HYDROGEN

In the 1970s, it was proposed that the world would soon change to a “hydrogen economy” and the first World Hydrogen Conference was held in 1976. Although nuclear energy is well suited to produce hydrogen through the electrolysis of water using electricity or the use of heat to produce hydrogen through chemical reactions, no new power plants have been ordered in the U.S. since 1979. Most of the hydrogen obtained in the U.S. today is produced by the reforming of fossil fuels and releases carbon dioxide as a waste (Lattin, 2007). Hydrogen fuel cells (HFCs) provide great promise in their reduction of carbon dioxide emissions, reduction of air pollutants, and the resulting energy security. Before this promise can be realized and hydrogen vehicles become commercially available, significant technological and infrastructure issues must be addressed (IPCC, Document III, 2007).

About 50 million metric tons of hydrogen are produced in the world annually, most of which is used to make fertilizer and other chemical products. Virtually all of the hydrogen which is produced is used at the sites where it is produced. The majority of the hydrogen is produced through the reaction of methane (from fossil fuels) with water to form carbon dioxide and hydrogen (Lattin, 2007).

Although there are as yet no hydrogen powered vehicles which are commercially available in the U.S., progress is being made. In 2003, there were less than 2 dozen hydrogen fuel cell vehicles in the U.S. and by 2006 there were in 150 in California alone. California has 23 hydrogen filling stations with additional stations planned. In 1998, Chicago implemented hydrogen-fueled buses. Since then, other cities have incorporated hydrogen in their public transportation systems, such as Oakland and Palm Springs (Lattin, 2007).

In 2005, the US Congress passed the Energy Policy Act (PL 109-58), whose requirements included the production of a hydrogen fuel infrastructure by 2020 and an increase in the number of hydrogen vehicles. In the year 2002, each hydrogen vehicle cost at least a million dollars each. Vehicles must store a considerable amount of hydrogen on board (Lattin, 2007).

The costs of hydrogen gas production from solar energy, from natural gas combustion, and as a reactant which can produce methanol from carbon dioxide, are falling sharply (Bockris, 2008). As oil prices continue to rise, an affordable production of hydrogen becomes increasingly likely (Bockris, 2007).

SOLAR ENERGY

Solar energy may be passively obtained through certain building architectures or actively obtained through solar collectors. Photovoltaic cells contain the semiconductor silicon; sunlight liberates electrons from silicon atoms creating small electric currents.
a) advantages:
Solar energy is clean and there is an endless supply; it reaches earth for free. The technology for taking advantage of solar energy is improving. Solar water heaters are used in 90% of the households in Cyprus, 65% in Israel. California has 650,000 houses obtaining hot water from solar energy. In 1995, the first contracts were given to solar power plants in the U.S. and the first U.S. photovoltaic solar recharging station partnered with an electric powered bus.
b) disadvantages:
The supply of solar energy is not constant (less during night and cloudy days) and it requires energy to concentrate it. The availability of solar energy depends on where you live: in this country the availability of solar energy is very good in South and excellent in Southwest.

WIND

     Wind energy generates electricity most efficiently with winds 14-24 mph, which is typical of mountain passes and coastlines.  California generates 70% the world's wind power.  In 1900, nearly every farm & ranch west of the Mississippi had at least 1 windmill to draw water. As oil prices rise, countries in regions ranging from Europe to Southeast Asia are increasing their investment in wind energy (Yang, 2007).

GEOTHERMAL

     Heat from deep in the earth's surface heats trapped water deposits (180-370 degrees C); pipes may then retrieve this hat water and steam to generate electricity.  Geothermal energy production may release pollutants such as hydrogen sulfide, radon, and radium.  This energy source is very useful if you live near a deposit.  Since deposits are scarce, it cannot be a major energy substitute.

WATER POWER

     Dams allow rivers to release controlled amounts of water which is then used to generate electricity.  Water power provides 21% world's electricity.  Hydropower provides virtually all Norway's electricity, 74% Switzerland's, 67% Austria's, and 70% Canada's (Canada then sells much to the U.S.).  Methods of extracting ocean thermal energy may never be economically competitive.

     Wind, geothermal, and water power won't be able to generate energy on a large scale and further development may disrupt pristine natural areas. 

     Below is a picture of the world’s second largest hydropower plant on the border between Brazil and Paraguay.

NUCLEAR ENERGY

The nuclei of some atoms are unstable nuclei and periodically eject parts of themselves. Stable elements (such as hydrogen, carbon and oxygen) can have radioactive isotopes (radioisotopes such as carbon-14, oxygen-18, and the radioactive forms of hydrogen known as deuterium and tritium). All of the largest atoms are radioactive (all elements with atomic number above 83 are always radioactive).

1) Why are nuclei unstable?
The nucleus of an atom is composed of two subatomic particles: protons and neutrons (a third particle, electrons, exist outside the nucleus). The electric charges of protons repel other protons and neutrons are needed to keep protons together. If there are more than 83 protons in nucleus, no number of neutrons can make stable. However, neutrons themselves are unstable. In a group of lone neutrons, half will split into a proton & an electron in 12 minutes.

2) Types of Radioactivity: Different elements eject different things from their nucleus.
a) Alpha radiation consists of large particles of 2 protons & 2 neutrons that can be stopped by human skin or a few sheets of paper.
b) Beta radiation occurs when a neutron (a composite particle made of a proton + an electron) ejects its electron and becomes a proton. The ejected electrons of beta radiation are faster moving than alpha radiation and can be stopped by 3 mm of aluminum or 2 cm of wood.
c) Gamma radiation is not particles but waves higher in energy than X-rays. Gamma radiation usually accompanies other forms of radiation as they remove excess energy from unstable nuclei.

3) As unstable nuclei eject parts of themselves, they change their identity and eventually become stable atoms. The time it takes for this to occur is measured in half-lives, the time it takes for 1/2 the sample to decompose. Each radioisotope has its own characteristic half life. The half life of the iodine used for medical examinations is 8 days; that of uranium & plutonium is thousands of years (this will become important as we discuss disposal of radioactive waste).

4) Why is radiation dangerous?
--Radiation disrupts molecules, forming radicals (molecules with unpaired electrons which are very reactive). Radicals then disrupt other molecules, which may kill the cell if essential molecules are destroyed. Disruption of DNA (mutation) is harmful since DNA instructions preserve normal cellular function as well as division rate. The most active cells (cells of the skin, breast, intestine, and blood-producing cells) are the most vulnerable. Only mutations which occur in the ovaries and testes can be passed on to future generations.
Radioactivity can occur from natural sources (background radiation) such as high energy cosmic rays which bombard earth from space and naturally occurring radioactive elements release radiation into air, water, and food. Radon-222 is a naturally occurring radioactive gas. It is harmless when released outdoors but can accumulate indoors to dangerous levels. Radioactive radon particles are more likely to remain in lungs coated with tobacco tar.