I was recently reading a blog by Paul at Sun Volt on the possibility of solar panels increasing global warming. I wanted to find out more about the solar heat island effect, or as Paul put it “Heat Islanding” effect. I was wondering just how much concern we should have over this effect as it seems to be a major factor in the possibility of global warming. Most of the information was over my head, but I did get the picture.
Generally, cities are much warmer than rural areas. This is caused by solar energy and how it is reflected and absorbed. The following graph from the Heat Island Group shows how the heat is distributed, you can see the Island effect.
There are a number of factors that contribute to this warming.
- In the rural areas, solar energy is absorbed at ground level and evaporates the water from the vegetation and soil. This evaporation causes cooling, along with other factors, like wind. In the city, this doesn’t happen. Instead the buildings, streets, sidewalks and pavements absorb the energy and with less vegetation, trees, etc., less energy emitted.
- There is less water run off in the city as well, so less evaporation– less cooling.
- There is a higher generation of heat from other factors in the city: cars, trains, and factories, etc. Only about one third of the heat is actually solar.
- Tall buildings create a canyon effect, enhancing the warming and trapping of heat.
- Temperature differences between city and rural may cause different changes in weather.
The EPA has a program called ENERGY STAR ® Roof Products Program for Cool Roofs and this may help curb some of this island effect. Check out the link – there was a good amount of information on how the program works for both building owners and builders.
There is a great deal more research stating that heat islanding has ill effects rather than little or no effect on global warming. Clearly, if it isn’t affecting global warming it is certainly affecting our environment in other ways like air pollution, air conditioning costs, and heat related health issues. In researching this solar island effect, I find it to be of concern to all of us.