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View Diary: Energy - some good news (for once) (237 comments)

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  •  Besides... (none)
    ...you can probably up that 20% by quite a bit by just doing things like storing the energy in flywheels, pumping water uphill, etc. It's not like we don't know how to store energy for later use.
    •  To try and explain the 20% "rule"... (4.00)
      First, note that the grid does not currently store any significant amount of electricity.  The electricity that you're using now is being generated, well, now.  Real time.

      This means that the capacity of reliable generation must be at least as large as the largest possible demand -- generally late afternoons in August on a weekday, when the combination of air conditioners all turned on at once (plus other appliances) result in surging demand.

      Now, wind just might not be blowing at that instant, and so it's reliable generation capacity is generally considered to be 0.  This means that other power sources -- gas, oil, coal, hydro, and nuclear -- can't be torn down immediately, even if we had 100% average generation via wind.  Generally speaking, if wind makes up less than 20% of the generation portfolio, the other 80%+ will be enough to be considered sufficient reliable generation capacity.

      Another important question is: how easy is it to adjust the power output of a power plant in real time; that is, how do you adjust the output to match the electricity demands?  Nuclear is the hardest to adjust: they are generally kept at the same level 24 hours a day and provide a baseline.  Coal and oil can be changed, although generally not on a second-by-second rate.  Natural Gas can be adjusted very quickly.  Hydro can be adjusted, but since the fuel is "free", hydro plants try to generate as much electricity as possible.

      So -- in the short term, more wind plants will reduce natural gas consumption, and in a less direct sense, coal and oil.

      One way to reduce the amount of oil and coal plants required is to address peak demand.  When is demand at its highest?  In the day.  This is why solar has promise -- it provides electricity when the grid needs it most.  So, even though its cost per kWh of generation is still unfavorable, it can be used to reduce peak demand, thereby reducing the need to expand capacity.

      Ultimately, the best way to reduce the amount of coal/oil/gas power plants that need to be built is to reduce demand, especially peak demand.  Buy an electronic thermostat so that you can program your heating and cooling, thereby reducing total and peak usage.  Insulate, and insulate well.  Make sure your hot water heater is insulated and well maintained.  Make sure your boiler is well maintained.  Check the gaskets on your fridge -- leaking cool area wastes.  Use compact flurescent bulbs instead of the cheapo incadescents.  Make sure your home doesn't have drafty doors and windows.  Turn of the freakin' light if you're not in the room.

      We can all reduce demand all the while fighting for a better source of supply.

      •  I don't disagree with this... (none)
        ...and I understand that just about all the power being generated is done in real time. But again, why is that necessary?

        This means that the capacity of reliable generation must be at least as large as the largest possible demand -- generally late afternoons in August on a weekday, when the combination of air conditioners all turned on at once (plus other appliances) result in surging demand.

        Nope, it means that the capacity of reliable supply must be at least as large as the largest possible demand.

        Again, you don't need other power supplies to pick up the slack if you just store wind power in high-wind situations in giant flywheels or pumping water uphill or what have you.

        Say your mean wind is 30% of your energy budget. Make your max energy from other sources 70% (alright, say 75% to cover problems). If wind's at 133% of the average, store that energy in flywheels or something, then just draw it down when the wind's not blowing so hard. As long as you have sufficient storage capacity and you can keep losses down to some manageable percentage, then wind will always be, say, 25% of your energy budget (we'll say we lose 5% in inefficiency and storage problems).

        Just because we don't store our electricity, doesn't mean we can't in the future. We have the technology to do that right now.

        •  Yes, supply is the correct word, but... (none)
          energy storage can't be considered a way to improve supply in the near term.  I'm not suggesting that energy storage cannot be done, but...

          1.  Convert to storage medium.  Every time you convert energy from one source to another (for example, electricity to hydro gravitational potential energy), you'll lose some to inefficiency.  

          2.  Storage.  When storing energy, you'll lose some more.  Flywheels have friction.  Lakes suffer from evaporation.  More energy lost.

          3.  Convert from storage medium.  Again, there's less than 100% efficiency, so more lost.

          4.  Retransmit electricity back over power lines a second time.  More energy lost.

          So, while it's not impossible to store energy, the cost of doing so is fairly high, in fixed cost (building flywheels, dams, etc), marginal cost (operating and maintaining equipment), and effeciency (you don't get a MW back for every MW put in).  Given that green-e is already more expensive than coal, storing it is simply out of the question.

          Besides, in your scenario, what happens if the wind doesn't blow for a week straight?  In other words, what happens if a long stretch of wind is preceeded by a long stretch of no wind?  The stored energy might run out before more wind comes along.

          So, energy storage can become part of the solution eventually, but not for a long time from now.  It's too inefficient, too expensive, and doesn't solve the problem of longer-than-average green-e "fuel droughts".

          Even though I'm skeptical of the hydrogen economy coming within the next 15 years, I'd bet that, in general, the hydrogen economy will arrive before green-e is "too much of the supply" in the USA.  Once we start storing energy as hydrogen, extra wind/solar/etc power can be stored as hydrogen, to be used in elec plants or for auto fuel & home fuel, etc.

          In the short term though, it isn't an issue of major concern, since no states are anywhere near 20% of power generation using high variance green-e production.

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