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How to Get Your Apartment Off the Grid (lowtechmagazine.com)
201 points by hellrich on May 18, 2016 | hide | past | web | favorite | 138 comments

A bit of context: In Spain, one of the European countries with better sunlight for solar production, some laws were passed recently that make it basically impossible for individuals to resell excess energy to the grid, so selling/buying from the grid on demand instead of using batteries is not really an option.

That's why when we see countries like Germany (not so much sun) going strong for solar Spanish people complain and try to change a corrupt government that passes laws that strongly favors utility companies. Not to say that some of this government relatives work in these utilities.

Wouldn't it be possible to create micro grids? E.g. tenants of one house or small town. They could sell electricity to each other then.

> Y se añade "en ningún caso un generador se podrá conectar a la red interior de varios consumidores". Esta medida habría beneficiado a las comunidades de vecinos.

And it adds "under no circumstance a generator will be connected to the inner network of several consumers." This rule would have helped neighborhood communities.

Seems like you are quoting an article from El Páis and not directly the law itself.



5.2.B - En el caso de que existan varias instalaciones de producción, el titular de todas y cada una de ellas deberá ser la misma persona física o jurídica.

(In case there are several production facilities, the owner of all of them must be the same natural or legal person)

"Y se añade "en ningún caso un generador se podrá conectar a la red interior de varios consumidores". Esta medida habría beneficiado a las comunidades de vecinos."

Baterías y trabas burocráticas (right column):


I'm not arguing it's not quoted from the article, just providing a source to the original in case someone is interested.

I thought that was the purpose, but I think it is always important to quote the source of one's comment. :-)

The quoted part within the article, seems actually to be from, Artículo 4.3 (yes, very pedantic :-)

Thanks for the link!

Should this be interpreted that the tenants could just form a company that owns (or even rents?) the equipment and then have the company pay them rent for the locations?

Sorry, the Decreto Ley, like any other legal text is complex and needs careful interpretation. As a native speaker I can quickly locate (what I think is) the relevant section, but a detailed analysis would take a lot of time.

Anyway, I've followed these news for a while and heard the defense that the promoters of these measures did, so in case they were thinking in other interpretation they would have said so. It has been massively unpopular for the people that understand this issue at all, that are not many, and only was defended by the gov. party and the companies.

The industry minister, by the way, had to resign after he couldn't explain why his name was found in the Panama Papers as owner of offshore companies. And no, it wasn't a big deal, if you think the whole government has been under suspicion since the party treasurer was jailed four years ago for outright corruption and the prime minister Rajoy sent him a SMS telling him "to be strong". There are an acounting papers by the treasurer that show in detail how everyone in the party received monthly cash filled envelopes with money that came from building companies briberies.

Also the Valencia mayor is being investigated in another case that has every of her councillors formally accused already. You would think that the party would have her resigned. Instead they put her in a Senate commite to protect her.

This is the governing party, the one that, after all those smoking guns showed, still had the most votes last December and (after nobody could form a government) is expected to also win next month elections. So if you were thinking this Sun Tax, as it's commonly known, couldn't be so obviously corrupt, think again.

I'm not specially partisan, more of a "swinger voter", but the situation here has been disgusting for too much time. The worst of all is that many people's reaction has caused the rise of a party that is very close to Chávez and Maduro, actually there's strong suspicion that it was ilegally financed by Venezuela gov. party (Edit: and Iran!), so we could fall from the pan to the fire.

I totally missed linking the article, thanks for linking it. I quoted a part that quotes the law, but the actual law is normally too cryptic. I'll link newspaper and law in the future as I agree it's important for some people.

Wouldn't it be possible to create micro grids?

Expressly forbidden. This law is a custom suit for electric companies.

The problem is demand will vary the same for all those in the same locality with time of day.

Now, if you could somehow form a grid with people on the opposite side of the globe...

BTW I like the idea of hydrobatteries: hydroelectric power stations sometimes pump water back up into the resevoir. One could do this with local water towers; perhaps even dual-purpose existing rain tanks, per house. Maybe not large enough; haven't done the math.

