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This week I went solar :)

How cool new technology is... Micro-inverters are cool!

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#21 g__day

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Posted 06 March 2015 - 11:55 PM

We insulated floors and roofs with fiberglass, installed awnings on all Westerly facing windows, use LED (dimmable) lights everywhere and probably could have gone for thicker curtains.  Swapped out room heaters for air conditioning late at night, user timed electric blankets that each person can set to their own preferences - heat the bed not the room! Gas we mainly use for heating (ducted downstairs, one sizable unit upstairs), instantaneous for showers.  Door frames we insulated with foam sticky tape - costs about $10 per door - really helped heat loss prevention in Winter.  Wish we had of been rich enough to get double glazed windows. 

 

I was amazed measuring how much energy a large gas stove and the ducted air conditioning use.  No matter what else we do they (of and a large dryer that is only used at night) appear to influence the lions share of our energy consumption. Today was almost a perfect sunny day - generated 30.2 kWh - of which probably 12 kWh fed the grid.  From about 10:30am to 3:30pm today the system produced at least 3.8 kWh - which is excellent!  So it had me trying to use everything to consume when we had excess from jobs I normally run at night in off peak - dish washers, pool pump cleaner, washing machine etc - just to see how much energy load balancing is possible if one person with the will to do it is home.  With a energy storage solution that need for human management could be significantly decreased.  Till almost sunset I could use everything I normally set for day time use and still be feeding the grid.  Only the large ducted air conditioning tips the apple cart - it can draw from 3.2 to 4.5 plus kWh alone.  Today I didn't put it on until 3.30pm cause the solar tiles are helping keeping the house cooler by shading the roof tiles - about 34 square meters of roof tiles are shaded.  Once I needed to cook with the oven I switched the a/c off and keep it close to zero grid input until kids came home.  So it is doable but I wouldn't wish to turn into the Grinch with energy - it would be easy to go too far.  Instead I want the family to be energy conscious and make good use of the free power we get each day!

 

Must say I find it really interested reading what others have done and raising awareness of how strong the legs of solar are nowadays.  It will be interesting to see in Winter if its economical to use slightly less gas and slightly more electricity.  I ponder are air conditioners more or less efficient as heaters than coolers (given they are still a heat pump based upon a compressor).


Edited by g__day, 07 March 2015 - 12:02 AM.

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#22 Mac Dude

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Posted 07 March 2015 - 08:10 AM

I think the impact of energy savings measures will be greater once small grid connected storage becomes easily available. As was pointed out earlier, once you can store even a small amount for night time use it will have a dramatic impact on your power bill.

I'll be looking at changing from the gas hot water we currently to one of the more efficient electric systems which can heat and store during the day. Problem is the old one won't die!

We haven't changed our lights yet, that's next on the list :)
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#23 AccessDenied

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Posted 07 March 2015 - 09:53 AM

Yeah..  It definitely is gaining some traction.

 

I'm looking at other methods of improving efficiency around the place.  Looking at making the house a 'solar air heater'.

 

We've got a large section of westerly facing roof, so that'd be ideal.

 

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#24 .:Cyb3rGlitch:.

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Posted 07 March 2015 - 10:00 AM

I think the impact of energy savings measures will be greater once small grid connected storage becomes easily available. As was pointed out earlier, once you can store even a small amount for night time use it will have a dramatic impact on your power bill.

I'll be looking at changing from the gas hot water we currently to one of the more efficient electric systems which can heat and store during the day. Problem is the old one won't die!

We haven't changed our lights yet, that's next on the list :)


I believe Tesla are working on a standalone Model S battery for residential solar power storage.

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#25 AccessDenied

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Posted 07 March 2015 - 10:01 AM

Correct:

http://reneweconomy....ge-market-92001

 

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#26 TheFrunj

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Posted 07 March 2015 - 10:12 AM

Changes include:

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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#27 AccessDenied

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Posted 07 March 2015 - 10:18 AM

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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#28 scruffy1

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Posted 07 March 2015 - 10:38 AM

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
 


ummmmmmmmmmm............


#29 Rybags

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Posted 07 March 2015 - 12:23 PM

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.



#30 g__day

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Posted 15 March 2015 - 08:50 AM

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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#31 Director

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Posted 15 March 2015 - 10:53 AM

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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#32 g__day

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Posted 15 March 2015 - 02:45 PM

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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Posted 15 March 2015 - 03:08 PM

Cheers.

 

I still don;t own a roof but like to collate the information for the day comes. :)


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#34 Mac Dude

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Posted 15 March 2015 - 06:05 PM

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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#35 AccessDenied

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Posted 15 March 2015 - 09:35 PM

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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#36 g__day

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Posted 16 March 2015 - 12:14 AM

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, 16 March 2015 - 12:17 AM.

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#37 g__day

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Posted 17 March 2015 - 08:51 AM

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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#38 Cybes

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Posted 17 March 2015 - 10:51 PM

...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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#39 Mac Dude

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Posted 18 March 2015 - 07:42 AM

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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#40 stadl

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Posted 18 March 2015 - 08:13 AM

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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