3kW Grid Tied Solar PV: Watts and Warts.

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30 posts

Geek

#929387 8-Nov-2013 13:22

Impressive work and thank you for sharing. I linked this discussion at Ecobob: goo.gl/oCGr4V . I am most jealous that your wife let you install solar thermal and photo-voltaic. I have a garage roof perfect for easy installations and I hope that eventually my wife lets me do the same as you.

Last year - 2012 on an August Saturday Germany hit 100% of electricity demand supplied by solar. The day before, a Friday, with factories and offices working it was 50%. I guess (hope) NZ is looking to do the same - be it at the usual NZ-time-frame of many years after all the main players.

In terms of watching photo-voltaic creep towards main-stream in NZ, I've been tracking panel prices.
A pellet of panels provides, very approximately, enough electricity for a 4-person family home off-grid system (not your average NZ scenario I admit).
In 2002 a pellet of solar panels was $35k.
In 2011 it as $7k.
In 2013 (today) $5k. goo.gl/WPBUCG
I wonder when the panels + other kit + installation hits a price that the pay-back is 2 years?
That seems to be the magic number dictating main-stream uptake.

Comparing wholesale electricity pricing in NZ:
In 1997 average WHOLESALE 04c/kWh (VERY approx. retail (you pay) price 14c/kWh).
In 2012 average WHOLESALE 10c/kWh (VERY approx. retail (you pay) price 39c/kWh).
(Retail electricity price calc'ed by (year total $-kWh-chg + $-line-chg) / (year total kWh) for some homes - so a VERY approximate calculation but a useful starter comparison)

Will the electricity price continue to be a political-game?
For example, will the govt need to buy back the electricity companies again?
Because their share-price drops very low because they become non-competitive compared to solar in some years time?
So how can you plan long-term the return on your installation?

To me it seems:
- There are many benefits to solar that justify doing it today.
- The 2 year pay-back will come in the near future (only some years?) no mater what the political-games.

It's going to be a big discussion topic at many forums and political venues.
So, again, thanks for starting this topic.

k1wi

484 posts

Ultimate Geek

#929420 8-Nov-2013 13:50

Parewanui: Last year - 2012 on an August Saturday Germany hit 100% of electricity demand supplied by solar. The day before, a Friday, with factories and offices working it was 50%. I guess (hope) NZ is looking to do the same - be it at the usual NZ-time-frame of many years after all the main players.

The big issue with Germany is it's really ramping up power costs and actually threatening supply. I read an excellent report on the situation in the Economist and some power generators in Germany have been [i]charged[i] for supplying power to the grid during periods of high solar supply (it's really not easy to turn base load generators off in a hurry). It'll be interesting to see where Germany goes from here and at what point solar/wind do threaten grid stability, if they do at all.

With grid-tied systems the grid is pretty essential so expect the generators to claw back more where they can (potentially from solar users rather than at the expense of all users). As the OP was saying, lucrative for early adopters, but diminishing returns for latter entrants. Never mind that solar is only competitive if the net cost of distributed power generation is less than the net cost of centralised power generation (economies of scale etc). It's easy to beat thermal generation costs, but hydro on the other hand...

In NZ the stability/efficiency problem is exacerbated because much of our hydro is run-of-the-river and considered baseload (due to resource consents re: minimum flows), variable such as wind, or true baseload (geothermal). Further, peak demand here is when solar is producing least (winter, at 8:30am and again ~7pm at night). With the grid still essential for grid-tied, solar may become cheaper, but those gains may be offset by higher grid connection costs passed onto consumers. After all, large-scale solar will exacerbate the base/peak ratios - we have low grid demand at night (potentially offset by electric cars(?)) and during the day, with two big peaks: at breakfast and then at dinner time.

Parewanui:
To me it seems:
- There are many benefits to solar that justify doing it today.
- The 2 year pay-back will come in the near future (only some years?) no mater what the political-games.

Two year payback seems a little steep - effectively it should be when the ROI is seen/perceived to be greater than investing that amount of money elsewhere/cost of borrowing, but then households will still be limited by their ability to finance the large upfront cost and predict the future returns...