Here you go:

E = mgh

1000l tank = 1000kg

7m high roof (~2 stories)

E = 1000kg * 9.81ms^-2 * 7m

=~ 70 000j

1Wh = 3600j

So a 1000l tank on your two story high roof would be able to store ~19Wh

Not including mechanical losses

For comparison a single decent sized SLA battery will be able to store 1000 Wh

Thanks! Not as good aa I'd hoped...

The numbers work better with increasing size, because volume is the cube of the dimensions. Also, you can build a pond on a hill with some excavators much more efficiently per unit volume than an enclosed plastic container.

A 1m cube weighs 1,000kg and has about 20Wh. A 10m cube weighs 1,000,000 kg and has about 20,000 Wh. A 50m deep, 1 km square reservoir has 1,000,000 Wh. And that's still assuming that it's 7m above the turbine!

can you elaborate on this? You mean the feed-in tariffs for individuals were cut in Spain? Is it different for companies who build solar farms?

Sure, just a quick search. Worth noting that not following this law has a higher penalty than having a nuclear leak in a nuclear plant:

> The new law also prohibits PV systems up to 100 kW from selling electricity. Instead, their owners are required to donate the extra electricity to the grid for free.



Its incredibly satisfying going off-grid. We have an off-grid cabin and its awesome turning up and finding the batteries fully charged and ready to dispense free electricity.

During the summer, rain water, solar power, cooking over a wood fire and walking or cycling to the beach means you can actually live at entirely carbon zero. One of the kids was fascinated by the idea that his iphone had been powered up using on energy from the sun.

Kudos to OP for doing all this in a city apartment!

>means you can actually live at entirely carbon zero

That's not enough. You need to also do something to offset the carbon dioxide that went into manufacturing everything and the transportation for it. Make sure you plant a few hundred trees if you want to be at carbon zero. You also need to plant trees to replace the wood you burn. And you need to offset the CO2 from process of making any food you bring in as well. Otherwise it's an unjustified feel-good exercise to claim you are living at carbon zero.

Actually, one needs to kill oneself (not with fire). Living takes up carbon.

Come on. Acting as if any "carbon positive" living is immoral, is insanity.

He said the claim of living carbon neutral was incorrect not immoral.

No, they were letting perfect be the enemy of good.

Calling out blatantly incorrect statements is not letting perfect be the enemy of the good. Electricity side effects is such a small percentage of the CO2 from a single person that neutralizing it and claiming carbon zero is ridiculous.

Why would planting trees not work?

It takes decades for those trees to grow to firewood size. In the meantime there will be carbon "in flight". Since the trees will be cut down and burned again, effectively replanting only reduces emissions by some fraction, dependent on the growth time. Burning wood, especially at your cabin, has a high emission rate, so an electric stove might be better, and fairly certainly is if powered by a solar panel.

Sure. But for some number of trees planted, you WILL eventually displace the carbon.

Trees die. Decomposing, or burning, gives off all the carbon they soaked up.

Cut the trees down, make paper out of it, print government regulations and statistics and reports on it, store these in a vault permanently. You have a carbon sink.

That sounds like it was a submission for shithackernewssays.

That comment just made my day :)

This is not true. Much carbon is left behind after burning or decomposition.

This can however take a decades or a few hundres years if not more. Around here they have found logs thousand of years old in the swamps.

> in the swamps

probably because theres not much O2 in the water compared to the atmosphere.

It's a bit more complicated than that. The original source for the carbon that humans emit is the atmosphere itself, so overall humans are carbon neutral. And since a human body itself contains carbon, until it has completely decomposed the body itself is carbon negative.

>kill oneself (not with fire)

lol...that's the funniest thing I've read all month.

> to replace the wood you burn

trees have a lifecycle, and for the time the tree was a live, it was sequestering carbon from the atmosphere. firewood needn't come from a living tree. and cutting some down can leave room and nutrients for others to grow.

Yes, we have a few hundred trees.

Good point about the food though.

>> at entirely carbon zero.

Not even close. You're still eating something. Unless that came from a magic farm, fuel was used to generate/transport that food. And to complete the picture, you still have all the external resources provided by a very carbon-hungry society. That includes everything from health and education to military infrastructures ... all of which burn carbon in epic amounts. Carbon zero is an idea, not something that any one person can every accomplish.

