Share →


I’ve been working furiously this week on a 48v battery module and controller to work with the Sunny Island 6048 US Inverter. Coming nicely I think. This will be a good combo.

But there is a kind of identity crisis between the Sunny Island and the grid-tied Sunny Boy. In Germany, where they are made, it is actually illegal to use them together. And it’s all about the grid.

Here in the U.S. too, there is an identity crisis that spans ALL the vendors of solar equipment. And it is ALL about the grid. People want their solar systems to be tied to the grid. In this way, if they need more electricity than their solar system provides, they can get it from the grid. And if they produce more at any particular moment beyond their needs, they can “sell” it back to the grid.

But if the grid goes out, they want it to provide electricity to their home. And there in lies the rub. If you are connected to the grid, you wind up powering the grid. And that can be bad.

So the vendors try to be all things to all people. And they try to come up with ways that will be “legal” and tie to the grid politely, but also be useful stand alone or as a backup system.

So you have:

1. Off grid systems.
2. Grid tied systems.
3. Backup systems.

Now since they all use similar equipment, why can’t somebody just come up with a way to do all of that in one box. Which is kinda/sorta what the Tesla powerwall purports to do.

Worse, the regulations vary from grid to grid and provider to provider.

Coloring all this is a huge backdrop of schizophrenic activity over what the role of the grid should be and what the role of the homeowner whom we are trying to incentivize to install solar.

In 2009 I predicted that we would no sooner free ourselves of the oil companies, than our pals the electric companies who were oh so enthusiastic and encouraging about electric cars would become the new arch enemy. And it has come to pass. Trading one master for another.

In a Pollyanna perfect world, we could of course build a very distributed network on a national scale and power could shunt from area to area as the sun did shine, and local outages could be made up with local rooftop resources and all would be happy. Meanwhile our dear friends at the utility company are doing horrendously cynical backroom deals with “regulators” all too willing to sell out their neighbors for the right amount of cash. Actually any amount will do.

The case in Florida where a constitutional amendment guaranteeing the right to install solar, which was actually a constitutional amendment assuring utility companies that no one could install solar, was so cynically and deliberately designed that it would do the Democratic National Committee proud. With millions spent by the utility companies to advertise and promote this “rights” movement, it did gain a majority of votes. But that was not enough to pass an amendment and so the deliberately fraudulent ruse was defeated. The author gleefully described it as brilliant political ju-jitsu – that is before it failed and when they thought it would probably pass.

This scenario is currently ramping up across the land and it is now a cottage consultant industry to advise utility companies on specifically how to defeat the desires of their “solar” customers. The self-centered world view of these people is frightening in both its scope and stupidity. But we saw it with the telephone companies over the Internet, the oil companies over the electric cars, and now the utility companies with solar. It is encouraging to note that in the end they ALWAYS lose. But the war can be nasty. And this one shapes up to be.

I’m entirely about empowering individuals at the expense of the large corporations and the state. In this case what I see as the solution is to MOSTLY cut the cord.

The idea of selling electricity from your home back into the grid is great. But in practice it isn’t. IF there is an artificial bonus in it in the form of a Feed In Tarriff, that’s nice. But for most of us, we get paid on a new device of the utility industry called “avoided cost of production” which ignores the realities of a “market” for electricity and goes to a theoretical cost of coal by the ton. In actual practice, for natural gas microturbines acting as load feeders, they pay a PREMIUM over market rates for electricity need during times of extreme demand. But here in Missouri the “avoided cost” is a laughable 1.75 cents per kWh. So in summer you buy at 10 cents, which with taxes is actually 12 cents, and sell at 1.75 cents. When I grow up, I want to be a monopoly. Actually I want to be a government, but like the utility companies, I would settle for just being a monopoly.

The cost of equipment and panels to do solar has come down. But it leaves the idea of building excess generating capacity so you can profit from sales to the utility company actually ludicrous in most cases. And if there IS a way to find a seam in the zone, trust that the utilities will move swiftly to close it.

What I would propose is a bit different type of solar system I term “Selfish Solar”. This is a solar system you build for you and your house. It IS connected to the grid. But kind of as a backstop/supplement. We would use the grid if necessary. But we never give or sell back to it. And the concept is to pay the monthly minimum connection fee and not use any of their electricity at all.

If they go down, we don’t want to worry about disconnection issues any more than someone running an electric dryer does now. It just goes down. And our system continues to power our home for hours, days, weeks or forever. If we are little missized, we might use a little bit from the grid, and there are indeed some winters where a week or two of overcast will probably put us in a deficit. So the connection is “valuable”. But we want it to appear to the utility companies as a normal connection, with no trick meter, and no opportunities to pass legislation “fixing” us. A standard 200 amp service panel with no trick anything. In fact, it only runs ONE device. A battery charger.

In the EV community we already know about battery chargers. We can use one, two, or three Chevy Volt battery chargers to produce up to 420vdc. Or, if Jack would get back on task, a single Tesla battery charger will convert 240vac to 400vdc all day long at a smooth 10kw. Actually Tesla now has a 17kW charger in the newer models.

And that is the ONLY connection TO the grid. It runs a simple switched power supply to convert 240vac grid power to 400vdc battery charging power and it has two basic states, on and off. By the way, if the grid goes down, it is off.

