Forms Of CSP Technology
Forms Of CSP Technology PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology

The three most promising solar thermal technologies are the parabolic trough, the central receiver or solar tower and the parabolic dish. Worthy of mention is also the solar sphere technology.

 
Solar Tower Systems PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology

 

Early power towers utilized steam as the heat transfer fluid, molten nitrate salt is used today because of its superior heat transfer and energy storage capabilities. Current European designs use air as heat transfer medium because of its high temperature and its good handiness. Utility scale tower power plants  will be sized to produce anywhere from 50 to 200 MW of electricity.

 

 

 

      

sketch of central receiver

 

 

(Known also as Central Receiver)

The technology utilizes many large, sun-tracking mirrors (heliostats) to focus sunlight on a receiver at the top of a tower. A heat transfer fluid heated in the receiver is used to generate steam, which, in turn, is used in a conventional turbine-generator to produce electricity.

 
Parabolic Trough PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology


Parabolic trough systems use trough-shaped mirrors or reflectors to focus sunlight on to a receiver tube located at the focal point of the reflectors. The tube contains oil or similar fluid that serves as heat transfer fluid and heat transporter which takes the heat (ca. 400 ºC) to where it can be used to produce superheated steam to generate electricity.Trough designs can incorporate thermal storage - whereby the heat transfer fluid in its hot phase is stored- allowing for electricity generation several hours into the evening. Currently, all parabolic trough plants are "hybrids," meaning they use fossil fuel to supplement the solar output during periods of low solar radiation.

 

 
Linear Fresnel PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology



Linear Fresnel
mirror system is similar to parabolic trough but uses long flat mirrors at different angles to concentrate sunlight on to a tube containing heat-collecting fluid. In some variants, sunlight is concentrated on to PV panels.



Benefits Fresnel system are ruggedness, low cost construction, primary components steel, glass, water, efficient use of land, air cooled, minimal water use, no toxic materials, easily protected from hail and dust storms, can be hybridized with fossil fuel plants.

 
Parabolic Dish PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology



Parabolic dish
systems are comparatively small units which use a dish-shaped reflector to concentrate sunlight, with superheated fluid being used to generate power in a small engine at the focal point of the reflector. Their potential lies primarily in decentralized power supply and remote, stand-alone power systems.  Current trends show that two broad pathways have opened up for large-scale delivery of electricity using solar thermal power. One is the ISCC-type hybrid operation of solar collection and heat transfer combined with a conventional power plant. The other is solar-only operation, with increasing use of a storage medium such as molten salt. This enables solar energy collected during the day to be stored then dispatched when demand requires.

 
Solarsphere PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology



Solarsphere is another CSP based technology that combines elements of both direct intercept dishes and
Solar Towers. The possibility of using materials such plastic (PETE) for Solarsphere production presents opportunities for affordable concentrators.  Solarsphere is not market tested yet.

 
Solar Updraft Power PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology

 



Solar Updraft Tower, also known as Solar Chimney or Solar Aero Power Plant:

Unlike the CSP plants with reflecting mirrors, Solar Updraft Tower uses translucent (transperent) roof heat collector (greenhouse) to trap heat and warm up air inside the green house. Solar Updraft Tower uses warm air escaping a sun heated canopy trap to drive turbine to generate electricity, unlike reflecting-mirrors-based CSP plants which use superheated steam/fluid to drive turbine to make electricity. Updraft tower also operates with cloudy sky, as well as utilizes diffuse light, while reflecting-mirrors-based CSP plants can utilize only direct light.
With sun heat, air beneath a translucent roof of the mega greenhouseis warms up. The hot air mass drifts up the tower placed at the center of the roof while cold air from outside drift into the green house to occupy the space left. The hot air creates an updraft (i.e it drifts up) along the tower to escape the green house and in the process drives wind turbines placed inside the tower which in turn generates electricity.
To set up a solar Updraft power station basically three major components are required: - a large translucent canopy (green house) for solar heat trapping, a tower (chimney) at the center of the green and turbines.

The solar Updraft power station operates1 like a hydroelectric power plant, but it uses hot air instead of water. 

1Operational similarities with hydroelectric power plant:

·         Solar Updraft Tower power plant uses dynamic energy of up-drafting buoyant warm air. Hydroelectric power plants use the dynamic energy of falling water due its gravity.

·         Both use turbines in order to transform part of their fluid’s dynamic energy to rotational energy and through their geared electric generators to produce electric energy.

·         The efficiency of the of Solar Updraft Tower power plant is proportional to the solar chimney’s height, in the same way the efficiency of the hydroelectric power plant is proportional to the dam height.

Net energy payback is estimated to be 2-3 years.
Advantages: continuous electricity generation is possible: heat can be stored inside the greenhouse, to be used for warming the air later at night when there is no sunshine. Materials with high specific heat capacity are used for heat storage. Such materials as water can be filled in black tubes placed under the collector. The tubes radiate heat at night to heat up air and cause it to rise just like in the day time. This ensures operation during cooler days during rainy season, dependent upon the temperature differential between the air inside the translucent canopy and air at the top of the tower.

Even though this technology is simple, for it to be efficient it requires a large area of greenhouse and a very tall tower. 

Disadvantages: a solar updraft tower power station would uses a significant area of land if it were designed to generate as much electricity as is produced by modern power stations using conventional technology. but when looking at electricity output versus total size, they use less land than hydroelectric dams (including the size of the lake behind the dam) or coal plants (including the amount of land required for mining and excavation of the coal). While all power plants require land and have an environmental impact, the best locations for solar Updraft tower is the desert, arid sahel and savanna areas:- with plenty of land.

 

 

 
Floating Solar Chimney PDF Print E-mail
R-Energy Solutions For Africa's Electrification - Forms Of CSP Technology



Floating Solar Chimney: Except that the chimney (tower) is inflatable rather than a concrete it functions just the same way as solar updraft tower. The body of the floating solar Chimney is made of successive toroidal tubes filled with lighter than air gas such as Helium or Nitrogen. Floating Solar Chimney power plant is also known as Solar Aero-Electric Power Plant (SAEPP) due to its similarity to Hydro-Electric Power plants. Driven by the premise of cost reduction through light chimney structures, Prof. Papageorgiou invented a Floating Solar Chimneys
 

Technical and financial viability of Floating Solar Chimneys: According to cost estimate report by Floating Solar Chimney Technology Inc., floating solar chimney power Plant with a capacity of 100 MW (300 million KWh annually) with a floating Chimney of 2-3 km height and 50-85 m internal diameter and a solar collector with diameter of 2000m-3000m could cost about 35-70 million Euros. A wind farm of similar capacity 100 MW that produces an average of 250 million KWh annually, would cost about 100 million Euros. Floating Solar Chimney technology is therefore a very interesting option for renewable electricity generation.

SAEPP, equipped with low cost thermal storage facilities, can operate 24 hours/day for 365 days per year, producing a guaranteed Power profile. Thus SAEPP can replace conventional fuel consuming Power Plants.