Power Generation General

[Scatty]

I was about to post a thread until I saw this one. There go my imaginary internet points again.

Has anyone else looked into whole-house UPS-style systems or cost time-shifting using batteries? My brother, my dad, and myself are looking into home battery storage for time-shift, but also to deal with the shortages that are inevitably coming in the next few years as the government continues to fuck with the grid. The idea is to be able to store enough energy for a bit over day of normal operation, which can probably be stretched to two or three days with rationing.

We're starting with a test rig at my dad's place, since he has both the time and the money to actually work on it. The initial plan is to start with time-shifting, then upgrade to some form of real-time rate management if possible (using a home assistant integration because home assistant is awesome), and then finally add solar for that fully off-grid lifestyle. We don't want to do some shitty all-in-one contractor installation, or use some tightly integrated system like Powerwall. Instead we're going start with a system that can be expanded over time. To that end, we're investigating the Victron EasySolar II inverter/charger, which has a wide range of compatible batteries and can have its capacity expanded with parallel units. If it works, we're going to pool money to upgrade our homes with the same system. I won't be having solar though. No suitable roof for it. All things being equal, we're probably setting it up within the next month.

I believe you'd want to get some "all-in-one" inverters and set things up in a grid-tied fashion with battery backup. Basically you'd have the incoming AC power going to the inverters, the batteries connected to the inverters, and the solar also connected to the inverters. The inverters would go to your house electrical panel, and they would decide whether to pass along AC, battery, or solar power.

Two important considerations:
1 - It might be worth it to buy the batteries all up front. It's tempting to start small and add more in a modular fashion, but it's best to use identical batteries that have the same wear. For example, if you add one battery now and a 2nd battery in a year, the 2nd battery will be newer and this isn't optimal. Getting the battery capacity you need can be a bit tricky, especially if you have hvac or electric heating needs. You also need to factor in at least a 30% reserve capacity. Ping me if you need any help estimating. My setup is 38KWH.

2 - Make sure that other people are having a reasonably easy time setting up the inverter to do what you want. Just because they advertise the feature doesn't mean it works well. For example, the 6548 inverters I have are technically supposed to be able to handle your setup, but a quick look reveals that people are struggling to get it working for that purpose.

 

[geckogoy]

how about that you dumb nigger

View attachment 6870263

thats a short circuit, you are lucky thats switched off or you would start a fire

 

[Oxyjen]

I was about to post a thread until I saw this one. There go my imaginary internet points again.

Has anyone else looked into whole-house UPS-style systems or cost time-shifting using batteries? My brother, my dad, and myself are looking into home battery storage for time-shift, but also to deal with the shortages that are inevitably coming in the next few years as the government continues to fuck with the grid. The idea is to be able to store enough energy for a bit over day of normal operation, which can probably be stretched to two or three days with rationing.

We're starting with a test rig at my dad's place, since he has both the time and the money to actually work on it. The initial plan is to start with time-shifting, then upgrade to some form of real-time rate management if possible (using a home assistant integration because home assistant is awesome), and then finally add solar for that fully off-grid lifestyle. We don't want to do some shitty all-in-one contractor installation, or use some tightly integrated system like Powerwall. Instead we're going start with a system that can be expanded over time. To that end, we're investigating the Victron EasySolar II inverter/charger, which has a wide range of compatible batteries and can have its capacity expanded with parallel units. If it works, we're going to pool money to upgrade our homes with the same system. I won't be having solar though. No suitable roof for it. All things being equal, we're probably setting it up within the next month.

I have that type of system. I use a pair of the “hybrid” Chinese 48V inverters, it gets charged up on cheap power at night, and discharges all day. About 40kWh of battery.
In summer it runs fully on solar power. Remember you can ground mount solar.

Rode through a 24h power outage recently with no concern at all.

The victron products are good, I have worked with those, they’re more expensive though.

I’d question whether it’s worth bothering if you don’t have solar though. Another option if you mostly
want to time shift is use an EV plus bi-directional kit.

