Difference between revisions of "Energy"

Humanity consumes 15 terawatts of energy^[1] and this is projected to rise to about 30 terawatts. This is a 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.

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 monetary 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 bypass the incumbent economic system to enable plentiful, environmentally-friendly power.

Much future energy generation is likely to become more decentralised. Many buildings, or group of buildings, will likely generate much of their own power on-site by incorporating solar panels into the roof, walls, pavements and even windows ^[7], as well as having other renewable energy generation devices such as wind turbines and geothermal systems.

Although for power requirements beyond that which can be captured locally for more energy intensive activities, there will be very large-scale renewable energy generation sites. For instance electricity to supply the entire United States or Europe could be met with photo-voltaic arrays measuring one hundred miles by one hundred miles [8].

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:

Generating energy

Solar

Unlike fossil fuel energy, solar technology is improving rapidly. As a result of improving technology and changing attitudes, world photovoltaic production is growing exponentially. And as production has been growing, price has been falling, with about a 20% decrease in price-per-watt for every doubling in production^[9].

This map shows the area needed to meet the world's energy needs (square on left), the EU's (middle), and Germany's (right). It is less than a third of 1% of the Sahara Desert. Desertec is multi-national program looking to develop this kind of large-scale solar facility and infrastructure.

Solar technologies can be divided into first, second and third generation. First generation solar cells use silicon wafers to convert about 12% of the light to electricity and work only in direct sunlight. As of 2008, 85% of solar panels sold were first generation^[10][11]. Second generation solar cells are similar, but the silicon wafers are much thinner, on the nanometer scale, which reduces material used, allowing lower production costs and higher manufacturing capacity. Using lenses and mirrors to concentrate the sun's light onto a smaller area, thus reducing the number of cells needed, is now commonplace. This method allows relatively expensive high-efficiency solar cells to be integrated into relatively cheap systems.
The third generation of solar cells  encompasses a range of technologies at various stages of development, including —

• Flexible polymer solar cells  that can be integrated into paint, windows etc. for ubiquitous PV. The conversion efficiency is currently low, around 3-5%, but this is improving. Current polymer solar cells degrade over the course of a few years, but future versions will hopefully overcome this limitation.
• Dye-sensitized cells . These have relatively high conversion efficiencies.
• Multi-junction solar cells, which have extremely high conversion efficiency. There are prototypes that convert as much as 43%^[12].
• Nanocrystal solar cells . Using nanoengineered crystals, it is theoretically possible to create solar panels with an efficiency of 60.3%^[13]. These are so small they could even be sprayed onto surfaces. They would also work with infrared.
• Microcontinuum are working on a solar cell that could convert infrared light with up to 80% efficiency by using arrays of gold nanoantennae. Half the energy that reaches us from the sun is in the invisible infrared range of spectrum, so finding a way to convert infrared to electricity opens up staggering amounts of energy. Infrared light is emitted by the ground at night, having been absorbed from sunlight during the day. If and when this technology comes to fruition, we could see thin, flexible coatings of solar cells that generate solar power even at night. This would enable constant solar power generation despite intermittent sunlight.
• Only a fraction of the solar energy that falls on a photovoltaic cell can be converted directly to electricity. Much of the rest turns into heat. However, this heat can also be used to generate electricity, as an alternative to, or in conjunction with, photovoltaics. Solar thermal  (such as power tower & [14]. SHPEGS is an open-source design for a solar thermal generator. solar updraft tower )
• stratospheric solar array

As the technology improves, solar power becomes cheaper and more efficient. By contrast, fossil fuels are stuck with a fixed efficiency, and become more expensive as accessible reserves are depleted.

As PV technology evolves it will allow ubiquitous photovoltaics —

Ubiquitous photovoltaics

Ubiquitous PV will be the ultimate in post-scarcity energy. This refers to easily-applied, durable and very cheap photovoltaic surface coatings, using inexpensive raw materials and manufacture processes, that could cover the majority of roofs, pavements, roads and other surfaces.

This vast distributed energy gathering area has the possibility of providing all of the energy requirements of advanced society. For example, one quantitative analysis found that covering all of England's rooftops with photovoltaic panels (at 19% efficiency) would meet energy demand. And interestingly in the US the road network has around the same area as would be required to supply the whole country with electricity - see Solar Roadways for more information. Ubiquitous PV will allow roads, rooftops and other surfaces to generate abundant energy in a way that is pre-distributed, reducing the need for an energy-distribution infrastructure.

Ultimately, solar cells could even be woven into clothing, allowing mobile power for phones, personal computers etc. The range of electric vehicles could be improved by integrating photovoltaics into the paint and windows and charging their batteries while not in use.