Electricity derived from solar panels and stored in batteries is neither free from cost nor free from carbon emissions. The monetary cost and emission of carbon coincides with the manufacture of the solar panels and batteries rather than the generation and storage of the energy unlike many other technologies.

The costs and emissions of solar-derived electricity may be lower than alternatives but they are most certainly not free.

Yes, I should have said "ignoring the embodied energy of the panels & associated equipment".

This is somewhat justifiable for the panels since they have a 25+ year life.

Less so for the batteries, which have maybe an 8 year life with good care. We try to burn power as much as possible (e.g. running the water pump) when the sun's up, so it doesn't have to pass through the batteries.

A lot of carbon goes it to making solar panels.


Is burning wood carbon zero? My in-law/relatives in Alaska say it can pollute quite a bit. Though I don't know how that relates to any carbon zero metric.

Burning wood is not carbon zero. It is the reverse of carbon sequestration in the sense that atmospheric CO2 was once converted to wood by the tree, and now the wood is being burned and the captured carbon release back into the atmosphere.

That could be nearly carbon zero (I don't know the contributions from soil and what mass remains as ashes, etc..), except when you consider the opportunity cost.

That burned tree, presumably healthy just prior, loses the ability to sequester any more carbon. A burned tree puts carbon in the atmosphere AND removes a carbon sequesterer simultaneously. That act is removing X amount of future sequestration until the tree would have naturally died and turned to soil. At that point most of that carbon would still be in solid form and not in the atmosphere.

I'm nitpicking at this point, but I lean toward burning wood as not carbon zero for the sake of opportunity cost.

It really only makes sense to measure the carbon capture at the level of the forest. When a tree is cut down or dies, it makes room for other trees to grow. Removing mature trees that are no longer growing very much can increase the rate of capture. Removing trees that are growing quickly and replacing them with smaller trees could reduce the rate of capture.

Either way, there is a limit to how much carbon a given forest will capture (rot releases it just as well as fire) and it will only do it for the life of the forest, which is usually not a geologic time scale.

Doesn't that exactly describe a carbon-neutral lifecycle?

Good point, I really didn't complete my thought. Updating my comment to explain.

Biochar is a potential solution, although the technology isn't there yet (at an industrial scale).

If wood is heated in an oxygen free environment it will turn into a form of charcoal. At the same time it will release gases (like methane) that can be captured and used as a fuel separately.

Rather than burning the charcoal, it is put back into the soil which effectively traps the CO2. This also improves the condition of the soil and reduces the need for fertilisers.

I think rotting logs release about the same carbon as burning. Rotting 'burns' the log too.

And much of what we burn is replaced, right? With younger, faster-growing trees.

It's a net zero emission as long as the trees come from a sustainable forest.

Only if the person actually plants a tree for every fire they burn. Even then, that does not offset the ash and other chemicals in the thick smoke ejected into the air that causes huge pollution problems at any scale.

A healthy forest plants trees all on its own.

I'm wondering how forest fires being a natural thing fit into your viewpoint. I don't think that fact entirely negates your point, but it does seem to dampen it at least.

Trees contain carbon. Burn trees, and they release carbon. New trees end up growing in the ash after it falls and re-capturing carbon. It's a natural, cyclic process.

The problem isn't that humans release carbon or other pollutants (burning trees, coal, oil, etc), it's the scale we do it at, and that we don't automatically re-capture it without doing extra work like planting more trees.

>Only if the person actually plants a tree for every fire they burn.

But wouldn't a tree be more likely to grow, and in the long run the expected number of trees in a forest be unaffected by the felling of any given tree? (the same can't necessarily be said for the felling of hundreds of trees of course).

Not to mention the well documented health issues related to regularly inhaling wood smoke, even in small amounts.

> and other chemicals

you mean "the chemicals" that came from nature in the first place ?

Yes, like plutonium, but we're not going to be dumping that all over the place either.

