Energy Flow Diagram

Posted by Max Dunn Tue, 31 Aug 2010 21:37:00 GMT

Have you ever wondered where energy comes from and where it goes? Well, wonder no more – here is a great energy flow diagram from Lawrence Livermore Labs that presents this information in a straightforward way:

Comparing the tiny, thin lines from solar, geothermal and wind against the big, fat lines from fossil fuels shows us that we have a long ways to go to a sustainable energy infrastructure!

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  1. JR said 13 days later:

    This is an awesome chart! It answers all kinds of energy use questions. One puzzling observation: a portion of biomass energy is being used for transportation? I am imagining a fleet of pickups with a bed of rotting biomass in the back capturing methane for the engine – probably not ;-)

    Also, any idea what ‘rejected energy’ is?

  2. Max Dunn said 13 days later:

    Good question JR about what the chart means by biomass for transportation – I had to look it up. It turns out that it isn’t rotting biomass in the back of pickup; it is just fuel ethanol and biodiesel.

    Here are some references:

    LLNL Energy Flow Charts: https://publicaffairs.llnl.gov/news/energy/energy.html

    AER data sources for this diagram: http://www.eia.gov/aer/contents.html

    Renewable Energy Consumption for Transportation: http://www.eia.gov/aer/pdf/pages/sec10_7.pdf

  3. Max Dunn said 13 days later:

    “Rejected energy” is mostly heat I believe.

  4. Max Dunn said 13 days later:

    Here is another energy flow chart that provides more detail than the one above:

    https://publicaffairs.llnl.gov/news/energy/content/energy/electricity_generation/LLNL_Energy_Chart300.jpg

  5. JR said 14 days later:

    Wow, I had no idea there was so much waste! Especially in transportation – I guess that’s the engine heat. Any idea if electric cars will reduce the total waste since batteries are pretty efficient and don’t generate heat like the ICE.

  6. Max Dunn said 14 days later:

    If you look at well-to-wheels, electric vehicles (EVs) save some energy, but not a lot more than gas cars (also called “internal combustion engines” or ICEs). Here is the quick analysis:

    Pulling oil out of the ground and refining it doesn’t take a lot of energy, so the majority of energy is lost in the engine itself, so the efficiency of an ICE is about 20%.

    From wall-to-wheels in an electric car is very efficient, around 70%. But burning coal or natural gas to make the electricity is only about 35% efficient, giving an overall efficiency of 25% – or about 5% more efficient than an ICE.

    However, with newer power plants whose efficiency can be 60%, and with hydro, wind and PV energy, the overall efficiency of an EV goes way up.

    So while an EV powered by old, fossil fuel fired power plants is not much more efficient than and ICE, using better sources of electricity can dramatically increase the efficiency of EVs.

  7. JR said 14 days later:

    Damn heat losses! If it’s not the ICE, then it’s the power plant. Too bad there isn’t a better way to convert waste heat to electricity.

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