Hypermilers in Clarity?

Jdonalds,
What do you mean by "charge the car 100% with home solar"? I have solar panels as well but when I charge my car it goes into the mains just like everything else. Do you have another arrangement?

 

Ozy, You are correct to call this into question. After a year of solar and Clarity I've learned that this isn't always true, and over a years time it isn't true at all for us.

I'll give two cases:

1) Lets say it's mid summer, the sun is high in the sky, and the days are long. The solar system is working at max, supplying close to 6KW. The house is using 3KW. Before I plug the car in I'm pumping 3KW back into the grid. We have net metering so the grid is acting like a battery for me, storing that extra power I don't need at the moment. The meter runs backward. I plug the car in which needs what, 7KW is it? So the solar system now sends that extra 3KW to the car and the grid supplies the other 4KW. It takes 2 hours and 10 minutes to fully charge the car. So we've used about 10KW or so from the grid. Then the load once again drops back to 3KW for just the house and the solar begins to pump it back into the grid. So some power is stored in the grid before plugging the car in, and more is pushed to the grid after the car is charged. Over the whole day we are net positive with the grid. On these best days our solar pumps out 50-52kw. Just as an example say we start out negative since the sun went down last night, but by the end of this day solar has made up for all we used from the grid and still pushed more power out to the grid. We have then fully operated the house, and charged the car, all on solar power. Yes the grid was involved but at the end of the day we are net positive and we don't owe the power company anything. Hence my comment that the car was charged 100% solar. If only this was true every day...

2) Now comes the dead of winter. Rainy season in California. Days are short. The sun is low in the sky. Some tall trees now shade part of the solar. Full cloudy days obscure the sun. Rain further hinders light hitting the panels. Daily solar production is almost non existent. I've recorded as low as 100 watts generated for a whole day. I groan as I push the button on the inverter and see the low level of generation. The car and the house are fully powered by the grid. Ugh! Full sun winter days can generate 25KW for a day. In the summer our system pumps out 50KW or more each day; a megawatt each month.

Net for a year... its a loss. But now we've had solar and the car for over a year. Year over year we paid $1844.68 in 2017 for electricity, and just $291.55 in 2018. In 2017 we didn't have a plug in car. So that $291.55 includes charging the Clarity which we often do twice a day. We banked quite a bit of power in the summer which the electric company graciously store (so to speak) for us until winter (sort of).

This disappointing chart shows the effect of nearly a year of this give and take. If the slope is up we're using more grid power than we're pumping to it. If the slope is down we're banking power. Things should be slightly better in 2019 for several reasons. First that first segment was rising because our inverter was clipping at 5KW so we were unable to take full advantage of the panels. We changed the inverter and also added two more panels. Then we had the huge Carr fire which put thick smoke in the air for six to eight weeks, cutting our solar production. Please God no more fires. I'm anxiously awaiting the turn in this chart when we produce more power than we use.


The other good news of course is we bought much less gas in 2018 than 2017, even though the car the Clarity replaced was a Prius. All together we realized a $2,500 cheaper year due to solar and using less gas. By the way we've only ever charged the car at home. Tonight the car has 22,742 miles on it. My wife and I share the car while the 2005 4Runner (13 mpg in the city) stays parked most of the time.

I've come to realize it would be too expensive to try to make our netmetering come out to $0 at the end of a year. That would require more solar panels, a higher capacity inverter, and trimming some trees ($750). As our electricity is not TOU there would be no benefit to adding a Tesla power bank; the grid already acts like a bank for us. Also if we were to add a battery bank we'd have to add more panels to charge it. As batteries deteriorate over time the benefit reduces over time.

I've also realized that even having a Tesla battery would fail to do the job all the time. We just came out of a period of about a week when we didn't see the sun and it rained continuously for at least 50 hours during that week. We've had 9 inches in January so far. The battery wouldn't be charged by solar and would provide no power for several days. As I said a TOU plan might make a battery a good value.

So on a daily basis we can experience several months of 100% solar charging the car. Sadly for even more months that isn't true.

Summer months the biggest draw is the air conditioner. Our summers are brutally hot (which I love) with highs of 100-112 for several weeks. AC runs 24/7. Still the solar, mid summer, can feed the AC beast, the rest of the house, and the car. Fortunately heat in the winter uses much less power than the AC in summer.

