Re: Research: Wind power pricier, emits more CO2 than thought

On 19 Jul, 19:48, "rlbell.ns...@xxxxxxxxx" <rlbell.ns...@xxxxxxxxx>
wrote:
On Jul 18, 12:36 pm, disgoftunwells <disgoftunwe...@xxxxxxxxxxx>
wrote:

On 18 Jul, 17:01, "rlbell.ns...@xxxxxxxxx" <rlbell.ns...@xxxxxxxxx>
wrote:

- Nuclear - if you look at the cost models, the overriding cost driver
is cost of capital. The French Government had a low cost of capital is
therefore able to supply very cheap electricity. The next biggest
variable is uncertainty over construction costs. I would expect
nuclear to be cheaper than the current cost of wind power. However,
Britain is not going to build more that a dozen nukes, which could
provide a maximum of 40% of the electricity supply.

Did they pass laws banning the construction of more than dozen?

For better or for worse, in effect and by default, yes. (Except on the
other side of the channel).

So, in truth, the UK has not irreversibly banned further construction.





- Gas: Cheap to build, but very expensive to operate. Given current
gas prices, on shore wind is cheaper. In future, gas should be used
for peaking units (or for home power generation - where its efficiency
can approach 100%).

When you talk about CHP and electricity production, at the same time,
you must sperate the heating efficiency from the conversion
efficiency. You must also seperate the electrical output from the
heat output. As a heat source, they are expensive, but thermally
competitive, however, their heating efficiency goes down when they are
also producing electricity (but it does produce electricity). As a
generator, they are comparable in output to a portable gasoline
powered generator, except that they are less efficient and more costly
(way, way too much waste heat). Their only excuse for existing is
producing heat and power at the same time. Getting electricity out of
them when they are not producing heat is really expensive.

I was looking for a cost competitive successor to the whispergen. That
could be a fuel cell or a small gas turbine, producing about 25%
electricity, 70% usable heat, and perhaps 5% waste (which is more than
a condensing boiler).

Going by the spec/info (and interpreting them as optimistically as
possible), the whispergen has an electrical conversion efficiency of
(1kw electric and 7.5 kw heat) 12%-- with a Sterling cycle! Sterlings
are actually a really good choice, as a well designed installation,
with appropriate duct work, can supply heat and electricity, draw
power and pull heat in from outside, or draw power and pump heat out
of the house. Another interpretation of the specs puts the efficiency
up to ~18% (0W electricity and 7.5kW heat to 1kW electricity and
12.3kW of heat). While not as good as a Carnot engine, the Sterling
is as good an engine as can be built (unless you care about size--
they are very large for their output).

The words 'small', 'gas turbine' and '25% efficiency' do not go
together. Much of the losses in a gas turbine arise from air slipping
past the blade tips. Large gas turbines get around this by having a
tiny clearance, relative to their blade length, but the smallest
possible clearance gap is not that different for a two foot blade, as
a two inch blade (once both units are at speed and up to normal
operating temperature). Another loss is heat passing through the wall
of the combustor, and out of the engine, before the working fluid gets
to the turbine, which also unfairly penalises small units.

I would like to be wrong, but does anybody make a gas turbine CHP unit
under 50kW?

Not sure. I've seen quite a few whispergen type units at about 10KWe -
good for blocks of flats and small factories.

You mentioned earlier you expected a hydrogen economy. A better goal
might be domestic fuel cells. These can convert gas to electricity at
about 40%. Capturing the vast majority of heat should be trivial.





- Oil: Similar analysis to gas, but more expensive.
- Wind: On shore can supply competitively, but is space constrained.
Offshore not yet competitive, but the cost curve (ref discussion above
about immaturity) is looking promising.
- Solar: Hugely expensive, but has the most promising cost curve, but
mainly for countries with a lot of sun and where maximum demand
correlates with maximum sun,

So I could see a rosy scenario where the UK electricty mix is 1/3
nuclear, 1/3 wind, 1/3 gas, with most of the gas being micro CHP. And
a high capacity line to Norway, where surplus wind is used to pump
water up mountains.

