2.  Allow sunlight in but trap heat in (greenhouse effect). 2 nd most important!  Glass or plexiglass, double paned with air space between works best  Plastic wrap is too thin

3.  Increase the surface area of the water so it will heat quickly

4.  Water should be in or around a conductor (for rapid heat transfer)  Metal is good

5.  The areas containing the water should be black to absorb heat

6.  Insulate outer areas of project to prevent heat transfer  Especially the Ground  Over insulation keeps light from entering and will DROP the temperature

7.  Use of reflectors or mirrors to concentrate light and heat onto water  Difficult to get the right angle due to moving sun  Least important

8.  Angle object 45 degrees to the SOUTHWEST  MOST IMPORTANT!!!!!!!!!!