AY Honors/Renewable Energy/Answer Key

Template:Environmental technology Renewable energy (sources) or RES capture their energy from existing flows of energy, from on-going natural processes, such as sunshine, wind, flowing water, biological processes, and geothermal heat flows. The most common definition is that renewable energy is from an energy resource that is replaced rapidly by a natural process such as power generated from the sun or from the wind.

Most renewable forms of energy, other than geothermal and tidal power, ultimately come from the Sun. Some forms are stored solar energy such as rainfall and wind power which are considered short-term solar-energy storage, whereas the energy in biomass is accumulated over a period of months, as in straw, or through many years as in wood. Capturing renewable energy by plants, animals and humans does not permanently deplete the resource. Fossil fuels, while theoretically renewable on a very long time-scale, are exploited at rates that may deplete these resources in the near future (see: Hubbert peak).

Renewable energy resources may be used directly, or used to create other more convenient forms of energy. Examples of direct use are solar ovens, geothermal heating, and water- and windmills. Examples of indirect use which require energy harvesting are electricity generation through wind turbines or photovoltaic cells, or production of fuels such as ethanol from biomass (see alcohol as a fuel).

A parameter sometimes used in renewable energy is the tonne of oil equivalent (toe). This is equal to 10,000 Mcal or 41,868 MJ of energy.

For aspects of renewable energy use in modern societies see Renewable energy development. For a general discussion, see future energy development. Template:TOCright

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Small scale energy sources

There are many small scale energy sources that generally cannot be scaled up to industrial size. A short list:

• Piezoelectric crystals generate a small voltage whenever they are mechanically deformed. Vibration from engines can stimulate piezoelectric crystals, as can the heels of shoes
• Some watches are already powered by kinetics, in this case movement of the arm
• Electrokinetics generate electricity from the kinetic energy in water that is pumped through tiny channels
• Special antennae can collect energy from stray radio waves or theoretically even light (EM radiation).

Issues

Aesthetics, habitat hazards and land use

Some people dislike the aesthetics of wind turbines or bring up nature conservation issues when it comes to large solar-electric installations outside of cities. Some people try to utilize these renewable technologies in an efficient and aesthetically pleasing way: fixed solar collectors can double as noise barriers along highways, roof-tops are available already and could even be replaced totally by solar collectors, amorphous photovoltaic cells can be used to tint windows and produce energy etc.

Some renewable energy capture systems entail unique environmental problems. For instance, wind turbines can be hazardous to flying birds, while hydroelectric dams can create barriers for migrating fish - a serious problem in the Pacific Northwest that has decimated the numbers of many salmon populations. Burning biomass and biofuels causes air pollution similar to that of burning fossil fuels, although it causes a lower greenhouse effect since the carbon placed in the atmosphere was already there before the plants were grown, rather than being "new" carbon from fossil fuels .

Another problem with many renewables, especially biomass and biofuels, is the large amount of land required, which otherwise could be left as wilderness.

Concentration

Another inherent difficulty with renewables is their variable and diffuse nature (the exception being geothermal energy, which is however only accessible in exceptional locations). Since renewable energy sources are providing relatively low-intensity energy, the new kinds of "power plants" needed to convert the sources into usable energy need to be distributed over large areas.

Electrical power consumption in Western countries averages about 100 watts continuously per person (i.e. about 1 MWh per year). In cloudy Europe this would require about eight square meters of solar panels, assuming a below-average solar conversion rate of 12.5%. Systematic electrical generation requires reliable overlapping sources or some means of storage on a reasonable scale (pumped-storage hydro systems, batteries, hydrogen fuel cells, etc). So, because of current costs of such energy storage systems, a stand-alone system is only economic in rare cases, or where a connection to a public grid would be impractical.

Proximity to demand

The geographic diversity of resources is also significant. Some countries and regions have significantly better resources than others in particular RE sectors. Some nations have significant resources at distance from the major population centers where electricity demand exists. Exploiting such resources on a large scale is likely to require considerable investment in transmission and distribution networks as well as in the technology itself.

Rooftop photovoltaic arrays are especially attractive in that most of the power they produce is consumed in the structure on which they are mounted or in other nearby buildings.

