Texas Electricity – Trying to Understand the Blackouts
Posted on February 4, 2011 by gailtheactuary
Cold weather affects both natural gas supply and electricity. Furthermore, a shortage of natural gas can interrupt electricity supply, and vice versa.
Today, three days after the winter storm hit Texas, electrical outages are still continuing in parts of Texas. We don’t have all the answers yet, but let me tell you what I have pieced together about what has happened. I also offer a few thoughts about how these outages should affect our planning for other natural gas uses, such as back-up to greater wind capacity, or natural gas for vehicles.
Cold Affected Electricity Supplies
Cold weather had direct impacts on electricity production. In the Globe Newswire, we read that frozen pipes in two inadequately weatherized coal-fired power plants were the immediate cause of the crisis. Coal fired power plants tend to be large. Taking two of them off-line simultaneously can be disruptive in and of itself.
There were other weather-related issues. According to the Star-Telegram,
Trip Doggett, president and CEO of ERCOT, said there was no one reason that power failed Wednesday at 50 electrical generating plants. Instead, he said, there were a variety of reasons and no pattern emerged either geographically or by provider. Frozen pipes, valves and monitoring systems were just some of the reasons, he said.
Cold Affected Natural Gas Supplies
Newly pumped natural gas supplies lower
Cold weather affected the amount of natural gas extracted. Platts reports:
US production for Thursday’ gas day would be about 57.5 Bcf, Bentek said, down from more than 62 Bcf a week ago — before the emergence of the cold front that left a large swath of the US with snow on the ground.
“There’s a pretty sizeable amount. The cold has shown a large effect in more than just Texas. We are seeing freeze-offs or lower production in the Rockies, the Anadarko [field] in Texas and Oklahoma, East Texas and the Texas Gulf Coast,” senior Bentek analyst Matt Marshall said.
Freeze-offs occur when low temperatures crystallize the small amounts of water produced with natural gas, forcing blockages at the wellhead, and are most common in extreme and prolonged cold snaps.
Platts also says, “Much of the production loss was centered around Texas, where more than 2 Bcf was lost, according to Bentek data.”
Stored natural gas supplies didn’t give enough “boost”
Normally, natural gas supplies come from a combination of natural gas that is just now being stored, plus natural gas that has been set aside in storage during the time of year when demand was low. But the amount that is available from storage hasn’t been enough, since many states are now reporting low supply.
There are really two different functions that natural gas from storage can provide (1) to add to total supply, as long as there is natural gas in storage and (2) to supplement daily needed amounts. It is clear that storage is not adequate for supplementing daily needed amounts, even though the caverns may appear to have plenty left in them. This is an issue of the “size of the tap” versus the “size of the tank”. It doesn’t matter if a natural gas tank is full, if users can’t get much out on a daily basis.
Natural gas storage is expensive, and is normally only done where naturally occurring caverns can be adapted for this use. No one would seem to have economic incentive to create gas storage if it will only be needed very rarely, and of course, adding such storage would add to the overall cost of natural gas. I don’t know the details of US natural gas storage. It may that to provide adequate short-term supplementation, one would need more, smaller storage locations, closer to where supplementation is needed.
Everybody using the same natural gas
There are multiple users for natural gas:
Homes heating with natural gas,
Businesses heating and cooking with natural gas,
Industrial users other than electricity users, who use electricity in their processes, and
Electricity users.
Of course, all of the gas for these many types of users flows together through the same pipelines, until at the very end, when it goes to its individual destination. When it gets cold out, at least three of the four users listed above are likely to have rising demand for natural gas: people heating their homes with natural gas need more gas for heat; businesses heating their establishments need more gas; and electric power plants need more gas.
One of the questions that comes up is whether the pipelines are of sufficient size to accommodate all of this demand simultaneously. Each new user plugs in, assuming that there will be enough. And there is, until it gets cold out. (We have been told that wind actually performed well during the initial day of the storm. If this had not been the case, the electricity shortfall would have been even worse.) It seems like adequacy of pipeline size should be something that is analyzed.