Cyanide is also "natural" but not great for our health depending on the context. The same for the "chemicals" that, when burned, cause some nasty stuff compared to if it wasn't burned.

* I love burning wood.

Carbon is not the only form of pollution, burning stuff generally puts a lot of nasty crap into the air.

Wood specifically is like 50% carbon by weight, no?

Long-term exposure to burning wood for heating and cooking can cause heart and lung disease.[1]

The main air pollutants in wood smoke are particulate matter (PM), carbon monoxide, carbon dioxide, nitrogen oxides and a range of other organic compounds like formaldehyde, benzene and polycyclic aromatic hydrocarbons.[1][2]

Using reverse-cycle refrigerant heating (or 'heat pumps') is probably the least worst polluting method of heating. Modern heat pumps can generate (well, move) four times more heat energy than used to drive the pump[3], with the added benefit of moving the source of pollution away from populated areas, or being carbon neutral via window, solar, hydro, geothermal.

1. http://www.health.nsw.gov.au/environment/factsheets/Pages/wo...

2. https://www.environment.gov.au/resource/wood-heater-particle...

3. https://en.wikipedia.org/wiki/Heat_pump#Performance_Consider...

Heat pumps only really work well when they have access to fairly warm temperatures. They are kind of worthless in the far north and direct fuel use is significantly more efficient.

If you burn coal for power at 40% efficiency and run a heat pump at 400% efficiency that's only 1.6x heat gain ignoring transportation losses. Drop that heat pump down to 150% efficiency and heating oil can become a better option.

In most areas using solar thermal heaters with backup resistance heating is actually the best overall option. But, in most of Alaska heating oil is much more viable.

Very good points, yes I hadn't thought about much colder areas. I'm at 41 degrees south where heat pumps still work okay.

Aarg, sorry for downvote. Finger slipped.

I think you're right about the cleanness of heat pump systems. Unfortunately they do not have the libertarian freedom flavour of a wood fire.

That would imply 50% non-carbon.

Most of that is probably water.

"Crap in the air" tends to precipitate. In Alaska, over either an ocean or an area in which no one lives.

Burning wood is ultimately carbon neutral, deforestation is the problem.

And here we need to be careful: around here there is a major problem with trees filling up what was once farmland.

No problem you may say but it means less local produce and more import, both import of meat as well as animal food.

Where's that? How productive/marginal was the farmland?

Up in the Yukon and Alaska plenty of people live in off-grid houses/cabins year round. It's amazing to never get a bill for your house - no water, no electricity, no garbage collections, etc. etc.

Friends have a 10kW system which in summer provides plenty of power for a sump pump for water, a big TV, espresso machine, etc. etc. In the winter they have to watch what they use, and they usually run the generator for a couple of hours a week to keep the batteries at a healthy level.

upvoted but also agree with others pointing out that you're far from being 'carbon zero', not that there's anything wrong with it :)

Nice project, but I disagree on one point:

> For lighting, it's impossible to fall back on grid power because I had to cut the power cords of all lamps to make them compatible with the 12V DC grid

Why not get a cheap-ass car battery charger? He's using lead-acid batteries anyway, and a charger for these is approx. 50 €.

Or bypass the battery entirely and use a 12V 200W power supply instead of the battery voltage (to avoid overloading your PSU with powering the equipment AND simultaneously charging the battery).

>Some important challenges remain, most notably the washing machine, the bathroom and the laser printer. The problem with washing machine and bathroom is that they're on the north side of the building, far from the solar panels. We could go to a laundromat but there are none in town. A pedal powered washing machine requires space that we don't have.

You could try washing your laundry by hand. It isn't as much work as it might seem if you have never tried it. There must be something magical in the detergent because I can get clothes cleaner than I ever had with a washer back home with little work.

For example, to wash a shirt I just put the water / detergent mix in a basin and agitate the shirt with my hands for a couple minutes. Leave the shirt in the basin for 15 minutes for the detergent to do it's work. Agitate for another few minutes and then hang. First hang in the bathroom or outside for 20 for the shirt to quit dripping and then I put in front of a fan. The shirt is dry within a couple of hours.

