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  • Are BEVs Really More Energy Efficient Than Fuel Cell Vehicles?

    It is often asserted that it is much more energy efficient to run a BEV than a fuel cell vehicle.

    The comparison usually ignores generating and transmission losses for the electricity though, and often assume solar for the BEV, which rarely happens as solar is only around 1% of the US grid and anyway most cars are charged at night.

    So how do they compare using the current US grid for charging the car, and steam reformation for the hydrogen?

    The US grid of course has some renewables, mostly hydro, but also uses lots of coal.

    For hydrogen, reformation of natural gas is the main way, but in California one third of transport hydrogen is mandated to come from renewables, which is a bigger share than in the US grid and in the same area as renewables plus nuclear, so I will simply compare the fossil fuel portion.

    Here is US electricity generation by source in 2012 (Fig 1)

    So we have coal: 38%

    Natural gas: 30%

    Nuclear: 19%

    Renewables: 12%

    Oil and liquids: 1%

    From the link here:

    'To express the efficiency of a generator or power plant as a percentage, divide the equivalent Btu content of a kWh of electricity (which is 3,412 Btu) by the heat rate. For example, if the heat rate is 10,140 Btu, the efficiency is 34%. If the heat rate is 7,500 Btu, the efficiency is 45%.'

    And following the link to the average heat rates of fuels, ignoring petrol as too small to matter and nuclear as I have already offset it against the renewables component of hydrogen, we have in 2012:

    Coal: 10,498BTU/kwh

    NG: 8,039BTU/kwh

    Dividing by 3,412 gives:

    Coal: 30.8% efficient

    NG: 42.5% efficient

    NB: For those wondering why NG is not much more efficient as the latest combined cycle turbines do way better than that, NG is used a lot for topping peak power, which is much less efficient, for instance for instant on power, which is needed more and more with more intermittent renewables in the grid and which drop with every passing cloud very suddenly, many have to be kept running as 'spinning reserve' without producing any power so that they can fire up quickly, and anyway most US turbines are the cheaper simple cycle, average efficiency ~40%, as they are only used part of the time and have to pay for themselves.

    So weighting by the 30% of NG in the grid and the 38% coal we have:


    So 30.8 + 42.5 = 73.3

    Divided by 2.25 = 32.6

    So the fossil fuel portion of the grid is around 33% efficient

    Transmission and distribution losses 6%:

    Losses wall to battery 10-20%.

    Here are the Nissan Leaf usage figures:

    Including losses from the wall that comes out to around 350Wh/mile
    350*1.06*3 = 1113Wh/mile

    Fuel cell car:

    Natural gas reforming 70%
    (GREET model, 70-72% depending on the CCS assumptions, 2.1 here)

    I am using 10% for compression losses, although they are closing in on 5% with the latest ionic compressors)

    Conveniently 1kg of hydrogen is pretty near one US gallon of petrol in energy terms.
    The Toyota Highlander SUV for which there is the best data and which is considerably larger than a Leaf got 68mpge:

    Using 60mpge for conservatism's sake and 33 kwh/kg of hydrogen then:
    Per mile: 550wh
    550*1.10/0.7 = 865Wh/mile

    The Tesla S uses around 466Wh/mile:

    So at the efficiency and losses of the US grid:
    466*1.06*3 = 1482Wh/mile

    Of course the fuel cell vehicle will not be hitting 60mph in 3 seconds or whatever, but the Toyota Highlander is a reasonably substantial vehicle and can hit the figures I gave.


    Fuel cell vehicle: 865 Wh/mile

    Nissan Leaf 1113 Wh/mile

    Tesla S 1482 Wh/mile

    These figures hardly bear out the contention that battery electric cars are massively more energy efficient than fuel cell cars, which is what is often claimed.

    Tags: energy, transport
    Jan 19 9:12 AM | Link | 66 Comments
  • The UK is to produce a proper balance sheet!
    In a conference this morning the new Chancellor, George Osbourne, said that a new forecasting organization is being set up, headed by Sir Alan Budd, which will make determine likely future growth independently, so that politicians can't juice them by assuming unrealistic growth rates and squeeze in more spending.

    In addition, we are to have the first proper balance sheet showing all the currently off-budget items, including public pensions, which in the UK are due to rise to an additional liability of around 80% of GDP on top on the on-budget ones.

    This hopefully is the start of a political process to rein in a lot of the more extravagant expenditure, as the costs are made more clear to the public.
    80% of people here pay in far more than they receive to pad the pensions of Civil Servants, whilst getting a fraction as much themselves.

    On the downside, there is a splash of paddles as the new Government rows back on plans to cut the banks down to size and they are shifting from a promise to take independent action to saying that they have to wait for what the US does, and can't go far outside that envelope.
    With Geithner in charge, that means the banks carrying on business as usual.
    Action in Europe though may force their hand.
    For the moment European ire is being focused on the hedge funds rather than the banks, as no-one wants to think about their huge problems.
    The $1 trillion bail out is to patch some holes in European banks balance sheets.

    That mythical beast, 'growth' is supposed to eventually complete the bail out after the trillion runs out.
    I am expecting a European program to finally locate the unicorn sometime soon, and it appears to have as much chance of success as getting any money back from the PIIGS, or of getting growth whilst savagely cutting budget deficits at the same time.

    Disclosure: No positions
    Tags: UK Finance
    May 17 5:23 AM | Link | 1 Comment
  • The Euro crisis as seen by the head of the Bank of England
    The excelent Edmund Conway, writing in the Telegraph, has published the comments of Mervyn King, Head of the BOE, on the crisis in Europe and what went on in the meetings about it - and he has been startlingly frank.
    Here he is comparing the present crisis with the previous banking crisis:

    'After all, dealing with a banking crisis was difficult enough, but at least there were public sector balance sheets onto which the problems could be moved.

    Once you move into the sphere of concerns about sovereign debt, there is no answer; there’s no backstop. And it is very important therefore that we hit these problems on the head now, put in place credible solutions to prevent the problems becoming worse.'

    I owuld question whether there are any measures short of the break up of the Euro and default which are credible, but the some of the gravity of the situation is illustrted here.

    There is more in the link about UK cutbacks, and other issues.

    Disclosure: No Positions
    Tags: Europe
    May 14 7:45 AM | Link | Comment!
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