President Obama will emphasize jobs and American competitiveness on Tuesday in the State of the Union address. We'll be covering what he says, and what it could mean for technology, especially energy technology, talking to various experts on the subject. But we'd also like to hear from you. What should Obama talk about in terms of energy, climate change, and innovation?

One of the smart things the Chinese have done—for decades now—is to take waste heat from coal power plants and use it to heat homes and businesses, something that's done in the United States, but not widely. The system works by using some of the steam produced at a power plant to heat water, which is distributed in pipes through a city to radiators or floor heaters (pipes in the floor). Called cogeneration, it's a relatively easy way to get far more use out of the energy in coal or other fossil fuels.

But as it turns out, cogeneration can make it more difficult to shift from fossil fuels to renewable energy. When cities depend on heat from power plants, there's a limit to how much grid operators can lower power output from coal plants, while still providing enough heat. Especially in winter, then, power grid operators have to keep coal plants running, even when there might be sufficient wind power to shut them down, or at least turn them way down. As a result, some of the wind power can't be used.

To use more wind power, the grid operators in northeast are building "pumped hydro" systems, which use excess wind power that's generally produced at night, to pump water uphill into a reservoir. Later, when there's less wind power, the water flows downhill and spins turbines to generate power again. This way, spikes in wind power that couldn't be absorbed by the grid because of the minimum power requirements at coal plants can still be used by spreading the power generated throughout the day. But adding storage for wind power will drive up costs, a major challenge for technology that is already more expensive than coal-fired power plants.

Efforts to reduce carbon dioxide emissions in China may be backfiring--at least in the short term.

Next month the country faces a self-imposed deadline to reduce its carbon intensity (a measure of the amount of carbon dioxide emitted per unit of GDP) by 20 percent compared to 2005 levels. In a last minute dash to meet these targets, some local governments have started imposing planned blackouts.

While the blackouts are cutting emissions from power plants, they're having unintended consequences. Factories, which have to keep running to meet production requirements or face fines for missing deadlines, are getting their power instead from backup diesel generators. These emit carbon dioxide and running them has led to a diesel shortage. Thousands of fueling stations have reportedly shut down or refused to sell drivers more than half a tank of diesel fuel. To make up that gap, Chinese refineries are producing more diesel--a strain in a country that has to import most of its oil.

Of course, unintended consequences from efforts to reduce carbon dioxide emissions aren't limited to China. In the United States and Brazil, the use of food crops for biofuels can drive up food prices and lead to the destruction of forests as new land is cleared to make up for lost food production. Clearing that land also results in more carbon dioxide emissions, undoing much of the benefit of biofuels.

Ethanol made from sugar cane rather than corn (the main source of ethanol in the U.S.) results in far less carbon dioxide emissions. But Dan Sperling, director of the Institute for Transportation Studies at the University of California at Davis, estimates that when you figure in the impact of cleared rainforests, that benefit could disappear.