What do search engines and wind energy have in common? That's the question a lot of investors were asking earlier this month, when Google made an almost US$40 million investment into NextEra Energy Resources, a North Dakota wind energy firm. The simple answer: more than you think.

It's not surprising that the Internet search-engine superstar needs energy. Companies like Google own massive computer frameworks, known as server farms, to store all that digital data floating around in cyberspace. While Google is quite hush-hush about how many computers it owns, estimates put it at about 1,000,000 servers (almost 2% of the world total), and an enormous amount of power is needed to keep them running constantly. And as cyber-information grows - almost 24 hours of video footage is uploaded onto YouTube every minute - more and more computers are required to store and distribute it.

But where does their power come from? Most server farms are located near coal-fired generating plants. Good for efficiency, but that adds up to a pretty big carbon footprint. Naturally, this has environmental groups fuming and lobbying the corporations for clean energy alternatives. Given Google's avowed sensitivity on this issue, investing in wind turbines in North Dakota makes good public relations sense.

However, it is usually the company's philanthropic arm, Google.org, that handles such good-citizen initiatives. Thus the unprecedented move to make a first-time direct investment into NextEra Energy suggests that Google is expecting something further.

It seems logical to assume that the company's motivation also involves saving money by slashing its dependence on coal-fired generators. After all, when your electric bills approach that of a small country, it's hard not to jump on a company that could potentially produce enough power to light up 55,000 homes.

But if this is, in part, an exercise in cost-cutting, Google made a big mistake: it chose the wrong renewable energy.

Wind Farms vs. Geothermal Power

The main problem with wind farms: they don't work when it's not windy.

But that's not all. Wind energy is plagued by high capital costs, a weak power transmission system, and low output, making its success heavily dependent on government subsidies. Load factors for wind energy - that is, the difference between how much power a generator can produce and how much it actually produces, which determines how much money a utility will make - are also quite low. The large physical footprint - the amount of land required to build wind farms - is another downside, as is the threat they pose to birds and the noise pollution they generate.

Add this all up and you've got the biggest loser when it comes to going green. In reality, the best renewable energy bet Google could make, especially in the United States, is on geothermal. Leaving everything else aside, geothermal beats wind energy on the most important factor: it is not dependent on weather. That means there is no need for backup power generation facilities, something wind farms must have for the days when the turbines won't turn. Nor are government subsidies absolutely necessary for geothermal energy; they're more of an added bonus. And geothermal power plants require the least amount of land: they can hum away contentedly even in the middle of farmland or a park.

Geothermal also wins on the numbers, with the highest load factor of all renewable energies and the biggest profit margin. Take a look at the cost breakdown of renewable generating technologies in the U.S. - it's clear that geothermal is miles ahead:

Once Bitten, Twice Shy

Perhaps the reason Google decided to go with wind energy this time is because it gave geothermal a chance in the past. Two years ago, through Google.org, the company became the biggest investor in enhanced geothermal research, beating even the United States government. Unfortunately, that time around, Google picked the wrong company.

Google invested US$6.25 million into AltaRock Energy in August 2008, to help the company make a success of its promising Geysers project in northern California. AltaRock was using the latest technology - Enhanced Geothermal Systems (EGS) - in an attempt to harness some of the energy locked far beneath the earth's surface. As Google discovered, though, making a sound investment is not as simple as picking a company just because it has a great project location and the finest in tech. A host of pitfalls faces any geothermal developer - including inexperienced crews, insufficient financial backing, and the lack of a good power purchasing agreement.

But most formidable of all are the challenges of very deep drilling. While EGS represents a breakthrough, it's still new, and it's tricky to use. To properly exploit its potential, companies need to learn how to drill that deep, and to do so despite the hot corrosive fluids and unfriendly intervening layers of rock that can ruin a well in short order. And as if that weren't enough, users have to work extra cautiously. Geothermal activity is generally found around seismic fault lines, and fracturing deep rocks using hydraulic pressure has linked EGS to earthquakes.

As AltaRock Energy (and its investors) found out, it's going to take more than just fat corporate and government checks and tweaks to conventional techniques for EGS projects to work. The Geysers project came to an abrupt halt just over a year after drilling began. Barely a third of the well's planned 12,000 ft depth had been reached before drillers encountered a layer of fibrous rock that caused the holes to collapse.

Getting on the (Right) Green Bandwagon

Renewable energy is essentially still in its infancy, with plenty of barriers to surmount. At the same time, there's no mistaking politicians' growing desire to climb onto the bandwagon. Which means more and more companies are jumping at the chance to join in. But this is still relatively unexplored territory, and the market has some hard lessons yet to teach. Not every company... or idea... is cut out for this.

It would be wrong to say wind energy doesn't have a future, because it does - a very distant and windy one. One that won't be materializing anytime soon, at least not until the capital costs of wind development drop and transmission techniques improve.

Geothermal isn't easy. The Geysers failure demonstrates that. But it's proven, it's cost effective, and it runs 24/7... so for now, it's our favorite renewable energy.

Our research is focused on finding the best geothermal companies out there and, because Google is our favourite search engine, we'll be happy to share that research with CEO Eric Schmidt and his band of merry men. So come on Google, feel lucky and click here - we'll give you a free three-month trial with our Energy newsletter, including our #1 geothermal recommendation.

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