Courtney Gwin's List: Renewable energy

• When certain semiconducting materials, such as certain kinds of silicon, are exposed to sunlight, they release small amounts of electricity. This process is known as the photoelectric effect. The photoelectric effect refers to the emission, or ejection, of electrons from the surface of a metal in response to light. It is the basic physical process in which a solar electric or photovoltaic (PV) cell converts sunlight to electricity.  
  
   Sunlight is made up of photons, or particles of solar energy. Photons contain various amounts of energy, corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the PV cell (which is actually a semiconductor).  
  
   With its newfound energy, the electron escapes from its normal position in an atom of the semiconductor material and becomes part of the current in an electrical circuit. By leaving its position, the electron causes a hole to form. Special electrical properties of the PV cell—a built-in electric field—provide the voltage needed to drive the current through an external load (such as a light bulb).
•  There are four main types of solar energy technologies:
  1. Photovoltaic (PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials.
  2. Concentrating solar power (CSP) systems, which concentrate the sun's energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
  3. Solar water heating systems, which contain a solar collector that faces the sun and either heats water directly or heats a "working fluid" that, in turn, is used to heat water.
  4. Transpired solar collectors, or "solar walls," which use solar energy to preheat ventilation air for a building.
• : A 10% efficient PV system in most areas of the United States will generate about 180 kilowatt-hours per square meter. A PV system rated at 1 kilowatt will produce about 1800 kilowatt-hours a year. Most PV panels are warranted to last 20 years or more (perhaps as many as 30 years) and to degrade (lose efficiency) at a rate of less than 1% per year. Under these conditions, a PV system could generate close to 36,000 kilowatt-hours of electricity over 20 years and close to 54,000 kilowatt-hours over 30 years. This means that a PV system generates more than $10,000 worth of electricity over 30 years.
• So, today's commercial PV systems are about 7% to 17% efficient,
• Some experimental PV cells now convert nearly 40% of the energy in light to electricity.

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• Turbine blades and towers can pose a threat to flying wildlife such as birds and bats.

• species and habitats from wind power developments.

   

  The program also works with other federal agencies to develop guidelines that enable developers to me
• et the statutory, regulatory, and administrative requirements for protecting wildlife,
• national security, and public safety. For example, the program works with the Department of the Interior to develop wildlife siting guidelines and is involved in interagency efforts to address the potential impacts of operating wind turbines on defense and civilian radar systems.

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• What do we mean by photovoltaics? First used in about 1890, the word has two parts: photo, derived from the Greek word for light, and volt, relating to electricity pioneer Alessandro Volta. So, photovoltaics could literally be translated as light-electricity
• PV cells are electricity-producing devices made of semiconductor materials.
• PV systems provide power for many small consumer items, such as calculators and wristwatches.
• Many road and traffic signs along highways are now powered by PV. In many cases, PV power is the least expensive form of electricity for performing these tasks.

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• DOE is investing in approaches across the development pipeline—from basic cell technologies to manufacturing scaleup to total system development—that demonstrate progress toward minimizing the effective life-cycle cost of solar energy

• and university-led projects that will receive up to $21 million in funding to address this critical l
• This i
• s the first competitive solicitation that the OBP Feedstock Platform has been able to run in several years. It is the first time OBP has formally partnered with industria

• Alabama is expanding its production capacity of biofuels—especially biodiesel—in Huntsville as well as in Monroe and Covington Counties (see Figure 1); however, its main population centers (Montgomery, Birmingham, and Mobile) lack the refueling stations to deal with the existing renewable-fuel-capable vehicles (see Figure 2).

   

   

   

   

   

   
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  Heavily forested, Alabama lies in the middle of the United States’ wood-rich Southeast and is using biomass for heat and power as well—the state recently instituted a tax deduction for wood-burning heating systems.  The statute allows taxpayers to deduct the cost and installation of a wood-burning heating system from their total taxes. 
• Rejected Watermelons: The Newest Renewable Energy Source (8/27)
• Scientists Force Fungus to Have Sex to Create Biofuel (8/11)
• Yeast Strain Could Help Fast-Track Biofuel Production (7/31)
• oule Adds CO₂ to Sunlight to Make Fuel (7/26)

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• Geothermal energy is an enormous, underused heat and power resource that is clean (emits little or no greenhouse gases), reliable (average system availability of 95%), and homegrown (making us less dependent on foreign oil).
• Hot water near Earth's surface can be piped directly into facilities and used to heat buildings, grow plants in greenhouses, dehydrate onions and garlic, heat water for fish farming, and pasteurize milk. Some cities pipe the hot water under roads and sidewalks to melt snow. District heating applications use networks of piped hot water to heat buildings in whole communities.
• A geothermal heat pump system consists of pipes buried in the shallow ground near the building, a heat exchanger, and ductwork into the building. In winter, heat from the relatively warmer ground goes through the heat exchanger into the house. In summer, hot air from the house is pulled through the heat exchanger into the relatively cooler ground. Heat removed during the summer can be used as no-cost energy to heat water.

