1. EXAMPLE 3 URBAN HEAT ISLAND

2. Cities are made up of large amounts of concrete and asphalt that heat up in the daytime from sunlight but do not cool off completely at night. As a result, urban areas tend to be warmer than the surrounding rural areas. This effect is called the urban heat island and has been documented in cities throughout the world. In Figure 5.11 function computes the average increase in night time summer temperatures in degrees Celsius at Sky Harbour Airport in Phoenix from 1948 to 1990 where x is the year. In this graph 1948 is the base year with a zero temperature increase. This rise in urban temperature increased peak demand for electricity. In Figure 5.12 function computes the percent increase in electrical demand for an average night time temperature increase of x degrees Celsius.

4. Compute the percent increase in peak electrical demand during this present year 2009. Use the composite function FIRST: FIND THE AVERAGE INCREASE IN NIGHT TIME TEMPERATURES FOR 2009 SO THAT YOU CAN SUB IT INTO THE COMPOSITE FUNCTION! Sub in 2009 for X

5. SECOND: SUB INTO Sub in For the X values Solve for g (the increase in demand for electricity)

6. Therefore, in 2009, there will be a 10.17% increase in peak electrical demand.