The U.S. Department of Energy Solar Decathlon 2015 returns to the Orange County Great Park October 8-11 and October 15-18 from 11 a.m.-7 p.m. Free event; $10 parking.

The Solar Decathlon challenges collegiate students from across the country and around the world to design, build and operate solar-powered houses that are cost-effective, energy-efficient and attractive.

Info: solardecathlon.gov.