Urine powered generators

Merry Christmas
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Besoeker

Senior Member
Location
UK
It does simply flow downhill, with occasional exceptions where a lift station is necessary. The lift station is nothing more than a surge tank that is pumped when a predetermined level is reached, but once pumped, the water begins to flow again with gravity being the only force making it move. At some point a treatment location is reached, but until then most movement between user and treatment facility is by gravity.
What if the treatment works is at a higher level than the source of the waste water/sewage?
 

Haji

Banned
Location
India
tallgirl:
Ah of the battery can vary depending on the adopted rate of discharge in the field. Lower is the rate of discahrge, higher is the Ah capacity up to a limit. So it may not be possible to predict from the remaining Ah capacity of the battery whether the deep discharge limit of the battery has already been reached or not. But from the KWH rating of the battery it may be possible to predict it.
 

kwired

Electron manager
Location
NE Nebraska
What if the treatment works is at a higher level than the source of the waste water/sewage?
That is what lift stations are for. They don't convey the water all they way to final destination, they just lift it to higher elevation and then gravity takes over again.
 

Besoeker

Senior Member
Location
UK
That is what lift stations are for. They don't convey the water all they way to final destination, they just lift it to higher elevation and then gravity takes over again.
If you look at large parts of the south, say Louisiana, there isn't much elevation change to get gravity to work for you. If Old Man Mississippi bursts its banks, the flood water doesn't go away very easily.

On a slightly more general note, municipal services for waste water transportation and treatment have to deal with huge volumes of it. Thames Water, for example transports and treats 4,000 million litres of the stuff - about 4,000 million gallons. Per day.
Getting large volumes of liquid through a pipe needs pressure (head) and, as a rule, gravity won't provide that. One possibility is to make the pipes very large so that you can get high flow with not so much pressure but that would be impractical and impossibly expensive. So smaller pipes and pumps are used.
 

mivey

Senior Member
Yes, they are correct on a number of points, but please keep in mind that they are trying to sell a product.
And what they say also agrees with people who are not selling a product but are involved in modeling and battery management research.

And no, they don't actually show the available energy (watt-hours).
They say they do and if that is the goal then so be it. Other research work also states this as one of the goals of some battery management systems.

They show a state of charge based purely on battery terminal voltage and time.
It is a little more complicated than that. Making sophisticated battery models is a little more than just reading a voltage and clock (or amps and a clock for that matter). I don't know exactly what this company is doing within their model, but I do know a good model is more than just following a simple voltage vs charge curve based on a simple voltage reading. From the bit I read, they are doing more than that.

In my earlier post, I noted some of the things that one might find in a battery management system.
 

mivey

Senior Member
So, what you're saying is that watt-hours are more accurate than amp-hours for doing all of those tasks?

Just a "Yes" or "No".
Have you stopped clubbing baby seals? Just a "Yes" or "No".

You pose an invalid question as neither amp-hours nor watt-hours does "all of those tasks". They are only part of a total package. To be accurate, either method requires supplementation. As I said earlier, for power loads we use watt-hour calculations and for current loads we use amp-hour calculations.

Now if you want to be picky, and you have a system measuring amp-hours and I have a system measuring watt-hours, I can make a battery management system that is much more accurate and versatile than you could ever hope to achieve. It is only logical because I would have more field data than you (the voltage in addition to the current and time). The point remains that neither watt-hour counting nor amp-hour counting alone make a good battery monitor because that is not their purpose. But either method can support a good battery management system.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
tallgirl:
Ah of the battery can vary depending on the adopted rate of discharge in the field. Lower is the rate of discahrge, higher is the Ah capacity up to a limit. So it may not be possible to predict from the remaining Ah capacity of the battery whether the deep discharge limit of the battery has already been reached or not. But from the KWH rating of the battery it may be possible to predict it.

That is absolutely not at all the case. Of all the metrics for "remaining capacity", the kWh capacity of the battery is the least useful.

The best model for remaining battery capacity is battery temperature, terminal voltage and discharge current. The shuntless meters use battery temperature and terminal voltage because terminal voltage is fairly linear in the non-absorption (and non-almost-completely-dead) voltage ranges with respect to state of charge. Time-rate-of-change in terminal voltage indirectly provides discharge rate as a percentage of capacity, so the discharge current can be calculated.
 

Besoeker

Senior Member
Location
UK
Time-rate-of-change in terminal voltage indirectly provides discharge rate as a percentage of capacity, so the discharge current can be calculated.
May we look again at this in the context of EVs?
Suppose, on a straight level road at 50mph, the EV needs 10kW to overcome aerodynamic, rolling friction, transmission losses. That will determine the required current. It is what it is to do the job. Not a calculated value.

Here's a picture.