As to the political involvement in power... Remember the government is still the largest shareholder of power companies ;)

k14

629 posts

Ultimate Geek

#929443 8-Nov-2013 14:22

Parewanui: Impressive work and thank you for sharing. I linked this discussion at Ecobob: goo.gl/oCGr4V . I am most jealous that your wife let you install solar thermal and photo-voltaic. I have a garage roof perfect for easy installations and I hope that eventually my wife lets me do the same as you.

Last year - 2012 on an August Saturday Germany hit 100% of electricity demand supplied by solar. The day before, a Friday, with factories and offices working it was 50%. I guess (hope) NZ is looking to do the same - be it at the usual NZ-time-frame of many years after all the main players.

In terms of watching photo-voltaic creep towards main-stream in NZ, I've been tracking panel prices.
A pellet of panels provides, very approximately, enough electricity for a 4-person family home off-grid system (not your average NZ scenario I admit).
In 2002 a pellet of solar panels was $35k.
In 2011 it as $7k.
In 2013 (today) $5k. goo.gl/WPBUCG
I wonder when the panels + other kit + installation hits a price that the pay-back is 2 years?
That seems to be the magic number dictating main-stream uptake.

Comparing wholesale electricity pricing in NZ:
In 1997 average WHOLESALE 04c/kWh (VERY approx. retail (you pay) price 14c/kWh).
In 2012 average WHOLESALE 10c/kWh (VERY approx. retail (you pay) price 39c/kWh).
(Retail electricity price calc'ed by (year total $-kWh-chg + $-line-chg) / (year total kWh) for some homes - so a VERY approximate calculation but a useful starter comparison)

Will the electricity price continue to be a political-game?
For example, will the govt need to buy back the electricity companies again?
Because their share-price drops very low because they become non-competitive compared to solar in some years time?
So how can you plan long-term the return on your installation?

To me it seems:
- There are many benefits to solar that justify doing it today.
- The 2 year pay-back will come in the near future (only some years?) no mater what the political-games.

It's going to be a big discussion topic at many forums and political venues.
So, again, thanks for starting this topic.

I think you will find that is a very long way away, if ever. The price of solar would have to drop massively and even then you never get around the basic facts that the bulk of NZ's power usage is in winter (when solar output is at it's lowest) and the peaks nearly always occur when it is dark. Not to mention the fact that the power companies could change the buy back rates at any moments notice and as more people install solar the lower the buy back rates will get. The buyback from Contact and Meridian is very much a token gesture (the other power companies either aren't involved or give very pitiful rates) because all it does is undermine their billion+ dollar investments in hydro, thermal and geothermal plants. With things as they are at the moment I don't think things will change too much (from the generators) but if the panel price continues to drop then expect the power companies to probably drop the buy back rates at similar rates. With the current setup of the NZ market it not in the generators interest to have wide scale micro generation. That is unless the government intervenes.....

P.S. Using that statement about Germany is grossly misleading. Life is very easy when you can rely on a grid that has interconnections to multiple other countries who have thermal and nuclear generation at their beckon call but down here in little ole NZ we have to be self sufficient. When the sun stops shining or the wind stops blowing you need to have thermal or hydro generation ready to come on at a moments notice to replace it. Someone (us) has to pay to build those plants so for every bit of solar/wind you need to have the equivalent MW of thermal/hydro available in case one day the sun doesn't shine or the wind doesn't blow. Building that more than doubles the cost of building the wind/solar to the whole country so in practice it is usually just easier to only build the predictable generation asset, that is until politicians get involved then logic all goes out the window!

wongtop

563 posts

Ultimate Geek

#929448 8-Nov-2013 14:30

Sure the power companies can play the game for a while, but if the cost of solar and storage keeps falling, at some point it will be economic to simply disconnect (especially if you get heating, cooking with gas), so there are limits to the games that they can play.