Pants can be a bit more work depending on the material. Denim is heavy and eats up the dirt. I do the same as with the shirt but I use a tide bar to spot soap areas which get more dirt (bottoms of the pant legs) and brush those areas.

This does take longer than using a washing machine. But the clothes last longer and get cleaner. You aren't using electricity, buying an appliance and birthing a hung of metal and plastic that you may one day have to dispose of.

One weird effect that doing laundry by hand has for me is that it sort of puts me closer to my stuff. It's too easy to get something dirty, throw it in the washer and forget about it. Hand washing makes me more aware of how what I own also owns me and the energy it takes to maintain and carry this stuff around with me.

Sadly, giving up on the washing machine is giving up one on of the great labour saving inventions, and going back towards the time when washing took at least one woman-day per week.



Back in the day when men were out working and families were larger, women had to do a lot of work do to laundry because they would do laundry for the entire family. Doing your own laundry doesn't take long. Still more work than using a washing machine, but not too bad.

Don't you rinse your clothes before wearing them? Detergents can do nasty things to your skin.

Yes, after washing with detergent you put fresh water in the basin and rinse the detergent.

Yep, and washing clothes by hand is oddly therapeutic as well. You end up looking for other items to wash, like bedsheets and towels and what not.

But it does do a number on your hands.

Use a bucket and a washing stool (wooden agitator)?

For me personally it's more about the dryer. I live in a cold/damp climate where it takes forever to line dry except for like 2-3 sunny/warm weeks in the summer.

During rainy season I can't line dry. I just hang the clothes in the bathroom until they stop dripping and then put them in front of the fan. This is as quick or quicker than line drying in the sun.

Could people with houses use legacy PSTN wiring to distribute 12V throughout the house?

POTS wires are 24 gauge [0] which can handle 3.5 amps [1] so you'd be able to transmit 12V * 3.5A = 42 Watts.

POTS often had 36V on it to power the ringer on phones so you could potentially up the power transmission by running your system at 14V. Some devices which consume a fixed amount of power would use less current, other devices would just use more power at higher voltage.

[0] https://en.wikipedia.org/wiki/Plain_old_telephone_service [1] http://www.powerstream.com/Wire_Size.htm

> POTS wires are 24 gauge ... transmit 12V * 3.5A = 42 Watts.

But AWG24 cable also has a resistance of 0.08Ω/m (0.024Ω/ft). With a 10m (33ft) cable this amounts to (current has to travel both ways): R=2⋅ℓ=1.6 Ohms, at 3.5A this drops 5.6V. So, in the end you'd loose RI²=19.6W in the cable and only get 22.4W (3.5A at 6.4V) in the load...

42 watts seems ok for a very small installation, right? I'm thinking enough to charge a phone and maybe a laptop. And, that would be driveable with a small 12V battery and a small solar panel.

As others have pointed out voltage drop is a significant problem with low voltage systems. #24 is 84 ohms per km, or 0.084 ohms per metre. Say the system is running at 13.4 V and the loads will work on as little as 11.5V before they brown out, that means we can have 13.4-11.5V voltage drop = 1.9V voltage drop. ohms law V=IR so for 3.5A and 1.9V R=0.54 ohms total resistance, and at .084 ohms per metre we can transmit 3.5A 6.46 metres before the voltage drop will be unacceptable.

You could charge a phone, but even my small laptop chargers are over 60W. The big ones are 90W.

Also don't try this in your house! pushing 3.5A through that little pinner wire it could get hot and start a fire.

Voltage drop is one way to look at it, but since efficiency is paramount, it's better to look at losses. Losses in the conductor are I^2 * R, so when there's a current of 3.5A, losses are 6.6W at an input of 3.5*13.4=46.9W. Efficiency is 88% which is very bad. An average inverter that converts the low DC voltage to AC is much more efficient and even with taking into account the wiring loss, there is a net gain. Generally, using a low voltage DC grid isn't a good idea.

Wouldn't there be 4 conductors, so resistance would be half when you pair them together?


But i forgot about the resistance from the load back to the source so above where I said 6m should actually be 3m. Or if two wires are parallel both from source to load and load back to source then we're back to 6m.

