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Insulation (lots of)

How did you retrofit insulation in? I've looked into doing that but this house has brick veneer and seems hard/expensive to modify.

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Used predominately "blow in" for the northern wall. Western and southern wall have got plenty of shade.

 

The other option is to get a plaster saw and go for it. (Be careful of electrical cables in wall) If you have a blank wall, you typically can have all the gyprock off, insulation in and replastered within a weekend. (Yes. Done this at a friends house. It was a wall that was about 8m in length).

 

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I ponder are air conditioners more or less efficient as heaters than coolers (given they are still a heat pump based upon a compressor).

 

 

ttbomk they are more efficient at cooling than heating, but need to do "more" cooling, if that makes sense

 

fwiw, recommendation for a system is mitsubishi heavy electric (not just mitsubishi, which aren't the same animal at all) - per people i trust as very practical and well educated in this subject, got best rating from 2 out of 2

 

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Reverse-cycle AC is generally more efficient than most (all?) other heating types.

 

I would guess that they are more efficient as heaters than coolers. Like most machines heat is generated as a byproduct and many AC systems bleed off some of the generated cool air for the purpose of cooling the internals of the unit itself.

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Just an update for those interested – as its now been two weeks of variable weather to analyse results.

 

The system has produced 310 kWh, split into:

 

Fed to grid 141.3 kWh (47% of creation) saving $11.30
Replacing Peak usage 47 kWh (15% of creation) saving $26.88
Replacing Shoulder usage 121.7 (39% of creation) saving $28.11

 

For a total saving of $66.30 or about $4.74 a day. For the first two weeks on average we feed 10.1 kWh into the grid per day – which is useful to know when evaluating a battery system and wish to size it and consider its economic appeal!

 

In this time we have consumed 324 kWh from the grid, at a pre-GST cost of 69.85, split into:

 

Off Peak 162 kWh
Peak 53 kWh
Shoulder 94 kWh

 

So it's way too early to say this is solid trending data – but it gives an early indication of how much energy and savings this system may be able to generate. If the trends above were to continue the system would save us about $1,600 per year so have around a 5 year payback. However usage is seasonal and peaks in Summer – so I expect savings may be higher.

 

On its best day solar has created 30.1 kWh (with two cloud breaks during peak production times). The maximum energy (Wh) it can produce so far by time of day is:

 

7am = 0002
8am = 0362
9am = 1,040
10am= 1,959
11am = 2,773
Noon = 3,603
1pm = 4,017
2pm = 4,131
3pm = 3,921
4pm = 3,518
5pm = 2,678
6pm = 1,862
7pm = 0911
8pm = 0209

 

Also I have averaged that our house running a chest freezer, fridge and devices on stand-by consumes a bit less than 900 Wh per hour.

So I hope this data is useful for anyone considering a solar system. I can see for us we can create North of 1.8 kWh from 10am to 6pm – so if we can load balance more of heavy consumption into that period – our savings will increase.

 

I can also measure that our heaviest consumers of power to juggle are:

 

Ducted air conditioning – 3-4 kWh per hour
Electric ovens 3 – 4 kWh per hour (often used in peak hour)
Clothes dryer 3.5 kWh per hour (always run in off peak unless we have loads of solar power to consume)
Dish washer 1-3 kWh per hour (run generally in Off -peak, usually runs for 2 hours – a lot of the time at 1.5 kWh, but then it must heat the water and it jumps consumption up to 3kWh – typically off peak usage)
Clothes washer 1- 2 kWh per hour (jumps highest during spin cycle – off peak usage)
Pool pump 1.1 kWh (off peak usage)

 

Finally by my simplest calculation of our data – if we wanted battery back up the sizing should be around 9.6 kWh if we use an Enphase system – arranged as a 2 strings) * 4 (batteries in each string) * 1.2 kWh (sized battery) array, – so able to shift maximum 550W * 4 = 2.2 kWh for around 3.7 hours at best.

 

Cheers Matt

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Finally by my simplest calculation of our data – if we wanted battery back up the sizing should be around 9.6 kWh if we use an Enphase system – arranged as a 2 strings) * 4 (batteries in each string) * 1.2 kWh (sized battery) array, – so able to shift maximum 550W * 4 = 2.2 kWh for around 3.7 hours at best.

 

Cost?