According to the Star-Telegram,
Fraser said that when several coal-fired electricity plants failed, providers turned to natural-gas-fired plants to fill the gap.
Except that didn’t work because Atmos had curtailed its supply of natural gas to industrial customers, including natural-gas-fired power plants, he said. Atmos did exactly as its protocol called for, he said, to make sure that residential and commercial users had enough gas pressure.
“We didn’t have enough gas pressure available to bring up the power plants,” Fraser said. “In a high-volume usage, the first ones they cut off are the power plants.”
This quirk in the system was unknown to Fraser and perhaps others in state government, probably because no winter storm had so taxed both the electricity grid and the natural gas supply.
So cutting off the electrical providers at the same time as other industrial users when there isn’t enough to go around is a problem that needs to be looked at. The Northeast had a similar conflict between homeowners and electric power plants during cold weather in 2004, according to the Wall Street Journal, and made change to permit electricity generators to be able to request more supply.
Short Natural Gas Supply Reduces Ability to Make Electricity
This is one of my arrows on the diagram at the top of the post. Pretty clearly, if natural gas pressure in pipelines is low, gas-fired electricity cannot be brought up, and this is a problem.
Lack of Electricity Affects Natural Gas Supply
This is my arrow going the other direction. When there are electricity outages, then natural gas pipelines that use electricity to pressurize their gas lose this ability, tending to put even more electric power plants out of commission. According to the Wall Street Journal,
Some natural-gas pipelines were unable to move gas to power plants because they had lost electricity and “they didn’t have a backup system to pressure the lines,” said State Sen. Troy Fraser, chairman of the Natural Resources Committee, who plans to hold hearings on the incident.
I don’t know about the feasibility of retrofitting natural gas pipelines to have natural gas as a back-up to electricity for pressurizing their supplies. It would seem like adding this option would be easier on new pipelines.
With arrows going both ways between natural gas supply and electricity supply, there is clearly a potential for escalation, through an unintended feedback loop.
Where does all of this leave us?
The natural gas system is very complex, as is the electrical system. As energy supplies become tighter, the temptation is to keep adding on to each of these systems, and hope that everything will continue to work together well. And it probably will, as long as conditions don’t occur that stress the system. We have now found out what cold will do, but there are other stressors too, that haven’t been tested yet–adding a huge amount of wind, or adding quite a few transportation vehicles. The stressor might even be something we haven’t even considered.
Analysts considering a new use for natural gas or electricity build models of what they expect to happen, but I expect most assume that everyone else’s pieces will work–the pipelines are big enough, and natural gas supply will be there when needed. The problem is that without real-life testing, we really don’t know how the system will work when it starts reaching its limits. For example, we have built a huge number of “peak demand” natural gas electrical generating units, but I doubt that anyone has really tested running them simultaneously, especially when the weather is very warm, which is one time when we are likely to need them.
Faced with the problem of rolling blackouts, one solution is to try to add on all of the things required to prevent outages, regardless of cost. It is quite possible that this will mean significantly higher electricity costs and natural gas costs, though.
Another solution is to decide that with our energy limits, we no longer can build to handle every contingency. We may have to learn to live with more frequent electrical outages because we are reaching energy limits. We can fix little things (like not cutting off natural gas to power plants whenever other industrial users are cut), but if the cost of other changes is prohibitive, we may just have to live with outages during extreme weather situations.
There are many papers being published that would suggest that natural gas use can be ramped up. Some of these advocate ramping up wind production with natural gas as backup; other consider using natural gas for vehicles. It seems to me that we either need to go slowly in these directions, so we can make course corrections, as we discover that we are overstepping limits, or we need to do very careful modeling of interaction effects, so that we can anticipate problems before they happen. The Texas Electricity situation demonstrates what can happen when not all of the interactions have been considered.
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