Renter installs solar on apartment building roof

[obstinate]

https://medium.com/@nikodunk/200-for-a-green-diy-self-sufficient-bedroom-that-your-landlord-wont-hate-b3b4cdcfb4f4

This was pretty cool. There are a number of caveats at the end of the article, but it is no doubt a Mustachian and clever solution to the problem of energy self-sufficiency.

[Plugra]

Community solar gardens are absolutely the solution to that problem.  Not legal in my state though :(

[bobechs]

Man crafts a system capable of making (perhaps)  a nickle's worth of electricity a day.

Enough to power a cellphone, laptop and an led desklamp.  Plus a 150Watt space heater.  That's the output of an incandescent bulb.

Declares that since the panel is dropped loose on the roof and the wires dangle free down the front of the building he's home free from any landlord or other interference.

Does not seem to be the sharpest tool in the electrician's toolbox.

[Kyle Schuant]

"My goal is to take care of the energy needs for just my bedroom."

I think he can achieve that goal. It's not his whole apartment, it's just his bedroom. Putting him down is much like putting down the 19yo who just put $100 in the bank: everyone has to start somewhere, and it is better to give it a go than not bother.

[obstinate]

Yes. This project would pay for itself simply in learning how to do it, without considering the payback period.

[Kyle Schuant]

The economics of it would be different in Australia, as electricity is about twice as much as in the article, about AUD0.30/kWh - and rising. So the financial payback period would be quicker, environmental is another and more complex question, of course.

[nawhite]

It is cool that he put it together but his return numbers are way too high both because he ignores efficiency losses and he doesn't depreciate his startup costs. If he depreciates everything over 8 years (very generous for the battery, about right for the inverter and charge controller, and an underestimate for the panel), at 100% efficiency his return is about 4%. The charge controller probably loses 8%, a wire run that long loses another 8%, the charge discharge round trip through the battery loses about 4% and the inverter probably loses about 15% (about 70% of the power out of the panel comes out of his inverter) Granted if he's running an electric heater then the heat loses don't matter as much but still.

You really need to scale up your components and your system as a whole to improve the efficiency. I have an off grid system in my RV and my losses are probably about 80% of panel out of inverter. (https://therecklesschoice.com/2016/04/29/diy-rv-solar/) Off-grid solar is expensive!

[robartsd]

It is cool that he put it together but his return numbers are way too high both because he ignores efficiency losses and he doesn't depreciate his startup costs. If he depreciates everything over 8 years (very generous for the battery, about right for the inverter and charge controller, and an underestimate for the panel), at 100% efficiency his return is about 4%. The charge controller probably loses 8%, a wire run that long loses another 8%, the charge discharge round trip through the battery loses about 4% and the inverter probably loses about 15% (about 70% of the power out of the panel comes out of his inverter) Granted if he's running an electric heater then the heat loses don't matter as much but still.

You really need to scale up your components and your system as a whole to improve the efficiency. I have an off grid system in my RV and my losses are probably about 80% of panel out of inverter. (https://therecklesschoice.com/2016/04/29/diy-rv-solar/) Off-grid solar is expensive!

None of the things he powers requires AC - leave out the inverter and cut losses in half!

[Plugra]

You really need to scale up your components and your system as a whole to improve the efficiency. I have an off grid system in my RV and my losses are probably about 80% of panel out of inverter. (https://therecklesschoice.com/2016/04/29/diy-rv-solar/) Off-grid solar is expensive!

I am currently getting rooftop solar for my house and it's a very close call whether it's a net savings.  Even with the most efficient hardware and net metering, the payback time will be 10-15 years if I'm lucky.  As for off-grid solar, well it's not about the money is it.  I think of it more as a harmless hobby for engineers and survivalists.

Anyone who just wants to save money on electricity might want to forget about solar. Maybe they should vacuum the coils under their refrigerator instead.

[Kyle Schuant]

None of the things he powers requires AC - leave out the inverter and cut losses in half!

I have often wondered if houses and more appliances will start going DC. Looking at my own house, the only AC things are all the high-current things like fridge and oven and airconditioning. The ceiling LEDs, the laptop, tv and so on are all DC.

I understand why houses originally had AC, but things are changing now.

[nawhite]

None of the things he powers requires AC - leave out the inverter and cut losses in half!

I have often wondered if houses and more appliances will start going DC. Looking at my own house, the only AC things are all the high-current things like fridge and oven and airconditioning. The ceiling LEDs, the laptop, tv and so on are all DC.

I understand why houses originally had AC, but things are changing now.

The reason we don't usually wire houses for DC is that DC has huge losses at low voltages unless you have huge wires. 50 feet of 14 gauge wire @ 12V and 5 amps (about what a laptop draws) gives you a 10.5% loss. So one way or another, you end up with AC-DC converters distributed throughout the home to minimize cable lengths. You also don't get more efficient converters by making them bigger or hardwired so there isn't any benefit vs just having a converter at the plug (i.e. a power block).

[robartsd]

None of the things he powers requires AC - leave out the inverter and cut losses in half!

I have often wondered if houses and more appliances will start going DC. Looking at my own house, the only AC things are all the high-current things like fridge and oven and airconditioning. The ceiling LEDs, the laptop, tv and so on are all DC.

