Energy

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 area 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 [1], 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:

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 ^[2], "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 ^[3]

Decentralized solar cells using currently available technology could provide us with nearly all of the energy we need. However, the technology is likely to become cheaper, more efficient and more accessible over the next decade. Modern off-the-shelf solar panels convert about 15% or 20% of the light to electricity; there are prototypes that convert as much as 43%. When these become mainstream, solar power will be a very attractive option.

[1]  photovoltaics , solar thermal  (such as power tower & [4], 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

land-based wind turbine, off-shore wind turbine. Prospective: jet-stream sky windmills , maglev

Ocean

wave, tidal, ocean currents

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 [5]

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[6]. 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[7].

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