Powerwalls and Time Based Controls

We are on a Time-of-Day electricity plan, the PG&E EV2 plan. Our cost for electricity is:

		Summer	Winter
Off-Peak	12am - 3pm	$0.31/kWh	$0.31/kWh
Mid-Peak	3pm - 4pm	$0.51/kWh	$0.48/kWh
Peak	4pm - 9pm	$0.62/kWh	$0.49/kWh
Mid-Peak	9pm - 12am	$0.51/kWh	$0.48/kWh

We are incentivized to keep the power-hungry activities like charging the electric vehicle to the daylight hours where solar is plentiful or overnight where demand is low. Unfortunately however, there are several confounding factors to our energy use which make things more complicated.

1. The house is on a hill, the crest of which blocks direct sunlight for longer and longer periods each winter day.
2. We have two Powerwalls, able to store 27 kWh to supply the house at other times.
3. BUT, when we installed the powerwalls in 2019 we claimed the Residential Clean Energy tax credit which requires the batteries be charged using only solar power for five years.

Combining all of these things, we ended up with an unfortunate confluence in the winter months when the hill allows only a few hours of direct sunlight: there is not enough excess solar to charge the batteries while also powering the house.

We would head into the higher priced times of day with little ability to time shift stored solar production. The batteries were never able to charge. Our power bills rose substantially, calling into question why we paid for this stuff in the first place.

The Tesla app has a "Time Based Control" mode, where it takes the time of day and rate plan into account. However its main focus is in exporting solar production during high value hours by running the home from battery. Lacking sufficient production to charge the battery, this resulted in poor outcomes with Time Based Control. I didn't look at it again for the next few years.

 

Hacking Around It

Instead we've come up with techniques to get things working acceptably:

1. On winter mornings set the Powerwall to reserve 100% of its capacity for power outages. All solar production during the day charges the batteries, trying to reach 100%. The home's needs are met from the grid during off-peak hours.
2. When peak hours start, change the Powerwall to 30%. It then discharges to power the home, allowing the evening load to be partially met using stored solar power.
3. Do this every day. Change the Powerwall setting in morning and afternoon, every day, all winter.

I of course wrote software to automate this, but Tesla has only recently decided to offer an actual API to control Powerwalls. For the first few years I was instead using authentication mechanisms and APIs which a community on GitHub would reverse engineer, and which Tesla kept deliberately breaking. I had to watch for errors from my software or, maddeningly, when it would run without error but Tesla ignored its commands.

 

Changing the Game

At the beginning of this month, our five years was finally reached. I set the Powerwall to be able to charge itself using grid power. This didn't immediately change much behavior, until I toggled it to Time Based Control again.

Now, suddenly, things are much improved. At 3pm every day the Powerwall begins supplying the house energy demand, and all remaining solar production is sent to the grid. At midnight when rates drop, the Powerwall charges itself to 100% using grid power, to be ready for the next day.

This is already better than the system I had cobbled together:

• There were many days when the total solar production could not fully charge the batteries. Now, no matter what, the batteries are 100% charged every day.
• We are on the Net Energy Metering plan from 2019. Sending solar to the grid offsets our use at other times, so long as the house can be powered from battery.

 

Futures

I do want to change the current behavior in one way: instead of charging from the grid overnight, I'd prefer the Powerwall try to charge from excess solar. In summer it will usually be able to do so, and in winter it can try and then start charging itself mid-morning from the grid if it isn't going to make it to full. I'm looking into the Fleet API which Tesla published this year for what might be possible.

However, fundamentally, this stuff needs to be easier for the homeowner. I've been writing custom software and manually intervening for years, just to get a decent result out of it. I should not need to do that, after having paid so much for the system install.

One small provision in the Inflation Reduction Act was to remove the five year solar charging mandate for batteries installed after its passage in 2023; the goal is to incentivize more batteries on the grid. With freedom to charge the battery, it should be able to figure out how and when to charge itself. The behavior of the system over time should inform future operation, deciding when to charge from the grid and when to trust that solar power will provide. Next-day solar forecasts can inform this decisionmaking.

Surplus Energy Response

The phrase "too cheap to meter" entered the energy discourse in the 20th century, referring to the potential of nuclear power. Though originally coined to refer to fusion power, the label instead became associated with all nuclear energy. Seventy years later fusion is not here yet, and fission power has been a solid source of baseload power but could never be described as cheap.

The idea of energy too cheap to meter is a compelling one, we just had to wait for an entirely different technology to deliver it: solar photovoltaic. Panels installed on residences and commercial buildings are typically installed "behind the meter," where it directly supplies the energy demand of the building. The proof that solar power is too cheap to meter is that is not, in fact, metered.

