Category Archives: Electric vehicles

A two year retrospective on solar energy

We are seven days from the end of 2021 with a stretch of sunny weather ahead, and I’m struck by the overall similarity of my power usage and solar production in 2020 and 2021.

First, let’s take a look at the results here with summary graphs from each year.

We’ve used slightly less power (300 kWh) this YTD than last year, but most of that difference will be made up in the next week. Similarly, we’ll make about 100 kWh or a bit more over the week. We’ll have generated 63% of our power over this biennium.

Next, let’s look at weather and monthly grid import.

Utility power consumption net of production

You’ll see that this is a very mild climate, with average highs under 90, and average lows generally above 40. Note that March, April, May, and then September, October, and November are the lowest external consumption. These are the shoulder seasons when HVAC usage is low, and especially in the spring, when production is high. High sun angle in the spring and cool temperatures are perfect for solar production.

For context, this is a 2100 sq ft house, built in 1993. There are just two of us here, and we work had to conserve energy. It’s “southern beach house” style, sitting up on 10 foot posts with a carport and utility rooms under. It has 3 HVAC systems, as a large addition was done in 2002 and it just worked out better to do that. We actually like this as having 3 zones gives a lot of flexibility for temperature management. We have a propane stove, but all other appliances are electric. All lights are LED, and we keep the temperature at 66 in the winter, and 77 in the summer. Baseline house load with no HVACs, water heater, or dishwasher running is 400 to 800 watts depending on which fridges and freezers are running). We could improve our curtailment of vampire loads. We get a lot of beneficial passive solar heat in the winter (love those sunny days that warm the house!), but that’s a double-edged sword with too much summer heat, too.

Now, let’s look at some of the differences in production and aggregate (not net) consumption on the graphs below. December 2020 was much colder than this year, and the difference in power imported is due to that and not just that December 2021 is missing a week. Summer import in 2020 was less than than in 2021. But generally, the cycle of high AC in the simmer and early fall with heat in the winter dominates seasonal consumption differences. The left graph below is 2020, and the right 2021.

However one thing that doesn’t show here is EV charging, which was about 50% higher in 2021 than 2020. In 2020 we put 1.4 MWh into the car. In 2021, this figure was 2.2 MWh. As a rule of thumb you can figure 4 miles per KWh. This home charging is not the total energy use, as this does not count any public charger use or use at the home of friends and family. I have better figures for 2021 on this than in 2020. Public charger usage was about 750 kWh and other charging was about 300 kWh, for an additional 1.05 MWh. This 3.25 MWh is consistent with the 12,800 miles on the car this year and an average of 3.9 to 4 miles per kWh. Without home EV charging in 2021, instead of 63% of energy, we’d show 77% of energy generated.

Our installation is 6.09 kWp (21 REC 290 watt panels) and one Tesla Powerwall configured for zero export. However, we have winter tree shading (in our neighbor’s yard) to the south, and only one row of panels is unaffected. I have 4 panels facing west instead of south, and another set of panels that gets shaded by parts of the house in the winter. My educated guess (and comparison with the results from the NREL PVWatts calculator) is that I’m losing about 1 MWh each year when compared to the ideal.

The bottom line is that rooftop solar can make a big contribution to meeting our energy needs. If you have a house with a southern exposure on the roof, you should look into it. Some utilities and rate structures make it easier and quicker to pay for the system, but it really works!

Solar update

The solar system went live on April 18th, so we’ve had it for about 7 weeks. It’s been interesting, as my awareness of energy consumption has increased dramatically with the monitoring data from the system, and we’ve changed some habits and practices. Also, as “technology” goes, this is dead level easy. Once it’s installed, it just quietly does its job. There will be more later in another post on this “quiet” statement; one side effect is increased RF noise which creates some HAM radio issues.

