Sunday, October 5, 2008

Batteries and The "Negative Temperature Coefficient of Reactivity"

Batteries

Energy storage costs under Proposition 7. I discussed Ed Ring's analysis of the costs of making the California electrical system 50% renewable by 2025. I mentioned electrical storage which Ring estimated would cost $350,000 per MWh. Ring's estimate struck me as low, because my own check last year had yielded considerably higher figures. Ring's figure was based on a study he did based on sodium-sulphur battery costs. Roger Brown came up with a somewhat higher figure:

NGK Insulators claims that in mass production the price of NAS batteries will drop to U.S. $140/kWh. The round trip efficiency in AC mode is 75%. With a lifetime of 2500 cycles at 100% DOD this adds up to a cost of $140/2500*0.75= $0.075 on top of the cost of primary generation. If private finance capitalism and a rising stock market last forever (or at least during our lifetime, a standard assumption of many posters on this site) then the cost of interest must be added to this number, thus bringing the cost up close to $0.12/kWh.


"Jim from The Energy Blog" reported:
Sorry I missed this announcement on Altair delivering 2 MW of batteries to AES:

January 2, 2008 -- Altair Nanotechnologies, Inc. (Nasdaq: ALTI), a leading manufacturer of safe, high-performance lithium-titanate battery and energy storage products, announced today that it completed on schedule in December the manufacturing of battery packs to be used in a two (2) megawatt energy storage system ordered by the AES Corporation. The $1 million purchase initiated by AES was previously announced in August 2007. Altairnano expects the system to be connected to the grid and tested during the first quarter of 2008.


According to a story in the New York Times, dated September 11, 2007, American Electric Power had contracted to pay NGK Insulators Ltd. of Japan, $27 million for six megawatts of sodium sulfur battery capacity. The price included the cost of substation improvements. The Times story stated that each battery could deliver one megawatt of power for a little more than seven hour. That would yield a cost of $640,000 per MWh of storage capacity. According to a USA Today story, the lifespan of a sodium sulfur battery is expected to run about 15 years.

The "negative temperature coefficient of reactivity"

The term "negative temperature coefficient of reactivity" (NTCR) sounds technical enough to be forbidding to the average person. What it means in a reactor is that as the temperature inside the reactor core goes up, the nuclear reaction decreases. Since increases in the nuclear reaction, increases temperature the nuclear reactions in reactors with NTCR will decrease. Eventually, in a well designed, inherently safe reactor, NTCR will turn the reactor off without any operator intervention.

In a fluid salt reactor the NTCR operates by taking advantages of the rules of nature. As the temperature of the core salts rise, they expand. Thus if the reactor fluid is some variant of the LiF-BeF2-UF4 approach, as core fluid temperature rises the fluid salt mixture expands. Since the size of the core is going to stay the same, some of the salt mixture will be pushed out of the core. that means pushing fissionable uranium out of the core, since the uranium is chemically bonded to the core salt. The less uranium in the core, the less fuel is available, so the nuclear reaction slows down. Eventually before the temperature reaches a dangerous point, so much uranium is forced out of the core that the nuclear reaction will completely stop.

The reactor core can be maintained at this temperature, and indeed some heat will have to be dumped because the nuclear decay of fission products that are dissolved in the core salts will continue to release heat. Decay heat thus must continue to be extracted from the reactor through the heat exchange system to prevent overheating. Thus the salt in the reactor core is held at maximum temperature without any fuel use, and this condition can be maintained for some time.

Liquid salt is an excellent heat storage medium. In fact liquid salts have been proposed as heat storage mediums for solar thermal electrical systems. The heat in the salt can be rapidly and efficiently transfered through a heat exchange system to power generating turbine. The turbines can be generating 100% of their capacity as quickly as they can ramp up to full speed. Thus the LFTR fulfills the basic requirements of peak load electrical generators. Currently natural gas burning turbines, hydro electric systems, and pump storage facilities fulfill the peak generation role. Natural gas systems are cheap to build, but expensive to operate because of the high cost of natural gas. Hydro systems are used to nearly the fullest possible extent already. Pump storage facilities are expensive to build and have limited flexibility, and limited storage capacity. In contrast liquid salt reactors such as the LFTR can be held in reserve, but when needed they can be operated for prolonged periods with very low fuel costs. The question then becomes one of capitol costs. Can the cost of LFTRs be low enough to justify their use as peak power producers?

