In this age of rising greenhouse gas emissions, everyone is looking for ways to scale up clean energy and cut back on fossil fuels. That typically involves the usual approaches: solar, wind, nuclear power, and hydropower.
But what if there are other technologies out there that could take a bite out of fossil fuels? There almost certainly will not be one silver bullet, but in the future there could potentially be a much broader portfolio of clean tech than just solar and wind.
Here are five technologies that may be a few years away (in some cases, many years away), but hold some promise of one day providing a significant source of pollution-free energy.
1. Tidal and wave power. Although somewhat different technologies, tidal and wave power capture energy from the movement of the ocean. Tidal power generates energy from the tides moving in and out, and is a little further along in development. Wave power generates energy from the rise and fall of waves and is still in the experimental phase. A company called Ocean Power Technologies planned to build a wave power pilot project off the Oregon coast – and received federal and state grants to do so – but abandoned the project after costs became too high. But tidal power in particular offers a lot of promise since there is no shortage of coastline on which to build. A third potential marine technology uses thermal energy; Lockheed Martin is pioneering what it calls Ocean Thermal Energy Conversion (OTEC), which uses the temperature differences between surface water and deep water to drive a steam cycle.
2. High altitude wind. Similar to the land-based and offshore versions, high-altitude wind energy harnesses power from wind, but as the name suggests, from very high altitudes. Turbines are tethered to the ground via cables and fly hundreds of feet in the air where winds are much stronger and more consistent. There are more than 20 companies developing prototypes but none have yet produced a commercially viable technology.
3. Solar roads. The possibility of a future in which roads are paved with solar panels created some buzz this spring when a couple in Idaho launched a crowd funding campaign to make that happen. The project also received lots of publicity when a YouTube video – "solar freakin roadways" – went viral and has been viewed almost 17 million times. Scott and Julie Bradshaw invented hexagonal solar panels durable enough to withstand vehicle traffic and the elements. They insist that if all 28,000 miles of U.S. roadways are covered in these solar cells, it would generate three times more power than the entire country uses. They won several contracts from the Federal Highway Administration to build a prototype solar parking lot, which is the first of its kind. They are confident it is a stepping stone to a much bigger market for solar roadways.
4. Space solar. Solar is making major inroads in the electric power sector, but the one downside is that it doesn't generate power constantly – the sun has an annoying tendency of not shining in the same spot all the time. Some scientists hope to get around that problem by building solar panels in space. Space-based solar power would generate power from the sun 24/7, and then beam the energy down to anywhere on earth using lasers or microwaves. A receiver can turn the energy into useful power. Although the technology sounds great in theory, costs would be steep and it remains a long way off.
5. Sewage waste. Cities everywhere have to deal with human waste on an enormous scale. Treating water and disposing of waste costs a lot of money, but what if that waste could be turned into useful electricity? The idea is that human waste is taken to a treatment plant where it is heated and pressurized. Then microorganisms known as methanogens go to work on the waste, and methane is produced as a byproduct. The methane can be captured and burned as electricity. The District of Columbia is going to try it out. If it works. D.C.'s water treatment agency will use the electricity to power its own operations.