Where can I get this info?

[JimL]

I've been Googling myself silly and can't find the answer to a relatively
simple question. At least I'm pretty sure it's an easy question for
SOMEBODY!

I've looked to find out how you sell electricity back into the grid.
Hundreds of web pages will tell you something like, "Well you fill out these
forms..."

No. How is it done?

Well, they use a generator or ..

No, no, no!

How do you put juice into the grid? How CAN you put juice into the grid?
Do you have to have a higher voltage so that it goes in the other direction?
How is it done? If somebody has a bunch of solar cells to feed into the
grid, why doesn't the incoming juice just burn out the inverter?

No doubt someone can sell you a bunch of stuff that will do the job at a
very high price, but I still want to know HOW it's done!

Where can I find that answer?

Thanks.

 

[Gerard Bok]

I've looked to find out how you sell electricity back into the grid.

How do you put juice into the grid? How CAN you put juice into the grid?

First of all, you need a controller and a converter. Your basic
solar cells provide low voltage DC. You can run an Ipod from
them, but that's usually not the aim.
So, for domestic use, the DC from the solarcells is fed to a
converter that produces 115 Volt at 60 Hz or 230 Volt at 50 Hz,
just like the local grid does. As long as you run a separate load
from your solar cells, that's where the story ends.

Mostly, you will run in a hybride mode. Part of the energy you
consume comes from the grid, the other part from your roof.
That requires both supplies to be in perfect sync, both voltage,
frequency and phase wise. That's where the controller comes into
action. You cannot force the grid to sync with your converter, so
your converter will need to sync with the grid

Do you have to have a higher voltage so that it goes in the other direction?

No. You are basically paralleling powersupplies. You are not
really powering the grid. Both the grid and your converter are
sharing (a very minor part of) the grid's load.

How is it done? If somebody has a bunch of solar cells to feed into the
grid, why doesn't the incoming juice just burn out the inverter?

A solar cell is like a battery. As long as you do not connect a
lamp, the power just keeps waiting for you inside. (That is, as
long as the sun shines

Where can I find that answer?

No doubt, on the internet

 

[JimL]

First of all, you need a controller and a converter. Your basic
solar cells provide low voltage DC. You can run an Ipod from
them, but that's usually not the aim.
So, for domestic use, the DC from the solarcells is fed to a
converter that produces 115 Volt at 60 Hz or 230 Volt at 50 Hz,
just like the local grid does. As long as you run a separate load
from your solar cells, that's where the story ends.

Mostly, you will run in a hybride mode. Part of the energy you
consume comes from the grid, the other part from your roof.
That requires both supplies to be in perfect sync, both voltage,
frequency and phase wise. That's where the controller comes into
action. You cannot force the grid to sync with your converter, so
your converter will need to sync with the grid


No. You are basically paralleling powersupplies. You are not
really powering the grid. Both the grid and your converter are
sharing (a very minor part of) the grid's load.


A solar cell is like a battery. As long as you do not connect a
lamp, the power just keeps waiting for you inside. (That is, as
long as the sun shines


No doubt, on the internet

Nice overview of solar cell use as long as the sun shines. But whether by
one production method or another, people DO sell power to the power company.
I know that is a fact.

 

[Jon Danniken]

Nice overview of solar cell use as long as the sun shines. But
whether by one production method or another, people DO sell power to
the power company. I know that is a fact.

It's like Gerald spoke of as a parallel power supply. Your 120/240 service
comes from a generation plant, and is stepped up to hundreds of thousands
(or millions) of volts. By the time it gets to the transformer nearest your
house, it is at maybe a few thousand volts.

The transformer nearer your house steps this voltage down to the 120/240 you
know. That service comes to your house and goes to a meter, which measures
the power (in Watts) that you consume.

That meter can also run backwards.

The transformer nearest to your house can also run backwards (as can all
transformers).

When you run a generator/solar controller/power supply of your own, and you
produce excess power, that excess power travels through your electric meter
(which reverses, and reduces your charge), and continues on to the
transformer nearest your house, where it provides a magnetizing current in
that transformer.

That magnetizing current in the transformer steps up the voltage to whatever
thousands of volts is used locally. Since there are other customers for
those thousands of volts, that magnetizing current provides a power source
for the load on the high voltage terminal on the transformer.