Solar deployment has grown incredibly rapidly, faster than the distribution grid would be ready to accept it all. Deployment behind the meter has been essential because the grid in front of the meter hasn't been able to deploy new capacity so rapidly, and solar deployment continues to accelerate. A post by Ben James argues that solar energy can be deployed so inexpensively that using it completely off the grid, for economic activities which can be economical with free energy so long as it can handle being run intermittently only when the sun is shining, is compelling.

• hydrogen production, via electrolysis of water
• fertilizer production, producing ammonia via air capture and energy
• kerosene production, also via air capture
• ... and other chemical processes made possible by prolific free energy

 

Surplus Energy Response

The electric grid has a notion of Demand Response, when there is heavy demand which stresses available generation — for example, by air conditioning on a hot afternoon. We have reached the point where we also have the opposite situation: we need a surplus response. Many builings now produce substantial excess behind-the-meter power during the day, so much so that the grid cannot absorb it all. We need our buildings to become smarter about putting the excess energy to useful work:

• pre-heat or pre-cool HVAC, somewhat overshooting the temperature setpoint while energy is free
• store hotter water, with a smart water system to mix scalding with cold to get the desired water temperature
• charge electric vehicles for free, with knowledge of when the vehicle is likely to be needed
• charge up batteries in appliances throughout the building, allowing high peak load appliances to be installed in buildings not originally built for them

Yet we can take it even further. Limitless free energy, albeit at limited time ranges within a day, allows us to make choices we would never have otherwise considered.

• heat a pool or hot-tub to be ready for impromptu human use at any time during summer months
• run heat pumps in a sunroom, open to fresh air yet maintained at a comfortable temperature
• indoor urban hydroponics, pre-engineered gardens which are never too hot nor cold and provide generous fresh produce

In building enthusiasm for the energy transition, providing services which seem impossibly luxurious yet are provided entirely by surplus energy would be a compelling outcome.

Getting Started with German Genealogy

This is the second post in a series about conducting genealogical research in Germany. The earlier post is "German Genealogical Research", describing where records can be found.

Taking that first step to actually search for ancestors can be daunting. Therefore as an example, I'll walk through how research of my wife's German family began.

 

Step 1: Parent

My wife's mother, Gundela, moved from Germany to the US in 1958. We knew Gundela's birth date and that she had been born in Hannover. A bit of searching turned up the website for Standesamt Hannover, with "Urkundenservice" partway down the page leading to an order form for:

• Geburtsurkunde Standardformat (birth record)
• Registerausdruck (copy of the birth register)
• Geburtsurkunde mit Geburtszeit (birth record with time of birth)

We ordered these in late 2020, at a cost of 10 Euros each / 30 Euros total. The three documents are shown below. Needless to say this was the only Geburtsurkunde mit Geburtszeit — the one with the stork — we ever ordered.

The Geburtsurkunde Standardformat gave us the full names of her parents Karl and Hedwig. However the Registerausdruck, a copy of the original handwritten register entry, brought even more information. We knew that Gundela had been adopted by Karl, and the Registerausdruck describes the adoption in the block of text in the right margin. It gave a date of December 14, 1940. In 1940, when Gundela was six, the Standesamt updated the record with a description of the adoption in the margin.

The German handwriting in the birth register uses what is now considered an obsolete cursive lettering called Kurrentschrift. After World War II, Kurrent was replaced by a more modern cursive lettering and then by typewriters. We were able to decode most Kurrent writing with some time and the lettering chart from Wikipedia, but more recently discovered Reddit's r/Kurrent with people happy to help with more difficult transcriptions.

 

Step 2: Grandparents

With a date and full names we next ordered the marriage record for Gundela's parents Karl and Hedwig from Standesamt Hannover, costing another 10 Euros. This was a case where the Standesamt did extra work to be helpful: 14 Dec 1940 was the date of adoption, but not the date of the marriage. The Standesamt located the marriage record a few months earlier, in May 1940, and sent it to us.

More Kurrentschrift! The first page of the marriage record contains the names, birthdates, and birthplaces of the bride and groom Hedwig and Karl. The lower half of the second page lists the parents of the bride and groom, my wife's great-grandparents, including their birthdates and places.

In the upper left margin of the first page is an update that the ehefrau (Hedwig) died in 1978 and giving the record number in Hannover. These updates are hit-or-miss: Karl died in 1993 but the marriage record was not annotated for his death.

 

Step 3: Maternal Great-grandparents

The marriage record of the grandparents supplied the birthdate and birthplace for the great-grandparents, allowing us to order the next set of records. The maternal great-grandparents were born in the 1880s outside of Hannover. Their records had originally been recorded at a Standesamt, but records that old are moved to an archive.

In one of the continuing themes of genealogical research in Germany, there were several archives around Hannover: the Stadtarchiv for the city itself, and the Region Hannover archive for the towns nearby. Their records were at the Region Hannover archiv.

