Science Energy 10 Surprisingly Easy Sources of Alternative Energy By Bryan Nelson Writer SUNY Oswego University of Houston Bryan Nelson is a science writer and award-winning documentary filmmaker with over a decade of experience covering technology, astronomy, medicine, and more. our editorial process Twitter Twitter Bryan Nelson Updated November 29, 2019 Carpathian Prince / Shutterstock Share Twitter Pinterest Email Energy Renewable Energy Fossil Fuels Sure, you've heard of wind and solar power, biofuels, hydroelectric, tidal, and wave power, but Mother Nature provides an endless bounty of alternative energy sources beyond those that we use today. Clean, green energy is all around us in the natural world, and scientists have only begun to answer the question of how to tap it. Here's a list of 10 practical sources of alternative energy you've probably never heard of. 1 of 10 Saltwater Power Photo: Tomasz Baranowski/Flickr [CC by 2.0] It has been called saltwater power, osmotic power or blue energy, and it is one of the most promising new sources of renewable power not yet fully tapped. Just as it takes huge amounts of energy to desalinate water, energy is generated when the reverse happens and saltwater is added to freshwater. Through a process called reverse electrodialysis, blue energy powerplants could capture this energy as it is released naturally in estuaries around the world. 2 of 10 Helioculture Photo: DM/Flickr [CC by ND-2.0] This revolutionary process called helioculture was pioneered by Joule Biotechnologies and generates hydrocarbon-based fuel by combining brackish water, nutrients, photosynthetic organisms, carbon dioxide and sunlight. Unlike oils made from algae, helioculture produces fuel directly — in the form of ethanol or hydrocarbons — that does not need to be refined. The method essentially utilizes the natural process of photosynthesis to produce a ready-to-use fuel. 3 of 10 Piezoelectricity Photo: Bignai/Shutterstock As the world's human population approaches a whopping 7 billion, tapping into the kinetic energy of human movement could become a source of real power. Piezoelectricity is the ability of some materials to generate an electric field in response to applied mechanical stress. By placing tiles made of piezoelectric material along busy walking paths or even in the soles of our shoes, electricity could be generated with every step we take — making people into walking power plants. 4 of 10 Ocean Thermal Energy Conversion (OTEC) Photo: Glenn Beltz/Flickr [CC by 2.0] Ocean thermal energy conversion, or OTEC for short, is a hydro energy conversion system that uses the tempurature difference between deep and shallow waters to power a heat engine. This energy could be tapped by building platforms or barges out at sea, taking advantage of thermal layers found between the ocean depths. 5 of 10 Human sewage Photo: PJjaruwan/Shutterstock Poo power? Even human sewage can be used to create electricity or fuel. Plans are already underway to power public buses in Oslo, Norway, with human sewage. Electricity can also be generated from sewage using microbial fuel cells, which utilize a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature. Of course, sewage can also be put to use as a fertilizer. 6 of 10 Hot rock power Photo: I am a Stranger/Shutterstock Hot rock power is a new type of geothermal power that works by pumping cold saltwater down to rock which has been heated by conduction from the Earth’s mantle and by the decay of radioactive elements in the crust. As that water heats up, the energy created can be converted into electricity by a steam turbine. The advantages of hot rock power are that the output can be easily controlled and it can provide energy 24/7. 7 of 10 Evaporative energy Photo: Dave Nakayama/Flickr [CC by 2.0] Inspired by plants, scientists have invented a synthetic, micro-fabricated "leaf" that can scavenge electrical power from evaporating water. Air bubbles can be pumped into the "leaves", generating electricity generated by the difference in electrical properties between water and air. This research could open the door to more grandiose ways to trap the power created from evaporation. 8 of 10 Vortex-induced vibrations Photo: Omar Jamil This form of renewable energy, which draws power from slow water currents, was inspired by the movement of fish. The energy can be captured as water flows past a network of rods. Eddies, or swirls, form in an alternating pattern, pushing and pulling an object up or down or side to side to create mechanical energy. It works in the same way that fish curve their bodies to glide between the vortices shed by the bodies of the fish in front of them, essentially riding in each other's wake. 9 of 10 Mining the moon Photo: Chris Isherwood/Flickr [CC by SA-2.0] Helium-3 is a light, nonradioactive isotope that has immense potential to generate relatively clean energy through nuclear fusion. The only catch: it is rare on Earth but abundant on the moon. Many projects are underway to mine the moon for this resource. For instance, the Russian space company RKK Energiya announced that it considers lunar helium-3 a potential economic resource to be mined by 2020. 10 of 10 Space-based solar power Photo: NASA/Wikimedia Commons [CC by 1.0] Since the sun's energy is unaffected in space by the 24-hour cycle of night and day, weather, seasons, or the filtering effect of Earth's atmospheric gases, proposals are underway to put solar panels in orbit and beam the energy down for use on Earth. The technological breakthrough here involves wireless power transmission, which could be performed using microwave beams.