SOLAR POWERED STIRLING ENGINE
History of stirling engine and solar powered
Stirling engine was invented
by ROBERT STIRLING on
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
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
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)
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
A power piston at the end of the
cylinder drives the flywheel
Type2:Gamma type sterling engine
A gamma configuration Sterling
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
The solar radiation can be focused onto the displacer hot-end
of the Stirling engine, thereby creating a solar-powered prime
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
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
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
CONCENTRATING SOLAR PLANTS
Concentrating solar power plants uses parabolic
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
The central tower acts as a receiver.
Stirling engine efficiency = Carnot efficiency
Unfortunately working fluid or gas is not ideal
this causes the efficiency to be lower than
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.
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
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