Conveniently, ubiquitous photovoltaics would mean that the greater the population concentration in an area, the greater the energy-generating surface would be.

Polymer solar cells , nanocrystals , or nanoantennae  are potential enabling technologies.

Another potential enabling path to ubiquitous photovoltaics is self-assembling biophotovoltaics. This approach could allow anyone to extract and stabilize proteins from any plant matter, for example lawn clippings or fallen leaves. Researchers at MIT have succeeded in not only generating solar energy by this method, but making the process easy enough that anyone could do it simply by adding a small bag of stabilizing chemicals to organic waste and soaking a piece of glass or metal in the resulting mixture. Because neither technical skills nor expensive raw materials are needed, this method could allow ubiquitous photovoltaics. The conversion efficiency of existing models is only 0.1%, but researchers are confident they can get it up to 1 or 2%, which would make it useful^[15].

Solar thermal

Solar thermal technology involves concentrating the Sun's light is converted to mechanical energy to drive a turbine. It may be concentrated to boil water to power a steam engine.

Solar thermal power systems have two key advantages:

• They create a lot of power. Where photovoltaic systems struggle to convert more than 15% of sunlight into electricity, solar thermal systems using steam engines can achieve solar-to-electric conversion efficiencies of over 40%
• They require no rare materials, such as gold or indium, which are needed for some photovoltaic chemistries. A system of mirrors, lenses and iron mechanical parts is potentially much cheaper and easier to build than photovoltaics. It is also possible to digitally manufacture many such parts. This technology could easily be open-sourced, and their are several groups such as SHPEGS and SolarFire working on this already.

Solar thermal systems may well prove preferable to photovoltaic in static, land-based generation. However, unlike photovoltaics, they require a 'footprint' of land and cannot be integrated into existing buildings, vehicles, roads etc.

Space-based solar

This picture shows the Earth and the Sun in their true proportions. Considering that the Sun is a fusion reactor 1,300,000 times the size of our planet, we ought to be able to get most of our energy from it...

Solar satellites could easily meet all mankind's energy needs for the foreseeable future. While wind, ocean, bacterial and other means of generating clean energy can make a contribution, space-based solar power (along with ubiquitous photovoltaics and nuclear fusion) have the potential to provide nearly all of the 30 terawatts we will need in the future. A solar array in space measuring 15km by 15km and converting and transmitting power at just 10% efficiency would produce nearly 30TW.

There are two obstacles that have held back space-based solar power so far. First, we would need to develop a more efficient means of access to space. It is too expensive to launch something as large as a solar satellite into space using modern rocket technology. Automated material processing and construction in lunar orbit would allow construction at the required scale. Second is the issue of transmitting energy wirelessly back to Earth. This can in theory be done with microwave beams directed at a receiver on Earth, but the technology is still in the prototype phase, see Microwave transmission 

Wind

Some people have expressed concern that generating significant amounts of wind energy would require massive swathes of land to be turned into wind farms. But this is not the case for several reasons:
Firstly, wind power lends itself easily to decentralization: turbines can be put on top of any building, taking up no 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. Also, much useful wind power is offshore, where land use is obviously not an issue, and the turbines can be far from view.

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.

Another is kite power. Kites can be flown much higher than turbines on towers, allowing them to access the faster winds that blow at higher altitudes. This is very advantageous, as the power in the wind is proportional to the cube of its speed: a kite flown at 800m would capture winds twice as fast as those available to a turbine, but these winds contain 8 times the energy. One study suggests kite generators will cost half as much to build as turbines. See also this TED talk and the company KiteGen.

Ocean

New slow water current energy technology allows us to turn the turbulence in little eddies and ripples of water into electricity. Ideal for small-scale generation from rivers and streams.

• Wave energy - The waves bobbing up and down endlessly are a source of practically unlimited energy. It is estimated that there are between 0.9 and 9.1 terawatts of wave energy available worldwide^[16]. 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^[17].

• Tidal energy - only 30,000 gigawatts available worldwide^[18]. Brings significant environmental issues by damming over a river

• Ocean currents - 80,000 gigawatts^[19]

• Ocean thermal energy conversion  - about 1.15 terawatts are available^[20], so it will never be a major part of the pie. It is, however, ideal for seasteading.

