3kW Grid Tied Solar PV: Watts and Warts.

Forums › Home Workshop DIY › 3kW Grid Tied Solar PV: Watts and Warts.

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | ... | 25

29105 posts

Uber Geek
+1 received by user: 10222

Trusted

Lifetime subscriber

#929742 8-Nov-2013 21:32

Mains voltage rising in areas with a high density of people with solar has already proven to be a problem in Australia, and when the voltage goes too high the inverters will shutdown meaning you end up making nothing. Thats where the vector deal with the battery has its advantages so you can hopefully at least stick that energy somewhere that it will not get wasted.

Richard rich.ms

wongtop

569 posts

Ultimate Geek
+1 received by user: 50

#929760 8-Nov-2013 22:01

richms: Mains voltage rising in areas with a high density of people with solar has already proven to be a problem in Australia, and when the voltage goes too high the inverters will shutdown meaning you end up making nothing. Thats where the vector deal with the battery has its advantages so you can hopefully at least stick that energy somewhere that it will not get wasted.

This is exacerbated in Australia, as there they mostly target a voltage of 240V, which leaves less "headroom" for high voltage as most appliances in the IEC world are designed for a nominal voltage of 230V. I recall seeing somewhere where some utilities in Australia are looking at reducing their target voltage to 230V to give themselves a bit more headroom.

Parewanui

30 posts

Geek
+1 received by user: 3

#929790 8-Nov-2013 23:10

@ k14
I too live in Central Otago.
Frankton, near Queenstown.
Myself and 2 neighbours are seriously looking at photo-voltaic.

Neighbour 1 is closer than me to installation as he already has solar-thermal. Which along with the wet-back on his wood-burner provides all the home’s hot water in winter. In summer, without the wood-burner running, solar-thermal is not quite enough (2 daughters using the hot water I think but I need to check this). So he wants to try photo-voltaic next. Also he has the money. I need to save.

Neighbour 2 and I have started looked at re-implementing his hydro-plant. This is seriously interesting and I will write this up another time. He already has the water-rights, and pen-stock. We are looking are replacing the generation gear. The original plant is from the 1960’s and stopped working in 1996. Neighbour 2 also has an $8k diesel generator (it’s big – it covers a third of the ute-tray). Over the next while (year(s)) we will be comparing running this compared to the hydro, and compared to grid-supply. Also, I hope, compared to photo-voltaic and compared to wind (VAWT). Actually, I think the wind is the most interesting as his farm is very windy. But this is the most risky – too much initial cost to install wind turbines, and unknown output. The hydro is a known install price and kWh output.

@Amosnz
Thanks for mentioning the efergy monitor.
I’ll investigate.
Actually, my neighbour is already using a smart meter but that was many-$$.
This looks much better.

@Porboynz
Like a few others have mentioned I’m keen on your generation-data and consumption-data.
I’ll be sharing mine and the neighbours – when we get there.
$12k is getting up there and I’ll have a hard time convincing my wife without the kWh-output to estimate pay-back. Simple install-price compared to kWh-usage-$ is what I want to do. And without selling power. That was the main reason for my initial post – because I estimate it is too risky saying home-generation will generate say this amount of $ income over the next 10 years.

Hence me keen on the gear dropping in price.
Then it’s 2 years pay back.
It will happen (because it has for real in other regions), but when in NZ?

Also hence me mentioning Germany.
They had a guaranteed power-buy-back price.
Basically a subsidy on photo-voltaic which was expensive for tax-payers but then Germany is rich (the richest in Europe) and the voters/tax-payers did push for doing the whole photo-voltaic generation project.
Many biz-mags have picked on the German photo-voltaic project.
But then the same biz-mags picked on wind 25 years ago when Denmark and Germany started doing wind generation.
And now those SAME biz-mags note that the initial high-investment in wind was of more benefit that loss to Denmark and Germany.

