This is a good idea for grid stability. People switch on electric clothes dryers all the time or air conditioners in the summer.

You would not use them for load shifting since the heavy usage would accelerate the decline of the batteries, but for grid stabilization applications they are perfect, a 100kw load for a couple of minutes will not use much of the capacity life left in the battery. A couple of minutes is more than plenty for spinning reserve to step in.

I like the idea of used Li-Ion car batteries for renewable storage. A $5,000 photovoltaic array, including batteries, can supply all the energy (10kwh/day) a BEV needs in United States (except on cloudy days). However, the PV array collects photons during the day when the vehicle is not available for charging. So you need batteries to store the 10 kwhs of solar energy, which will be used to charge the car at night.

This will probably have widespread use because the cost of PV arrays has plummeted and continues to fall and the energy is free. However, lead acid deep-discharge batteries cost only $100 per kwh. Will used Li-Ion batteries be cost effective for storing PV energy? Maybe it will be better to just recycle them.

It's not cheaper to move it to the grid. To transfer PV energy to the grid, you need an expensive inverter. For a home PV system, 10 kwhs of Pb-acid batteries cost about $1,000. A grid tie inverter is more. With battery storage, you can charge the car batteries with DC. So you don't need the charger inverter either. I don't see how battery storage is less efficient for a home PV system. Inverters aren't 100% efficient.

Widespread use of home PV charging systems will also remove a lot of concern about grid supply, demand, improvements, substations, transformer overloading, etc. And most people would love to generate their own power independent from power company regulations and bills. Apartments dwellers can't put up a 10 kwh/day PV array, so their demand will still affect grid infrustructure.

Running appliances isn't part of the deal, if the PV system only produces 10 kwhs/day. That's enough for 30-40 miles of driving. Home battery storage also provides energy when it's needed, which is when people get home from work in the early evening. At that time, the PV output is gone and the grid is overloaded with air-conditioning demand. If the home batteries are charged up, the car batteries can be charged immediately. There is no need to wait until the rates go down at 10-11 PM, as with a grid-tie system. Again, such a home PV storage system reduces the need to redesign the grid infrastructure.

The fight between centralized e-energy production and decentralized customer orientated systems has just started.

Owners of centralized systems do not want competition from individual systems and they will do everything they can to stop it. They have deep pockets and will use their $$$ to pressure current and future politicians to lean in their favor. What is good for the Nation is not good for them. Who will win? In our free enterprise democracy, they will win.

Individual (home) production is currently much more expensive. Surpluses and shortages are expensive to manage efficiently. Using the existing grid via an inverter and 2-way meter is certainly less costly and more efficient for both. Here again, will grid operators and large producers cooperate? They will ask to be compensated. Making PHEV/BEV available for peaks may be an acceptable compensation? Nothing is free.

Running appliances isn't part of the deal was defined by me in my original argument.

I'm talking about a PV system used only for recharging batteries.

Grid-tie inverters are expensive because they need to have very accurate 60 Hz operation, require a lot of mechanical assembly, carefully wound coils, and machined parts.

Your objections could only get more bogus if you invoked the phase of the moon or human sacrifice.

I was talking about energy being available to charge the car battery, not to run appliances. This is about convenience to the consumer and keeping the load off the grid.

From the POV of the grid, it makes more sense to use all available storage as buffers. This means it all needs to be on-line. Wheeling power across the grid from home PV to the car at work requires no new lines or transformers and allows the car to be used as a buffer all day (the difference between minimum required SOC and full charge is available buffer, and the car can be charged at any time before it's needed next). This eliminates one battery, one battery-management system, a DC-DC converter, and cuts a bunch of costs out of the grid (for regulation) for the cost of an inverter. Since inverters historically last longer than batteries, this is by far the sweeter deal.

What happens when rapidly falling PV prices result in 20-30% of homes have PVs and EVs? Without storage, the power company will have to buy a lot of power it can't use during the day. They will have to install coal and nuclear to meet increased demand in the evening.

Storage at the source removes grid-related issues like purchasing unusable PV energy, new power plants, transformer and substation upgrades, new transmission lines, fuel mining and distribution, CO2, for which consumers would have to pay anyway. The economics and cloudy day operation remain to be seen, but hopefully Duke and ITOCHU can explain this.

Either way you need either a new inverter or battery storage. That's the deal.

The grid-tie inverters have to match the output phase to the line

need maximum power-point tracking

and anti-islanding protection

This technology is obviously more complex thn an inverter supplied with a backup generator.

If the inverter has coils (not all do), aren't they machined parts?

I believe the grid-tie inverters are complex and require more labor to build than PV panels.

Transformers will be required because at the community level, recharging large numbers of car batteries will overload the existing local transformers. Most people won't be satisfied with trickle charging and they will want 60,000 watt chargers at home to charge in 5-10 minutes.

By law the producers have to pay the consumer for excess PV energy put back into the grid. I guess in the long run they can get the law changed and stop buying it. That doesn't help the PV industry much. And what will the homeowner do with the excess? This is another good reason to store it.

It's true that weather affects the output of PV. So if large numbers of people have PV, and the sun goes behind he clouds, load goes way up on the grid. This is the main reason storage is necessary if PV ever becomes a large segment of the grid.

For years the PURPA laws provided only "avoided cost" or payment for the utility's cost of production. It took decades for that to become more just. Events move slowly but at times grind in the right direction.