 

[Alaina's Rotdog]

So last year I got the ECO FLOW Delta 3 plus with a 220W solar panel after being without power for nearly a week after the hurricane.

It's a long path to self sufficiency, but this was my first step. To be able to have something that could charge devices and run a fan since nowhere had power outside of driving 2 hours.

It's just been sitting on my computer as a UPS for the time being and tried running some stress tests today.

It typically stays at 91% for an emergency and ran a pot of coffee today which drew around 1100 watts and brought it down to 43%. Afterwards, I've been running my fridge, 25cuft Whirlpool French door on it since. It's been about an hour or so and we're at 34%. The fan/compressor draw about 120 watts and we have about 2.4 hours left of power.

Overall, it's a great little stop gap. I haven't had any issues with the device or ecoflow themselves but take with a gain of salt I've read horror stories.

I'd certainly like to expand my ecosystem but would hate to mix and match. I've been tinkering with the idea of getting their Dual Fuel generator as a backup backup.

 

[Napoleon III]

As far as I can see there are 4 main power sources one could utilize off the grid. Two which are likely best used in small scale for simple tasks for things like powering a house or similar and two that require a bit more effort and infrastructure but could generate a lot more power.

Really quickly it is worth mentioning the difference between power and energy in this discussion. A water heater tank will use more energy but less power in comparison to a continuous water heater. If you have batteries that can charge and discharge that much then this distinction isn't important but batteries themselves are an extra layer of complexity that must be maintained. There are many applications where this aspect is important to consider.

The first and most obvious is some kind of solar setup. I think Solar that relies on the Photoelectric effect is worthless due to its complexity and difficulty and is only really popular in order to try and match the efficiency of modern power systems. That leaves some kind of thermal solar which while less efficient is capable of generating power. Likely the easiest and therefore best way to do this is mirrors concentrating heat into water rather than sodium as sodium adds a layer of complexity. Solar can produce a decent amount of power but it is likely a smaller sort of domestic power.

A traditional steam engine relies on the tremendous volume expansion that occurs when you turn water into steam in order to create pressure which can be turned into mechanical motion. But Stirling engines exist and they can work off of differences in temperatures rather than pressure likely meaning they are simpler to make, operate and maintain. They can also be quite efficient. I see Stirling engines being the way to go for solar power rather than regular steam engines.



The second type of power generation that is more domestic is Wind power. This is probably the simplest possible form of power generation as you need very little in the way of complex infrastructure. Generators are basically just magnets rotating around a wire. Granted you need wind in order to do this and therefore you can't press a button and generate electricity. Very good form of power generation that I see being the easiest to maintain but also the spottiest.



Now we move onto the two power sources that can produce a lot of power but require a lot of infrastructure to maintain and utilize.

The less complex of the two is hydro-power. Everything about wind power applies here although rusting does present a bit of challenge as does the fact not everyone has a giant river next to them. But you can get excessive amounts of power from rivers and in the event of some kind of societal collapse rivers would be a great place to place for some kind of manufacturing hub/city. Honestly not much to say here either you have giant river you can attach a wheel connected to a rotating magnet to or you don't. If you do then you have access to a lot of power, if you don't then you don't.



This leaves the final power sources of hydrocarbons or other combustibles. I put this in the not useful for domestic category because while users here are correct that wood gas does exist and you could produce combustible fuels from biomass, such biomass must be grown and unless you have an absolutely giant farm this isn't likely to be a good power source you'd use everyday. Sugarcare or other things that grow quickly are good for this type of power but it still definitely will require a lot of land. But one thing that this power source does have is that it can store energy relatively easily. This means you could use this method to store power for when you really need it such as for winter heating or to power some important process you need to utilize semi-regularly.

