What makes plug-in more efficient...

Discussion in 'Prime Technical Discussion' started by priusmatty, May 28, 2016.

  1. priusmatty

    priusmatty Member

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    ...than the regular Prius with Hybrid Synergy Drive?
     
  2. cproaudio

    cproaudio Speedlock Overrider

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    You're not using gas to propel the car. The electricity from plug in can come from clean source such as solar. During a long descent, a regular Prius's HV battery can be fully charged (80% SOC) before you reach the bottom of the descent. The rest of the way down is wasted energy because the regular has no more battery capacity to store electricity from regen brake. A plugin has big enough battery to accept regen brake all way down the hill. That's extra energy is only able to be captured by the plugin's large battery. The energy captured can be used to propel the car.
    Look at it this way, anyone can install a solar system on their roof and generate free electricity. Not many people can install an oil extractor in their back yard and refine their own gasoline. Sure, you can plant corn in your backyard and make your own ethenol but your Prius won't take it.
     
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  3. alanclarkeau

    alanclarkeau Senior Member

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    Essentially it is for 2 reasons:

    1) The Plug In has a 4.4 kWh battery, compared with 1.3kWh. So the system can do much more electric storing of energy (regenerating brakes etc) which can be used to save more fuel. In theory, a Plug-in which is never plugged in could use less fuel than a regular hybrid, though is a bit heavier with more battery weight.

    2) As the name implies, you can also plug it in - and use electric power from whatever source your home/charger uses to save fuel.
     
  4. priusmatty

    priusmatty Member

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  5. bisco

    bisco cookie crumbler

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    efficiency. that's a good question. it maybe that gasoline is the most efficient, but i would say it's the fuel that does the best job of propelling the car.
     
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  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    In many regions, equivalent electrical power is under 1/2 the cost of gasoline power. So while not technically 'free', from the point of MPG, the cost of electricity adds little to the cost of gas. When you see the huge MPG numbers, remember they are not showing the cost of electricity, and if they did, it would not be much lower.

    In Louisiana, gas is $2.06, but the equivalent power in electricity is $0.83

    The eGallon: How Much Cheaper Is It to Drive on Electricity? | Department of Energy

    (While in mountainous areas the increased size of the battery will let it charge longer on long, steep, downhills, in Louisiana is is just academic)
     
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  7. wjtracy

    wjtracy Senior Member

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    I would say Bisco is on the right track.
    Plug-in vs. hybrid Prius is probably close on efficiency and fossil fuel sipping, and cost in many places. Many plug-in advocates favor a policy shift away from gasoline, so a plug-in does that.
    Electric drive is also more powerful and peppy and that is a major selling factor. The new Prius Prime plug-in will be better than the older Plug In Prius for electric drive power and pep.

    Let's face it a ton of the Plug-in Prius (PiP) were sold in California where they qualify for free HOV.
     
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  8. Redpoint5

    Redpoint5 Senior Member

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    The best gasoline engines are about 35% efficient at converting the chemical energy in gas into propulsion, and only while accelerating. At steady cruising speed, it might only be 20% efficient. The other 80% is lost as heat.

    Electric motors are about 90% efficient at converting the chemical energy into propulsion. Of course, there are losses associated with delivering the energy to the charging location, and there are losses in charging the battery, but gasoline has many losses that must be factored in too, such as the energy required to extract the oil from the ground, to refine it, and to deliver it.

    It turns out that even if the electricity for a car is derived from a fossil fuel power plant, it's still more efficient than than burning gasoline in the vehicle. Total efficiency for an electric car powered by fossil fuels is around 30%, while total efficiency for a gasoline vehicle is about 15%. This improvement in efficiency usually means that electricity is cheaper per mile than gasoline. In Oregon, at current low gasoline prices, it costs about $0.04 per mile to run the Prius on gasoline, and about $0.02 per mile on electricity.

    With electricity being twice as efficient at moving a vehicle, it makes sense that it costs half as much as gasoline.
     
