Reduce heat wave harm with solar air heaters

Humid Heat Waves Will Top Limits of Human Survivability
psmag.com
https://psmag.com/environment/humid-heat-waves-will-top-limits-of-human-survivability 
Heat danger in coming years. But warm humid climates have one advantage - it might easily be possible to create convectional rain, merely by heating the air. Usually the solar energy goes into heating ground and air, but with solar air heaters the ground is prevented from heating because solar air heaters shade the ground. Most of the energy would go into heating the air, so we could have massive convection and rain. The clouds formed would reflect and radiate solar energy back to space. This is especially so with low clouds in low latitudes. See
http://www.builditsolar.com/Experimental/PopCanVsScreen/PopCanVsScreen.htm
on how to build a solar air heater. We could have huge solar air heaters on every roof.
Using Espy's equation shows that with high relative humidity, low clouds form.
H = 125 (T-Tdew), where H is the height of the base of the clouds, where T is the temperature (deg C) of the parcel at near ground level and Tdew is the dew point temperature at near ground level. With high relative humidity Tdew is close to T. The formula gives the altitude of the cloud base in metres.The heated air parcel that we are applying the above formula to is the air heated by the solar air heaters.
Example: The temperature of the air parcel heated by all the solar air heaters is 45 deg C. The dew point is 35.9 deg C.
Then H=125(45-35.9) = 125x9.1=1138 m.
The whole process of causing the rain takes heat away from near the ground and moves it higher up. It also removes water vapour from the air, dehumidifying the air (the water vapour has become water). In the tropical forests the temperature usually stays below 35 deg C or so because evaporation reduces temperatures near the ground.
SOLAR AIR HEATER DESIGN FOR SOLAR UPDRAFT TOWER: 
The present design has a greenhouse at the bottom providing hot air. My concern is that air does not come into intimate contact with hot surfaces with a greenhouse and if the hot air is not transferred quickly, there will be heat losses through the glass of a greenhouse and so on. Air is not heated much by radiation, but it is heated efficiently by direct contact with hot surfaces. I therefore propose that solar air heaters be used for the base of the solar updraft towers, rather than greenhouses. With greater efficiency one would not have to have such a large area (the greenhouse needs a huge area). Also, with solar air heaters, the heaters can be mounted vertically saving huge space. See http://www.builditsolar.com/Experimental/PopCanVsScreen/PopCanVsScreen.htm
Example on air pollution: Kathmandu has an air pollution problem and solar air heaters could be used to cause convection and dilute the air pollution. Kathmandu, in winter, has about 4.2 kWh of solar energy falling on every square metre in a day. Because of a fairly high altitude, the air pressure is about 87 kPa (instead of 101.325 kPa). With a temperature of 25 deg C, 4.2 kWh could heat 2954 cubic metres of this low pressure air by 5 deg C. If a one square metre solar air heater was 50% efficient, it could heat 1477 cubic metres of air by 5 deg C every day. In summer Kathmandu has about 7.6 kWh of solar energy falling on every square metre every day.
VOLUMETRIC HEAT CAPACITY OF AIR: I had a hard time finding figures for the volumetric heat capacity of air. They will be useful for calculating how many cubic metres of air at a certain temperature and pressure of 101.325 can be heated by a solar air heater, for example. I calculated the figures using Specific heat of mixture of gases=sum of (mass fraction x specific heat of each gas). I then calculated the mass of a cubic metre of air with RH=50% for various temperatures and multiplied specific heat by mass of a cubic metre of air with RH=50 and P=101.325 kPa at various temperatures. The RH makes very little difference to the volumetric heat capacity (although it does make a bigger difference to the specific heat). For instance the volumetric heat capacity of dry air at 35 deg C at P=101.325 kPa=1.154 kJ/degC.m^3 and the volumetric heat capacity for an RH=50% parcel at the same temperature and pressure is 1.159 kJ/degC.m^3.

