Last week the U.S. National Academy of Engineering (NAE) announced a list of grand challenges for engineering in the 21st century. The goal was to identify what needs be done by the engineering community to help humanity thrive.The NAE's committee paid no heed to my recommendations, so don't look for a technologic stimulus package. Forget the Tech Check. It's not coming. That shiny new hybrid car and the solar-powered 60-inch flat panel HD TV and the iPhone for the dog will have to wait.

Instead, the committee of experts came up with 14 challenges in four categories: sustainability, health, reducing vulnerability, and joy of living. Overlooking the fact that the categories sound like seminars at a geriatric conference, the entire list itself is robust.

The challenge that caught my eye was "make solar energy economical." This idea dovetails with an excellent report in last month's Scientific American titled "A Solar Grand Plan." The editors contend that "by 2050 solar power could end U.S. dependence on foreign oil and slash greenhouse emissions." Then they go on to outline their plan:

• Massive tracts of the Southwest would have to host solar energy-capturing photovoltaic cells
• Large solar concentrator power plants would have to be built to process that energy
• A new DC power transmission delivery system would then deliver the juice

The toughest part may be the financing. Scientific American figures it will take an investment of "$420 billion in subsidies from 2011 to 2050." Can that price tag be considered affordable? If not, how can solar energy be more economical? The NAE suggests using new materials to reduce fabrication costs and finding better ways to store solar energy.

Engineering those ideas into real, working, affordable solutions will be the grandest challenge.