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An Epic Journey Toward Cleaner and More Efficient Transportation
You know how a small project can turn into a big one very easily? This is what happened when I moved to a different house, and at about the same time, decided to buy a Tesla. It turned into a project of epic proportions – although, I have to admit- I brought it on myself, and honestly have enjoyed every minute of it.
First, here is what happened with the house. About 15 years ago, friend of mine built a house up on top of a hill overlooking the northern end of Lake Tuscaloosa. I told him, “If you ever go to sell this place, talk to me first.” And, he did! I was fortunate to be in a position to buy it. Now, I had to have some electrical work done to support the hot tub we were adding, and also electric car charging, and a large amateur radio station. The electrician contacted Alabama Power to see if the existing service could handle the additional loads (we knew that the main panel was already close to capacity – on cold winter nights, our 5-ton heat pump runs almost constantly). They said the service would need to be upgraded (along with the main panel)… and that they would do this at their own expense. What a project that turned out to be, just by itself. While our electrician upgraded the main panel from 200 amp to 400 amp, Alabama Power brought in an array of equipment and personnel to bore in a new 5-inch conduit for 300 feet between the power pole and the road, and the main panel:
The guys boring the hole for the conduit were experts – after 300 feet, they were able to control the drill so that it came in between the sewer line below and water line above (separated by about 18 inches), and also miss the AT&T line. The project was supervised by a couple of tiny, goose-stepping chihuahuas.
Once the hole was bored, they set about pulling in the 5” conduit:
All went well until the conduit was pulled in about ¾ of the way back, where it became stuck. At that point, they had to dig down about 10 feet to it and splice it there; then they pulled in 500 MCM electrical cable for the residential service.
I believe this means each conductor has a cross section of 500 square millimeters – each of the 4 cables (a pair of 240 lines, neutral, and ground) are about an inch in diameter.
Now we had 400 amp service, capable of providing a sustained load of 320 amps.
Alabama Power’s crew was here for 4 days at $1500 per day – I figure the labor plus materials for this upgrade cost them about $7000. I didn’t tell them at the time that I was planning to add a grid-tied solar photovoltaic system which should actually drive my electric bill down. More on that later.
Now why an electric car?
I have always tried to pick the most energy-efficient vehicles. Sure, there are more efficient modes of transportation than cars, but since moving away from New York in 1969, I have never been fortunate enough to live and work in a place that had any kind of public transportation. First there were the diesels (I had two of the ill-fated attempts by GM to do diesels on the cheap in the 1989s - both of mine ran very well, but as an engineer I knew how to fuel and care for them; not everyone was so lucky with them). Then a VW Jetta diesel which got a delightful 52 mpg (probably emitting lots of oxides of nitrogen, but hey, you can't have everything, regardless of demands by the CEO). Then once in the lower management ranks at Mercedes Benz US International, I bought a used E300 diesel through ebay. That car had 125,000 miles on it when I bought it (just getting broken in). It wad still running fine when I sold it with 335,000 miles on the odometer.
Then I thought, can I find something even more efficient? I leased a Nissan LEAF. This let me enjoy the zero gas plus takes-off-like-a-scared-rabbit experience for 3 years while letting Nissan carry the battery risk. The LEAF was perfect for my 40 mile round trip commute- now at the University of Alabama I somehow persuaded the University to let Chargepoint put a couple of charging stations in the parking decks. At the end of 3 years and 35,000 miles, the batteries still had almost their original capacity. Now I was confident enough to go for the Tesla. I waited with bated breath to see how the Model X's release would go. I much preferred the styling of the Model S; and, as a former car assembly plant guy, I foresaw some of the problems now being experienced with building the falcon doors (what a terribly hard thing to build and adjust... and I expect the warranty costs to be very high on these. So I ordered a Model S. I saw on my MyTesla page a delivery window the car would be delivered April 20 to May 4. By strange coincidence, this corresponded exactly with a long planned cruise around Italy for our 25th wedding anniversary. I asked the Marietta sales center to hold the car for May 4, and we flew back to Atlanta (where we had put our other vehicle at the airport Doubletree with park-n-fly). We went for delivery. Oh-ho, delivery day! This is a 90D.
