Question

Describe the principles and operations of four types of concentrating solar power (CSP) technologies using a systems diagram and discuss any potential environmental implications of concentrating solar power systems. Please include appropriate references to support your argument?

Answer 1

Introduction

Concentrating solar power (CSP) is the power generated in solar power systems that use solar concentrators to convert solar energy into heat and then the produced heat is converted into power. CSP systems use very different technology thanphotovoltaic (PV) systems. They use the sun as heat energy source instead of the photon energy of the sun used by PV systems. CSP plants use mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. Electricity is generated when the concentrated light drives a heat engine, usually a steam turbinecycle, connected to an electrical power generator. The thermal energy concentrated can be stored and used to produce electricity when it is needed. Most power plants use solar concentrator together with some form of fossil fuel burners to increase the amount of thermal heat source.

The four main types of solar concentrator systems are parabolic trough, power tower,linear Fresnel, and dish. All of them use thermal energy from the sun to generate mechanical energy in a heat engine to drive electrical generator do produce electricity. The dish concentrates thermal energy, generally used in Stirling engine systems. The parabolic trough, linear Fresnel, and power tower are technologies for CSP systems based on Brayton or Rankine cycles. The basic and general process for conversion of solar thermal energy to electric energy in the concentrated power plants.

Energy is recovered by solar collectors, which are mechanical devices that capture radiant solar energy and convert it to useful thermal energy. This energy can be stored (if appropriate or required) and converted to satisfy electricity, thermal, or mechanical energy demands. Different types of solar collectors can be applied, depending on the application.

There are nonconcentrating and concentrating types of solar collectors. The former uses the same area to intercept and absorb solar radiation. However, theconcentrating solar collectors used in CSP plants usually have concave reflecting surfaces to intercept and concentrate solar radiation into a small receiving area, thereby increasing radiation flow. Parabolic troughs, solar towers in heliostat field, linear Fresnel reflectors (LFRs), and parabolic dishes (PDs) are the main technologies used in the concentrating solar thermal power plants, due to the production of high-temperature.

*FOUR TYPES OF CSP.

1.linear Fresnel

A compact linear Fresnel reflector (CLFR) – also referred to as a concentrating linear Fresnel reflector – is a specific type of linear Fresnel reflector (LFR) technology. They are named for their similarity to a Fresnel lens, in which many small, thin lens fragments are combined to simulate a much thicker simple lens. These mirrors are capable of concentrating the sun's energy to approximately 30 times its normal intensity.

Linear Fresnel reflectors use long, thin segments of mirrors to focus sunlight onto a fixed absorber located at a common focal point of the reflectors. This concentrated energy is transferred through the absorber into some thermal fluid (this is typically oil capable of maintaining liquid state at very high temperatures). The fluid then goes through a heat exchanger to power a steam generator. As opposed to traditional LFR's, the CLFR utilizes multiple absorbers within the vicinity of the mirrors.

2).Parabolic trough

A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The sunlightwhich enters the mirror parallel to its plane of symmetry is focused along the focal line, where objects are positioned that are intended to be heated. In a solar cooker, for example, food is placed at the focal line of a trough, which is cooked when the trough is aimed so the Sun is in its plane of symmetry.

For other purposes, a tube containing a fluid runs the length of the trough at its focal line. The sunlight is concentrated on the tube and the fluid heated to a high temperature by the energy of the sunlight. The hot fluid can be piped to a heat engine, which uses the heat energy to drive machinery, or to generate electricity. This solar energy collector is the most common and best known type of parabolic trough.

When heat transfer fluid is used to heat steam to drive a standard turbine generator, thermal efficiency ranges from 60-80%. The overall efficiency from collector to grid, i.e. (Electrical Output Power)/(Total Impinging Solar Power) is about 15%, similar to PV (Photovoltaic Cells) but less than Stirling dish concentrators. Large-scale solar thermal power plants need a method for storing the energy, such as a thermocline tank, which uses a mixture of silica sand and quartzite rock to displace a significant portion of the volume in the tank. It is then filled with the heat transfer fluid, typically a molten nitrate salt.

3)power tower Systems:

Power tower or central receiver systems utilize sun-tracking mirrors called heliostats to focus sunlight onto a receiver at the top of a tower. A heat transfer fluid heated in the receiver up to around 600ºC is used to generate steam, which, in turn, is used in a conventional turbine-generator to produce electricity.

The earliest power towers utilized steam as the heat transfer fluid, which does not lend itself to storage.A great deal of research is investigating various other heat transfer or energy storage materials because of potential to attain higher temperature with resulting efficiency gains leading to lower costs. These possible energy storage materials range from air to sand particles, to alternative mixtures of chemicals..

4) parabolicDish Systems:

A Parabolic dish system consists of a parabolic-shaped point focus concentrator in the form of a dish that reflects solar radiation onto a receiver mounted at the focal point. These concentrators are mounted on a structure with a two-axis tracking system to follow the sun. The collected heat is typically utilized directly by a heat engine mounted on the receiver moving with the dish structure. Dish can attain extremely high temperatures, and holds promise for use in solar reactors for making solar fuels which require very high temperatures. Stirling and Brayton cycle engines are currently favored for power conversion, although dish has been seldom deployed commercially for power generation