carrousel, Wudaokou, Beijing, China

Wudaokou, one of the most dynamic places in Beijing, is a large plate of spaghetti of high-tech like Google China, grassroot internet startups, night clubs, cafes and bars, pirated books, snacks, etc. This carrousel is just a newly added topping to the always pictorial, always fascinating Wudaokou…

Not so long ago, there was a discussion on the environmental impact of Google searches.

An article from Times magazine UK on Jan. 11th, 2009 (Revealed: the environmental impact of Google searches) claimed that 7 grams of carbon dioxide is released for each Google search. The issue of this article was neither did it well define “a search”, nor did it provide any details on how the result was obtained. Very quickly, the official Google blog responded: “Only 0.2 grams of carbon dioxide is released for each search.”, and the link to the blog is here.

Wow, 35 times difference!

In a few days, the Times magazine UK added a note on the 16th, explained that by “one search” they referred to the search of a question, which may result in multiple actual searches. They basically agreed on the 0.2 gram calculated by Google, and added that they also considered the energy consumption of the user’s computer. 1-10 grams of carbon dioxide will be released when an user is doing a search, depending on the time spent and device used. So everything is clear now: Google is doing great, and it’s the users who caused major carbon dioxide release. We all should go back and do some reflections. Let’s see what “green things” we can do to cover damage that our routine searches do to the environment.

It’s been almost half a year, I still think the two numbers are way too different. I think this can be calculated, so I did the following with some assumptions.

All I need to know is the total search counts from Google in a given period of time, and the total energy consumption during this time.

About Google search counts, we know:

1. http://www.marketingvox.com/may-searches-rise-20-to-94-billion-044409/

9.4 billion searches in the US alone in May 2009, grew 20% over May 2008.

2. http://news.bbc.co.uk/2/hi/technology/7039114.stm

37 billion searches worldwide in August 2007.

If we assume the annual growth for the recent 2 years is 20%, then it should grow no more than 30% from August 2007 to January 2009. Let’s assume 30%, then the worldwide searches via Google in January 2009 is:

37 billion * 130% = 48.1 billion times. That’s 1.6 billion times per day, 75 million times per hour (20,000 times per second, that’s very scary!)

To figure out Google’s hourly energy consumption on search, we need to know how many servers there are on search, and energy consumption for each server. Data on these is scarce and outdated, but we can still get some reasonable things out with some bold assumptions.

According to this article on Wikipedia: http://en.wikipedia.org/wiki/Google_platform

Google has about 450,000 servers in 2006. Considering 20% growth on search market, ever-growing numbers of webpages, large amount of other services (Youtube, Picasaweb, Google Map, etc.), the total number of Google servers may have already doubled, even possible to reach 1 million.

Being almost the sole revenue source, search is the core business of Google. We have reason to believe that server needs related to search (spider, indexer, backup, ads, etc.) won’t be a small percentage. Let me suggest 50%, that’s still 450,000 servers.

Google provided some information on their servers in this article (http://news.cnet.com/8301-1001_3-10209580-92.html): 1,160 servers in a standard shipping container with a power consumption of 250 kilowatts. That’s a little over 200 watts per server, which aligns well with our common sense.

450,000 servers will fit in about 400 of such containers, and the total energy consumption per hour is 250 * 400 kilowatt hour = 100,000 kilowatt hour (kWh).

Ok, we are getting there. We need one more data, how much carbon dioxide is released for each kilowatt hour (kWh) produced? And the answer is here: http://answers.yahoo.com/question/index?qid=20080817001636AAgJkka

Actually, amount of carbon dioxide released varies a lot for different types of electricity generation. Obtaining electricity by burning coal (still the major method to get electricity) will release 950 grams of carbon dioxide for each kWh generated, using oil 900 grams, and water power merely 3 grams. If we assume 900 grams, let’s see the result.

75 million Google searches worldwide per hour, consumes 100,000 kWh, and 900 grams of carbon dioxide is released for each kWh generated. For every search, the amount of carbon dioxide release is:

900 * 100,000 / 75,000,000 = 1.2 gram

This only considered the energy consumption of Google server excluding energy consumption by the user, and energy wasted during transfer.

Actually user doesn’t use much energy on search at all. Let’s assume the user’s computer is working at full capacity, energy consumption is 250 watts, that’s 1 kWh for 4 hours, which correspond to 900 grams of carbon dioxide. Therefore, less than 4 grams of carbon dioxide per minute of usage. Within the 0.2 second it takes for Google to return the search result, only 0.013 grams of carbon dioxide is released. None of Google’s servers that serve this search should work for more than 0.2 second, most likely much shorter than 0.2 second. 1.2 gram is almost 100 times more than 0.013 grams, and this matches well with the fact that Google uses hundreds if not a thousand servers to serve one search.

0.2 and 1.2, that’s wholy 6 times! How could this be? There are only a few possibilities:

1. Google uses much less servers on their search business. Is it possible for them to use <10% of their servers on something that generates >90% of the revenue?

2. The majority of the energy used by Google is clean energy, but I highly doubt it.

This actually tells us why Google is so fervent on the investment in clean energy, because they could benefit in big ways directly. The electricity price in the US is at least 10 cents per kWh (http://michaelbluejay.com/electricity/cost.html). The electricity bill for Google each month will be at least:

100,000 kWh (half of the servers for 1 hour) * 2 * 24 * 30 * 0.1 (price) = 14.4 million USD

That’s more than enough for a few early stage projects.

3. There is something wrong in my calculation.

So Mr. Google please, am I wrong?