Past Paper Sun Flashcards
With reference to the figure below, explain how an automated tracking system can maximise energy output from solar devices. {3}
Answer to make reference to the fact that a solar tracking device must be able to track the relative motion between the Earth and the Sun and make reference to at least three of the following design parameters;
• Daily variations of the position of the sun during day light hours (earth spinning on its own axis).
• Annual variations in the position of the sun in the sky depending on the season / time of the year (Earths elliptical orbit around the Sun).
• Variations in positioning in the Northern and Southern hemisphere (Earths tilt on its own axis is 23.45 degrees and elliptical orbit).
• Tracking device must be able to change tilting angle and rotate on its own axis to achieve optimum tracking.
Outline two ways in which automated solar tracking can maximise the energy output from solar collectors.
It can tilt and rotate on its own axis to achieve optimum tracking.
• It can track the variations in the sun’s position during daylight hours (earth spinning on its axis).
• It can track the annual variations in the sun’s position during years/seasons (earth orbiting the sun).
• It can adjust according to location in northern or southern hemispheres.
n the space below sketch a diagram of a typical flat plate thermal solar panel and clearly label the following; {4}
• Inlet and outlet connections.
• Flow tubes
• Absorber plate.
• Insulation.Inlet and outlet connections. {1}
• Flow tubes. {1}
• Absorber plate. {1}
• Insulation.
State one advantage provided by an evacuated tube solar collector compared to a flat plate solar collector. {1}
Answer should make reference to the fact that evacuated design eliminates;
• Conduction losses. {1}
or
• Convection losses. {1}
State three factors which should be considered when calculating the roof area required to install flat plate thermal solar panels on a house. {3}
Answer to include any three of the following;
• Solar radiation levels of site / roof.
• Shading.
• Proposed collector type and performance specifications.
• Family size and hot water requirements.
• Lifestyle of users and 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? {3}
(Assume 1m2 of a flat plate collector provides 450 kWh of useful heat per year)
1: 65% of hot water = 0.65 x 6500kWh = 4225 kWh
2: 1m² flat plate collector provides 450 kWh
4225/450 = 9.38 m²
3: Cannot buy fractions of panels to meet at least requirements must install 10m²
State three issues which should be considered when calculating the amount of roof space required for a flat plate thermal collector.
Solar radiation levels of the site / roof
• Shading
• Proposed collector type and performance specification.
• Family size and hot water requirements
Explain the main benefit to households of installing a flat plate solar collector.
Economic reasons. Cost more important in the application than efficiency. {1
State one benefit to households of installing a flat plate collector
One from;
• Reducing environmental impact.
• Financial benefit – reducing energy costs.
• Improved energy security.
Explain the following;
Question (I); The purpose of the antireflective coating. {1}
Environmental Technology – AS Past Papers Overview 2018;
Question (II); The role of the metal contacts.
Question (III); The operation of the PV cell.
Answer;
Maximises the efficiency of the cell by reducing the reflection of light (photons) from the surface.
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.
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.
Explain the purpose of the anti-reflection coating. {2}
(II) Explain he operation of the PV cell. {3
Anti-reflection coating maximises the efficiency of the cell {1} by reducing the reflection of light (photons) from the surface {1}.
(II) When light falls on the 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 either side of the p-n junction. {1}
Contacts on either side of the cell connect to an external load and permit the electrons to travel around a loop back to neutralise the valence hole at the opposite side of the potential barrier.
Describe one advantage and one disadvantage of monocrystalline PV modules.
Advantage; Most efficient type of PV module. {1}
Disadvantage; Cost – Expensive manufacturing techniques required to ensure efficiency.
Name two other material types of PV modules
Answer to include any two of the following;
• Polycrystalline.
• Thick-film
• Thin-film
State one advantage and one disadvantage of monocrystalline PV modules.
Advantage: It is more efficient than other PV cells. {1}
Disadvantage: It is more expensive.
Name and briefly describe any two financial incentives that are available to homeowners considering the installation of solar panels.
Green deal {1}; Financial assistance towards cost of installing solar panels {1}.
• Feed-in-Tariff for Solar PV {1} Where homeowners are paid for the amount of electricity they generate and feed back into the grid {1}.
• Renewable heat incentive {1}; Where homeowners are paid for the amount of heat they generate using their own solar thermal panels {1}.
