Government offer of *feed-in tariff of 60 cents per kilowatt hour (kWh)*

[?]

Government offer of *feed-in tariff of 60 cents per kilowatt hour (kWh)*

I'm a bit confused about the government offer of paying the owners of solar
photovoltaic (PV) systems who put power back into the grid.

Is this at all possible in the real world?

When you consider the power losses within the cables and other
infrastructure on the electricity grid.

Does an array of solar photovoltaic generate *enough power* to feed any
*useful* energy back into the grid?

 

[Sylvia Else]

Government offer of *feed-in tariff of 60 cents per kilowatt hour (kWh)*

I'm a bit confused about the government offer of paying the owners of solar
photovoltaic (PV) systems who put power back into the grid.

Is this at all possible in the real world?

Depends what you mean by possible. In a world inhabited by beings with a
solid understanding of economics, no such scheme would ever be
constructed. However, we don't live in such a world. Instead we live in
a world where decisions are made based not on sound economics, but short
term political expediency. In such a world, yes, it's possible.

Though given your comments below, I suspect you meant technically.

When you consider the power losses within the cables and other
infrastructure on the electricity grid.

Does an array of solar photovoltaic generate *enough power* to feed any
*useful* energy back into the grid?

The grid isn't that inefficient.

But it doesn't matter anyway. Power you generate will likely be consumed
by people in the same street, and reduce the power that has to be
transmitted through the grid.

Sylvia.

 

[?]

Depends what you mean by possible. In a world inhabited by beings
with a solid understanding of economics, no such scheme would ever be
constructed. However, we don't live in such a world. Instead we live
in a world where decisions are made based not on sound economics, but
short term political expediency. In such a world, yes, it's possible.

Though given your comments below, I suspect you meant technically.


The grid isn't that inefficient.

But it doesn't matter anyway. Power you generate will likely be
consumed by people in the same street, and reduce the power that has
to be transmitted through the grid.

Sylvia.

Thanks Sylvia,

Has anyone actually crunched the numbers to prove this is viable even with
the limited inefficiencies, and there is a *net gain* in power?

Or is it just a political stunt to get more people to take up solar photovoltaic cells,
i.e. get on the green bandwagon, save the planet, stimulate the economy etc...

Will the net gain be a benefit to only the immediate neighbors who are there to consume
It , or is of benefit to everyone on the grid?

Also, what if there is *excess* power produced by streets of houses with
solar photovoltaic cells, where is all that *surplus* energy stored??

 

[Sylvia Else]

Thanks Sylvia,

Has anyone actually crunched the numbers to prove this is viable even with
the limited inefficiencies, and there is a *net gain* in power?

I'm sure there's a net gain. Not only is the power produced by the PV
cells being consumed in the neighbourhood, but the grid losses, such as
they are, are obviated because that power doesn't have to pass over the
grid.

Or is it just a political stunt to get more people to take up solar photovoltaic cells,
i.e. get on the green bandwagon, save the planet, stimulate the economy etc...

Will the net gain be a benefit to only the immediate neighbors who are there to consume
It , or is of benefit to everyone on the grid?

Now you get in the murky area of the definition of benefit. The total
power available is increased, at the instant it's produced, but except
in very unusual circumstances, it's not power that would otherwise have
been unavailable (which would have let to power cuts). All the PV cells
are doing is reducing the production of power by the existing generation
plant with the highest marginal cost (typically gas or oil). The only
benefit is the elimination of the CO2 that would have been produced by
that other plant. Whether that elimination is a real benefit is a
separate argument.

solar photovoltaic cells, where is all that *surplus* energy stored??

Well, that won't happen. Even in a green politician's wildest dreams,
there's simply not going to be anything like enough PV output from
domestic rooftops to meet the entire power load during the day.