Ultimately I think that PV will become an de facto price cap on retail electricity, and personally I think we are close to that cap now.

k14

629 posts

Ultimate Geek

#929461 8-Nov-2013 14:45

wongtop: Sure the power companies can play the game for a while, but if the cost of solar and storage keeps falling, at some point it will be economic to simply disconnect (especially if you get heating, cooking with gas), so there are limits to the games that they can play.

Ultimately I think that PV will become an de facto price cap on retail electricity, and personally I think we are close to that cap now.

Yep, spot on. That is what the power companies have found out over the last few years, they used to think they could just keep putting the retail prices up and up and up, but what has happened is that demand has decreased at the same rate as prices have increased and thus revenue has been relatively static.

Although the difference in cost of a grid tied solar system vs a stand alone system is quite massive, so I think there is still a bit of room to move yet. I believe the long run cost of a newly built geothermal generator (probably the best indication for current large scale NZ generation) is around $75 per MWhr. So solar has a fair way to drop before it starts to compete. If it does get to that point it will bring an interesting paradox to the table for how distribution lines companies run. If people start disconnecting from the grid then the cost of maintenance of the local network will probably not decrease proportionately. So you will have less people paying for the same amount of upkeep and thus it will make it even more attractive to go off the grid, then the death spiral begins!

k1wi

484 posts

Ultimate Geek

#929476 8-Nov-2013 14:52

k14:
wongtop: Sure the power companies can play the game for a while, but if the cost of solar and storage keeps falling, at some point it will be economic to simply disconnect (especially if you get heating, cooking with gas), so there are limits to the games that they can play.

Ultimately I think that PV will become an de facto price cap on retail electricity, and personally I think we are close to that cap now.

Yep, spot on. That is what the power companies have found out over the last few years, they used to think they could just keep putting the retail prices up and up and up, but what has happened is that demand has decreased at the same rate as prices have increased and thus revenue has been relatively static.

Although the difference in cost of a grid tied solar system vs a stand alone system is quite massive, so I think there is still a bit of room to move yet. I believe the long run cost of a newly built geothermal generator (probably the best indication for current large scale NZ generation) is around $75 per MWhr. So solar has a fair way to drop before it starts to compete.

Nevermind new installed capacity has to compete with the marginal cost of existing capacity - I imagine you'll see thermal shutdown first (potentially at the risk of security in dry years) and then it'll be a battle over existing renewables and economies of scale vs. efficiencies associated with local consumption.

wongtop

563 posts

Ultimate Geek

#929477 8-Nov-2013 14:54

k14:
wongtop: Sure the power companies can play the game for a while, but if the cost of solar and storage keeps falling, at some point it will be economic to simply disconnect (especially if you get heating, cooking with gas), so there are limits to the games that they can play.

Ultimately I think that PV will become an de facto price cap on retail electricity, and personally I think we are close to that cap now.

Yep, spot on. That is what the power companies have found out over the last few years, they used to think they could just keep putting the retail prices up and up and up, but what has happened is that demand has decreased at the same rate as prices have increased and thus revenue has been relatively static.

Although the difference in cost of a grid tied solar system vs a stand alone system is quite massive, so I think there is still a bit of room to move yet. I believe the long run cost of a newly built geothermal generator (probably the best indication for current large scale NZ generation) is around $75 per MWhr. So solar has a fair way to drop before it starts to compete. If it does get to that point it will bring an interesting paradox to the table for how distribution lines companies run. If people start disconnecting from the grid then the cost of maintenance of the local network will probably not decrease proportionately. So you will have less people paying for the same amount of upkeep and thus it will make it even more attractive to go off the grid, then the death spiral begins!

You have to remember though that PV (with storage) is not competing with wholesale at 7.5c/kWh, but with retail at 20+c/kWh. Like you say this will start to put the price pressure on right through the chain, from the generators through to the lines companies.

Parewanui

30 posts

Geek

#929481 8-Nov-2013 14:56

k1wi:
Parewanui: Last year - 2012 on an August Saturday Germany hit 100% of electricity demand supplied by solar. The day before, a Friday, with factories and offices working it was 50%. I guess (hope) NZ is looking to do the same - be it at the usual NZ-time-frame of many years after all the main players.

