Electricity can be generated in a near limitless number of ways — from massive nuclear plants to the smallest rooftop solar system. However, each particular method comes with its own set of costs and drawbacks.

Coal-fired plants, for example, emit harmful greenhouse gas emissions. Renewable sources like wind power have engendered community opposition because of concerns about potential health and environmental concerns. And in the wake of the recent earthquake in Japan — and subsequent radiation leaks — many are wary of nuclear power.

The drawbacks associated with any method of generation — whether real or perceived — have spurred researchers to look into alternative sources of energy.

Here is a look at some not-so-familar sources of electricity that could one day be powering homes or devices.

Algae-based biofuels

(Pond Biofuels)(Pond Biofuels)

Biofuels, made from plant and animal materials such as corn, have been touted as a greener alternative to fossil fuels. One of their main advantages is that plants absorb carbon dioxide as they grow, compensating for the carbon dioxide released when they are burned. Toronto, Ont.-based Pond Biofuels has developed a process for using algae as a source of biofuel, as well as a way to capture carbon dioxide from industrial sites. The algae are grown in large tanks. Through the process of photosynthesis, they use light energy to turn the carbon dioxide generated by factories such as cement plants into biomass. The algae biomass is harvested and processed into a substance that can be used as a substitute for coal or petcoke, or processed into other biofuels such as biodiesel.

More than just a solar cell

(Fujitsu Laboratories)(Fujitsu Laboratories)

This past December, Kawasaki, Japan-based Fujitsu Laboratories announced that it had developed a new device that can harvest energy from both ambient light and heat. The device is made from low-cost plastics, and could be used to produce medical or environmental sensors that don't require batteries or wiring.

Tidal power

(Andrew Vaughan/Canadian Press)(Andrew Vaughan/Canadian Press)

Engineers have talked about harnessing the power of tides for a long time, but it wasn't until November 2009 that Nova Scotia Power and its technology partner Open Hydro deployed the first commercial in-stream tidal turbine in the Bay of Fundy.

Tidal turbine

(Joel Page/Associated Press)(Joel Page/Associated Press)

Many different kinds of tidal turbines have been tested in the past few years. This is one of the prototypes that Ocean Renewable Power Co. mounted on a barge in Eastport, Maine, for testing in 2008.

Waste-to-energy

(Plasco Energy Group)(Plasco Energy Group)

Ottawa-based Plasco Energy Group is one of several Canadian companies developing technology to turn trash into energy. Plasco's plasma gasification demonstration plant in Ottawa is shown above. It decomposes garbage in the presence of high temperatures and low oxygen to generate syngas, which is burned to generate electricity.

Flywheel technology

(Lisa Poole/Associated Press)(Lisa Poole/Associated Press)

One challenge posed by renewable energy sources such as wind power is that their peak power production may not match periods of peak demand. Beacon Power Corp. uses "flywheel" technology to provide short-term energy storage for New York's electrical distribution system. Energy is stored as rotational energy when the rotor or flywheel is accelerated and released when the flywheel is slowed down.

Storing energy

(Lisa Poole/Associated Press)(Lisa Poole/Associated Press)

At 16,000 rpm the flywheel can store and deliver 25 kilowatt hours of extractable energy. This array, in Tyngsboro, Mass., can store one megawatt. (Lisa Poole/Associated Press)