Category Archives: Fuel Sources

Our Electric Grid – Renewable Energy Sources, Part 1

Being in the power industry, and especially since I am currently working at a coal power plant, I get a lot of people asking me about Renewable Energy. More specifically, why can’t we just go to all renewable energy, what’s the hold up? So I’d like to spend the next few blogs in my Our Electrical Grid series to discuss some of the ins and outs of renewable energy.

In 2014, in the US, renewable energy accounted for less than 15% of our total power generation. There are 5 main types of renewable energy sources right now:

  1. Hydroelectric – 6%
  2. Wind – 4.4%
  3. Biomass – 1.75
  4. Solar – 0.4%
  5. Geothermal – 0.4%

http://www.eia.gov/tools/faqs/faq.cfm?id=427&t=3

about-renewable-energy

http://www.occupy.com/article/renewable-energy%E2%80%94-jobs-producer%E2%80%94wins-vote-north-carolina

Both Biomass and Geothermal utilize the basic steam cycle. A Biomass plant is much like a coal plant, except it has special processes to handle and combust the biomass material. While geothermal extracts its heat from below the Earth’s surface, which is primarily from the decay of radioactive elements. Please review my Electrical Generation Basics post for this topic to review the steam cycle.

Hydroelectric and wind are both similar, as they directly convert their energy source into a rotational motion – The sole purpose of the steam cycle is to cause the turbine to rotate. After the energy is converted into a rotational force, hydroelectric, wind, biomass, and geothermal all use a similar type of generator to convert the rotational energy into electrical energy. You may also review my Electrical Generation Basics post for this topic to review the basics of the electrical generator.

Solar is very different from the other renewable energy sources. It essentially uses a photosynthesis process to convert the sun’s energy into electricity. I will cover this topic in a later post on my renewable energy series.

For my next blog post in this series, it is important to understand the sources of energy for renewables – Biomass, Geothermal, and Hydroelectric are the only renewable sources that provide a consistent source of electricity 24/7. Next week I will be discussing some of the negatives of renewables – Please sign up and follow me, or check back next week for more!

Does anyone know what type of electrical generation source caused the largest immediate death toll? Please leave an answer in my comments section, and I will provide you with some more insight next week!

Our Electric Grid – Fuel Sources Part 2 (Nuclear Fuel)

In Our Electric Grid – Electrical Generation Basics, I introduced the basic steam cycle in my discussion. In Our Electric Grid – Fuel Sources Part 1, I presented the basics about coal and gas fuel sources. In this part, I am introducing the basics of nuclear fuel sources.

Now I will mention that there are numerous types of reactor designs, including different nuclear fuels, different fuel mixtures, boiling water reactors, pressurized water reactors, and different methods for controlling nuclear reactors. In my future blogs, I will be discussing the GE Hitachi Nuclear Energy – Economic Simplified Boiling Water Reactor (ESBWR), which is one of the reactors I studied for my bachelor’s degree. If you would like me to discuss another type in the future, please let me know in the comments below.

ESBWR

In the ESBWR reactors, uranium 235 (abbreviated U-235). U-235 is actually found naturally, and is mined. Although, natural uranium only contains about 0.7% U-235, the remaining 99.3% is primarily a U-238 isotope, which isn’t useful for reactor fuel. Numerous facilities exist that enrich the uranium by physically separating the isotopes of uranium. Civilian plants typically use 3% – 5% enriched uranium (they are prevented from using anything higher due to nuclear treaties), which is a level that is low enough that it is impossible to create a nuclear weapon with. Theoretically, one kilogram of U-235 can release as much energy as 1500 tons of coal, if it were able to fission 100% of the U-235.

Almost looks like lead or a sort of metal

U-235 – Almost looks like lead or a sort of metal

At the highest level, you can think of the uranium simply as a hot rock. Inside the reactor, while it is operating, the U-235 fuel is fissioning. (In a later blog posts, I will discuss how the process of how fission works in these reactors, safety concerns, and how they are controlled.) The process of the U-235 fissioning produces tremendous amounts of energy in the form of heat. Water is in contact with the fuel rods inside the reactor, which allows for the heat to transfer from the fuel into the water. In the ESWBR plants, the water is actually allowed to boil inside the fuel channel, which creates the steam. From there, it starts the basic steam cycle, as I mentioned in my Our Electric Grid – Electrical Generation Basics post.

nuclearreactor

I will continue discussing nuclear power in the near future, but next week I will begin introducing some information about renewable energy sources – so stay tuned and leave comments/suggestions!!!

Our Electric Grid – Fuel Sources Part 1

Last blog post I discussed some of the basics about how electricity was generated, and introduced the basic steam cycle. This blog I would like to share some information about the primary heat sources for steam cycles of power plants; coal, natural gas, and nuclear.

Coal Plant1

In order to increase the efficiency of coal, which also helps minimize emissions, coal is ground up into a very fine particulate. This is performed inside of a Pulverizer, which uses large steel balls to crush and grind the coal into the very fine powder. The pulverizer is also combined with a Primary Air fan, which blows a large amount of air into the pulverizer that serves two purposes:

  • Blows the pulverized coal out of the pulverizer
  • Mixes a specific amount of air with the coal fines to increase burning efficiency

After the coal leaves the pulverizer, it is directed into coal burners, which assist in directing the coal, and the fire to maximize efficiency and minimize emissions. At the burners, coal is lit off into fire (initially by a natural gas flame, but the coal fire becomes self-sustaining and the natural gas is removed). The fires heat the tubes inside the furnace, which contain water, causing the water to boil into steam. The steam is then “superheated” by sending it through another heat exchanger downstream from the fires. After being superheated, the steam is then sent to the turbine, starting the steam cycle.

Pulverizer

http://www.powermag.com/pulverizers-101-part-ii/

Coal Plant2

There are two different methods for using natural gas – through a gas furnace, or by using a gas turbine. A gas furnace is perhaps the simplest of all the power sources for the steam cycle plants – it is simply done by burning natural gas through burners, similar to how coal is burned after it is pulverized.

The gas turbine is not necessary for a steam cycle, however, they are typically used in conjunction with a steam cycle to increase the efficiency of the gas – these are called combined cycle natural gas plants. In a combined cycle natural gas plant, natural gas feeds a gas turbine, where it is mixed with air and burned. The burning creates additional gasses, and heat, causing the gasses to expand, building up pressure. This pressure from the gas and heat is used to drive the turbine, which also has a generator attached to it. After it exits the turbine, the gas is directed through a water heat exchanger, where it boils the water to steam – this allows these plants to reclaim some of the energy, which would have been lost in the form of heat. Some of these plants also have supplemental natural gas burner elements to aid in controlling and increasing the output of the steam cycle. (http://energy.gov/fe/how-gas-turbine-power-plants-work, https://www.edfenergy.com/energyfuture/generation-gas)

GasTurbinePlant

Thanks for continuing to read my blog! Next week I will continue this discussion of fuel sources, moving to nuclear fuel – please check back, and leave comments!