What is the potential problem with solar energy?

Solar energy demand extra credit problem?

• The average solar radiation incident on the surface of the earth is about 1 KW/m2 for the entire year. A solar house is built with solar panels installed in the roof to provide the heating and electrical energy of the house. If the roof has a surface area of 100 m2 and the panels are installed over the entire roof, will the solar panels be able to provide enough energy to meet the heating and electrical energy demands for the house for the entire year. The total time of available sunlight for energy production is 1000 hours for the entire year. If so, explain how? Note: The average electrical energy demand for the house is 15,000 KWh for the year. It takes about 1000 gallons of fossil fuel with a heating value of 15,000 Btu/gallon to provide heat to the house for the entire year. ( 1 Btu = 0.000293 KWh) Please show all work so i know how you got the answer. Thanks so much for helping me with this extra credit question!!

• Answer:

  The amount of solar energy falling onto the solar panels over an entire year can be found through multiplication: 1 KW/m^2 * 100m^2 * 1,000h = 100,000 KWh To calculate the energy required by the house, we must combine the electrical demand with the heating demand: Electrical: 15,000 KWh Heating: 1,000g * 15,000 Btu/g * 0.000293 KWh = 4,395 KWh Total: 15,000 KWh + 4,395 KWh = 19,395 KWh The house uses 19,395 KWh. Therefore, the sun is providing enough energy to the roof to power the house (and a lot of extra). However, what is missing is the efficiency of the solar panels. The solar panels cannot capture 100% of the solar energy. Basically, to be able to power the house they must be able to capture: 19,395 / 100,000 * 100% = 19.395% Approximately 19.4% of the energy that reaches the roof. Unfortunately, average solar panels have an efficiency of about 12% meaning that no, they could not power the house. Fortunately, if price wasn't a problem, expensive panels can be bought that convert up to 20% (enough to power the house, but only just!). So the answer is 'no' under normal circumstances, but 'yes' it is possible with expensive technology