Tesla03.jpg


Note the title. And figures from an EV.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Have you stopped clubbing baby seals? Just a "Yes" or "No".

You pose an invalid question as neither amp-hours nor watt-hours does "all of those tasks". They are only part of a total package. To be accurate, either method requires supplementation. As I said earlier, for power loads we use watt-hour calculations and for current loads we use amp-hour calculations.

Now if you want to be picky, and you have a system measuring amp-hours and I have a system measuring watt-hours, I can make a battery management system that is much more accurate and versatile than you could ever hope to achieve. It is only logical because I would have more field data than you (the voltage in addition to the current and time). The point remains that neither watt-hour counting nor amp-hour counting alone make a good battery monitor because that is not their purpose. But either method can support a good battery management system.

If what you have is "watts", not "amps and volts = watts", and what I have is "amps", my system will be more accurate than yours.

The half-cell reactions for batteries do not involve "watts", they involve charge. Each reaction results in 2 electrons moving from one half-cell to the other. Again, no "volts", just charge.

Pb + HSO4- -> PbSO4 + H+ + 2e- <== negative plate reaction

PbO2 + 3H+ + HSO4- + 2e- -> PbSO4 + 2H2O <== positive plate reaction

An amp is a coulomb-per-second, and a coulomb is 6.241x10^18 electrons. Multiplying amps by time gets you coulombs, which gets you reactions times two. From the quantity of reactants, you can get the total number of coulombs that are available at various concentrations (which are based on state of charge) and temperatures (since thermal energy is required for the reaction to occur). And there is are still no "volts" in that set of values.

What you need to know, to determine the remaining charge, is the stoichiometry of the battery at any given instant in time, plus a bit of Physics. That is, the quantities of reactants in the two half-cells and the temperature in which the reaction will take place, activation energy at given temperatures, etc. State of charge is the integral of "reactions so far", so you can derive reactants from that. And that is all. Volts aren't even in that equation.

If you'd like to present some Chemistry or Physics which disagrees with that, I'd be more than happy to entertain whatever science you've got to back your arguments up.
 
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tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
May we look again at this in the context of EVs?
Suppose, on a straight level road at 50mph, the EV needs 10kW to overcome aerodynamic, rolling friction, transmission losses. That will determine the required current. It is what it is to do the job. Not a calculated value.

Here's a picture.

Note the title. And figures from an EV.

Yes, I totally get that people use "power" to describe things that are "power". Forces times distances per unit time -- that's power. Power integrated with respect to time, that's energy. For the umpteenth time, point conceded.

However, you are 100,000% absolutely, completely, and totally incorrect when you go from "power" to anything having to do with the chemistry of batteries. Batteries DO NOT store "power". They store a total amount of potential charge given some set of operating conditions. Yes, there will be a terminal voltage associated with each discharge current, state of charge and temperature, but it is silly to say you "add" or "subtract" energy simply because you charge the discharge current or temperature. And yet, that's what you're doing when you base everything on "energy" and not on "charge".
 
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mivey

Senior Member
I'd be more than happy to entertain whatever science you've got to back your arguments up.
I have as much as you want. However, why don't you try addressing my arguments instead of erecting a bunch of straw-men to fight against whatever un-resolved issues you have with:
I've had this argument before...

My first argument was that you implied amp-hour counting could keep up with the battery state of charge and I said it could not. My argument also includes the fact that amp-hour counting, like watt-hour counting, would have to be supplemented to be accurate to any reasonable level except for some very specific conditions. You have provided nothing to counter that argument.

My second argument was when you disputed the fact presented by Besoeker that the energy storage capacity of a battery system is a determining factor in the potential performance/range of EVs. My argument includes the facts that we use watt-hour calculations for power loads and amp-hour calculations for current loads. You claim energy is useless and I have provided information to the contrary showing available battery energy is quite useful and even a common specification for EVs. You have provided nothing to counter that argument.

You make a straw-man argument about the accuracy of amp-hours vs. watt-hours. I have said both operations have useful functions and you have provided nothing to counter that argument.

If what you have is "watts", not "amps and volts = watts", and what I have is "amps", my system will be more accurate than yours.
Since I have to meter both current and voltage to get watts, then I will say mine can achieve better accuracy.

In another straw-man argument, you present a LA cell reaction and imply that I am arguing against chemistry. If you want any argument about LA cells, I'll just say the topic of amp-hours and watt-hours and batteries covers more than just LA batteries.
 

mivey

Senior Member
However, you are 100,000% absolutely, completely, and totally incorrect when you go from "power" to anything having to do with the chemistry of batteries. Batteries DO NOT store "power". They store a total amount of potential charge given some set of operating conditions. Yes, there will be a terminal voltage associated with each discharge current, state of charge and temperature, but it is silly to say you "add" or "subtract" energy simply because you charge the discharge current or temperature. And yet, that's what you're doing when you base everything on "energy" and not on "charge".
Well, you are wrong. In fact, NASA adds and subtracts energy in Li-Ion batteries they use and they are not so silly. The Li-Ion batteries are also valued because of their high specific energy (the Wh to weight ratio).