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• Stationary Power Stations

   

  Stationary fuel cells can be used for backup power, power for remote locations, distributed power generation, and cogeneration (in which excess heat released during electricity generation is used for other applications).

• Portable Devices

   

  Fuel cells can power almost any portable application that typically uses batteries, from hand-held devices to portable generators.

• Transportation

   

  Fuel cells can also power our transportation, including personal vehicles, trucks, buses, and marine vessels, as well as provide auxiliary power to traditional transportation technologies. Hydrogen can play a particularly important role in the future by replacing the imported petroleum we currently use in our cars and trucks.

• Why Fuel Cells?

   

  Environmentally Friendly

   

  Fuel cells directly convert the chemical energy in hydrogen to electricity, with pure water and potentially useful heat as the only byproducts.
• A conventional combustion-based power plant typically generates electricity at efficiencies of 33 to 35 percent, while fuel cell systems can generate electricity at efficiencies up to 60 percent (and even higher with cogeneration).
• gasoline engine in a conventional car is less than 20% efficient in converting the chemical energy in gasoline into power that moves the vehicle under normal driving conditions. Hydrogen fuel cell vehicles, which use electric motors, are much more energy efficient and use 40-60 percent of the fuel's energy

• Components

   

  A single fuel cell consists of an electrolyte sandwiched between two electrodes, an anode and a cathode. Bipolar plates on either side of the cell help distribute gases and serve as current collectors.
• Reducing cost and improving durability are the two most significant challenges to fuel cell commercialization.

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• Hydrogen is an energy carrier, not an energy source—it stores and delivers energy in a usable form. It is abundant in nature but must be produced from compounds that contain it.
• esearchers are developing a wide range of technologies to produce hydrogen economically from a variety of resources in environmentally friendly ways.

• Natural Gas Reforming

   

  Hydrogen can be produced from methane in natural gas using high-temperature steam. This process, called steam methane reforming, accounts for about 95 percent of the hydrogen used today in the U.S. Another method, called partial oxidation, produces hydrogen by burning methane in air. Both steam reforming and partial oxidation produce a "synthesis gas," which is reacted with water to produce more hydrogen.

• Renewable Electrolysis

   

  Electrolysis uses an electric current to split water into hydrogen and oxygen. The electricity required can be generated using renewable energy technologies, such as wind, solar, geothermal, and hydroelectric power.

• Gasification

   

  Gasification is a process in which coal or biomass is converted into gaseous components by applying heat under pressure and in the presence of steam. A subsequent series of chemical reactions produces a synthesis gas, which is reacted with steam to produce more hydrogen that then can be separated and purified. Producing hydrogen directly from coal by gasification and reforming processes is much more efficient than burning coal to make electricity that is then used to make hydrogen. Researchers are developing carbon capture and sequestration technologies to separate and store the carbon dioxide (CO₂) produced in this process. With carbon capture and sequestration, hydrogen can be produced directly from coal with near-zero greenhouse gas emissions.

   

  Like coal, biomass can be gasified using high temperatures and steam to produce hydrogen. Because biomass resources consume CO₂ in the atmosphere as part of their natural growth process, producing hydrogen through biomass gasification releases near-zero net greenhouse gases.

• Renewable Liquid Reforming

   

  Biomass can also be processed to make renewable liquid fuels, such as ethanol or bio-oil, that are relatively convenient to transport and can be reacted with high-temperature steam to produce hydrogen at or near the point of end-use.

• Nuclear High-Temperature Electrolysis

   

  Heat from a nuclear reactor can be used to improve the efficiency of water electrolysis to produce hydrogen. By increasing the temperature of the water, less electricity is required to split it into hydrogen and oxygen, which reduces the total energy required.

• High-Temperature Thermochemical Water Splitting

   

  Another water-splitting method uses high temperatures generated by solar concentrators (special lenses that focus and intensify sunlight) or nuclear reactors to drive a series of chemical reactions that split water. All of the chemicals used are recycled within the process.

• Photobiological and Photoelectrochemical

   

  When certain microbes, such as green algae and cyanobacteria, consume water in the presence of sunlight, they produce hydrogen as a byproduct of their natural metabolic processes. Similarly, photoelectrochemical systems produce hydrogen from water using special semiconductors and energy from sunlight.

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