A regular photovoltaic unit converts sunlight into electricity. Building integrated photovoltaics (BIPVs) do more. "Building integrated" means the unit is installed as a part of the building instead of as an appendage. There are multiple types and orientations of solar panels on the ICON House.
Our roof array consists of 30 polycrystalline solar panels that also serve as cladding, they are the first wall against weather elements. They are able to shed water in the summer and snow in the winter. By producing a small amount of heat when operating, snow melts on contact.
To supplement the main roof array, the east porch area is sheltered by a glass roof. These 11 glass BIPVs are monocrystalline and amorphous silicon panels, a different type of panel from the roof. These specific panels are bi-facial, meaning they use both sides to convert light into energy, so that reflected light on the underside of the porch can also be used to generate electricity.
The 2009 competition is the first Solar Decathlon in which all solar houses will be tied to the grid, as opposed to storing PV-generated electricity in batteries. What does this mean for our house?
In general, it means that we will feed electricity into the grid during the day, and draw electricity from the grid at night. The amount in and amount out are measured and balanced using net-metering, with the hope that we will produce more than we use over the course of the competition.
Our team believes that this grid-tied version of energy balance is a highly important demonstration for the public, and a much more realistic model of a solar-powered community. With a battery, one house can be self-sufficient. Tied together, a community of houses can generate enough power for themselves and then feed the excess into the grid, making it available for purchase by those who require more energy than they can produce by themselves, thereby impacting the overall community need for fossil fuels.
The ICON Solar House uses flat-plate solar thermal collectors on the south roof and walls to superheat water for latent cooling, radiant flooring, and domestic hot water needs. Upon heating the water-glycol solution in the collectors, the heat energy is transferred to one of these three tanks, depending upon temperature and need.
The desiccant system is given highest priority, because it requires the highest temperatures to provide latent cooling, or dehumidification, in the summer. This make the air feel a little bit cooler, and the electric AC unit does the rest of the job.
The second destination is the domestic hot water storage tank, where the heat energy is exchanged to heat hot water for showers, clothes washing, and other domestic uses.
The radiant flooring system is the third destination, where the heat energy from the solar thermal collectors is exchanged to heat water, which in turn circulates through tubing underneath the floor. Radiant floors deliver heat at low temperatures by utilizing the superb energy storage capacity of water compared to air, and the performance level of our radiant floor is a testament to the efficiency and flexibility of this type of system. Delivering heat at temperatures only a couple of degrees above the desired comfort zone temperature means that the radiant floor system heats the house using a fraction of the energy used by a gas furnace or electric heater. To further improve the efficiency of this system, a pump selectively draws water from the middle or top of the storage tank depending on the desired temperature of the house, which maintains stratification in the tank and improves the efficiency of the solar thermal system as a whole.