Power Plants: Build, Baby, Build…

The recent spike in gasoline prices (the subsequent crash in prices is temporary) amplified the interest in alternative energy sources for transportation. Many of the proposed solutions involve “electric cars”, that is, cars that store and use electrical energy as their primary source of energy for conversion into mechanical drive. This contrasts with “hybrid” drives like the Prius, which primarily use energy stored in gasoline with electrical augmentation to improve efficiency.

There have been millions of words written about these cars and why they are the “future”, but there is one aspect that I have never seen concretely addressed: how to supply power for use in the western United States, where typical transportation distances are much greater than in the Eastern United States and Europe where population density is much higher.

In the western United States a trip of 100 miles each way is not infrequent.  It might not be a daily occurrence, but it happens often enough that a car with only a 100 mile range would be very inconvenient if it couldn’t be recharged rapidly.  Rapid recharging means single digit minutes, not hours.  What does this sort of recharging capability imply for the electrical generation system?

The EPA limits gasoline pumps to 10 gallons per minute, but most average between 5 and 10 gpm.  So let’s say we refuel at 5 gallons per minute. Gasoline has an energy content of approximately 131MJ/gal (mega joules per gallon, please forgive the mixing of unit systems). At 5 gallons per minute, the typical fuel pump is moving 655MJ/minute, or 10.9MW!

So if a thousand cars are trying to recharge at the same time, that is a 109GW load.  The largest nuclear generating station in the United States, currently the Palo Verde Nuclear Generating Station, is rated at 3.2GW. (Why nuclear? Because all of the other significant power generation methods use fossil fuels which essentially just move the problem, not solve it. Solar is not yet ready for prime time.)  A thousand cars refueling at the same time in a major city would not be unusual.

Let’s look at it another way,  current US gasoline consumption is 390 million gallons per day.  Assume that the vast majority of that gasoline is used for transportation.  The energy content of gasoline, again is 131MJ/gal., which equates to 51,090,000 GJ/day,  or 591 GW of continuous power usage.  That is 184 Palo Verde sized nuclear power plants.

This naïve analysis doesn’t take into account any efficiency gains from using electric cars, so let’s do that.  Assume that the average car is on 20% efficient, so 80% of the energy content in the gasoline is wasted.  And for the sake of argument let’s say electric cars are 100% efficient.  That means we only need one fifth as much electrical power to replace the gasoline.  So we only have to build 36 new Palo Verde size plants.

So is there an alternative?  No.

Another popular alternative fuel proposed for transportation is hydrogen.  Many breathless articles have been written about hydrogen fuel celled cars like Honda’s FCX Clarity. They completely ignore the question “where does the hydrogen come from?”

Let’s ignore the considerable question of hydrogen distribution, getting the gas to the end user, and stick with actually obtaining the hydrogen in usable form.  Hydrogen is most easily obtained by electrolyzing water, splitting the H2O into it’s component parts. That requires electricity, a good estimate of how much generating capacity would need to be dedicated to producing hydrogen gas can be found above. But that again ignores the inefficiencies in the electrolysis process itself.

If we want to move away from petroleum fuels (regardless of which country straddles the oil deposit) we need to start building generating capacity right now. By the time the generating capacity is in place, maybe we will have cracked the energy storage problem (hydrogen or electrochemical storage) problems that are at the forefront of most research now.

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5 Responses to Power Plants: Build, Baby, Build…

  1. cha says:

    The battery only drives for 100 miles so it contents is what? 5 gallons of gas max. So it is 1 minute of 655MJ/minute. A 1000 cars is max 10.9GW for a minute so around 300 cars per minute per Palo Verde x 60 minutes = 18000 cars an hour fueled by Palo Verde

    You also forget to mention wind which is a significant powersource which is even cheaper than natural gas per Joule

  2. enderw88 says:

    You are correct about currently conceived “range extended EV” like the vaporous Chevy Volt. I am analyzing what it would take to support a hypothetical EV that actually functions as a drop in replacement for a current petrol powered car. Same range between charges, and the same time to recharge, both characteristics are completely outside the currently foreseeable EV technology. But a power plant take years to decades from concept to on line, regardless of the underlying power source (nuclear, solar, coal, etc).

    I did not forget to mention wind, or other solar sources (wind is a form of solar, the sun drives the weather). I dismiss any power source that is not capable of supplying base load. Until we solve the energy storage problem on very large scales (at night or when the wind isn’t blowing) wind, or any other solar based power supply will not be truly viable sources of base load supply. The amount of power consumed by our current transportation infrastructure is of the same magnitude as our purely electric consumption, so adding non-base load support will not help the situation.

    The only non-solar forms of power currently conceivable are nuclear fission, geothermal, tidal and petroleum based. Wind, hydroelectric, solar thermal and solar photovoltaic are all solar…

  3. cha says:

    Natural gas fired power plants are to expensive to supply base load so i guess you dismiss them too. And solar and peak load are so coupled that i don’t see a problem. There is also the fact that wind is the perfect cheap match when the batteries are big enough for a few hunderd miles because than you don’t have to fill them up to capacity. There is also the issue that in that case you don’t need the quick fueling

    If you claim that hydroelectric is solar than petroleum based is also solar, only a bit older.

  4. enderw88 says:

    The point to EV is to reduce carbon emissions. Otherwise you may as well just stay petrol, that is why I dismiss Natural Gas.

    Remember I am analyzing replacing the petrol powered car, which means a vehicle that can conveniently do 500-600 miles days, limited by driver endurance, not charge rate of the battery. In the western United States it is not unusual to have that requirement, not for everyday usage, but frequently enough to make it a deal breaker if the vehicle can’t do it. So wind negating recharge rates doesn’t really make sense.

    Yes, petrol could be concentrated solar if you subscribe to that particular theory. But the point is carbon reduction. So look at NON-carbon power sources.

  5. cha says:

    EV is a possible future of the automobile. Not only as a power source but also as a form of transmission. If you say that in 20 years all cars will have an ICE coupled with a generator and electric powered wheels but with less battery capacity than a Prius than that is believable to me.

    There is also the issue that oil is hard to get enough of while coal isn’t. It is true that you can convert coal into gasoline but EV is also a solution.

    Carbon emissions are a problem but my fate in humanity is not so great. I doubt that we will even try to solve.

    I wasn’t talking about concentrated solar but the fact that human society uses more of it electricity during the day than during the night

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