5 ms·

These "minimal battery" concepts are great. They are the sort of thing that would be fantastic (and maintainable) in the event of a grid apocalypse. A similar

by abraae 7y ago

These "minimal battery" concepts are great. They are the sort of thing that would be fantastic (and maintainable) in the event of a grid apocalypse. A similar one would be a hot water cylinder that only heats up when the sun is shining. And maybe something that fills scuba bottles to store electricity as compressed air. etc.

sandworm101 7y ago
Great ideas if you are dead against batteries, but there are massive downsides. Batteries are not evil or expensive, at least if you go with traditional lead-acid ones. They are a thousand times more reliable and efficient than compressed air storage. Compressed air storage has many dangers, from explosions (metal fatigue) to fire (compressing gas creates heat). The best and most reliable method of non-battery storage of energy is the traditional water tower. It used to be standard practice for buildings to maintain water storage tanks on their roofs. Mate a water tank with some solar panels and you can create an energy storage system without heat, high pressures, chemicals, high voltage or even moving parts (the pump has only one moving part).
- adrianN 7y ago
  Lead-acid batteries die after only a few hundred cycles.
  - mgiampapa 7y ago
    No they don't. Case in point, I live off grid with a 24v system composed of 2v lead acid marine batteries. They were 2 years old when I got them and have put them through over 1000 days of use since. Mind you, I don't discharge the system past 23.5v ever, and I check my electrolyte levels weekly adding distilled water as needed, but lead acid are cheap, effective, long lasting, and recyclable with minimal effort. The only thing against them is maintenance, and they are big and heavy. My house doesn't seem to care.
    - ledauphin 7y ago
      I appreciate the anecdata, but do you have an actual cycle count on the batteries? It's not clear to a non-expert (me) how you've disproven the GP.
      - extrapickles 7y ago
        The cycles you get is dependent on the depth of discharge (and more). See the chart in [0], where 100% discharge nets 200 cycles, 50% gives you ~500, 30% is ~1200. One would expect that if you discharge 50%, thats half a cycle, and therefore get 400 cycles, but in reality you get 500. [0]: https://pvcdrom.pveducation.org/BATTERY/charlead.htm https://pvcdrom.pveducation.org/BATTERY/charlead.htm
        ben_bai 7y ago
        Lead batteries can be rejuvenated, with a device mostly called "A pulser/desulfator/refresher" Short story: I had a completely dead 12V car battery. It was at 0V and would not accept a charge at all. Connected it to a bench power supply and slowly cranked the voltage up until it charged with a couple mA @ 30V. Slowly it accepted more amps so I constantly dialed the voltage down until it was charging at 14volts. Then hooked up the desulfator and left it for couple of weeks. Every other day checked voltage and hooked it up to a charger for couple hours. After that it was perfectly able to start my car(oldtimer) again.
        Spare_account 7y ago
        This kind of work requires a supply of power though, which is something of a catch 22 if the battery you are rejuvenating is your power source. That said, this thread has descended from a comment about apocalyptic scenario planning and this general principle of maintaining batteries makes sense. Learning how to build and repair lead acid batteries doesn't seem to be beyond the realms of possibility.
        mgiampapa 7y ago
- abdullahkhalids 7y ago
  Pumped hydro storage is great. The difference between it and batteries is that batteries can be constructed off site by a third party and then transported to your location. Water towers have to be built on site, which can be difficult. Not to mention, to get appreciable storage, you have to build a really tall tower or a really big one. This is difficult too. Especially if you are in a location where the soil shifts or you get high winds. Because now your tower has to survive the elements. There is definitely a strong case against water towers for distributed energy storage.
  - sandworm101 7y ago
    Conversion to or from electrical power is one option, but an elevated water storage (tower or simply up hill) reduces the need for larger water pumps. It means you don't have to run your well during dark hours. So it saves on electric use rather than provide actual electricity.
  - _iyig 7y ago
    Why not dig a pit? You can even load a big mass on top of the water for extra potential energy. Similar system from the age of steam: https://youtu.be/aKmi0PN7LxM https://youtu.be/aKmi0PN7LxM
