Tag: Solar System
Solar Savings with Ultra Low Overnight Rate
In a previous post, I talked about switching our electricity rates from a tiered rate schedule to an Ultra Low Overnight (ULO) rate schedule. The latter rate schedule effectively means we pay a third less when using electricity from 11pm to 7am.
I have received a full month’s invoice while on the ULO rate. Below is a comparison with the previous year.
The above is a clear depiction of the resulting differences. We are able to get way more credits using the ULO rates. I call this a huge success, especially since we had a few hot days with the air conditioning running. Let us see how the remaining months will add to our credits.
Panel Snow Coverage
Today is January 13, 2023. We had an icy snow storm last night that lasted until this morning, and I was curious what the roof condition was like. Just how much of the panels were covered in snow?
Our peak energy production was at around 11am when we generated a little over 800Wh, which is inlined with what we kind of get on a cloudy, misty, winter day. In contrast, the best we got so far was on January 7th at 1pm. We generated 5,494Wh. That was a sunny day with no snow coverage on the panels.
I was kind of impressed that we got that much with so much of the panels covered. Watch the above video to see just how much of the panels are covered today. Our total production for today is only about 3,400Wh.
Below are the stats per panel.
As you can see above, every panel contributed even the covered ones! There will be two sunny days over the weekend, so we will see!
Update: 2023-01-14
I did another roof survey with my drone, seeing that today it was a sunny sky day.
We have generated over 10,000 Wh of energy today about 3 times more than yesterday. The survey was conducted when it was still -6 ºC outside, so way below freezing.
Length of Days Throughout the Year
Winter has arrived, and our solar production is seeing a sizeable drop in production. Although the month of November is still incomplete, here is our current solar production history so far:
We were operating at 50% utilization when on of our SolarEdge inverters went down in June, and as pointed out earlier, November is only about 75% completed as of the time of the writing of this post.
Even with the above discrepancies in mind, we can see a gradual reduction in generation from the summer months. From a peak of over 2500 kWh in July to just around 1230 kWh in the month of October. That is half of our peak from July. Based on the November trend, we will have even less.
These reductions got me curious to the length of day variation through the year, and I found this handy chart:
The above chart is customized by our home location of course. From trough to peak, there is a difference of about a 6.5 hours! I must say, I knew there is a difference between the longest and shortest days, but seeing number was a bit of a shock. These short days are made worst by lowest sun elevation on our Southern horizon during the winter months.
It will be interesting to see how much power we end up generating during December which will be our lowest generating month, per the above chart.
Solar with Snow
The past few days we have met our first signs of Canadian winter. Although winter has not officially arrived, we have received at least a couple of snow dustings that resulted in enough accumulation on the roof to cover the solar panels.
I wanted to record our observation with this “new” experience in terms of the impact to power generation. Below is a chart on solar power generation in the past few days with different weather conditions during the shorter days of our Canadian autumn.
Our highest recorded power per day is around ~110 kWh during a nice sunny, long, summer day in June. We are now facing shorter days with the panels active from around 8am to a little after 3pm, as the chart below shows.
Below you will see what my roof looks like today on November the 18th. Click the video below to see the entire roof.
You can see that we have some panels that are fully exposed, and some that are partially covered. The solar optimizers are optimizing away during these times, and when the sun comes out, we can still sometimes generate above 3500W of instantaneous solar power.
During these dark and short days, we are now definitely eating into our stored electrical credits from Alectra Utilities.
XWPro Configurations
This is going to be a fairly technical post on the topic of my Conext XWPro battery inverter configurations. I am writing this post primarily to document my experience and my current rationale, and for my future, forgetful self.
Previously I had my Grid Support SOC (State of Charge) and the Recharge SOC set to 40%. With these settings, the battery will be used (anytime during the day and night) until it discharged to 40%, which will initiate a charge cycle that will charge the battery back to 100%. Under normal circumstances, the battery will typically discharge during a very cloudy day, but mostly in the evenings and at night.
I had the above settings because I stupidly thought I should stay off the grid as much as possible. The intent is to try to charge the batteries in the evening during off peak hours, and not to use the grid at all during on peak hours. These settings certainly accomplish this, but at the expense of shortening battery life. Another big downside with this approach is that charging the battery through the Conext XWPro inverters only achieves around 83% efficiency. This observation is based on my real-time data observations from the actual inverters.