The big issue with Germany is it's really ramping up power costs and actually threatening supply. I read an excellent report on the situation in the Economist and some power generators in Germany have been [i]charged[i] for supplying power to the grid during periods of high solar supply (it's really not easy to turn base load generators off in a hurry). It'll be interesting to see where Germany goes from here and at what point solar/wind do threaten grid stability, if they do at all.

With grid-tied systems the grid is pretty essential so expect the generators to claw back more where they can (potentially from solar users rather than at the expense of all users). As the OP was saying, lucrative for early adopters, but diminishing returns for latter entrants. Never mind that solar is only competitive if the net cost of distributed power generation is less than the net cost of centralised power generation (economies of scale etc). It's easy to beat thermal generation costs, but hydro on the other hand...

In NZ the stability/efficiency problem is exacerbated because much of our hydro is run-of-the-river and considered baseload (due to resource consents re: minimum flows), variable such as wind, or true baseload (geothermal). Further, peak demand here is when solar is producing least (winter, at 8:30am and again ~7pm at night). With the grid still essential for grid-tied, solar may become cheaper, but those gains may be offset by higher grid connection costs passed onto consumers. After all, large-scale solar will exacerbate the base/peak ratios - we have low grid demand at night (potentially offset by electric cars(?)) and during the day, with two big peaks: at breakfast and then at dinner time.

Parewanui says:
Some years back now the German-public agreed to the govt investing in wind and solar.
It has been an expensive time for them.
But the Germans seem to look at a 21 year view.
It seems the German voter is saying, ok, invest now, I'm paying for the future of my family.

Base-load I believe is a political-problem.
In a true engineering (as in building plant) situation and a real competitive-business-environment it would not be an issue.
I can see base-load handled regionally by commodity low-tech plant.
I'm not going to try justifying this here.
Parewanui ends:

Parewanui:
To me it seems:
- There are many benefits to solar that justify doing it today.
- The 2 year pay-back will come in the near future (only some years?) no mater what the political-games.

Two year payback seems a little steep - effectively it should be when the ROI is seen/perceived to be greater than investing that amount of money elsewhere/cost of borrowing, but then households will still be limited by their ability to finance the large upfront cost and predict the future returns...

As to the political involvement in power... Remember the government is still the largest shareholder of power companies ;)

Parewanui says:
2-year pay-back IS STEEP even using simple calc's - but it is true that it has occurred in many markets in human history.
E.g. the plant cost $4.5k and my power bill is $2.4k/year so yes I do get a 2 year pay-back (not true accounting ROI).
I said <some> years.
Will the example above occur in 3 years? 7 years? 21 years?
Solar gear is fast becoming commodity gear (around the world, but not yet in NZ).
Even ignoring the massive over-supply of panels yanking the price around.
2-year payback is now, 2013, in some examples, but not NZ, so when in NZ?

NZ is not a real competitive market.
NZ is too small.
NZ is an island so limiting the border competitive pressures.
Will the NZ electricity-price be political compared to competitive forever?
I cannot see the electricity companies being super valuable.

I think MY REPLY is off-topic compared to the topic-starter.
My initial post was really because some posters were talking electricity pricing and pay-back.
I see others taking issue with my post but I'll not reply except with this one.
I think I should stick to discussing INSTALLING solar compared to the commercial (Vector + others) offerings.
The forum discussions on Germany, electricity generation options, and pricing are MASSIVE out there on the Internet!?!?!
My 21 years in the electricity industry and 33 years working say to me that the solar industry will be MASSIVE and profitable and beneficial to humans and earth.
Parewanui ends:

Parewanui

30 posts

Geek

#929512 8-Nov-2013 15:21

This bit got lost in my reply post so again....

Parewanui says:
Some years back now the German-public agreed to the govt investing in wind and solar.
It has been an expensive time for them.
But the Germans seem to look at a 21 year view.
It seems the German voter is saying, ok, invest now, I'm paying for the future of my family.

