Of That

Brandt Redd on Education, Technology, Energy, and Trust

15 April 2011

Update: The Cost of Solar Energy

Nearly a year ago I wrote a three-part series on energy. At the time, I calculated a cost of $83.33 per gigajoule for solar power. That compares to $1.42 per gigajoule from nuclear power.

Google is investing $168 million in the Ivanpah Solar Farm in the California Desert. As far as I can tell, the total investment will be approximately $2.068 billion. It will be capable of generating 392 gross megawatts of electricity and should last at least 25 years.

In order to convert these numbers to a cost per gigajoule, we have to make some assumptions. I'll use some very generous ones. The solar array cannot generate energy at night and will only generate peak output for part of the day. Not surprisingly, the California desert location chosen for the Ivanpah project happens to be the most favorable in the entire United States. The approach used with solarvoltaics is to multiply peak output by 6 hours per day in that region. Lower numbers are used in other regions. I'll assume that the Ivanpah project is engineered to collect excess solar energy compared to its peak output and so I'm using an 8 hour multiplier instead of 6. Since a net megawatt figure isn't offered, I'll use assume 100% delivery efficiency and use the gross figure. These, of course, are unrealistically favorable assumptions.

It works out to 392 megawatts * 8 hours * 365 days *  3,600 joules/watt-hour = 4,120,704,000 megajoules/year or 4,120,704 gigajoules per year.

Assuming a lifetime of 25 years, construction cost of $2.068 billion and no maintenance costs we get $2.068 billion / (25 years * 4,120,704 gigajoules / year)  = $20.07 per gigajoule. That's an improvement of four times over my previous calculation for solar power. It starts to approach the $13.89 per gigajoule cost of wind power.

It's a huge improvement over solar panels but this still remains the most expensive way in the world to generate electricity. It's an order of magnitude more expensive than conventional energy sources which have the added advantage of delivering power 24 hours a day regardless of the weather.

I'm glad to see this happening but it won't spark a revolution in energy production.

12 April 2011

Do I Trust the New Airport Scanners? No.

I recently decided that I will refuse to step into the new backscatter and millimeter wave scanners that the TSA has deployed at US airports. So far, this hasn't cost me much. Despite flying six times in the last two weeks I haven't yet provoked the infamous pat-down. So far, I've been able to survey the scene and pick the line that uses the old-school metal detector. That won't work forever, they still pick people randomly from the alternative lines and send them through the megadetector. But it should work for a while because the new scanners are too slow to handle full passenger volume.

According to the TSA, one scan by a backscatter x-ray machine exposes an indivdual to a radiation dose of 0.005 millirem which is equivalent to 0.05 microsievert (µSv). Meanwhile, this extremely helpful chart indicates that the dose is equivalent sleeping one night next to someone, it's 1/20 the dose of eating a banana and it's 1/800 the cosmic ray dose of a cross-country airline flight. Millimeter wave scanners, which are also being deployed, use non-ionizing radiation and should pose even less of a threat.

I'm a fairly scientifically-minded individual. So, why am I taking this seemingly unscientific position? The main answer is because I don't trust the information we've been given. I even have some indicators for this lack of trust. For example, in this blog post, the TSA states, "Backscatter X-ray technology uses X-rays that penetrate clothing, but not skin, to create an image." This is language they've used in other places and it's technically true but it's also misleading. The X-rays that make the image penetrate clothing and bounce off the skin and other materials to reach the detector. But the rest of the X-rays, those that didn't make the image, are absorbed by the body. So, my spontaneous lack of trust is reinforced by the TSA's use of misleading language.

I'm not alone in distrusting government assurances. A recent survey conducted by Xavier University indicates that 78% of Americans have less trust in government than they had 10 years ago. A CNN poll shows that only one in four Americans trusts government to do the right thing most of the time.

But for me to distrust the TSA's explanations, I have to either distrust their intentions or their judgement. The fact is, I distrust both. It turns out that the benefits of the scanners weren't sufficiently convincing until the manufacturers spent millions of dollars lobbying congress and federal agencies for their adoption. And security expert Bruce Schneier says it's all just security theater with no real benefit.

So, I guess my opt out represents a concern that the scientific tests are incomplete combined with a relatively inexpensive form of civil disobedience. But my real hope is that someday government officials will quit trying to convince us they're right and start earning back our trust.

Added 2011-04-13:
My son just sent me a link to a letter written by concerned UCSF scientists. After a little more research I found this response from the FDA. Both parties agree that the absorption by the skin of low-intensity X-Rays results in a disproportionally high dose compared to medical X-Ray systems. In fact, the FDA estimates the effective dose to be 0.56 µSv which is more than 10 times the number reported by the TSA that I used above. That's still a small dose. Where they disagree is on whether sufficient research has been done to establish the safety of these scanners. So, it remains an issue of trust and with all of the misinformation in the TSA statements they just aren't behaving in a trustworthy way.