Chapter 8 LO3: Explain how an automated tracking system can be used to maximise energy output from solar collectors Flashcards
Solar radiation arrives on the surface of a solar collector by 3 different methods. Name those 3 different methods and describe each in detail
Direct Radiation - Involves sunlight that travels from the sun in a straight line directly to the surface of the Earth. As the rays travel in a straight line, and parallel to each other, they can be blocked by an object and this can create shadows. Although a shadow is blocking an area sunlight must be hitting this area in a different form for you to see the colours in the shadowed area
Diffuse Radiation - As the light strikes the earths atmosphere some of it is scattered in different directions as it interacts with the molecules in the atmosphere. Some of this scattered radiation, travelling in all directions, does strike the surface of the Earth. These randomly orientated rays of radiation make up the diffuse light which can be substantial depending on the weather cloud cover and pollution levels. On cloudy days, light still reaches the Earth from the Sun. The sunlight is derived via diffused radiation as well as reflected radiation. On a clear day with the sun directly overhead, diffuse radiation can still make up 15% of the solar radiation striking a point on the Earth’s surface.
Reflected Radiation - This radiation strikes a surface on the Earth and is reflected. This reflected light can then go on to strike another part of the Earth, building or even solar panel. This reflected radiation is ultimately derived from either direct or diffuse radiation. LOOK AT BOOK FOR REFLECTED RADIATION
Describe how in southern France the different types of radiation, direct and diffuse, vary from the summer to the winter seasons.
Southern France has a much greater percentage of solar radiation from diffuse radiation. In summer months around 50% can be from diffuse while in winter, which is associated with predominantly cloudy conditions, nearly 100% is diffuse as sunlight cannot get to the Earth’s surface directly through cloud cover.
Would a solar tracking system, either single or dual axis, be a viable business investment in NI? Is this the same in the Southern Hemisphere?
No, as the 2 tracking systems are more advantageous in countries closer to the equator. They maximise direct solar radiation, NI is not within a region which has a high solar radiation which makes this investment in NI unfeasible. This is not the same in the southern hemisphere as regions have a lot higher solar radiation Levels.
What is the ideal orientation of a solar collector placed in the Northern hemisphere. Is this the same in the Southern Hemisphere?
The ideal orientation of a solar collector in the Ni is that the system should be south facing. This is the opposite in the southern hemisphere where the solar collector should be north facing.
Where are the generally accepted tolerances in terms of degrees either side from the ideal orientation in a given hemisphere?
In the northern hemisphere e.g., UK and Ireland the degrees should be in range of 35 to 40•. This pitch angle is the angle the solar collector is above the horizontal.
Describe the operation of a single axis tracking system.
The angle of incidence on solar collectors is maximised to absorb the maximum amount of direct radiation from the sun. To do this the solar tracking system can be utilised. Here the solar collectors turn the collectors towards the east or west to track the sun’s positioning during the course of the day. The radiation axis of such a system is in the north south plane allowing the collectors to be rotated towards the or west as necessary. The solar collectors can now rotate from the east in the morning, in a westerly direction throughout the day, to ensure that the angle of incidence is maintained at 0•.
Advantages of a single axis tracking system
1 - The energy output from the system will be higher, it can be higher by as much as 25%. In warmer climates this justifies the higher initial costs.
2 - The higher output obtained means that the repayment period is reduced which makes thermal better long-term in warmer climates
Disadvantages of a single axis tracking system
1 - Complex electrical and mechanical equipment is required for the tracking system. This drives up the price of such systems.
2 - The motors or pneumatic cylinders required to rotate the collectors require power to operate. Consequently, some of the electricity produced by the system is used for tracking operation.
3 - The locations where single axis tracking cane be installed are restricted to high solar radiation regions. Tracking only maximised direct solar radiation which is constantly high in hotter climates close to the equator. This makes them unfeasible in NI
4 - When one panel rotated towards the sun in the morning and evening, a shadow I’ll be created in behind the panel. A panel beside it will need to be spaced further away to ensure that this shadow region does not block the sun from striking its collectors.
How does a dual axis tracking system differ from the single axis tracking system?
The dual axis tracking system has an additional degree of rotation, the additional axis of rotation lies in the East West plane. Dual axis tracking system is more expensive than single axis tracking system. The quantity of energy required for dual is lever than single.
What additional benefits are offered by a dual axis system compared to a single axis tracking system.
Much higher energy output as much as 35%. With this repayment periods are reduced which makes them better long - term investments in warmer climates
CCEA PPQ
Q1) Explain how an automated tracking system can maximise energy output from solar devices.
Solar tracking devices must be able to track the relative motion between the Earth and the Sun this can be completed with 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 year. (Earth’s elliptical orbit around the Sun) Also variations on positioning in the Northern and Southern hemisphere. ( Earth’s tilt on its own axis is 23.45• and elliptical orbit. Tracking device must be able to change tilting angle and rotate on its own axis to achieve optimum tracking.
Q2) Outline 2 ways in which automated solar tracking can maximise the energy output from solar collectors.
Any 2 from : It can tilt and rotate on its own axis to achieve optimum tracking.
It can track the variations in the sun’s position during day light hours ( Earth spinning on its own axis)
It can track the annual variations in the sun’s positioning during years / seasons (Earth orbiting the sun)
It can adjust accordingly to location in Northern or Southern hemispheres