Yesterday I noticed that my batteries are reporting a State of Health (SOH) drop to 99% instead of 100%. This was a bit alarming given only 6 months of uses. I also realized from the Alectra invoices that Time of Use (ToU) is not a factor in Alectra’s billing calculations. All of this resulted in a shift in my thinking. We will now use the grid as our primary battery, and preserve our Lithium Ion as our backup batteries only. Time shifting of loads will no longer be my primary concern since it is no longer worth it with zero benefits.
To do this, I have set the Grid Support SOC to 90% and the Recharge SOC set to 85%. This way immediately after a charge cycle, the battery will be used a little bit to draw down from 100% to 90%. This has two benefits in my opinion. The first is to get some charge flow through the batteries, so it is not only sitting there. The second is that it leaves a 10% SOC gap. If we have a power failure during a sunny day, there is space for the excess solar production to go without tripping the solar inverters.
The 5% gap between Grid Support and Recharge is currently a guess. My thinking is that over time the charge on the Lithium batteries will leak and it will trigger a recharge cycle. Of course I did not want to set the Recharge the same as the Grid Support, because this will cause a constant recharge loop which defeats the purpose of preserving battery life. I do not know how long it will take to naturally draw down from 90% to 85%. This is why it is still a guess at this point. If there is no leakage, which is great news because it shows how good the batteries are, then I will have to trigger a recharge cycle at least once a month just to keep the charge flow within the battery’s chemistry.
For now I will live with the new settings and see how often the battery cycles. If it only cycles once every one or two months, then that is perfect. If it does not cycle through more than three months, then I may have to add the monthly charging cycle logic into my custom controller.
Electricity Bills & Natural Gas Rates
Since our solar installation, and our live commissioning of our net metering with Alectra Utilities, our last payment to Alectra was in May, 2022. Since then, we have not paid a dime to Alectra, but instead we are sitting on a nice credit as the attached snapshot of our bill showed:
As the above bill indicates, we created 372 kWh during the 30 days of this last bill that we received. I was also surprised by the fact that during the summer months, we were still able to generate excess while running our AC without compromising our comfort requirements. The extended summer days and the higher angle of sun’s elevation were very conducive to solar production.
I also noticed our natural gas prices increased by 110% from the same time last year. Below is directly from the Ontario Energy Board (OEB):
Our goal now is to try to switch our heating source from natural gas to electric, so that we can use our excess electricity for this winter’s heating needs. This makes total sense, since our electricity is almost free, while natural gas is not!
There are reports out there saying the rate increase is significantly less. This is because they are comparing against the July, 2022 rates and not the October, 2021 rates, so read carefully.
I went on Amazon and purchased three of these electric based heaters.
At time of purchase, they were $219 CAD each. We tried the cheaper ones, but their fans were simply too loud. These ones are nice and quiet with a very user friendly interface.
The master plan is to set the house thermostat to 18ºC, so that it acts as a backup heating source. While these electric panels will try to heat the house during most of the winter days. We will see how this plan goes. I would consider this to be a win if we can reduce our natural gas consumption this winter by more than 50%, which will effectively normalize the rate increase. In the end, these electric heaters may not be enough. Time will tell.
I also investigated the possibility of installing a centralized heat pump, but current technology is limited to -20ºC outside temperature. I decided to table this for now until the technology matures a bit more. I want a solution that can transfer heat from -30ºC outside to indoors.
Our next plan is to research our water heating needs and to see if there are any electric based tankless solutions out there.
Wish us luck and I’ll keep everyone updated!
Update: November 14, 2022
Previously I got the rates from the Enbridge web site. Below is an actual excerpt from my Enbridge bills. However you compare, the increase is significant.
Update: November 26, 2022
Found this CTV article.
Frequency Shift Power Control
If you follow my posts in the Solar category, I mentioned Frequency Shift Power Control. What is this? I will try to answer it in this post and explain why this is important in the context of full house backup and grid connectivity is lost during a power outage.
There are two types of inverters in my house. The Schneider inverters are the hybrid inverters that charge and discharge the battery and manage the battery power in conjunction with grid power. During normal operations when the grid is connected, the Schneider inverter can consume or send electricity to the grid.
The other type of inverter is the SolarEdge inverter, which is a solar inverter. Its job is to convert DC power from the solar panels into AC power which your house needs.
Having both hybrid and solar inverters connected on a common AC bus is known as AC coupling.