- abraae 7y ago
  I'm not dead against batteries, we've got an off grid cabin that runs on 4 6v Trojan lead acid batteries and they are great. However there's something about living off grid that makes one want to simplify, and batteries are one of the big, expensive, and limited life time components of a solar system. If you can reduce the load on, and the required capacity of your battery bank, then you have improved reliability significantly. As you say, pumped hydro is certainly a great storage system if the situation permits. It just takes a very large storage system to store as much as batteries. If you have a pond or lake and an easy supply of water it would certainly be my choice.
  - jefftk 7y ago
    > batteries are one of the big, expensive, and limited life time components of a solar system On the other hand, so is a big chest freezer!
- happosai 7y ago
  A lot of the household energy load is either heating (water, cooking, surviving winter) or cooling (fridge, feeezer, surviving summer). You don't have to be dead against batteries to see a lot of potential in using thermal energy storage to decouple renewables energy sources from energy use.
dclowd9901 7y ago
I don’t think a good solar electric hot water system would ever work if it was running only when the sun was shining. It takes _so much energy_ to get water up around the requisite 110+ degrees, that even a very efficient storage system wouldn’t benefit it all that much. Honestly, the best solar powered hot water system is a black plastic bag full of water in the sun. Anything else will require a battery bank at minimum.
- abraae 7y ago
  Depends on the size, but if you have even a modest size solar system you should be good. On a sunny day, a 2kw solar system can drive a 1kw hot water cylinder to full temperature easily. And to avoid legionnaires disease - a risk of inadequately heated water - you only need to drive the temperature up high from time to time, not continuously. Once a day is plenty.
- jdmichal 7y ago
  Don't use solar PVCs to heat water! Solar water heaters are much more efficient than PVCs. Even the lowest-efficiency system listed is 46%, compared to 19% for standard solar cells. https://en.wikipedia.org/wiki/Solar_water_heating#Energy_production https://en.wikipedia.org/wiki/Solar_water_heating#Energy_pro...
  - nullc 7y ago
    Ignoring equipment cost, in many climates PV + a heat pump would outperform a plain solar water heater. :) [Silly to ignore equipment costs, sure, but if you have other uses for PV power ... using PV for heating water isn't necessarily nuts.]
nunodonato 7y ago
I do something similar to that. Living off-grid and my solar setup is quite small (1.6kwh of solar panels and a bunch of batteries). However I depend on electricity for most things, including cooking(induction) and hot water (electric water heater/tank). So in sunny days I let the water tank heat as much as possible(usually around 70-80C), and can go 3-4 days without even needing to turn it on. We are 4 in the household and it holds nearly 100liters of water. It is a kind of battery :)
- WalterBright 7y ago
  > It is a kind of battery I find it ironic that this sort of thing is so overlooked with solar/wind power on the electric grid. Consumer electricity prices should be allowed to rise and fall with the availability of solar and wind. Then, you can heat one hot water tank only when electricity is cheap, and also use that tank to heat your house in winter. In summer, a separate tank can be chilled when power is cheap, and used to cool the house. Or even simpler, a pile of rocks will work. With such a scheme, the need for grid batteries would be reduced enormously. Instead grids have the problem of what to do with the extra power when there's too much of it.
  - nunodonato 7y ago
    well.. I guess water and rocks, at a scale that make them useful for other purposes will definitely have a size problem for most people. While a battery (especially the new lithium ones) can fit in a drawer :)
    - WalterBright 7y ago
      Your dwelling, just as it is, has a lot of thermal mass that can be used as a "battery". For example, cooling it to the low end of the comfort zone when electricity is cheap, and letting it drift to the high end when it is expensive. For example, the power goes out around here often. I've noticed it can take up to two days for the house to cool down. The water in the hot water tank is hot enough for a comfortable shower for 3 days. Water/rock batteries are cheap as dirt, no maintenance, no fire risk, etc.

