Thursday, June 22, 2023

Smart low cost power controller/monitors for EVs?

My 20+ years old burglar alarm went off while I was away for the weekend and the neighbors, thinking I was in trouble, called an ambulance. So I decided to buy a new alarm. The new alarm is part of a smart home system. One of the 133 optional extras is a plug in smart energy use monitor and controller. There are many such controller/monitors available, for less than $20 each. I realize these consumer devices might not be up to the task of car charging, but could a similar distributed arrangement be used for EV charging in an apartment building? 

The idea is to avoid running an individual cable from each car space back to a central control/metering point in a basement. Instead the control and metering would be at the socket, with the sockets wired in parallel. Also the wiring would only need to carry about one eighth* the load the sockets could theoretically supply. There would just need to be a dumb circuit breaker for each string of sockets, in case the automation failed and tried to power too much at once. 

Smart high power chargers already have the capacity to be remotely controlled and used for metering, but cost thousands of dollars, and require expensive high capacity circuits to be run to the building. The power also costs money. A low cost alternative would be an ordinary domestic outlet with a smart controller built in. The householder would simply plug their car in to charge, or if security is needed, use an app to start. The smart system would charge only about one in eight cars at a time*, monitoring which cars had charged, & which would accept more. 

A workable setup might use a run of 20 amp cable, with 16 sockets, with only two sockets ever being active. A system ration the power available, between cars.  The householder could have the option of only using off peak low cost power, or on-site free surplus solar power.

 * Back of the envelope calculation: 

The average Australian car travels about 33 km a day.

An electric car, such as the Tesla Model S, uses 19 kWh/100 km.

So that is 6.27 kWh per day per car needed. 

From an Australian domestic outlet you get 2.4 kW.

So it will take 2.6 hours to charge for an average day driving. Let us round it up to 3 hours. So in 24 hours you could charge 8 vehicles from one outlet.

ps (added 6 July 2023): Laws restrict what the body corporate which runs an apartment block, and companies supplying power, can do. The body corporate typically can't charge householders for electricity generated on its own roof, nor can they contract for a bulk supply, & charge for that. Also the companies who can charge, and how much they can charge, is heavily regulated, creating monopolies which can make super-profits. An alternative approach might be for the body corporate to levy householders a fixed amount in advance for car charging. This would be based on the number of car charging spots the household has. If the charging is only low rate, it may not be worth metering individual apartment use: everyone would pay the same amount per car. If it is worth metering, there could be a refund, for power not used.

Wednesday, June 21, 2023

Neighborhood Watch Needed for the Region

I had the pleasure of meting the late Senator, and former Major General, Jim Molan several times on defence discussion panels in Canberra (I get called in as the defence tech expert). While I did not agree with the Senator's politics, I respected his military experience, and patriotism. Part of his legacy is the book "Danger On Our Doorstep" (HarperCollins, 2022), warning of the potential for war between Australia and China.