[HN Gopher] Direct Solar Power: Off-Grid Without Batteries
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Direct Solar Power: Off-Grid Without Batteries
Author : bookofjoe
Score : 54 points
Date : 2023-09-13 19:32 UTC (3 hours ago)
(HTM) web link (solar.lowtechmagazine.com)
(TXT) w3m dump (solar.lowtechmagazine.com)
| AYBABTME wrote:
| The idea that we should somehow just follow what nature dictates
| and revert to less is never going to work. We'll go mine
| asteroids if there's not enough material on Earth to make the
| batteries we need to run our industries 24/7, lights out. We want
| everything faster, in more comfort, to last longer, to be
| cheaper, to be more automated, to me more grandiose, to be more
| precise, to be more convenient.
|
| If humans wanted to live by nature's vagaries, they would have
| remained chimps.
| voisin wrote:
| > We want everything faster, in more comfort, to last longer,
| to be cheaper, to be more automated, to me more grandiose, to
| be more precise, to be more convenient.
|
| Perhaps some of these should be reevaluated since it appear
| clear that their cost means less duration as a species.
| imbusy111 wrote:
| "That is because these systems use the central power grid, which
| largely runs on fossil fuels, as a kind of battery to cope with
| power shortages." - not according to PG&E reports from Sonoma
| County, California, where less than 5% is fossil (natural gas)
| for 2022.
|
| PG&E Generation Mix: 5% Biomass & Biowaste, 1% Geothermal, 2%
| Eligible Hydroelectric, 22% Solar, 9% Wind, 8% Large
| Hydroelectric, 5% Natural Gas, 49% Nuclear.
| jancsika wrote:
| They're just 9% away from giving 110%.
|
| Good hustle!
| lazide wrote:
| Also, that nuclear plant is going offline in about a year
| [https://www.pge.com/en_US/safety/how-the-system-
| works/diablo...]
| philipkglass wrote:
| I don't think that it will be. The state and PG&E want to
| keep it running through 2030 and the federal government is
| helping:
|
| https://www.sanluisobispo.com/news/local/environment/articl
| e...
|
| _Diablo Canyon was expected to stop operating its twin
| reactors in 2024 and 2025, but the state failed to procure
| enough clean energy to replace the plant in time. In
| September, the California State Legislature passed Senate
| Bill 846, which allocated $1.4 billion to PG &E to fund the
| nuclear power plant's license renewal costs for staying
| open through 2030.
|
| That was followed by a $1.1 billion grant to PG&E in
| November from the U.S. Department of Energy through
| President Joe Biden's bipartisan infrastructure law.
|
| The NRC in March told PG&E it can run Diablo Canyon past
| its original closure dates without a current license as
| long as the utility company submits a valid license renewal
| application for the two reactors by the end of 2023.
|
| PG&E has said it will file a license renewal application
| for Diablo Canyon by the end of this year._
| lazide wrote:
| Hah! Still, that does rather shoot the original boast in
| the head, eh?
|
| 'We're renewable, as long as we do emergency measures
| (and override safety rules) to keep our creaking old nuke
| plants online because we can't get enough renewable
| energy.'
| jedc wrote:
| It's unlikely to go offline. They've got the funding to
| keep it open, they're just waiting on federal acceptance of
| their continuation plans.
| RetroTechie wrote:
| Very good read that discusses a lot of options & strategies for
| using solar power cost-effectively.
|
| 1 thing I found lacking: discussion of optimal power point
| tracking. If ignored (PV panel -> load directly) then depending
| on the load's characteristics, it can pull the solar panel into
| very sub-optimal power generation.
|
| That is _an_ advantage of heaving batteries in the system: they
| can serve as a predictable / constant load, which a charge
| controller uses to have the solar panel operate at near-maximum
| output.
|
| But as the article notes: any power that goes through a battery
| rather than used directly, is relatively expensive. So it makes
| sense to minimize battery size & throw money at more solar panels
| instead.
| hex4def6 wrote:
| Completely agree.
