Monday, December 22, 2014

Comparing Aviation and Nuclear Power's Safety Record for 2014

It often seems like people zero in on the dangers of certain things while largely ignoring the dangers of others.  For example commercial airlines.  People are often more afraid of flying then they are of driving, and if they've been watching the news this year they would probably feel justified in their fears as this year has seen news story after news story about downed and missing airliners, but things are not always as they appear to be.   In 2014 761 people died on commercial airlines world wide while a staggering 33,783 people died in automotive accidents in the US alone.  Things can look a lot different when you compare statistic than they do when you just go by gut feeling, or what makes the news more often.  Often people consider nuclear power to be dangerous.  Far more dangerous then flying, but I wonder if that's really the case.  That's why I'd like to try and compare Aviation and Nuclear Power safety record for 2014.

Accidental Deaths 

The first comparison is talking about the number of people directly killed as a result of the different activities.  This comparison doesn't deal with radiation.  That's up next. 

Well we got 761 death for commercial aviation.

Nuclear Power
Three people died in and industrial accident while constructing a nuclear reactor.  They most likely died of asphyxiation from breath pure nitrogen gas.  Nitrogen gas is sometimes used in construction

761 is much larger then 3.  Point 1 goes to nuclear.

Radiation Exposure 

This section is for comparing radiation exposures between the two activities.  Some useful information: 1,000 nSv = 1 µSv,  1,000 µSv = 1 mSv, and 1,000 mSv = 1Sv.  Sv stands for Sievert which is a unit used to measure the effect of low levels of ionizing radiation on the human body

Lets start with commercial aviation.  On commercial airlines people are exposed to higher the normal levels of ionizing radiation because of their altitude.  Basically there's ionizing radiation coming from space (i.e. cosmic radiation).  A lot of it gets blocked by our atmosphere, but not all of it, and when you higher you receive large doses (also being closer to the equator gets you higher dosages).  So lets try and calculating how much radiation exposure results from air traffic.

According to the FAA Revenue Passenger Miles (An RPM represents one paying passenger travelling one mile) where 815 billion in 2011 and expected to be 1.57 trillion in 2032.  That's as close as I could get to 2014 with my Google skills, but It probably hasn't changed that much in three years so I'll just go with it. I couldn’t find information on total hours passenger spent travelled so but a commercial jet travels between 500 to 900 km/hr.  With that and a little math we get 1.46 to 2.62 billion total hours flown by paying customers in 2011, and a projected 2.81 to 5.05 billion total hours flown by paying customers in 2032. 

That is a lot of hours. Next lets look at what people are exposed to during those hours. The amount of radiation people are exposed to during flight depends on both altitude and latitude, so in order to get a better idea of the rate of exposure people can reasonably expect during commercial flights lets look at some data taken from Xinjiang Airlines.

Feng YJ, Chen WR, Sun TP, Duan SY, Jia BS, Zhang HL. Estimated cosmic radiation doses for flight personnel. Space Med Med Eng 15(4):265–269; 2002.
  • The average effective dose rate of all flights of Xinjiang Airlines from 1997 to 1999 was 2.38 µSv h-1.
  • The average annual cosmic radiation dose for flight personnel was 2.19 mSv.
  • Annual individual doses of all monitored flight personnel are well below the limit of 20 mSv y-1 recommended by the International Commission on Radiological Protection (ICRP).
Now we need to know the average world wide natural background radiation so we know how much more people get while flying.  Using Wikipedia I got this 0.27 µSv/h (Derived from 2.4 mSv a year) So with a bit of subtraction I get 2.11µSv/h (2.38 - 0.27 = 2.11) more radiation from flying.  Using this we have 1.46 Gh to 2.62 Gh times 2.11 µSv which equals 3,100 Sv (3,080,600,000 µSv) to 5,500 Sv (5,528,200,000 µSv).  If you applied Linear No-Threshold Model to that it would equal 155 to 275 extra cases of cancer for one year of commercial flight, projected to almost double by 2032.  To put that number in perspective this study estimates a total of 130 fatal cancers as a result of the Fukushima nuclear accident.  Though some people contest the validity of applying the Linear No-Threshold Model to low levels of exposure. 

I looked for information about military aviation exposure, but couldn't find anything so I'll leave that out.  I'm also leaving out commercial pilots.  They fly aircraft for other reasons, such as charter flights, rescue operations, firefighting, aerial photography, and aerial application, also known as crop dusting.  I have no clue what kinds of does they get.  For things like crop dusting I'm guessing not a lot. 