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  9. Wolfie52

    Wolfie52 Senior "Jr" Member

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    I will note, that as often as possible, I charge from the "free" chargers in my community. Although I know that that electricity is not really "free" I take advantage of it while it lasts. Costs me nothing if I plan well.

    Also, I have noticed that my home electric bill has not really increased since I bought my PiP...as a matter of fact, Duke energy sends a usage update every 2 months and my home consistently uses less than even the "energy efficient" homes in my area. This is my goal; reduce CO2 and pollution AND keep my costs/expenses as low as possible.

    I know a lot of people here seem to be very knowledgeable about EV's and PHEV's, not to mention, adept at minor "tweaks" to extend mileage...i just want a car I like to drive, will help reduce GW and pollution, without too much hassle (like waiting HOURS charging before I can use my car) and SAVES ME $$$ This is what will allow PHEV/EV's to "go mainstream" not the minutia about how many cents per mile, efficiency or what time to plug in to achieve a "full charge"...
     
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  10. Vike

    Vike Active Member

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    Thanks! Always worth getting a fresh reminder on the Tragedy of the Commons.

    Free chargers are abused chargers - there's just no avoiding it.
     
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  11. bisco

    bisco cookie crumbler

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    you can't abuse a free charger, that's the whole point.
     
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  12. Vike

    Vike Active Member

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    This is an old argument, and one that always depresses me because it sets PHEVs against BEVs, which strikes me as nuts. Unfortunately, human nature being what it is (hence the Tragedy of the Commons reference), resources that aren't priced tend to be used inefficiently, and that's as true of public chargers as anything else.

    Charging infrastructure is essential for uptake of BEVs, which is why governments at various levels have invested in deploying them, often (and mistakenly) for "free". The PHEV does not need to charge away from home, because it carries an on-board generator, so any "free" charger occupied by a PHEV while a BEV waits is abused, more or less by definition. If the charger is in fact unused and nobody has to wait for anyone else, that's great, but unless you're sitting in a cafe within view of the charger, I don't see how you can guarantee that won't happen.

    The single most effective thing PHEV owners can do to degrade the BEV ownership experience and so discourage BEV sales is to "PiP" free chargers, tying up a resource that is essential for range-extended BEV use to save a few nickels and/or feed their own self-assessed "green cred." That's a lot more likely to happen with free chargers, because as Wolfie helpfully points out "I take advantage of it while it lasts. Costs me nothing if I plan well." A billing meter will fix that problem right quick. When you have to pay to use a charger, it's always more than the electricity is worth, and often more than the gasoline needed for a PHEV to travel the same distance. While that doesn't eliminate use by PHEVs (there's still that "feeling green" thing), it does at least eliminate the free riders, which I expect would have a significant impact on charger availability.

    If all that seems too convoluted, try this: If you have a BEV, depleting one's battery means being stranded or getting a tow, so needing a charge means needing a charge. If you have a PHEV, depleting one's battery means having to burn some gasoline. It does NOT mean:

    1. Being towed home.
    2. Being bankrupted.
    3. Destroying the global ecosystem.

    I'm not saying PHEVs should be banned from using free chargers - that's completely unreasonable and impractical. I am saying that free chargers should not be regarded as reliable power sources for BEVs because they are subject to abuse by free-riding PHEVs that don't need them, so institutions interested in promoting BEV use should not make chargers available for free (counter-intuitive though this may sound).

    Over time, this is going to become self-evident, and I expect free chargers will ultimately be limited to shopping centers, restaurants, movie theaters, casinos, and other venues interested in offering them as a relatively low-cost way of attracting customers that will be "captive" to the facility for some period of time. While I can certainly imagine some reasonable exceptions (e.g., it may be in the interest of highly congested areas to provide ample charging facilities to reduce emissions by PHEVs), in general the use of chargers without such self-interested commercial sponsorship should be paid for by their users, not taxpayers
     
  13. Tideland Prius

    Tideland Prius Moderator of the North
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    I've always wondered about that. Someone did mention that as a greater good, it is still more efficient for a PHEV to continue its journey in electric mode but I completely understand the part where BEVs don't have a backup but PHEVs do.

