Stirling engine : bonne explication ici (Baxi) min. 1:26 à 1:50

1.  Baxi Ecogen (4:37)
2. How the Baxi Ecogen works (1:58)
(This short film explains exactly how the Baxi Ecogen dual energy system, or micro-combined heat and power boiler, actually works. Using a cut-away model, Dave Willetts from Baxi’s R&D Department in Preston, which is Baxi’s European Centre of Excellence for micro-CHP, explains how electricity is generated in this wall hung replacement for a conventional domestic boiler.)

3. How does the Flow Boiler work ?

transcriptions ci-dessous.

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Micro combined heat and power
Micro-generation technologies
Micro CHP products
Flow Boiler (pub)

You might also be interested in:
– the microCHP hub (the whole site is full of interesting articles on renewable energy !)
– How Stirling engines work
– The BedZed project  (Beddington Zero Energy Development (BedZED) is an environmentally friendly housing development in the suburbs of London. The project is designed to use only energy from renewable sources generated on site. There are 777 square metres  of solar panels. Tree waste fuels the development’s cogeneration plant (downdraft gasifier) to provide district heating and electricity.)

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TRANSCRIPTS

1.  Baxi Ecogen

Climate change is real
and it is affecting life on every continent.
The evidence is conclusive :
globally the ten hottest years on record
have all happened since the beginning of the 1990s.
Greenhouse gas emissions caused by our activity are harming the planet
and have the potential to damage it beyond repair.
Along with the serious threat posed by climate change,
our planet is also rapidly running out of the natural resources that we all depend upon.

0:36 It’s time to act,
and the best place to start helping the planet is right here, at home.
The way we heat and light our homes at present is just not efficient enough.
Only around 30 percent of the fuel used to generate electricity at the power station
is actually converted into energy.

1:00 But more than 90 percent of the fuel used in Baxi Ecogen
will generate heat and electricity for the average home.
Baxi is an innovative company,
responsive to the changing world we live in.
We’re developing ways to improve energy efficiency
including fuel cells, internal combustion engines,
and external combustion engines like the Stirling engine.

1:30 The Stirling engine is very efficient, clean, and reliable.
It’s also the technology behind Baxi’s Ecogen boilers.
Baxi Ecogen converts the energy stored in the gas supplied to homes
into electricity and heat.
Here’s how the Baxi Ecogen system works.

1:54 Outside, it looks like a standard wall-hung boiler,
but inside it’s something altogether different.
The advanced electronic control system
allows the unit to modulate down to a very low thermal output
while still generating electricity.
Behind the cover is a boiler configuration that’s entirely new
but based upon tried proven technology.
Everything is managed by the electronic control unit,
from the volume of air and gas supplied
to switching on and off.

2:26 The spool valve* controls the air and gas supply.
The engine burner delivers precisely controlled heat
to elevate the temperature of the top of the engine compartment
to approximately 525°C.
The hermetically sealed Stirling engine generates the electricity.
At its heart is a displacer** (and ??) piston.
This is driven up and down at 50 cycles per second between electrical coils
to generate a current.

2:54 The engine can deliver up to 6 kW of thermal output on its own,
but it’s also supported by a supplementary heat exchanger,
giving an extra thermal output. (18 kW)
In standard mode, the engine burner operates first,
with the supplementary engine firing into action
only when the heat demand goes above 6 kW.
Cold water from the domestic supply
goes into the unit and picks up some initial heat
by flowing around the engine.
It then flows up to the supplementary heat exchanger
picking up more heat before flowing out of the unit.

3:28 The 1 kW of electrical output generated by the Stirling engine
can either be used in the home to reduce consumption
or exported back to the grid for an export tariff.
(NB : in the US this is referred to as net metering)

3:51 Baxi has an unparalleled combination of knowledge and experience
in developing, manufacturing and servicing home heating systems.
We are pioneers in a business
that will have major impact on the future of the planet.
With Baxi Ecogen we can all make a difference.

* spool valve : distributeur (?)
** displacer : see here (Stirling engines for microCHP generators)
Description of the Baxi Ecogen system : here.

2.  How the Baxi Ecogen works

So this is a cutout (= cutaway ?) of the Ecogen unit
which helps to explain its operation.
The Ecogen unit is basically internally split into two areas :
The Stirling engine, which is the generator at the bottom,
and provides 6kW of thermal energy,
and the supplementary heat exchanger at the top,
which provides 18 kW of heat.

0:21 Gas enters the Ecogen unit at the bottom, through this pipe,
and is then distributed between two burners :
one for the Stirling engine, and one for supplementary heating.
Hot water leaves the Ecogen at the flow pipe here,
and travels to the central heating and domestic hot water system.
It then returns from the domestic hot water and central heating system through this pipe
and enters the Stirling engine here,
where it cools the bottom of the Stirling engine head.

0:51 The top of the Stirling engine head is heated by this burner here.
It’s that difference in temperature
which creates an oscillating pressure wave
and drives the power piston here.
This displacer piston
is moving the gas between the hot(s) and the cold end of the engine.
So when the displacer piston’s at the bottom of its stroke,
most of the gas is at the top end of the engine here and being heated.

1:18 That heat causes the gas to expand.
It moves the power piston down to displace a piston(s) on a spring.
As it returns to the top of the Stirling engine,
most of the helium gas is in this area here and is being cooled.
This causes the gas to contract
and pulls the power piston upwards.

1:37 It’s this movement of the power piston up and down
that moves these fixed magnets here,
as a result (they) move within this copper coil 50 times a second,
inducing an electromagnetic field and generating 1 kW of electricity.
This is then returned via this cable into your home
and on to the national grid.

3. How the Flow boiler works

From the outside,
the Flow Microgeneration boiler looks like any other boiler.
It has the same shape and the same size.
It’s only inside that it’s special.
The Flow boiler employs innovative technology
to generate low cost, low carbon electricity
while it uses gas to heat your home.
The clever engineers at Flow have used the finest quality parts and materials
sourced from the very best European manufacturers
and configured them in a novel way
in our state-of-the-art manufacturing facility in Livingston, Scotland,
to produce the world’s first affordable electricity-generating boiler.

0:35 The Flow boiler is unique, and it’s patented worldwide.
You can’t get a boiler like this anywhere else.
So here’s how the Flow boiler works.
Gas burns in the combustion chamber just like a normal boiler,
but instead of directly heating water for your heating and hot water tank,
this heats up a liquid within the boiler.
As the liquid is heated, it evaporates.
The resulting vapour moves to a device called a scroll expander.
As the vapour moves through the scroll,
it causes it to spin.
At this point the scroll is acting like a mini generator, or dynamo.

1:10 This is how the Flow boiler generates electricity.
The electricity can then be used in your home
or exported to the national grid for other households to use.
The vapour that causes the scroll to spin and generate electricity
then enters a small heat exchanger
and condenses back into a hot liquid
which heats water for your heating system and hot water tank.
The liquid is then pumped around to be heated and evaporated again,
continuously converting heat from the burned gas
into electricity and heat for your home.

1:40 So that’s it : the unique Flow boiler,
intelligently engineered by the clever people here at Flow.
The Flow boiler launches in January 2015.
Our launch version is suitable for 3 to 5-bedroom houses
and needs a separate hot water tank.
But our team are working on versions for smaller houses and for bigger houses,
and they’re creating a combi version too.
So register your details now,
and you can be part of the most exciting vision for home energy
that has ever been.

Description of the Flow boiler : here.