 

And what are the practical limitations of going completely off-grid?

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Wouldn't try to go off grid!

 

Cost isn't know yet - by my calculations to get a five year real world pay off by simply power shifting you would want each 1.2 kWh pack to cost $1,000 or less to break even. At $800 you should see a 20% ROI. I wouldn't be surprised if these packs retail at $1400 each at launch - which wouldn't make them very appealing.

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Thanks for the info Matt, some really interesting stats to be getting on with :)

 

Have you had a look at any of the sites that help you forecast your generation over a typical year? This might help you with some of your savings forecasts. As you say, a couple of weeks is a very small sample but it does give you some idea.

 

On a side note, it's interesting to see how much is generated on cloudy days. The type of cloud seems to make quite a difference.

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Cloud makes a difference, but with Matt's cells he'll have less impact (Once cell down doesn't bring down a group)

 

I'll be interested in following this.

 

Matt.. Please keep us updated. I'd love to see how this plays out over a year. (Even if you post it in Tech Talk. That'll keep it front page for most of the year.. :P )

 

I love energy efficiency and the like.

 

Out of curiousity Matt. Do you have solar hot-water? I've noted that his is a huge thing in our energy efficiency. When we have to use the booster, it's a massive drain on our power.

 

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No solar hot water - although I had this growing up as a kid, and so long as you have a mains boost for bad weather and a reasonable daily consumption rate its okay and saves you money. But in my situation with a young family, lots of washing and showering that we felt no chance could solar keep up - when we planned for hot water we simply removed a gravity fed, off-peak heated, huge tank of scalding hot water for an instantaneous, high flow all you could use system. Back then gas and electricity were cheap too!

 

I have looked at PV watts site for a forecast for my system http://pvwatts.nrel.gov/pvwatts.php it gives me a model that for half of March is almost spot on:

 

Solar Model.....PVWatts kWh
January.............767
February............620
March................653
April..................539
May..................438
June.................378
July..................455
August.............583
September.......643
October............738
November........701
December........735

Total..............7,250 kWh

So the big thing is if I feed over 40% of this to the grid rather than self consume it is decreasing my potential savings by my figures by about $1,400 a year, or say $7K over 5 years. To minimise this I would need say 8 * 1.2 kWh in batteries. and $7,000 / 8 = $875. Now these batteries may have a ten year life, but on such a long tail bet does one really want to buy (versus lease or rent) that much storage. So if the company prices them with a 8 year break even - they would launch at say $1,400. For a 10 year break even $1,750. So the battery providers may hope to convince zealots to jump on board with an Australian launch price of say $1,400. If they did that as an out right purchase instead of an annual lease - then smart money would say they have over-priced the bulk residential market.

 

Happy to post figures cause anyone considering it should go in with better information and analysis than I had - if I do this job right!

Edited by g__day

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Two rather interesting solar generation innovations were shown on the weekend on the ABC. The first was an Australian University innovation that doubled power conversion to above the magic 40% target for the first time, the second was a refrigerated concentrated that produced an amazing amount of power.

 

The first innovation came simply from understanding that different solar cell technologies work better or worse with different frequencies of visible light. Gallium Arsenide is great at blue and higher energy frequencies of light whilst the normal poly crystal silicon cells work far better below the blue frequency range. So scientists took a way front of light and ran it thru a simply beam splitter (called a cold mirror) set the desired spectrum switching point. So deep red to almost blue wave lengths of light go to a normal silicon based cell and blue and above frequencies go to a normal gallium arsenide cell. When you had the output of these two cells it’s into the 40% plus range of power converted. So miniaturise this design and you have a real winner – double the power from the same roof top area.

 

The second innovation came from noting gallium arsenide is very efficient with high energy beams of solar radiation so long as the cell keeps below 65 degrees Celsius. So one bright spark built a massive refrigerated heat sink and integrated it to a very small (15cm square) gallium arsenide cell, put this gear up a 10 metre high post and pointed a small, tracking solar array of mirrors (about 20 of 15 m square size) to focus and shine sunlight at this cell. Wow did it produce so he scaled it up to a 1 metre square refrigerated collector and it produced 250 kilo Watt hours of energy in a day. This set up they say scales linearly and has been in production as a test facility for months now. Scaled to 2 * 2 metres square and a solar mirror array a bit large than a large back yard worth of land and it would produce a mega watt hour of power – enough to supply say 50 houses for a day.