by abraae 7y ago

sandworm101 7y ago

Great ideas if you are dead against batteries, but there are massive downsides. Batteries are not evil or expensive, at least if you go with traditional lead-acid ones. They are a thousand times more reliable and efficient than compressed air storage. Compressed air storage has many dangers, from explosions (metal fatigue) to fire (compressing gas creates heat). The best and most reliable method of non-battery storage of energy is the traditional water tower. It used to be standard practice for buildings to maintain water storage tanks on their roofs. Mate a water tank with some solar panels and you can create an energy storage system without heat, high pressures, chemicals, high voltage or even moving parts (the pump has only one moving part).

adrianN 7y ago
Lead-acid batteries die after only a few hundred cycles.
- mgiampapa 7y ago
  No they don't. Case in point, I live off grid with a 24v system composed of 2v lead acid marine batteries. They were 2 years old when I got them and have put them through over 1000 days of use since. Mind you, I don't discharge the system past 23.5v ever, and I check my electrolyte levels weekly adding distilled water as needed, but lead acid are cheap, effective, long lasting, and recyclable with minimal effort. The only thing against them is maintenance, and they are big and heavy. My house doesn't seem to care.
  - ledauphin 7y ago
    I appreciate the anecdata, but do you have an actual cycle count on the batteries? It's not clear to a non-expert (me) how you've disproven the GP.
    - extrapickles 7y ago
      The cycles you get is dependent on the depth of discharge (and more). See the chart in [0], where 100% discharge nets 200 cycles, 50% gives you ~500, 30% is ~1200. One would expect that if you discharge 50%, thats half a cycle, and therefore get 400 cycles, but in reality you get 500. [0]: https://pvcdrom.pveducation.org/BATTERY/charlead.htm https://pvcdrom.pveducation.org/BATTERY/charlead.htm
      - ben_bai 7y ago
        Lead batteries can be rejuvenated, with a device mostly called "A pulser/desulfator/refresher" Short story: I had a completely dead 12V car battery. It was at 0V and would not accept a charge at all. Connected it to a bench power supply and slowly cranked the voltage up until it charged with a couple mA @ 30V. Slowly it accepted more amps so I constantly dialed the voltage down until it was charging at 14volts. Then hooked up the desulfator and left it for couple of weeks. Every other day checked voltage and hooked it up to a charger for couple hours. After that it was perfectly able to start my car(oldtimer) again.
        Spare_account 7y ago
        This kind of work requires a supply of power though, which is something of a catch 22 if the battery you are rejuvenating is your power source. That said, this thread has descended from a comment about apocalyptic scenario planning and this general principle of maintaining batteries makes sense. Learning how to build and repair lead acid batteries doesn't seem to be beyond the realms of possibility.
        mgiampapa 7y ago
abdullahkhalids 7y ago
Pumped hydro storage is great. The difference between it and batteries is that batteries can be constructed off site by a third party and then transported to your location. Water towers have to be built on site, which can be difficult. Not to mention, to get appreciable storage, you have to build a really tall tower or a really big one. This is difficult too. Especially if you are in a location where the soil shifts or you get high winds. Because now your tower has to survive the elements. There is definitely a strong case against water towers for distributed energy storage.
- sandworm101 7y ago
  Conversion to or from electrical power is one option, but an elevated water storage (tower or simply up hill) reduces the need for larger water pumps. It means you don't have to run your well during dark hours. So it saves on electric use rather than provide actual electricity.
- _iyig 7y ago
  Why not dig a pit? You can even load a big mass on top of the water for extra potential energy. Similar system from the age of steam: https://youtu.be/aKmi0PN7LxM https://youtu.be/aKmi0PN7LxM
abraae 7y ago
I'm not dead against batteries, we've got an off grid cabin that runs on 4 6v Trojan lead acid batteries and they are great. However there's something about living off grid that makes one want to simplify, and batteries are one of the big, expensive, and limited life time components of a solar system. If you can reduce the load on, and the required capacity of your battery bank, then you have improved reliability significantly. As you say, pumped hydro is certainly a great storage system if the situation permits. It just takes a very large storage system to store as much as batteries. If you have a pond or lake and an easy supply of water it would certainly be my choice.
- jefftk 7y ago
  > batteries are one of the big, expensive, and limited life time components of a solar system On the other hand, so is a big chest freezer!
happosai 7y ago
A lot of the household energy load is either heating (water, cooking, surviving winter) or cooling (fridge, feeezer, surviving summer). You don't have to be dead against batteries to see a lot of potential in using thermal energy storage to decouple renewables energy sources from energy use.

