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Question about solar power

eclectricdave

Member
Feb 24, 2016
336
115
Malbourne Australia
Ive been off-grid for about 24 years now. We have around 5kWs of PV (solar). Im an electrical engineer by background. If Id had my time again Id have got a large grid feed system & a Tesla type power system & small efficient generator. Owning a Tesla is a challenge for our system and I rely on SCs and a local If Homer Chardemo. If Homer wishes I could visit on my next trip to Syd to check his house for energy usage.
 

360C

Member
Aug 5, 2015
87
33
Melbourne Australia
I've been going back over the bills and the usage drops back to 36kWh/day in the Spring quarter, which is when we run the a/c the least. So to me that indicates the impact of the a/c on our consumption. I have a feeling, based on comments by my neighbours who have replaced their lights with LEDs, that the lighting makes up another chunk of the cost. I will investigate replacing the lights; from memory it was around a $10K spend so, much like the solar, you get it back over time.

Big houses can use a lot of energy, especially with A/C running. The A/C can use multiples of your homes average daily use without the A/C.
I am in a similar situation and we used an average of 50kw a day before I started changing to more energy efficient lights and appliances. After I changed something close to 100 internal lights and about 40 external lights, the average daily usage dropped to about 35kw. When we use the A/C in summer to cool a 40sq two story house the energy used is 100kw plus a day. Now I run a Tesla it adds about 15kw a day of usage so we are back up to an average of 50kw a day. In late December I am getting a Model X in addition to our Model S and we will be all EV for daily drivers and I expect our average daily usage will be around 65-70kw a day as I have a long daily commute to work.
This month I am upgrading the home solar/battery system to 20kw and battery storage of 48kw which I estimate will be enough to run the house and 2 cars totally for about 6-7 months of the year in Melbourne.
As noted in a previous post, the economics of doing this won't stack up for most people.
 
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eclectricdave

Member
Feb 24, 2016
336
115
Malbourne Australia
360C . I do have access to main electrcity though at our farm 100ks from Melb. I have a 2kW PV array charging a 50kWhr battery. I can charge o'night at 3.6 kWs offpk and at day time ex bat/PV for another 6-8 hrs at 2.4kWs and this is usually enough to charge the Tes. I will expand the PV & bats such that less power will be taken from the grid. The PV predates the Tes and was installed to power a heat pump HWS.
 

Homer

Member
Jan 13, 2016
245
56
Sydney, Australia
Big houses can use a lot of energy, especially with A/C running. The A/C can use multiples of your homes average daily use without the A/C.

Yes I really think this is our issue based on the seasonal variation I see in the bills. We have separate a/c units for the living floors and the bedroom floors and do try to switch them on and off according to where we are but in the middle of summer and in the depths of winter, they are cranking. Our washer and dryer are less than two years old but we've got a large refrigerator and a bar fridge that would be 10 years old and not very energy efficient. And we need a new fridge so I'll make energy efficiency one of the requirements. And I'll tackle the lights...
 

360C

Member
Aug 5, 2015
87
33
Melbourne Australia
Typical Day in August.jpg
Yes I really think this is our issue based on the seasonal variation I see in the bills. We have separate a/c units for the living floors and the bedroom floors and do try to switch them on and off according to where we are but in the middle of summer and in the depths of winter, they are cranking. Our washer and dryer are less than two years old but we've got a large refrigerator and a bar fridge that would be 10 years old and not very energy efficient. And we need a new fridge so I'll make energy efficiency one of the requirements. And I'll tackle the lights...

The A/C makes a monumental difference which is easily illustrated with a couple of images from the software in my solar system........

The first readout is from a typical day in August. Energy Consumption is the top graph and Energy Generation is the bottom graph.

RED = Grid Power
GREEN = Solar Generated Energy
MUSTARD = Stored energy being discharged from battery bank
ORANGE = Solar Generated Energy being used to charge battery bank
YELLOW = Solar Generated Energy being fed back into the grid

Base energy requirement of the house is about 1kw/h (runs fridges and appliances permanently on).
Night time energy usage typically between 1-2 kw/h without heating cooling running.