We've yet to find an archive with a web order form like many Standesamt use, but every archive has accepted requests through email. DeepL is very helpful in composing an email request. The practices vary substantially from one archive to another:

• Some are happy to send PDFs in email, others always send paper copies as part of their processing.
• Some will send the documents along with an invoice, trusting that it will be paid, others require payment in advance.

This is an example of an email to the Region Hannover archive to request the Geburtsurkunden for the great-grandparents:

Ich bin auf der Suche nach der folgenden Geburtsurkunde:

    Georg Heinrich August Koch
    *: 25. Feb 1884, Otternhagen
    +: unbekannt

    Minna Luise Elise Oltrogge
    *: 19. Mai 1888, Borstel
    +: 22. Jun 1976, Neustadt am Rübenberge

Meine Adresse ist:
    Denton Gentry
    123 Main Street
    Anytown, AA 12345
    USA
Aber PDF in EMail ist besser für mich.

Ich verpflichte mich, alle Tarife zu zahlen.
Ich kann Überweisungen in EUR oder SEPA senden.

The invoice for an Archiv usually requires an electronic transfer to a bank account, none so far have been able to accept a credit card. We use Wise to send a SEPA transfer, an electronic check in Euros, for just a few cents in fees.

Great grandmother Minna's birth record had a note in the left margin which told quite a story: her birth had been out of wedlock, a big deal in the very Lutheran 19th century Germany. The biological father later legitimized the child by marrying the mother and updating the birth record of the child to use his own family name.

 

Step 4: Paternal Great-grandparents

The paternal grandparents were older, born before 1874 and pre-dating civil recordkeeping at Standesämter. Their birth records were in church books. This was our first venture with Archion, which holds digitized Lutheran and Evangelical Church books from much of Germany. We paid about 20 Euros for one month of access, using a credit card.

Church books can be kept for each type of record or held as sections in one book:

• Taufbuch: baptism records
• Bestattungen or Beerdigungen: burial records
• Trauungen: marriage records
• Kirchenbuch: one large book with sections for each type of record

The place of birth from the marriage record led to the correct Church book to look in, and then look for the birthdate.

95. November, der 27.- Mevert, Carl Heinrich, ehelichen Sohn des Friedrich
                       Wilhelm Mevert von Nr 1 in Beeke, und seiner ehefrau
                       Sophia Luisa geb. Heshe von Nr 10 in Luhnde, geboren
                       der sechzehnten der November.

 

It is totally possible to research one's own family genealogy, it is not necessary to pay someone else to do it. It only takes a bit of time and small amounts of money.

EVs Are More Than Their Range

We have a 2016 Kia Soul EV. It uses a 27kWh battery pack, quite small compared to other electric vehicles which commonly have 50+ kilowatt hours of capacity. We've used the Kia primarily as a city car on local roads with only the occasional highway trip. As a city car it has been fantastic, small and easy to park yet large enough to handle our typical trips like groceries and taking kids to school.

When new the car would get 80+ miles in city driving on a full charge. Its battery slowly degraded each year until a few months ago when it began dropping quite rapidly. OBD diagnostics can read the state of each individual cell in the battery pack, enough of the cells had failed for it to be replaced under warranty.

This post is not about the battery replacement process, though we are quite happy with Kia and the warranty support.

This post is about how useful we find an electric vehicle even with fairly limited range, and how little difference it made when its range suddenly increased. The first time we charged the car with its new battery pack its range estimate read 101 miles. Honestly I didn't even know it could display three digits.

We charge the car using solar production in excess of what the house is using. Where before we would charge the vehicle every day, we're now charging it mostly on weekends. It has triple the battery capacity but 5x above the reserve level we like to keep. It can go all week on our usual errands.

It seems somewhat strange to me but our use of the vehicle has not really changed with all this extra range. The new energy ecosystem was already compelling for us:

• Solar panels on the roof produce substantial extra energy during the day.
• Not having to pay for gasoline or oil changes further improves the economics.
• Most trips are short. On any given day we drive just a few miles.

When we talk about the fossil energy system we point out how damaging its emissions have been, and how the cost of that damage is completely externalized from production. All of that is true. Another aspect of the fossil energy system is how ruthlessly it pulls profits back up the supply chain, resulting in enormous profits at the top and almost nothing to the rest of the ecosystem. Gas stations make their profit from snacks, carwashes and oil changes, the gasoline sale merely brings people in while the supplier takes all of the profit. Methane pricing encourages spikes to ruinous prices for electricity distribution operators.

Distributed energy production and distributed ownership of energy production also results in more of the benefits being distributed. Our little electric car is part of a larger whole where one can capture and use the energy from the Sun without some entity in the middle siphoning off the benefits of doing so.

Update: a few weeks after publishing this, both of us parents had conflicting appointments and I had to drive the EV further than its previous battery could have managed. It was glorious. More range is certainly better. Still, our use of the car is mostly just short trips around town.