• Salinity gradient - Where the fresh water at river estuaries pushes into the salty water of the sea, it creates pressure that can be harnessed to generate energy. The first power plant using this method was opened in Norway in 2009^[21] . 220,000 megawatts are available ^[22] but, like tidal power, it could interfere with the river's ecology

Hydro-electric

Hydroelectric power  has been used for decades as a renewable source of energy. This is ultimately powered by the sun evaporating water from the oceans and depositing rains on mountains and hills, which is captured in reservoirs and fed through turbines. It is also currently used as an energy storage system by pumping water back up to the reservoir when there is surplus electricity being generated, however this is not very efficient and caused by inflexibility and slow response in current national power networks.

Some mountainous countries such as Norway have almost their entire electricity supply met by hydroelectric generation.

One downside of hydroelectric power can be that large areas of countryside become flooded behind the dam during the building of a new hydroelectric generation project, altering the local ecosystem.

Nuclear power

Nuclear fission  (currently employed). Nuclear reprocessing  by the Fast breeder reactor  reduces the amount of waste, increases efficiency.
Prospective: nuclear fusion , accelerator-driven thorium-fuelled energy amplifier , and Travelling wave reactor . 3rd and 4th generation nuclear reactors are very safe.

Question of waste disposal. 1GW of nuclear generates only a modest 20 tons of waste. So if all our energy came from nuclear fission, we'd have 300,000 tons of waste (very dense, occupying a relatively small volume). However, this waste is dangerous.

Decommissioned warheads can be used as fuel.

Geothermal

• shallow geothermal heat pumps . Small-scale thermal (not electric) geothermal heat pumps are a great way to heat houses year-round in cold places.
• 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 [23].
• Prospective: pump CO₂ instead of water as the fluid to carry heat [24]

Biomass (carbon-neutral)

biofuel (algae), compost methane, fermented crop waste, algae, sustainable wood, and clean burning of: organic waste, animal dung and rubbish

Could be integrated with carbon capturing technologies to become better than carbon-neutral

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 microbial fuel cell one cubic meter in size has been made to produce 2.5kW, though this is not easily replicable. Microbial fuel cell expert Bruce Logan has said that he expects systems will produce 1-1.5kW/m³ and cost about $3000 ^[25].

A $40 system developed by Dr. Peter Girguis and Dr. Helen White has shown itself capable of producing 96W of power^[26]. This system used inexpensive charcoal electrodes and can run for years and years without maintenance. They write that "we could potentially access 9 tW of power annually via microbial processes alone. "^[27]

Derek Lovley and his team have developed a new strain of geobacter bacteria has been developed that has a power output eight times greater than previously known strains^[28]. This is not factored in to the figures given above. Using biotechnology, it may be possible to produce even more productive microbes.

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. By building microbial fuel cells into water treatment facilities, we can make water treatment plants self-sustaining in terms of energy. This would be a big step towards abundant water.

Like geothermal power, microbial fuel cells could find useful application in places lacking significant sunshine, wave or wind power.

• 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. Some examples —

• Stirling engines like this one convert heat to mechanical energy. They are more efficient than steam engines and more appropriate for small-scale power generation.
• 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 ^[29].
• 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 ^[30] 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.

Storing energy

Compressed air

For solving the intermittency problem with wind and solar, compressed air has several advantages over batteries or other technologies:

• It is about 50% cheaper than batteries
• Unlike batteries, it requires no rare elements and no chemicals that could leach out into the soil.
• Unlike batteries, it does not run down over time. Air compressors have few or no moving parts, so they can run for ages.

Mechanical energy from wind turbines or concentrating solar powered steam engines could be used directly to compress air, without generating electricity. This air is later used to spin a turbine to generate electricity on demand. This increases efficiency, as the energy is only converted once.

• See this report on a renewable energy grid for the US using compressed air.
• http://www.u.arizona.edu/~sreynold/caes.pdf

Batteries

Capacitors

Nanoengineering is enabling more and more efficient capacitors

Hydrogen

Hydrogen economy

Using energy

As our technology advances, it is becoming more and more energy-efficient. According to Wikipedia's article on efficient energy use , "up to 75% of the electricity used in the U.S. today could be saved with efficiency measures that cost less than the electricity itself". When considering the energy needs of a post-scarcity world, it is important to recognize that most of the things people want to do - heat a building, wash clothes, light their homes - can be achieved with a fraction of the energy we currently use.

• Transport is currently one of the biggest demands on energy supply, taking up 27.8% of all the energy we use^[31]. The transport article looks at how we can transport people and goods using almost no energy.
• Good architecture and insulation can reduce energy needed to heat and cool buildings to zero in nearly all climates. This is discussed here.

Post-scarcity of energy will arise when we have both halves of the equation: abundant production of energy, and non-wasteful use of it.