Solar PV - Grid Connected System

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Niel

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#799827 15-Apr-2013 20:13

Skolink: NIWA have quite a useful tool here.

Great tool (which comes in handy for a project I'm working on ;-), but keep in mind they show the energy that the sun drops on a solar collector ignoring it's efficiency. According to Wikipedia, the best mass produced cells capture about 175W per sqm when radiated with 1000W per sqm of sunlight. New development in flexible films promises over 350W per sqm by 2019, but that is some time ago and not in mass production. At the start of this year First Solar announced a record breaking 187W per sqm cell for mass production. Note when the cell is assembled into a panel with protection it drops about 2%-3%. Also performance is measured at 25 degree C.

We use a fair bit of power, about 30kWh per day, so to run off the grid we need about 60 sqm of panels and lots of batteries to store the energy. It makes much more sense to get solar water heating. The Wikipedia page for solar water heating suggests saving about 6.5kWh per day and typically payback is 6 or 7 years in various countries except UK and USA where it is 12 years.

Note you need a resource consent to add solar panels to your roof. And if solar water heating, then you cannot get a discount for using a ripple controller as there is nothing to control. So it might make more sense to get a heat pump water heater (if your climate is not too cold) and still get the discount for a ripple controller, then in Summer you can also use the exhaust to cool your home.

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benmurphy66

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#799828 15-Apr-2013 20:17

Niel:
Skolink: NIWA have quite a useful tool here.

Great tool (which comes in handy for a project I'm working on ;-), but keep in mind they show the energy that the sun drops on a solar collector ignoring it's efficiency. According to Wikipedia, the best mass produced cells capture about 175W per sqm when radiated with 1000W per sqm of sunlight. New development in flexible films promises over 350W per sqm by 2019, but that is some time ago and not in mass production. At the start of this year First Solar announced a record breaking 187W per sqm cell for mass production. Note when the cell is assembled into a panel with protection it drops about 2%-3%. Also performance is measured at 25 degree C.

We use a fair bit of power, about 30kWh per day, so to run off the grid we need about 60 sqm of panels and lots of batteries to store the energy. It makes much more sense to get solar water heating. The Wikipedia page for solar water heating suggests saving about 6.5kWh per day and typically payback is 6 or 7 years in various countries except UK and USA where it is 12 years.

Note you need a resource consent to add solar panels to your roof. And if solar water heating, then you cannot get a discount for using a ripple controller as there is nothing to control. So it might make more sense to get a heat pump water heater (if your climate is not too cold) and still get the discount for a ripple controller, then in Summer you can also use the exhaust to cool your home.

Consents depend on the council. here is kapiti a consent is not required for PV Panels but is for hot water heating panels.

Skolink

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#799843 15-Apr-2013 20:39

benmurphy66: Consents depend on the council. here is kapiti a consent is not required for PV Panels but is for hot water heating panels.

Same here in Christchurch, but outside the city limits in Waimakariri District Council jurisdiction you need a consent for both.

Skolink

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#799855 15-Apr-2013 20:49

Niel:
Skolink: NIWA have quite a useful tool here.

Great tool (which comes in handy for a project I'm working on ;-), but keep in mind they show the energy that the sun drops on a solar collector ignoring it's efficiency.

See the example page. They suggest an efficiency of 9%. The panels I'm looking at getting are 1.8x0.9m, 250W ~154W/m2

Niel:
And if solar water heating, then you cannot get a discount for using a ripple controller as there is nothing to control. So it might make more sense to get a heat pump water heater (if your climate is not too cold) and still get the discount for a ripple controller, then in Summer you can also use the exhaust to cool your home.

The HWC still has an electric element in it. Ours is ripple controlled, so if the weather is cloudy our water is heated at night.

richms

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#799876 15-Apr-2013 21:10

Just wind the thermostat all the way down and keep the controlled element. also means you can turn it back up if your pump dies or whatever.

Richard rich.ms

nickb800

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#799899 15-Apr-2013 22:02

Its a bit complicated interfacing solar with a hot water cylinder - for instance you need a booster heater to periodically ensure any legionella bacteria doesn't grow in the cylinder - it's not as simple as winding down the thermostat

Seeing as you are in Kapiti I recommend that you AVOID solarzone - we had a bad experience with them. They installed a solar hot water system in our new build, which has had several issues, but worst of all they didn't seal the pipe connections to the solar panel properly, thus we ended up with antifreeze leaking out of the closed loop onto the roof and into our rainwater supply. At this point we would be willing to accept them remedying the subsequent mess, but they staunchly denied all responsibility (despite the council green plumbing advisor, our plumber, our water tank guy, etc all agreeing it was their fault).

benmurphy66

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#799901 15-Apr-2013 22:06

nickb800: Its a bit complicated interfacing solar with a hot water cylinder - for instance you need a booster heater to periodically ensure any legionella bacteria doesn't grow in the cylinder - it's not as simple as winding down the thermostat

Seeing as you are in Kapiti I recommend that you AVOID solarzone - we had a bad experience with them. They installed a solar hot water system in our new build, which has had several issues, but worst of all they didn't seal the pipe connections to the solar panel properly, thus we ended up with antifreeze leaking out of the closed loop onto the roof and into our rainwater supply. At this point we would be willing to accept them remedying the subsequent mess, but they staunchly denied all responsibility (despite the council green plumbing advisor, our plumber, our water tank guy, etc all agreeing it was their fault).

