This week the Department of Energy announced that the 2015 Solar Decathlon will again be sited at the Orange County Great Park in Irvine, California (link). It will run October 8-18, 2015. Traditionally, the Decathlon was held in Washington, DC, but moved to Irvine for the 2013 contest.
This is a significant and disappointing decision because it confirms that the contest is about solar electricity, not solar heating. In Irvine in October, the average temperature is 64˚F, practically room temperature! (In Washington, DC in October, the average temperature is cooler, though still mild at 59˚F.)
I'm a big supporter of solar electricity, to be sure, but passive solar heating ought to be central to the challenge and to the definition of a 'solar house' and a 'net-zero' house. Most of the places in the US are not like Irvine in October; they have significant heating demands that can be reduced through passive solar design. To design an 800-square foot house in Irvine that will use net-zero energy for a week in October is frankly not very difficult.
Why not hold the contest in Minneapolis a month later? Perhaps because passive solar heating implies the need for thermal mass, which is contradictory to the need for the houses to be lightweight and transportable. This is the fundamental paradox of the Solar Decathlon.
As I wrote in The Solar House, the Solar Decathlon has always been oriented to the promotion of PV systems, and it has always endured criticism for failing to reward passive strategies. But with the decision to return to Irvine, the organizers have raised the stakes by going all-in for solar electricity.
What remains curious is why so many top universities want to participate in such a naked promotional effort, and why students are willing to have their labor exploited for the PV industry.* That industry doesn't really need the publicity at this point, and I don't see PV companies turning around and endowing architecture programs. Kudos to schools like Virginia, Kansas, and Auburn, for investing their capital in more worthwhile house-building projects.
And if the Department of Energy wishes to promote PV to homebuyers in a more realistic setting, why not support the National Solar Tour?
*Then again, I must admit this is an enduring historical theme. See Your Solar House (1947) and Living With the Sun (1955), where architects did much the same for the glass industry and the Association for Applied Solar Energy (AFASE), respectively.
(Note: Weather data is TMY3 data from Orange County Airport and Reagan National Airport.)