Energy from the Sun Flashcards
Which way should the panel be facing and why
In the Northern Hemisphere, the panel must be facing south at 45°. The closer the roof-panel is to exactly south, the more energy can be absorbed from the sun.
What is the use of solar thermal panels
Solar thermal panels capture the suns energy, and use it to warm water can be used in the house/ building, reducing energy costs and co2 emissions and may generate revenue.
What is a flat plate collector
It is a metal box with a glass cover with glazing on the top and a coloured absorber plate in the middle. The bottoms and sides are insulated to prevent energy losses in the system. Radiation from the sun passes through the glazing and strikes the absorber plate, where it is absorbed. The energy from the sun is transferred to thermal energy within the absorber plate, and so the particles vibrate much more. This thermal energy is transferred to liquid passing through pipes attached to the absorber plate, where it is then pumped to the water tank.
Most solar panels are on this type, being cheaper
Not as efficient, and will have longer repay times.
What is a Evacuated tube solar panels
Wet vapour (liquid and dry vapour, which can as you remember, absorb a lot of energy) rises to the top of copper heat pipe, transferring thermal energy to the top, the tip of the copper heat pipe is connected to a header pipe through which more fluid flows. Heating takes place between the tip of the copper heat pipe and the header pipe, which raises the water temperature between 90°c and 60°c
How do panels work
The panels work, using a semi conductor such as silicon, which has the bottom and top halves of the crystal doped, making one side negative and the other side positive. Once the semiconducting silicon is exposed to sunlight, electrons are released from the negative side, and a do circuit is induced to flow.
What is a solar tracking system
It is a device for orientating a solar panel or concentrating a solar reflector or lens towards the sun
What’s the advantages and disadvantages of a solar tracking system
ADV
-Trackers generate more electricity than their stationary counterparts due to increased direct exposure to solar rays. Can increase by 10-25%, Electricity production increases 30% in single axis.
-Created to certain needs, such as Single-axis and dual-axis
DisADV
-More expensive than stationary counterparts
-More maintenance
-Large foundations
-More preparation needed as system is more completed
-Designed to certain climates- Little to no snow
What is a Single Axis Tracking System
It turns on centre axis that follows the tilt to sun travelling east to west.
What is a dual axis tracking system
It moves north and south tilt during different seasons as well as tilt east to west with the sun. It orients a mirror and redirects sunlight along a fixed axis towards a stationary receiver. But the system can also gain additional yield on your PV cells
How does the flat plate collector work and give its advantage and disadvantages.
Energy from the sun is absorbed as it passes the glazing and strikes the absorber plate which is then converted to thermal energy. This thermal energy is transferred to liquid passing through pipes attached to the absorber plate where it is then them pumped to the water tank. ADV -Cheap-Cheaper initial cost DisADV -Not efficient-Longer repay times.
How does an evacuated tube collector and gives its advantage and disadvantages
The glass absorbs the energy from the sun. The inner layout is coated with a reflective coating, to help ensure that the energy does not escape again. When the sun rays are radiated onto the evacuated glass tube, most of the energy is absorbed by the copper heat pipe, which transfers this energy to the antifreeze located inside the copper heat pipe. ADV -Efficient-90% DisADV -Larger initial cost
Explain the benefits to households of installing a flat plate solar thermal collector
Financial Costs
-Receive payments for the electricity you export through the Feed-in tariff scheme.
-Virtually no running costs
Savings
-Helps cut electricity costs. Once initial installation costs are paid, the electricity costs will be reduced as sunlight is free
-Virtually no running costs
Greenhouse gas emissions
-Solar electricity is green renewable energy and doesn’t release any harmful carbon dioxide or other pollutants. A typically home solar PV system could save around 1.2 to 1.7 tonnes of carbon per year.
Planning Permission
-Installed on any part of the external walls of the building if contains a flat
-Panels when installed on a flat plate roof are situated within 1 metre from the edge of the roof or protrude more than 1 metre above the plane of the roof.
-Panels when installed project higher than the highest point of the roof
Name and explain the different pieces in a photovoltaic cell structure
A- Encapsulate: The encapsulate, made of glass or other clear materials such as clear plastics, seals the photovoltaic cell from the external environment
B- Contact Grid: The contact grid is made of a good conductor, such as metal, and it serves as a collector of electrons.
C- The Antireflective Coating (AR Coating): Through a combination of a favourable reflective index, and thickness, this layer serves to guide light into the photovoltaic cell, without this layer, much of the light would bounce off the surface of the cell.
D- N-Type Silicon: N-Type silicon is created by doping the silicon with compounds that contain one more valence electrons than silicon does, such as with either phosphorus or arsenic. Since only for electrons are required to bond with the four adjacent silicon atoms, the fifth valence electron is available for conduction.
E- P-Type Silicon: Is created by doping with compounds containing one less valence electrons than silicon does, such as boron. When silicon (Four valence electrons) is doped with atoms that have one less valence electrons (three valence electrons) only three electrons are available for bonding with four adjacent silicon atoms, therefore an incomplete bond exists which can attract an electron from a nearby atom. Filling one hole creates another hole in a different Si atom. This movement of holes is available for conduction.
F- Back context: The back contact of a photovoltaic cell is made out of metal covers the entire back surface and acts as a conductor
What is the calculation for sizing a hot water system
Step 1 = Need to find out how much energy the system must generate.
Energy Req = Annual Energy x % (decimal form)
Step 2= Determine the exact number of m2 required to produce this energy
(En) Energy required = 4875 kWh
(En²) Energy Pv m² = 425 kWh En = Em² x N
(N) No m³ ?
Rearrange N = En/En²
N = En/En² = 4875/425 = 11.47 m² (2dp) Answer = 12m²
What are the general advantages of thin films are:
- Lower production costs and installation costs, resulting in a lower cost per watt in comparison to thick film cells.
- Flexible- Thickness range from a few nanometers to tens of micro metres, meaning that the can be bent for application to curved surfaces.
- Their lightweight, which means that fitting is less time consuming with less fasteners required, and so costs are reduced
- Works well in lower light areas
