ShinyChrome: Ooof, what happened at 10 to 6pm

It's gotta be a data error. - looks to be about double what it was one block earlier or later.

NZ only has about 9.5GW of installed capacity (and not all of it is available at the same time), so no way we could have manage a 12.5GW spike...

Handle9:
That introduces a lot of variables to the grid which can make it challenging to effectively maintain stability. Current grids aren't designed around distributed generation and will require significant changes and upgrades.

Electric Kiwi files 'UTS' complaint over Monday's electricity market failure | Stuff.co.nz

"The fundamental issue was that Genesis was basing its decision on the power it needed to generate to supply its own retail customers and meet its contractual obligations with wholesale customers, rather than the needs of the whole market, he said."

Kyanar: 

Here in Australia

If they have reached the point where they are running 100% on solar, they need to start looking at grid scale storage. 

I can imagine the spot price would be getting very cheap on those days to the point where a city could be looking at a cold or heat storage project to absorb the electricity.   

Or small pumped storage. If you look at the twin lakes in upper hutt, there is about 36MW stored between the bottom and upper lakes in just the gravitational energy from the 20 metre altitude difference.
Assuming 8kwh units of usage for an average household between 6pm and 9pm, that will satisfy the power requirements of 4,516 households. That is around 30% of upper hutts residential power needs during the evening 6pm-9pm hours. 

I see a lot of argument in australia with CEOs of lines companies saying that the grid isnt designed for solar panels and moving the electricity in such a way. The answer is simply finding ways to dump the excess into storage from the local distribution rather than the national or state grid.   

It looks quite simple to me, to find some unused low value land near a city and convert it into a micro pumped storage facility with some earth moving equipment. 

Ideally it would be Onslow size and scale but if they cant move the electricity to a central load then perhaps have many smaller dump loads closer to the producers/consumers. 

If Local HydroCO™ is able to pay a penny for the power during the day because there is so much excess power from all these solar panels, and then makes a profit by selling it in the evening, while only needing to transport the electricity through the local distribution a few kilometres then thats awesome. Still better than charging to allow people to export or dump to the grid because there should always be demand from a purchaser that exceeds supply.  

SomeoneSomewhere: The issue (one of them) is that houses just aren't really the ideal place for solar. They're usually unoccupied during weekdays, with limited ability to soak up load. And if every house has 5kW of solar, as Australia is finding, you start overloading supply transformers because the solar exceeds the average maximum demands that the transformers are sized for. Could batteries improve this? Yes, but it's a bad way to. We don't want to use batteries if we can avoid it because they're an environmental PITA. Chuck the solar on supermarkets, retail, and offices where there's tons of daytime lighting, AC, and refrigeration that nicely tracks insolation. Putting retail customers on 100% spot pricing is absolutely not going to work - it's too risky and unpredictable. But we should really look at improving the incentives and load control we have. Most new builds no longer have any ripple control or time clock. Most customers pay a flat rate regardless of when they use power or the maximum demand. Should we start adding max demand charges or forcing day/night or peak/day/night plans?

Why not make it a requirement for PVs to heat the HWC during the day? The HWC in peoples houses is a big energy store.

mattwnz:

 

 

 

Why not make it a requirement for PVs to heat the HWC during the day? The HWC in peoples houses is a big energy store.

 

Solar PV is so marginal (not for all) that you can't do that. You have to use it or lose it. Its excessive in Summer when you don't need it, its not there in Winter when you do, thats the problem with PV. I cant get PV despite my house being large and north facing , but if I could Its very marginal. I have Solar HW, that is great, but the same Winter issue exists. But with Solar HW my 300L cylinder is off grid 1/2 the year.

You also end up needing a larger tank or losing capacity, because now you have to avoid heating hot water during times the sun isn't shining - so overnight, when power is cheap anyway.

And a typical tank has a 3kW element and gets up to temperature within a couple of hours. If you have 5kW+ on the roof and it's a sunny day, by midday everyone's cylinder will be hot anyway. Either you continue heating well over 65C (increasingly inefficient due to losses, and also potentially more dangerous if a mixing valve fails) or you dump it all into the grid.

SomeoneSomewhere: And if every house has 5kW of solar, as Australia is finding, you start overloading supply transformers because the solar exceeds the average maximum demands that the transformers are sized for.

I don't understand this.

Is it that smaller transformers are being installed *because* houses are on solar so average demand is (expected to be) less? But when houses run out of battery, the transformer load quickly increases beyond what it is designed for? i.e. the maximum demand has been underestimated? But surely transformers must be sized for more than average maximum demand, because you would expect that there would be several maxima each year greater than the average maximum? Wouldn't you design for absolute maximum plus a bit more for growth?

frankv:

 

SomeoneSomewhere: And if every house has 5kW of solar, as Australia is finding, you start overloading supply transformers because the solar exceeds the average maximum demands that the transformers are sized for.

 

I don't understand this.

 

Is it that smaller transformers are being installed *because* houses are on solar so average demand is (expected to be) less? But when houses run out of battery, the transformer load quickly increases beyond what it is designed for? i.e. the maximum demand has been underestimated? But surely transformers must be sized for more than average maximum demand, because you would expect that there would be several maxima each year greater than the average maximum? Wouldn't you design for absolute maximum plus a bit more for growth?

 

 

 

I think SoneoneSomewhere is talking about when the solar is feeding the grid. The combined output of all the solar systems connected to a transformer is capable of overloading the transformer.

I went out and had a bit of a count, and found a 100kVA poletop transformer with about 37 houses connected to it, or a bit under 3kVA per house on average. But each house has a pole fuse for 15kVA, so what gives?

It's unlikely that the houses are all flat out at the same time. Some will be cooking tea earlier/later. Hot water cylinder gets shut off during peak hours. You can overload the transformer for a short while because there's a lot of thermal mass in the oil and steel - it takes a while to heat up. Then it has hours of low load overnight and during the middle of the day to cool back down.

If you have a lot of houses with 5-8kW of solar on the roof and very little load, then they all produce peak output at around the same time, because the weather is more-or-less the same. That generation going backwards through the transformer heats it up just as much as load does, and it's probably in the hot sun at the same time. And now, just as the sun is disappearing and the generation dries up, the evening peak kicks in as people get home from work. Transformer is now at capacity again in the other direction.

Slap 50kW-100kW of solar on top of Countdown? Their refrigeration systems probably don't ever go below 30kW. Add some aircon, lighting etc, and it's questionable if they ever actually export power to the grid. You would usually have a hard time fitting enough PV on a supermarket/mall/other commercial building (exception warehouses and the like) to wipe out their daytime power usage, let alone overload the transformer back in the other direction.

Capacity a bit low again tonight: https://www.transpower.co.nz/sites/default/files/interfaces/gen/GEN%20Insufficient%20Generation%20offers%20North%20Island%204038210476.pdf

Well at least wind is up today, not much out of Huntley, and still plenty to tow out of SI.

Market

Cyril

The GEN notes that Pole 2 of the HVDC is out of service. This both halves capacity and increases the amount of reserves required as if one pole trips, the remaining pole can't pick up extra load.

Note that the price in the north island is ~4x as much as in the south - HVDC constraint.

It would be interesting to see if the rest of Huntly is about to come online (would probably expect it by now, or if they've screwed that up again.