    However, as you've also mentioned, there will be freeloaders. There's a Model S (company car maybe?) that's always parked at the public charger at a local mall, taking up space for patrons. Eventually the mall added a Tesla home charger so that Model S can charge on its own and leave the L2 chargers for the others but that's a rare occasion that a mall would compromise and spend the extra money.
     
  14. Vike

    Vike Active Member

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    That's an expected outcome for a freebie, which was my point, and it's up to the establishment to work out a solution. Regardless, it underscores the fact that free chargers offered for promotional purposes cannot be regarded as reliable resources in support of increasing the practical range of BEVs. They're a "come on", not useful infrastructure, and nobody should count on being able to access them. Subsidizing public chargers and allowing their use at no cost might seem like a good idea to some institutions, but for the above reasons it's really no help at all if the goal is to expand the market for BEVs.
     
  15. Redpoint5

    Redpoint5 Senior Member

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    I'd like to see the cost of public charging to come down, approaching the cost to charge at home. My work gets power for about half the cost I pay at home ($0.04 / kWh vs $0.08 / kWh), but they do have an additional demand cost (fixed cost for the maximum amps the system is capable of consuming).

    It seems that with commercial rates, they could be profitable selling electricity at home rates.

    While I haven't used a public charger yet, it seems the pricing structure is more about how long the charger is occupied than how much power is delivered. Perhaps this is more important to the bottom line, and helps keep pricing consistent no matter where people go to charge.

    My electric bill increases by about 25 cents each time I charge, so I'm paying about $5 more per month. That gets lost in the noise of taking on 2 roommates.

    ...You mention that you want to save money, and that it's a concern that affects EV's ability to go mainstream. That has everything to do with cents per mile. When gasoline prices climb to record highs, people will be very interested in cheap electric fuel rather than expensive petrol.

    As a side benefit, perhaps Americans will loose weight when they are no longer tempted to purchase a Super Big Gulp at the gas station when they no longer need to get petrol. Lets just hope people don't have a snack shelf near their charging apparatus.
     
  16. alanclarkeau

    alanclarkeau Senior Member

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    Redpoint5 - I'm wondering if you have the decimal point in the right place - 0.04 /kWh?

    My electricity here costs me $0.402 (base cost per kWh is 24.5, but they add meter charge, supply charge (close to $500 per year), which comes to a net 40cents /kWh. It does depend on how much electricity you use - high users still have the same supply charge as people who live alone and don't use much power like me.

    No wonder it's economical to have a PHEV or BEV in USA - the sums I did make it dubious here, unless you have your own solar to tap into (which I do). But there are almost no PHEVs or BEVs available here, TOYOTA didn't bother bringing the Plug-In Prius here.
     
  17. Redpoint5

    Redpoint5 Senior Member

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    Most everything is cheaper in the States, including electricity. Your rates are closer to what Hawaii pays.

    Here is a typical electric and water bill, with electricity coming from hydro. Note that the water bill is for 2 months of use. The house is 2-story, 4 bedroom, 2100 sq/ft.

    [​IMG]

    ...and natural gas bill for those curious:

    [​IMG]
     
    #17 Redpoint5, May 31, 2016
    Last edited: May 31, 2016
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  18. alanclarkeau

    alanclarkeau Senior Member

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    WOW - at those prices, I'd be in a BEV or PHEV tomorrow - a red one (they go faster).
     
  19. Redpoint5

    Redpoint5 Senior Member

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    It's crazy seeing solar panels installed here when electricity is so cheap, and already provided by a renewable resource, and considering how many rainy days we get.

    I'd much rather see the panels being installed in Arizona or southern California (or Australia). The payback period would be much faster in those areas.

    That said, I have thought about installing solar on my house.
     
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  20. bisco

    bisco cookie crumbler

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    i pay 24 cents. gas is cheaper.
     
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