Solar energy is an alternative to fossil fuels for providingelectrical power for both homes and businesses. It may be locallyproduced and used at the same location as the panels, which reducesdistribution costs. Large facilities may be located in availablespace and the power added to the \"grid\" that distributeselectricity. Solar power may be a better choice in rural orundeveloped areas where the grid infrastructure is unreliable orjust not there, and it has been discussed as an alternative forreconstruction in storm-damaged Puerto Rico. It is also useful inless sunny areas, and here in Kentucky the regional power provideris developing a shared solar energy farm to supplement itsconventional power plants. Even the Coal Museum in eastern Kentuckyhas solar panels to provide building power.
1. The Sun provides approximately 1.4 kilowatts (kW) of energyadding all the light striking one square meter perpendicular to aline to the Sun above the Earth's atmosphere. If solar panels are25% efficient in converting this optical energy to electricalenergy, and if they are oriented to make maximum use of incidentsunlight, how much panel area is needed to develop 10% of theregional power production which is 3.5 gigawatts (GW) while the Sunshines? (3.5 GW is 3,500 MW. Currently LG&E has a 10 MW solarfarm covering 50 acres.)
2. A typical single solar panel that would be installed on ahome uses crystalline silicon as the material that creates thecurrent, measures 1x2 meters, and produces 340 watts at 48 volts.It is said to be 17% efficient, allowing that not all the sunlightat the top of the atmosphere reaches the surface, and that somewavelengths are beyond the range over which silicon responds. Howmany of these panels would be needed to supply 15 kW that wouldfulfill the peak needs of a typical home? What area of the roofwould they cover? This is for peak use, but typically the averagepower needs are about 5 kW.
3. If it is sunny 8 hours a day, then you would need 3X as manypanels and a way to store energy to use them 24/7, but storage alsoallows you have fewer panels to meet peak needs. Allowing that thepanels gather enough energy during 8 hours to provide power forthat time and for 16 more hours, how much energy has to be stored?Consider two alternatives: pumped water and Tesla batteries. If youcould pump water to a height of 20 meters, say to a pond or pool upthe hill from your home, how much water by volume would have to bemoved to store this energy . (Use the potential energy of gravity,mgh, to figure this out. ) For batteries, consider the Tesla\"Powerwall\", a module that stores 13.5 kWh of energy and provides 7kW peak AC power.
4. Given what you know about the physics of solar, comment onthe viability of it as a sole source of power for your home, andyour rechargeable electric car. If you have a clever way of storingenergy, mention it here too.
