Labour attacking plans to sell power plant

[Mully]

The formula for getting power from water is:

P = GQHe
where P is power in kW
G is gravity (9.81 m/s^2)
Q is the flow of water in cumecs
H is the head (height) or equivilent head of water in m
e is the turbine efficiency.

In tidal, or instream situations where there is no or very little actual head then the equivilent head must be calculated from the speed of water.
H = V^2/2G

and the flow Q is calculated from
Q = Va
where a is the cross sectioanl area of the flow path through the turbine in m^2.
e in the power formula is highest when a is minimised.

So it is obvious that unless you have a large head, or high velocity of water then it is impossible to get meaningful amounts of power.

Well yeah, of course that's obvious........

All I know is they claimed to be able to power 250,000 houses or some such. And the NIMBYs had a waaaaaaaa (tm).

[Ocean1]

Um, no such animal as cumecs per day. One cumec is one cubic meter of water per second. Cumecs per day is a bit like km/hr per day.

I meant cumecs plotted over the tide cycle duration, (but not daily, true). Still can't find the graph I was looking for.

[piston broke]

Jantar,you seem to be the knowlegable one here.
is there a reason they don't have solar panels around the wind turbines?
is it because the cells aren't good enough yet or maybe startup costs.
and of course profit

[superman]

Jantar,you seem to be the knowlegable one here.
is there a reason they don't have solar panels around the wind turbines?
is it because the cells aren't good enough yet or maybe startup costs.
and of course profit

They've started putting solar panels on top of wind turbines

But they have to provide a meaningful amount of energy for the cost put in, and that includes all year around. NZ good for wind, not great for all year high energy light. And winter is when more power is used so unless you had huge batteries to store summer solar energy through the winter it would be pretty pointless and probably not cost effective.

[Jantar]

Jantar,you seem to be the knowlegable one here.
is there a reason they don't have solar panels around the wind turbines?
is it because the cells aren't good enough yet or maybe startup costs.
and of course profit

Costs of installation, poor efficiency, and the area required makes them unworkable on a large scale. Spain tried a solar inititive and it sent their power generation company to the wall. Some aussie states are trying it with domestic solar and expect that it may be economic in around 40 years time.

[Winston001]

Bling to Jantar for informative facts.

It isn't commonly recognised that solar cells are inefficient. The best ones only capture 15% of the energy which falls on them. As well as that, they cost a lot to make so the energy produced is 5 times more expensive than hydro. They require wiring and bits and pieces and they do not last long.

[piston broke]

They've started putting solar panels on top of wind turbines

But they have to provide a meaningful amount of energy for the cost put in, and that includes all year around. NZ good for wind, not great for all year high energy light. And winter is when more power is used so unless you had huge batteries to store summer solar energy through the winter it would be pretty pointless and probably not cost effective.

i guess the storage battery would be,less use of hydro,therefore during the summer you would keep more water behind the dams for peak use in the winter.

how much wind speed do you need to get those big wind turbines to start?

[Jantar]

i guess the storage battery would be,less use of hydro,therefore during the summer you would keep more water behind the dams for peak use in the winter.

how much wind speed do you need to get those big wind turbines to start?

To answer your second question first. The speed at which wind turbines begin to produce energy variesaccording to design and manufacturer. We track closely the ones at White Hills (near Mossburn) as they cause us to spill water over Clyde and Roxburgh. They appear to begin generating at a wind speed of around 15 kmh and feather at around 55 kmh. Yes, Too much wind and they stop working.

Solar power that is designed to feed back into the grid, do not use storage batteries. That would make the cost prohibitive. Storage batteries are only used in very small solar power situations. I believe that some solar farms farms do use small battery banks as a power smoothing. These have a few seconds of storage only.