That aside, where is surplus energy stored? For the most part, we have
no practical way of storing energy on this sort of scale. There is a
small capacity to pump water from the lower side of hydroelectric plants
to the high side, and the energy, or most of it anyway, can later be
recovered by operating the hydroplant. Of course, this presupposes that
the hydro plant doesn't have enough reserve to have operated anyway.

This scheme is used, as are some compressed air storage systems, but
they are limited by the need to have suitable places to build them.
There are a few other mechanisms, but none have a major impact. But
these schemes would never be used to store the energy produced by PV
cells. It wouldn't be economically worthwile. Where they are used, it's
to store energy produced cheaply overnight from coal or nuclear so that
it can be used during the day, where other sources (gas, oil) are more
expensive.

Sylvia

 

[?]

I'm sure there's a net gain. Not only is the power produced by the PV
cells being consumed in the neighbourhood, but the grid losses, such
as they are, are obviated because that power doesn't have to pass
over the grid.


Now you get in the murky area of the definition of benefit. The total
power available is increased, at the instant it's produced, but except
in very unusual circumstances, it's not power that would otherwise
have been unavailable (which would have let to power cuts). All the
PV cells are doing is reducing the production of power by the
existing generation plant with the highest marginal cost (typically
gas or oil). The only benefit is the elimination of the CO2 that
would have been produced by that other plant. Whether that
elimination is a real benefit is a separate argument.

"reducing the production of power"

Interesting you say that as I have wondered about the "mechanism" to gauge
the amount of power that is required to maintain all the houses/factories at a particular time of day etc.

Is there some kind of dynamic sensing device that knows if there is a reduced load
and therefore less coal/gas is burned?
Then if the demand is increased, does the "mechanism" sense this instantaneously
and say "x tonne" of additional coal is shovelled into the furnaces to generate more electricity?

Well, that won't happen. Even in a green politician's wildest dreams,
there's simply not going to be anything like enough PV output from
domestic rooftops to meet the entire power load during the day.

It'll never meet the demands of industry, there is no way you can power
an aluminium plant with PV, that's for sure!

That aside, where is surplus energy stored? For the most part, we have
no practical way of storing energy on this sort of scale. There is a
small capacity to pump water from the lower side of hydroelectric
plants to the high side, and the energy, or most of it anyway, can
later be recovered by operating the hydroplant. Of course, this
presupposes that the hydro plant doesn't have enough reserve to have
operated anyway.

This scheme is used, as are some compressed air storage systems, but
they are limited by the need to have suitable places to build them.
There are a few other mechanisms, but none have a major impact. But
these schemes would never be used to store the energy produced by PV
cells. It wouldn't be economically worthwile. Where they are used,
it's to store energy produced cheaply overnight from coal or nuclear
so that it can be used during the day, where other sources (gas, oil)
are more expensive.

Sylvia

I've heard about storing the access energy into the batteries of electric cars
that are plugged into the grid , that of course is some time into the future ( if it ever eventuates)…

 

[Sylvia Else]

"reducing the production of power"

Interesting you say that as I have wondered about the "mechanism" to gauge
the amount of power that is required to maintain all the houses/factories at a particular time of day etc.

Is there some kind of dynamic sensing device that knows if there is a reduced load
and therefore less coal/gas is burned?

The entire network is the sensing device. The more current is drawn, the
more torque is required to keep the generators rotating at their nominal
rate. Any tendency for the rotational rate (or equivalently, mains
frequency) to change is detected by the generator control mechanism, and
inputs (steam, gas, whatever) changed accordingly.

Then if the demand is increased, does the "mechanism" sense this instantaneously
and say "x tonne" of additional coal is shovelled into the furnaces to generate more electricity?

In the very short term, it's the rotational energy of the generator that
changes.

In practice, specific generators are tasked with maintaining the
frequency by changing their power output, and their owners get paid a
premium for doing it.

It'll never meet the demands of industry, there is no way you can power
an aluminium plant with PV, that's for sure!