For information about flight attendants and pilot.  I was able to get some employment numbers.  There were  84,800 jobs for flight attendants, and for airline pilots there were  66,760 (104,100 - 37,340 = 66,760) job.  From the study quoted above we get 2.19 mSv does for flight personnel each year so that adds another 330 Sv (331916.4 mSv = 2.19 mSv (66760+84800)). 

Next lets talk about space.  Do to the lack of atmosphere astronauts get higher dosage than most professions do.  So lets try and calculate that.  The international space station has six crew spots and they've been filled all year round.  I've found this information about their doses.

The green line is the one that matters to us.

The number on the left are for annual mSv.  The number one the bottoms describe aluminium shielding with 0 being zero shielding and 100 being the most shielding.  Looking at the green line, at solar minimum it looks like they get up to 225 mSv  unshielded, and down to around 75 mSv shielded by aluminium.  I'm just going to assume they're shielded most of the time and call it 100 mSv a year.  There are 6 people on the station all year round so we end up with 600 mSv.

All together for aviation 2014 we get between 3,430.6 Sv to 5,830.6 Sv.  There are a lot of things I've left out like solar particle events, but given my limited resources and waning patience this will have to do.

Nuclear Power  
When you think nuclear and radiation the first thing on a lot of people's minds these days seems to be Fukushima.   So I did some searching and found one map that shows up to date radiation readings, and the other map shows the current evacuated areas.  Here are the two maps side by side at roughly the same scale (I think).

I find these maps rather interesting in light of what I've learned about aviation.   Consider 2.38 µSv/h the the average does for airlines that I used above.   If I wrote this like the radiation readings map it would be 2,380 nSv/h, and would be accompanied by an ominous red dot.  It becomes even more interesting when you consider that 2.38 is just an average. Depending on the type of flight exposure can be much higher.  From an earlier link
Friedberg W, Copeland K, Duke FE, O'Brien K 3rd, Darden EB Jr. Radiation exposure during air travel: Guidance provided by the FAA for air carrier crews. Health Phys 79(5):591–595; 2000.
  • Seattle to Portland: 0.03 mSv per 100 block hours
  • New York to Chicago: 0.39 mSv per 100 block hours
  • Los Angeles to Honolulu: 0.26 mSv per 100 block hours
  • London to New York: 0.51 mSv per 100 block hours
  • Athens to New York: 0.63 mSv per 100 block hours
  • Tokyo to New York: 0.55 mSv per 100 block hours
On the first map a flight from Athens to New York would be listed as 6,300 nSv/h. Furthermore the space station data from Nasa would get purple dots with the heights level of shielding getting 8,560 nSv/h, and no shielding getting 25,700(much higher than anything on the Fukushima map). I find it ironic that people can get on a plane and travel halfway around the world, or even go to space, while thousands of Japanese people aren't even allowed to travel the handful of miles needed to see their own homes.

Unfortunately while this investigation was interesting to me it didn't really give me an idea of what doses people are getting because of Fukushima. I was starting to worry that I would ever get the information I need but luckily Wikipedia came to my rescue again (The same page even). From that article I got an average of 0.0002 mSv a year exposure worldwide. Knowing that there are around 7.3 billion people on earth we can do a little math and get 1,460 Sv ((7,300,000,000 * .0002)/1000 = 1,460) a year exposure from nuclear power.

With between between 3,430.6 Sv to 5,830.6 Sv. from aviation  and 1,460 Sv from nuclear power.  Point 2 goes to nuclear. What an upset victory! 

Terrorist Threat

Terrorist threats are on a lot of people minds these day.  People keep worrying about what they might be up to next. So the question this time is what is more vulnerable to terrorist attacks.  Nuclear power plants or aviation.  Something like this is really hard to put a number on.  Luckily Wikipedia came to my rescue again with the List of terrorist incidents in 2014.  I'm just going to add up all the ones that had to do with nuclear power or aviation.  The one that gets the least wins.

Aviation has a bit of history of terrorism with the whole Twin Towers thing.  Lets see how it fared this year. 

Car bomb
A remote control car bomb exploded near the international airport in Mogadishu as a convoy of U.N vehicles traveled by, damaging one of the U.N vehicles, killing seven Somali civilians and injuring 15 civilians and four security guards. No U.N. Somali or International staff were injured or killed in the terrorist attack.[68][69]
Al Shabab
14 (+10 terrorists)
Gunmen stormed Jinnah International Airport, killing 24 people and injuring 14 others.[160]
Taliban fighters fired eight rockets at a Jalalabad NATO air base. No casualties or property damage were reported.[181]
Suicide bombing, shootout, raid
Assailants conducted a series of attacks in the Seiyun, Yemen. In one attack a suicide bomber drove an explosive-laden vehicle into the entrance of an army base, killing four soldiers. In another attack, non-state militants attempted to raid Seiyun's airport, killing two soldiers. The government killed four militants in order to regain control of the airport. In another attack, a civilian woman was killed by an agricultural plant.[19

Nuclear Power

There wasn't any.