Electricity is the one commodity that is made as it is used. It cannot be stored on any scale. This means that the electricity generators in total have to be able to follow the load. New Zealand has a very predictable load pattern as our whole country is on a single time zone. Most people sleep at night, so our demand is minimum around 2:00 - 5:00 am. Between 5:00 and 7:00 am people are waking up putting on their morning coffee etc. and by around 8:00 am even teenagers are out of bed and demand is suddenly very high. Over that 3 hour period from 5:00 to 8:00 demand more than doubles. It then drops off as the day goes on to reach a second minimum around 2:00 to 4:30 pm, then a second peak around dark, then drops off again. Solar power doesn't produce any energy at all during these rises to the peaks in winter, but does produce its maximum in the afternoon when it isn't needed. It is starting to produce power at the morning peak in summer, but again, that's when hydro inflows are at their peak, and additional energy isn't needed.

Solar power can work best in places where more energy is needed for air conditioning than for heating. Spain and northern Queensland perhaps?

[superman]

Solar power can work best in places where more energy is needed for air conditioning than for heating. Spain and northern Queensland perhaps?

There is a proposal to have satellites with large solar panels that then beam the energy to the ground via microwaves. Don't know how far they've gone in developing that so far, but that would provide 24 hour output of solar power and therefore could be useful. However you would then require an area of land to pick up the microwaves and of course no plane could fly over this zone etc etc. But the idea... is a good one.

So some companies just use capacitors to even out voltage peaks do they?

[Winston001]

What I fail to see is...
If it was 'necessary' to build the Whirinaki plant as backup, because of shortfalls in generation, in 2001 - since then demand has increased, but has generation done so too, to the point where that extra capacity is not needed?

An excellent question and I'm surprised nobody else picked up on it. I dunno either.

But I'll hesitate a guess: we are short of electricity but not at any price. If its too expensive, then it doesn't get used. Whirinaki is oil powered? which makes it costly to run.

Even so, I'd have thought one of the major electricity companies could run it and spread the cost across its other generation plants. I suppose that puts them at a competitive disadvantage if they are needing a higher overall price than other generators.

[Winston001]

There is a proposal to have satellites with large solar panels that then beam the energy to the ground via microwaves. Don't know how far they've gone in developing that so far, but that would provide 24 hour output of solar power and therefore could be useful. However you would then require an area of land to pick up the microwaves and of course no plane could fly over this zone etc etc. But the idea... is a good one.

http://en.wikipedia.org/wiki/Space-based_solar_power

Its an interesting idea and beaming energy from space 24/7 has potential.

Experiments have been carried out at Goldstone California, Reunion Island, and most recently in Hawaii. In that case they beamed 20kw 92 miles which is astonishing when you think about it.

We could also beam direct sunlight from space using parabolic mirrors onto a "kettle" on Earth. The kettle would heat up and run steam generators just like geothermal power stations. Highly efficent and much easier than microwaves but focusing the beam would be critical. Basically we are talking about a death ray from space.

[Swoop]

and by around 8:00 am even teenagers are out of bed

WHAT!!??

Seriously? What planet is this on?

[Ocean1]

There is a proposal to have satellites with large solar panels that then beam the energy to the ground via microwaves.

Problems with atmospheric attenuation across most frequencies.

Basically we are talking about a death ray from space.

Problems of a more political nature with more suitable frequencies.

[Smifffy]

An excellent question and I'm surprised nobody else picked up on it. I dunno either.

But I'll hesitate a guess: we are short of electricity but not at any price. If its too expensive, then it doesn't get used. Whirinaki is oil powered? which makes it costly to run.

Not at any price?

Start with rolling brownouts/blackouts across Auckland & Wellington, and there will be a hue and cry for more generation at any price.

At the rate we are going, I wonder when we will get ditched from the OECD and join the 3rd world properly. At least then we'd get some Kyoto money to waste.

[Banditbandit]

PS where the custodian of the land , the so called Maori party ??

Kia ora koutou ... It's a dirty smelly station burning either oil or diesel polluting our land .. get rid of it now ..