I've heard about storing the access energy into the batteries of electric cars
that are plugged into the grid , that of course is some time into the future ( if it ever eventuates)…

Seems highly improbable to me. At the times when the stored energy is
needed, daytime, the cars are more likely to be being driven, or at
least not plugged in. In any case, a car owner is likely to want his
battery charged against need, and not come out of his house to discover
the the car's unusable because of a preceding high power demand. The
whole "using car batteries" concept is being pushed by the PV/Wind
brigade, in an attempt to address the inherent limitations of a system
that produces power when it can, not when it's needed.

Sylvia.

 

[Sylvia Else]

It's a benefit to:

(c) the generating authority, by way of reduced capital servicing
costs.

Except that it doesn't do that, because the infrastructure still has to
exist to supply power when the PV cells aren't. Today in Sydney was a
nice example of how PV cells can fail even to offset airconditioning
loads. It reached 40 degrees where I live, but was still overcast for
much of the day.

Sylvia.

 

[Jasen Betts]

Government offer of *feed-in tariff of 60 cents per kilowatt hour (kWh)*

I'm a bit confused about the government offer of paying the owners of solar
photovoltaic (PV) systems who put power back into the grid.

Is this at all possible in the real world?

When you consider the power losses within the cables and other
infrastructure on the electricity grid.

Does an array of solar photovoltaic generate *enough power* to feed any
*useful* energy back into the grid?

The power only has to go next door to find another consumer
so unless you're on the end of a 100km SPER line I'd say the
answer is yes.



--- news://freenews.netfront.net/ - complaints: [email protected] ---

 

[Jasen Betts]

"reducing the production of power"

Interesting you say that as I have wondered about the "mechanism" to gauge
the amount of power that is required to maintain all the houses/factories at a particular time of day etc.

Is there some kind of dynamic sensing device that knows if there is a reduced load
and therefore less coal/gas is burned?

thermal plants (gas, coal, nuclear etc) can't respond fast enough to
track to diurnal load variations, other types or plants ( hydro, compressed air, and
internal combustion) can respond more quickly.

Then if the demand is increased, does the "mechanism" sense this instantaneously
and say "x tonne" of additional coal is shovelled into the furnaces to generate more electricity?

AIUI power load equates to drag on the generator rotor which if it
exceeds the input torque reduces the frequency of the mains supply.

that can measured and used to close the feedback loop

the one time I got to play with a 3kVA portable generator
I plugged a 2.4kW heater into it and watched it respond
the motor slowed a little and the mechanical govenor in
the crank-case moved a linkage which opened the throttle
to compensate. (my impression was it got louder but not
noticeably slower)

It'll never meet the demands of industry, there is no way you can power
an aluminium plant with PV, that's for sure!

for sure! they need 24 hour power for a start...

I've heard about storing the access energy into the batteries of electric cars
that are plugged into the grid , that of course is some time into the future ( if it ever eventuates)Â…

This is what all the different electricity supply tariff rates are
about. Excess power (mostly) generated by thermal plants sold off
cheap because they can't turn the boiler off and back on overnight
(or during other periods of low demand).


--- news://freenews.netfront.net/ - complaints: [email protected] ---

 

[David L. Jones]

Government offer of *feed-in tariff of 60 cents per kilowatt hour
(kWh)*

I'm a bit confused about the government offer of paying the owners of
solar photovoltaic (PV) systems who put power back into the grid.

Is this at all possible in the real world?

Yes, it works. They will actually pay you, and you *can* efficiently put
power back into the grid.
Whether it makes actual economic sense overall is another matter entirely...
The scheme is likely not economically sustainable, grab it while you can.

When you consider the power losses within the cables and other
infrastructure on the electricity grid.

It's not that bad, the grid is actually quite efficient. The power you
generate will be used more by your neighbours rather than the rest of the
grid, so the losses are fairly minimal becuase their power is supplied
locally.