BIG PEAK 10am-12.30pm is the Tesla charging on SINGLE PHASE. Note it uses all the solar generated energy (green) and the available battery charge at the time (mustard) and then the balance required comes from the grid (red).

ENERGY USAGE FOR THE DAY = 51.38 kw
 
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360C

Member
Aug 5, 2015
87
33
Melbourne Australia
Now have a look what happens when the Air-Conditioning is cranking full tilt on a 42 Degree day in January............

We have reverse cycle A/C with one unit for each floor of the house.
The A/C went on at 10am and then cycled for the rest of the day. Note the total daily consumption jumped to a massive 159.46 kw.





42 Degree Day in January.jpg
 
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moemoke

Member
Oct 10, 2014
179
48
Moe, Victoria, Australia
Nice info 360C, is that the latest version of Sunny Portal? I used it a while ago for our place but it never gave me
that sort of info, maybe I need to update!
Gee I'm glad we don't have air-con, certainly chews through the power, we average about 8kw/h a day in
summer and 11kw/h in winter, our 2kw solar system in summer used to pay for our winter usage.
 

360C

Member
Aug 5, 2015
87
33
Melbourne Australia
360C . I do have access to main electrcity though at our farm 100ks from Melb. I have a 2kW PV array charging a 50kWhr battery. I can charge o'night at 3.6 kWs offpk and at day time ex bat/PV for another 6-8 hrs at 2.4kWs and this is usually enough to charge the Tes. I will expand the PV & bats such that less power will be taken from the grid. The PV predates the Tes and was installed to power a heat pump HWS.

That is a pretty serious battery at 50Kw/h and I think it is the key to being able to charge the Tesla from only a 2 kw PV array.


Nice info 360C, is that the latest version of Sunny Portal? I used it a while ago for our place but it never gave me
that sort of info, maybe I need to update!
Gee I'm glad we don't have air-con, certainly chews through the power, we average about 8kw/h a day in
summer and 11kw/h in winter, our 2kw solar system in summer used to pay for our winter usage.


I can't say that I know which version of the Sunny Portal software this is. It is what we have had since the system was installed about 18mths ago. I know that there is an even more advanced version available by subscription; but I think that is aimed at installers rather than end users.
I actively use data from 3 sources to analyse our energy usage. The Sunny Portal software, the Tesla App and the Power Shop App provide all the detail that I need.
 

Homer

Member
Jan 13, 2016
245
56
Sydney, Australia
Are all solar panels the same or are there variations in the performance/technology? Is the industry expecting any significant improvements to the design or performance of panels in the next few years?
 

meloccom

Moderator Aus/NZ
Feb 11, 2008
2,327
1,220
Sydney Australia
Are all solar panels the same or are there variations in the performance/technology? Is the industry expecting any significant improvements to the design or performance of panels in the next few years?
From what I understand solar panels are like batteries, where there are regular reports of "breakthrough" technology improvements but the product available to the general public improves only incrementally. Having just installed Solar with a PowerWall I had a choice of panels ranging from 255W per panel and a 16.5% efficiency up to 300W panel rated at 18.3% efficiency. I went with the 300W LG Neon 2 black panels but most of the reason was visual as the panels are visible front and centre as you drive in my driveway and sit on a grey house with a grey roof and black window frames and trim. That and they have slightly longer product warranty, higher load ratings and are manufactured by a company I had heard of before I went Solar shopping.
2016-10-09 09.57.27.jpg
 

baillies

Member
Apr 19, 2015
477
256
Sydney, Australia
Tesla should announce the power wall V2 soon, maybe end of this month(or maybe Tesla time). Solar panels are expected to come down by 10 to 30% in the next few years and improve to over 300W panels being the norm. Note that the install cost is not just the panels so maybe not a large reduction but if V2 power wall is cheaper this could make a difference. Not sure if V2 will include Tesla inverter or if this will happen post integration with Solar City.
 

miimura

Well-Known Member
Aug 21, 2013
6,161
5,754
Los Altos, CA
Are all solar panels the same or are there variations in the performance/technology? Is the industry expecting any significant improvements to the design or performance of panels in the next few years?
There are certainly differences between solar panels. However, the ratings are usually reliable and the main difference is the output per square meter of panel area. If you have limited roof area then you may need to use more expensive panels to reach the system size you want. If you have lots of available area, you can spend less $/Watt. I don't expect any step changes in solar technology or price, just gradual improvements to both as it has been over the years.
 

