Last Friday, I sent an update to the savvy investors of the Alternative Energy Speculator making the case that, despite a temporary financial slowdown, energy demand is still forecast to significantly rise in the short-, medium-, and long-term.

Here's an excerpt from that update:

It's true the International Energy Agency (IEA) has cut it's short-term forecast by 240,000 barrels per day (bpd) for 2008 and by 440,000 bpd for 2009, but those numbers are a drop in the bucket. However, there are some nuances that need discussed.

First of all, even with the cut in the IEA's short-term forecast, the overall prediction for 2008 and 2009 is still an increase in demand. Of course, that means we still need an increase in supply if we're to keep the wheels turning and the lights burning.

The IEA still expects global oil demand to total 86.5 million barrels per day this year and 87.2 million barrels per day next year, which is still higher than the 85 million bpd or so we used in 2006.

So demand is still on the rise. And demand is still on pace to reach 113 million bpd in 2030.

My conclusion in that update was that oil production will likely never reach 113 million bpd, and that renewable energy would have to make up the difference. This is a fundamental principal of my investment philosophy... one that can't be shaken by this temporary financial mess.

What's more, our energy needs (and energy supply shortfalls) aren't limited just to oil. According to an electricity demand study by the Energy Information Administration (EIA), electricity demand is expected to increase 29% in the next 22 years, "from 3,659 billion kilowatt- hours in 2006 to 4,705 billion in 2030, at an average rate of 1.1 percent per year. "

To make up for this surging demand for both oil and electricity, the use of renewable energy is going to be significantly ramped up.

By now you're all familiar with the technologies that are going to bridge the gap to a new energy economy. We discuss them in these pages all the time: solar energy, wind energy, geothermal energy, energy efficiency, biofuels, tidal, etc.

But in order for these renewable sources of energy to make any meaningful curb in rising demand, they have to be able to successfully introduce their energy to the grid. This obstacle has incited a new industry, which I'll dub green infrastructure stocks.

These are the companies hitting the ground running, providing installation and maintenance services for wind and solar farms, and also engineering complex transmission initiatives to deliver all the green electricity to the grid.

Green Infrastructure Stocks

In the same report referenced above, the EIA also concluded that the share of renewable energy generation will climb to 6.8% in 2030, up from 2.4% in 2006. That's an increase of 183%

Perhaps more interesting, the use of wind power in the U.S. will climb an astounding 377% in that same time.

For that to happen, billions of dollars not only need to be invested in renewable energy technologies like wind and solar, but that same amount will need to be spent on new infrastructure projects.

Consider this, a 2005 study by the American Society for Civil Engineers concluded with a report card for all the U.S.'s infrastructure systems.

The grade for the national power grid was a D, and that was after earning a D+ in the 2000 version of the study.

According to the American Society of Civil Engineers:

The U.S. power transmission system is in urgent need of modernization. Growth in electricity demand and investment in new power plants has not been matched by investment in new transmission facilities. Maintenance expenditures have decreased 1% per year since 1992. Existing transmission facilities were not designed for the current level of demand, resulting in an increased number of `bottlenecks' which increase costs to consumers and elevate the risk of blackouts.

Their conclusion: The estimated 5-year monetary need for infrastructure improvements is $1.6 trillion—and that doesn't include monies needed for security.

With that kind of spending on the way, only a fool would opt not to include some infrastructure plays in their portfolio.

And with all the recent selling, some infrastructure and energy service stalwarts are trading relatively low, making now and excellent to pick up some shares.

Before I get into the companies, it's important to note that these are not pure green plays. These companies service many energy sectors, but their involvement in renewable energy will prove crucial.

Here's a list of green infrastructure companies with revenues greater than $5 billion that I currently find worthy of investment:

• Foster Wheeler Ltd. (NASDAQ: FWLT)

• The Shaw Group Inc. (NYSE: SGR)

• Jacobs Engineering Group (NYSE: JEC)

• Integrys Energy Group (NYSE: TEG)

• American Electric Power (NYSE: AEP)

• FPL Group (NYSE: FPL)

An Early Infrastructure Stock Success Story

I would've included NRG Energy (NYSE: NRG) in that list of infrastructure stocks ready to purchase.

But the U.S.'s largest utility, Exelon Corp. (NYSE: EXC) beat me to the punch.

In a litany of recent market events in which large firms and wealthy investors are trying to load up on energy assetts (Warren Buffett recently purchased Constellation Energy), Chicago-based Exelon has made an unsolicited bid of $6.2 billion to buy NRG.

Fun fact: Buffett also invested in NRG earlier this year.

But I digress...

The $6.2 billion offer is a 37% premium to NRG's closing price last week. So naturally the shares went soaring earlier this week, and savvy investors likely cashed out.

I expect this to be the infrastructure investment climate at least for the next few quarters.

This massive sell-off has left the share prices of many top infrastructure plays completely battered down.

Smart investors (like Exelon and Buffett) realize this and are acting fast to cash in.

You should be too.

According to an analyst at Atlantic Equities, Exelon is able to purchase NRG for the same price as building new energy plants and infrastructure.

This should highlight to you the oversold nature of many of these stocks.

In addition to the handful of stocks mentioned above, I've recommended my top green infrastructure play to the informed readers of the Alternative Energy Speculator.

We've already taken 5%, as I recommended it just as this activity in the sector started to heat up.

But there is much more upside to come.

Whether this company continues to operate on it's own or is bought up by an even bigger company, the returns are going to be hefty.

The company is already constructing and managing wind farms, and is manufacturing wind-related components.

You don't want to miss this next evolution of the green energy markets. Get all the information you need to profit from the Alternative Energy Speculator.

Call it like you see it,

Nick