Regarding the line-co permit. It’s SAFETY-FIRST. If the linemen are out fixing a fault near you they want to know what is dead/live and what is back-feeding. Regarding the network layout questions you asked, I will be talking to 1 (maybe 2) project-manager electrical-engineers next week. I’ve copied your text and will get some info from them. Actually all the home generation tech is a HUGE deal to them – we’ll be talking about it here at GeekZone or EcoBob I’m sure. It was very interesting for me to here about the Vector deal. I’m going to find out what some others in the industry think.

Porboynz

110 posts

Master Geek
+1 received by user: 47

#930067 9-Nov-2013 17:53

I think it would be useful to get the opinion of an engineer from a line distribution company like Vector on the pitfalls or engineering considerations PV grid tie systems cause. My export voltage has been 240/241V most of the afternoon, in the evenings the supply is usually close to 231V. I would also like to understand better how PV energy does make its way back into the grid, I understand transformer theory well enough but I suspect that distribution transformers are optimised for one direction. I presume that Meridian is able to aggregate all the solar PV exports from its customers and gets paid for it on the spot market somehow.

Re the safety angle, the inverter is required to shut off automatically as soon as it detects a loss of mains voltage to protect lines workers, so no particular issue there except that the power goes off just like everyone's in a power failure.

"The inverter is designed to shut down in less than two seconds if there is a power outage. This is dictated by the AS/NZS.4777 and G.83 standards. As soon as the power outage is over, the inverter will automatically resume operation"

Now if my neighbour had a hydro scheme capability I would be offering a co-operative installation pronto. There is a company in New Plymouth exporting hydro generators all over the world. They make them from F&P smart drive motors, fantastic. 24 x 7 power generation, not much opportunity for this or wind power in a suburban environment.

***If only I did not know now what I did not know then***

nutbugs

272 posts

Ultimate Geek
+1 received by user: 47

Lifetime subscriber

#930089 9-Nov-2013 19:32

There is a company in New Plymouth exporting hydro generators all over the world. They make them from F&P smart drive motors, fantastic. 24 x 7 power generation, not much opportunity for this or wind power in a suburban environment.

We have a couple of turbines from these guys (Eco innovation) installed on a family property in the tararuas. They are the older models. Been in for several years now and just keep spitting out 8-900watts continuously. We have good head that helps and the stream keeps flowing even in summer. By far the best option. This setup is off grid, so we have a battery bank as well, is starting to get a bit tired. Batteries really need to be looked after well. Still, far cheaper than trying to get a grid connection, in fact we probably would not be able to get one if we wanted!

Would love to be able to set up hydro for home, but solar is the next best option :)

k14

631 posts

Ultimate Geek
+1 received by user: 94

#930097 9-Nov-2013 20:37

Porboynz: I think it would be useful to get the opinion of an engineer from a line distribution company like Vector on the pitfalls or engineering considerations PV grid tie systems cause. My export voltage has been 240/241V most of the afternoon, in the evenings the supply is usually close to 231V. I would also like to understand better how PV energy does make its way back into the grid, I understand transformer theory well enough but I suspect that distribution transformers are optimised for one direction. I presume that Meridian is able to aggregate all the solar PV exports from its customers and gets paid for it on the spot market somehow.

I think you are over thinking it. The line voltage is fairly much arbitrary, it has certain limits it fluctuates between during different parts of the day. The voltages are largely controlled by Transpower on the transmission grid via varying the voltage at the power stations. The lines companies have a few ways of varying the voltage in their network but they are very much the tail and not the dog. The sun hits your panels, creates a bit of current, your inverter changes it to AC, and then your neighbor uses the physical electrons you made flow out your lines. The inverter makes sure the voltage is correct so the system functions as required.

In terms of the billing side, Meridian (and Contact etc) do not aggregate the load and sell it on the spot market, the amount would be so insignificant it wouldn't be worth the time for someone to try and model their customers generation (although this could certainly change if it becomes more wide scale, but I don't see that happening in the near future). Remembering the spot market is a real time every second of the day market, they would need to know how much power you are going to generate tomorrow to be able to sell it there. Also the spot market is very much a computer model, it doesn't account for the physical electrons each company generates. Everyone generates into the national grid and everyone takes it out of the national grid. There is no way to know who generated every bit of power. Essentially what happens is that instead of buying a kw of power for one of their other customers in your street/suburb/town/city off the spot market it completely bypasses the national grid and goes straight from you to them. So when the monthly reconciliation is done for Meridian at the GXP (that stands for grid exit point) that your supply comes from on the national grid, they would have 1 less kw to buy than if you didn't sell them your solar.

