Carnot efficiency

Twist 1.5, Major's Hill Park, Ottawa

For a bit of light entertainment, I have been reading Tom Rogers’ book Insultingly Stupid Movie Physics, which basically covers the same terrain as his entertaining website, though at greater length and with more detail. Of course, one can never entirely escape climate change related information, and the book includes a discussion of Carnot efficiency: the maximum theoretical efficiency with which heat engines can convert thermal energy into useful power.

The efficiency depends on two factors: the high temperature produced using combustion, solar energy, geothermal energy, etc, and the cold temperature where the heat is expended into the surrounding environment:

Efficiency = ( 1 – Cold temperature / Hot temperature ) * 100

This has implications for technologies like the co-generation of heat and power. If the heat source for a power plant is 375°C (648°K) and it is dumping waste heat into 10°C (283°K) outdoor weather, the Carnot efficiency is about 56.3% (the actual efficiency is lower, for various reasons). If, instead, it is dumping the heat into buildings at 25°C (198°K), the Carnot efficiency falls to 54.0%. In a case where the heat source is just 200°C (473°K), the difference between a 10°C cold area and a 25°C cold area cuts the Carnot efficiency from 40.2% to 37.0%. In many cases, cogeneration is still worthwhile, despite the loss of useful electrical or kinetic energy, but it should be appreciated that the redirection is not without cost.

Carnot efficiency also helps explain why waste heat is not always worth capturing. If the temperature difference between the source and an available destination for the thermal energy is not large, there isn’t much useful power that can be produced.

[Update: 4:47pm] Remember to express the temperatures in Degrees Kelvin, by adding 273.15 to the figure in Degrees Celsius.

Microsoft’s imitation Google

Microsoft’s new Bing search engine is a bit bewildering. To call it an homage to Google is an understatement: complete with ‘Web,’ ‘Images,’ ‘News,’ ‘Maps,’ etc across the top bar. While the bird’s eye feature in Bing Maps is a bit neat (it seems like it might be based on HDR images), one cannot easily shake the feeling that Microsoft decided to respond to Google’s approach by outright copying it. The only oddity is that, because I have my Windows language set to British English (so it knows how to spell ‘colour’), this makes Bing think I am in the UK, and the site offers me no option for showing Canadian results or news. Not very clever, given the ease with which an IP address can be turned into a location.

Has anybody discovered any Bing feature that is either quite different from or better than a Google offering? Hotmail certainly cannot begin to touch the searchable glory that is GMail.

Human rights and climate change

Rabbit near Mud Lake

Over at Grist, there is a discussion about whether human rights are a useful perspective for thinking about climate change, as well as how they might be applied at the legal or institutional level to improve climate change outcomes. For instance, future generations could be appointed guardians within the legal system, in the same way in which children have legal guardians appointed to represent them in court.

The idea is a nice one, but it overlooks the degree to which legal and political decisions largely emerge as the products of political and economic influence, neither of which is possessed by future generations, within today’s political system. As such, these guardians would likely end up unpopular (for trying to block projects that would benefit those living and influential now) and powerless (for the lack of a real constituency to back them).

My general position on human rights is that they do not have moral force in and of themselves – they are just a shorthand way of encouraging good outcomes. For instance, it is the consequences of protecting free speech that make it a moral imperative to do so, not some metaphysical characteristic embedded in human beings. As with other areas of ethical thinking, human rights can be a useful heuristic when dealing with climate change, but what really matters is developing the mechanisms of thinking and action that will prevent the worst possible outcomes, while also seeking to secure the complimentary benefits that could accompany a global transition to carbon neutrality.