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# 213858 15-Apr-2017 22:17

This will probably be one of those "crystal ball" questions. But are solar panel prices likely to drop in the future, stay the same, Or go up in price like how everything else seems to increase in price.

 

Partly why I ask is that supposedly new rules have come out to do with solar panels. Which mean that new ones are now more expensive. And the old models are now available at cheap prices. (presumably until the old stock has sold out).

 

Also I have seen people claim that solar panels typically cost around $1 per watt output. They didn't say whether that is US$1, NZ$1, or $1 +GST ect. Yet they normally seem to cost way more than NZ$1 per watt. So what is typical pricing, So I know when to jump at a good offer. Guessing that quality will also vary. But virtually all sellers seem to offer 20+ year warranties. So Im unsure how to judge them beyond the reputation of the seller (Big company Vs someone on Trademe)

 

I haven't even decided what solar system size I want. I could just get a MPPT charge controller. And use it to charge up my existing 12V UPS system, which is 2x 100AH deep cycle batteries. Which provide power to the Router, fibre ONT ect. And are currently charged by a constant voltage charger that runs on offpeak mains power. Guessing would probably need approx 1KW solar array size to get good charging in cloudy weather. Also allowing for a scenario where the mains is dead for ages in a disaster.

 

Or go big - more batteries, Add a big inverter - probably around 5KW, and of course more solar panels. I would consider consider using the solar PV to feed an element in the hot water cylinder, but I have an existing solar hot water system.

 

Guessing the answer would probably be - Do nothing. As solar will never stack up on a purely financial point of view. Due to already having solar hot water, and getting cheap offpeak power with Flick Electric. But having a backup power system would have a big value in a disaster. Yet I could just buy a diesel generator and lots of diesel instead. If the only consideration was backup power. Problem is that generators are noisy, And would be inefficient for me as average current draw for my house is low. But I have things like water pumps and fridge compressors that still have big switch on surges. So load profile better suits a battery / inverter setup.






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  # 1764830 15-Apr-2017 23:28
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Aren't they actually getting more efficient, and dropping in price? So even if they do increase in price, the near models will be able to produce more electricity. However this sort of thing has only been decreasing in price, so I would be surpised if they are increasing in price, unless there is a specific reason. eg a lack of supply at the moment. Or a lack of competition.

 

I thought it was worth getting solar financially, and the best way to store that power in your HWC. Also I was told by one company selling them, that photovoltaic is a better solution for heating water, than the other systems that have historically been used for solar heating. 


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  # 1764845 16-Apr-2017 07:46
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Rate of improvement seems to be decreasing, rate of price drop not sure but I think still decreasing at a reasonable rate. I suspect installation and other things like inverters staying similar prices. What fraction of a solar system is the price of the solar cells?


 
 
 
 


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  # 1764872 16-Apr-2017 09:29
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I have 2x250w panels on my motorhome and they easily keep up with charging the 2x100A/h AGM's I run the whole bus from. For your use I'd say 250w is more than ample as you're running really low wattage appliances.

Best practice is to work out your A/h use over 24hrs and factor 3 days of no/low sun to work out your needs in batteries and charging.

Also to note is that solar panels do best in FULL sunlight, and often outperform their rated specs in our climate. That do very badly when even slightly shaded on one area of the panel, and this affects all the panels in the series. Low sunlight is far better than full sun with even just an aerial shading the panel.

Panel placement and angle is far more important than current weather.

Some excellent discussion on http://www.nzmotorhome.co.nz/NZMotorhomeForum/viewforum.php?f=55 if you search for 'solar efficiency" etc.

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  # 1764994 16-Apr-2017 12:53
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what I've seen over the years is a one way price trend - downwards. As long as there is no reduction in manufacturing capacity, prices should maintain their levels, or continue to drop. With current appetite for carbon free/renewable electricity I cant see a drop in demand either (setting aside arguments about the panel's whole life cycle).

 

 

 

When it comes to panel sizing, you need to do some calculations of load versus panel sizing. More professional calculations will take account of the winter insolation and include your 'confidence' demands. i.e. do you want a 68 / 95 / 99 % chance of maintaining charge in any given (winter) season?

 

You'll need a surprisingly large array for 'guaranteed' power'.

 

Yes, at work we're seeing panels for approx NZD1 per watt but that's panels only. Your system costs will be only partly from the array.


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  # 1765216 17-Apr-2017 00:38
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So a 1kw array would be too much for such a small battery bank - you could likely damage the batteries by charging them too fast each morning.  

 

I would suggest you want at least 1ah at 12v of storage, per watt of solar

 

That would typically run a constant 80 watt load or 2kw per day.

 

 

 

Pricing

 

I havent noticed a drop in price for the last 2 years.

 

Though in saying that, 7 years ago I was paying $1200 for a 120 watt panel, and now I pay $300 for a 200 watt panel.

 

I find its about $1.50 per watt for the efficient type. There is less efficient ones avaliable but they use more space on your roof - better to pay the extra 20% and get the more efficient silicon and save more than 20% of the space on your roof so you can add a few more panels since they are so cheap now.

 

Batteries have not dropped in price over the last 7 years - you are still better to grid tie if you are close to the road / local lines.

 

Lithium is the next big thing with solar batteries.

 

A lithium vs SLA battery of the same storage capacity

 

- Lithium lasts twice as long as SLA

 

- Lithium currently costs more than twice as much as SLA

 

You are best to go with SLA and swap to lithium later when its time to replace your batteries - hopefully the lithium cost will have come down by then.

