Please enable JavaScript.
Coggle requires JavaScript to display documents.
Solar Power :sunny:, Brise Soleil :scroll: - Coggle Diagram
Solar Power
:sunny:
Amount reaching earth is greater than humanity should need to harness
Problems with reliable, large scale commercial use
Problematic Properties
:partly_sunny_rain:
Intermittency
:forbidden:
availability and intensity depends on daily/seasonal cycles
Reliability
:forbidden:
Daily/Seasonal cycles are predictable :heavy_check_mark:
Energy intensity changes caused by cloud cannot be accurately predicated :red_cross:
Clouds, dust, smoke scatter the light
Cannot be intensified and focused
By mirrors and parabolic reflectors
Energy Density
:forbidden:
Low energy density requires large areas of solar collectors
To get a significant amount
Angle of incidence changes daily and seasonal cycles
No single optimum position for a solar panel to harness solar power
Reduces energy density further
Locational Constraints
:world_map:
Can be used anywhere in the world
Most viable where light levels are highest
Dry sunny deserts
Systems that concentrate the sunlight
Parabolic reflectors
Only work when there is no cloud
So rays of light are parallel and reflect onto the absorber
Areas that are a long way from the equator have long summer days
Increases avaliability of solar power
Winter days are short and light levels low
Harnessing
:hammer_and_wrench:
Photothermal solar power
:sun_with_face:
Absorb sunlight to produce heat
Usually to heat water or domestic hot water
Heat harnessed can be retained in a thermal store for later
In a well insulated tank
Materials such as
Water
Sand
Concrete
Molten salt can be used if the energy has been concentrated to produce much higher temps
Passive solar architecture
:house_buildings:
Buildings can be designed to maximise the absorption of sunlight
Without the use of active equipment
Over heating in summer can be reduced with a fixed solar screen
Deflects the sunlight
Adjustable screens or ventilation
Heat Pumps
:fuelpump:
Uses the change in state
Liquid to gas
To absorb heat from the environment
Releases it within a building when the gas condenses to a liquid
Heat source
Ground
Atmosphere
Change in state caused by pressure
A compressor pump to condense the gas then a pressure relief valve to cause the liquid to boil
Absorb heat energy from low energy density sources and produce high temperatures in the building to be heated
Heat energy released can be four times more energy to run the heat pump
Less is released if the temp of the heat source is lower
NB heat pumps can also harness other sources of heat
Geothermal energy :hotsprings:
Photovoltaic (PV)
:camera_with_flash:
When a PV cells absorbs photons of light
Electrons are dislodged from atoms in the upper layer of the PV cell
Flow along an electrical conductor from this electrically negative layer to the relatively positive lower area
A wide range of improved PV cells have been developed
Some have lower efficiencies but are cheaper to manufacture
More expensive ones have higher efficiencies at converting light to electricity
Early uses
For isolated uses of electricity
With a rechargeable battery for night time operation
Solar farms are now used to deliver electricity to grid connected uses
Types
Multi junction
46.%
Single Junction gallium arsenide
29.1%
Crystalline Silcon
27.6%
Environmental Impacts
:evergreen_tree:
Manufacture of solar panels
:building_construction:
Making solar panels - extraction and processing of materials
Metals
Plastics
Paints
Silicon
Making PV panels - produces toxic wastes
Silicon tetrachloride
Small amounts of cadmium
Can be controlled but adds costs
Impacts during use
:warning:
Do not require much maintenance :heavy_check_mark:
Cleaning requires water
May be scarce in areas best suited to solar (dry deserts)
Large solar farms can occupy land that could be used for other purposes
Large areas of urban roof space that could have panels installed
No land use conflict :heavy_check_mark:
New technologies
:desktop_computer:
Multi-Junction photovoltaic cells
:video_camera:
Multi layers of different materials
Each absorbs different wavelengths
Greater amount of available light is absorbed and converted
Anti-reflective surfaces
:crossed_swords:
PV cells with smooth surfaces reflect 30% of light that hits them
Grooved/textured surfaces reflects light into the cells rather than away
Some designs mimic the structure of the corneas of moth eyes
Very efficient at absorbing light
Concentrating solar power (CSP) + thermal storage
:chart_with_upwards_trend:
Parabolic reflectors are used to increase energy density
The light is absorbed by tubes of oil
Used to heat molten salt in large insulated tanks
The salt is heated up to 500 degrees
Used to boil water and drive steam turbines whenever electricity is required
Over comes intermittency
Photovoltaic/Thermal hybrid systems (PVT systems)
:zap:
Efficiency of PV cells drops at high temps
Electrical resistance increases
Hybrid systems absorb heat for other uses:
Space/Water heating
Cools the PV system increasing the efficiency
Transparent PV cells
:white_flag:
PV cells that allow most of the light in can be used in windows
Some are transparent so that they look just like windos
Some provide shade and reduce overheating
Heliostats
:helicopter:
Alters gthe angle of a solar panel
Always at optimum angle for absorbing light
Self-Cleaning Panels
:shower:
Nanohydrophonic surface
Brise Soleil :scroll: