Those of you who read the Tools of the Trade

column on energy Web sites earlier this month are no doubt aware that there are lots of ways to play this sector.

For example, maybe you think a summer's worth of brownouts in California and elsewhere will force corporate IT managers to find ways to keep their computers running. If so, take a look at

C&D Technologies

(CHP)

or

American Power Conversion

(APCC)

. Both companies supply back-up power systems to offices. APC's been creeping up all during May to a recent price of $16.42, which is well below its 52-week high of $49. CDT's also been rising steadily, but its recent price of $30.44 was also well off its high of $62.

Piping Hot

An active energy stock trader named

Maryke

wrote to say she likes stocks of so-called "oil country tubulars." These are the companies that make the pipes that actually extract oil or natural gas from drill sites. Her favorite company is

Maverick Tube

(MVK)

. Her rationale: "On average, a 5,000-foot well needs 50 tons of tubular steel, but a 10,000-foot well needs 600 tons of it," she says. As everyone knows, drillers must continually dig deeper as worldwide supplies diminish.

FYI: You'll find lots of reportage on Maverick and its competitors in these

past

TSC

articles. Also, to learn about tubular steel and find a list of Maverick's competitors, check out the

white paper produced by the

Steel Tube Institute of North America, or go to the group's Web site.

Maryke does a lot of her research at the Web site for

Simmons & Co. International. Simmons, an investment bank specializing in the energy sector, makes its research reports available to the public. Another useful site is

Oil & Gas Journal Online

. Maryke also regularly reads the energy pages of the

Houston Chronicle

, available online.

Alternative Energy Now

Maybe big oil stocks aren't your cup of tea. You've been watching the changing political winds in Washington, and you believe a Democratically controlled

Senate

will push for alternative fuels and renewable energy. That, of course, could benefit a company like

AstroPower

(APWR)

, which makes solar power generating products. AstroPower also has crept up steadily this spring, before retrenching some during the middle of this week.

Companies making fuel cells might benefit even more from any renewed push for renewable energy. Used in

NASA

spacecraft since the '60s, fuel cells currently have applications in everything from autos to small electric plants, which would supply power to say, a home or small office. Instead of noxious fumes, fuel cells vent plain old water as exhaust.

By way of review, fuel cells do their work by mixing hydrogen with oxygen from the air to produce an electric current. Lots of variations in fuel cell technology exist. Some run on

natural gas. So-called molten carbonate fuel cells, used for large-scale power generation, do their work at north of 1,000 degrees Fahrenheit. So instead of venting water as exhaust, they produce steam, which can be channeled to produce additional electricity. Proton exchange fuel cells use a powdery layer of platinum to spark a reaction between hydrogen and oxygen. Someday they may become commonplace in cars that use

methanol as a hydrogen source.

Visit the Web site

HowStuffWorks for a simple primer on competing technologies or the

Online Fuel-Cell Information Center (if you're so inclined, the

National Hydrogen Association, the

National Fuel Cell Research Center and

Virginia Wesleyan College all contain links to more in-depth information. Also check out

Yahoo!'s

list of

fuel cell sites, because it includes the names of manufacturers and suppliers.

And when you're ready, the

Hydrogen Energy Center maintains a list of publicly-traded companies involved either with hydrogen production or fuel cells. Keep in mind that some of these companies have yet to turn a profit, and the stocks' volatility will likely attract daytraders.

For that reason, some investors prefer

United Technologies

, which is developing the technology through its subsidiary

International Fuel Cells.

Hard Hydrogen

Finally, one hot area within the fuel cell arena right now is hydrogen storage. Maintained as a gas, hydrogen is highly flammable (remember the

Hindenburg

?). An alternative technology that keeps the hydrogen in a frozen state is too expensive for most applications. That's why the emphasis has changed from developing fuel cells that run on pure hydrogen to creating devices that extract hydrogen from more readily available substances like methanol, natural gas or even gasoline.

But the Holy Grail is solid storage. Hydrogen can be stored in the form of a metal alloy. A privately held New Jersey company called

Ergenics has developed a battery that uses this technology. And according to the company's Web site, plans are in the works to market the battery for use in hybrid fuel vehicles late this year. Meanwhile, the

U.S. Department of Energy's National Renewable Energy Laboratory is working on ways to safely store hydrogen inside microscopic carbon tubes. If its plans succeed, gas stations as we know them might someday disappear. Instead, we'd refuel our cars by replacing large carbon blocks every few weeks or months.

More Monitors

A day trader I'll call

Jeff from Houston

read my

April 25 column, "Building Your Own Multiple-Monitor Trading Station" and took issue with the idea that you should shell out as much as $900 for a graphics card that supports four monitors. The alternative is to buy four cards for each of four monitors, or eight cards for eight monitors. Fact is, you need one input jack connected to a card for each monitor you run. Cards supporting just one monitor start at about $40. So if you planned to run eight monitors you'd spend $40 times 8, or $320 -- a substantial savings. But you'll need a lot of expansion slots on your PC, and you may also need to do a fair amount of tweaking to make all the cards work in tandem.

Mark Ingebretsen has written for a wide variety of business and financial publications. Currently he holds no positions in the stocks of companies mentioned in this column. While Ingebretsen cannot provide investment advice or recommendations, he welcomes your feedback and invites you to send it to

mingebretsen@yahoo.com.