No, the ratios, as you describe them, are 1/2 nuclear, 1/2 wind, and
1/2 gas turbines (50% overcapacity);

Electricity supply 1/3, 1/3, 1/3. Small scale CHP is important in the
winter, when the heat is used, making its effective/combined
efficiency close to 100%. In summer, it's only used when the wind
doesn't blow.

How is this implemented? The utility is being given the right to stop
me exporting power when the wind blows in winter and to force me to
export power when it is economically disadvantageous to me, in
summer. If I have invested in CHP, what do I get out of it?

Lets assume you don't invest a 40% efficient, fuel cell, but someone
can make a 20% efficient unit.

Lets assume you can buy gas at 2p/KWhr.

In summer, you log on and say you're happy for the utility to turn on
your unit at their discretion and buy electricity at 12p/KWhr. The gas
costs you 10.

Or, you pre-agree to sell a limited amount at 6p, That keeps your
water hot for showers.

In winter, you log on and say you're happy for the utility to turn on
your unit at their discretion and buy electricity at 6p/KWhr, up to a
certain amount. As long as you're not using too much electricity
yourself, you're marginal cost of export is 2p.

Best of all is if you have a very large hot water tank so you can heat
your house at a different time from the electricity supply.

really expensive peaking power and importing up to a third of
electricity demanded at any given time. The norwegians are only going
to buy surplus wind power killowatt*hours if they are sold at less
than the cost of hydro-electric kilowatt*hours, but they will sell the
power back at peaking rates (that's the free market, for you).

No - less than the price of HEP KWhrs. The marginal cost of HEP is
close to zero.

Norway will import surplus wind because for every KWhr they import (or
produce), they can export about 0.8KWhrs. Obviously they have to make
a margin on this, and there they have to compete with other storage
means.

To add> insult to injury, if the high capacity line does not run directly to
Norway,under the North Sea, every utility along the way will charge
for wheeling the power (as it reduces their transmission capacity, but
does not supply them with power).

There would need to be a European, or North Sea HVDC grid. Nice thing
is that laying HVDC at sea is cheaper than on land.

I can see a rosier picture with 100% nuclear producing hydrogen for
fuel cells during the off-peak periods, and the fuel cells supply any
needed peaking power (not as cheap pumped storage, but way cheaper
than oil/gas peaking). Everybody pays less for electricity and there
is hydrogen for their fuel cell cars.

Except Electricity to Hydrogen to Electricity is about 40% efficient,
which is why most of the world is giving up on hydrogen.

Two and a half times the cost of a nuclear generated kWhr is still
less than the cost of a peaking unit kWhr.

Gas would have to go up a lot more for that.

And for storing energy a VRB unit will be much more cost effective
than hydrogen.

There are schemes like this though:http://www.vrbpower.com/technology/ess-specifications.html

It would be interesting see what the cost is per GWhr of storage. If
you were designing a HVDC grid (as a CEGB / French Government might,
rather than having economics dictate it), it might make sense to have
a few GWHr storage plants at the ends of the HVDC net.

Storage of real energy is less important for HVDC systems than a solid
source of reactive power. Once you get past driving large motors, you
really do not want to use inverters-- they are too inefficient, so the
receiving end of the HVDC link has to have enough reactive power to
excite the rectifier bridge. HVDC links cannot transfer reactive
power and both ends of the link are heavy reactive loads. Also, there
is no coupling between the ends of the HVDC link, so weakness at one
end cannot be assisted by stiffness at the other and the large
inductance of the HVDC line will prevent fast power responses.

So if I was designing an HVDC grid, there would be large synchronous
reactances to provide reactive power, and their rotational inertia
would stiffen the grid long enough to adjust power distribution
(alternatively, a diesel engine helps keep the system frequency from
falling).

As I understand HVDC beats AC for lengths of more than a few hundred
kilometres, or under water.

The transfer of power is controlled by computer, rather than
reactively following loads.

Any distribution system is limited in the power it can transport, so a
storage system at either end can be useful.
.

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