First, let me explain how it works when the grid is happy and we have connection. The solar power from the solar inverters will do the following in priority:
- Power the house; and send excess to
- Charge the batteries; and send excess to
- Send back to the grid
If there is not enough power from solar, then power is supplemented by the batteries or the grid depending how you configure the Schneider inverters. I will not get into how Schneider inverters are configured here.
Now when the grid is out (power outage) and the batteries are fully charged, the solar power has no where to go. To regulate solar power production, the hybrid inverters will communicate to the solar inverters via Frequency Shift Power Control. The hybrid inverters will intentionally shift the output power frequency from its normal 60Hz to something like 61Hz. This is done slowly. The solar inverters detects this anomaly and either throttles its power output or stop producing power completely. Once power regulation is completed, the hybrid inverters will shift back to 60Hz.
The solar inverters will come back online after an arbitrary down time. For SolarEdge, I have observed this to be around 5 to 10 minutes. The idea of having this down time is so that batteries can be discharged while powering the house and create more head room for new solar energy. Unfortunately the SolarEdge down time is not long enough, at least not for my house and my battery storage system. Once solar power is restored, you can end up in a cycle if the batteries are still topped up. The hybrid inverters will again shift its frequency to force the solar inverters to reduce or stop producing power. The cycle repeats until the grid comes back on.
Instead of a repeating the cycle every 5 to 10 minutes, it is better to manually turn off the solar inverters and wait for the batteries to draw down until you have enough head room for the batteries to absorb the solar energy again. For example, you may want to draw down the batteries from 100% to 80%, and then turn back on the solar inverters. In this scenario, excessive solar power can then be used to charge the batteries.
Another matter to pay attention to is UPS (Uninterruptible Power Supply) units. Certain models are very finicky to frequency shift and will actually shutdown instead of continuing to supply power. This is very frustrating as it cuts power to the very items that you are trying to protect from outages.
I had UPS units spread through out the house prior to our solar installation. Now I am simply going to replace these with surge protection power bars.
First Hand Supply Chain Impact
Our last power outage on May 21st, caused one of my two SolarEdge inverters to stop generating power. This effectively caused 50% of solar panels to be ineffective. Considering that the system was recently commissioned fully on May 4th, it was a bit frustrating to go through this. At least the other SolarEdge inverter is still generating power from the remaining 50% of my panels.
Upon a remote assessment of the inverter by SolarEdge, they determined on the 25th that the inverter requires replacement. As of this writing, I have not been given a formal response by SolarEdge that explains why the inverter cease generating power. I assume it is a quality issue on their end, and something from the grid outage during the storm fried something in the inverter. For an inverter that was less than 2 months old, this was slightly concerning.
It took SolarEdge from May 25th to June 10th to ship a replacement. Today is June 15th, and the UPS tracking number still shows “Label Created”.
Apparently recent supply chain issues has caused much shortages resulting in the delay.
Kudos to New Dawn who was able to source another inverter and they promptly installed the inverter today. All is good now.
In summary, we had 50% of our solar panels not producing power for 24 days (from May 21st to June 15). SolarEdge to this day still has not met its warranty commitments because its replacement unit is still in “transit”. If it was not for New Dawn being creative, I would still be out 50% of my solar capacity.
If you are using SolarEdge for off grid applications, perhaps it is wise to store an additional unit if you think solar generation is critical to your livelihood.
Canada Greener Home Grant
In a series of posts, I have documented my experiences and adventures on installing solar panels and backup batteries. One of the incentives that prompted us to start the project is the new Canada Greener Home Grant, which offers a maximum of $5,000 grant towards certain home projects that are classified as “green”. I also mentioned EnerTest as a great company that chaperoned us the entire process of the Canada Greener Homes Grant.
EnerTest was extremely prompt in organizing and conducting the energy audits, which are required for the grant eligibility. I wanted to thank Nick Crosby from EnerTest who played a very supportive role in guiding our family through this, and sometimes very confusing process.
Knock on wood, but I think today we crossed the last hurdle.
If you are embarking on the same grant, take note that you must perform the first energy audit prior to you getting the work done. This is very important.
You will have to perform a second audit once all the work is completed. Make sure you keep all of your receipts and working documents relating to the work.
I would highly recommend Nick Crosby for the job if you are starting a similar journey that I did. Click on his name to email him.
It certainly feels good that the grant is coming our way in 30 days!