Nuclear wins again.  There are a lot of things about airports that make them good targets.  For example lots of people going in and out leaving holes in security.  Also, they often exist in places that have a lot of terrorists making them conveniently located targets for them to lash out at the 'evil' foreigners.  

The Dangers of War   

I'm not really sure that this is comparison is really needed, but people often argue that nuclear power is a nuclear weapons proliferation threat so I figured I better at least mention it.  My own view is that technical advancement of any kind is a nuclear proliferation threat.  If you want to keep someone from getting nuclear weapons you have to basically keep them down so that they can not make anything that can threaten you.  Such a practice is unethical in my opinion, and counter productive because poor miserable people are more likely to be violent.  Really instead of holding some people down I think we should bring everyone up so that we can all enjoy the fruits of technological progress together.  Then I think the world would be a much safer friendlier place.  In the end I declare this category a tie because I can not quantify this in any way that I find meaningful.

Final Conclusion

Nuclear wins!

Whether or not this article changes your mind about anything I hope you enjoyed it, and it at least made you think. 



Thursday, January 2, 2014

The Hidden Costs of Wind and Solar: Part II intermittency (i.e. variability)

Wind and solar are intermittent (i.e. The wind isn't always blowing and the sun isn’t always shining).  This creates costs that need to be accounted for properly.

Lets start by talking about the electric grid sense understand it is important for understanding the issues with intermittency.  With the electric grids the amount of electric power produced always needs to equal the amount used.  Matching production and use with uncontrollable and difficult to predict sources like wind and solar can be tricky. Things like clouds and changes in wind speed can cause problems.  One way of understanding this problem is to think of the electric like a giant bucket.

"The Western Grid is like a giant bucket," said Mark Avery, SRP's grid manager "with a bunch of spouts running in and out, and you have to keep the water level constant." The Denver Post

Picturing the electric grid as a giant bucket. Some people are taking cups of water (electric power) and pouring them into the bucket while others are taking cups of water out of the bucket. If the bucket become empty it’s bad because people can’t get their water, and it’s also bad if the bucket gets too much water and starts overflowing. The water in the bucket isn't very deep (just enough for someone to get a cup full) so the rate of the water going into the bucket has to precisely match the rate of the water coming out of the bucket. If there is only one person drawing water from the bucket this can be difficult to do. One person is fairly unpredictable. What if he all the sudden decides he wants a lot of water, or what if he all the sudden decides he doesn't need any for a while. This makes load following (i.e. making sure the right level of water is always present) more difficult and less efficient.  Lucky the actions of a lot of people average out into something much easier to predict. So in order to deal with the problem they made the buck wider (but still just as deep) so many people can draw out their cups of water at once.

This system worked well enough (most of the time). Then one day some new people (i.e. wind and solar advocates) decided that they wanted to put their cups of water into the bucket as well, but other people didn't want them to because they couldn't control when they put the water into the bucket, and because they also couldn't predict it with perfect accuracy. The new people said it would be fine, and that just like with people taking water out of the bucket things would become more predictable if they just made the buck wider so more people could put their cups of water into the bucket at once. Then once things became predictable the people that could control the rate they put water into the bucket would help match everything up.

So how well does this new way work?  Opinions vary, but personally I am very sceptical that adding different types of unpredictability together will somehow make things more manageable. One thing’s for certain, the electric grid is not really a bucket. It is an expensive complex machine, and making it do what the renewable energy advocates want makes it even more complex and expensive. I think that’s why they are always saying things like “we need to upgrade our archaic electric grid” or “we need a smart grid”. Sure the electric grid (just like roads) needs maintenance, occasion expansions and even upgrades; but I believe that the biggest reason they are pushing so hard is because they want the money needed to integrate more solar pv and wind without having to included that money in the costs of those technologies.

So what happens when things don't match up?  Well larger difference cause Power outages while smaller differences cause other power quality issues.  Both of these things have costs.   A Berkeley Lab Study estimates that power interruptions cost the US $80 Billion annually.

Lets talk a little bit more about power quality.   What is power quality?  Opinions vary but here is one definition I found useful.

"Power quality is simply the interaction of electrical power with electrical equipment. If electrical equipment operates correctly and reliably without being damaged or stressed, we would say that the electrical power is of good quality. On the other hand, if the electrical equipment malfunctions, is unreliable, or is damaged during normal usage, we would suspect that the power quality is poor."

