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.
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.
Thanks! I had a (much) smaller LiFePO4 cache battery in my dynamo bike light stored in an outdoor shed that significantly killed its capacity, so I was wondering what people did to manage these types of batteries in outdoor conditions.
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.
The problem with that is that you can have a brownout from a single cloud passing. I note that his "living farm" example is much larger - scale helps. The more you have a "microgrid" or even, you know, the real grid, the more things can balance out without so much need for batteries.
It is quite dramatic how much cheaper and longer lasting the panels are, though.
Made me search narrowboats and that sounds like a neat lifestyle! Here in the US there are people who live on houseboats in lakes like Lake Cumberland (Kentucky), and that’s probably the closest thing we have.
Have you thought about micro wind turbines? I wonder if those would provide some power in the winter just to charge phones and laptops.
Their output is fairly low due to surrounding trees and housing. I did consider wind for heating water however. That might be feasible with a large enough savonius turbine.
> 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.
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.
The UK is a further north than all of the US except Alaska. Seattle is about the same latitude as Paris, New York and Chicago the same as Madrid, and Los Angeles and Houston the same as North Africa.
Solar is never likely to be as important in the UK as it is for the US, but even so it seems it can be helpful because solar generation is at its highest during the summer when wind generation (over a quarter of UK total generation) is lowest.
Winter energy could be done on a (smaller) community basis ... if it constructs a large enough, well-insulated thermal mass, or is lucky to live by one. I grew up in a place where, each winter, a large lake was covered-over by a couple of feet of ice. (Often covered by snow.) The water beneath stayed liquid. A heat-pump under the ice could draw on that source.
Worldwide, the ground itself, a few feet down, stays at about 50F year-around ~~ regardless of outdoor temperature. Locally, summer heat-pumping could be directed underground in some places. Reverse in winter.
Pumping heat from where it's stored is a lot less expensive than transporting and burning fuels. We do need to get better at it.
"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.
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.
I think isolated solar (off-grid) is probably not great unless you're close to the equator, but when you're on the grid every carbon atom displaced from somewhere is valid.
It depends what latitude you are whether the (societywide) heating load in winter or the AC load in summer is greatest. And that breakpoint is moving north all the time.
More and more people want air conditioning. I wouldn't be surprised if lots of people use more energy in the summer.
Even here in Montana, the heat going out in the beginning of winter for a few weeks was not really as obnoxious as some of the really hot days with no AC I've seen.
Yes. But the engine is at least fifty years old and so I'm not inclined to run it just for electricity. Plus it doesn't do it any good to run in idle without any change in revs.
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.
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.
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.
If you have an electric car then the whole article gets thrown out the window. An electric car battery is significantly larger than what you would need for an average house, so just have a battery that can also feed back into the house and you're done.
Yes but. It turns out that PV solar wins on maintenance by a lot; since you don't have to run hot water pipes and keep the solar heater from leaking. With a reasonable system design you can pretty much just connect the wires to your heater element.
I think I read it ends up being close with solar heat still winning. The panels have a range of effectiveness and the heat pump isn't always 400%. The solar thermal is cheap too so even if efficiency were superior with PV panels it would still only be useful if you just had a massive excess of wattage.
> 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.
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.
There's many smart solutions that don't reduce our comfort in any way. One example:
I've worked in a cold store way back. Like, a big warehouse filled with frozen items.
Say products needs to be maintained between -20 and -28C. That 8C is a massive amount of thermal energy. If you'd just cut power, say temperature in the cold store goes from -26 to -21C in a day (for a large cold store, probably less. Volume vs. surface area!). That means as long as you observe the outer ranges, and know how fast the store warms up (when not cooled) you can pick any time of the day to run the cooling systems. The mass of frozen product inside is your battery.
Connect to a bunch of solar panels on roof or nearby solar/wind farm, and you simply run cooling systems when that power comes up.
Versus: add battery storage & run cooling 24/7 to remain as-close-as-possible to optimal temp.
Similar things can be done with many factories, logistics, storage of thermal energy, charging EV batteries & more. Battery storage just gives more flexibility.
It's just using power in a smarter way. Not ditching modern comforts.
I'm with you on what you're saying. But that's different because this is a hands off system that doesn't really change anything to humans' experience, unlike one where you're asking someone to not cook after sunset or some such.
In the case of your freezer example, the freezer is a form of energy storage. Similarly a battery, or a phase change heat battery, are other forms of energy storage. Energy storage is important for the obvious reasons of being able to decouple time of production from time of consumption.
Modern humans built all of civilization on their ability to decouple time of production from consumption.
> 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.
Loss aversion suggests we'll get out of our way to find a maximalist solution where we get to have our cake and eat it too, instead of reneging on anything.
Like EV cars: they had to become better than ICE cars for the switch to happen.
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.
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.
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.
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.
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.
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.
"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.
It seems like a big chunk of the Democratic party started supporting nuclear power at roughly the same time. The IRA passed a few months later, with subsidies for nuclear.
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.
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.'
> It is not so difficult to imagine a modern society where activities such as vacuuming and DIY chores only take place during the day. It is certainly not a return to the Middle Ages.
in the Middle Ages, modern technologies weren't available, and once the sun set, a candle gave light. Showering wasn't popular.
