Monday, February 27, 2012

A "Nation-Sized Storage Battery" and the Wind Power Delusion

In "How Big a Battery Would it Take to Power the USA?" a recent Scientific American article asks whether the US is ready to be powered by wind and solar. Wind and solar are intermittent energy sources, inherently unreliable.
According to the U.S. Department of Energy, when intermittent sources such as solar or wind reach about 20 percent of a region’s total energy production, balancing supply and demand becomes extremely challenging: rolling blackouts can sometimes become inevitable. The same problem exists elsewhere, notably in Germany, where a vast photovoltaic capacity has sprung up thanks to generous subsidies.

Burton Richter, a physics Nobel laureate who was on a recent panel that studied California's power supply situation, told The New York Times blogger Andrew Revkin that because of intermittency, utilities would need to keep fossil fuel–burning plants as a backup that can quickly ramp up generation as need be. This large-scale load following, as it is called, "can only be done with natural gas," Richter told Revkin. _SciAm
And what if the wind stops blowing for several days in a row? The author speculates on the possibilities of using a giant, nation-sized storage battery to power the entire US national grid. Unfortunately, he does not quantify the speculations, but he does help fuel the undying wind and solar fantasy, if the comments are any judge.

Fortunately, UCSD physicist Tom Murphy has looked at this question quantitatively in "A Nation-Sized Battery." and wind suffer a serious problem in that they are not always available. There are windless days, there are sunless nights, and worst of all, there are windless nights. Obviously, this calls for energy storage, allowing us to collect the energy when we can, and use it when we want.

... We’re not a nation tolerant of power outages. Those big refrigerators can spoil a lot of food when the electricity drops away. A rule of thumb for remote solar installations is that you should design your storage to last for a minimum of three days with no energy input. Even then, sometimes you will “go dark” in the worst storm of the winter.This does not mean literally three days of total deprivation, but could be four consecutive days at 25% average input, so that you only haul in one day’s worth over a four day period, leaving yourself short by three.

So let’s buy ourselves security and design a battery that can last a week without any new inputs (as before, could be 8 days at 12.5% average input, or 10 days at 30% input). This may be able to manage the worst-case “perfect” storm of persistent clouds in the desert Southwest plus weak wind in the Plains.

Let’s also plan ahead and have all of our country’s energy needs met by this system: transportation, heating, industry, etc. The rate at which we currently use energy in all forms in the U.S. is 3 TW. If we transition everything to electricity, we can get by with 2 TW, assuming no growth in demand.

...Running a 2 TW electrified country for 7 days requires 336 billion kWh of storage. We could also use nuclear power as a baseload to offset a significant portion of the need for storage—perhaps chopping the need in two. This post deals with the narrower topic of what it would take to implement a full-scale renewable-energy battery. Scale the result as you see fit.

...Large lead-acid batteries occupy a volume of 0.013 cubic meters (13 liters) per kWh of storage, weigh 25 kg/kWh (55 lb/kWh), and contain about 15 kg of lead per kWh of storage.

How do we put this into more familiar terms? A 12 V battery rated at 200 A-h (amp-hours) of charge capacity stores 2400 W-h (watt-hours: just multiply voltage and charge capacity), or 2.4 kWh. 200 A-h means that the battery could discharge a 10 amp current (120 watts) for 20 hours, or a one amp current (12 watts) for 200 hours—though in actual practice the capacity is lower at higher currents.

I can’t resist the temptation to ask: what is the minimum amount of lead that is theoretically needed to build the battery? The chemical reaction for a lead-acid battery is such that each interaction involving the transformation of one lead atom to PbSO4 liberates one electron at a 2.1-volt potential. This electron then is bestowed 2.1 electron-volts (eV) of energy, amounting to 3.4×10−19 J (see page on energy relations). One kilowatt-hour is 3.6 million Joules (1000 W times 3600 seconds), so that it takes 1025 lead atoms (where every one participates). If you remember that Avogadro’s number is 6×1023, we need about 20 moles of lead atoms. At 207 g/mol, this comes out to about 4 kg per kWh of energy, which is a factor of four less than the realized value above.

...Putting the pieces together, our national battery occupies a volume of 4.4 billion cubic meters, equivalent to a cube 1.6 km (one mile) on a side. The size in itself is not a problem: we’d naturally break up the battery and distribute it around the country. This battery would demand 5 trillion kg (5 billion tons) of lead.

...A USGS report from 2011 reports 80 million tons (Mt) of lead in known reserves worldwide, with 7 Mt in the U.S. A note in the report indicates that the recent demonstration of lead associated with zinc, silver, and copper deposits places the estimated (undiscovered) lead resources of the world at 1.5 billion tons. That’s still not enough to build the battery for the U.S. alone. _Tom Murphy
So we are confronted with "the limits to lead." Not only is such a battery unaffordable, but it is unobtainable. Trying to use any other technology in place of the old standby, lead acid, would make the impossibility of a national battery even worse.

Dreams are wonderful things. But they should not distract us from the things that need to be done. Lefty Luddite dieoff.orgy greens have taken over the governments of much of Europe, North America, and Oceania. Their delusions -- when put into law -- threaten to make it impossible for their societies to achieve an abundant future.

What the residents of those nations choose to do when their power cliques are operating with a destructive and delusional mindset, is up to them.

More: The German government's decision to precipitously close all nuclear power plants, and to rely upon unreliable big wind and big solar for industry-critical power, is creating an economic disaster. More on dealing with intermittency:
The industry is concerned that it isn't clear how the government intends to guarantee the power supply in the future. Pumped-storage hydroelectricity plants would have to be built to store energy for periods when there is little wind or solar energy. But hardly any new facilities are currently in the works. Billions would also have to be invested in reliable power grids so that wind-generated electricity can be transported from the coast to the industrial Ruhr region and to the southern states of Bavaria and Baden-Württemberg. But national and state politicians are still fighting over where the lines should be installed and whether it will be necessary to bury all cables underground. Finally, additional natural gas-fired power plants are urgently needed. Not surprising, however, very few companies are prepared to invest in facilities that may or may not be profitable, depending on which way the political winds happen to be blowing.

...The energy supply is now "the top risk for Germany as a location for business," says Hans Heinrich Driftmann, president of the Association of German Chambers of Industry and Commerce (DIHK). "One has to be concerned in Germany about the cost of electricity," warns European Energy Commissioner Günther Oettinger. And Bernd Kalwa, a member of the general works council at ThyssenKrupp, says heatedly: "Some 5,000 jobs are in jeopardy within our company alone, because an irresponsible energy policy is being pursued in Düsseldorf and Berlin." _Spiegel

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