Availability

One recurring criticism of renewable sources is their intermittent nature. Sunlight is only available during the day (50% of the time, on a yearly basis). Wind energy is somewhat more available, while geothermal and wave energy are continuously available, although wave intensity varies by season. A wave energy scheme installed in Australia is generating electricity with an 80% availability factor.

Fossil fuels

Template:Main Renewable energy sources are fundamentally different from fossil fuel or nuclear power plants because the Sun will 'power' these 'power plants' (meaning sunlight, the wind, flowing water, etc.) for the next 4 billion years. They also do not directly produce greenhouse gases and other emissions, as fossil fuel combustion does. Most do not introduce any global new risks such as nuclear waste.

Fossil fuels are not considered a renewable energy source, but are often compared and contrasted with renewables in the context of future energy development.

The traditionally, though not universally, held Western (biogenic) theory postulates that fossil fuels are the altered remnants of ancient plant and animal life deposited in sedimentary rocks. They were formed millions of years ago and have rested underground, mostly dormant, since that time.

In contrast, the Abiogenic petroleum origin theory states that petroleum (or crude oil) is primarily created from non-biological sources of hydrocarbons located deep in the Earth. This view was championed by Fred Hoyle in his book The Unity of the Universe.

Though it is possible to produce complex hydrocarbons artificially by using the Fischer-Tropsch process, this process does not generate energy, and cannot be considered a large scale solution to the energy problem.

The coal industry in the US is publicly claiming coal is renewable energy because the coal was originally biomass. However, the biomass of fossil fuels was produced on the time scale of millions of years through a series of events and it is considered to be a deposit of energy, not an energy flow. Some scientist hold the view that the formation of fossil fuels was a one-time event, made possible by unique conditions during the Devonian period, such as increased oxygen levels and huge swamps.

When the term renewable was introduced (see Defining renewable within this article), it was a generally held belief that the Earth's sources would be depleted within some 50 years. Since then, large deposits of deep-Earth oil have been found, which has extended this timetable. Because the current rate of consumption exceeds the rate of renewal (if, indeed, there is renewal of fossil fuels), the Earth will eventually run out of fossil fuels (see peak oil).

Transmission

If renewable and distributed generation were to become widespread, electric power transmission and electricity distribution systems might no longer be the main distributors of electrical energy but would operate to balance the electricity needs of local communities. Those with surplus energy would sell to areas needing "top ups". That is, network operation would require a shift from 'passive management' - where generators are hooked up and the system is operated to get electricity 'downstream' to the consumer - to 'active management', wherein generators are spread across a network and inputs and outputs need to be constantly monitored to ensure proper balancing occurs within the system. Some Governments and regulators are moving to address this, though much remains to be done. One potential solution is the increased use of active management of electricity transmission and distribution networks. This will require significant changes in the way that such networks are operated.

However, on a small scale, use of renewable energy that can often be produced "on the spot" lowers the requirements electricity distribution systems have to fulfill. Current systems, while rarely economically efficient, have proven an average household with a solar panel array and energy storage system of the right size needs electricity from outside sources for only a few hours every week. Hence, advocates of renewable energy believe electricity distribution systems will become smaller and easier to manage, rather than the opposite.

Historical usage of renewable energy

Throughout history, various forms of renewable and non-renewable energies have been employed.