 

Now the two teams are collaborating on their designs as they can both use the others solutions. The future seems much brighter for localised, mini grid production of energy! Now it will be interesting to see if storage technologies can progress significantly in the next few years!

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...So one bright spark built a massive refrigerated heat sink and integrated it to a very small (15cm square) gallium arsenide cell, put this gear up a 10 metre high post and pointed a small, tracking solar array of mirrors (about 20 of 15 m square size) to focus and shine sunlight at this cell. Wow did it produce...

That sounds very cool (groan), but does it still make a profit once you account for running the refrigeration system?

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Just to add some more stats to the mix.

 

Our solar which was installed at the end of October but went 'live' in Dec.

 

For the past qtr we generated 2.9MWh of which 43% was exported. The average generation per day was 31.5kWh with a peak of 48.6kWh. The peak instantaneous was 6.48kW which was higher than expected.

 

As for other cost saving measures, we will be changing the high use halogen downlights for LEDs in the coming months, and I'm researching the best hot water system to replace our 15yo gas storage unit. Given that gas prices are also increasing quickly, this will be some sort of electric storage system.

 

Another aspect I investigated was putting the stand-alone freezer on a timer. It doesn't get opened all that much so the logic was if I have it only sucking power during the day while on solar, it would still remain cold overnight. I tested this while it was empty but the temp went up dramatically. This showed that it's insulation sucked donkey balls and that having a frozen mass of food inside would probably help keep the temp down :)

 

I haven't tried it again with food in it because I don't want it to go off, but I think if you had a better quality unit(not the second hand $50 homemaker brand) you might get better results.

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Another aspect I investigated was putting the stand-alone freezer on a timer. It doesn't get opened all that much so the logic was if I have it only sucking power during the day while on solar, it would still remain cold overnight. I tested this while it was empty but the temp went up dramatically. This showed that it's insulation sucked donkey balls and that having a frozen mass of food inside would probably help keep the temp down :)

 

I haven't tried it again with food in it because I don't want it to go off, but I think if you had a better quality unit(not the second hand $50 homemaker brand) you might get better results.

 

Sounds risky, and it won't take much spoiled food to offset the cost of the power - and stand alone freezers are usually about long term storage, so it's temp needs to be sub -18c

The freezer will have a thermostat, so if as you say, it's not opened very often, and it's located in a cool place at night, then the thermostat should be only running the compressor the minimum needed to keep it below the set safe temperature.

 

Food storage is an area where convenience is more suitable than lowest cost, but buying a better appliance will perform better - whether it offsets the cost of purchasing the replacement is a separate factor - but if you may be able to offset that against the coolness of keeping the old one in the back yard to use as a nuclear blast shelter :P

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I went through the process out of interest more than anything else - it did point out how poorly insulated cheap freezers are. When I tested it I had a high/low thermometer in the freezer with an external display. If I remember correctly the temp went up by 15C!

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I've had a 5KW system (6KW of panels and a 5KW inverter) for nearly 2 years now and it's great. Spent about $10K and it generates around 30-33KwH per day in summer. My bill went down from around $1300, with ducted air and a pool running 8 hours a day) to $800 after solar. That's with me running the ducted more than I did the previous summer.. Winter is around $300 instead of $700.

 

I'm scared about my summer bill this year though. I've pretty much left the ducted on 24/7 when we're home.

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I am curious - why more panels than the inverter should handle - is it panel loose expectations or is the inverter capable of handling 6kW but your power line to the grid is only single phase so you can't go above 5 kW without spending the $1,200 to convert to three phase?

 

Yeah our next Summer will be interesting - the Solar should handle most of the Air conditioning, and with more people home we should be consuming more of what we produce - I hate seeing power go into the Grid at peak time when they charge us so much but pay us so little.

 

Really home power shifting battery technology is economical soon! It leave me irked that the power companies can meter and bill us for time zone priced capacity, but don't offer the same courtesy when they take power for us. I would be ecstatic at a power company that said we will sell to you at time of day rates and buy from you at say those same rates less a 5% discount. I would also like them to say hey half the time you supplied peak power to us so we will half your grid connection service fee as that's equitable!

