Materials development can also play a significant role in the transmission and storage of power. Nearly 10% of the power generated at the source is lost in transmission to the end-user. Stated another way, the power generation base must be approximately 10% larger in order to overcome the losses. Material improvements that reduce these losses would be the equivalent of building new construction, which translates to about 100 GW of installed capacity.
Superconductivity offers one pathway to minimize energy losses through resistive heating in a metal or conductor. While we've known about the superconductivity effects in metals since its discovery in 1911, we've not been able to expand this understanding much beyond the laboratory. Initially superconductivity was only found at temperatures below 30 K, a temperature that required liquefied hydrogen or helium to reach. It was not until 1986 that superconductivity was observed in the laboratory at 77 K, making it practical to use liquid nitrogen as a coolant. It would be 1993 before that temperature reached 138 K using a ceramic material comprised of thallium, mercury, copper, barium, calcium, and oxygen .
The first superconducting power transmission system was brought on line in 2008 in Long Island, almost a century after the discovery superconductivity. While it was a feat of engineering, so were the costs. For 2,000 ft of conducting cable, $58.5 million in capital was expended or about $30,000 per foot—$154 million per mile. By comparison, the most expensive gas pipeline built in the United States in 2007 was less than $10 million per mile; and the average is typically less then $4 million per mile.
Reducing the thermal losses associated with energy transmission can yield significant gains. As noted previously, the energy loss between the point of generation and use is about 10%, and that translates to about 150 million tonnes of CO2 per year for the US alone. If CO2 were assigned a market value of $50 per tonne, the savings would be equivalent to $7.5 billion. Of course, the thermal losses can never be eliminated, but there is the possibility of reducing the resistive losses, perhaps by 3-4%.
Several years ago, IBM researchers suggested a dual approach to energy and power. Energy, in the form of electricity, would be delivered through a superconducting grid. Power, in the form of hydrogen, would be delivered in the same grid, while it would also be used as a coolant to maintain the superconductivity effect. Currently, a scan of the literature reveals only a limited number of technical papers on this subject. However, such an innovative concept may only find its way to markets when substantial development and deployment have been undertaken .
Materials performance improvements may offer one of the paths forward to reaching high energy density, while at the same time providing high output power. It's expected that in the near term, this could be achieved with a lithium ion battery coupled with a super capacitor (a device that can supply power for very short periods, typically less than 60 s). Successful exploitation of energy storage could result in significant reductions in CO2 emissions due to the increase in efficiency at the point of end-use. Net reductions in CO2 of 25-45% would result using this strategy even if more coal plants were constructed to supply the additional electricity. This is due to the lower efficiency of the gasoline IC engine that could be replaced by more efficient electric motors. To maximize the potential of these candidate approaches, materials improvements for energy storage should focus on:
1. Increasing energy density. Reduction in size and mass of the energy storage device.
2. Use of non-toxic and non-hazardous materials. Some of the current battery designs use acids which are corrosive, and can generate explosive gases. High surface area carbons that can readily oxidize on exposure to air.
3. Operation over a wide range of temperatures. Most battery energy storage devices exhibit rapid performance deterioration below -20°C and above 30°C. Extending these ranges will substantially increase opportunities to improve applications of energy storage devices.
4. Development of hybrid systems: energy storage devices that can offer performance of either a battery or a super-capacitor in a single low cost device.
Materials development will be a center of excellence in developing new technologies that can be used to achieve a combination of increased energy efficiency, high energy density storage, and gas separation without the overwhelming parasitic energy costs of today's solvents.
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