Thanks for the heads up, the were on my short list.

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Handle9

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#799919 15-Apr-2013 22:35

benmurphy66:
Handle9: If you want to retrofit microgeneration of any kind don't expect an economic return. The payback for most systerms , other than home made solutions aren't reasonable.

Doing on a new build is a little better but still nowhere near sub 10 year returtns .

Out of interest what do you base this on? the numbers seem to make sense to me if you intended to live in the house for say 10 years. Just not sure if real world experience is the same as what the sales people are providing.

As others have said, maintenance costs are significant. Typically domestic systems aren't particularly well made compared to industrial systems (which of course are even more expensive). You get one failure outside the warranty period and all of a sudden paybacks go through the roof.

If you have a battery system it's even worse. Batteries aren't really rated by time period, they are rated by cycles. If you deep cycle your batteries daily then you can chew through batteries very quickly.

pmonro

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#799963 16-Apr-2013 06:19

benmurphy66: I am looking at installing a PV based Solar Power system in my house. it will be grid connected and I am interested to see if anybody has one currently and could share their experience with how well it works or doesn't work.

most interested with how much they find they use vs export etc.

pmonro

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#799977 16-Apr-2013 07:53

My approach to economic return is to reduce installation cost and reduce electricity from the utility.
I estimate I can install 2kw, 8X250w panels ground mounted.
solar panels..........................2600
convertor china import............700
cables, AC&DC isolator............500
ground mount .......................500
DIY +inspector +metering cost.500
building consent..................... 0

Any export power is a bonus
My electricity bill is $2000pa. I hope to reduce this by 1000 giving a payback of 4.8 years.
Economically this is marginally acceptable

benmurphy66

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#799990 16-Apr-2013 08:20

pmonro: My approach to economic return is to reduce installation cost and reduce electricity from the utility.
I estimate I can install 2kw, 8X250w panels ground mounted.
solar panels..........................2600
convertor china import............700
cables, AC&DC isolator............500
ground mount .......................500
DIY +inspector +metering cost.500
building consent..................... 0

Any export power is a bonus
My electricity bill is $2000pa. I hope to reduce this by 1000 giving a payback of 4.8 years.
Economically this is marginally acceptable

Based on my research (on kapiti daylight hours). getting a $1000 saving from a 2kw system might be difficult. that would need you to generate ~4000 kwh of energy and you would have to use every one in realtime.

My production model shows a 4.6kw would produce less than 8000kwh.

wellygary

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#800040 16-Apr-2013 09:48

pmonro: My approach to economic return is to reduce installation cost and reduce electricity from the utility.
I estimate I can install 2kw, 8X250w panels ground mounted.
solar panels..........................2600
convertor china import............700
cables, AC&DC isolator............500
ground mount .......................500
DIY +inspector +metering cost.500
building consent..................... 0

Any export power is a bonus
My electricity bill is $2000pa. I hope to reduce this by 1000 giving a payback of 4.8 years.
Economically this is marginally acceptable

You numbers sound very optimistic, What is your annual consumption in Kwh? and what is your load profile?

If you are a regular household you peaks will be in the AM and evening, which for 6 months of the year will likely be in the dark, so you end up selling you solar to the grid at less than you pay ( I think Contact's 17c/unit is about the best deal that is not currently under downward review)

In Auckland they are installing 65KW of panels on the cruise ship terminal and expecting 85Kwh from it annually, scaled to 2KW of panels would yield ~2600 Kwh annually, even at 30c/unit thats only $780 which I guess is probably less than marginal

http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=10875121

pmonro

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#800183 16-Apr-2013 13:28

Thankyou to the two readers who commented on my pricing.
The economy of solar installation is based on two factors.

What it costs to install and What are the returns
I have outlined installation costs which I believe can be achieved or even bettered.

The returns can be obtained from
avoided electricity purchases by reducing the amount of electricity taken from the utility. I pay 21.98c/unit plus GST (25.2) on houshold composite (controlled hot water)
sale of surplus electricity which will always be lower and the difference probably increasing

Now as you noted the houshold usage is highest when solar production is lowest, on a daily basis and also seasonaly so it will be necessary to time switch the load into the best periods. Sure it will be tight.

But if this is not economic it will not be improved (for a householder) by building for sale

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