Alternative energy plays have been around for decades, including Ballard Power Systems Inc. (NASDAQ/BLDP), a maker of hydrogen fuel cells that went public in 1993. The stock traded as high as $100.00 as a speculative investment opportunity in early 2000 but was unable to break into the automotive market. It is currently drifting at the $4.00 level. However, what Ballard was hoping for is now materializing for battery-powered automaker Tesla Motors, Inc. (NASDAQ/TSLA), which has built a superhighway of charging stations across the U.S. and is expanding into Europe and China. Tesla is a great story and a decent possible investment opportunity. Yet it’s not only vehicles that demand alternative sources of energy; we also see demand coming from numerous applications and, in some cases, manufacturing facilities. The demand for alternative energy can be based on wind, solar, or water and has led to the development of a strong solar industry as an investment opportunity. A small-cap that has been exciting the stock market while producing sizzling gains for speculators has been Plug Power Inc. (NASDAQ/PLUG), a developer of hydrogen fuel cells that power forklifts and other devices. The stock traded as low as $0.32 over the past 52 weeks, surging to $6.37 on Thursday morning after reporting strong results. Plug Power has been on my technical analysis screens for some time, as the stock consistently breaks higher. If interested, I would suggest investors look to this stock on weakness for a volatile speculative investment opportunity. Another possible investment opportunity that may interest investors in the alternative energy space is FuelCell Energy, Inc. (NASDAQ/FCEL), which has a market cap of $616 million. The stock has traded as low as $1.12 and as high as $4.74 over the past 52 weeks. The current price is halved at $2.37, so there’s a potential aggressive investment opportunity here. FuelCell is a developer of fuel cell solutions by way of its stationary “Direct FuelCell” power plants, built to deliver ultra-clean, efficient, and reliable green power. The process involves harnessing the energy of renewable biogas from wastewater treatment and food processing. Clients are varied and include commercial, industrial, government, and utility businesses. Sectors served include the food and beverage, manufacturing, hospital and prison, college and university, hospitality, utilities, and wastewater treatment areas. FuelCell says its energy produced is up to two times more efficient than fossil fuel plants. The company’s plants produce output ranging from 300 kilowatts (kW) to 2.8 megawatts (MW) and are expandable to more than 50 MW. There are currently more than 50 plants worldwide that have generated more than 300 million kilowatt hours (kWh) of electricity. FuelCell is expanding in Southeast Asia, including South Korea, Indonesia, Thailand, Malaysia, and Singapore, which the company sees as an investment opportunity. Revenues are estimated to rise 7.2% to $201.16 million in FY14 followed by 22.6% to an estimated $246.54 million in FY15, according to Thomson Financial. I suggest investors keep an eye on a company like FuelCell, as this volatile investment opportunity has tremendous upside if it can deliver results.