|
| I think there's something to be said for time-shifting
| predictable large energy consumption events to points at which
| you're producing more solar energy than can be stored.
|
| Scheduling an electric water heater to run at noon until 2pm
| for instance, depending on the insulation and size of the tank
| might be enough to provide all the hot water you might need for
| 24 hrs. Likewise, for electric car charging.
|
| But there is definitely a minimum battery bank size requirement
| for maximum efficiency, especially if this is an off-the-grid
| setup where you can't rely on the grid to act as infinite
| excess storage.
|
| Without batteries, you're either overproducing (and therefore
| throwing that power away by backing off the MPPT point), or
| you're underproducing (and therefore browning out). Therefore,
| you have to size your solar array for the worst case spike. AC
| locked rotor might be 30A for instance -- better make sure
| you're producing at least 7.2kW (~9.5kW of solar+) at any time
| the AC might flick on.
|
| The higher the peak-to-average of your daily load, the more
| inefficient your setup will be. In our 9.5kW array example,
| this means any time you're consuming less than that, you're
| paying for panels that are effectively offline.
|
| I think it's an interesting problem to solve, with a lot of
| variables. If the limiting factor is $ vs. roof space vs. ROI
| vs. 99.9% uptime, you might get different "optimal" answers.
| EricE wrote:
| A solar water heater would be a hell of a lot more efficient
| than generating electricity via solar then trying to heat
| water with that!
| wayfinder wrote:
| Funny thing -- heating a hot water tank is still storing
| energy in a battery.
|
| Charging your car is still putting energy in a battery.
|
| And the article mentions that devices sometimes have a built
| in battery.
|
| The article is talks about getting rid of batteries but
| really is talking about maximizing energy usage during times
| of cheaper energy... which is the "smart grid" stuff OP is
| throwing shade at.
|
| I don't disagree with the idea of maximizing your energy
| usage during times of cheap energy availability but obviously
| most people don't do it because the trade off is higher
| scheduling complexity. What if you set a timer for your
| washing machine but the sun doesn't come out -- now you just
| have no fresh clothes..
|
| And plus some batteries are only possible at scale -- like
| pumped water storage. Setting up that complex distribution
| infrastructure allows society to invest in more efficient
| forms of energy storage and distribute its costs.
| adql wrote:
| > 1 thing I found lacking: discussion of optimal power point
| tracking. If ignored (PV panel -> load directly) then depending
| on the load's characteristics, it can pull the solar panel into
| very sub-optimal power generation.
|
| The discussion: Buy MPPT controller
|
| End of discussion
|
| > That is an advantage of heaving batteries in the system: they
| can serve as a predictable / constant load, which a charge
| controller uses to have the solar panel operate at near-maximum
| output.
|
| Well the single disadvantage of batteries is cost, everything
| else is an advantage so there is not much else to discuss here
| too.
| AtlasBarfed wrote:
| I thought there were LFP chemistries with virtually unlimited
| recharge cycles. That's what Jeffrey Dahm stated back when Tesla
| was bragging about the million mile range battery pack.
|
| With Sodium Ion entering mass production, and whatever mishmash
| of solid state and sulfur techs hit mainstream, I think batteries
| will be the way to go. There's always flywheels too.
| marksbrown wrote:
| So living on a narrowboat in the UK this is something I have
| experience with. We have a 335 W panel with an MPPT connected to
| a 200 Ah 12 V flooded lead acid battery. The battery in reality
| has a capacity of half that and in the 6 years of seasonality it
| has probably halved.
|
| A few things :
|
| * you don't need a fridge in winter so you can just turn it off.
| * charging battery banks / laptops in sunny periods results in
| the battery bank being useful in times when the weather isn't so
| kind. * no amount of solar is enough in the deep of winter. * any
| amount of solar is too much in the height of summer. * pubs are
| great for charging devices. * lead acid batteries last
| substantially longer if you only let them drop to half their true
| capacity and regularly charge them. Yes alternatives exist but
| there's something to be said for making what you have work for as
| long as possible.