That magnetizing current you are providing is what is considered the energy
you are "giving back" (minus losses, but I don't know if they calculate for
that, probably not).

The point here is that you are just another addition point to the grid. The
grid does not consist of one power generation plant and a number of
consumers, the grid does consist of multiple power generation plants
interconnected in a grid fashion to all of the consumers.

You are, essentially, just becoming another power generation plant on the
grid, albeit a small one.

Jon

 

[Gerard Bok]

That meter can also run backwards.

When you run a generator/solar controller/power supply of your own, and you
produce excess power, that excess power travels through your electric meter
(which reverses, and reduces your charge),

Well, that would be very nice ;-)
Maybe, somewhere in a perfect world, things would work that way.

Overhere (the Netherlands, but the same system is in practice
elsewhere in Europe), things work differently.
The power company places 2 meters. One measures energy that flows
from their network into the user's premisses. As always.
Another one measures energy supplied back into the grid.
(While they charge say 25 cts for the current they supply, they
only reimburse you with say 3 cts for the reverse supply.)

There are several 'good reasons'. But it makes it virtually
impossible to operate a solar panel in an economic viable way,
unless you can use the generated power almost entirely by
yourself. (Or the government pays huge grants for solar power
installation, as is common in many countries now.)

 

[JimL]

It's like Gerald spoke of as a parallel power supply. Your 120/240
service comes from a generation plant, and is stepped up to hundreds of
thousands (or millions) of volts. By the time it gets to the transformer
nearest your house, it is at maybe a few thousand volts.

The transformer nearer your house steps this voltage down to the 120/240
you know. That service comes to your house and goes to a meter, which
measures the power (in Watts) that you consume.

That meter can also run backwards.

The transformer nearest to your house can also run backwards (as can all
transformers).

When you run a generator/solar controller/power supply of your own, and
you produce excess power, that excess power travels through your electric
meter (which reverses, and reduces your charge), and continues on to the
transformer nearest your house, where it provides a magnetizing current in
that transformer.

That magnetizing current in the transformer steps up the voltage to
whatever thousands of volts is used locally. Since there are other
customers for those thousands of volts, that magnetizing current provides
a power source for the load on the high voltage terminal on the
transformer.

That magnetizing current you are providing is what is considered the
energy you are "giving back" (minus losses, but I don't know if they
calculate for that, probably not).

The point here is that you are just another addition point to the grid.
The grid does not consist of one power generation plant and a number of
consumers, the grid does consist of multiple power generation plants
interconnected in a grid fashion to all of the consumers.

You are, essentially, just becoming another power generation plant on the
grid, albeit a small one.

Jon

I've known all this stuff for years - many years. And it is precisely the
kind of generalities I found on the internet. I guess the answer to my
actual question of HOW is to merely to start up a generator and plug it's
output into a hot outlet. If the sparks fly and the wires melt down I'll
know that is wrong.

Thanks

 

[Jon Danniken]

I've known all this stuff for years - many years. And it is
precisely the kind of generalities I found on the internet. I guess
the answer to my actual question of HOW is to merely to start up a
generator and plug it's output into a hot outlet. If the sparks fly
and the wires melt down I'll know that is wrong.

It sounds like your real problem is figuring out how to properly phrase a
question which will lead to the information you are looking for.

I might suggest your local community college, perhaps the writing department
could recommend the proper class.

Jon

 

[Gerard Bok]

I guess the answer to my
actual question of HOW is to merely to start up a generator and plug it's
output into a hot outlet.

The key is, exact synchronisation of voltage, frequency and
phase. If you 'just plug it in', firework is inevitable.

The basic rule reads: you cannot parallel powersupplies.
(Unless .....)

 

[JimL]

It sounds like your real problem is figuring out how to properly phrase a
question which will lead to the information you are looking for.

I might suggest your local community college, perhaps the writing
department could recommend the proper class.

Jon

How would you phrase it?

 

[JimL]

"Where can I buy a converter that will support my specific
power generating components in order to facilitate my
selling power back to the local electric company?"

Of course you have to know you need something named a "converter" before you
can ask about one, now don't you.

So how would you phrase it if you didn't already know the answer?

 

[pimpom]

The key is, exact synchronisation of voltage, frequency and
phase. If you 'just plug it in', firework is inevitable.

That's correct. I had no trouble understanding what the OP wanted
to know, but didn't reply because I don't know a simple
practicable way of doing it.