dclowd9901 7y ago

I don’t think a good solar electric hot water system would ever work if it was running only when the sun was shining. It takes _so much energy_ to get water up around the requisite 110+ degrees, that even a very efficient storage system wouldn’t benefit it all that much. Honestly, the best solar powered hot water system is a black plastic bag full of water in the sun. Anything else will require a battery bank at minimum.

abraae 7y ago
Depends on the size, but if you have even a modest size solar system you should be good. On a sunny day, a 2kw solar system can drive a 1kw hot water cylinder to full temperature easily. And to avoid legionnaires disease - a risk of inadequately heated water - you only need to drive the temperature up high from time to time, not continuously. Once a day is plenty.
jdmichal 7y ago
Don't use solar PVCs to heat water! Solar water heaters are much more efficient than PVCs. Even the lowest-efficiency system listed is 46%, compared to 19% for standard solar cells. https://en.wikipedia.org/wiki/Solar_water_heating#Energy_production https://en.wikipedia.org/wiki/Solar_water_heating#Energy_pro...
- nullc 7y ago
  Ignoring equipment cost, in many climates PV + a heat pump would outperform a plain solar water heater. :) [Silly to ignore equipment costs, sure, but if you have other uses for PV power ... using PV for heating water isn't necessarily nuts.]

nunodonato 7y ago

I do something similar to that. Living off-grid and my solar setup is quite small (1.6kwh of solar panels and a bunch of batteries). However I depend on electricity for most things, including cooking(induction) and hot water (electric water heater/tank). So in sunny days I let the water tank heat as much as possible(usually around 70-80C), and can go 3-4 days without even needing to turn it on. We are 4 in the household and it holds nearly 100liters of water. It is a kind of battery :)

WalterBright 7y ago
> It is a kind of battery I find it ironic that this sort of thing is so overlooked with solar/wind power on the electric grid. Consumer electricity prices should be allowed to rise and fall with the availability of solar and wind. Then, you can heat one hot water tank only when electricity is cheap, and also use that tank to heat your house in winter. In summer, a separate tank can be chilled when power is cheap, and used to cool the house. Or even simpler, a pile of rocks will work. With such a scheme, the need for grid batteries would be reduced enormously. Instead grids have the problem of what to do with the extra power when there's too much of it.
- nunodonato 7y ago
  well.. I guess water and rocks, at a scale that make them useful for other purposes will definitely have a size problem for most people. While a battery (especially the new lithium ones) can fit in a drawer :)
  - WalterBright 7y ago
    Your dwelling, just as it is, has a lot of thermal mass that can be used as a "battery". For example, cooling it to the low end of the comfort zone when electricity is cheap, and letting it drift to the high end when it is expensive. For example, the power goes out around here often. I've noticed it can take up to two days for the house to cool down. The water in the hot water tank is hot enough for a comfortable shower for 3 days. Water/rock batteries are cheap as dirt, no maintenance, no fire risk, etc.