Now for some details. First, let me say that the system isn’t complete yet, as the Tesla Powerwall battery has not been installed, since it was on backorder. It’s arrived now at the installer, and should be in by the end of June. Also, note that my utility does not support Net Metering, so I have to consume all of my generated power in real time, or store it. Since the battery is not currently in, I’ve left a lot of energy on the table. As we have looked at the consumption patterns, it’s easy to discern when the HVACs run, the water heater runs, the dryer, and other things turn on. We’ve made some adjustments, replaced some lights with LEDs, and we take shorter showers. One of the big items is the battery electric car, a Chevy Bolt. It runs entirely on electricity and has a massive 60 kWh battery. One of the big adjustments we’ve made has been in how we charge the car. Instead of charging as fast as possible, at 7.2 kW per hour, I’ve slowed down the charge to about 40% of that, 2.8 kW. I’ve also set it to charge from 9 to 4 when the solar output is at its highest. The JuiceBox charger makes this easy to manage thru its app. If I need to use the car for long drives on consecutive days, I can increase the rate and draw more from the grid. But if not, let the car capture the sun! The Powerwall, when in, will capture any generated power not otherwise used, and can use that energy after the sun goes down, or for backup power if the grid is out.

So what are the results? We were away from home for 3 weeks in May, so that skews the data, tho the HVACs were on, and we had some construction underway. Here’s the picture so far:

The system has captured, as of this snapshot, 643.55 kWh of power over 54 days. That’s about 12 kWh per day. However, it’s a mix of very low days where 14 kWh Powerwall would have grabbed much more power had it been online, and 20+ kWh days in late May and early June where car charging and HVAC grabbed virtually all generated power. June production, over just 6 days, is over 135 kWh! The projected production with the Powerwall is approximately 16 kWh per day on average.

The car has received 300 kWh over this same time (out of 1.62 mW total consumption), but I think that is slightly understated due to a couple network glitches. Here’s a graph that shows the car charging at 2.8 kW from 9 to 4, with HVAC use skewed late in the day. Note that the house has three relatively old and inefficient HVACs and when these are replaced, the total consumption will drop significantly.

So what’s the bottom line? I think that with the Powerwall the projected production of approximately 5,900 kWh annually is very doable, and I’ll probably exceed that. My savings should be on the order of $600 per year, at current power prices. Assuming modest inflation in grid power, it will pay off in 20 to 25 years. But it’s the right thing to do, and I’ll also have an emergency power system. Also, the instrumentation and data will help to shape conservation efforts over time and that is also a hidden savings.

A day in the life of an EV

Well, not a day, but, with apologies to Solzhenitsyn (damn, I’m glad spell check jumped in here!), it gives me an excuse to extol the virtues of driving an EV. Don’t get me wrong, I like my Silverado, and it does a great job pulling the boat, hauling other trailers, hauling dogs, driving on the beach, and so forth…but I sure do wish GM made electric trucks! I didn’t have but one errand to run today, just a 2.5 mile (one way) trip to the dentist, but I sure do love to drive the Chevy Bolt. Heck, it’s not a Tesla in Ludicrous Mode, but press the sport button, push the accelerator, and you will zip you into traffic with the instantaneous torque only an EV can offer. Zip up to 45 mph, slow down to 35 in the EI business district, back to 45, then whip around the new roundabout (using one pedal driving with huge regen braking) and over to the dentist. Reverse it going back, and I used 1 kWh, about 9 cents, for the 5 miles…and fun to drive.

Need a new car? Do yourself a favor and check out an EV.

Another nice day with Clearwater trout

The first day of Daylight Savings Time means getting up early, more so when you have a two hour and 45 minute, 155 mile drive. A lot further than when this was only 15 minutes from the house, before we moved. My alarm went off at 5:15 so I could make coffee and get out the door to meet Sam at the EV charging station at Durham Regional Library, so I could get a charge on the Bolt while we fished (used 95 kWh for the round trip, so with 60 kWh battery, with temps in the 40s, I needed several hours of juice). Sam picked me up at 8:30, and we headed to Clearwater, for the TU-sponsored stocked winter stillwater trout fishery. It started very slow…only one guy (of 8 rods on the lake) was catching fish, and he caught several while I was watching. I asked him what he was using, and he was fishing a dry as a soft hackle fly, just below the surface. I did the same, and promptly caught a couple nice fish.

Sam was on the other side of the lake, so I walked around the lake to where Sam was fishing, and suggested we have lunch and debrief. We ate, and then went back to to casting stations where the action had been. He promptly caught a nice one!

We then figured out that olive wooly buggers were the ticket, and over the afternoon we each caught a dozen or so, big strong fish, 16-24″. It rained on and off during the day, but the fishing was good in the afternoon and that made for a great time. Good fellowship and lots of trout. A great way to spend a late winter day.