I also want to point out that hydrocarbons don't simply disappear in the event of societal breakdown. Likely we won't be operating oil rigs any more but coal still exists in vast quantities. Also if you heat plastic hot enough it undergoes pyrolysis to form a kind of diesel fuel. The excellent thing about hydrocarbons is you can produce a lot of power basically anywhere as long as you have the fuel and the machinery to use it.



Overall power generation is actually quite difficult to do well. Our complex systems of coal burning and gas burning power plants work very well and replacing them to similar levels in the event of societal degradation or collapse is very difficult. I wanted to write this post to provide a framework for thinking about this problem as well as highlighting the aspects I can see that are involved.

 

[Sperg_rancher]

I put this in the not useful for domestic category because while users here are correct that wood gas does exist and you could produce combustible fuels from biomass, such biomass must be grown and unless you have an absolutely giant farm this isn't likely to be a good power source you'd use everyday

Not a lot of us have entire farms we need to power. An 8KW generator will keep most households happy, even on days with heavy AC usage.

 

[Napoleon III]

Not a lot of us have entire farms we need to power. An 8KW generator will keep most households happy, even on days with heavy AC usage.

I ran the numbers because of your post. It would take about 5.1 Kg of Methane in order to provide the energy needed to match the average daily power consumption in the US. I'd say double that because conversion ratios are not perfect which means you need something in the realm of 10Kg of Methane equivalent.

I got about 1.7 kg of Methane to match 30Kwh or 108 MJ. Then ofc you multiply by 3 since most forms of combustion are about 30% efficient.

Do you have 10Kg or about 22 pounds of biomass to convert every day for electrical generation? Keeping in mind that a lot of living tissue, even cut down plants, is water? I don't though I admit this is a little bit closer than I thought it would be. I could see doing this as a source of electricity when other sources are scarce. But I still think that anyone cut off from the power grid would be better served by something like wind or solar for most of their needs.

 

[Sperg_rancher]

Do you have 10Kg or about 22 pounds of biomass to convert every day for electrical generation?

Overcomplicating things.

https://www.homedepot.com/p/Honda-Inverter-7-000-Watt-Standby-Gasoline-Generator-120-240V-Single-Phase-with-Bluetooth-and-10-Circuit-Auto-Transfer-Switch-HP2S-EU7000/316874841

Specs: 5.1 gal
1/2 load runtime: 8 hours
5.1*(24/8) = 15.3 gallons gasoline per day, and that's only if you're constantly drawing 3,500 watts. Most households do not.

 

[God's drunkest driver]

It's possible to characterize the fuel usage of generators, they get less efficient as power drops so you wind up with a logarithmic looking curve. Mine is large and I have a crude spreadsheet that I've done just out of curiosity by watching fuel consumption when it has been running with various things happening in my household like the refrigerator, AC, lighting in use. Just keeping the lights on and a few things around the house with it is basically idle load and it's surprisingly expensive to do, so it makes more sense to cycle your generator when continuous use isn't absolutely necessary. Load reduction, for example gas or solar water heating, natural lighting (unfortunately reduces your temperature regulation ability). In any climate where it's necessary air conditioning will be the most power hungry and most frequent load you have, in the American south for example you might as well have your generator remotely started and stopped by a thermostat in your house so you can start it, run the AC for a bit, then shut it down.

All this makes a point that it makes good sense to invest in insulation and thermal regulation. Paint your house white or the lightest color you can if restricted for example, and use a thermally efficient roof like a light color metal roof, paint your shingles white, etc. If you're in a place that gets hot and very cold you wind up with competing issues; you want to tint or shade your windows with awnings during the summer to reduce direct solar heating but you want them to let sun in but not heat out during the winter, you want the white roof during the summer but during the winter any heat you can get reduces expenditure. It's a balancing act and there's no foolproof answer for everyone other than you want natural light so during the day you wouldn't be running your generator unnecessarily just to light your dark house.

