Mostly Inverters or Lots of DC Too

[jmellc]

I tried several years ago to stay abreast of solar progress, but have let it slide a lot. The few materials I used to find indicated a lot of DC lights & appliances. A lot of what I read here indicates inverters for AC as end use product. Some battery chargers carry labels warning not to power them from inverters. Are inverters overcoming their flaws in that area?

Are most systems now geared for AC? How much DC does anyone install now? How hard is it to find lights/appliances for DC?

 

[jaggedben]

The vast majority of new solar systems going in right now are grid-interactive with only AC utilization. Most systems do not have battery backup. DC only systems are extremely rare in buildings, and off-grid systems are a tiny section of the market.

Some battery chargers carry labels warning not to power them from inverters. Are inverters overcoming their flaws in that area?

I guess I would say yes; I'm not sure what kind of setup would lead to such a problem nowadays.

First, a grid-interactive inverter can power anything that the grid can.

Second, if you are setting up a system with batteries, you hook up the batteries and the solar panels (through a charge controller) in parallel to the inverter. There are now numerous products that provide all of the above in an integrated package.

How hard is it to find lights/appliances for DC?

I don't think it's any easier than it used to be (except that the internet may make it easier to find anything nowadays). Which is to say, they exist but there's not much selection.

 

[jaggedben]

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[ron]

How hard is it to find lights/appliances for DC?

For lights, it will depend on the voltage you are working with. 12V is readily available from RV (motor home) vendors and 120V can use regular lamps, 120VAC is similar to 120VDC since 120VAC is a RMS value.

 

[Marvin_Hamon]

In the old days most inverters did not output a true sine wave. This would cause problems with power electronics plugged into off-grid systems, most notably PC printers if I remember right. It's still possible to buy small cheap 12V inverters that do not output a true sine wave so the problem still exists. Most larger inverters used in off-grid installations through are putting out cleaner power than some utilities.

It would be more efficient to have most things running on DC if generation was local. AC is, for the most part, helpful to the transmission and distribution of power over longer distances. But you will find that due to the small market DC lights and appliances are harder to find and have much less to choose from than with AC. DC consumer devices are almost always not as well made and are more expensive than the AC counterparts. If they are well made they are much more expensive. This is why inverters are considered the standard for off-grid installations.

 

[CA Contractor & Builder]

Where is Professor Telsa when you need him!

 

[BillK-AZ]

He never solved the problem of how to charge for wireless power.

 

[jmellc]

In the old days most inverters did not output a true sine wave. This would cause problems with power electronics plugged into off-grid systems, most notably PC printers if I remember right. It's still possible to buy small cheap 12V inverters that do not output a true sine wave so the problem still exists. Most larger inverters used in off-grid installations through are putting out cleaner power than some utilities.

It would be more efficient to have most things running on DC if generation was local. AC is, for the most part, helpful to the transmission and distribution of power over longer distances. But you will find that due to the small market DC lights and appliances are harder to find and have much less to choose from than with AC. DC consumer devices are almost always not as well made and are more expensive than the AC counterparts. If they are well made they are much more expensive. This is why inverters are considered the standard for off-grid installations.

I sometimes use an inverter from my truck battery. I plugged in a battery charger & ruined it. Later, I saw the warning tag not to use on an inverter, duh. I should have known better.

 

[jmellc]

I saw on another forum that the cost of PV power has come down a lot the past 1-2 years & for remote locations is now cheaper than bringing in grip power. Does that ring true with you EC's that install PV systems?

 

[ggunn]

I saw on another forum that the cost of PV power has come down a lot the past 1-2 years & for remote locations is now cheaper than bringing in grip power. Does that ring true with you EC's that install PV systems?

Yes, the cost of PV has definitely come down a lot in the past couple of years, but there really are two worlds of solar electric power - grid tied and off grid.

Grid tied is much cheaper to implement because it only involves PV modules and inverters, and the prices of these components has been dropping steadily as more manufacturing comes on line. In some locations, power from distributed PV generation is becoming competitive in cost to grid power.

Off grid is really a different kettle of fish because off grid operation must include energy storage, which means batteries, and the cost of batteries has not been coming down, it's been going up because of the metals involved. Batteries are the single most expensive part of an off grid system and may cost 2X or 3X (or more) what the rest of the system costs, which makes off grid power cost something like 10X what grid power costs. The determining factor of whether off grid power is worth the expenditure is the cost of grid interconnection. If you build a remote cabin even a relatively short distance from the nearest grid connection point, the cost to run conductors out to you may be hundreds of thousands of dollars, and that's before you pay the first electric bill. The more remote you are the more the interconnection costs, so it can get economically feasible, relatively speaking, to build an off grid system when you are remote. Obviously, it's hideously expensive either way, so most off grid systems are small. Owners of cabins "out in the sticks" are notorious for their miserly ways when it comes to energy consumption.

 

[jmellc]

Off grid, very remote location was specifically what I had read about. It would have cost a fortune to extend power from grid. In his case, looks like self contained was the way to go. See the survival tech page from Survivaltopics.com forum, heading "Got to visit another off-grid home".

I applaud anyone who has the means to do this, if the equipment holds up reasonable well. I've never seen grid power get cheaper & I'm sure future rates will be much higher than today.

I looked into solar a few times. Once ordered a Brinkmann double flood with solar panel for my house. It was a dud. A local lighting dealer said he'd carried some stuff, but had problems with all of it. The stuff at big box stores doesn't look that good either. I found websites for a couple of seemingly good producers, but they were cross country from me. They mostly made parking lot/street lights, etc. with collector & battery pack on pole, near light.

I visited a solar dealer that came to town, told him I wanted to learn solar. He said he had contractors already. Don't know if he is still here or not.

 

[Marvin_Hamon]

When bringing in grid power is over $100,000 and a 10kW off grid system is $90,000 then maybe going off grid is cheaper, but it's still $90,000 plus periodic replacement of the expensive battery bank. There are many factors involved.

 

[ggunn]

When bringing in grid power is over $100,000 and a 10kW off grid system is $90,000 then maybe going off grid is cheaper, but it's still $90,000 plus periodic replacement of the expensive battery bank. There are many factors involved.

$90k is a pretty good price for a turnkey 10kW off grid PV system with adequate batteries, actually.

Most offgridders have much smaller systems than that and live a very energy frugal lifestyle; you don't see many of them with large floorplans and full central air and heat. If you find one, best keep your distance; he is probably heavily defended and easily alarmed. ;^)