lonewolf313

Member
Jun 18, 2014
240
79
Sydney Australia
When Tesla first announced the Gigafactory in Nevada, they showed pictures of it completed with a solar roof

Gigafactory 1 2014.JPG


Now after a number of years of construction, it still does not have a solar roof on it

Gigafactory 1 2018.JPG


Does anyone know why as that many solar panels would surely reduce their electricity costs dramatically?
 

miimura

Well-Known Member
Aug 21, 2013
6,161
5,754
Los Altos, CA
They started installing solar panels on the roof. Don't you see them down at the far end? I suspect that they're not in a hurry. I would expect that they will soak up whatever production at Gigafactory 2 is not sold to other customers, in order to fulfill the minimum production promised to Panasonic for solar cells. Solar roof tiles certainly haven't ramped up as expected.
 

360C

Member
Aug 5, 2015
87
33
Melbourne Australia
An update on my earlier posts about running Tesla's on our home solar/battery storage system.

This is a full year of running 2 Tesla's and the house on our upgraded 20kw solar/48kw battery storage system. My conclusion is each Tesla is adding the equivalent energy usage of one average house. So even with what is a very large system for residential it won't take a house and 2 Tesla's completely "off-grid". The system easily takes the 40sq house by itself "off grid". I'll be adding to the battery storage capacity, probably to 96kw in the near future when I upgrade my work system and transfer its batteries to my home system. I suspect the house and Tesla's will be pretty much fully off grid bar perhaps a month or so in the depths of winter in Melbourne.

I also made what turned out to be a major change in the effieciency of the house in February 2018 - getting all of the north facing windows of the house tinted. Unfortunately we don't have double glazed windows and the tinting was a cheap efficiency alternative. Much to my surprise it would seem that we gained about 8% in self-sufficiency so far this year. We have yet to turn the A/C in the house on this year and I expect we will use it a lot less over summer. I'll be interested to see what the gain in self sufficiency is over the full year.


Sunny Portal 2018-10-17 at 8.47.49 PM.jpg
 

paulp

Active Member
Jul 23, 2015
2,675
1,215
Adelaide, Australia
Before you add another battery you need to ensure you have sufficient surplus to charge it. You may find that it wont be used for several months.
Also shade your north, east, and west windows. Will perform way better than just tinting. Unless your glass is toughened, the film used is very low grade, so removing the heat load will be a quantum leap. Exterior venetians are extremely effective.
 

360C

Member
Aug 5, 2015
87
33
Melbourne Australia
Here is some more data that may interest those looking at solar/battery storage with EV's.

Initially we had a 10kw system with 24kw of storage. Our first Tesla arrived early August 2015.

We upgraded the system to 20kw solar and 48 kw battery storage on 25/10/16

Our 2nd Tesla arrived late March 2017 making us completely EV for daily driver cars.

I've learned to choose the timing of charging each of the Tesla's to optimise the usage of solar generated energy by monitoring the Sunny Portal, the Tesla app and the Powershop apps. That is a bit tricky; but makes quite a big difference to the amount of grid energy used over a year.

Annual Comparison 2018-10-17 at 9.12.38 PM.jpg
 

360C

Member
Aug 5, 2015
87
33
Melbourne Australia
Before you add another battery you need to ensure you have sufficient surplus to charge it. You may find that it wont be used for several months.
Also shade your north, east, and west windows. Will perform way better than just tinting. Unless your glass is toughened, the film used is very low grade, so removing the heat load will be a quantum leap. Exterior venetians are extremely effective.

You're right; but I've got the batteries anyway. I'm just transferring them from my work system to my home system. I am going to upgrade the 65kw work system with about 200kw of lithium batteries from salvage Tesla vehicles as a fun project.
I would expect that there will be a couple of months in winter where the extra capacity won't be used at home. However over summer it will really pay dividends as we currently send too much back to the grid.

Correct again on the shading of the windows. In this case aesthetics win out over energy efficiency as it would not work with the design of our house. I really was surprised at the gain we got from the tinting though, I expected a couple of % at best.
 

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