Base-load I believe is a political-problem.
In a true engineering (as in building plant) situation and a real competitive-business-environment it would not be an issue.
I can see Base-load handled regionally by commodity low-tech plant.
I'm not going to try justifying this here.
Parewanui ends:

Porboynz

110 posts

Master Geek

#929674 8-Nov-2013 19:08

k14: Did you do any analysis on Contact vs Meridian in terms of your expected output? Doing a quick calculation I think the per monthly generation required before Contact becomes a better proposition than Meridian is approx 380kWhr, or around 12-13kWhr per day. At your current output you are easily exceeding this, although things skew the other way in winter. Although this doesn't take into account the other usage rates of the two retailers, which could skew it one way or the other.

If you have already said this I apologise but have you calculated what your expected annual generation will be and what this is per month? I live in Central Otago so think the short winter days may not make it the most lucrative project but maybe the longer summer days could help balance it out?

k14 I plan to record the Import, Export and overall usage once I get to 30 days after switch on. I will be sure to post my findings then, until I have hard data everything is a bit vague I regret. Here is what I have so far, remember I turned it on Monday 14th at 10am

Inverter
Lifetime 373kWh over 329 hours
Average daily production 13.3kWh

Meter
Imported 365kWh
Exported 194kWh

Assumptions
Solar used by house is 373-194=179kWh
Total House consumption is 179+365=544kWh

From here you can calculate all sorts of trivia, which I plan to do after 30 days/1 month in 6 days time. I went with my installers recommendation to change to Meridian, plus it felt right to me when I did a fag packet comparison. I may have been wrong but that's what I am setting out to discover when I have valid data.

Note edited to fix obvious error, should not drink and keyboard

Porboynz

110 posts

Master Geek

#929686 8-Nov-2013 19:53

k1wi: Really appreciate the info mate,

From my back of the envelope calculations you only spent an extra 50c a day for the first 18 days of the month ($9 total) being on the low usage plan over the standard usage plan, but saved you the same over the 13 you had solar ($7) so no big deal eh?

The solar's saving you ~$110 a month, assuming no change in overall usage, for a pay back of approx 9 years excluding all the additional variables such as opportunity cost, future power price changes etc (increase in house price, depreciation)...

I'd call that probably close to best case scenario as your panels are at their prime orientation for this time of the year (when solar strength is getting close to its strongest and longest), but offset by any demand shifting you can do as you get use to the system - shifting those 2KWh/day sold back @10c to sunshine hours would make a decent difference over time (Some people put the freezer on a timer and cycle it off over night when it usually remains closed, to come on again once the sun comes up... Not that I'm suggesting you try that!)

I think most interestingly for me is the relationship between the three 'plans' low, low with solar, standard without solar and how that influences your returns - it really puts an incentive on demand shifting towards daytime hours, or perhaps even grid-tied with a battery option (for those 7 KWh sold back to the grid each day).

Excuse me for taking your bill apart, again, I appreciate the amount of info re: numbers.

k1wi, thanks for taking an interest, I like the idea of the freezer on a time clock, I would need to monitor the temp carefully though. Thx also for the reassurance over the plan change, I was really surprised when it was applied retrospectively, the broadband market does not operate the same way sadly, imagine if it did. Battery operation seems to be an expensive option if you have grid available, different situation if you are in a remote location and grid connection is expensive. The life of a battery bank and its cost and maintenance is also a concern, keeping the battery in my classic car charged is enough effort. Using the grid as a battery works for me at the moment, but I understand the risk of the retailer changing the buyback, plus there are technical issues if there are too many solar installations with AC voltage levels and usage patterns.

I plan to post some info on the finance angle soon, the $12k I spent has an opportunity cost, or does it? (If I had the $12k in the bank what net interest can it earn versus solar, if I borrowed the $12k what is the cost of finance)

Porboynz

110 posts

Master Geek

#929692 8-Nov-2013 20:11

Amosnz:
Porboynz:

- 0.55kWh average background usage during daytime hours 365 days of the year

.