Makes sense. Could you instead apply a DC bias to the AC power jack?

Some laptops use over 150 watts, so it would have to be an extremely tiny laptop.

The Macbook Air has a 45W charger. Assuming you're using DC (no conversion inefficiencies), you should be able to charge it.

Sorry but No. The phone line has DC to power the old-style carbon microphone and AC to ring the bell. If you try to draw appreciable current, the system thinks your phone is "off hook", so the phone is out of service.

You can draw a tiny current without triggering the "off hook" detector, but that is miniscule.

the question is about the wiring, not about keeping the PSTN working while using the wiring.

Yes, but you'd be better off using a higher voltage and switching DC-DC converters at the end.

The POTS lines would have ~50V on them in normal operation so they'd be insulated for 48V. However, V=I/R, and the lines have a constant resistance so if you can raise V and lower I you can get the same total wattage for a lower line loss. This is also why distribution networks are at 11kV and up.

Modern switching converters are pretty efficient, and you can also tailor them for the device so you don't have to double convert.

Since you have 4 conductors to work with, you could run 12V for low-amperage applications and 48V for high-amperage stuff that justifies the switchgear.

Yes, but only for very small amounts of power, as others have pointed out. A better idea would be to run DC on a select few runs of the existing 14-gauge romex from your breaker box to the rooms they serve. You'd be taking those 110v lines out of service and using them exclusively for DC, but you could pump a lot more power across them than you could across telephone wire. (You still wouldn't be able to run electric heating appliances or big motors or incandescent lights, but pretty much everything else in a modern house would work, modulo the need for switched DC-DC voltage converters.)

incredibly inefficiently, and only for loads of 5-10W max... phone wiring is not thick enough in gauge and 12V has very high voltage drop over distance for any appreciable amperage.

there is a good reason why we use 110-240VAC to distribute power in houses.

The phone line is essentially "constant current". There's 48V before you draw current, but that quickly drops to zero when you lift the handset, because there's an exchange relay in series which senses when the phone is "off-hook"


Is 16 ohms per thousand feet really that high?

Yes. Typically devices can tolerate a voltage drop of about 3%. With that resistance, a 1A load can only go 22.5 ft from the source. Considering you might have to run up a wall, across the ceiling and down another wall, you might not even get to the opposite side of a room.

No. In fact most newer solar installations are using microinverters to convert to AC at the source. 20-30amps of DC requires quite a bit of copper to go even a few meters.

20-30amps of DC requires very little copper if it's high-voltage. It's low voltage that requires fat copper, not DC vs. AC.

The same number of amps will require the same cross-sectional area of Copper, for both DC and AC.

You can use less copper for the same power with higher voltage as a reduced current is required for the same power. This is also independent of AC/DC.

(nitpicking) That's correct if you take into account the skin effect when computing the cross-section area (or if you design your transmission line to avoid it. Better solution). But at 50/60 Hz, it's negligible (the "skin depth" of copper at these frequencies is around 9mm)

Except for electric cars there is very little consumer facing HV DC. Solar panels are 12/24/36/48V. With a 20-30 meter cable run it makes sense to convert it to higher voltage at the source. Since it's going to be used in traditional AC grid system, skip a step and convert it to AC as well. Kills 2 birds.

True. And HV DC (more than 50 volts or so) is more likely to kill you than HV AC if you grab a live conductor. Just the same, if I were building a new PV-powered house today I would try very hard to wire it as a mostly-DC house with 12-gauge or bigger romex and switchable voltages at the breaker box in increments of 12, up to 48. I'd put in point-of-use inverters at the few places that needed them instead of having 100 point-of-use rectifiers like we have today. The overall efficiency of a DC house would be quite a bit higher than a typical AC home.

I live on a boat and from my experience you're better off using AC. We have 12VDC outlets and 5VDC USB outlets around the boat. Except for basic lighting they are practically useless. The 12VDC cigar adapters aren't designed for the load we put on them 80-90W (120W and they get extremely hot). And with motors you get into other concerns like the starting current can be 3-4x higher.