The AC voltage from the solar power must fluctuate at exactly the
same rate as the mains grid (frequency synchronisation), the
up-down variation must occur at the same time and direction
(phase sync), and the voltage and waveform must be the same (a
simple square wave from the solar generator will not do). In
addition, internal resistances must also be considered, otherwise
whichever source has the lower resistance will try to supply more
power than the other. And if the solar generator has a lower
effective resistance.............

The basic rule reads: you cannot parallel powersupplies.
(Unless .....)

Unless...... you install some device that automates the
synchronisation process and relative power load. I have no idea
if the OP's power company will supply such a device or if it can
be bought for a reasonable price. I've been out of touch with the
field for a long time.

I'm a self-taught electronics tech in an isolated part of India.
Decades ago, engineers of our state's power department used to
call on me to help with technical problems. In those days, rural
areas were supplied with power from local 300 kW diesel
generators. When demand exceeded the capacity of one generator,
they paralleled two or more. Synchronisation was done in a crude
but effective manner. Frequency was monitored with a series of
vibrating reeds, voltage with analog panel meters, and phase sync
with an incandescent lamp between two generators. One generator
(alternator) was run up to the proper frequency and voltage, and
the other's engine was slowly adjusted until they matched for
voltage, frequency and phase. Then a technician switched the
generators to a common power bus. Synchronising aids became
available later on and, in any case, local generators were
gradually phased out.

The answer to the OP's project is the same in principle. But he's
talking about contributing a miniscule amount to a much, much
more powerful grid, and such a crude, manual method of
synchronisation is simply not practical..

 

[Paul]

Of course you have to know you need something named a "converter" before you
can ask about one, now don't you.

So how would you phrase it if you didn't already know the answer?

We're taught how to make hot connections to the grid, in
engineering (power systems). One of our labs involved
connecting a motor generator set to the grid. In the
case of that crude electromechanical system, we used
light bulbs and the beat frequency between the
two systems, to judge when to close the switch.
As long as the systems are synced and there is no
potential difference, when the switch is closed,
the motor generator hardly responds mechanically (which
tells you there is no net power transfer).

If you make a mistake, you can actually shake or rock
the motor generator set on its mounts. So when students
are doing that lab, they cannot afford to do the exact
opposite of what the instructions say. Connecting the
generator to the grid when the generator is out of phase
with respect to the grid, causes a nasty reaction. The
sound of protest coming from your rig, tells you
you've screwed up.

Our motor generator was a bit bigger than this.

http://www.frontierpower.com/gensets/motorgen.htm

*******

The inverter on the solar collector or window power system,
is intelligent, and can vary the voltage or frequency, just
like a real power plant on the grid. With the right relationship,
AC current flows "out of" the house connection and back into
the grid. If the electric meter is digital (as mine is on the
side of the house now), the digital meter can measure flow
in either direction and total it up. My meter sends readings
every 15 minutes or so, via wireless piconet. Or so it is claimed.
I haven't seen a physical meter reader in a couple years,
so I assume it is all working.

Here is an example of some chatter, between individuals
discussing the connection of a city run power generation system,
to a grid.

http://www.control.com/thread/1241213442

And this is the project in question. This is what they were
connecting to the grid. (You'd need a recent version of
Acrobat Reader, to read this.) About a 5 MB document.

http://www.ciandservice.com/media/CIS$20Case$20Study$20-$20Power$20Generation.pdf

In the case of solar, the inverter is there, to convert
DC from the solar panels, into AC at the same frequency
as the grid. It will adjust its output voltage and phase
automatically, and will only "push" as much electricity
into the grid, as the DC source (solar panels) will allow.
If you overload the solar panels, I presume the terminal
voltage will start to drop. So the controller on
the inverter is tasked with finding the "sweet spot",
of loading the solar panels as efficiently as possible (max V*I),
maximizing the extracted energy, and pushing the energy
in the form of AC, back into the grid. "Pushing" being
a figurative term - when the voltage and phase are
adjusted properly, there is power transfer which the
inverter can measure and monitor. It can do this,
until the ratings of the pole transformer are exceeded,
(which isn't too likely).