That question cannot be fully answered until we know what would be the competing peak power production systems, and what would they cost. Some possible peak systems would include thermal solar with heat storage, pump storage, compressed air storage, and natural gas with carbon penalties. Power from the natural gas system would be very expensive, because the power user would be paying in effect a double carbon premium. Thus the lower capitol cost would not be a significant advantage.

Solar thermal with heat storage would be well matched to normal daytime demand, provided its capital costs were competitive. But my power system model is that of Texas, where summer heat waves place extreme peak demands on the power system. Although solar power does have some seasonable flexibility, it is probably not sufficient for the peak demands of Texas summers.

The term "negative temperature coefficient of reactivity" (NTCR) sounds technical enough to be forbidding to the average person. What it means in a reactor is that as the temperature inside the reactor core goes up, the nuclear reaction decreases. Since increases in the nuclear reaction, increases temperature the nuclear reactions in reactors with NTCR will decrease. Eventually, in a well designed, inherently safe reactor, NTCR will turn the reactor off without any operator intervention.

In a fluid salt reactor the NTCR operates by taking advantages of the rules of nature. As the temperature of the core salts rise, they expand. Thus if the reactor fluid is some variant of the LiF-BeF2-UF4 approach, as core fluid temperature rises the fluid salt mixture expands. Since the size of the core is going to stay the same, some of the salt mixture will be pushed out of the core. that means pushing fissionable uranium out of the core, since the uranium is chemically bonded to the core salt. The less uranium in the core, the less fuel is available, so the nuclear reaction slows down. Eventually before the temperature reaches a dangerous point, so much uranium is forced out of the core that the nuclear reaction will completely stop.

The reactor core can be maintained at this temperature, and indeed some heat will have to be dumped because the nuclear decay of fission products that are dissolved in the core salts will continue to release heat. Decay heat thus must continue to be extracted from the reactor through the heat exchange system to prevent overheating. Thus the salt in the reactor core is held at maximum temperature without any fuel use, and this condition can be maintained for some time.

Liquid salt is an excellent heat storage medium. In fact liquid salts have been proposed as heat storage mediums for solar thermal electrical systems. The heat in the salt can be rapidly and efficiently transfered through a heat exchange system to power generating turbine. The turbines can be generating 100% of their capacity as quickly as they can ramp up to full speed. Thus the LFTR fulfills the basic requirements of peak load electrical generators. Currently natural gas burning turbines, hydro electric systems, and pump storage facilities fulfill the peak generation role. Natural gas systems are cheap to build, but expensive to operate because of the high cost of natural gas. Hydro systems are used to nearly the fullest possible extent already. Pump storage facilities are expensive to build and have limited flexibility, and limited storage capacity. And we see that mass storage batteries don't come cheap. In contrast liquid salt reactors such as the LFTR can be held in reserve, but when needed they can be operated for prolonged periods with very low fuel costs. The question then becomes one of capitol costs. Can the cost of LFTRs be low enough to justify their use as peak power producers?

That question cannot be fully answered until we know what would be the competing peak power production systems, and what would they cost. Some possible peak systems would include thermal solar with heat storage, pump storage, compressed air storage, and natural gas with carbon penalties. Power from the natural gas system would be very expensive, because the power user would be paying in effect a double carbon premium. Thus the lower capitol cost would not be a significant advantage.

Solar thermal with heat storage would be well matched to normal daytime demand, provided its capital costs were competitive. But my power system model is that of Texas, where summer heat waves place extreme peak demands on the power system. Although solar power does have some seasonable flexibility, it is probably not sufficient for the peak demands of Texas summers. However, if the cost of a LFTR can be brought in at a low enough cost, the LFTR would be a Jim Dandy load follower-peek power generator.