The first and most obvious is some kind of solar setup. I think Solar that relies on the Photoelectric effect is worthless due to its complexity and difficulty and is only really popular in order to try and match the efficiency of modern power systems. That leaves some kind of thermal solar which while less efficient is capable of generating power. Likely the easiest and therefore best way to do this is mirrors concentrating heat into water rather than sodium as sodium adds a layer of complexity. Solar can produce a decent amount of power but it is likely a smaller sort of domestic power.

Solar-thermal has proven to be a boondoggle on the industrial scale (reflected light farms using sodium or steam) and is basically nearly impossible to implement on a household scale. You could theoretically do something like a solar water heater on steroids and use it to generate electricity, but in practice that's ridiculous. With steam efficiency scales with temperatures and pressures involved and you wind up with high pressure steam and all of the associated dangers and difficulties not to mention expense, with something like sodium you just aren't going to do it, don't even try, it's not worth it. On a small scale I'd estimate solar-thermal would be an order of magnitude more expensive than photoelectric, because it is far more expensive on an industrial scale even when you consider the degradation with time of PV panels. The only realistic application solar-thermal has is water heating; weather dependent elimination or at least reduction of the amount of energy or gas you use to heat water. Whether it is economically beneficial to try that is dependent on your climate, usage, location, etc. It could easily never pay for itself or save you a bunch of money depending on those factors.

 

[NKVD qt]

I ran the numbers because of your post. It would take about 5.1 Kg of Methane in order to provide the energy needed to match the average daily power consumption in the US. I'd say double that because conversion ratios are not perfect which means you need something in the realm of 10Kg of Methane equivalent.

I got about 1.7 kg of Methane to match 30Kwh or 108 MJ. Then ofc you multiply by 3 since most forms of combustion are about 30% efficient.

Do you have 10Kg or about 22 pounds of biomass to convert every day for electrical generation? Keeping in mind that a lot of living tissue, even cut down plants, is water? I don't though I admit this is a little bit closer than I thought it would be. I could see doing this as a source of electricity when other sources are scarce. But I still think that anyone cut off from the power grid would be better served by something like wind or solar for most of their needs.

I think it only makes sense if you have access to a large amount of waste biomass for free. For example a small farm or trimmings from an orchard or something. Or as a way to supplement solar and wind when they have a low yield.

 

[Less Nasty Old Person]

I think it only makes sense if you have access to a large amount of waste biomass for free. For example a small farm or trimmings from an orchard or something. Or as a way to supplement solar and wind when they have a low yield.

Indeed. And processing enough biomass to power your homestead is going to be a full time job. It would be far more efficient to burn it directly than trying to turn it into methane and burning that.

Self-sufficiency is hard work.

 

[Yugica]

I am no agriculturalist, but wouldn't the constant growth and subsequent burning of such a fast growing plant ruin the soil pretty quick?

As Doctor Love already put it in posts after, the ashes should contain the minerals. However the organic(think potting soil, mulch, etc.. This is the stuff that usually helps to hold moisture in the soil and also hosts microbial and fungal communities) and nitrogen(as has been pointed out too) components of the soil can't easily be regenerated this way.

The organics disappear because they get consumed by microbes(and a good chunk of it is microbes) but most of the nitrogen, to my knowledge, gets burned off when you make something into wood gas and charcoal. There are ways to add nitrogen back into the soil, like using legumes(beans). Legume plants use symbiotic bacteria in their roots to fixate nitrogen from the air which the plant then uses. Many kinds of cyanobacteria and other microbes can also fix nitrogen. There's even a kind that works with palm trees. Here's a web 1.0 page talking about that and other kinds of nitrogen fixers. In short though you can also get nitrogen from farming and composting pond scum from otherwise just mineral having water like spring water or well water.

You should be careful about what you're making charcoal and wood gas in though. If the container has potentially dangerous elements in it. Stainless steel as an example contains at least chromium(but can also contain other toxic elements) and chromium, depending on its oxidative state, is either a micronutrient(emphasis on MICRO) or a heavy metal that will poison you. To quote the wikipedia article on stainless steel:

Stainless steel's resistance to corrosion comes from its chromium content of 10.5% or more, which forms a passive film that protects the material and can self-heal when exposed to oxygen.

