1. Solar Energy Written for Physics 101 Fall 2008

2. The truly vast clean source of energy Output Power of the Sun 4 x10 26 Watts Solar Constant S 0 1.4 kW/m 2 Reaching Surface 1.0 kW/m 2 12 hr day 500 W/m 2 Miami (whole year) 219 W/m 2 Average US 200 W/m 2

3. Energy Units 1 BTU= 1055 Joule = ~ 1000 J 1 calorie = 4.184 J 1 Calorie = 4186.8 J 1 J = 10 7 ergs 1 kilowatt-hour = 3.6 x 10 6 Joules 1 watt-hour = 3600 Joules 1 megaton = 4.184 x 10 15 J

4. Energy Equivalents One ton of coal 2.5 x 10 10 J 1 gal gasoline 1.3 x 10 8 J Wabash Generating Station (600 MW) operating for one day 5.184 x 10 13 J = 2074 tons of coal Wabash Generating Station 600,000,000 W (electrical) or 1800,000,000 thermal divided by 200 W/m 2 = 9,000,000 m 2 = roughly 3.5 mi 2 (note in Terre Haute this would be more)

5. R Values The United States maintains their own definition for R- value, which can be spotted as being approximately six times larger than a standard unit. The imperial R-value is measured in degrees Fahrenheit, square feet hours per Btu, (ft²·°F·h/Btu).United Statesft°FhBtu Unfortunately this does not agree with the international value (K·m²/W), using the SI sys. Use the conversion 1 K·m²/W ≈ 5.67446 ft²·°F·h/BtuSI sys R values are additive, e.g. for a brick home R- value(brick) + R-value(fibreglass batt) + R- value(plasterboard) = R value(total).

6. Typical R values for insulating board The house insulation r value of insulating boards are: Expanded polystyrene 4.00 per inch Extruded polystyrene 5.00 per inch Polyisocyanurate & Polyurethane 6-7 per inch Conduction is the reciprocity of the R value

7. An example Taking an R value of 4, imagine a room of 10 x 10 ft times 6 sides (a cube). Thus the conduction is 0.25 Btu/(sq ft deg F ) BTU/hr or 0.25 x 100 x 6 sq ft x 68 deg F = 10,200 BTU/hr