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How is Electricity Generated?

January 14th, 2014 | Posted by Dawn Richards in Ask the Expert

One of the Most Important Things We Don’t Understand

Long ago, the energy we used to do things like heat and cook came from locally sourced firewood. It was easy to gauge how much we needed and how much we had left. It was hard work to chop and haul that energy source, so folks probably didn’t keep putting wood on the fire when they didn’t need the heat. Now that obtaining energy in the form of electricity is as easy as flipping a switch, we don’t have much reason to think about where it comes from and how it’s made.

How is Electricity Generated? {The Dirt on Green}

According to the World Bank, all but about 1 billion of us have access to electricity. This doesn’t mean there are a billion people without a source of energy – it’s just not in the form of electricity. Those without access, and some with limited access, still rely solely on solid fuels like coal and wood for heating and cooking.

That leaves about 6 billion people, most of whom probably rely on electricity virtually every minute of every day. I recently asked a random assortment of ten people to explain how electricity is generated. The result? All but two of them hadn’t the faintest idea how burning coal, nuclear reactions or spinning wind turbines leads to the electricity that powers our lives. One of the reasons that electricity remains such a mystery is that we don’t need to think about it.

How Much Do We Use?

Six billion people use a lot of electricity. Together, we required the production of over 22,000 terawatt hours (TWh) of electricity in 2011. Tera-what? The metric prefix ‘tera’ indicates a trillion of something. For perspective, it would take just 1 TWh of electricity to light 10 billion 100W light bulbs for an hour.

How is Electricity Generated? {The Dirt on Green}

With a population of a bit over 300 million, Americans comprise 4.45% of the world’s population (US Census Bureau data), yet we consumed 21.5% of the electricity generated worldwide. In 2011, more than half of our electricity came from coal (42%) and natural gas (25%) combustion combined. Especially in the US, the contribution of natural gas is on the rise, bucking the predicted price increase and remaining competitive with coal.

Compared to the world breakdown of fuels, we’re not that far off, except that hydropower comprises a greater proportion of global electricity production (15.8%) than it does in the US (just a few percent).

I’m a Little Teapot, Short and Stout

More than 80% of the world’s electricity is generated through thermal generating systems. Fuels like coal, natural gas, oil and even biomass (like wood and animal waste) are burned in large furnaces. The resulting heat is used to boil water.

The steam travels through boiler pipes where the pressure and speed turns the blades of a turbine. That mechanical energy is converted into electrical energy inside the generator because of the relative rotation between magnets and an electrical conductor.  The resultant electricity is run through transformers before beginning its journey along the electrical grid.

How is Electricity Generated? {The Dirt on Green}

Nuclear power is a mystery to many people, but in simplest terms, nuclear electricity generation is just another way to boil water. When radioactive materials like

Uranium-235 are bombarded with neutrons they split apart in a process called fission. This process releases a tremendous amount of energy in the form of heat. After that, it is the same as burning fossil fuels: the heat boils water, the water turns to steam and steam turns a turbine which is attached to a generator. Voila, electricity! Interestingly, December 10th marked the end of a 20 year program called “Megatons to Megawatts” whereby the United States purchased the uranium from 20,000 retired Russian warheads and processed it for use in power plants. Since 1993, 10% of our electricity supply has come from this material. That’s more than all alternative energy sources combined. Even though we’ve received our last shipment, the uranium from those warheads will be providing Americans with electricity even after 2020.

How is Electricity Generated? {The Dirt on Green}

It is worth noting that a technology called solar thermal electric generation has begun to have an impact on US markets in the past few years. Clustered in the US Southwest, these facilities use various methods to focus the sun’s energy to boil water which generates electricity as described above. Though this technology still occupies a very small share of the market, a recent report by the US Energy Information Administration reports that several new large installations are about to double the electricity generating capacity of this method.

Mother Nature Turns the Turbine

Humans have been using the sun, water and wind as energy sources since the beginning of time, yet they comprise what we call alternative energy. To generate electricity, wind and water turn the turbine directly, skipping the energy-losing step of boiling water, and the rest of the process is the same.

The immense natural power of water can be used to turn a turbine through a variety of methods including channeling through dams, submerging the turbine in an area with predictable tides, using the pressure created by ocean waves, and even small turbines submerged in minimally disturbed rivers and waterfalls. Hydropower is not without problems but continues to comprise a large portion of the renewable energy sector.

Wind power continues to be a rapidly growing source of renewable energy throughout the world. Detailed wind maps are constructed to find locations with adequate non turbulent wind without too many powerful bursts. Installations can be found on mountain ridges, plains, coastlines, and in coastal ocean waters. Wind power is not without controversy. Just last month amidst great controversy, the Federal Register published a decision designed to promote the development of wind power but may lead to an increase in the deaths of golden and bald eagles.

How is Electricity Generated? {The Dirt on Green}

Geothermal electricity generation is another example of using nature to turn that turbine. The United States led the world in geothermal electricity generation last year, providing us with four times as much electricity as solar based methods. These plants use the steam that is produced from heat that occurs naturally a few miles beneath the Earth’s surface in some places.

Photovoltaic cells, what most of us think of as solar power, are unique in that there is no steam or turbine. The special materials used in photovoltaic cells are called semiconductors. When sunlight strikes certain semiconductor materials (e.g., silicon) photons are absorbed and electrons are released. We can then channel these electrons into an electrical current. Materials that do not exhibit this photovoltaic effect just absorb the photons and heat up when struck by sunlight. Technological advancements in semiconductor materials that can be applied in thin layers and still efficiently turn photons into electricity are progressing so rapidly that the IEA predicts photovoltaics will grow more than 11.5% a year through 2040.

The Most Efficient Solution

The energy mix that powers your home with electricity depends on where you live and your utility company. For instance, power companies serving California, Oregon and Washington generate more of their electricity using hydropower than any other single source. In contrast, the primary source for the south atlantic states is coal. As consumers we don’t have much control over our electricity sources, but Amory Lovins, physicist and energy expert, called energy efficiency the world’s biggest untapped energy resource. By using less energy to perform the same task, we are not sacrificing comfort or convenience, simply using less electricity. The justification begins with the money you can save and has far reaching implications. Switching to energy efficient products is easy and EnergyEarth is here to help.

Dawn Richards of EnergyEarth

© 2014 Energy Earth LLC. All Rights Reserved

Sources:

http://www.iea.org/publications/freepublications/publication/KeyWorld2013.pdf

http://www.eia.gov/todayinenergy/detail.cfm?id=13791

http://www.nytimes.com/2013/11/15/business/international/last-shipment-of-nuclear-fuel-from-russian-bombs-heads-to-us.html?_r=0

http://phys.org/news/2013-12-solar-power-sector-small.html#jCp

http://energycommerce.house.gov/press-release/subcommittee-examines-role-diverse-electricity-generation-portfolio

http://keshefoundation.org/image/keshe_generator/Electricity_Production_400.jpg

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2 Responses

  • Kevin F Swartz says:

    Good article. I would like to suggest that some time be spent on the need to generate power in real time-matching supply and demand constantly. This requires a reserve margin or power plants that just ‘stand around’ just in case there is a spike on demand, a mechanical isssue or mother nature-and that is what makes it so expensive. I would also suggest that in order to increase renewables, you need storage because renewable generation does not match demand.

    • Thank you for your astute comment. Although this article was intended to be a simple primer on electricity generation, you are right that it would be useful to address the concepts of peak demand and other factors that require use of the operating and supplemental reserves. Since we tried to keep this post brief, we also knowingly omitted discussions of energy storage and transmission as critical in the development of renewables.



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