Being familiar with the MS after having obsessed about it for over a year, I asked for the delivery briefing to be brief. I did wonder if we would need to go via the Auburn supercharger, but since the 90D was charged to 285 mile range this was unnecessary. We drove both vehicles the 220 miles home without a hitch. The Monroni sticker gave the car's fuel economy as an equivalent 100 mpg.
Now, what could I do to make my transportation even more efficient? Solar panels!
I decided on a grid-tied system. SolarTechnology of Eva, AL, designed a 10kw system using SolarEdge optimizers and inverter (this was necessary since, although my south roof is perfectly sited for panels, we have some large trees that would shade part of the array in the mornings).
The system has 38 260-watt panels (you can’t see them all in the photo):
These are connected with 2 strings of 19 optimizers each to a 10 kw inverter. I did something out of the ordinary here – I specified common-mode chokes between the optimizers (and also between the optimizers and the panel). This is to minimize radio frequency noise created by the system (the optimzers are like switching power supplies, so can be RF-noisy).
We are still working the kinks out of the solar system. String 1 works great. We think the chokes may have been wound incorrectly on string 2, because some of the optimizers don’t sync with the inverter (OK, maybe they communicate occasionally, but not enough to produce power). So usually I get 3.5 kW to 6 kW during the day. (I should be able to get 6 kW to 8 kW). We will be taking some panels off to check the wiring later in the week.
Will I be able to charge my Tesla using this system? Well, sort of; the system is grid-tied and hooked up in parallel with all other loads in my house (including the 5-ton HVAC, hot tub, and electric dryer). If we work hard to ensure that we only use one of these heavy loads at once, then I guess I could charge the car. Other than that, I have received Alabama Power’s PEV Rate Rider, which gives a 15% discount on power used between 9 PM and 5 AM, and schedule charging during that time. The solar PV system will have the effect of replacing the power I use at night. (Not as cool as directly charging the car using the system, but I will experiment with this a bit once the system is fully operational).
The large box between the (white) inverter and the main panel is part of the RFI filter. The whole solar system is extensively filtered to hold down radio noise, so that my other hobby (amateur radio) should not be affected (there will be some sensitive antennas near the solar array).
We are still working the kinks out of this complex system, but I anticipate that we should be able to get about 1,400 kwh out of it per year (using most of it locally, so that it is a direct cost savings). Alabama Power will pay for energy pushed out to the grid, but only at wholesale rates (I don’t complain about this – look what they spent on my upgrade, all on the grid side). There is also an additional rate available from Alabama Power for owners of EVs: the PEV Rate rider, which gives you a 15% discount on power you use between 9 PM and 5 AM.
And all this just to run this 14-50 outlet in the garage for the Tesla!
You know how a small project can turn into a big one very easily? This is what happened when I moved to a different house, and at about the same time, decided to buy a Tesla. It turned into a project of epic proportions – although, I have to admit- I brought it on myself, and honestly have enjoyed every minute of it.
First, here is what happened with the house. About 15 years ago, friend of mine built a house up on top of a hill overlooking the northern end of Lake Tuscaloosa. I told him, “If you ever go to sell this place, talk to me first.” And, he did! I was fortunate to be in a position to buy it. Now, I had to have some electrical work done to support the hot tub we were adding, and also electric car charging, and a large amateur radio station. The electrician contacted Alabama Power to see if the existing service could handle the additional loads (we knew that the main panel was already close to capacity – on cold winter nights, our 5-ton heat pump runs almost constantly). They said the service would need to be upgraded (along with the main panel)… and that they would do this at their own expense. What a project that turned out to be, just by itself. While our electrician upgraded the main panel from 200 amp to 400 amp, Alabama Power brought in an array of equipment and personnel to bore in a new 5-inch conduit for 300 feet between the power pole and the road, and the main panel:
The guys boring the hole for the conduit were experts – after 300 feet, they were able to control the drill so that it came in between the sewer line below and water line above (separated by about 18 inches), and also miss the AT&T line. The project was supervised by a couple of tiny, goose-stepping chihuahuas.