There is a picture of an inverter box on this web page.
This system is handling 3.5KW or so.

http://solar.hmtech.info/

If you were doing wind power, there is a possibility the
wind generator has an AC output. Here is a company using some kind of
switching technology (Insulated Gate Bipolar Transistor or
IGBT) as part of their conversion solution. If the generator
in a wind power unit is not synced to the grid, then
that makes it more likely something like AC-DC-AC (double
conversion) is required. Thinking in simple terms,
you could do the AC-DC step with rectifiers, and
the DC-AC step with an inverter. The scheme they
claim to use here, is more complicated than that.

http://www.phasetechnologies.com/windconverter/

The power company is not likely to allow you to do
all the work yourself, so at some point, a professional
who knows what kind of conversion is required, will be
involved. Even when automated systems are involved,
there are still opportunities for smoke or blown
fuses. So the systems still need to be protected
against switching transistor failures and the like.
No different, than protecting you from a failure
inside your computer's power supply.

Paul

 

[JimL]

We're taught how to make hot connections to the grid, in
engineering (power systems). One of our labs involved
connecting a motor generator set to the grid. In the
case of that crude electromechanical system, we used
light bulbs and the beat frequency between the
two systems, to judge when to close the switch.
As long as the systems are synced and there is no
potential difference, when the switch is closed,
the motor generator hardly responds mechanically (which
tells you there is no net power transfer).

If you make a mistake, you can actually shake or rock
the motor generator set on its mounts. So when students
are doing that lab, they cannot afford to do the exact
opposite of what the instructions say. Connecting the
generator to the grid when the generator is out of phase
with respect to the grid, causes a nasty reaction. The
sound of protest coming from your rig, tells you
you've screwed up.

Our motor generator was a bit bigger than this.

http://www.frontierpower.com/gensets/motorgen.htm

*******

The inverter on the solar collector or window power system,
is intelligent, and can vary the voltage or frequency, just
like a real power plant on the grid. With the right relationship,
AC current flows "out of" the house connection and back into
the grid. If the electric meter is digital (as mine is on the
side of the house now), the digital meter can measure flow
in either direction and total it up. My meter sends readings
every 15 minutes or so, via wireless piconet. Or so it is claimed.
I haven't seen a physical meter reader in a couple years,
so I assume it is all working.

Here is an example of some chatter, between individuals
discussing the connection of a city run power generation system,
to a grid.

http://www.control.com/thread/1241213442

And this is the project in question. This is what they were
connecting to the grid. (You'd need a recent version of
Acrobat Reader, to read this.) About a 5 MB document.

http://www.ciandservice.com/media/CIS$20Case$20Study$20-$20Power$20Generation.pdf

In the case of solar, the inverter is there, to convert
DC from the solar panels, into AC at the same frequency
as the grid. It will adjust its output voltage and phase
automatically, and will only "push" as much electricity
into the grid, as the DC source (solar panels) will allow.
If you overload the solar panels, I presume the terminal
voltage will start to drop. So the controller on
the inverter is tasked with finding the "sweet spot",
of loading the solar panels as efficiently as possible (max V*I),
maximizing the extracted energy, and pushing the energy
in the form of AC, back into the grid. "Pushing" being
a figurative term - when the voltage and phase are
adjusted properly, there is power transfer which the
inverter can measure and monitor. It can do this,
until the ratings of the pole transformer are exceeded,
(which isn't too likely).

There is a picture of an inverter box on this web page.
This system is handling 3.5KW or so.

http://solar.hmtech.info/

If you were doing wind power, there is a possibility the
wind generator has an AC output. Here is a company using some kind of
switching technology (Insulated Gate Bipolar Transistor or
IGBT) as part of their conversion solution. If the generator
in a wind power unit is not synced to the grid, then
that makes it more likely something like AC-DC-AC (double
conversion) is required. Thinking in simple terms,
you could do the AC-DC step with rectifiers, and
the DC-AC step with an inverter. The scheme they
claim to use here, is more complicated than that.

http://www.phasetechnologies.com/windconverter/

The power company is not likely to allow you to do
all the work yourself, so at some point, a professional
who knows what kind of conversion is required, will be
involved. Even when automated systems are involved,
there are still opportunities for smoke or blown
fuses. So the systems still need to be protected
against switching transistor failures and the like.
No different, than protecting you from a failure
inside your computer's power supply.

Paul

Excellent. Thanks.

 

[JimL]

That's correct. I had no trouble understanding what the OP wanted to know,
but didn't reply because I don't know a simple practicable way of doing
it.

