By signing up to the Harvard University Clean Energy Project, you can contribute your computer's idle time to assist vital renewable energy research.
The Clean Energy Project uses computational chemistry and the willingness of people to help look for the best molecules possible for organic photovoltaics to provide inexpensive solar cells, polymers for the membranes used in fuel cells for electricity generation, and how best to assemble the molecules to make those devices. By helping Harvard University search combinatorially among thousands of potential systems, you can contribute to this effort.
When idle, your computer will request data on the project from the project's server. It will then perform computations on this data, send the results back to the server, and ask the server for a new piece of work. Each computation that your computer performs provides scientists with critical information that accelerates the pace of research!
The Clean Energy Project is one of the projects you can assist with on the World Community Grid.