Air Cleaner

You can email me at millertrader@gmail.com
The blog owner T E Miller (Swayseeker), known as Eddie will not accept liability or responsibility for any problems arising from the use of this blog and its calculations. I try to provide good calculations and analysis, but cannot guarantee that there are no mistakes. Here is a site that tells you how to build your own solar air heater:
 http://www.builditsolar.com/Experimental/PopCanVsScreen/PopCanVsScreen.htm
My Facebook page:
https://www.facebook.com/Swayseeker
Have been doing the following calculations: Los Angeles (latitude 34.05 deg N) has a maximum (always facing the sun) 11.2 kWh of solar energy per square metre on a good day on 1 July. On a horizontal surface it has 8.8 kWh of solar energy per sq metre per day (assuming a sunny day). It takes about 1.2 kJ of solar energy to heat 1 cubic metre of air 1 deg C (volumetric heat capacity of air is about 1.2 kJ per cubic metre per 1 deg C temperature rise - depends on pressure, etc). I have done this for the first day of each month and give a graph of how much air could be heated 5 deg C by one sq metre of horizontal surface by solar energy in one day. These are theoretical values and solar air heaters are certainly not 100% efficient, but the volume is enormous. I have been promoting this idea in Africa, China, US, India, via the Internet, etc, and am hoping it will have a good effect on the world.
If people generally knew the following facts about air the world might have been been different: 
Air is very little affected by radiation (sun shining through it, radiation from fires, heaters and so on). But air is heated by coming into contact with hot surfaces (casing of heaters, hot tar and so on) and the hot ground heats air and causes upward movement of this less dense air on a grand scale. The ground only has fairly superficial contact with air. On the other hand a solar air heater (a sort of greenhouse with a solar absorber to heat up in the sun and large hot surfaces to make contact with the air) is a different matter - it will heat air efficiently and a solar air heater on each rooftop could get warm air rising and out of polluted cities and also cause more rain to fall when vapour condenses in the cooler regions. 
People make their own solar air heaters and I believe India and China, with their pollution, could get polluted air moving out of their cities with them. It takes about 1.2 kilojoules of solar energy to heat 1 cubic metre of air by 1 degree C and every second 0.8 kilojoules of solar energy can easily fall on every square metre of some locations at noon.
The graph shows the number of cubic metres of air in a day that can theoretically be heated 5 deg C, using solar energy falling on a square metre of horizontal surface in Los Angeles. The x-axis shows 1 July, 1 Aug, etc.
Wikipedia says that rain dust (alkaline rainfall deposits, caused by particles from Saharan dust, etc) could help combat acid rain. 
An idea of mine: If one had huge solar air heaters and put Saharan dust in them, the hot air could carry the alkaline dust into sulfur dioxide-polluted air and neutralize acidity.
Wikipedia also says," Acid rain does not directly affect human health. The acid in the rainwater is too dilute to have direct adverse effects. However, the particulates responsible for acid rain (sulfur dioxide and nitrogen oxides) do have an adverse effect. Increased amounts of fine particulate matter in the air do contribute to heart and lung problems including asthma and bronchitis." 
Therefore the rain itself is good, because sulfur oxides, etc, are washed out, improving health prospects (reducing asthma, etc). Rain also washes out ozone, so if one could neutralize rain and get more rain, that would generally be good.
Graph below: The number of cubic metres of air in a day that can theoretically be heated 5 deg C, using solar energy falling on a square metre of horizontal surface in Los Angeles. The x-axis shows 1 July, 1 Aug, etc.

Graphs

The first two graphs are for Cape Town, South Africa (lat 33.9 deg S). These two graphs show 
1) the solar energy falling per day on one square metre, maximum (always facing the sun - upper graph) and for a horizontal surface (lower graph). Solar energy in kWh 

2) the theoretical volume of air per day (cubic metres) that could be heated 5 deg C by a solar air heater of dimensions 1m by 1m always facing the sun (upper graph) and on a horizontal surface (lower graph).

The graph below is for Delhi, India. Lat 28.4 deg N. The graph shows the theoretical volume of air per day (cubic metres) that could be heated 5 deg C by a solar air heater of dimensions 1m by 1m on a horizontal surface. The x-axis shows 1 July, 1 Aug, etc. So on 1 July, in a day, the 1m by 1m solar heater on a horizontal surface in Delhi could heat 5241 cubic metres of air by 5 deg C.

Looking at temperatures and relative humidities for Delhi (India) and taking a low rainfall month of November, with an average RH of 55% and daily average temperature of 20.8 deg C, the graph uses figures as follows: The surrounding air temperature is 20.8 deg C and air is heated to the temperature shown on the T-axis (parcel of heated hotter air is at temperature T deg C), using solar air heaters. The line with the steeper slope shows the height to which the parcel will rise, using a dry adiabatic lapse rate of 9.8 deg per 1000 m rise and an environmental lapse rate of 6.5 deg C every 1000 m (fairly standard sort of figures). The line with less steep slope shows how high the heated air parcel must rise before clouds start to form (uses Espy's equation). When the parcel is heated to 28 deg C it will rise further than it needs to before clouds start to form. Before about 28 deg C it will not rise far enough for clouds to form. Actual lapse rates for Delhi would have to be taken into consideration for accurate conclusions. You can also work this out yourselves.I will tell you the near ground dew point for the parcel - it is 11.43 deg C. Espy's equation says, for clouds to form, the air parcel must rise 125(T-Tdew) where T is the near ground level temperature of the parcel and Tdew is the near ground level dew point of the parcel. As for how high it can rise, after it has risen 1 km, starting at T=27 deg C, say, the temperature of the parcel is 27-9.8 deg and the surrounding air is at 20.8-6.5 deg, etc. When the parcel and surrounding air are at the same temperature the parcel will stop rising (this is modified a bit because water vapour is less dense than air)