Energy From The Sun Flashcards
How would you calculate the energy of a given area on earth e.g the UK
energy per m² x area of land
What is active solar heating and give an example
- A solar collector that collects the sun’s energy to typically heat water
- Flat plate collector
- Evacuated tube
What is passive solar heating
The direct absorption of the suns energy into a building which can then be circulated naturally as heat
What is a solar thermal engine
Similar to active solar heating except the heat transfer fluid is evaporated into a gas to turn a generator for electricity
Explain the difference between direct and indirect loop systems
Direct
* Water is heated directly
* Water circulates through the system
* For warmer climates
Indirect
* Antifreeze heat transfer liquid circulates to solar collector
* Passes through a heat exchanger to heat the water
* For colder climates
Explain the difference between passive and active solar systems
Passive
* Natural convection currents
* No pumps required
* Less maintainence
Active
* Pump used to circulate flow
* More energy and energy used
Define what solar PV is
Takes energy from the sun and directly converts it into electrical energy
List the 3 methods of solar radiation
- Direct
- Diffuse
- Reflected
Where should a solar collector be faced
Towards the equator
Explain what a single axis tracking system allows a solar collector to do
Allows solar collectors to move from east to west to follow the daily movement of the sun
State the advantages and disadvantages of single axis tracking
Advantages
1. Eout can be increased by 25% in warmer climates
2. Repayment period shortened
Disadvantages
1. Complex system, more expensive to set up
2. Electricity needs used to turn the system
3. Locations are restricted to higher solar energy regions
Explain what a dual axis tracking system allows a solar collector to do
Allows tracking of both daily and seasonal variation of the sun’s position therefore increases efficiency
State the advantages and disadvantages of dual axis tracking
Advantages
* Energy output increased by up to 35%
* Repayment period can be decreased
Disadvantages
* Complex system
* Larger quantity of energy used in operation
* Less panels/ unit area due to shading
Describe the operation of a flat plate collector
- Cold Fluid pumped in at a low level
- Enters heat absorbing rising tubes
- Black obsorber plate transfers heat energy
- Fluid rises with natural convection currents
- The fluid is pumped into a hw tank either directly as water or indirectly as a heat transfer fluid
List the components of a flat plate collector
- Rising tubes with cold fluid in and hot fluid out
- Glazing sheet cover
- Absorber plate
- Insulation
List the advantages and disadvantages of a flat plate collector
Advantages
* Cheapest collector
* Suited for colder environments as snow can be melted to c&c
* Efficiency can exceed 80%
Disadvantages
* Heat loss can be minimised but not eliminated
* Efficiency drops at higher temps
* Remains flat all day
* Installation requires two people
Describe the operations of an evacuated tube solar collector
- Water flows through a copper pipe
- Copper pipe connected to an absorption plate
- Solar energy converted to heat as it strikes absorption plate and fluid is heated into gas
- Gas is sent to a copper manifold heat exchanger where the gas heats water
- Liquid falls back down and repeats
List the components of an evacuated tube solar collector
- Copper pipe fluid in
- Black heat absorber plate
- Double wall vacummed glass tube
- Copper manifold heat exchanger
List the advantages and disadvantages of an evacuated tube solar collector
Advantages
* Circular geometry means aoi=90 almost always
* Heat loss to c&c nearly 0
* Around 90% efficient
* Easy to transport
Disadvantages
* More expensive than a flat plate collector
* Will not be able to melt snow (suited to colder environments)
List the 5 factors that effect the amount of roof space required for solar collectors
- Solar radiation levels
- Shading
- Collector Type
- Family size
- Lifestyle of users