We have a single 3kVA inverter for the entire boat. From this we can run clothes washer, power tools, kitchen tools, and blow dryer from our batteries. Modern wall warts are incredibly efficient. You are losing, at most, 3-5% efficiency. Plus, it's really hard to find 12V anything thats any good. A 12VDC vacuum cleaner is a joke compared to a proper AC vacuum cleaner.

Trust me whatever efficiency you think you'll be saving is better off buying more solar or bigger battery bank. Keep the distribution simple, 120/220V. Point of use inverters are for charging laptops in the car.

Why is it a good idea to get off the grid? Genuinely curious. I would think that a networked connection of energy input/output nodes that is globally optimized would be a good thing. Not sure why it's better for anyone to have every node (home) operate independently.

1 reason is you don't have to deal with the red tape of the ILEC. I've read a few stories of people installing solar onto their house. Then, when it's time to tie into the grid the electric company won't certify the install or drags their feet for months.

Even if you do get it tied in any new changes require recertification. I can understand the position of the ILEC. The homeowner just wants to get up and running quickly. The electric company wants to ensure the stability of the grid.

In places with net metering, the electric company often seems more interested in the profitability of the grid, which tends to delay approvals.

The article says 2/3 of the power bill was network connection cost.

>Why is it a good idea to get off the grid?

It's not necessarily. If you use solar cells in your home, CO2 emission is something like 180g per kWh. In that case you'd be better of getting you power from the grid, if you can buy power from wind farms or nuclear power plant. It's better than coal, but only marginally better than natural gas.

If you happen to live in a country where you'll need heating for large parts of the year, it also pretty hard to beat the efficiency of a large district heating plant.

It always struck me more as an engineer rig problem to solve. Sure there's an environmental aspect about divesting from fossil fuels, but the real appeal always struck me as engaging in the romanticism of being off on your own in the middle of nowhere and independent.

Sure making your apartment energy independent doesn't have to the romanticism, but it still has the engineering problem.

That's an interesting question and something I hadn't thought about. I think the biggest motivation for going off-grid is the relatively cleaner outcome. I.e. the control over the source/production (e.g. solar vs coal). So overall my guess is that the intent isn't to operate independent nodes but moreover to have control over the way the electricity is produced.

Transporting power isn't cheap. If you can generate the power where you need it, then you eliminate the need to transport it.

I don't know about Spain in particular, but to me it feels that apartment electricity is massively overpowered (in terms of the effect). In my country the max effect for apartments is 3x16 A = 11 kW. My consumption is 35-40 kWh/month. Unsurprisingly I pay more for the grid connection and the effect, than the actual energy production.

Ok, if I max out my stove completely it could _theoretically_ reach around 10 kW, but only if all four burners AND the oven are turned on at the same time.

It feels like it would be a better idea to install a battery in high-effect appliances to spread out the consumption over the day, than having a guaranteed 11 kW effect available 24/7/365 just in case... (and not everybody needs a stove with four burners, or even reliable power)

Nice, but a lot of apartment managers would freak out over those kinds of installations being visible, at least for any halfway decent apartments.

Agreed, I've lived at probably 8 different complexes in my life and none of them would have allowed this. I've had managers bitch at me for taking down vertical blinds and only having curtains.

Actually most modern cities forbid any modification to a building's facade.

Sad that we don't have a 12V power socket standard that is better than the lighter socket.

In the US at least, and other countries have adopted it, the Anderson power pole is becoming the standard. Anderson power poles are genderless and keyed. In other words, you can connect any similar amp connector to any other, and you can't plug them in wrong (almost). You can put power pole pigtails on all your 12V sources, and power pole pigtails on all your 12V devices, then make any (reasonable) length of extension cable with power poles at either end.

The most common amperages (15, 30, 45) use the same plastic housing, so you can connect a 15A device into a 45A rated power source. The higher amp rated power poles are are 75A, 120A, 175A, and 350A. These are more commonly seen on trucks and commony used to attach things like a winch. I have a set of 175A power poles attached to my Prius to run an inverter, and I have a long set of heavy duty jumper cables that I split near one end put a 175A powerpole set inline (so I can connect my inverter (or my prius) to almost any external source.

https://powerwerx.com/anderson-powerpole-connectors-15amp-bo... https://en.wikipedia.org/wiki/Anderson_Powerpole#De_facto_st...

