Bangkok temperature plunges to below freezing!

Sky radiant temperature in Bangkok
 -- surprisingly cool, even on a hot season afternoon.

Believe it or not, the sky temperature the last few days has dropped to 0 deg C or a little below. 

People who write learned papers and books about tropical architecture and comfort --Floridians, Singaporeans, Australians, and, God knows why, even some Norwegians -- talk of "dumping" building heat, ie trying to find places where the enthalpy is low to which unwanted building heat can be efficiently transferred.

Alas, this is not easily done in Thailand because there aren't any cool places to be found. With a mean temp over the year of nearly 28 degrees(82 F), the earth itself is warm -- about 28 degrees, which does not provide much of a "sink" for heat. 


The sky, which cools the overheated brow and the roof in the night desert  is fairly warm in the tropics, except for a few weeks in the low humidity "cool season", and efforts to radiate heat into the sky from buildings are not usually considered to yield much benefit, especially in the hot season.

But since we have recently seen that we are not asking for much cooling, just a few degrees, I've been taking some night sky temperature measurements* with my little Radio Shack radiant thermometer. Here are the results on the graph above. Evidently the night sky temperature is a function of sky moisture, or dew point. And in the hot season, when there is a lot of moisture in the air, the night sky becomes less effective as a heat sink.

But still. How much can we get from a night sky of 15 degrees?

According to radiant heat theory, we should be able to transfer about

k*(Troof^4-Tsky^4) watts/m2
where k= 5.6697xlO-8 w/m2-°K. T

which comes to about 50 to 80 watts per square meter of roof. This is enough to lower the roof temperture, suppress it as we say, by two or three degrees.

The question is, can we use this natural cooling to some good end?
-------------------------------
* I know that this instrument is not really measuring the temperature of anything in the sense of say a thermometer, rather it is feeling how much radiation is being emitted by whatever you point it at. Or whatever you point it's 30 degree "eye" at. It thinks that the emittance of everything is the same, maybe 0.9, which is not true or things like aluminum and skies. But since radiation is what we are talking about here, I'm just going to go ahead and figure the heat transfer as if the "temperature" of the sky was what the radiant thermometer says it is.

Bangkok temperature plunges to below freezing!

Sky radiant temperature in Bangkok
 -- surprisingly cool, even on a hot season afternoon.

Believe it or not, the sky temperature the last few days has dropped to 0 deg C or a little below. 

People who write learned papers and books about tropical architecture and comfort --Floridians, Singaporeans, Australians, and, God knows why, even some Norwegians -- talk of "dumping" building heat, ie trying to find places where the enthalpy is low to which unwanted building heat can be efficiently transferred.

Alas, this is not easily done in Thailand because there aren't any cool places to be found. With a mean temp over the year of nearly 28 degrees(82 F), the earth itself is warm -- about 28 degrees, which does not provide much of a "sink" for heat. 


The sky, which cools the overheated brow and the roof in the night desert  is fairly warm in the tropics, except for a few weeks in the low humidity "cool season", and efforts to radiate heat into the sky from buildings are not usually considered to yield much benefit, especially in the hot season.

But since we have recently seen that we are not asking for much cooling, just a few degrees, I've been taking some night sky temperature measurements* with my little Radio Shack radiant thermometer. Here are the results on the graph above. Evidently the night sky temperature is a function of sky moisture, or dew point. And in the hot season, when there is a lot of moisture in the air, the night sky becomes less effective as a heat sink.

But still. How much can we get from a night sky of 15 degrees?

According to radiant heat theory, we should be able to transfer about

k*(Troof^4-Tsky^4) watts/m2
where k= 5.6697xlO-8 w/m2-°K. T

which comes to about 50 to 80 watts per square meter of roof. This is enough to lower the roof temperture, suppress it as we say, by two or three degrees.

The question is, can we use this natural cooling to some good end?
-------------------------------
* I know that this instrument is not really measuring the temperature of anything in the sense of say a thermometer, rather it is feeling how much radiation is being emitted by whatever you point it at. Or whatever you point it's 30 degree "eye" at. It thinks that the emittance of everything is the same, maybe 0.9, which is not true or things like aluminum and skies. But since radiation is what we are talking about here, I'm just going to go ahead and figure the heat transfer as if the "temperature" of the sky was what the radiant thermometer says it is.

Phaking in Phnom Penh

Chez Gaston, Phnom Penh

Ou-la-la, lovely food and people here in Cambodia where I am spending a few hot bright days in late November. Bright blue sky radiant temperatures are 15 degrees C, but the sun creates a fiery glare that makes it pretty hot along the tree-short (and watershort)  riverside area. My hotel room was catching it on the outside walls with inside wall temps at 33 deg and the sluggish aicon was not keeping up. I asked for another room at the desk but they showed me a great trick instead. Get a castrated room key card and when you go out leave it in the slot by the door so the power and aircon remains on.

Meanwhile the astrologers (?) are predicting worse to come as per the local English language news this morning.

Phaking in Phnom Penh

Chez Gaston, Phnom Penh

Ou-la-la, lovely food and people here in Cambodia where I am spending a few hot bright days in late November. Bright blue sky radiant temperatures are 15 degrees C, but the sun creates a fiery glare that makes it pretty hot along the tree-short (and watershort)  riverside area. My hotel room was catching it on the outside walls with inside wall temps at 33 deg and the sluggish aicon was not keeping up. I asked for another room at the desk but they showed me a great trick instead. Get a castrated room key card and when you go out leave it in the slot by the door so the power and aircon remains on.

Meanwhile the astrologers (?) are predicting worse to come as per the local English language news this morning.

My modest Bangkok electric bill

At about ten cents US per kilowatt hour the electric bill for our condo was less than forty dollars US last month, a cool one. Our hot June bill (750 kw-hrs) was nearly double; even then our nightly use of aircon for a single shaded bedroom amounted to only about $1 extra a day -- not too bad. On the other hand, this would amount to perhaps ten percent of the income of most Thai workers -- making aircon a threshold luxury for them. 

This is also consistent with the observation that aircon amounts to roughly half the electric power use in Bangkok.

My modest Bangkok electric bill

At about ten cents US per kilowatt hour the electric bill for our condo was less than forty dollars US last month, a cool one. Our hot June bill (750 kw-hrs) was nearly double; even then our nightly use of aircon for a single shaded bedroom amounted to only about $1 extra a day -- not too bad. On the other hand, this would amount to perhaps ten percent of the income of most Thai workers -- making aircon a threshold luxury for them. 

This is also consistent with the observation that aircon amounts to roughly half the electric power use in Bangkok.

Air conditioned tents

At Mecca. Sufficient for 3 million people. Used 5 days a year.