 

 

 

If you just want to run your router, phone and a couple of appliances in a natural disaster, then 4x 200 watt panels + 600ah @ 12v of storage is probably quite suitable for most to run laptops/charge phones and keep the freezer running. (max 50% occasional overnight discharge or 450 watts for 8 hours)

 

On a more constant basis, that would give you 90 watts for 8 hours a day and the SLA batteries would last 4 years and be at 60% original capacity. (max 60ah daily discharge) 





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  # 1765388 17-Apr-2017 18:28
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raytaylor:

 

 

 

Lithium is the next big thing with solar batteries.

 

 

 

 

 

 

Hi - I'm new here - be gentle.  I'm keen on Solar energy and want to install here in the Waikato (any supplier recommendations welcome!).

 

Personally, I can't wait for the Z-Cell (see zcell.com).  From what I understand it's a zinc-bromide hybrid battery that stores energy by electroplating, and produces energy by breaking down that electroplating.  It's supposed to have a life greater than the current battery technologies.

 

Robert Llewellyn (Kryten from Red Dwarf) recently did an article on his Fully Charged vodcast https://youtu.be/4OHstY_kKUY.

 

 


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  # 1765396 17-Apr-2017 19:05
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In terms of storage, the Tesla power walls seem to be the next step in the evolution. I believe they do now sell them here via a power company.

 
 
 
 


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  # 1766523 18-Apr-2017 09:08
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Local battery retailer list price $3362 for same storage capacity (SLA)

 

Powerwall 2 list price $7800 (nickel manganese cobalt - think of galaxy note 7 fires)

 

More than double the cost

 

They are a hyped up way to repackage batteries  - nothing actually new in the core of the product. And thats where tesla's technology is - the repackaging. To simplify, instead of using big batteries, they use hundereds of little ones. Recharge and discharge them all in parallel and suddenly you can get a very good power output for your car acceleration, or quicker charging.

 

 

 

 





Ray Taylor
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For my general guide to extending your wireless network Click Here




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  # 1766572 18-Apr-2017 09:57
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What new rules have come in that drive up the cost of panels?

 


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  # 1766583 18-Apr-2017 10:07
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I think it's the install cost that's changed as you now require a sparky for anything over (I think?) 200w or something close?

I happily installed (without injury or fire) the 500w on my MHome roof a couple years back, but now the electrical board successfully pushed for this to be regulated (as they miss out on clipping the ticket for lov voltage- less than 50V) and saw the future of solar panels rising

/rant

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  # 1766606 18-Apr-2017 10:41
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If your system is low voltage DC only e.g. mobile home, do you still need a sparky?


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  # 1766608 18-Apr-2017 10:43
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Thanks. Your answer makes sense... not so the new rule.

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  # 1766867 18-Apr-2017 16:36
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Re: Deep cycle batteries. Check specs for yours - some can be charged @ 25 - 35Amps.

 

Re: Solar System ROI - in June 2017 I will finish collecting one year stats for my Solar System generation in Auckland. 3KW Solar Panels with Tesla PowerWall 6.4KWH Battery.

 

In July 2017 I will be able to Analyze total savings + payback for exported electricity and the total number will be a benchmark for calculating ROI period for similar system and usage similar to ours - no gas, no wood, only electricity with us being at the premises 24x7, 365.

 

Link to current stats is here:

 

http://www.hybrids.co.nz/our-solar-system/

 

 




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  # 1767652 20-Apr-2017 01:27

Thanks for the replies everyone. I have taken some current measurements of my battery bank. Approx 2.5A continuous draw. But I still have to switch my second Wifi Ap over to the battery system. And I would like to connect the circulating pump for solar hot water system to the batteries as well. That pump draws approx 100VA, but only runs on approx 10% duty cycle. Annoyingly it doesn't like running from modified sine wave inverters. (still works but buzzes loudly, almost silent on mains). Also intend to run a Raspberry Pi as well.

 

Since Im on a peak/offpeak price plan with Flick Electric. The charger and some other loads are connected to a timer to cut the power during the peak time blocks. 4H off (morning peak), 6H on, 4H off(evening peak), 10H on. So Im only discharging the batteries about 5% per off cycle. Battery voltage was 12.65V at end of 4 hour discharge cycle (measured on load)

 

Interestingly my total peak time power usage is around 35KW/Hr per week. (40 hours peak time per week). So it will most likely work out cheaper for me to offset that by getting a larger battery / inverter system without solar. And time shifting the peak power usage to offpeak times. Peak power costs 11.5c per unit more than offpeak, assuming the wholesale price stays the same. So a possible saving of $200 per year + whatever extra savings due to differences in the wholesale prices. Yet will need around 250 Ah at 48V to meet that load at approx 35% depth of discharge. Guessing that wouldn't even pay for the batteries, even on the basis of - Battery bank cost divided by years of expected lifetime.






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  # 1767677 20-Apr-2017 07:52
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If this is for a long time power outage situation, also get yourself a decent charger that can be run off a generator to get them topped back up as quickly as possible so that you can still get juice into them on a damp cold yuckky winters day/evening when the fragile power network has blown over again. I tried using the one on my generator to charge a 12v battery last time and it was as close to useless as you could get. I think my modified UPS would put more current into a battery than the generators built in 12v output.





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