Coal. It’s dirty, and burning it generates massive amounts of CO2, which causes global warming. It’s also the America’s main source for power generation.

So what can be done, asks Greg Gunner Guenthner. Are there ways to make it cleaner? Carbon capture technology is a possibility, but it’s years away from being usable.

Oil is another massive polluter, and gets more expensive by the day. Looks like the only option is to invest in sustainable energy – the sooner the better.

We’re standing on the tracks and the train is coming, says Wayne Mulligan. But that’s no reason for investors to not play the market. Wayne says going long on discount retailers is the best way to profit from low consumer confidence. And with fuel prices on an unsustainable uptrend, investors should look to the alternative energy market. Meanwhile, the auto industry is facing ruin. A clear opportunity for shorting, says Wayne.

Editor’s Note: It seems energy is on the tip of everyone’s tongue again today. If it’s not the debate about where oil prices are heading next, it’s fresh concern over our long-term energy future. Byron King’s energy insider says we cannot lose anymore time in developing a plan for future power supplies. Whether its finding new oil reserves or shifting dependence to alternative sources, it will take decades to realise. Without a clear energy policy now, it will take longer. And by this time, it could be too late…

There’s a small revolution going on…You see it on TV when the commercials come on. You see it on the front page of your local newspaper. You see it everywhere. New corporations are being formed because of this revolution. And money is flooding into this sector undeterred.

Costs for solar thermal energy will be cheaper than coal as soon as 2020, according to a report from the US Department of Energy, making one solar ETF a great way to profit.

Google, Chevron and Goldman are all betting that this prediction is correct. This from Bloomberg:

Unlike photovoltaic solar panels that convert sunlight to electricity, solar thermal focuses sunrays with mirrors to heat oil in glass pipes to about 700 degrees Fahrenheit (370 degrees Celsius).

After a strong 2007 campaign, solar stocks – and the overall clean energy sector – fell hard in the first quarter of 2008. The PowerShares Wilder Hill Clean Energy Portfolio (PBW), an industry standard, plunged nearly 30%.