So effectively, the discussed "make the most of daylight modern society" feels like a step back to the Middle Ages to me.
> This system consists of two 50W solar panels on the balcony, a 100 Ah lead-acid battery and a 10A charge controller. The energy generated is used for lighting, the music system, and charging laptops and other electronic devices, among other things. The initial financial investment was 340 euros: 120 euros for the solar panels, 170 euros for the battery and 50 euros for the charge controller.
There’s the problem - the expensive lead acid battery, which is not the best technology to fit the application.
I get the overall point about load shifting to suit solar output, but the point about storage being prohibitively expensive falls flat because they didn’t use the right battery.
Deep cycle lead acid batteries are the cheaper option for the first 1-3 years, but LiFePo4 has more discharge cycles and a longer lifespan (500-1000 cycles vs 3000-5000+).
IMVHO such usage is meaningful for agriculture purposes ranging from automatic irrigation systems with DC pumps, door opener for poultry and SO FAR not much more, in a longer terms IF someone will develop electrical agriculture machines like automatic harvesters and so one, perhaps it will be possible to mount them on rails, makes them autonomous following available direct p.v. powers.
Other applications for small stuff can be for spread sensors.
But running something else it's simply too unreliable. Let's imaging just a simple washing machine on p.v. directly. If it's a sunny day with no clouds at all ok, but if there are just few clouds the irregularly input power makes hard to complete a cycle safely. Similarly we can imaging cooking devices, useful yes, but you can cook only if the p.v. output is there and constant enough. Water heaters with large water storage might be used, since they do not need constant power, BUT they need something else to give hot water in adverse climate, like a wood stove with pipes or something equivalent.
Doable, yes, but I do not know how many can invest enough for having a meaningful set of solar panels + MPPTs and DC devices to power directly for such unstable usability. We have on sale a handful of p.v. direct irrigation systems and they are NOT so cheap, not super expensive, ok, but still not that cheap, so if someone can afford them probably can afford batteries as well, at least for a limited usages just to ensure intra-day services.
Direct solar with no batteries at all is fairly impractical with today's devices.
That's because most devices use constantly varying amounts of power. For example a washing machine might use 1500 watts while heating, 150 watts while spinning, and 5 watts while filling with water. With no storage, you need to have available for it the whole 1500 watts it requires (otherwise the machine will power off). Yet the whole time it's using 5 watts you're wasting 1495 watts.
The vast majority of solar inverters don't even support non-battery non-grid powering of AC devices because of this problem - it ends up being hugely wasteful of solar area.
Near-Storagless off grid setups could be done with small amounts of batteries to even out said peaks and troughs in load. If you want to buy one, they're normally sold as 'hybrid' inverters. Even a tiny battery is enough if you have logic to, for example, turn appliances like fridges, car chargers , or air conditioners off or on based on power availability.
Even something like a laptop, who could theoretically charge at any rate between zero watts and 80 watts, doesn't have support for 'taking only the power available'.
Instead, the laptop power supply will just cut out if it isn't provided with the power it wants to take.
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.
Nice article. Especially in the way it emphasizes energy efficiency over just trying to continue to power the things we already use.
One thing I would have like to have seen discussed, in the section on non-battery storage, is pumped liquid storage.
This is a great technology for grid scale storage, but I wonder how well it could be applied to small scale instalations.
I would think something on the scale of the Living Energy Farm would be able to make good use of this, and maybe even smaller scale, like with a 50gal tank on his balcony?
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.
>> That's what Jeffrey Dahm stated back when Tesla was bragging about the million mile range battery pack. <<
He probably didn't tell you that Tesla LFP EVs would degrade and lose the first 10% of range twice as fast as non-LFPs because LFP EVs must be charged to full 100% frequently.
For home charging, that is ... typical? And for a grid or solar storage system, again, probably a typical situation to top off. Since they are lots of cells, the battery management system can cycle topping off individual cells I would think to keep them fresh, but I'm not 100% sure on that.
All lithium ion batteries, including LFP, degrade much faster under high SOC or high C (or even high DOD, extreme temp). In stationary energy storage systems under low SOC/low C-rates (eg, home powerwalls), LFP could last quite longer than other LIBs and this has been studied for years and widely accepted.
But, contrary to Jeff's Dahn's claim on Tesla's LFP battery pack, we don't really know much about LFP's true lifespan/performance in moving vehicles since they were deemed unsuitable for EV's with high SOC/high C-rates until China spiked them up a few years ago and they weren't studied as rigorously in that particular application/environment. Even as they are mostly limited to entry-level, low-range EVs, there are some early data indicating that LFP degradation in EVs is significant:
The brand new LFP batteries will degrade substantially quicker. There's not long-term retention data for LFP batteries on the market yet, but the trend tends to be substantially faster degradation. Trends show them stabilizing around that 10% degradation mark in about half the time as non-LFP batteries - around 50,000 miles instead of 100,000 miles."
There is also a study by Recurrent, "How Long Do Electric Car Batteries Last?" which seems to corroborate Tessie's finding.
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?
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.
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.
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.
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...
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.
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.
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.
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.
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.
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.