When finished, it'll be the largest rooftop solar installation in the United States.

But it's not where you'd expect it to be.

Amid a slew of recent announcements about large solar thermal installations (a form of concentrating solar power) in the nation's deserts and well-known sunny spots, this project comes as sort of a surprise.

It's going to be built in Summit, NJ—not the first place that comes to mind when you think about solar power.

And it's being built by PPL Corp. (NYSE: PPL), which is not the first company you think of when it comes to alternative energy investments. After all, they're based in Allentown, PA.

So the meaning of this new installation is twofold.

Alternative Energy is Everywhere

We're no longer dealing with a niche market.

According to the recent UN report "Global Trends in Sustainable Energy Development," global investment in renewable energy climbed to $100 billion for the first time last year.

And more than 30% of that total came from mergers and acquisitions headed by large banks like Goldman and Morgan Stanley.

So no matter your stance on the issues driving this high level of investment, you have to agree on one thing: this is pretty big business.

Of course, we'll still need oil. We'll still need gas. I'm not denying any of that. We'll need that stuff for decades.

But the green stuff is here. It's viable. And it's making a lot of investors a lot of money.

Back to the solar installation...

It's going be built on eight roofs throughout the business campus of pharmaceutical company Schering-Plough (NYSE: SGP) in Summit, NJ.

The 1.7 megawatt system will help Schering meet its corporate goal of reducing emissions 5% by 2012 by preventing 1.3 million pounds of carbon dioxide from entering the atmosphere every year.

And that reiterates the first meaning of this story: alternative energy is everywhere.

Even on the roofs of pharmaceutical companies in New Jersey.

That leads directly into the second takeaway from this announcement.

Alternative Energy Investments Aren't Just a Pure Play

Despite what you hear everyday from the national financial media outlets, there are more ways to play this sector than just First Solar (NYSE: FSLR)—though that certainly has been, and will continue to be, a success story.

So if you're not ready to go diving into a pure play solar stock just yet, don't fret. There are plenty of other ways to gain exposure to this booming market.

For starters, you could dabble in a clean energy ETF. These have been well-chronicled in these pages and in the pages of Green Chip Review.

In some instances, these ETFs offer a mix of clean energy and sustainable companies and aren't susceptible to swings that can effect an entire sub-sector, like solar or wind.

To take an even further step away from solely renewable companies, you could also invest in holding companies or in the numerous utilities that have become early adopters of clean technologies.

A case in point is PPL, which I discussed in these pages six months ago to the day. In the two months after that mention, the stock climbed 14%.

It has since fallen, along with the broader economy, but now is looking like a good time to get back in.

In addition to developing, building and operating renewable energy facilities since 2002, PPL plans on investing no less than $100 million in renewable energy projects over the next five years.

And yet, renewables only make up a portion of the nearly 12,000 MW under PPL's control. They also employ coal, nuclear, hydro, natural gas and oil.

So the company isn't a pure play by a long shot.

But they know what's coming. And they have a plan.

That's more than can be said about some of the the larger utilities operating here in The States.

Plus, they offer a dividend, as most utilities do. For every share of PPL common stock owned, the shareholder is entitled to a $0.335 quarterly dividend. What's more, the PPL dividend has seen a 74% rise in the last five years.

Expect the dividend—and the share price—to continue to grow as PPL sees increased revenue and profits not only from increased energy demand and prices, but from good return on their alternative energy investments as well.

Other Backdoor Alternative Energy Investments

A few other savvy utilities, like Portland General Electric (NYSE: POR) and Xcel Energy Inc. (NYSE: XEL), are making good steps as well.

Incidentally, Portland just raised its quarterly dividend to $0.245 per share. It's available to shareholders of record on or before June 25.

Of course, I know more than a few ways to profit directly from alternative energy and cleantech companies as well. And they're being exploited every day in the Alternative Energy Speculator.

Our last play—a water-related company—is up over 10% in eight trading days.

Call it like you see it,

Nick