Electric dreams and clean beaches

What does a picture of a Lab fetching a frisbee from the surf have to do electric dreams? Just indulge me for a bit…we’ve been driving the Bolt for two and a half months now, and I’m more convinced than ever that EVs can work for the vast majority of families, particularly if you look at one as a local or “regional” car. Yes, we still have two internal combustion vehicles for the time being, but they are being used for special cases. I have a Chevy Silverado crew-cab pickup I use for hauling the boat to the ramp, and as our long range trip car. We’ll keep the truck for its special abilities. We also have the 2006 Chevy Equinox that Jan drives once per week to Mebane to visit her mother in assisted living, a 400 mile round trip, and we need this vehicle as long as she’s making that trip. For everything else, we drive the Chevy Bolt. We drive to Wilmington, to Greenville, to Jacksonville, to Beaufort, to Morehead, or just to Swansboro. Now that the weather has warmed, we’re getting 5 to 5.5 miles per kWh (up from 4ish mp/kWh in cold weather), for nearly a 300 mile range. Think about the percentage of your drives that fit a 125 to 150 mile circle. I’ll bet it’s pretty large. Need to go further? Keep a second car, or rent for trips. More EVs are coming to market with decent range and dropping prices. If you think about it, you could use an EV for most of your driving, too. Teslas are great if you can afford one, but if not, there are a growing number of options. Look at EVs. Ask your friends who have them. I’ll bet you can make it work, and it’s good for the planet…let’s make drilling for oil and gas a moot point, and keep our beaches clean…and that will keep that dog happy in the surf!

Chevy Bolt after one month

We bought our Bolt on December 12th, just over a moth ago, so I thought I’d take advantage of a lazy, cold Sunday to jot down a few thoughts.

First, overall, both Jan and I are quite pleased. We’ve put about 1400 miles on it. That’s more than we’ll usually drive in a month, which I’m guessing will be more like 1000 miles. It drives very well, and matches stated economy specs. We routinely get well over 4 miles per kWh on running around with trips that are for local (50-60 mile round trips) shopping or errands. We’ve driven from EI to the RTP area twice (175 miles each way), including freeway driving. Once, we overnighted, and then I drove it for a day trip to go fishing on January 13th. On these trips, we got 3.7 to 3.8 miles per kWh. However, it’s important to note that we tried not to exceed 65 mph, even in a 70 mph zone. Also, we ran the heat sparingly as this can reduce mileage by several percent. Instead, we used seat heaters and the heated steering wheel. The heater works very well, you just see the cost directly, since heat is a waste product in an internal combustion engine (ICE). By way of comparison, today we drove to Sam’s Club in Jacksonville, a 54.3 mile round trip, urban driving with about 20 miles at 55-60mph. Used 12 kWh for an average of 4.5 miles per kWh.

The Bolt is fun to drive on curvy back roads, since it has a very low center of gravity, great regenerative braking, and excellent acceleration. A key to good efficiency (higher miles per kWh) is to accelerate moderately from a stop and not use the 200hp engine to show off its capabilities.

A sidebar here on regenerative braking. While you have brake and accelerator pedals, there are two modes to drive an EV, traditional and “one-pedal.” In one pedal mode, it goes when you push down, and brakes (regenerating strongly) when you reduce pressure. This gives excellent control for sport driving and you almost never need to use the friction brake. For freeway driving, however, I shift to traditional mode, especially if I’m going to use cruise control.

The Bolt is roomy, though the seats are narrow. Frankly, if you have a big butt, you won’t like it. I’m 6’5″, 230 pounds, and I’m ok. But a stockier person might have issues. It’s roomy for 4 people, and can seat 5, and works fine for the granddaughter’s car seat. The hatchback-style trunk is good for groceries, and will even hold 2 Labrador retrievers for 3 hours, with the backseat folded down.

Our JuiceBox EVSE (Electric Vehicle Supply Equipment) works well. It’s a misnomer to call it a charger, technically, as the car contains the charger and the EVSE is a smart switch. One thing that was interesting is that in very cold weather low 20s and below, the car will consume power periodically to keep the battery pack warm. This is very evident in the charging logs from the JuiceBox. The opposite takes place in very warm weather, where it cools the battery. The heating process seems to be as much as 2 kWh every 4 to 6 hours. Obviously if you have the car in a garage this is mitigated. The JuiceBox provides the Bolt with its maximum of 7.6 kW input, for an effective rate of about 30 miles per hour. Remember this relates to your efficiency, so that at 3.7 miles per kWh it recharges 28 miles per hour, and at 4.5 miles per kWh, it charges 34 miles per hour.