It takes a bit of money to get into using them (you need a set of crimpers, and the insertion/extraction tool is a lifesaver here as well). Unless you buy in a lot of bulk, you can expect $1/end you make. If you're in an a club (amateur radio/model trains/rc), someone might be able to lend you a crimp tool or make up some adapters for you. But once you start replacing ends and seeing the usefulness of it, you'll probably want to put ends on everything 12V. I've got pretty much everything 12V of mine switched over, and a handful of adapters to go from power to: alligator clips, ring terminal, bare wire, car DC socket (cigarette lighter), bananna clips, trailer connector.

USB C PD (power delivery) delivers up to 5W at 20V. Used for charging laptops now, we'll be using it for light bulbs in a few years time, I'm sure.

Grid actually is good (easier to balance etc). "Utility grid" is what causes most inconveniences.

What is this, Hacker News or something? :) (Just nice to see this kind of thing on here)

It's great that the author wrote up their approach, but one thing I don't see is how this was managed with the landlord. There is some clue in that the landlord installed the solar water heater. My interest comes from my belief that my landlord (or more likely the condo association that our apartment is in) would never allow this sort of installation. Aside from "aesthetic concerns", solar panels can potentially cause insurance rates to go up (firefighters don't like to douse electricity generators with water).

Solar hot water panels do not generate electricity. They heat up a fluid (glycol) which is used to heat up your water.

I'm referring to the PV panels the author mentioned putting on his window sill. Agreed that the hot water system isn't a fire concern.

I recently built a flat roof 35m2 home office/gym at the back of my garden. I'm currently using an electrical convection heater and a 9kw instant water heater for shower/basin.

What would be the most cost effective way to use solar instead for heating/shower? I was thinking about putting a 100-200 litre insulated tank either inside or outside, and heat that with solar to about 70c, to use for both heating in the winter, and showers. I don't need cooling in the summer.

Has anyone done this?

It is great to be knowledgeable about energy consumption and conservation methods and to try to spread that knowledge. Realistically however, any action is negligible unless it is done by industries that will have a huge effect on the environment (airlines, for instance).

If you want to achieve X, it is ultimately best to spend your time convincing a certain number of local businesses to do X, or petitioning governments, etc.

Lobbying private or public interests is definitely important if you want to have an impact. The other half of that is that people have to actually do the things you're lobbying for.

Implementing these ideas personally is more than just collecting knowledge -- it's contributing to the desired effect.

To boot, in a conversation where you'll subsequently advocate for energy consumption, one of the easiest ways to build trust will be to speak from a position of experience -- to know what probing questions to ask about your audience's life experiences that will help them build a future story in which they're enjoying conserving energy.

You might also want to check the batteries you are using for your system. Due to the nature of the small space and high use, I remember from my armature radio license exam that some batteries vent gas when under operation. If I remember correctly, one such battery is NiMH.

You should really read into your batteries and your charge controller specifications before doing anything like this.

Other than that, this looks great!

Laser printers need much power for heating. Would it be possible to switch to a ink printer? They should work fine on 10 to 20 Watts. They even have external Poweradapters like a Laptop.

It depends on the usagepattern. Not printing enough would dry up the ink. Printing to much could be to expensive or to slow.

But heating dust up with a laser to melt it down on paper seems to be very inefficient in terms of energyefficiency.

This is veering offtopic but laser printers don't actually use the laser for heating the toner, they use it to create charges on an image drum which picks up the toner electrostatically. The fuser assembly is a very simple resistive heater.

Nice use of an in house microgrid. To me the striking thing was how the LED bulbs designed to be plugged into 220VAC 'just work' when plugged into 12VDC; I know this is because of their switchmode power supplies, it's still surprising.

You could consider doing this with "19.5V" (popular with laptops), although many will work just fine from 12V, or power-over-ethernet's 48V.

Why not place two 250 watt solar panels vertically in the windows. They are big enough.

All that work to get 150Wh per day? That's what, 20 cents worth of grid electricity?

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