Once the hole was bored, they set about pulling in the 5” conduit:
All went well until the conduit was pulled in about ¾ of the way back, where it became stuck. At that point, they had to dig down about 10 feet to it and splice it there; then they pulled in 500 MCM electrical cable for the residential service.
I believe this means each conductor has a cross section of 500 square millimeters – each of the 4 cables (a pair of 240 lines, neutral, and ground) are about an inch in diameter.
Now we had 400 amp service, capable of providing a sustained load of 320 amps.
Alabama Power’s crew was here for 4 days at $1500 per day – I figure the labor plus materials for this upgrade cost them about $7000. I didn’t tell them at the time that I was planning to add a grid-tied solar photovoltaic system which should actually drive my electric bill down. More on that later.
Now why an electric car?
I have always tried to pick the most energy-efficient vehicles. Sure, there are more efficient modes of transportation than cars, but since moving away from New York in 1969, I have never been fortunate enough to live and work in a place that had any kind of public transportation. First there were the diesels (I had two of the ill-fated attempts by GM to do diesels on the cheap in the 1989s - both of mine ran very well, but as an engineer I knew how to fuel and care for them; not everyone was so lucky with them). Then a VW Jetta diesel which got a delightful 52 mpg (probably emitting lots of oxides of nitrogen, but hey, you can't have everything, regardless of demands by the CEO). Then once in the lower management ranks at Mercedes Benz US International, I bought a used E300 diesel through ebay. That car had 125,000 miles on it when I bought it (just getting broken in). It wad still running fine when I sold it with 335,000 miles on the odometer.
Then I thought, can I find something even more efficient? I leased a Nissan LEAF. This let me enjoy the zero gas plus takes-off-like-a-scared-rabbit experience for 3 years while letting Nissan carry the battery risk. The LEAF was perfect for my 40 mile round trip commute- now at the University of Alabama I somehow persuaded the University to let Chargepoint put a couple of charging stations in the parking decks. At the end of 3 years and 35,000 miles, the batteries still had almost their original capacity. Now I was confident enough to go for the Tesla. I waited with bated breath to see how the Model X's release would go. I much preferred the styling of the Model S; and, as a former car assembly plant guy, I foresaw some of the problems now being experienced with building the falcon doors (what a terribly hard thing to build and adjust... and I expect the warranty costs to be very high on these. So I ordered a Model S. I saw on my MyTesla page a delivery window the car would be delivered April 20 to May 4. By strange coincidence, this corresponded exactly with a long planned cruise around Italy for our 25th wedding anniversary. I asked the Marietta sales center to hold the car for May 4, and we flew back to Atlanta (where we had put our other vehicle at the airport Doubletree with park-n-fly). We went for delivery. Oh-ho, delivery day! This is a 90D.
Being familiar with the MS after having obsessed about it for over a year, I asked for the delivery briefing to be brief. I did wonder if we would need to go via the Auburn supercharger, but since the 90D was charged to 285 mile range this was unnecessary. We drove both vehicles the 220 miles home without a hitch. The Monroni sticker gave the car's fuel economy as an equivalent 100 mpg.
Now, what could I do to make my transportation even more efficient? Solar panels!
I decided on a grid-tied system. SolarTechnology of Eva, AL, designed a 10kw system using SolarEdge optimizers and inverter (this was necessary since, although my south roof is perfectly sited for panels, we have some large trees that would shade part of the array in the mornings).
