Solar Power (Thermal) Part 2 Flashcards
What are the four main large scale solar concentrators?
Parabolic Linear Reflector
Fresnel Linear Reflector
Point Focus Tower
Point Focus Dish
How does a parabolic linear reflector work?
A long linear parabolic reflector focus sunlight onto a pipe where the transfer fluid reaches temperatures < 500°C
How does a flat plate reflector work?
Flat plate reflectors focus sunlight onto a pipe where the transfer fluid reaches temperatures < 500°C
How does a point focus tower work?
Flat plate reflectors focus sunlight onto a point target that reaches temperatures of 800°C
How does a point focus dish work?
A parabolic dish focuses sunlight onto a point target that reaches temperatures of up to 500°C
What is a problem of parabolic linear reflectors?
Uneven heating of the collector pipe can cause problems due to thermal stresses as it expands and contracts at different rates on each side
How does a fresnel linear reflector work?
Line focus system which has rows of flat reflection mirrors positioned below a stationary cavity receiver with a single absorbing pipe
Reflective mirrors track sun and concentrate on collector
secondary glass reflector refocuses any missed light
operating temperature ~450 deg
What is the step by step process of linear concentrators?
Sunlight hits the linear reflectors
It is reflected onto the collector where it heats the water
The steam produced is at high pressure & drives a turbine
The steam is condensed and recycled
The turbine is connected to a generator which produces electricity
The electricity is converted to the correct voltage and supplied onto the national grid
What are the advantages of solar concentrators?
Moderate/high efficiency
Large scale and high output
Displaces a large amount of fossil fuels utilised by the public and therefore, saves resources and money.
Reduces emissions in comparison to conventional systems.
Fuel used to heat the transfer fluid is free.
Storage can be incorporated in the system
What are the disadvantages of solar concentrators?
Intermittent source
Large areas of land required
High construction costs.
High maintenance costs.
Expert technical staff required.
Majority of systems are still in prototype stages.
Erosion/fouling of mirrors may take place.
Potential hazard to environment or locals if toxic transfer fluid is used.
Large structures may be considered and eyesore
What are solar chimneys composed and what are its features?
Large transparent solar collector
Tall hollow chimney
Wind turbines inside the chimney
Must be made of glass/plastic and be UV resistant
~⅓ heats the air between
collector and the ground
~⅓ heats the ground
~⅓ is lost.
How do solar chimneys work?
The hot air rising up the chimney generates suction which draws cooler air into the collector to subsequently be heated.
The warm air rising up the chimney drives the wind turbines to produce electricity.
What are the advantages of solar chimneys?
Direct and diffuse radiation collected Will operate in cloudy regions Day and night operation possible Low maintenance Simple building materials No transfer fluids used Moderate/high efficiency Can be scaled to give high output Displaces a large amount of fossil fuels and therefore saves resources and reduces emissions
What are the disadvantages of solar chimneys?
Large areas of land required
Moderate construction costs.
Not resistant to earthquakes
Expert technical staff required.
Erosion/fouling of the collector may take place.
Majority of systems are still in prototype stages.
Large structure may be considered and eyesore
What are the advantages of solar ponds?
Large areas of land required
Moderate construction costs.
Not resistant to earthquakes
Expert technical staff required.
Erosion/fouling of the collector may take place.
Majority of systems are still in prototype stages.
Large structure may be considered and eyesore