In regards to the transformers, I am not an engineer but am pretty sure transformers don't care which way the current goes. They are an inanimate object (barring some having a tap changer to change the output voltage) so depending on which side has the load the current will flow from one side to other or vice versa.

Porboynz

110 posts

Master Geek
+1 received by user: 47

#930129 9-Nov-2013 22:05

Aha, to overthink it, that's exactly the challenge though. Your explanation about GXP's is helpful and makes a lot of sense. I understand that in NZ a power company can undertake 2 of 3 energy activities: a lines company, a retailer or a generator. No one company is allowed to be all three. I had considered that Meridian as a generator and a retailer could aggregate all its solar exports and somehow get paid for it, but your explanation makes more sense. They simply have to buy less, very elegant.

I am not at all concerned about my small PV installation, but I am interested in what the effects will be in NZ longer term when or if solar PV becomes more mainstream. The reports from Australia are telling, with their 240V standard, if the inverter shuts off at say 250V that's not a lot of head room at all. This is why I raised the theoretical scenario of all the houses in a residential GXP having solar causing a surplus of current at the wrong time of the day, the voltage spikes and they all start cycling off and on. Who will regulate the installations I wonder? Probably the lines company as its their responsibility to ensure reliable supply. Well, first in first served as they say, a bit like Xero shares.

***If only I did not know now what I did not know then***

k1wi

484 posts

Ultimate Geek
+1 received by user: 111

#930140 9-Nov-2013 23:25

My understanding was that power companies can be generators or retailers because they are in 'competitive' markets, but lines companies are separate because they are natural monopolies?

Anyone who can accurately forecast where the electricity industry is going is liable to make a killing.

There are a ton of variables and interactions (beyond just marginal and fixed costs i.e. hydrology, security of supply etc) that will have very profound influences on the industry.

P.s. Anyone interested in the NZ market should be aware of:
www.systemoperator.co.nz
em6live.co.nz
www.electricityinfo.co.nz/comitFta/ftaPage.hydrology

Pretty useful sites; I used to collect data on the NZ market every 5 minutes (pretty interesting over time) but haven't got around to fixing my database.

k1wi

484 posts

Ultimate Geek
+1 received by user: 111

#930227 10-Nov-2013 11:43

Just to clarify my previous response, I meant power companies can be generators and/or retailers, but lines companies cannot also be generators or retailers. For the reasons given previously.

I see on further investigation that distribution (lines) companies can produce unlimited amounts of renewable power within their network - i.e. I understand this is what Vector is doing.

The model raises some interesting questions - at what point do lines companies then become significant generators and was the market designed with foresight into a future with significant distributed supply?

As per:
Electricity Industry Reform Act 1998

Porboynz

110 posts

Master Geek
+1 received by user: 47

#930399 10-Nov-2013 21:06

Meridian Meter Install Delay and Finance
I decided to outsource the entire installation rather than buy in the components and do it myself. There were 2 key factors in this decision. One was not having ready access to all the components needed and the realisation that I would still need an electrician anyway. The other was the KiwiBank Sustainable Energy loan scheme where Kiwibank will provide an energy loan to existing mortgage holders in the form of a loan top up. They require the install to be done by a member of the Sustainable Energy Association or the Solar Association and for the installation to have a 10 year warranty. For this they waive any loan top up fees plus contribute up to $2000 towards the cost of the system over 4 years based on $800 in the first year and $400 per year for the next 3 years. That’s free finance when you do the sums on a $12k loan at 6% over 5 years, it just does not get better than that. (Borrow $12,000, 6% interest, 60 month term; $107 repayments 2 weekly, $1446 total interest paid) Note that currently the Kiwibank floating rate is 5.5%, but I used a more conservative 6% in my calculations, these low interest rates cannot last forever.