The system has 38 260-watt panels (you can’t see them all in the photo):
These are connected with 2 strings of 19 optimizers each to a 10 kw inverter. I did something out of the ordinary here – I specified common-mode chokes between the optimizers (and also between the optimizers and the panel). This is to minimize radio frequency noise created by the system (the optimzers are like switching power supplies, so can be RF-noisy).
We are still working the kinks out of the solar system. String 1 works great. We think the chokes may have been wound incorrectly on string 2, because some of the optimizers don’t sync with the inverter (OK, maybe they communicate occasionally, but not enough to produce power). So usually I get 3.5 kW to 6 kW during the day. (I should be able to get 6 kW to 8 kW). We will be taking some panels off to check the wiring later in the week.
Will I be able to charge my Tesla using this system? Well, sort of; the system is grid-tied and hooked up in parallel with all other loads in my house (including the 5-ton HVAC, hot tub, and electric dryer). If we work hard to ensure that we only use one of these heavy loads at once, then I guess I could charge the car. Other than that, I have received Alabama Power’s PEV Rate Rider, which gives a 15% discount on power used between 9 PM and 5 AM, and schedule charging during that time. The solar PV system will have the effect of replacing the power I use at night. (Not as cool as directly charging the car using the system, but I will experiment with this a bit once the system is fully operational).
The large box between the (white) inverter and the main panel is part of the RFI filter. The whole solar system is extensively filtered to hold down radio noise, so that my other hobby (amateur radio) should not be affected (there will be some sensitive antennas near the solar array).
We are still working the kinks out of this complex system, but I anticipate that we should be able to get about 1,400 kwh out of it per year (using most of it locally, so that it is a direct cost savings). Alabama Power will pay for energy pushed out to the grid, but only at wholesale rates (I don’t complain about this – look what they spent on my upgrade, all on the grid side). There is also an additional rate available from Alabama Power for owners of EVs: the PEV Rate rider, which gives you a 15% discount on power you use between 9 PM and 5 AM.
And all this just to run this 14-50 outlet in the garage for the Tesla!
The Solar Technology guys are supposed to come here today, and remove some panels to diagnose why most of the optimizers on one string don't communicate with the inverter. We suspect it is because one or more of the ferrite cores between the optimizers are wound wrong, so the differential mode communication that the optimizers use is being filtered out. Not sure if this can be caused by a single mis-wound one, but it seems possible, depending on where it is located. We shall see...
Yay! The Solar Technology Alabama guys found the problem with my system and fixed it - now ready for full power output.
Here's what was wrong: using the design of Tony Brock-Fisher (amateur radio K1KP) and colleagues, we installed common-mode chokes (radio frequency interference filters) between the optimizers. This avoids having RF hash getting into the antennas of my ham radio station. Some of them were wired backwards, causing the signaling used between the optimizers and the inverter to be heavily attenuated, so the optimizers on one string were continuously re-starting and never producing power. This was corrected yesterday, but not sunny enough to give it a complete test. Hopefully we'll have some full sun today to re-sync everything. My goal is to get the system to where it can produce 8 kW + in full sun... enough to charge Elecsis (at least a goodly part of him)... will post further results as they come in...
Here's what was wrong: using the design of Tony Brock-Fisher (amateur radio K1KP) and colleagues, we installed common-mode chokes (radio frequency interference filters) between the optimizers. This avoids having RF hash getting into the antennas of my ham radio station. Some of them were wired backwards, causing the signaling used between the optimizers and the inverter to be heavily attenuated, so the optimizers on one string were continuously re-starting and never producing power. This was corrected yesterday, but not sunny enough to give it a complete test. Hopefully we'll have some full sun today to re-sync everything. My goal is to get the system to where it can produce 8 kW + in full sun... enough to charge Elecsis (at least a goodly part of him)... will post further results as they come in...
Hugh Mannity
Mediocre Member
Electric700
Active Member
I definitely agree, congrats! Also this is the first solar installation with an RFI filter that I've seen.