I understand why houses originally had AC, but things are changing now.

AC is great for power distribution because step-up transformers are very useful for efficient long-distance transmission.

It would be relatively simple to distribute 24 to 48 VDC arround a home to power electronics. The electrical code allows quite a bit more flexibility for low-voltage (>50V IIRC) applications than allowed for line voltage. Power supplies for electronics generally rectify AC into DC then switch on and off rapidly to control output (with inductors and capacitors to smooth things out) - with a DC supply, you just eliminate the rectifier.

I think the biggest obstacle to DC microgrids within homes is the lack of interconnecting standards appropriate for powering small appliances. Current de-facto standards are the auto 12V assessory port (possibly OK for up to 120W, but not great at making reliable connections) and the 5V USB port (up to 25W) as de-facto standards. A new consumer standard supplying 24-48 VDC with connectors rated 10-20 amps is needed. This would allow pretty much any home appliance outside the kitchen to be powered by DC.

[robartsd]

The reason we don't usually wire houses for DC is that DC has huge losses at low voltages unless you have huge wires. 50 feet of 14 gauge wire @ 12V and 5 amps (about what a laptop draws) gives you a 10.5% loss. So one way or another, you end up with AC-DC converters distributed throughout the home to minimize cable lengths. You also don't get more efficient converters by making them bigger or hardwired so there isn't any benefit vs just having a converter at the plug (i.e. a power block).

You're right that it make no sense to use a DC microgrid supplied only by utility power. Each device will still need a power supply that reduces and regulates the voltage. It does start to make sense when you are interested in battery backup or local renewable energy sources because you can eliminate the inverter losses. Transmission losses are aproximately proportional to the inverse of voltage squared (doubling voltage transmits the same power with about 1/4 of the lost). Converting to higher voltages is easier using AC than DC making AC preferred for utility transmission.

Using your example of a 60W laptop supplied over 50' of 14 guage wire, the loss would be less than one percent if the supply was 48VDC (still several times the loss for transmitting 60W @ 120 VAC over the same wire).

[Plugra]

Inverters are not necessarily so inefficient. They can certainly exceed 95+% efficiency.  Batteries are a bigger problem. Even if you are lucky enough to have a battery that recovers >95% of your energy, it's not going to have a 20-25 year useful life and that means extra cost. 

I don't know why people other than campers and hermits want off-grid solar. If you have grid access and net metering, then off-grid solar is an inefficient solution to a non-problem.

[robartsd]

If you have grid access and net metering, then off-grid solar is an inefficient solution to a non-problem.

Until you have the utility power go out for some reason.

Does the risk of power outage justify the costs of building and maintaining off-grid capabilities? Probably not for most circumstances. Anyone aware of someone doing an analysis of generator vs. an off-grid solar as a backup power source? I think in most cases a backup generator would make more sense - even if the building also has grid tied solar.

[nawhite]

If you have grid access and net metering, then off-grid solar is an inefficient solution to a non-problem.

Until you have the utility power go out for some reason.

Does the risk of power outage justify the costs of building and maintaining off-grid capabilities? Probably not for most circumstances. Anyone aware of someone doing an analysis of generator vs. an off-grid solar as a backup power source? I think in most cases a backup generator would make more sense - even if the building also has grid tied solar.

Backup generator wins by a landslide. The reason is that capital costs are so tiny with a generator comparatively. You can get a really nice generator that will power a whole house with no problems for $1000, then you'll spend about $2-10/hour for fuel and maintenance. A backup solar setup with enough storage to run a house overnight is going to cost you $2000 minimum. An inverter that can run off-grid is probably an extra $1000 vs an always grid tied one (not to mention that a grid tied one would be sized to your panels production, not to your home's max usage which will be much higher). And that's before you've even bought the solar panels.

[Prairie Stash]

Man crafts a system capable of making (perhaps)  a nickle's worth of electricity a day.

Enough to power a cellphone, laptop and an led desklamp.  Plus a 150Watt space heater.  That's the output of an incandescent bulb.

Declares that since the panel is dropped loose on the roof and the wires dangle free down the front of the building he's home free from any landlord or other interference.

Does not seem to be the sharpest tool in the electrician's toolbox.

Man writes a blog about it, makes a lot of money. Pays for it within hours of posting.

Might be sharper than you think, he got a free solar panel today. With the hits from this site, his traffic shot up.

[nawhite]

Man crafts a system capable of making (perhaps)  a nickle's worth of electricity a day.

Enough to power a cellphone, laptop and an led desklamp.  Plus a 150Watt space heater.  That's the output of an incandescent bulb.

Declares that since the panel is dropped loose on the roof and the wires dangle free down the front of the building he's home free from any landlord or other interference.

Does not seem to be the sharpest tool in the electrician's toolbox.

Man writes a blog about it, makes a lot of money. Pays for it within hours of posting.

Might be sharper than you think, he got a free solar panel today. With the hits from this site, his traffic shot up.

Lol, My comment on his site linking to my page above generated $5 of affiliate revenue. I'm sure he paid for his setup with that post.