Some folk will have $12k sitting in a bank account earning interest and will not need to arrange a loan. For them the calculation is the cost of the net interest after tax. If I had to pay the $1446 interest then my payback calculations would have been extended another 2 years, approx 10 years total. The decision to go ahead would have been much more difficult.

There was about 2 months delay in proceedings while I got the roof repainted, which was an experience in itself. Once the loan was arranged I paid a deposit to Tim from Solarcraft. Tim sent off an application to the lines company Vector to get approval from them for the install.

The day my installation was completed Tim turned on the inverter to check operation and then turned it off again using the DC and AC isolation switches on the inverter and the circuit breaker in the fuse board. He did this because without the correct Import Export meter, any power generated was registered by the meter as more power consumed, not generated! The installation was inspected and passed the same day by an approved electrical inspector so I submitted an application to Meridian to have the Import Export meter fitted. A very helpful person recorded the details telling me it should be done within 2 weeks, 30 days maximum. And so I waited, and the sun shone and still I waited. After 25 days or so I enquired about progress and was informed it was 30 business days and to let them know if it was not completed within 30 business days and they would consider some sort of credit. This was no good, I was not interested in a credit, I wanted to operate my latest toy! After 28 business days the contractor called me to arrange the install and explained they had run out of Import Export meters, hence the delay. Apparently others had waited much longer than me so perhaps I should consider myself lucky? The meter install took about 90 minutes and on Monday 14th October at 10am the inverter was switched on.

Here are the questions Meridian need answered for the meter install:
- How many phases is the current supply to the property?
- If two or three phase, will export be on one phase or all?
- Any other changes to the existing metering?
- Are all the current meters being replaced?
- What is the name and contact number of your electrician

I did ask Meridian by email if I could have applied for the meter install ahead of the install, but they did not answer, I think you probably could, so that was a project management stuff up on my part. It was a very frustrating time, we had an unseasonal spell of fine sunny weather just to make it even more annoying.

***If only I did not know now what I did not know then***

richms

29105 posts

Uber Geek
+1 received by user: 10222

Trusted

Lifetime subscriber

#930435 10-Nov-2013 21:45

Is there a limit to the number of stand-alone inverter/panel combos you can have installed at a single property?

As in, if I was to take the vector deal on the shed since thats not going anywhere for a looooong time, and then wanted to put an independant non battery one onto the extension when it is done, would there be any interaction issues between them, or even could I get permission to connect the second one up?

Would having 3 phase make any difference? Will be getting that when it comes time to relocate the breaker panel inside regardless.

Richard rich.ms

Porboynz

110 posts

Master Geek
+1 received by user: 47

#930439 10-Nov-2013 21:54

Well it seems to me that you could easily have each system on a separate phase once you have 3 phase installed. I do not think there would be any issue having multiple inverters on the same property on the same single phase either, with or without the Vector batteries. There might be something in Vector's fine print however.

***If only I did not know now what I did not know then***

Parewanui

30 posts

Geek
+1 received by user: 3

#931030 11-Nov-2013 20:34

@Porboynz + @nutbugs

The Tararua Range – I have fond memories from many years tramping up there – in the rain.
No wonder your family farm has hydro.
Search ‘mangahao dam’ and you get a small commercial hydro station in the Tararua Range.
I’ve been up the river that feeds the dams many times and one time in flood – that was impressive.

In my first post was this link Eco Innovation website for solar: goo.gl/WPBUCG
And this is their sister website for hydro-generators: www.powerspout.com

@nutbugs, can you read this PDF? goo.gl/eIhNXV
It would be good if you can do a similar appraisal of the plant on your family farm?
I am going to get Tugos, but I suspect you have the original Pelton model?
It could be a new forum you start, and I would add the hydro project I’m doing?

