Energy From The Sun Flashcards
Explain how an automated tracking system can maximise energy output from solar devices
Daily variations of the position of the sun during the day light hours
Annual variations in the position of the sun in the sky depending on the season/time of year
Variations in positioning in the northern and Southern Hemisphere
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 suns position during daylight hours
It can track the annual variations in the suns position during years/seasons
It can adjust according to location in northern or Southern Hemispheres
State one advantage provided by an evacuated tube solar collector compared to a flat plate solar collector
Conduction losses
Or
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
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 6500 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 would provide a practical solution?
(Assume 1m2 of a flat plate collector provides 450 kWh of useful heat per year)
65% of hot water requirement = 0.65 x 6500kWh = 4225kWh
1m2 flat plate collector provides 450 kWh
4225/450 = 9.38m2
Cannot buy fractions of panels, to meet the 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
Lifestyle of users and hot water requirements
A family uses 6800kWh of hot water per year. If they wish to install a solar thermal hot water system to meet at least 70% of their annual hot water needs, what area of flat plate solar panel would provide practical solution?
(Assume 1m2 of a flat plate collector provides 550kWh of useful heat per year and that solar panels are supplied in 1m2 modules)
70% of hot water needs = 0.7 x 6800kWh = 4760kWh
1m2 of collector provides 550kWh
4760/550 = 8.65
Must be a whole number of panels so the family must install 9m2 of panels
Explain the main benefit of household of installing a flat plate solar collector
Economic reasons. Cost more important in the application than efficiency
State one benefit of a household installing a flat plate collector
Reducing environmental impact
Financial benefit - reducing energy costs
Improved energy security
In the typical arrangement of a PV cell explain the purpose of he following;
1) antireflective coating
2) metal contacts
3) operation of the PV cell
1) maximises the efficiency of the cell by reducing the reflection of light from the surface
2) 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
3) when light falls on a silicon p-n junction some of the photons can create electrons hole pairs through the photoelectric effect
As the electrons move, this creates a potential difference with net positive and negative charge at each side of the junction
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
Describe one advantage and one disadvantage of monocrystalline PV modules
Advantage- most efficient type of PV module
Disadvantage- cost- expensive manufacturing techniques required to ensure efficiency
Name two other types of PV modules
Polycrystalline
Thick-film
Thin-film
Name and briefly describe any two financial incentives that are available to homeowners considering the installation of solar panels
Green deal - financial assistance towards cost of installing solar panels
Feed in tariff for solar PV - where homeowners are paid for the amount of electricity they generate and feed back into the grid
Renewable heat incentive- where homeowners are paid for the amount of heat they generate using their own solar thermal panels
Explain briefly any two passive solar design techniques that can be applied to new and existing buildings
Orientation; main glazed ‘dayrooms’ orientated south (or within 15 degrees of south) Non-habitable rooms towards north
Windows to be appropriately sized; to provide good day lighting and prevent excessive heat loss/heat gain
Use low emissivity glazing; to reduce heat loss through windows
Provide eaves overhangs/bris-soleil; to reduce summer heat gain through windows
Heavy construction/high thermal mass; will absorb heat in winter and even out temperature fluctuations
High levels of thermal insulation; will reduce the heat loss of the building
Name two types of concentrating Solar Power (CSP) systems
Parabolic troughs
Fresnel reflectors
Solar dishes