Does an array of solar photovoltaic generate *enough power* to feed
any *useful* energy back into the grid?

Yes. A typical system of 1KW is a pretty decent amount of power, certainly
not insignificant. Most of it will be usable after various losses. If you
switch off your house power then most of that goes back into the grid to be
used by your neighbours.

It's all about averages and so forth.
Back of envelope:- If everyone had a 1KW system on their roof in Sydney for
example (1.5million people), that's 1.5GW of peak power available to the
grid as a whole, or roughly half of the snowy river hydro scheme output. And
that power is distributed near point loads, so it's comparatively quite
efficient.

Nit-pickers go for your life...

Dave.

 

[Mauried]

if there are consumers nearby without solar and using energy - it
would




Remember too - about the "feed in tarriff". in the QLD system, it is
only paid on power IN EXCESS of what you are using in your own home.
So if you are using 0w and generating 1kw - you will be paid the feed
in tariff on the 1kw x the number of hours it is generated.

If you are using 500w and generating the 1kw, you are paid 50% of the
feed in tariff PLUS saving the normal tariff of the 500w you are using
in your home.

If you are generating and using the same amount, then you are only
saving the normal tarriff, which is a LOT less than 60c (typically 17c
for domestic and half of that for off-peak hot water - if its actually
on at that time. .


If you arent going to be home during the day, and can turn off all
appliances in the home during that time - including hot water systems,
and all things that use stand-by power - you will get the full 60c.

You may be able to get away with turning the fridge off during some or
all of that time, if the insulation is good, no one will be home to
open it, and you don't have anything that is going to spoil at the
slightest drop in temp. (IE beer fridge in workshop) Whether this is
worthwhile compared to the savings is another matter.




As to your other question, if the power being generated isnt being
used, it isnt stored anywhere.

Its the same scenario as a generator running without load, or a better
analogy would be a battery that is not connected to anything.

With no load, the impedance of the power lines would just rise
slightly and the power from the solar system simply wouldn't flow into
the grid as there would be no load for it to flow into. Whether the
solar system generates a slightly higher voltage than the mains
voltage - to get it to flow in and therefore "take priority" over the
mains, for any load on the grid that is below the solar panel's full
output capacity - I don't know.


The inverter in the solar system might even just shut itself down,
until there was a load present ?

Grid Tie Inverters push power back into the grid by raising thier own
voltage above the incoming mains, so that current flows back into the
mains.
If there is no grid voltage present, the Inverter shuts down.
Practice is called anti islanding, and is done for safety reasons, so
that if the electricity supply to your house is cut for any reason,
the internal wiring wont be live.

 

[Mauried]

thermal plants (gas, coal, nuclear etc) can't respond fast enough to
track to diurnal load variations, other types or plants ( hydro, compressed air, and
internal combustion) can respond more quickly.


AIUI power load equates to drag on the generator rotor which if it
exceeds the input torque reduces the frequency of the mains supply.

that can measured and used to close the feedback loop

the one time I got to play with a 3kVA portable generator
I plugged a 2.4kW heater into it and watched it respond
the motor slowed a little and the mechanical govenor in
the crank-case moved a linkage which opened the throttle
to compensate. (my impression was it got louder but not
noticeably slower)


for sure! they need 24 hour power for a start...


This is what all the different electricity supply tariff rates are
about. Excess power (mostly) generated by thermal plants sold off
cheap because they can't turn the boiler off and back on overnight
(or during other periods of low demand).


--- news://freenews.netfront.net/ - complaints: [email protected] ---

Currently, there arnt any efficient ways of storing electricity.
All the known methods require turning the electriciy into something
else , storing the something else, and then reconverting the something
else back into electricity.
At every conversion phase, you lose some of the electricity.
Hydro dams are the best so far, but they are only around 70%
efficient.
So storing electricity only makes sense when the electricity to be
stored is coming from a very low cost power source like a coal fired
power station.