So solar panels produce DC current, no conversion actually happens when sunlight is generated as electricity.
The DC current is then converted to AC as it is efficient in the electrical grid for long distances. However it is also used at home and majority of devices (hardly at least) don’t use AC as it gets converted to a safer DC current. This is especially important for electronics and battery recharging. When conversion happens, majority of that energy is lost as heat which you would find in the charging brick. In addition, with smartphones and EVs, wouldn’t direct DC be more efficient and quicker to charge than converting it back to DC. [Proponents claim that it would be beneficial if buildings had a ‘AC-DC converter box’ near a switchboard.](https://www.youtube.com/watch?v=hF_A4sp7nM8) (should mention that this is not a very credible source but others also claim similar stuff with DC)
So as I said before, why is AC forced as the current for homes instead of direct DC. Only current that needs to be exported to the grid would benefit from AC conversion. I couldn’t really see any answer to this with solar on mind. They will say AC is used for powering things while the other sites claim that AC burn devices if used.
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The problem is that all devices are designed with AC outlets in mind. They all need a different DC voltage, so they have a circuit that transforms the standard AC voltage of your country to the DC voltage the device needs.
Now if you’d want to directly use the DC your PV provided then you’d need a DC/DC converter (that sets the correct voltage) for each of your devices that bypasses the AC/DC converter.
Now if we all agree that DC power outlets should be a thing (in addition to AC, wich is still better for everything with a bigger motor) then we could agree on a few voltage levels, and then new devices could support that standard.
So in the end it’s all about inertia. Existing AC devices prevent people from switching.
Also with todays technology DC would actually be better for long distance transport of energy (you avoid EM radiation losses). The issue is that our current system was built for AC, and switching out all at once would be extremely expensive. AC was used because until the 90s DC/DC converters that could handle the necessary powerlevels didn’t exist, while AC/AC voltage converters are easy to build.
>When conversion happens, majority of that energy is lost as heat
No, you lose about 1% of the energy during conversion (with modern devices)
>So solar panels produce DC current, no conversion actually happens when sunlight is generated as electricity.
>The DC current is then converted to AC as it is efficient in the electrical grid for long distances. However it is also used at home and majority of devices (hardly at least) don’t use AC as it gets converted to a safer DC current. This is especially important for electronics and battery recharging. When conversion happens, majority of that energy is lost as heat which you would find in the charging brick. In addition, with smartphones and EVs, wouldn’t direct DC be more efficient and quicker to charge than converting it back to DC. Proponents claim that it would be beneficial if buildings had a ‘AC-DC converter box’ near a switchboard. (should mention that this is not a very credible source but others also claim similar stuff with DC)
>So as I said before, why is AC forced as the current for homes instead of direct DC. Only current that needs to be exported to the grid would benefit from AC conversion. I couldn’t really see any answer to this with solar on mind. They will say AC is used for powering things while the other sites claim that AC burn devices if used.
You can absolutely add a separate DC grid at, for example, 12V or 24V or 48V to your home. If you have enough devices that could benefit from that it makes total sense! It’s quite often the case with island solutions in, for example, a toolshed or similar.
But is that the case? Do you have enough devices that could readily use DC? Or would you have to suddenly replace or modify 200 different power supplies in your house just to save on pennies in conversion inefficiencies? If you’re not feeding your surplus into the grid you wouldn’t save anything anyway, you’d just have a slightly more efficient system, provided you utilize your whole output.
What kind of plugs would you use? AC power supplies are already standardized, no real risk of frying any equipment.
A power inverter modifies DC power to AC power. AC power is what the power grid uses. Without the inverter, the solar panels are essentially useless on the power grid
The DC voltage from panels varies widely. Often installations have multiple strings of panels feeding the same inverter and each strip can have a different number of panels facing in different directions and so having different voltages. You need a device like an inverter to get a single usable output standard. Otherwise you have to design a complex power supply into every electrical device in the house.
So given you need a device between the panels and the house circuits, it may as well output the same AC standard power we’ve been using for decades. Conversion these days is very efficient and any difference between outputting AC vs DC is going to be negligible. And who wants to throw away all their existing AC appliances to attempt to replace them with new DC ones of which there’ll be, at best, a very limited selection.
Also, switching high power DC can be a problem because it’s never at zero. You can get sustained arcing at the switches when you turn them off. With AC the arc stops quickly as the voltage crosses through zero. If you have an inverter, turn off the AC isolation switch first before the DC.
Solar power (DC) is cheap. Grid power (AC) is expensive. Converting from AC to DC or from DC to AC wastes some amount of power.
**Do you choose to waste cheap solar power to produce AC, or do you choose to waste expensive grid power to produce DC?**
If you have AC appliances, you need to invert to AC to power them which wastes some cheap, solar power.
If you have DC appliances, you need to be able to produce and store enough DC power to operate them. That requires a lot of expensive batteries. Or, you need to convert grid power to DC. That wastes expensive grid power.
If you do have enough capacity to store enough power under average conditions, you will have an excess of power during great conditions, and you’ll need the inverter anyway, to export that excess to the grid.
>However it is also used at home and majority of devices (hardly at least) don’t use AC as it gets converted to a safer DC current.
The majority of devices *by count* use lower voltage DC, but the vast vast majority of devices by *power draw* use AC
Electric stoves, ovens, dishwashers, clothes washers, electric driers, fans, air conditioners, and pumps are all built with AC motors and with heating elements sized for the right AC voltage.
