PDS APES 5th Period 2009-10

Using hydrogen to create electricity is an innovative process that is currently in the research and development stage. We may hear about hydrogen power being prevalent in countries like Iceland, but it will be some time before hydrogen power becomes large scale. Nevertheless, many believe hydrogen to be the major energy carrier for the future. Notice I said  that H2 is an energy carrier, not an energy source (like oil, coal & natural gas). This means means we can’t burn H2 like oil to create energy.

A hydrogen fuel cell is a device that creates electricity via electrochemical conversion. These cells are currently used to power hydrogen automobiles. To put it simply, a fuel cell performs this equation:

H2 + O2 —-> H2O

In the process hydrogen is split into its proton and electron, and ELECTRICITY is generated. Water is then created as a by product when the hydrogen combines with an O2 molecule. Click on this link to see an excellent simulation of the reaction going on inside a hydrogen fuel cell: http://videos.howstuffworks.com/ballard/651-ballard-shows-how-a-fuel-cell-works-video.htm

Be sure to recognize that multiple fuel cells must be stacked together into fuel cell stacks in order to generate more power.

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So how exactly do we obtain the hydrogen to store in automobiles? This is where the process of electrolysis comes in. This process essentially performs the reverse reaction of a fuel cell:

H2O —-> H2 + O2

Electricity is used to separate the atoms of a water molecule in order for us to gather the H2. But this electricity used may result from burning fossil fuels; therefore, a carbon footprint can exist in the hydrogen power process although it is not a direct result of using hydrogen fuel cells. (Note: hydrogen can also be gathered by separating methane (CH4)…but this process creates CO2)

Pros of Hydrogen Fuel Cells:

-only emission is H2O

-H2 is the most abundant element in universe

-reliance on hydrogen power lessens reliance on fossil fuels

Cons:

-H2 is volatile

-must expend energy to harvest from thins like water

-lack of infrastructure (hydrogen fueling stations are extremely expensive)

-only in the research and development stage

-H2 in the stratosphere depletes ozone

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Last year, a student send me a 12-minute bit from 60 minutes on coal power. The piece is centered on an interview with Jim Rogers of Charlotte’s own Duke Energy. Watch this, then read on:

*IF the embedded video will not play, try this link: Powered by Coal (60 minutes)

So…what do we do in the short term? Build the “cleanest” coal-powered plants we can build AND try to capture the carbon in the ground? Regardless of our efforts, does it matter if China is not even trying while starting up one new coal-fired power plant A WEEK?!

Is our future “blowing it the wind?”

NPR posted a wonderful series last spring called Power Hungry: Reinventing the U.S. Power Grid. While some place great hopes in wind and solar, the fact remains that coal (and nuclear) provide reliable sources of power for our grid. In the segment, Constant Challenge: Constant Current from Fickle Winds, NPR exposes the main limitations of putting our hopes in wind:

At the Midwest ISO’s control room in Carmel, Ind., talk of a major increase in wind power sends chills down the spine of Rob Benbow, a grid manager. Before dawn on a spring morning, Benbow and a few dozen grid operators are shouting electricity jargon at each other in front of a massive curved screen that’s 20 feet high and 150 feet long.

As people in the Midwest wake up and turn on coffee makers and hair dryers, the operators make sure enough power is being generated to match the surge in demand. A warning signal alerts them that a power plant has unexpectedly turned off. This time, it is someone else’s problem. But Benbow worries that when wind power makes up a significant portion of his grid’s electricity, managing it will cause him frequent problems.

“My biggest fear is if you see 20 percent wind on your system, and then it comes off at a time period where you don’t have resources to replace it — that’s going to, could, result in a blackout situation,” he says.

Wind power is not predictable. That morning, the wind is steadily producing about 3,000 megawatts — about 5 percent of the total power being used in the region. But Benbow says he’s seen wind power become increasingly variable as more wind farms come on line. And grid operators can’t order wind plants to produce like they can other power plants.

“If the wind is not blowing, you just don’t have that resource available,” he says. And when the wind is blowing, it can be hard to make wind turbines shut down. “A lot of these plants are not manned — if we need to turn them off, we have to send a person out to actually do that,” he says.

Lots of other things about wind frustrate the Benbows of the world — wind blows hardest at night when electricity demand is lowest, there currently aren’t ways to store wind for later use, and you can’t count on it on hot summer days when you need it most.