Let us assume for a moment that we need a system that will assure the delivery of 7 GWh of overnight electricity to run Texas Air Conditioners on summer nights. You can get a battery system for from $3.5 to $4.5 Billion. The batteries will last 15 years. Would it be possible to deliver a LFTR system for $3.5 per GW? If you were a utility which would you prefer?

1 comment:

Warren Heath said...

Eventually Batteries will come down to the $150 to $350 per kwh range. But just for overnight storage of Solar Power – say 16 hrs – that’s 16 X $150-$350 = $2400 to $5600 per kw. A hefty price on top of a >$11,000 per kw power plant, and that’s just for overnight storage. What if its thick, dark cloudy, rainy weather for a week or more. Just doesn’t make sense, it is not economical. Useful only to smooth out power peaks caused by highly fluctuating demand or supply – most typically Wind Turbines.

An even more serious concern about energy storage is in Northern Regions, where most of the energy demand is in winter – for heating – when Solar is lowest, Wind is commonly low and Hydro is lowest. Eventually, with the demise of fossil fuels, most energy will come from Electric Power Plants – whether Nuclear, Hydro, Wind or Solar. This brings up a serious problem of supplying the increased energy demand in the Winter in Northern Areas. Wind & Solar Power would be absolutely terrible for that purpose. Hydro is poor – what’s left – only Nuclear. Unfortunately, it means over-sizing Nuclear Power Plants and Power Transmission or Heat Distribution (with CHP plants), in order to supply the much higher energy requirements of Winter Energy. A major advantage would be small CHP Nuclear Plants like the LFTR, NuScale or Hyperion, which could be located closer to the point of use – thus reducing the cost of over-sizing the Energy Transmission network. Another method would be to use surplus Nuclear Heat & Power in the Spring-Summer-Fall to convert Water plus Waste, Biomass or Atmospheric CO2 to Methanol / DME, which could be used as Transportation Fuels or Winter Fuels in remote locations.

With the lackluster efforts of our politicians to expand Nuclear Energy, the next best thing is a sensible use of what’s left of our fossil fuels. They are still far and away, the best and cheapest way to store energy. We are not using our declining fossil fuel resources sensibly, they should be conserved for energy storage and Chemical applications, most particularly our rapidly depleting Petroleum and Natural Gas. It is SHEER, RECKLESS STUPIDITY to be using Natural Gas for Baseload power. It should be strictly rationed for Peak Power, i.e. for Winter Energy needs in Northern regions, to complement fluctuating Wind and Solar, to supply Liquid Fuels (Methanol/DME) for Transport - where Electricity & Batteries are not practical, and to supply Peak Summer Loads in Southern Regions (when Solar is unable to do so). And in Northern Regions, where NG is needed for Winter Heating, it makes most sense to use Home CHP Solid-Oxide Fuel Cells of about 5-10 kWe, rather than furnaces, to get maximum efficiency out of our precious NG resources - ~90% efficiency vs 53% for NG CC Turbine Power Plants (delivered).

Petroleum should also be conserved, similarly to the NG. However, only a small portion of Petroleum is wasted on Power Generation – but it is wasted needlessly on stupid, inefficient Vehicles. And as such, by-far-and-away batteries, rare earth magnets, and power electronics are of greatest value for EV’s and HEV’s not Wind & Solar installations. Once again, it is PURE IDIOCY to continue to allow this practice, when automobiles can easily be made 60-100 mpg and city vehicles can easily be made electric. The greatest opportunity to reduce unreliable Oil imports, reduce GHG and other emissions and strengthen the economy. See:

Supercar: The tanking of an American dream

The Velozzi 200 mpg Series HEV with Micro-Turbine Engine/Generator

EPA 43% Peak Efficiency Methanol Engine with Low Emissions and a Wide Island of High Efficiency

John Westlund explains how the Government had to pay Detroit to build 60-80 mpg HEVs in the 90’s, which they easily did, and pocketed most of the cash, without offering the vehicles for sale.

And most shipping can be done with Nuclear Power.

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