| latchkey wrote:
| I've got a 300ah 12v LiFePO4 battery in my campervan, which
| cost $1k.
|
| It is way too much power cause the thing is constantly being
| charged every time the sun shines and it is pretty hard to use
| 300ah in a campervan while you're sleeping.
|
| The benefit of LiFePO4 over those AGM batteries, is that you
| can go to zero. It is worth every $ for that and for the weight
| savings (in a campervan).
|
| Highly suggest checking out Will Prowse on YT. He's a great
| resource.
| verisimi wrote:
| > no amount of solar is enough in the deep of winter
|
| > any amount of solar is too much in the height of summer
|
| I totally agree. I can't understand how it why solar is
| promoted, when the winter is when you need more energy as
| you're in more, heating your house, etc. You can't store your
| summer's energy till the winter.
| amanaplanacanal wrote:
| It depends on your local climate. I assume the desert
| southwest in the US uses far more energy in the summer, for
| instance.
| stonogo wrote:
| "No amount is enough" might be true on a boat. I have a land-
| based deployment. In winter my 5 kWh array generates enough
| to heat my 2200-square-foot house, as long as I clear the
| snow. In summer it generates enough to air-condition. This is
| in addition to appliances, televisions, lights, etc. It's not
| like the sun turns off for six months.
| Turskarama wrote:
| Latitude matters so much for this, people love to make
| blanket statements forgetting that their situation doesn't
| apply universally.
|
| People hardly realize (or straight up don't realize) that
| once you're in the tropics even the notions of summer and
| winter start to get fuzzy. Consider: if you're on the
| equator then you can go from "summer" to "winter" in only a
| few steps. Obviously, near the equator solar is a no
| brainer.
|
| And of course the opposite is true, once you're inside the
| arctic circle solar is basically pointless because there
| literally is a period of no sun lasting anywhere from
| several days to several months. Of course not too many
| people live inside the arctic circle so it's not too much
| of an issue.
|
| Even between these extremes though, the usability varies a
| lot.
| Retric wrote:
| Rooftop PV isn't the best plan if you're north of NYC. The
| grid can far more efficiently move power from Southern areas
| that don't need significant heating in the winter up north.
| The transmission losses are vastly lower than the gains you
| get from longer days. And as a bonus you rarely need summer
| cooling while people south of you do.
|
| However, if you're in Main and don't have a ground source
| heat pump then solar thermal works great. PV is panels are
| still only 22% efficient and you air source heat pumps don't
| work well in ultra cold weather, worse you need batteries for
| the long nights. But with solar thermal you're looking at
| ~90% efficiency for heat collection and ultra cheap energy
| storage in hot water tanks. You do get less power per m2 of
| collection area, but that's offset by needing heat for a
| longer period.
|
| Off grid solar can work in the surprisingly far north, just
| expect a significant premium.
| cgh wrote:
| Sure, but the entire point of the article was to get rid of
| batteries so I don't understand what point you are making. This
| guy was trying to live life with solar panels connected
| directly to his devices, no batteries at all.
| nine_k wrote:
| The article has a number of good ideas, as long as you live in a
| sunny place (the author mentions Barcelona) and can adjust your
| day to follow the sun. Then maybe you're OK operating you vacuum
| cleaner or power tools only when the sun is shining (and only on
| weekends if you have a day job).
|
| Also, the author states:
|
| > _The production of lithium-ion batteries requires fossil fuels,
| and (unlike lead-acid batteries) they are not recycled._
|
| I think that there's no strict requirement to use fossil fuels to
| produce batteries, and lithium-based batteries _definitely_ are
| recycled. Unlike lead, lithium is not an environmental and health
| hazard.
|
| That is, in the shortest term, limiting the amount of batteries
| you have and running high-powered stuff directly off solar cells
| is a good approach to limit your carbon footprint. But in the
| longer term, large amounts of energy storage (both electrical and
| thermal) can and should be produced completely with renewable
| energy, thus removing the dependency on sunshine being available
| at a given moment.
