Solar Energy Flashcards
State one advantage provided by an evacuated tube solar collector compared to a flat plate solar collector
The design of a evacuated tube solar collector eliminates conduction/convection losses
State three factors which should be considered when calculating the roof area required to install flat plate thermal solar panels on a house
Any three of; Solar Radiation levels of site/roof Shading Proposed collector type Family size and hot water requirements Lifestyle of users hot water requirements
A household uses 6,500 kWh of hot water per year. If the owners wish to install a solar thermal hot water system to meet at least 65% of their annual hot water demand, what area of solar panel (flat plate) would provide a practical solution?
(Assume 1m2 of a flat plate collector provides 450 kWh of useful heat per year)
0.65 x 6500 = 4225 kWh
4225/450= 9.38 m^2
Cannot buy part of a panel so 10 m^2
Explain the main benefit to households of installing a flat plate solar collector
Reduces heating costs on a site or in a household
Explain the purpose of the antireflective coating
Maximises the efficiency of the cell by reducing the reflection of light (photons) from the surface
The role of the metal contacts
Necessary to allow for circuitry necessary to facilitate the flow of electrons in the circuit from the p to the n layer of the cell
Explain the operation of the pv cell
When light falls on a silicon p-n junction some of the photons can create electron hole pairs through the photoelectric effect. {1}
As the electrons move, this creates a potential difference with net positive and negative charge at each side of the junction (pn junction). {1}
Contacts on either side of the cell connect the cell to an external load and permit the electrons to travel around the circuit loop back to neutralise the valency hole on the opposite side of the potential barrier