I’ve just charged the car once at “station,” which in this case was a free charge at a library in Durham, with all other charges being at home at EI, or using the dryer plug in Chapel Hill (but that house is now sold, and we’ll be out in February) and Winterville. I have charging credentials with EVGo, ChargePoint, and Greenlots. I’ll use them at some point. Again the key is that charging an EV is not like going to a gas station and being back on the road in 10 minutes. You just have to think differently about refueling, with the ideal being an overnight stop with an EVSE.

However, again, the key is that an EV will do a heckuva lot of the things you do, and with an ICE 2nd vehicle or a rental as a backup, you can cover the other use cases.

2017 EV sales continue to rise

Saw a good statistical summary of electric vehicle (EV) sales for 2017. Nearly 200,000 battery electric and plug in hybrid vehicles were sold in the US in 2017, up by 26% from 2016, and 1.6% of US sales in December. Estimates are that we’ll see sales of 300,000 in 2018, depending on the Tesla Model 3 rampup, and vehicles like the new Nissan Leaf, and the Chevy Bolt.

The EV is probably still not an “only car” for most folks, but as a second car, it will fill a lot of niches with current and emerging products.

EV chargers

Saw an interesting article on Level 2 and DC fast chargers, with a summary of chargers by state, here. I was interested to see both a good number of chargers in NC, as well as the ratio of DC chargers. The page says the total includes public and private chargers, as well as the Tesla network. What it doesn’t say and probably doesn’t include, are privately owned chargers but made available thru networks like PlugShare. We installed a JuiceBox Pro 40 (a Level 2 charger), which at 40 amps, is faster than many commercial Level 2 chargers. Like many other EV drivers, I’ve listed this on PlugShare in case anyone is in a bind and needs a charge. EV chargers are not as ubiquitous as gas stations, and are nowhere as quick, particularly the Level 2 chargers, but there are more out there than you might think.

Early reflections on the Bolt EV

We’ve had our Bolt 4 days now (we got Nightfall Gray, just as in this stock image) and so far, we are loving this car! Jan drove it home from Virginia Beach, where we brought it. That was a bit over 210 miles, and we were nervous about the range, so we stopped for a couple hours at a Chevy dealership along the way to load some more electrons. We realized, though, that we could have made it if we’d gone direct, the 238 mile advertised range seems to be realistic! We drove it around town some, maybe 25 miles, and then a round trip of about 160 miles to visit my dad for his birthday. Jan let me drive it on the return trip 😎 so I have some good behind -the-wheel time, too. I’ve put together some thoughts on our experiences so far below.

GENERAL OBSERVATIONS ON THE BOLT

The Bolt is a pleasure to drive. It’s quiet, solid and handles well. With the low center of gravity, coming from 1,000 pounds of battery in a nearly 4,000 pound car, it sticks to the road in curves. The biggest knocks are that GM skimped on what we often expect in the interior of a car, finishing the car with plastic rather than wood, basic carpet instead of plush, manual rather than electric seat adjustments, and so forth. Well, yeah, it doesn’t compare to the interior of my spiffy LTZ Silverado. But it’s comfortable, functional, and they put the money in the EV parts. I’ve read that GM pays LG $8,000 for the battery in each car. The infotainment center is great, with a big 10+ inch screen with CarPlay or Android Play. This works well. We have the basic audio system in our Bolt LT, rather than the Bose in the Premier edition, but it sounds fine. There is a plethora of information about the car’s operation, personalization, and configuration. Bluetooth calling works well, with good audio. It’s not luxury, but it’s functional, comfortable (I’m 6’5″ and can easily drive, and can sit in the back seat as long as the driver seat is not all the way back) and roomy. It’s a hatchback with 60/40 split back seats, and feels spacious on the inside, a good job with design.

