Re: Strategies for CO2 reduction

thanks for your points

Toby Kelsey wrote:
> Alex Terrell wrote:
>
>
> Some of your claims for wind energy seem out.
>
> You claim an installed capacity of 25GW, but this apparently only produces
> a maximum power of 22.5GW. Why lose 20%? You limit wind power use
> because of intermittency and put in a "low" value of 5GW - half the
> average and one-fifth the peak power. I would expect with many turbines
> widely distributed over the UK the overall fluctuations would be much
> lower and the use could be larger. Also you claim that the use of other
> renewables limits wind power use. How?
>
On average, wind turbines at sea run at about 35% of capcity, compared
to 25-30% on land. I assume that can be improved, to 40% to give 10GW
from 25GW capacity. Given the widespread deployment, this average
should be reached most of the time.

The extreme scenarios are what the Grid would need to plan for. Given
wind turbines being maintained, I think 90% of capacity could be the
maximum. Likewise, a stable high over the North Sea, where most of the
capacity would be, could mean no power from these windmills. The sea
breeze would always provide some win, but not 24 hours per day.

> Also you claim that the use of other renewables limits wind power use. How?

Not so much limit, but require additional standby capacity, either from
gas or from regulating nulcear plants. So if there's a cold, stable
high winter's evening, with no waves, and the tidal barrgaes are not
producing, hardly any power is coming from intermittent renewables.
This is an unlikely combination of events, but would still need lots of
gas powered standby capacity.

> Then you claim you couldn't install more capacity because windy days might
> produce "too much" power. Are you serious? Who's holding the gun to the
> turbine operators which stops them shutting down turbines or just dumping
> the load? I'm sure that if "too much" power was a frequent occurrence
> there would be many profitable schemes created to solve the "problem".
>
If there's too much power, the price of electricity falls, and the wind
turbine operators revenue falls. This pushes up the average cost of
wind energy. So it's not a technical problem, but an economic one.

> Does your calculation of CO2 reductions by nuclear power include the CO2
> produced by Uranium mining, power station construction and
> decommissioning?

Probably not the mining. Power station construction is included in
figures for "Cement Production" and elesewhere. The construction and
support of a nuclear power station, or a wind turbine produces
negligible CO2 compared to what it saves. (Solar cells fabrication is
not negligible, but still produces a payback)

> In general it would be useful to see the the capital and
> maintenance CO2 load for each of the technologies.
>
There has been research on this.

> Your assumption that PV remains uneconomic for the next 25 years is not
> credible given its rapidly decreasing costs.
>
Perhaps, but I can't see silicon based photo voltaics being economic in
the UK. Of course, we can hope for an alternative form - thin film
printed cells? In southern countries, high demand for electricity is
caused by bright sunny days. In the UK, Winter 6pm is about the peak
demand time.

> You don't mention the option of local/domestic renewable energy being sold
> to the grid, which has great potential. And given you assume widespread
> PHEVs and worry about intermittency and energy storage, I'm surprised you
> didn't include car-to-grid storage.

I did mention it at the end, but you are right. 30 million PHEVs would
contain 300 GWHrs. 20% of that would supply most shortfalls.

Also, most offices, perhaps even households, might have fuel cells that
produce combined heat and power. Even in summer, if the electricity
price goes above X, then a lot of these will come on. So one could have
30GW of gas fired fuel cell capacity in 15 million seperate units. This
may be expensive given prives of gas in 2030, but it will guarantee no
blackouts.

This means that centralised electricty generation would be nuclear and
renewables and be carbon free. Now I have a problem - from where do I
get the CO2 for the algae farms?

Alex

.

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