“You can put all that wind in, but I still need to have all this other generation that I need to have available — all my coal, nuclear, all the gas — for my peak load day,” Benbow adds.

So, what do we do?

Here is today’s presentation. While biomass is valued for being essentially carbon-neutral, you cannot ignore all the potential drawbacks to agriculture (erosion, fertilizer, pesticides, feedlots, etc…).

When you think “Modern Wind Technology”, think of Power Plants.

http://www.duurzamevoetafdruk.nl/en/cms/selplaatje.asp?id=223

These power plants include wind turbines that are powered by the wind in order to turn a turbine that powers a generator, and creates electricity that can be used and stored.

http://visual.merriam-webster.com/images/energy/wind-energy/wind-turbines-electricity-production/nacelle-cross-section.jpg

To understand the parts of a turbine and how it works, check out the following websites:

http://guidedtour.windpower.org/en/kids/intro/intronac.htm

http://guidedtour.windpower.org/en/kids/intro/index.htm

One wind turbine generates approximately 2 MW of power.

Wind is less than 1% of the commercial energy market.

Positives:

-No emissions (CO2)

-Multiple land use because of small footprint

-Could go longer than solar power (because of night and day)

-Renewable Energy

Negatives:

-Noise pollution (from the blades)

-variable wind supply (need storage and backup)

-Aesthetics

-Some habitat laws (birdstrikes-birds sometimes fly into them)

This is a funny video from class : ) :

http://www.youtube.com/watch?v=6IjUkNmUcHc

Hey guys, I’m stumped. Question 7g on the study guide talks about how coal can be turned into a gas or liquid fuel (synfuels). First of all, it never explains how this is done. And second, this seems pointless to me because why would we want to coal to different forms if it costs more and requires more mining? Lastly, the book says that gas and liquid coal fuels produce less air pollution than solid coal when burned but more CO2 emissions. That is contradicting!  Any help would be nice.

Hey guys,

Looking over my study guide, I’m confused about the difference between net energy and efficiency. Is there a difference? As I understand it:

Net energy is the amount of energy available minus energy needed to extract/process/etc.

Efficiency is input= output/percent efficient.

Aren’t these definitions basically two different ways of saying the same thing–that the second law of thermodynamics ensures that heat will be lost in all reactions, thus input will never equal output, yet the degree to which energy is lost in the reaction varies?

Thanks!

1. Power

Power is the rate at which Energy is used or being created. Its base unit is in Watts where 1W=(1Joule)/(1second). Power is the basis for rating the amount of energy appliances use over time, like a 100 Watt light bulb will use twice as much energy at any period of time than a 50 Watt bulb.The equation for Power is:

P=E/t

This equation can also be rearranged to find Energy produced: P*t=E

2. Heat transfer

The most common method of turning any Energy in heat, is to transfer heat into steam which will turn a turbine and generator shaft. We can use Heat transfer equations to show how much Energy we need to boil water.

The heat equation uses several variables: Q=Heat energy(calories/BTU’s); m=Mass(grams);c=specific heat, the higher the harder to heat up a material [cal/(J*C)]; and T refers to the change in Temperature. The equation goes like this:

Q=mcT

(remember T is change in temperature!)

3. Price

Calculating Price is the same process as calculating Power, minus the  science! Instead of power we refer to number units bought(units), individual price($/unit) to get the total Price($). Instead of power, price uses a ‘price rate’ or the individual price. Equation:

#Units*Individual Cost= Total Cost

4. Efficiency

Last but not least, we need to be able to calculate efficiency. It doesn’t matter how much Energy we use, if we aren’t using it properly, thats what efficiency is about. Sadly, due to reality all appliances aren’t a 100% efficient so we need to see how much energy we are wasting. For efficiency, we focus on the Input energy, the total energy we put into say a light bulb, multiply that by the efficiency to get an output, an alternate form of energy from what we started (say light/heat). The equation is straight forward:

Input*%efficiency=Output

Today we took a brief look at solar power. Solar makes up a tiny fraction (<1%) of the commercial energy market, but it is doubling every two years. I tried to distinguish between solar electricity technologies and solar thermal (heat) technologies.

