Energy
The human race currently requires 15 terawatts of energy[1]. This is a laughably tiny amount of energy compared to what is available around us: 72 terawatts of available wind energy at ground level[2], 150 terawatts in the jet streams[3], 44.2 terawatts of geothermal energy [4], 2 terawatts of easily-exploitable wave power[5] and 174,000 terawatts of solar energy[6]. We clearly have tens of thousands of times the energy we need, the key is our ability to harness this energy. This article explores existing and emerging technologies for doing this.
The energy available from solar and geothermal alone far exceed our current and likely future energy requirements and could sustain humanity indefinitely. The amount of energy that falls on the earth from the sun in a minute is what humans currently use in a year across all nations and industries.
Steadily increasing energy efficiency 
due to improved system design and increasing cultural awareness should become a significant factor in our energy usage.
The issue currently is commercial economics. The bottom line is that with the current economic framework it is still 'cheaper' to pump oil out of the ground and burn it to produce power than use other more plentiful, renewable and environmentally benign sources. These alternative energy sources are sitting right in front of us waiting to be harnessed. It may be that open-source methods can by-pass the incumbent economic system to enable plentiful, environmentally-friendly power.
A word on decentralization: some scenarios imagine our renewable electricity in the future coming from giant solar farms, wind farms and other renewable sources. However, for such farms to meet our needs, they have to cover an area the size of the USA ref. This is simply not feasible and would require bulldozing large areas of wilderness. However, solar, wind and geothermal energy can be very effective at a small scale. Each building, or group of buildings, can generate its own electricity on-site by putting solar panels on the roof, third-generation photovoltaics embedded in windows [7], a wind turbine or small geothermal generators. It is likely that our electricity in the future will mostly come from such decentralized sources, supplemented by the occasional larger energy-farm, such as a wave power generator next to a coastal city.
We have these major sources of energy available to us, in no particular order and not including fossil fuels that we currently rely on for the majority of our energy today:
Contents
Solar
Because the amount of energy falling on the Earth from the Sun is ridiculously abundant, it is likely that solar power will form the bulk of our energy in the near future, with the other sources mentioned here supplementing it. Ray Kurzweil has said [8], "If we could convert .03% of the sunlight that falls on the Earth into energy we could meet all of our projected needs for 2030" and he has predicted that solar power will meet all our needs by 2026 [9]
If most buildings covered their roofs with solar panels, using currently available technology, we could meet nearly all of our energy requirements without the need for supplementary forms of energy or centralized energy farms. It is also possible to create solar cells that are integrated into ordinary-looking windows (see Ubiquitous PV)
However, solar technology is becoming cheaper, more efficient and more accessible. Modern off-the-shelf solar panels convert about 15% or 20% of the light to electricity, but there are prototypes that convert as much as 43%. When these become mainstream, solar power will be a very attractive option. Using nanotechnology, it is theoretically possible to create solar panels with an efficiency of 60.3%[10]
[1] photovoltaics , solar thermal (such as power tower & [11], ocean thermal energy conversion , SHPEGS and solar updraft tower ). Prospective: Space solar power including solar power satellite , ubiquitous PV and stratospheric solar array
- Dye-sensitized cells
- Thin-layer photovoltaics
- Ubiquitous PV
- Nanocrystals
Wind
Wind power lends itself easily to decentralization: turbines can be put on top of any building, taking up zero extra space. By putting the turbines on a tall pole, they reach the faster winds available higher up. Large-scale wind farms also take up very little space, as the diameter of the pole is the only bit that takes up land; the business-end of the machinery is up out of the way and the land in between wind turbines can be used for agriculture or any other purpose.
One technology we may see in the near-future is flying wind turbines that exploit the reliable, high-speed winds of the stratospheric jet-streams.
Ocean
wave, tidal, ocean currents
The waves bobbing up and down endlessly are a source of practically infinite energy. While engineers have looked for a way to harness this energy to make electricity for decades, the first commercially viable wave farm was opened in 2008[12].
Hydro-electric
Nuclear power
fission Nuclear fission fission http://www.adciv.org/upload/thumb/4/4d/Wikipedia_logo.jpg/11px-Wikipedia_logo.jpg (currently employed). Prospective: nuclear fusion , accelerator-driven thorium-fuelled energy amplifier , and Travelling wave reactor
Geothermal
shallow geothermal heat pumps , volcanic related geothermal and deep geothermal - Enhanced geothermal systems (EGS). See also Future of Geothermal Power (in the US) published by MIT and Google's funding of enhanced geothermal [13]. Small-scale thermal (not electric) geothermal heat pumps are a great way to heat houses year-round in cold places.
Biomass (carbon-neutral)
biofuel (algae), compost methane, fermented crop waste, algae, sustainable wood, and clean burning of: organic waste, animal dung and rubbish
Bacteria
Certain species of bacteria (such as geobacter) deposit electrons onto electrodes placed in their environment. Much work is still being done on optimizing the systems, but microbial fuel cells already provide a cheap and very resilient form of energy. A $40 system developed by Dr. Peter Girguis and Dr. Helen White has shown itself capable of producing 96W of power[14]. This system used inexpensive charcoal electrodes and can run for years and years without maintenance. Since then, a new strain of geobacter bacteria has been developed that has a power output eight times greater than previously known strains[15].
Microbial fuel cells can be synergized with composting toilets to create a system that disposes of human waste, fertilizes plants for food and also generates electricity.
- Bruce Logan research on Microbial fuel cells including advocacy on installing microbial fuel cells at wastewater treatment plants and a page on how to make your own
- microbialfuelcell.org
Recapturing waste energy
Just like there are untapped reserves of money in the back of your couch, there are untapped reserves of energy in the ambient surroundings. Though not normally discussed by renewable energy afficionados, the random wasted energy that is floating around us as motion and heat can be considered a form of clean, renewable energy. Devices to capture this energy can be fitted to anything from a car to a computer.
Trochoidal gear engine technology can be attached to machines such as factory robots to recapture the heat they generate and turn it back into useful energy [16].
Piezoelectric crystals are crystals that generate electricity when shaken or squeezed. They have been used to recapture kinetic energy from the air flowing around a car [17] and in the suspension systems of cars.
Kinetic generators such as the nPower PEG generate electricity whenever they are moved. Even just keeping one in your pocket while walking provides clean energy. What if devices like this were routinely fitted to our vehicles?
Regenerative braking is now a standard feature in electric cars. Whenever you use the brakes of your car, you are taking away its kinetic energy. This is normally wasted, but with regenerative braking, is recaptured and used later. This can provide 10% of the car's energy needs.
