Growth investing hinges on companies that are positioned to take advantage of potentially huge markets. And it's easy for anyone to see that renewable energy is just that: a potentially huge market.

I've been noticing more and more interest in solar energy, and it does seem like a tantalizing prospect. After all, the sun is a constant and reliable energy resource that, for the most part, gets squandered. And when it comes to harnessing solar power and its transformation into an important energy resource, there are plenty of signs that its time has finally come.

What's your sun sign?
There have been plenty of indications that solar is becoming a more popular option for burgeoning electricity needs. Microsoft (NASDAQ:MSFT) has set up a solar power system for its research facility. Google (NASDAQ:GOOG) has the same idea with its recent move to make its headquarters solar-powered (if not its data centers). Walgreen (NYSE:WAG) has installed solar systems in 100 of its stores.

Government interest in (and subsidies for) solar power can't be discounted at the moment, either -- and some would remind us that with the Democrats' majority in Congress, solar initiatives will likely become even more common. A high-profile case in point is California, which recently approved a $3.2 billion solar energy initiative that will span 11 years.

Meanwhile, solar energy is of interest overseas as well. Think of the opportunities afoot as huge countries are expressing interest in harnessing the power of the sun to generate cheap power. Indeed, China recently said it wants to build the world's largest solar-power plant.

Banking on sunshine
There are plenty of companies -- not to mention venture capitalists -- trying to capitalize off the market opportunity inherent in sustainable energy solutions. Some big, impressive numbers are floating around out there about renewable energy and particularly solar power. I have seen conjectures that put the renewable-energy market at $167 billion by 2015. Meanwhile, CleanEdge expects the solar energy market to grow from $11 billion today to $54 billion in 2015.

There are many ways companies seek to capitalize off solar's likely explosive trend in clean energy generation. Some of the companies are already well- established ones. For example, Cypress Semiconductor (NYSE:CY) is in the game through its subsidiary SunPower (NASDAQ:SPWR). Semiconductor maker Applied Materials (NASDAQ:AMAT) is also adding the manufacturing of solar wafers. BP may be an oil giant, but it's also breaking ground in solar power.

But what about the companies that aren't household names yet, that many investors don't know about? The exciting potential for solar energy is a large part of the reason why David Gardner recommended SuntechPower (NYSE:STP) in June's issue of Motley Fool Rule Breakers. It's a solar-energy pure play that makes photovoltaic (PV) cells, the backbone of solar-power-generating systems.

Foolish bottom line
If you're interested in learning more about Suntech Power, or you want to search for or discuss high-growth investments in many different promising industries, take a 30-day free trial to Motley Fool Rule Breakers. You'll immediately have access to all of the stock picks offered up by David Gardner and his team of analysts, as well as the great insight and research this vibrant community digs up and discusses on an everyday basis.

When it comes to solar power, the future seems bright. Don't forget your shades.

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Alyce Lomax does not own shares of any of the companies mentioned. Microsoft is a Motley Fool Inside Value pick. The Fool has a disclosure policy.