And

There is extensive research indicating some probable increased risk of cancer (particularly lung cancer) from inhaling fumes while welding stainless steel. Stainless steel welding is suspected of producing carcinogenic fumes from cadmium oxides, nickel, and chromium.

Stainless steel is generally considered to be biologically inert. However, during cooking, small amounts of nickel and chromium leach out of new stainless steel cookware into highly acidic food.

Very high temperatures are going to leach out chromium and other elements into your charcoal as well, the higher the temperature the more you should expect to leach out. From something like a stove top being harmless without something to aide it like certain pH ranges, to getting somewhat under the melting point of stainless steel where you should expect it to be extremely present. In a lab setting you could put that stainless steel into a vacuum chamber, heat it from some light source to that temperature range and expect after some amount of time to have coated the inside of the chamber with a predictable thickness of stainless steel over a course of time. It isn't fast, but it will happen and one should always avoid heavy metal exposure.

There's discussion of solar, hydro and diesel generators but is wind not worth considering?

Wind is pretty viable, especially in windy areas it's more reliable than solar. A better to maintain windmill is going to be a vertical windmill, they're even easy enough to make on your own. To store power for a home though sand batteries(if I'm understanding what you were talking about right) is not a good option unless you live someplace cold(Like Finland which you mentioned.). Lithium ion is cheap for the scale that a single household might need, but lithium ion batteries also break down over time. Another good option is pumped hydro which is actually amazing at industrial and civilizational scales in terms of power capacity per unit volume per dollar spent.

The problem with pumped hydro, beyond cost related to scale(small scale is more costly), is actually a problem that heat sand batteries have as well, that is that you need a method to harvest electricity from the medium. For sand batteries this is basically going to be some kind of steam turbine or stirling engine. The efficiency of which is dictated by one of the formulas for the Carnot Cycle and here's a calculator for playing around with the efficiencies of that. Pumped hydro in comparison is I think somewhere around a 70% efficiency? This is because it does not rely on heat like a heat-based engine would and so temperature plays no real role in standard operations beyond wear and damage to equipment or for the pumped hydro a loss of water(and thus energy storage) or your water freezing over.

You can also do a combination of pumped hydro with floating solar panels. The water can circulate on the back of the solar panels to keep them cool(raises efficiency) and the power from which can also be used to pump water into your reservoir. This would be considered a kind of floatovoltaic system.

My next post will cover another alternative that might be better though .

 

[Yugica]

So it doesn't seem like anyone has talked about vanadium flow batteries in this thread yet, so I wanted to throw this in. They'd be a means of power storage that works electrochemically. You can think of them like a lithium ion or lead acid battery but with the only solid parts being in contact with the medium being the casing, electrodes and a kind of membrane. Wikipedia shows them as having amazing measured stats, including up to 90% efficiency(I'm sure at larger scales that's very achievable, or in lab settings, but the more conservative 75% is likely what one should expect) and having energy densities of 15-25 Wh/L. To expand upon that, the typical US household uses 20 kWh's of power each day. This means that a household, using the 15Wh/L statistic, would only need a system containing 1,333~ liters of medium for 1 day's worth of power storage. That's a bit more over a cubic meter(1,000 liters), or something close to 1.5 cubic yards. For a place off-grid that kind of volume is easy to fill up.

The advantages of a vanadium flow cell over a lead acid or lithium ion battery is that the electrochemical components are dissolved in liquid form and are not going to form solids(under the right conditions). This means that no damage should come about to the electrochemical bits, the only wear should be on the membrane, casing and/or electrode depending on its material properties. The problem is if the two tubs of vanadium solution mix. This will cause the battery to stop working properly and it will leak energy until the casing is fixed. Then all one should need to do is some basic electrochemistry to regenerate the two individual mediums.