Make your aircon work harder for lower humidity

Sleep well: most BKK condo aircons way too big, run small % time with temp=25, add rather than subtract humidity. My neighbor gets lower RH temp= 22 deg, aircon runs near 100%, cuts RH from 75 to 65%, but still a little too high. Big electric bill for this.

Inverter Outperforms Old More Powerful Aircon

Answer to question re power use and effectiveness of inverter v overpowered older aircon split units. On this  warm cloudy Bangkok afternoon my new Mitusbishi uses about the same power as the old Trane with  three times the power rating, but delivers dry air. The Trane begins to cycle on and off when it reaches the set temperature. In the intervening periods with fan but no compressor the Trane blows moisture back out of the concealed wall unit  into the room raising the humidity in the room to higher than outside. It is also much more noisy.

 

Threshold (28-29 deg) of "deadly" days are actually optimum in Thailand

Further to the reported onslaught of "deadly" hot weather in the tropics, I show here a J-shaped plot of Thai Central valley hot season death rate vs. maximum daily temperature. We note that the least deadly temperature is about 33-34. This translates to an average daily temperature of about 28-29. The death rate increases about ten percent when daily Tmax hits the upper 30s. These data are all-age, elder rates reportedly are optimum at lower temps.

When we think that many deaths occur at the end of a long lingering illness we should ask whether hot-weather induced tipping point death should be considered a heat-related death rather than in many cases a benign heat-accelerated death.

And why doesn't anyone mention the threat so close to the heart of most tropical people, namely more frequent cool weather?

The association between temperature and mortality

in tropical middle income Thailand from 1999 to 2008

Benjawan Tawatsupa & Keith Dear & Tord Kjellstrom &

Adrian Sleigh

Global risk of deadly heat Camilo Mora, Bénédicte Dousset, Iain R. Caldwell, Farrah E. Powell, Rollan C. Geronimo, Coral R. Bielecki, Chelsie W. W. Counsell, Bonnie S. Dietrich, Emily T. Johnston, Leo V. Louis, Matthew P. Lucas, Marie M. McKenzie, Alessandra G. Shea, Han Tseng, Thomas W. Giambelluca, Lisa R. Leon, Ed Hawkins & Clay Trauernicht

Nature Climate Change 7, 501–506 (2017) doi:10.1038/nclimate3322

Threshold for "Deadly" days

The Nature paper (referenced last entry) determines the threshold for "deadly" days by sifting through and classifying various reported heat wave events  in places like France and Southern Australia and comparing them to days with "ordinary weather" in the same place, using a classification technique ("support vector machines") that aims to draw boundaries between types of events based on what appear to be discriminatory boundaries between attributes. In this case it is found with only a fair degree of reliability that heat-attributed deaths generally occur on hot days, with a lesser impact from high humidity. Notably unsurprising conclusions.

By picking points from the chart I developed a simple linear relationship (shown above in green) that emulates the "deadly" boundary. It also appeared to me (as an old psychrometrician) that the boundary appeared to correspond fairly well to a wet bulb temperature of about 26, at least when humidities are 70 percent or more, which is usually the case in Bangkok. Given the broad approximations of the method the study dictates that on days with usual hot-season humidity in the tropics the average daily temperature becomes "deadly" at about 29 degrees.

Readers of this blog might recall that this is the temperature where I turn on the bedroom air conditioner at night. Readers who have some experience with wet bulb and global wet bulb temperatures will be aware that military training and sports practice are thermally acceptable at wet bulb temperatures of 26, heading into precautionary modes only above Twb=26.

Global risk of deadly heat: Bangkok compared

Publication of this paper "Global risk of deadly heat" in the prestigious Nature Climate Change journal last week 

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3322.html

has created a considerable stir. It concludes that a deadly increase in tropical health problems is a likely outcome following man-made global warming.

How well does this hold up for Thailand? This question will be examined here starting with this brief entry showing the results of the Nature study (right) compared to recent years including the record (?) 2016 in Bangkok (left).

Following this study, almost all days in the Bangkok hot seasons (March-June) for the past few years would be categorized as "deadly", that is, they are hotter than the red line which is meant to divide various historical heat waves with and without fatalities. With humidity typically 70 percent, it follows from this study which draws from a global database (not specific to Thailand or other tropical regions) that average daily temperatures of higher than about 27 deg should be classified as "deadly". This line also corresponds closely to a wet bulb temperature of 26. Is this suggestive of fatalities? How does this compare with observations here in Thailand over the past few years, both personal and published by local researchers? Or with standards developed for military training and sports internationally?

The hot season broken by moisture

Mid-May dawn: with the coming of rainy and cloudy weather, the back of the hot season seems to be broken, with dawn temperatures below 30 degC (86F) in my downtown neighborhood. At the peak of the hot weather a couple of weeks back they were consistently over 30. 

Notice the 28-30 temps downtown and the 27 or so further out including the Don Muang airport area where our long-term records are. This agrees with my previous study indicating a 2-3 deg "heat island effect" in the Sukhumvit area.

Afternoon Bangkok sun blasts glassy condos

In an earlier post we showed how anyone seeking a "view condo" pays the penalty of terrible heat either in the morning (east facing) or afternoon (west facing). Curtains, blinds, or dark glass don't help much, they just heat up to 50 deg C (130F) and act like ski-cabin radiators. Ugh! Few of us think of this when we buy a condo, we are charmed by views which become minor considerations after we occupy a condo for a few weeks.

Be warned! Air conditioning does not alleviate this radiant heat problem!