| issa wrote:
| I feel like this is one area that requires a less extreme
| approach. It feels silly to forego batteries completely, but
| equally silly to put 100kW of batteries in a car. Most car trips
| for most people are going to be well under 50 miles.
| imbusy111 wrote:
| I have a BMW 330e with 12kWh battery (~20 miles range), mostly
| drive locally in the city, and the car reports ~55% of driving
| is electric for the last two months. Occasional longer trips
| make up the vast majority of non-electric driving.
| issa wrote:
| Exactly. 10 electric cars with 20 mile pure-electric range
| will have a larger impact than 1 electric car with 200 miles.
| imbusy111 wrote:
| You need to be able to plug it in at home though, even if
| it's just a regular wall socket. No one is going to go to a
| charging station for 20 miles of range.
| 1970-01-01 wrote:
| Just like nobody is buying 8 ounce coffee tumblers, nobody is
| buying 50 mile range cars. Electricity and coffee is cheap. The
| coffee tumblers and EV batteries are not. So you buy it bigger
| than it needs to be, fill it up as far as you can, and maybe
| share some before refilling.
| issa wrote:
| I'm not sure your comment makes sense in the context of the
| article and my reply. The whole point is that batteries are
| expensive.
| SigmundA wrote:
| First picture is a laptop, with a battery of course, being
| charged with solar...
|
| Batteries are a cache, they allow harvest energy to be stored and
| used as needed, depending on load you can forgo them so long as
| the load is ok with varying voltage or being cut in and out if
| run through an inverter of some sort or solar controller both
| which will have capacitors that act as little batteries or caches
| to try and provide consistent power until they can't and they
| shut down.
| adql wrote:
| I don't think you need to explain to people here what batteries
| do...
| SigmundA wrote:
| You would think so and yet this article gets posted showing a
| laptop with a battery as the lead...
|
| My point was to get useful power at a stable voltage you need
| some battery like components to buffer the inconsistent power
| delivery of a solar panel so most of the time you see a
| actual battery involved.
|
| Without any batteries you typically need to way over panel
| and still have some caps involved. My parents have a 7kw
| solar system grid tied no batteries with a 1500w emergency
| outlet that runs when the grid is down. Works ok but if
| enough clouds go over it just shuts off the inverter needs a
| lot of excess to maintain a stable 120v output and it has
| rather large filtering caps.
| alex_young wrote:
| The solar fridge thing is one of the more interesting points.
|
| For my own off the grid setup, I went with a cheep high
| efficiency chest freezer ($200) and converted it to a fridge
| using a replacement thermostat. It's about 10x less expensive
| than the equivalent DC fridge, has much better insulation, and
| does the job. I then spent a tiny fraction of the savings on a
| couple of extra solar panels to cover any loss in conversion from
| DC to AC to DC.
| PaulKeeble wrote:
| A Fridge that was solar power aware could absolutely freeze a
| big chunk of water or another material that was more energy
| dense with diverted solar power and then use it as cooling
| through the night when solar wasn't available. The same is true
| of water heaters (for which we have diverters already
| available) for storing hot water and a bunch of other devices
| like ceramic heaters.
|
| A lot of these appliances exist already for shifting power use
| to the sunny hours based on electricity, but right now all the
| various parts don't really work together as the home grid is
| just dumb AC and people orchestrate it all with Home assistant
| where possible.
| zdragnar wrote:
| Do "chest fridges" have a higher risk of mold? With a chest
| freezer, humidity just frosts onto the walls and you can
| periodically defrost and empty it.
|
| With a fridge, moisture from foods and opening the door would
| collect on the bottom, unless you've got it tipped on its side?
| Even still, given how deep it is I would think that might be
| problematic.
|
| FWIW I live in a very humid climate, so maybe it isn't so much
| an issue for you.
| alex_young wrote:
| Honestly IDK. There is a drain in the bottom, and the sides
| and bottom are all actively cooled and covered with aluminum.
| For my case it's in a very dry environment and I take it down
| and deep clean it each season.