You’d also run into the problem of *which* DC voltage do you send around your house? 5V? 9V? 12V? 24V? 170VDC to replicate peak of line? The losses are mostly in stepping between voltages not in the conversion from AC to DC. If you’re running 24VDC it is safer but you need *thiccc* wires to pass any significant amount of power(800W for a PC would require 8AWG wire!), and if you’re running 170VDC its actually significantly more dangerous and fuses/breakers won’t stop the arc so you have no fault protection
>When conversion happens, majority of that energy is lost as heat which you would find in the charging brick.
This is also wildly outdated knowledge. Solar inverters can be >95% efficient at their conversions. The bigger it is the higher the efficiency. Even small USB power bricks are all using flybacks now and are >80%. A 10W USB power brick might consume 12W of power at full load but a big 50W brick is probably less than 60W because again more space means more room for efficient parts
Ok first off DC isn’t “safer” than AC, just because Edison was an ahole and electrocuted Topsy the elephant doesn’t mean what he said was true. 9 volt DC can kill you just as dead. And the “majority of that energy is lost as heat” is also untrue, acdc rectifiers are 90% + efficient.
As for why you home is AC and will continue to be AC is transformers. You phone charges off 5v DC your electric oven isn’t going to cook to well on a 5v supply. For as long as homes have appliances that opperate at different voltages you’ll need transformers and transformers don’t work on DC.
A DC house supply would need rectifier transformer rectifier to power anything that doesn’t opperate at the voltage of the socket. And if you’re rectifying it anyway why not just have one.
A 12V 100A DC cable is a chunk thicker than a normal mains cable, despite not being able to carry the same amount of power (volts x amps) as one.
The higher the voltage, the more power you can carry on a thinner cable. So 110/220V around the home means I can – in my country – pull 3.5KW in a cable that isn’t even as thick as the one that comes from a single 150W solar panel.
You don’t want to see how thick a cable has to be to connect to any substantial battery bank for DC. Nor how short you need to keep it to stop it overheating or having too much voltage drop.
So transforming to high voltage is certainly something you want to be doing.
DC vs AC, however, is less clear.
Because you want to transform the voltage (from 12 to 110/220V), it’s actually easier to do that with AC than with DC. And if you want to transmit it any significant distance – even around a home – AC has less loss.
AC is far easier to generate for mains supply because you can use a rotating device to translate really well to AC. Hence even a wind turbine will be better suited to AC than DC in a small home system. Solar is relatively unusual in being DC generating.
Thus solar generating low-power DC is actually the oddball and subject to problems. Thus the very first thing we want to do with it is turn it into high-voltage AC. And that’s what inverters do.
The fact that “AC battery storage” isn’t really a thing also means that battery banks tend to be DC.
So it’s better to have all the low-voltage DC generation/storage in one place, convert that up to high voltage AC as best and as soon as you can, and then use that for EVERYTHING else (i.e. your entire home). EVEN if that means transforming it back down to low-voltage DC (like a USB plug). The losses in those kinds of low power situations aren’t worth worrying about. But when you turn on your high power electric heater or cooker, on the opposite side of the house to the solar battery bank, you’ll want to do it with high-voltage AC for as much of that distance as possible. Because the losses are the same as the above example, in terms of percentage, but the power FAR higher (meaning the overall losses would be far higher).
It’s almost like people sat and worked this out over hundreds of years and arrived at the best compromise all round – low voltage DC is transformed to high voltage AC when going any distance, high-voltage AC is transformed to very high voltage AC when joining towns or crossing the country, and then in the home if we need to we get it all back down to low-power DC for some small, low-power applications but otherwise use high-voltage AC for anything that pulls serious amounts of power (cookers, heaters, etc.).
Those big wall plugs that power your appliances from the mains – they are converting from high voltage AC back down to low voltage DC at the VERY LAST MOMENT before you put them in an appliance. Because that’s the most efficient way to do that.
It means your home has dozens of AC->DC convertors in it, whether you realise it or not. You could say “why not just run 12V / 5V DC around your home… same reasons. It’s actually simpler, cheaper, easier and less loss to run everything on AC and then down-convertor and transform to DC at the very last minute than try to deal in entirely DC cabling and circuits unnecessarily.
In my (rather primitive) home solar panel setup, the leads between my batteries and my inverter are 20cm long and about 1cm thick copper. They get warm if I pull a lot of power.
The leads from the inverter to everything else are 220V AC, and they are just bog-standard ordinary mains leads (so barely a few mm thick copper each) and I can use them at the other end of a very long extension cable if I so wish, or run a high-power heater off them without them getting warm.
Very little of your DC devices use much power and they do not in fact lose much efficiency from heat but rather the fact that the electric has to be manipulated to get from 48vdc to 120vac and back perhaps perhaps 12vdc or 5vdc or the current USB-C standard of 20vdc like small things.
AC power is a manmade construct and is difficult to manipulate.
Most of the power you use has to be high volt like refrigerators. Whereas a phone can charge on ten watts, a 55″ TV three hundred fifty, a coffee maker, vacuum cleaner or your mom’s vibrator can use eleven hundred and an air conditioner double this.
We will likely eventually switch to something more like the outlets you see with USB-C ports in them, and have a secondary 20vdc system in tandem with the 120vac we currently use.
Still, it makes little use of the solar panel. My little 1800 watt gas powered generator can power every light, computer, phone, and even the well pump if I bend physics a bit but it can’t run major appliances like a dishwasher unless I devote 100% of it’s power to it alone.
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