 

Wonder if that inflection point might happen soon - if say 30% of house had solar would the rebate structure be almost totally equitable. So If I shift say 200 KwH in a month to the grid in peak hour and my next door neighbor consumes it - AGL pays me $16 and bills my neighbor $112; which seems a bit unfair pricing to me. Their cost to distribute my excess energy a small distance is tiny and they are selling my excess energy at a total premium. My producing power for them delays their need to upgrade peak production capacity.

 

I honestly ponder what will happen to Energy utilities when solar is the norm and the grid has most of the houses and businesses creating most of what they need during peak usage periods. I read Hawaii is planning to be 100% solar by 2040 - a big change I think will be coming.

 

Peak Solar efficiency in the lab is now 47% - so almost three times more efficient then commercial cells I bought last month. If my roof could produce 15 kWh and batteries / energy storage were affordable I pretty much very economically could go off grid for all power. Bet the power utilities weren't counting on that happening so fast.

 

Solar efficiency has grown from a few % to almost 50% in 35 years! http://www.treehugger.com/slideshows/energy-efficiency/all-solar-efficiency-breakthroughs-single-chart/

 

During that period Solar has become 100 time more affordable - with the biggest fall in price per watt produced happening in the last three years http://media.treehugger.com/assets/images/2013/12/price-of-solar-power-graph-11.jpg.662x0_q100_crop-scale.jpg

Edited by g__day

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Speaking of phases(!) that was one issue I hadn't really thought about until we got close to installation. This was a little more complex because we have 3 phase power.

 

I went through working out what devices were on what phase and tried to match demand with production since the main benefit is for us to consume our own power, not feed it into the grid. After doing the work and putting in the application with the power company we were knocked back - it was either evenly spread production across the three phases or nothing.

 

I can see it makes sense from their perspective, but I was a little annoyed at the time...

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That was something I didn't know about 3 phase power. But recent development I have heard is the next generation of the Envoy-s gateway can limit the power sent to the grid to 5 kW, so one could install a 10 kW system - use as much energy as one can, put energy into storage if you have it and it needs it and feed the grid - but just up to 5 kW - meaning you don't need 3 phase power.

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Small rant here, background is:

 

  1. I have been with AGL for electricity for 20+ years now
  2. I called them 6 times over the past six weeks requesting a Solar quote from them - and they never once got back to me despite promising to within 2 business days when the calls diverted elsewhere
  3. Today a solar recommendation arrives for me unsolicited from them.

I have some issue with their quote that I rang to discuss with them:

  1. It's very, very late
  2. It recommends a solution that is sized at half of what even the simplest of maths would confirm is the appropriate size
  3. It doesn't state the recommendations are indicative only - not its wording are Our Smart Solar recommendations by our Experts
  4. It recommends a solution technology that won't suit my roof shape (its not micro inverter based)
  5. It recommends a solution that it doesn't clarify is ready for energy storage when it becomes available from AGL later this year

So pretty much a fail on all accounts and a shameful example of having deep knowledge about me and failing totally to leverage their data. The icing on the cake was telling them all of the above and asking them to feed that back to their senior management in Marketing, Sales and Customer Service. Then I asked them about storage solutions they say AGL will only offer a storage solution if you buy their Solar solution (even though really the two technologies are not heavily interdependent as far as I understand.

 

Just a shame when your own service provider demonstrates no understanding of your requirements and totally fails to offer you what you implore them to do on a times basis!

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A good friend is going off the grid in the near future, here is a video of his solar pump setup.

 

 

 

No prizes for guessing :)

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Bump? lol.. I should drop by here more often..

 

Anyhoo, My old man got solar.. back with the 60c feedin rate.. makes money every day. not much, but enough. his main problem is trying to get his money back from the utility companys.
Another mate put the panels on his house, then brought a plug in hybrid.. so "fueling" the car costs him nothing during the day. And his next door neighbour put 20KWh on the roof of his busines to slash his energy costs.

Its looking to be a dang good investment.. a one off payment for almost free power. :D

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Bump? lol.. I should drop by here more often..

 

Did...did you just intentionally select Comic Sans? Like, on purpose?

 

You monster!

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Bump? lol.. I should drop by here more often..

 

Did...did you just intentionally select Comic Sans? Like, on purpose?

 

You monster!

 

MUA HA HA HA HA HA!

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