When considering solar electricity, it can be done on a small scale (homes/buildings) and a large scale (solar tower power plants). Most folks are familiar with solar panels, or photovoltaic panels, made from two layers of silicon and divide into solar “cells.” These panels can be bolted on existing structures or built into the roof (as shingles). When light hits the panels, electrons are freed from silicon and flow in wiring for immediate use or storage in batteries. Battery storage is critical, since solar incidence (amount of sunlight energy) varies by season and location and of course, since there is no sunlight at night. Small bolt-on systems are a great solution for homes that are off an electrical grid. A good basic explanation of PV technology is in your text, or at HowStuffWorks.com:
http://www.howstuffworks.com/solar-cell.htm

Folks are less familiar with large-scale solar-thermal power plants, like the one seen in the video below from Spain:

A huge field of mirrors follows the sun and focuses the sunlight on a central tower where water is heated to make steam, to turn a turbine, to turn a generator, to make electricity. There are a quite a few of these in the US and other countries.

As for solar thermal technologies, they focus on capturing the sun’s heat (infrared radiation). Unfortunately this year we will not get to tour a local home that incorporates both these techniques. In years past, I’ve taken APES classes to the home of Jeff Martin up at Lake Norman. From the front, Jeff’s home looks like a normal house, but if you walk around back you can see his huge solar roof:

Local Solar Home

Jeff designed the home, not just to produce electricity (the lower 3/5 of that roof) by PV cells, but also to take advantage of passive and active solar thermal technologies.

• Passive techniques: The rear of the home (and the panels) faces south to maximize the sun’s light and heat. Also, the amount of window space is maximized on the south face of the home. A large overhang blocks the more intense, higher sun in the summer but is designed to let the lower winter sun in completely. The home also has concrete floors (with nice wood on top) to absorb the sun’s heat to heat the structure. Finally, the house is super-insulated to retain all this warmth.
• Active techniques. The top 2/5 of the roof (see picture above) has copper sheets with water piped through them via a pump in the basement. The water is heated by the sun, then piped back down to the basement for storage in a huge insulated water tank. This heated water not only provides almost unlimited hot showers, but it can also be circulated through tubing in the concrete floors to provide radiant heating for the structure.

Between all these technologies, Jeff and his family have a house that is heated and lighted in a super efficient fashion. He further works to maximize energy efficiency with Energy Star rated appliances, super insulation, and CFL bulbs. Of course, one of the downsides is the cost–not everyone can afford the technology on this scale. Regardless, solar technologies are becoming more and more prevalent in the USA and enjoy even greater popularity in Japan and Germany.

Wednesday in class we talked about the common fuels that we use. The three most commonly used fuels include Coal, Oil (Crude Oil), and Natural Gas. When comparing the percents of total energy use in the world to total energy use in the US, 76% of the world’s energy use requires fossil fuels while 85% of the US’s energy requires fossil fuels.

http://www.tehrantimes.com/index_View.asp?code=200268

COAL:

Coal is made up of decayed ancient swamp material which tends to be solid hydrocarbons. Coal can also contain Carbon, Sulfur, Magnesium, and Nitrogen. The top three reserves for coal include 1) USA (27%) 2) Russia (17%) , and 3) China. After coal is mined and extracted from the earth, it is primarily used for electricity generation and steel production. Advantages include: Ample supplies, high net energy yield, low cost, well-developed technology, and air pollution can be reduced with improved technology. Disadvantages include: Severe land disturbance, air pollution, and water pollution, severe threat to human health when burned, environmental costs not included in market price, large government subsidies, high Co2 emissions when produced and burned, and radioactive particle and toxic mercury emissions. Coal is projected to last 200-900 years.

http://unclemeat.wordpress.com/2009/09/17/end-of-peak-oil/

Crude Oil:

Oil is a liquid mix of hydrocarbons and decayed remains of ocean plants and animals. Oil is also known as Petroleum. The top three reserves that we drill oil from are 1) Saudi Arabia (25%), 2) Canada (15%), and 3) Iran (10%). After the oil is extracted from the earth, it is primarily used for transportation and sometimes asphalt and plastics. Advantages to using oil include: Ample supply for 42-93 years, low cost, high net energy yield, easily transported within and between countries, low land use, technology is well developed, and efficient distribution systems. Disadvantages include: Need to find substitutes within 50 years, large government subsidies, environmental costs not included in market price, artificially low price encourages waste and discourages search for alternatives, pollutes air when produced and burned, releases Co2 when burned, and can cause water pollution. Oil is projected to last for 42-93 years (less than 100 years).

