Solar radiation calculation
Incoming radiation is calculated as a result of the following factors:
- Height above the horizon
- Azimuth angle
- Depth of the atmosphere
- Angles of solar collector
Formula to calculate how much energy we receive from the Sun
E = 3.6 10-9 Snr2
Means to collect solar:
- Early and late in the day the solar angles are low
- Angle panels/mirrors are pitched towards the sun
- Mirrors can be fixed (facing north at angle of latitude inclination for maximum or alternatives to maximise power in particular times of the day/season) or moving (solar tracking)
Solar energy diagram
Mean solar radiation in Australia
The best solar resource is located far from the populous Australian cities where the power is needed the most. The highest mean solar radiation in Australia is located in the top western side and through the top center of the island.
Summary of Solar Types
Sunlight that is directly converted to electricity (current) through photovoltaic cells (solar PV). Photovoltaics generate electricity without no moving parts from the renewable source of sunlight.
- Small scale residential rooftop solar PV (laminated solar cells = PV module)
- Building integrated PV (BiPV) differs from traditional PV systems in that the solar cells are integrated into the materials, such as a solar facade, integral roof modules, roofing tiles, etc.
- Large scale solar PV plants (‘solar farms’) (PV modules linked together = PV array)
Solar energy used to heat water
- Solar thermal hot water systems
- Concentrated Solar Power (CSP)
- Solar PV
Solar PV is the only technology that converts solar directly into electricity. Solar energy in the form of light hits the solar panel, which excites electrons in the panel and creates an electric current. The current created by the solar panel is direct or DC current, and it flows to an inverter box which converts it into alternating or AC current. Most residential solar panel systems are grid-tied, meaning that there is no backup battery system involved. Current supplied by the solar panels either flows into the home or into the grid through the home’s electric meter. Under current Australian government schemes, homeowner can be compensated for this surplus power.
Components of PV system
- PV module
- Controller (includes regulator, invertor and grid interface)
- Batteries and enclosure
- Power cables, connectors, buses and switchgear
- Electrical grounding network
- AC loads and DC loads
Types of PV systems
- Stand alone PV systems
- Direct coupled
- DC load with battery
- DC load with battery and charge controller
- DC & AC loads with battery, charge controllers and inverter
- Stand alone hybrid systems
- Hybrid system with AC and DC loads, battery, charge controller and inverter
- Grid connected systems
- Grid connected AC loads only
Direct Current (DC) is unidirectional flow of electric charge while Alternating Current (AC) is a electric charge flows in a constant direction.
- AC to DC: Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction.
- DC to AC: Direct current may be made into alternating current with an inverter or a motor-generator set.
Three main PV technologies:
- Crystalline Polysilicon (c-Si costs less than US $1.40/Wp)
- Thin Film (a-Si costs about US $0.80/Wp)
- Organic PV
- Market share is dominated by Chinese and Taiwan manufactures 14 GW per year (First Solar, Suntech, Sharp)
- Europe, Japan, North America, rest of the world are all under 5%
- There is 67.3 MW of PV installed globally, with 27 GW of newly installed PV in 2011
- Europe, Japan, North America, rest of the world are all under 5%
Solar Thermal Energy
Solar thermal energy (STE) is a technology for harnessing solar energy for thermal energy (heat). STE are much more efficient than photovoltaics. Instead of turning sunlight directly into electricity, the solar energy is used to heat up water that is used to generate hot water or power.
At a small scale, Solar Thermal Hot Water Heating is used for buildings to heat water for the building. Solar energy is collected using a solar panel which heats water in hot water cylinder. The hot water is directed through the pipes. There is a controller and pump that is also connected to control the system. These systems are very easy to install and can attract government rebates.
At a large scale, Concentrated Solar Power Plants use mirrors or lenses to concentrate a large area of sunlight, or onto a small area. Electrical power is produced when the concentrated light is converted to heat, which drives a heat engine (usually a steam) connected to an electrical power generator.
At the Australian federal level, under the Large-scale Renewable Energy Target (LRET), in operation under the Renewable Energy Electricity Act 2000 (Cth), large scale solar thermal electricity generation from accredited RET power stations may be entitled to create large-scale generation certificates (LGCs). However as this legislation is technology neutral in its operation, it tends to favour more established RE technologies with a lower levelised cost of generation, such as large scale onshore wind, rather than solar thermal and CSP. At Australian State level, renewable energy feed-in laws typically are capped by maximum generation capacity in kWp, and are open only to micro or medium scale generation and in a number of instances are only open to solar PV (photovoltaic) generation. This means that larger scale CSP projects would not be eligible for payment for feed-in incentives in many of the State and Territory jurisdictions.
There is currently 2GW of concentrated solar power facilities in the world. Lead mostly by developments in Spain and the US. Completing the Australia Solar Flagship program would see Australia reach 2GW CSP by 2020.
Types of Concentrated Solar Power (mirrors and solar collectors)
a) Parabolic Trough
- Most common and largely installed CSP technology
- Similar to Linear Fresnel but instead of flat solar panel, concave mirrors are used to focus the solar onto the working liquid (oil) that is in an absorber tube located at the focal point
- Heat transfer to generate steam through the turbine
b) Linear Fresnel
- Sun focus on lines of working liquid (oil or water) which can boost steam
c) Solar Dish
- Central receiver system with dish collector
- Stirling engine is attached to the solar panel so that the solar power is concentrated to the engine
- Can achieve 30% efficiency
- Stirling engine heat up the gas to then expand and move the piston to power the engine
d) Solar Tower
- Large field of solar panels with solar tracking concentrating solar to a tower
- Working fluid is molten salt which transfers heat to steam to generate power through turbines
- Energy storage potential
Most techniques for generating electricity from heat need high temperatures to achieve reasonable efficiencies. The output temperatures of non-concentrating solar collectors are limited to temperatures below 200°C. Therefore, concentrating systems must be used to produce higher temperatures. Due to their high costs, lenses and burning glasses are not usually used for large-scale power plants, and more cost-effective alternatives are used, including reflecting concentrators.
Solar in Australia
Australia’s cumulative installed capacity of solar power at the end of 2011 was 1044.2 MW (Clean Energy Australia, 2011). Small scale PV accounted for 1031 MW and the remainder was generated by 27 large scale PV power plants (over 100kW) and 1 solar thermal plant. Future investment in solar technologies is expected to rise as Australia moves towards its renewable target by 2020.
Small and large PV module costs have been dropping significantly with learning rate of 22% between 1979 to 2003 (Hearps, 2011). PV LCOE range between $275-$454/MWh and is comparatively more expensive than CSP LCOE at $151-$195/MWh (EPRI, 2011). Note that utility scale CSP baseline LCOE is about $250 p/MWh while revenue streams in main grid connected markets is about $120 p/MWh (including renewable certificates). The wind down in European subsidies and over-supply from Chinese manufacturers has also influenced the drop in the price of PV over the last 10 years.
Currently 67.4 GW of PV
Large solar thermal power stations
- 354 MW Solar Energy Generating Systems power plant in USA,
- Solnova Solar Power Station (Spain, 150 MW),
- 13.9 GW announced globally through 2014. Spain is the epi-center CST development.
- 3 WB projects for integrated solar thermal/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco have been approved.
Advantages and Disadvantages
|Small scale solar PV||
|Solar thermal hot water||
|Large scale solar PV||
|Concentrated Solar Power||