Electric Vehicles etc

I understand that, The issue is that solar & batteries operate in DC, our appliances in AC.

The battery makes more sense to be downstream (inside) the house power, not connected to solar, as explained in the video.

Is there another way?
 
But it can't and anyway like 12V fridges you are better off wasting your losses with the higher quality power source. It makes no sense to go DC - AC - AC - DC. The US east west interconnect is a hateful thing.
 
Dales Cannon said:
But it can't and anyway like 12V fridges you are better off wasting your losses with the higher quality power source. It makes no sense to go DC - AC - AC - DC. The US east west interconnect is a hateful thing.
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I think ultra high voltage DC is better for punching across distances. Although I remember reading somewhere the US has DC interconnects because the three grids run slightly different frequencies ...
 
Haakon said:
I think ultra high voltage DC is better for punching across distances. Although I remember reading somewhere the US has DC interconnects because the three grids run slightly different frequencies ...
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HVDC is more efficient (if by efficient you mean less transmission losses) on the same transmission infrastructure, but none of this is relevant to a Tesla power wall.

Each time you convert between DC or AC or different voltages of DC-DC or AC-AC you will get losses. A power efficient system will aim to minimise those losses. This is why if you go totally off grid, you run as much stuff as possible on DC directly off the batteries. Any time you use an inverter to get 240V AC you are wasting a lot of energy (at least 10% and possibly >50% if you are running the inverter in its least efficient part of the power curve).
 
I have no idea what I'm learning here.

Is there a product available for home use that doesn't have heavy transformation losses?

And are transformation losses the end of the world?
 
Ok, there are a lot of issues with DC. For one it is less safe. DC high voltage jumps a long way. You need inverters and rectifiers not just transformers. Switch gear is bigger and heavier and more prone to failure. AC switches self extinguish because the current reverses 50 times a second. DC does not and will jump a breaker. Google some of the videos of people opening DC breakers on solar systems before shutting down the inverter. Even good quality breakers last 5 or 6 cycles before they are rubbish. The DC interconnect in the US is because one grid is 50Hz and the other is 60Hz. I visited the station where the interconnect lives. Massive maintenance costs etc. The station staff hates it.

There are other reasons for DC interconnects like under sea transmission etc but unless it is simply point to point the costs associated with infrastructure mid line and the risks mean it is less than ideal even if the efficiency is potentially higher.

Transformers and rectifiers and inverters all lose some power. Nothing is free. Like solar inverters it depends what you buy and how well it perfoms. Sometimes the losses are small, sometimes they are significant.

I do not know what voltage any of the battery banks operate at but it is likely the solar is coupled into 400V DC lines or thereabouts. If the batteries could take that 400V directly into the charging system then you wouldn't have the losses with the other equipment and then have a single high quality inverter to provide ac out of the DC system.

Batteries have come a looooong way. When I built 18 years ago I wanted to go off grid because of the length of power line I needed. But it didn't work out economically. I still needed a back up. Now the equation is closer and soon it will be the norm to install battery packs with solar and wind turbine installations. I want to fit a grid isolator and have solar / wind providing the bulk of my needs but I need storage.

Formula E has made huge progress in their batteries and this flows into F1. It is coming.
 
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hifiandmtb said:
And are transformation losses the end of the world?
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I don't think they're the end of the world but they do impact the financial viability of the product. When I looked at the first gen Tesla powerwall I needed the batteries to last for 15 years to break even and there was no guarantee that they would last that long based on what I would need the battery to do (I would need the battery to handle a full charge/discharge cycle every day). The new product has double the capacity so maybe it will break even in 7.5 years, but if say the double conversion makes it 15% less efficient then that pushes the break-even point out another year or so.

But of course, you don't just want to break even...
 
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