Thanks... I implemented a design published in QST magazine (April 2016). I have a few imperfections in it yet... the installers pulled out 7 of the 19 inter-optimizer ferrite cores in string 2 in their effort to get it working, and never put in the triple chokes at the interface between the panel rack and the lines to the inverter (they did twist the wires though, so I am hoping this will hold down radiation coming from the DC lines). I am just now starting to work on antennas (none up yet), so I can't ever really yet measure the RFI output of the system... we shall see...
First antenna up (80-meter dipole) , oriented with end of antenna pointing toward house - so far I don't notice any noise (but then, the end of a dipole is a null area, so this is to be expected). Next, I need to start working on 20 meters through 10 - will put up DX Engineering Hex beam, and see what noise we get from solar array, if any...
I just noticed a typo in the original article, saying we could save 1400 kWh per year using the solar system. This should be 1400 kWh per month.
Here's the latest: yesterday, my MS needed a small amount of charge (40 miles worth), and I was able to charge it using pure solar power. The bad news is that all this extra current was available because my whole-house HVAC system went out. Now I will replace that with a SEER 20 unit. I will save energy no matter how much it costs me!
Solar Technology Alabama is still working on getting full output out of my system... for a while, all panel-optimizer pairs were producing full output except for one... when they tried to fix that one, this disabled the entire string. The RFI filtering adds a wrinkle to it, so this may be the root cause... the chokes have to be wired a specific way, and it is possible to get this wrong - although that may not be the problem, since I basically reproduced a system that another ham radio operator got working fine. The installers are coming back to give it another shot later in the week...
iwannam3
Active Member
Have you looked into ground loop heat exchanger for your HVAC? Eliminates the fan noise too. You can also use it to heat your water and with a water to water heat exchanger heat the hot tub.
Electric700
Active Member
I did think about a geothermal system, but I didn't go very far with this because my lot is covered with beautiful hardwood trees, and I would have to fell some of these (maybe a lot of them) to make room for a geothermal system (i.e., with underground piping). Another option that was suggested to me by friends was this: my property is lakefront, and theoretically, I could draw water from deep in the lake (it goes down to 35' just past my property line) both for heating and cooling. This may be a plan for the future. I didn't go very far with this in this case, though, because my HVAC (heat pump & A/C) broke down entirely, and in the middle of an Alabama summer (you know, 98 degrees in the shade every day for months), one is desperate to get a running system in ASAP. The lake water plan would involve pumping water up a 75' cliff and then through a heat exchanger (which would have to be a heat pump also to handle our winters which can get cold); this is not a popular thing to do in this area, so it would be hard to find an installer - if I had a month or two to accomplish this, it might have been possible, but I simply could not handle having the HVAC down in midsummer for any length of time, so I simply took the easy route and shelled out for an Amana SEER 20 conventional system. In 10 or 15 years, when this system starts getting old, I may consider a geothermal system that uses lake water.
My parents (in Kitty Hawk, NC at the time) put in a geothermal system at the beach when they first built their house there in 1979; it was a disaster. First, it didn't use a closed-loop piping system, but rather pumped water from the aquifer and then returned the water back to the aquifer after rejecting heat or acquiring heat. The heavily iron-laced water soon built up a thick layer of scale inside the heat exchanger which had to be cleaned out with acid a couple times per year. In summer, rejecting heat into the aquifer made the tap water run unpleasantly warm. The maintenance on the system far exceeded any energy cost savings. After a couple years, there was a monster storm where power went off for a week with a severe cold snap - the whole system froze up and split. After that, we put in a conventional heat pump & never looked back, So I have a nervousness about geothermal systems. I'm sure they can be done right, but finding a competent designer/installer is the trick, and can be almost impossible if you live in an area where such systems are not popular.
Solar system is now fixed and producing full output! My installer had a lot of problems with the ferrite core filters I had them put between the optimizers - some of them were wound wrong (they have to be bifilar), and finally it required removing about 8 of the 38 cores to fully eliminate signal damping between the optimizers and he inverter.