| 1053r wrote:
| I stopped reading at paragraph 4. What idiot is buying lead acid
| batteries in 2023 for solar storage systems?
|
| 4 12V 200AH deep cycle lead acid batteries cost $1552 on Amazon
| and hold as much energy in practice as a 100AH 48V LFP battery
| which last 15 years, minimum, and only costs about 6% more up
| front. (Not linking to specific batteries in order to not shill
| for them, but do a little searching for 100AH 48V 4U server rack
| LFP batteries on youtube, and you will find dozens of tutorials.)
| Quality inverters last 30 years, not 10.
|
| Are these people TRYING to light money on fire? Are they fronting
| for someone by trying to make solar look impractical? Or are they
| just stupid?
| [deleted]
| outworlder wrote:
| Other than the fact that most batteries on Amazon are
| counterfeit garbage.
|
| If you want something better and brand name, you'll pay more.
| Sometimes, significantly more.
|
| It still doesn't make sense to use lead acid for off grid, deep
| cycle or not. UPS systems still use them because lead acid
| loves to stay charged at 100% and not drop below half, which is
| fine for UPS that are intended to run only during occasional
| power failures.
|
| LFP batteries also last for thousands of cycles and are safe,
| probably safer than lead acid.
| philipkglass wrote:
| Low Tech Magazine remains a great sourcebook for an alt-history
| novel or role playing campaign. Its advice has increasingly
| diverged from efficient paths toward
| sustainability/decarbonization as the high tech approaches
| (advanced solar, wind, nuclear, batteries, electric vehicle,
| heat pumps...) continue to improve.
|
| Over the past 20 years I have noticed this tendency among a
| subset of people people in the environmental movement. Some
| people loved solar power only when it was expensive and small
| scale. A future world powered by solar once evoked images of
| cozy little villages, bicycles, deglobalization, handmade
| wooden toys, and a slower pace of life. Now that solar power is
| inexpensive and scalable, it's unappealing to people who value
| the cozy aesthetic more than they value meeting quantifiable
| IPCC emissions targets.
| m463 wrote:
| keep reading. You skipped out before the entire point of the
| article in this paragraph:
|
| "For example, if I omitted the battery storage of my solar
| installation, my system would become about 10 times cheaper:
| ..."
|
| and then goes further along this interesting line of
| reasoning...
| PaulKeeble wrote:
| Its notable he skipped the primary chemistry people use for
| storage too, LiPho. They are guaranteed to last 10 years, they
| are about $150 per KWH and can sustain 0.5C charge and
| discharge.
|
| For me at least the storage is about 1/3 of the cost of the
| system and I'll likely have to replace it once (probably with
| Sodium Ion since that is taking off and $50 a KWH) and a new
| inverter and there is no way it costs even half the total
| system install over the lifetime.
| stonogo wrote:
| Speaking of idiots, ordering batteries on Amazon is a great way
| to acquire really shitty batteries. Lead-acid works fine and is
| maintainable. The price parity is _extremely_ recent and
| supply-chain problems still mar the lithium side.
|
| Also, where did you buy your inverters in 1993? I've used about
| six different brands on various deployments and ten years is
| about right for MTBF there. I sure wouldn't trust a fifteen-
| year-old inverter to handle 3500VA continuous, and god forbid
| there's a spike...
| bombcar wrote:
| Lead acid has some really good benefits for low end off grid
| solar, not least of which is the relative lack of rapid
| exothermic decomposition.
|
| And the only inverters we know will last 30 years had to have
| been made in the 90s ...
| jsight wrote:
| I don't understand the benefit relative to lfp that the
| parent comment mentioned. Those are very safe.
|
| Lead acid is much more dangerous than that, IMO, due to the
| potential offgassing.
| rootusrootus wrote:
| > lack of rapid exothermic decomposition
|
| This is a common misunderstanding. The lithium batteries used
| for off-grid and RVs are not the kind you're thinking of.
| They are LiFePO4, and far less susceptible to thermal runaway
| than, for example, an average laptop battery.
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(page generated 2023-09-13 23:00 UTC)