As I said you were smart to point this out. Having solar has been a learning lesson. What is your situation Ozy?

 

I've averaged in the 130-150 mpge range (3.8 to 4.5 miles per kWh) for city driving (not in a great area for hypermiling). For hybrid efficiency, I've averaged 40's and 50's mpg at 70-80 mph highway speeds, and for city I've averaged 60's and 70's. For short trips below 10 miles, and especially 5 miles, I have observed decreasing efficiency, but not as significantly as I did in my previous vehicle (a gen 2 Prius). The decrease for short trips is applicable to electric and hybrid mode.

I haven't used electric on the highway often, but I have observed 100-110 MPGe (3-3.25 miles per kWh) depending on conditions.

My hypermiling technique has not been pulse and glide, just driving smoothly and avoiding harsh acceleration/deceleration. I use the neutral mode sometimes to give my foot a break.

These numbers are good for a Clarity, but I know someone with a Prius Prime achieving above 35 miles of electric range, or above 5.5 miles per kWh, so I'm not particularly proud of my results.

Still, I charge at work for free, so my costs have been very low. I have been going 1,000 to 2,500 miles between gas stops with a 50+ mile commute.

 

I do 5-5.5 miles per kwh in town in my Clarity, not intentionally pulse and glide but I effectively do that a lot between stoplights. I spend a lot of time holding the power at the neutral point as I coast in, since coasting is much more efficient than regen. I still can still get 70 miles estimated range (barely) on my 5 year old car with 77k miles.

 

You are much luckier than me. Mine is 80k miles, bought used at 70k, and I have between 80% and 85% of original capacity. My range is around 40-50 miles depending on driving.
It is a hot climate.

 

Me too, I'm in south Florida.

 

I believe this is related to the potentially insufficient SOC buffer in the Clarity. The bottom is decent, with hybrid mode activating around 20% minimum cell soc, (2 bars, or 10% in hondalink) but the upper limit is 94% to 96% soc, which is really high. (Measured over OBD2).
I recommend to you what I have been doing the past few months. If you only charge to 85% in hondalink (they are soon going to fix the smart charging limits), that is also around 85% maximum SOC on the battery cells. I accomplish this before the fix by disabling smart charging and scheduling the start/stop times in the car.
To enact a lower limit, I activate hybrid mode around 5 miles of EV mode remaining, which is close to 25% minimum individual cell soc, (16% to 18% soc in hondalink, 3-4 bars on the battery indicator. Hybrid mode activates at 10% hondalink soc, which is 0 miles of EV range.)
Limiting to 25% and 85% SOC as detailed above instead of the stock 19%-20% and 94%-96% should double the cycle life of the Clarity battery, based on lithium lifespan vs discharge depth testing I've read.

For my future commute, around 22 miles, I will be targeting 30%-75% discharge depth. I also typically activate hybrid mode, when I need it, around 50% soc (hondalink) to further avoid cycling the battery in a high or low range. Similar to the max charge value for hv charge mode (56%).

 

In a grid-tied application the cost of a lithium battery backup is difficult to justify. Typically, the batteries will just sit, fully charged, and only be used during a power outage. For those who baby their lithium batteries by only charging them to 80-85%, they’ll be paying dearly for 15-20% of capacity that will never be utilized in a home energy storage system. Lithium batteries would be an appropriate choice in an off-grid application.

The “power company as an energy storage system concept” doesn’t hold up during a power outage. Any excess energy generated by the panels and sent to the grid, will not be delivered to a home when the grid is down. Additionally, peak solar production does not coincide with peak demand. Any excess production that isn’t being stored is simply wasted production.

We’ve had a 16kWh FLA L16 battery bank for the past 11 years. They still have about 90% of their original capacity. When they fail, I’ll replace them with a 21kWh FLA bank for about $3200. They got us through an 8 day outage a few years ago. Eventually we’ll install a whole house backup generator which will charge the batteries. That would allow us to run the generator for an hour or two, use the HVAC system, and then shut the generator down and operate off batteries. In the mean time they can be charged with a portable generator and a 48v charger when solar generation in insufficient.

A small amount of maintenance is required. I’ve established a protocol of checking water levels and cleaning any corrosion every 4-6 months along with performing an equalization once or twice a year. In total, maintenance takes about one hour per year.