Here is an example of a "perfect day," i.e., few clouds came by, so the solar system produced all that it could all day, Notice the slow start to the day - trees block the panels for the first part of the morning, and full output is achieved between about 12:30 PM and 3 PM.
I estimate the payback period to be roughly infinite, but at least I have the satisfaction that I produce more power than my Tesla requires almost every day, sometimes several times as much (I expect this to be less in the winter - also, the curve will be different in winter because the leaves will be off the trees). Why an infinite payback period? We have a high monthly cost to connect to grid here, so it negates much of the $ savings, ending up with maybe a less than $40/mo savings on a $21k system (after federal tax credits) - and I don't expect the highly complex optimizer and inverter combination to run for 38 years with no maintenance or replacement of anything. In Alabama, if you want real payback on a system, you have to go off the grid. (That said, after a year of observing the system's output, I plan to investigate whether a Powerwall could be used to reduce grid demand during pear hours (varies by season), which may let me eliminate the $50/mo "capacity reserve" fee via a different rate schedule. That only works if you can nearly completely replace your demand during peak hours (otherwise, you're paying 70 cents per kWh at that time)). Will keep you posted...
Here is an example of a "perfect day," i.e., few clouds came by, so the solar system produced all that it could all day, Notice the slow start to the day - trees block the panels for the first part of the morning, and full output is achieved between about 12:30 PM and 3 PM.
I estimate the payback period to be roughly infinite, but at least I have the satisfaction that I produce more power than my Tesla requires almost every day, sometimes several times as much (I expect this to be less in the winter - also, the curve will be different in winter because the leaves will be off the trees). Why an infinite payback period? We have a high monthly cost to connect to grid here, so it negates much of the $ savings, ending up with maybe a less than $40/mo savings on a $21k system (after federal tax credits) - and I don't expect the highly complex optimizer and inverter combination to run for 38 years with no maintenance or replacement of anything. In Alabama, if you want real payback on a system, you have to go off the grid. (That said, after a year of observing the system's output, I plan to investigate whether a Powerwall could be used to reduce grid demand during pear hours (varies by season), which may let me eliminate the $50/mo "capacity reserve" fee via a different rate schedule. That only works if you can nearly completely replace your demand during peak hours (otherwise, you're paying 70 cents per kWh at that time)). Will keep you posted...
skitown
Member
Sorry to be so tardy on answering this, but I only just now noticed the above post. I believe my roof is indeed standing seam. I don't know the mounting system in detail, this was handled by solar installer. I can find out if someone wants to know. My understanding is that the mounting points are screwed to the underlying roof (not just clipped to the steel sheets) - this means you do have to drill through the roof seams. No leaks so far after 6 months.
A small update - I noticed there was a sound coming from SolarEdge inverter that sounded like an arc. (In my past experience, this sound eventually leads to a circuit card being burned through). A $345 inspection by Solar Tech Alabama (with help from SolarEdge) did not reveal any visible damage inside inverter; SolarEdge also reported that their diagnostics did not show any problems being logged by the inverter. I don't hear the noise now. (BTW, I do have a recording of it, so I can prove that I was not hearing things!). Will continue to monitor this and see if anything changes...
Here is a video where you can listen to the odd sound coming from SolarEdge inverter; but so far, no problems have resulted. It was suggested that this sound my be due to electrical noise coming from elsewhere (my house, the grid), but this seems unlikely because I have extensive filtering between the panel and the inverter to make it radio-quiet for amateur radio activities.
Ham operator here too... If you were not getting any random RF from the unit when it was making that noise, perhaps the noise wasn't electrical. It almost sounds mechanical to me. Any transformers or inductors that might be vibrating a loose shield, or a relay that might be chattering? I don't suppose the unit has a hard drive in it. That's the closest sound I can think of (random seeks).
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