Awesome thread, I'll be following with interest.
I installed an Efergy Energy Monitor a few months ago, and interestingly my base\background usage is about 0.5kW as well (although I work from home so my base usage is overnight).
Here is an image of my last 24 hours usage.

Amosnz, nice work identifying your usage, I took a look at my usage over the last 24 hours now that 1 person is at home studying, what a difference! My base load 550w is now from about 10pm through to about 5am when the HW element booster kicks in to make sure my morning shower is OK.

The rest of the day shows lots of assorted usage. Some of this is being provided by the panels so all good.

Porboynz

110 posts

Master Geek

#929699 8-Nov-2013 20:26

Parewanui: This bit got lost in my reply post so again....

Parewanui says:
Some years back now the German-public agreed to the govt investing in wind and solar.
It has been an expensive time for them.
But the Germans seem to look at a 21 year view.
It seems the German voter is saying, ok, invest now, I'm paying for the future of my family.

Base-load I believe is a political-problem.
In a true engineering (as in building plant) situation and a real competitive-business-environment it would not be an issue.
I can see Base-load handled regionally by commodity low-tech plant.
I'm not going to try justifying this here.
Parewanui ends:

Some interesting observations Parewanui, I really appreciate your detail around retail and wholesale unit pricing over the years. If you have been involved in the energy sector perhaps you can help fill in some gaps in my understanding. What do lines companies call an area fed by a large street transformer? Is its a sector or a zone or some industry specific name? I have one outside my property, its green, about 2.5 metres by 1.5 metre and 1.5 metres high with cooling etc. I presume its an 11kV to 230V transformer? I understand that my inverter exports to the grid by lifting the voltage slightly above that of the power lead-in cable so the current reverses direction. It seems to me if all my neighbours had panels then the voltage would rise exponentially as we all tried to export power to each other. I suspect this is why I had to get a permit from Vector the lines company first. Can this exported power be transmitted backwards through a standard distribution transformer such as the one outside my house or must all my exported energy be used by my neighbours? How many houses are typically fed by one of these street transformers?

naggyman

697 posts

Ultimate Geek

#929719 8-Nov-2013 20:52

Porboynz: I understand that my inverter exports to the grid by lifting the voltage slightly above that of the power lead-in cable so the current reverses direction. It seems to me if all my neighbours had panels then the voltage would rise exponentially as we all tried to export power to each other. I suspect this is why I had to get a permit from Vector the lines company first. Can this exported power be transmitted backwards through a standard distribution transformer such as the one outside my house or must all my exported energy be used by my neighbours? How many houses are typically fed by one of these street transformers?

According to wikipedia that isn't true - but it is wikipedia so take it with a grain of salt.

Morgan French-Stagg

morgan.french.net.nz

k14

629 posts

Ultimate Geek

#929729 8-Nov-2013 21:07

Porboynz:Some interesting observations Parewanui, I really appreciate your detail around retail and wholesale unit pricing over the years. If you have been involved in the energy sector perhaps you can help fill in some gaps in my understanding. What do lines companies call an area fed by a large street transformer? Is its a sector or a zone or some industry specific name? I have one outside my property, its green, about 2.5 metres by 1.5 metre and 1.5 metres high with cooling etc. I presume its an 11kV to 230V transformer? I understand that my inverter exports to the grid by lifting the voltage slightly above that of the power lead-in cable so the current reverses direction. It seems to me if all my neighbours had panels then the voltage would rise exponentially as we all tried to export power to each other. I suspect this is why I had to get a permit from Vector the lines company first. Can this exported power be transmitted backwards through a standard distribution transformer such as the one outside my house or must all my exported energy be used by my neighbours? How many houses are typically fed by one of these street transformers?

Thats a fairly simplistic view but basically how it happens. Transformers can go both ways so wouldn't be worried about that. However with AC there are a lot of complicated factors that come into play with line inductance/capacitance that could effect how your system performs. The lines companies have quite strict performance standards they have to maintain so want to know the full details of everyone's installations to ensure the network voltage etc is kept within allowable limits. I wouldn't be too worried about it though, in future years things could get complicated but currently with only the odd person doing it the networks would hardly notice it.

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