All of this DOES require a battery of course. Indeed, let’s stop looking at the battery as an adjunct to a solar system. Let’s mentally get over it and realize that the battery is the HEART of a home power system. We can use the grid, generators, or solar arrays to put energy INTO it and we use an inverter to convert its output to the familiar 240vac to take energy OUT of it.

Electric vehicles, and Tesla most notably, have batteries that start at 300vdc on the empty side, and reach nearly 400vdc on the full side. This is actually a very good operating range for houses in that 240vac is the object of our desire. If you rectify 240vac and feed it into a large capacitor it will charge to the peak voltage of the input 240vac x 1.41 or 340vdc. And of course to EFFICIENTLY generate 240vac, you really need a power supply that is very near to the peak voltage of 340vdc. We would FULLY charge a Tesla pack to 403vdc.

To efficiently charge this 300-400vdc battery bus from solar, we need a maximum power point power supply that takes the photovoltaic output of the panels and converts it to the battery charge voltage. Almost ALL MPPT charge controllers currently have a max PV voltage of 100 or 150 vdc and are sized for 12, 24, 36, or increasingly 48vdc batteries. At power levels, this gives us huge bulky awkward and very expensive cables.

Eight of our Panasonic HIT panels produce 480vdc in full sunlight. This would be ideal for stepping down very efficiently to our 300-400vdc range. But most MPPT controllers don’t do it, and the one we DID find is kind of weeny at 3000 watts. So we have gone to China and asked them to specifically build us one for the Tesla battery pack. 37 kw and hard wired to charge the battery to 400 vdc. It will do up to 100 amps.

And that leaves us with the inverter. Again MOST of them operate off of 48vdc. So we have again gone to China to get them to build us a special 20kW inverter that works off 300-400dc and produces 240vac output.

And that leaves charging your car. ANd we already have a CHAdeMO charger that runs off a battery input of 300-400vdc.

So the needed utility is to center on a common bus of 300-400vdc, and have everything interact with that.

Let me estimate the retail cost of what the famously expensive EVTV would want for all this.

1. 10 kW Tesla charger and controller – $3,000
2. MPTT 37 kw 400 vdc charge controller – $2,000
3. 20 kw array of 64 Panasonic HIT panels – $20,000
4. Tesla 85 kw battery pack $15,000
5. Battery pack controller $2,000
6. 20 kw 400vdc to 240vac Inverter $10,000
7. CHAdeMO Charger $23,000

That looks like $52,000 without my CHAdeMO charge station. On a sunny day of 4.5 hours, this should make about 90kWh solar. We can store 85kWh. And the average American home uses about 31kWh per day. So 2.5 days storage.

The $52,000 is expensive. But it is expensive like an expensive car. And you are your own utility. Freedom. If you can afford all that, you might just have a home LARGER than the Average American home. So you add 8 panel strings until your utility bill goes to connection fee. Sizing is pretty easy here. Overkill is always appropriate.

What about when your house makes more electricity than you can use or store? Unlike the utility company, we can turn our plant off instantly. Just shut down the MPPT controller automatically when the battery gets full. You suffer the crime of having energy fall on your panels that you cannot use. Be selfish about it. Who cares?

The “response” from the utility companies will of course be to raise the minimum monthly “connection fee” and they already attempted this in Utah and Arizona proposing $150 per month as a minimum. I think the legislature gave em $5 but hey, its a start. Kind of like a two drink minimum at a lap-dance stripper bar. And from the same sort of people. At the point where you don’t want to pay it, tell em to pick up their meter and then describe for them in detail where you would like it inserted for storage purposes.

This then is how I see individuals successfully fighting this battle. As always, it will be for those with the resources to be early adopters. But I think the days of a “little bit of solar” adding a 5kw system to the roof are rapidly coming to a close and you are going to have to choose between the grid and the grid-not. Fortunately, the electric vehicles give us the tools to perform this act with dispatch. As more EVs show up, and as more people move to a 400v bus compatible with the car batteries, I think all of this gets cheaper. In five to eight years, probably that entire system will be doable in the $20k range.

And so I would advocate not worrying about grid tie and indeed not view your home as contributing power to the grid and system. It’s yours, to use or waste as you like.

I think industry and commercial installations will follow this same logic to the same conclusion. And the greed of the electric utilities will ultimately be their downfall. ALL the great corporations of the past have gone the same way. It wasn’t the disruptive technology that got them. It was the hubris and the failure to adapt.

If they embraced the technology, helped people finance and install grid sharing solar systems and taken the same 30% markup everyone in the world deals with in everything, or even the 3% markup of the grocery store, they would have done fine and we would have a marvelously flexible and intelligent national grid. They would make a fortune just billing and paying people and clearing the economics of the market, and acting as tax collector for the government. They could even be in the solar equipment business. Instead, they will be selling off their office furniture at 6 cents on the dollar. Bucket trucks will be $1000 apiece. And the huge tax revenues generated currently will dry up like leaves autumn. Oh well. It is ever so.

For individuals, the selfish solar system is the future. EV components will power it. And for the present, it will be very very modular – the all-in-one boxes trying to be all things to all people will not make it.

Jack Rickard