Earthday presentation

Discussion in 'General' started by bwilson4web, Apr 21, 2018.

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  1. bwilson4web

    bwilson4web Well-Known Member Subscriber

    We decided to have an EV, Plug-in Auto Show, Saturday in honor of Earth Day. We had a Tesla, two BMW i3-REx, and a Prius Prime BUT it was our first attempt. I presented the program.

    This chart comes from the USA Energy Information Administration, Dec 2017 for Alabama.

    Understand I have no problem with burning coal to make electricity. Rather I think it is wrong to burn coal inefficiently. A simple formula show coals can be burned more efficiently:

    The J1772 connector is an SAE standard:

    In the USA there are two types of power distribution. Split phase is what is found in the home, neutral is center tapped and two legs. Commercial power can be three phase:
    Between L1 and L2 in the home, the unloaded voltage will be 120VAC to neutral and between L1-L2, 240 VAC. In three phase, each leg is 120VAC relative to neutral, a white wire, and due to the phase angle, 208 VAC between any pair of legs.

    The pilot signal is how the EVSE tells the car the maximum current, regardless of voltage. At the same time, the car signals to the EVSE that it is there, received the maximum allowed current, and time to enable power to the J1772:
    At -12V between the pilot and ground, the EVSE is broken. It may take 30 seconds before the two drops the link with an error. If someone walks away too soon, they won't see the error show but they will find there was no charge.

    There is a 1k ohm resistor on the pilot line in the EVSE. The a car plugs in, it has a resistor that reduces the voltage to 9 V. Then the EVSE can signal the maximum allowed current by a pulse width modulated, 1 kHz signal. In the example, 75%. Using the chart it corresponds to ~45A. Then the car adds another resistor to lower the voltage to 6V so the EVSE will connect the power pins to the grid. If the car needs a cools environment, it can lower to 3V so the EVSE garage can lower the ambient temperature.

    One issue is many do not know how to answer the question of how much does it cost to drive. The USA EPA provides kWh and gallons per 100 miles. These can quickly give a credible metric of EV versus gas miles, more than 2-to-1, gas over electric:

    Now a replacement EVSE can come in different makes and models:
    The cheapest is a straight replacement. Although tempting, a dual voltage EVS at 16 A can not be used in the older NEMA 5-15 plug. A better but more expensive solution is dual voltage and multiple current.

    An expensive but better approach is a home EVSE with management:
    The EVSE communicates with a server that the user can access and manage with either a personal computer or cell phone.

    When trying to get a commercial installation, the goal is to make a fair trade. Provide 'free' electricity to pay for the trip down:

    Here is an example of typical, PC based management including monthly summary, daily summary, and down to individual charge sessions:

    It can also provide performance graphs fo charge over time:
    Here we see the smart phone App of the same data.
    NOTE: the internal voltage is shown higher than 208VAC. I don't know if it is some local power or more likely, internal voltage measurement error.

    Bob Wilson

    ps. Fuel cell advocates were absent.
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  3. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    If it was cost-effective to build power plants to burn coal more efficiently, then most or all of them would already be of that more efficient type.

    My main issue with coal isn't the inefficiency, it's the public health hazard from the exhaust pumped into the atmosphere. People worry about leaks from nuclear power plants, but the reality is that coal ash pumped into the atmosphere puts a lot more radioactive material into the air we breathe than nuclear power plants! The annual death toll in the U.S. from respiratory illnesses and conditions caused by coal exhaust is variously estimated at between ~13,000 and ~30,000. Worldwide, of course, the death toll is far greater.

    From The 9 Billion: "Death Rate From Nuclear Power Vs Coal? This May Surprise You"

    From New Scientist: "Fossil fuels are far deadlier than nuclear power"

    If humans were rational animals, then long ago we would have shut down every single coal-fired power plant and replaced it with clean, non-polluting nuclear power. Even accounting for the very few nuclear power plant accidents, the death rate from using nuclear power, per kWh generated, is lower than any other type of power generation, and by one estimate, is 4000 times lower than the death rate for coal-fired power plants!.
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  4. bwilson4web

    bwilson4web Well-Known Member Subscriber

    There is a materials challenge of high temperature, steam turbines and many of the inefficient plants were built before these technologies became widely available. With 30 year lifetimes, we saddled with legacy plants. In contrast, China and other developing countries can bring in more modern and efficient plants than we can decommission older plants and build/license new plants.

    I'm OK with nuclear but would prefer newer technology and smaller, modular systems be used. The massive UK nuclear plant, Hinkley C, has turned into a disaster. Some of the liquid fueled, thorium reactors appear (via YouTube) to be interesting. But our species is still faced with a recycling and highly radioactive waste disposal problem.

    Bob Wilson
  5. Martin Williams

    Martin Williams Active Member

    You are wrong about Hinkley C, Bob. It HASN'T turned into a disaster. It started out as one on day one! We have agreed to pay the operators at least twice what offshore wind power is coming in at, for the next 35 years! If it works of course. The contractors have not managed to get one of this design working yet. But that's what you get with greedy, unimaginative, innumerate politicians who are generously funded from industry.

    I would be OK with nuclear too, if the cost of looking after the waste were properly factored into the cost of the power. At the moment the taxpayer will have to face the bill for however long it takes. How much will this cost? Do let me know if you find out. Despite strenuous efforts, I have been defeated by our civil servants who are masters of obfuscation. All I can say is that it is a lot. A very lot!

    You can forget coal. Nobody is going to invest in any technology that uses it. And I imagine gas will be the next one to go. The UK has virtually ditched coal. Even the 'coal' plants are now burning wood pellets, and gas use is being progressively replaced with wind. Power consumption here is falling anyway as more and more private solar and more efficient equipment reduces the demand.
    Last edited: Apr 22, 2018
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  6. bwilson4web

    bwilson4web Well-Known Member Subscriber

    I didn't know one of my brother George is considering a plug-in hybrid. He finds the presentation useful because it gives him a way to evaluate the relative cost of EV and gas miles. No doubt he'll use his requirements to make an informed decision. Living in Arizona, he has choices.

    He asked about heat and I advised a liquid cooled pack which seem to handle temperature extremes better than some of the air cooled packs. We know the first generation Leaf packs had a problem and the Gen-1 Prius although this is a special case.

    Bob Wilson
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