http://nedgrace.wordpress.com/2009/03/28/natural-gas-prices-drop-to-lowest-level-in-6-years-on-weak-us-economy/

Natural Gas:

Natural gas is a gas mixture of hydrocarbons that comes from oil and coal. 50-90% is methane along with some propane and brutane. The top three reserves for natural gas includes 1) Russia (27%), 2) Iran (15%), and 3) Qatar (14%). After natural gas is retrieved from the earth, it is primarily used for heating spaces and for cooking. Advantages to using natural gas include: ample supplies, high net energy yield, low cost, less air pollution than other fossil fuels, lower Co2 emissions than other fossil fuels, easily transported by pipeline, low land use, and good fuel for fuel cells and gas turbines. Disadvantages include: it’s a nonrenewable resource, releases Co2 when burned, government subsidies, environmental costs not included in market price, methane can leak from pipelines, difficult to transfer from one country to another, can be shipped across ocean only as highly explosive LNG, and sometimes it is burned off and wasted at wells because of low price. Natural Gas is projected to last 62-125 years.

Today in class, we discussed the properties of Uranium, as well as how it is used in nuclear power plants.

Of all the naturally occurring atoms on Earth, Uranium is the largest in size.  Because of its large size, Uranium is very unstable, and very reactive.  In order to stabilize itself, Uranium (and any other large, unstable atoms) must release matter and/or energy.  There are two types of matter an atom can release: alpha and beta.  Alpha Decay occurs when an atom releases a proton or neutron to stabilize itself, and Beta Decay occurs it releases electrons.  An atom can also release energy, or Gamma Rays.  Unstable atoms naturally release one, two, or all of these three, causing the atom to decay over time.  Given time, Uranium will naturally decay until it becomes the stable lead atom.  An atom is considered radioactive when it constantly releases matter or energy.

A Half Life of an atom is the time period that it takes for half a sample of that atom to decay into a nonradioactive, or stable state.  Uranium 235 has a half life is 710 million years.

Because Uranium is the largest atom, and therefore the most likely to decay, it is also the most radioactive of all the atoms.  This comes in handy with nuclear power plants, which use Nuclear Reactors to create energy from Uranium.

When finding the Uranium to use in nuclear reactors, the only isotope of Uranium that can be used is Uranium-235.  An Isotope is an atom that has the same number of protons, but a different number of neutrons.  The number that follows the atom name (235) is the number of neutrons that the particular isotope has.  Although Uranium-235 is the main source of fuel used, it is also one of the smallest Uranium amounts found in nature (less than 1%).

Nuclear Fission is the atomic process that powers nuclear reactors.  Nuclear fission occurs when the nuclei of a large atom is hit by a neutron, and therefore split, producing a split atom and another free neutron.   A Nuclear Fission Chain Reaction occurs when the neutron that was produced by the original nuclear fission hits another atom’s nucleus, producing more free neutrons, and therefore the chain continues.

The Chain Reaction produces a LOT of heat, which is used to power the nuclear reactors.  In nuclear reactors, Fuel Rods (Uranium) and Control Rods (neutron control) are placed in a containment building.  The fuel rods are placed in a huge vat of water, and when the chain reaction occurs (the speed of which can be controlled by the control rods, which absorb or release neutrons) the water is heated.  The water in the vat then boils, turning into steam.  The steam is sent through Steam Pipes/Heat Exchangers, which use the steam to spin a Turbine, creating energy.  All the steam then travels to the cooling tower, where excess heat is vented through steam stacks.  There are no pollutants released from nuclear Power plants. Here is a cite explaining nuclear reactors in more detail:  http://www.howstuffworks.com/nuclear-power.htm

http://electricalandelectronics.org/wp-content/uploads/2008/10/nuclear-power-plant.jpg

After fuel rods are used, they are still very radioactive, and must be placed securely in storage for hundreds of years.  If not placed in storage, radioactivity can be very harmful to human health.  Released alpha particles are not strong enough to get past the outer layer of human skin, but can cause skin cancer.  Beta particles are a little stronger, and can pass to the epidermal, or inner layer of skin.  Gamma Rays are nasty, and can pass through any type of tissue, bone included.  This is useful for treating diseases like cancer, but harmful in any other way.

I hope this helps!