Regarding replacing batteries, I think the best deal is still, 2nd-hand deep-cycle forklift batteries. The sealed-lead-acid ones at Eco Innovation and others are low-maintenance/easy-care but costly. Lead-acid batteries still only has a 5-8 year life. But I read the USA is working on this type of battery to improve the tech. The have 50k-population-towns so far of the main grid, that it’s cheaper to install a large building of lead-acids than upgrade their feeder town-to-main-grid!?!? This is for handling the 3 evenings each week of peak-demand (tv-soap-night / doing the ironing / coffee-machine / air-con all at once – go figure!?!?).

Beside VAWT’s I think the materials science work going into Li-batteries looks interesting. The ink-jet printing of the Li/polymer layers to create more spaces; making the battery hold more change, lighter, quicker to charge, and cheaper to make too is impressive. I want to find out more about the Li-batteries Vector are using.

@Porboynz, I am not sure what you mean by ‘co-operative installation’, except to say micro-hydro is commodity gear. Eco Innovation have so many live-customers the install price is known and the output is known. Far less risk than PV or Wind.

Here’s a more interesting example (I think anyway) and it’s real in NZ with names changed...
Hydro-engineer-tauranga- biz has many projects on the go at various stages of planning and implementation.
Hydro-engineer-tauranga- biz finds streams/rivers suited to their hydro-generation plant.
Hydro-engineer-tauranga- biz signs up Farmer- te-kuiti-biz whose land the stream flows through.
Hydro-engineer-tauranga- biz designs a $200k plant (about the size of a small woolshed).
Energy-broker-biz signs up Fruit-drink-factory-biz in Auckland to buy all the plant’s output for 15 years.
Bank-biz finances the whole thing, leaving Farmer- te-kuiti-biz with a monthly power income, Fruit-drink-factory-biz with a steady known electricity price, and Hydro-engineer-tauranga- biz with another project to do.

Woops – I’m off topic again, so back to PV...

@Porboynz, the post on your installation was very interesting – thanks again for sharing.
I talk to the lines-co electrical-engineers on Thu.
We’ll see what info I can get and what I’m allowed to write up.

So, Vector and a whole lot of independents are doing-it!
I guess the other biggies will be too at some stage, and here’s why...
goo.gl/YBcv1G
goo.gl/Flgi4A

nutbugs

272 posts

Ultimate Geek
+1 received by user: 47

Lifetime subscriber

#931231 12-Nov-2013 09:43

Parewanui:

@nutbugs, can you read this PDF? goo.gl/eIhNXV
It would be good if you can do a similar appraisal of the plant on your family farm?
I am going to get Tugos, but I suspect you have the original Pelton model?

Yep - that brings back memories. I installed most of it myself - it is in pretty rugged country!
Yes - we do have the older pelton turbines in the metal cases. I do like what they have done with housings etc for the powerspout brand. Look much more robust.

It could be a new forum you start, and I would add the hydro project I’m doing?

Hmmmm - You have got me thinking there. I could dredge out some info and photos and give a run down of what we did and how it has worked and is working.

Regarding replacing batteries, I think the best deal is still, 2nd-hand deep-cycle forklift batteries. The sealed-lead-acid ones at Eco Innovation and others are low-maintenance/easy-care but costly. Lead-acid batteries still only has a 5-8 year life.

Yes - ours are near end of life now - probably been about 7 years. As you say - expensive!

Anyway - hijacking the thread here - back to the PV on the roof with a grid tie - I shall ponder kicking off a micro-hydro thread sometime soon :)

Parewanui

30 posts

Geek
+1 received by user: 3

#936629 18-Nov-2013 14:02

Pertinent post at /.

Arizona Approves Grid-Connection Fees For Solar Rooftops...
http://hardware.slashdot.org/story/13/11/16/1422227/arizona-approves-grid-connection-fees-for-solar-rooftops

Not that the fee is a good thing.
But then The article has some interest gems like...
'Arizona Public has about 18,000 solar customers'
(pop. 6.5million, sunny climate)

I've still to talk to the electrical-engineers about PV systems.
Last week we talked proper work so I did not get a change to ask the questions from Porboynz.
But I expect to talk to them again this week.

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | ... | 25