The AC voltage from the solar power must fluctuate at exactly the same
rate as the mains grid (frequency synchronisation), the up-down variation
must occur at the same time and direction (phase sync), and the voltage
and waveform must be the same (a simple square wave from the solar
generator will not do). In addition, internal resistances must also be
considered, otherwise whichever source has the lower resistance will try
to supply more power than the other. And if the solar generator has a
lower effective resistance.............

Unless...... you install some device that automates the synchronisation
process and relative power load. I have no idea if the OP's power company
will supply such a device or if it can be bought for a reasonable price.
I've been out of touch with the field for a long time.

I'm a self-taught electronics tech in an isolated part of India. Decades
ago, engineers of our state's power department used to call on me to help
with technical problems. In those days, rural areas were supplied with
power from local 300 kW diesel generators. When demand exceeded the
capacity of one generator, they paralleled two or more. Synchronisation
was done in a crude but effective manner. Frequency was monitored with a
series of vibrating reeds, voltage with analog panel meters, and phase
sync with an incandescent lamp between two generators. One generator
(alternator) was run up to the proper frequency and voltage, and the
other's engine was slowly adjusted until they matched for voltage,
frequency and phase. Then a technician switched the generators to a common
power bus. Synchronising aids became available later on and, in any case,
local generators were gradually phased out.

The answer to the OP's project is the same in principle. But he's talking
about contributing a miniscule amount to a much, much more powerful grid,
and such a crude, manual method of synchronisation is simply not
practical..

Thanks. Interesting that the square wave won't work.

I'm thinking someone had to watch those engines pretty closely for rpm
drift.

 

[Sjouke Burry]

Thanks. Interesting that the square wave won't work.

I'm thinking someone had to watch those engines pretty closely for rpm
drift.

Once running, you dont have to do much watching, when power
changes, the phase angle changes, and more power goes to the net,
slowing the generator, and decreasing phase.
It is more or less self-regulating.
In the dark ages, they had 3 lamps between the 3 phases of the net
and the generator, they had the generator speed up, until the lamps
showed the same speed.
When the lamps also faded out, the phase was also oke, and the generator
was switched onto the net, and self-regulation took over.
After that,just up the steam and power, sync is maintained.

 

[JimL]

Not really, what you need is a plan.

You need to detail what you use to generate power, then
based on the parameters of that, you pick the appropriate
converter.

There are power converters for most possible scenarios, but
to pick one you have to have a starting point, what the
input power is which is determined by our choice of what
solar, wind, etc, components you use.

Thanks, but no need. I have no electricity to sell. As I tried to indicate
as we went along, it was all a matter of theoretical curiosity. (Someone
has suggested in another thread, maybe another NG, that I don't want to
learn. In fact I want to learn everything in sight.) I have no solar
cells, no generator big enough to consider, no wind turbines. This is why I
can only ask about it and give utterly no details - the food upon which
answer givers live. <g>

Perhaps I will eventually learn never to ask general questions when so many
are primed to zero in on specific items of hardware which, in turn, require
lengthy and carefully worded explanations of detail.

I have my answer, thanks to people who had no problem understanding my
question. It is basically a direct connection - made possible only by
carefully matching waves using synchronizing equipment. Early on I said it
was probably a simple answer for someone. I was right. I just put it in
one sentence.

Thanks

 

[JimL]

Once running, you dont have to do much watching, when power
changes, the phase angle changes, and more power goes to the net,
slowing the generator, and decreasing phase.
It is more or less self-regulating.

It's easy when you know how! <G>

Thanks

 

[pimpom]

Thanks. Interesting that the square wave won't work.

That's because alternating voltages from two sources with
dissimilar waveforms will have the same value at only a few
points in the AC cycle, and will be out of sync at all other
points. This means that there will be a potential difference
between the two sources most of the time, causing a circulating
current. Circulating current is wasteful and can even be
damaging.

 

[JimL]

this is the wrong NewsGroup,

Did you happen to notice the title of the thread? Are you badly upset
because some people were helpful?

the OP should try his question over at:
"alt.energy.homepower"

Thank you.

 

[JimL]

Your questions are like asking "how would you know to ask
how to find a car if you didn't know it was called a car?"

Perhaps if you were buying a car you'd have enough money to just run out and
start spending.

The answer is to describe your intentions to those you ask

Boy, you _really_ want this to be a problem don't you?