RANGE

There a few caveats about range. Your driving and use of the car’s other systems all tap the same 60Kw battery pack. If you have a heavy foot, the Bolt will respond. It is rated at 200HP with 0-60 of 6.5 seconds. It will go if you need to pass or merge into traffic. It will also tell you, on a big display, how much energy your decisions cost you from your “tank” of latent power. EV’s (and hybrids) go further on the same power in stop and go driving than on the open road. The Bolt’s EPA rating of equivalent “MPG” is 128 city and 110 highway. We saw this effect. Also, something you might not think of, though, is that the heat (and A/C) will trim the range, by 5-10% depending on how you use it (observation and reading the documentation). The seat heaters and heated steering wheel don’t seem to have much impact. The infotainment center also draws some power, but that’s minimal. It’s the climate system that strongly impacts range. Clearly, this is only an issue if you were trying to maximize range. Range is directly proportional to the size of the battery pack.

CHARGING, STANDARDS, AND CONNECTORS

How, when and where to charge are tied closely to range. To understand this takes some background, which I will attempt to give. This is based off casual research before purchasing, and intensive, highly motivated research in the 4 days after signing the papers 😉. There are three levels of charging, called (so originally!) Level 1, Level 2, and Level 3. Level 1 is with 120V standard outlets, and cars usually have built in charge control circuitry for this. The Bolt can charge at 8 or 12 amps on such outlets, using the included charging cable. This charges at about 3 miles per hour for 8 amps, and 4+ for 12 amps. This means 48-72 hours to fully charge the Bolt’s 60Kw battery. The amperage draw is managed through the UI of the infotainment system. Level 2 is with 240V circuits, at 16-40 amps. This can charge at 12-30 miles per hour, depending on current. I’m planning to install one of these Level 2 chargers at the house. It requires a dedicated 40-50 amp circuit and the charger unit itself. Level 3 is 480V, and can charge a battery the size of the bolt’s in about 2 hours. However, it’s not quite so simple in all cases. There are multiple standards and connectors. The J1772 connector is widely used for Level 2 chargers from many manufacturers, except Tesla. Level 2 connectors are what you find on many public, free chargers. These are typically 16 amp chargers, which would charge a small capacity EV quickly, but an extended range EV like the Bolt takes 18-20 hours on one of these to fully charge. Level 3 chargers are also different, with different plugs and no clear standard. Tesla, of course, has its own. Our Bolt has the DC fast charging option, which is a $750 add-on from the base vehicle. These chargers are not free, and typically require membership in a charger network.

CHARGER NETWORKS AND LOCATIONS

These networks provide access to and billing for chargers that are not free, including Level 3 and some Level 2. I’ve joined ChargePoint and EVgo with pay as you go plans. Their apps show charger locations and even availability of chargers. I’ll explore this more as we try some. There are a lot of chargers in parking decks, municipal parking lots, commercial parking lots, like malls, and so forth. Most Level 2 and most free. Also, car dealers selling EV’s often have a public freely available charger. Most Chevy dealers have them now, it seems. But remember that at Level 2 the J1772 standard rules, and you can charge a Chevy at a Nissan dealership and vice versa, for example. Tesla has a deal with Sheetz gas stations and is putting chargers at some of them, including their Level 3 supercharger. At Level 2, there is now a 3rd party adapter to let a J1772 vehicle use a Tesla charger, and Tesla has an adapter to go to J1772.

DRIVING PATTERNS

A lot of this comes down to the way you use the car. Where are going? How far? Are there chargers at your destination? Even if you don’t have a fast charger where you are going, you can plug into 120V if an outlet is available and get some miles, as the Level 1 charger is portable and rides with your car. If your car is at your house for 12 hours, even a Level 1 charger will put 50 miles on it. Traveling long distances is the bugaboo. You can’t do a 500 mile day with a Bolt unless you find a Level 3 charger for a quick charge. But lots of folks have cars that are not practical trip vehicles, and have another (my Silverado for example) or rent for a trip.

BOTTOM LINE

The Bolt is a practical EV. The price is right. Performance is great. It’s roomy enough for a big driver, and is a flexible hatchback design. Range is sufficient to drive 100 miles to a destination and come back on one charge. Don’t forget that scheduled maintenance on an EV is much lower, no oil changes, and very little periodic maintenance. There are a lot of driving use cases covered here. It won’t work for everyone, but it works for us. At $0.10 per Kw/hour for electricity, it takes $6 for a full charge to go 238 miles. And when we put solar on the house, as we plan to do in 2018, then driving at no fuel cost and no indirect emissions, either.