We have standard for voltage, frequency and phase.  Then we make devices that run off those standards.  If the power difference to much from the standard then devices won't work properly or they can even be damaged.  Both Solar pv and wind can cause power quality issues (e.g. can deregulate line voltages and sometimes in extreme circumstances even shifting the line phase ).  Google the words wind and solar along with power quality and you can learn about the various issues and proposed solutions, or you can watch this video (I highly recommended it).  There are sighs Germany is already having problems  with it’s level of penetration.
"short interruptions in the grid has increased by 29 per cent in the past three years – resulting in some firms on the grid reporting damage running into hundreds of thousands of euros as a result of unexpected stoppages."
Manufacturing requires good power quality which solar/wind can have trouble supplying. This is especially true for manufacturing high tech things like solar panels. There have been attempts to deal with the problem with things like battery back up at the source, but there are still signs that large amounts of wind and solar can cause problems.  In order to cope with these problems  manufactures need to spend money on special systems (for example system that use battery backup), but such things have costs.  However the problem is dealt with (e.g. at the source, smart grids and/or making the end users deal with it) there are costs that should be included in the price of wind and solar.

The variability of wind and solar means that other types of energy generation have to ramp up and down more often in order to match electric production with use.   This creates inefficiencies which have costs that should be attributed to wind and solar.

A good way to understand these inefficiencies is to compare electric generation to something  most people are familiar with.   Cars are more efficient when they are driven a certain way.  For example.
"While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 50 mph."
Power plants also have an optimal fuel economy when operated at a certain continuous output.   They call plants made to operate at their optimal fuel economy Base load Power Plants and anything that causes them to very from their continuous optimal output  creates inefficiencies that have costs.  Some of that cost should be attributed to wind and solar (The rest of it should be attributed to things like changing demand).

It's important to note that power plant not operating at their optimal output because they are being used for load following(i.e. being used to help match electric production with use) are performing a service for the gird.  This service is called spinning reserve and studies have been conducted to try and estimate how much it costs.  One such study is quoted below.

"An expected finding from case studies made to date is that the specific cost of power generated in spinning reserve mode is quite high compared to the optimum cost of power from the same unit. This is, of course, due to the poor heat rate of most thermal power units at low load. If the unit could have operated at high load instead of spinning reserve, there is a lost opportunity cost which may double the cost of the spinning reserve service."

Next is another comparison between cars and power plants.

"Idling can use a quarter to a half gallon of fuel per hour, depending on engine size and air conditioner (AC) use. Turn off your engine when your vehicle is parked. It only takes a few seconds worth of fuel to restart your vehicle. Turning your engine on and off excessively, however, may increase starter wear."

Unlike internal combustion engines base load power plants can't start up that easily (Some can take more than 12 hours to reach full load).  How long it takes to start a base load power plant varies based on numerous factors.  One such factor is how hot it is.  Cold starts take the longest while warm and hot starts take less time.  Trying to get the plant online too fast can result in unnecessary plant failure or wear.  This bring us to another cost that is increased by intermittency.    Intermittency increases Power Plant Cycling Costs.   Power Plant Cycling Costs are the increased costs of maintenance and forced outages caused by things like turning the plant on/off, load following, and minimum load operation, in response to changes in system load requirements.  There are ways to reduce these costs like keeping the plants hot, but such things also have costs.

Another costs of intermittency is as the cost of underutilized capital assets.  A good example of an underutilized capital asset would be a power plant that only runs a few month out of the year when its too cloudy for solar pv, or a transmission line going to a wind farm that has to be build to handle that wind farm’s maximum capacity even though on average the wind farm only delivers 30 percent of that.  Here is a good example of the problem from Germany.

As you can see there are days in January with almost no wind or solar production.   The question you might be asking yourself is how do they get power when wind and solar aren't there for them.  What happens is that people end up having to have two power systems.  The conventional power system (mostly coal in Germany) which is able to meat all of the countries needs plus an extra wind and solar system which can't be relied upon.   Both of these systems have to be paid for which as you can imagination is quit costly.   A lot of people seem to think that some costs don’t count, but if people want to continue to enjoy electricity on demand 24/7/365 then they do count and they need to get paid.

In conclusion there are reasons why electric prices are higher in places that embrace solar and wind.  The sticker price they show you isn't even close to all that you'll have to fork out.  This shouldn't be allowed to go on.  There need to be a better accounting of the true costs of producing electricity with different methods.  Some people have already started on it, but a lot more work need to be done.

Update Mar 4 2015:  Made some changes on things I didn't like.