• Wood was the earliest manipulated energy source in human history, being used as a thermal energy source through burning, and it is still important in this context today. Burning wood was important for both cooking and providing heat, enabling human presence in cold climates. Special types of wood cooking, food dehydration and smoke curing, also enabled human societies to safely store perishable foodstuffs through the year. Eventually, it was discovered that partial combustion in the relative absence of oxygen could produce charcoal, which provided a hotter and more compact and portable energy source. However, this was not a more efficient energy source, because it required a large input in wood to create the charcoal.
• Animal power for vehicles and mechanical devices was originally produced through animal traction. Animals such as horses and oxen not only provided transportation but also powered mills. Animals are still extensively in use in many parts of the world for these purposes.
• Human power for vehicles, mechanical devices and individual non-machine-aided transportation has been employed throughout human history. Slaves have been used for powering boats and powering construction machinery such as that used to build the Egyptian pyramids. Today, slaves have largely been replaced by other sources of power to the degree that the average American accesses the same amount of power that otherwise would require 50 slaves. One of the largest uses of human power today is bicycling.
• Water power eventually supplanted animal power for mills, wherever the power of falling water in rivers was exploitable . Water power through hydroelectricity continues to be the least expensive method of storing and generating dispatchable energy throughout the world. Historically as well as presently, hydroelectricity provides more renewable energy than any other renewable source.
• Animal oil, especially whale oil was long burned as an oil for light.
• Wind power has been used for several hundred years. It was originally used via large sail-blade windmills with slow-moving blades, such as those seen in the Netherlands and mentioned in Don Quixote. These large mills usually either pumped water or powered small mills. Newer windmills featured smaller, faster-turning, more compact units with more blades, such as those seen throughout the Great Plains. These were mostly used for pumping water from wells. Recent years have seen the rapid development of wind generation farms by mainstream power companies, using a new generation of large, high wind turbines with two or three immense and relatively slow-moving blades. Today, wind power is the fastest growing energy source in the world.
• Solar power as a direct energy source has been not been captured by mechanical systems until recent human history, but was captured as an energy source through architecture in certain societies for many centuries. Not until the twentieth century was direct solar input extensively explored via more carefully planned architecture (passive solar) or via heat capture in mechanical systems (active solar) or electrical conversion (photovoltaic). Increasingly today the sun is harnessed for heat and electricity.
• Attempts to harness the power of ocean waves appears in drawings and patents back to the 19th century. Modern attempts to capture wave power began in the 1970's by Professor Steven Salter who started the Wave Energy Group at the University of Edinburgh in Scotland. There are several pilot plants generating power into the grid, and many new and curious designs are in various stages of development and testing.

See also

• Nuclear power phase-out
• Renewable energy development
• Renewable energy links
• Soft energy path
• Sustainable energy
• Wave Power
• Wind power
• Tidal power

External links

• Atlas of Renewable Energy (in English, French & German)
• World Council for Renewable Energy WCRE
• Surface meteorology and Solar Energy - a renewable energy resource for data and images
• Green Mountain Energy
• Renewable Energy News from around the world
• Renewable Energy Projects and Daily News
• An Appropriate Technology Future
• Renewable Energy Projects (site in Spanish)
• Renewable Energy
• World Oil Boycott Grassroots Organization
• Green Progress alternative energy news
• SolarDrome Renewable Energy from Around the Web
• Technology turns greenhouse gas emissions to clean air biofuels
• International Energy Foundation
• Alternative Energy newsletter for Research Professionals
• National Renewable Energy Laboratory (American)
• Genome News Network (GNN) Energy News Collection of articles about how advances in genomics is leading to advances in energy production.
• Centre for Alternative Energy (European)
• Carbon Activism for Beginners.
• Renewable Energy Media Analysis — US Election 2004 Web Monitor
• EU Intelligent Energy, energy efficiency and renewables.
• French Agency for the Environment and Energy Management, fields of activity : air quality, wastes, energy-efficiency and renewables, environmental management, polluted soils, transportation
• Intermediate Technology Development Group
• The Hydrogen Expedition Renewable energy world record
• Abiogenic Gas Debate On the possible abiogenic origin of fossil fuels
• Green Wiki Collective articles on renewable energy and other topics related to sustainable living
• Energyorbit :: Towards Sustainable Power and Renewable Energy
• The Source for Renewable Energy A directory to more than 9000 renewable energy businesses worldwide
• Environmental Finance magazine
• Renewables vs Energy Efficiency Where should i spend my money if i want to have a low carbon home?
• European Union website about renewable energy
• The wide world of renewable energy
• Offshorewind.net Information on offshore wind energy in the United States.
• sterling Planet
• Renewable Energy - Beginner's tutorial on using renewable fuel in a diesel engine
• Alternative Energy: News Consolidated News Links

References

• U.S. Energy Information Administration provides a wide range of statistics and information on the industry.
• Boyle, G. (ed.), Renewable Energy: Power for a Sustainable Future. Open University, UK, 1996.
• U.S. DOE Energy Efficiency and Renewable Energy (EERE) Home Page