Manikishore ppt

SOLAR POWERED STIRLING ENGINE

Presented by Manikishore

History of stirling engine and solar powered stirling engine.

Stirling engine was invented by ROBERT STIRLING on September 27,1816. A solar powered stirling engine was patented by Roelf J. Meijer in 1987.

What is stirling engine.

Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature level, such that there is a net conversion of heat energy to mechanical work.

The engine is designed so that the working gas is generally

compressed in the colder portion of the engine and expanded in the hotter portion resulting in a net conversion of heat into work. An internal Regenerative heat exchanger increases the Stirling engine's thermal efficiency compared to simpler hot air engines lacking this feature.

Operation of Stirling Engine. The stirling engine is a closed cycle it contains a fixed mass of

gas most commonly air, hydrogen or helium. This is accomplished by moving the gas back and forth

between hot and cold heat exchangers, often with a regenerator between the heater and cooler.

A change in gas temperature will cause a change in gas pressure, while the motion of the piston causes the gas to be alternately expanded and compressed.

When the gas is heated the pressure rises and this then acts on the power piston to produce a power stroke.

When the gas is cooled the pressure drops by the piston to compress the gas on the return stroke thus yielding a net power output.

Classifications of Stirling engine. There are three major types of Stirling engines :1. Alpha Type: Alpha Stirling contains two power pistons in separate cylinders, the

hot & cold cylinder, this type of engine has high power to volume ratio, but has technical problems due to high temp of the hot piston and durability of seals.

2. Beta Type: A beta Stirling has a single power piston arranged within the same cylinder on the same shaft as a displacer piston, When the working gas is pushed to the hot end of the cylinder it expands and pushes the power piston ,when it is pushed to cold end of the cylinder it contracts, the technical problem of alpha stirling is been overcomed by beta.

3. Gamma Type: A gamma Stirling is simply a beta Stirling in which the power piston is mounted in a separate cylinder alongside the displacer piston cylinder, but is still connected to the same flywheel. The gas in the two cylinders can flow freely between them and remains a single body. This configuration produces a lower compression ratio but is mechanically simpler.

Type1:Alpha type sterling engine Alpha type Sterling engine.

There are two cylinders. The expansion cylinder (red) is maintained at a high temperature

the compression cylinder (blue) is cooled.

The passage between the two cylinders contains the regenerator

Type 2:Beta type sterling engine

Beta Type Sterling Engine.

There is only one cylinder, hot at one end and cold at the other.

A loose fitting displacer shunts the air between the hot and cold ends of the cylinder.

A power piston at the end of the cylinder drives the flywheel

Type2:Gamma type sterling engine A gamma configuration Sterling engine design

Pink – Hot cylinder wall

Dark grey – Cold cylinder wall (with coolant inlet and outlet pipes in yellow)

Dark green – Thermal insulation separating the two cylinder ends

Light green – Displacer piston

Dark blue – Power piston

Light blue – Linkage crank and flywheels

BASICS OF STIRLING ENGINE WITH SOLAR

Solar energy is one of the more attractive renewable energy sources that can be used as an input energy source for heat engines. In fact, any heat energy source can be used with the Stirling engine

The solar radiation can be focused onto the displacer hot-end of the Stirling engine, thereby creating a solar-powered prime mover.

The direct conversion of solar power into mechanical power reduces both the cost and complexity of the prime mover.

History and Generation A solar powered stirling engine was invented by Roelf J. Meijer in

1987. His invention relates a heat engine, such as a Stirling cycle engine,

with a solar dish collector in order to produce electricity. The apparatus consists of a large dish aimed at the sun to reflect the

rays into the focus point, which is located at the centre of the dish. Solar energy is now collected in the form of heat to fuel a Stirling

cycle engine which operates by letting heat flow from a hot source to a cold sink in order to do work.

The work output of the stirling cycle is then used to drive a generator and create electric power.

Placed at the focus of a parabolic mirror a Stirling engine can convert solar Energy to electricity with efficiency better than non-concentrated photovoltaic cells. It generates electricity much more efficiently and economically than Photovoltaic (PV) systems with technology called concentrated solar power (CPS).

By making a mirror to focus the sun’s rays on the receiver end of a Stirling engine. The internal side of the receiver then heats hydrogen gas, which expands. The pressure created by the expanding gas drives a piston, crank shaft, and drive shaft assembly much like those found in internal combustion engines but without igniting the gas. The drive shaft is connected to a small electricity generator. A second type of solar powered stirling engine was patented by NASA on August 3, 1976 which employed the use of solar energy in order to freely pump water from a river, lake, or stream. The purpose of this apparatus is to “provide a low-cost, low-technology pump having particular utility in irrigation systems employed in underdeveloped arid regions of the earth,

SOALR STIRLING ENGINE

CONCENTRATING SOLAR PLANTS

Concentrating solar power plants uses parabolic trough collectors.

In parabolic trough system a parabolic shaped concentrator of aluminium is used. In the centre the received is placed.

In the central tower system many number of heliostat’s are arranged in pattern, such that the entire reflection of each heliostat is towards a central tower.

The central tower acts as a receiver.

EFFICIENCY

Theoretically Stirling engine efficiency = Carnot efficiency Unfortunately working fluid or gas is not ideal this

causes the efficiency to be lower than Carnot efficiency.

In fact, Stirling engine efficiency depends on Temperature ratio (proportionally) Pressure ratio (inversely proportional) Specific heat ratio (inversely proportional)

Advantages of solar stirling engine

The silence of operation.

Can run on any available heat source.

Supplying heat from continuous combustion process.

Some cases, allows the use of lightweight cylinders.

The engine mechanisms are simple in many ways.

Stirling engines are best for constant speed purpose.

Their maintenance cost is very low.

Disadvantages of solar stirling engine

The initial cost of the engine

It needs to warm up.

The problems of sealing.

Design complexity.

Some stirling engines are large for the amount of power that they produce.

Losses increased due to regenerator, heater and cooler.

THE SCOPE OF SOLAR STIRLING TECHNOLOGY

As we know that today the huge amount of world’s power is produced by the fossil fuels and that is also threaten to the environment.

Even the prices of power are increasing day by day due oil crises and also the trend of load shedding has been started.

So now the trend should be changed the technology has to be switched off instead of renewable energy resources.

The solar stirling technology is best option to produce maximum power to overcome energy crises.

The capital cost is high of this technology but the source of energy is free till the universe ends.

“Change is the only constant factor in the World”

THANK YOU.