from a company called Joulia SA that runs the incoming domestic water through a floor grid in the shower floor. The incoming water picks up heat from the flowing shower, preheating the water going into the water heater. Joulia claims that a family of four can save 1,000 kWh per year with its shower tray, which converts to 3,412,142 Btuh.
The team from California’s Santa Clara University employed a ceiling-mounted radiant heating and cooling system from an Italian company called Messana Air-Ray Conditioning SRL. Why the Italians? They volunteered, said Santa Clara’s spokesman Brian Grau. Offering students products for the houses goes a long way; it seemed like all of the plumbing was from Kohler, except for the Austrians and Czechs, who opted for products from Duravit and Hansgrohe.
Stanford University’s Start.Home contains a prefabricated 12-ft. x 15-ft. core module that contains all of the wet systems for the kitchen and bath, including a GE heat pump water heater. The bathroom contains a Caroma dual flush toilet and a digital shower control from Kohler. A 25-gal. graywater tank, which was not connected during the contest, would supply drip irrigation to the landscaping.
The plumbing system is a Uponor PEX combination domestic water and fire sprinkler system. As it turns out, however, the house will ultimately be permanently sited in San Mateo County in California, which does not allow PEX for fire sprinklers, so the house will have to be replumbed.
All of the houses were tightly insulated; Stanford’s uses a structural insulated panel, along with a phase change material that fastens onto the USB underneath the roof. Stanford selected 650-sq.ft. of DuPont’s Energain phase change material, which the company says will stabilized temperatures and reduce heating and cooling costs.
Phase change material was big at this year’s Decathlon. Santa Clara filled an old wine barrel with it to store solar heat. Stevens Institute of Technology placed a soy and wax phase change material in their walls. Stevens Institute of Technology, by the way, used a regenerative calcium chloride system to remove humidity, plus the system could also reverse and supply humidity in an arid climate.
The home has 6.5 kW of PV on the roof, but no solar thermal.
Heating and cooling is provided by a Mitsubishi Tri-Zone ductless split heat pump. Fresh air is provided by a Fantech heat recovery ventilator and there’s a Panasonic Whisper Fan in the bathroom.
The DesertSol house from the University of Nevada Las Vegas had the most attractive interior design seen at the competition by CONTRACTOR, an opinion evidently seconded by the judges since the house won first place in the market appeal category. Its exterior is steel and vertical wood battens made from reclaimed snow fencing. The house has both PV panels and ground-mounted evacuated tube thermal collectors that feed into a 100-gal. Buderus tank.
Radiant heating is supplied through a familiar product — the students couldn’t remember the brand name, but it was either Viega Climate Panel or Uponor Quik Trak, both of which were invented by former CONTRACTOR hydronic heating columnist Joe Fiedrich. Taco circulators move the heat transfer fluid, and the forced-air side is handled by a Mitsubishi ductless split.
Like a number of the other houses, DesertSol uses a fire-protection sprinkler system combined with a potable water plumbing system.
The next Solar Decathlon will be held in 2015. DOE has not yet announced a site, although Orange County has to be a contender.