No argument being made in the following, but since you seem to like reactions:
Positive: LiMO2 <-> Li1-xMO2 + xLi+ + xe-
Negative: C + xLi+ + xe- <-> LixC
Overall: LiMO2 + C <-> LixC + Li1-xMO2

Also, I don't see where "everything" has been based on energy.
 

Haji

Banned
Location
India
That is absolutely not at all the case. Of all the metrics for "remaining capacity", the kWh capacity of the battery is the least useful.

The best model for remaining battery capacity is battery temperature, terminal voltage and discharge current. The shuntless meters use battery temperature and terminal voltage because terminal voltage is fairly linear in the non-absorption (and non-almost-completely-dead) voltage ranges with respect to state of charge. Time-rate-of-change in terminal voltage indirectly provides discharge rate as a percentage of capacity, so the discharge current can be calculated.

Thanks for your reply. I want to know if the KWH of a battery remains independent of the discharge rate adopted for the battery as the Ah capacity is not.
 

Besoeker

Senior Member
Location
UK
However, you are 100,000% absolutely, completely, and totally incorrect when you go from "power" to anything having to do with the chemistry of batteries.
I didn't

Batteries DO NOT store "power".
I did not claim that they do. I was very specific about that point as far back as post #10.

I'd rather you read what I posted than what you think I posted if you are going to respond to my posts.
 

mivey

Senior Member
If you are talking about the time rate of energy, you should have. But I thought the graph you posted was talking about double-quote "power" wink-wink-nudge-nudge since it was labeled Wh/mile.

At any rate, batteries do have a specific power (W per unit weight) that is a characteristic of battery chemistry and packaging.

I did not claim that they do. I was very specific about that point as far back as post #10.
We know they don't store time-rate-of-energy power but it appeared your graph was using power to mean energy.
 

mivey

Senior Member
Well, you are wrong. In fact, NASA adds and subtracts energy in Li-Ion batteries they use and they are not so silly.
tallgirl,

I see you meant to say change instead of charge and I read that you were talking about battery charge. I will say that the available energy does change, as does the available amp-hours.

I stand by the fact that you can add and subtract energy to and from a battery.
 

Besoeker

Senior Member
Location
UK
If you are talking about the time rate of energy, you should have. But I thought the graph you posted was talking about double-quote "power" wink-wink-nudge-nudge since it was labeled Wh/mile.
Yes. Energy per mile.

We know they don't store time-rate-of-energy power but it appeared your graph was using power to mean energy.
The vertical axis is clearly energy per mile at a given rate of travel. That would allow you to calculate range from say, a 25kWh battery.
But I agree that the actual title as opposed to the axes, is wrong. Sales speak from that EV manufacturer. I should have cropped it out.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Thanks for your reply. I want to know if the KWH of a battery remains independent of the discharge rate adopted for the battery as the Ah capacity is not.

The kWh capacity of a battery is dependent on current state of charge, temperature, and rate of discharge. It is not some kind of independent value that can be looked-up on a nameplate and believed to be true.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Well, you are wrong. In fact, NASA adds and subtracts energy in Li-Ion batteries they use and they are not so silly. The Li-Ion batteries are also valued because of their high specific energy (the Wh to weight ratio).

No argument being made in the following, but since you seem to like reactions:
Positive: LiMO2 <-> Li1-xMO2 + xLi+ + xe-
Negative: C + xLi+ + xe- <-> LixC
Overall: LiMO2 + C <-> LixC + Li1-xMO2

Also, I don't see where "everything" has been based on energy.

Appealing to NASA doesn't make it true.

What you see in those half-cell reactions aren't watts. They are electrons -- those "xe-" thingies.

That means the reaction is in terms of AMPS, since an amp is a coulomb-per-second, so an amp-hour is a coulomb-per-second for 3600 seconds. You can't convert between coulombs per second and watts or watt-hours no matter how hard you might try.

The reason amp-hours work better -- and this is a "better" conversation, as well as a discussion about why kilowatt-hours are a horrible measure -- is because those electrons really do have to make their way through the circuit, even if the voltage is depressed.

When you can get a half-cell reaction that's in watts or watt-hours, you get back to me.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
I didn't


I did not claim that they do. I was very specific about that point as far back as post #10.

I'd rather you read what I posted than what you think I posted if you are going to respond to my posts.

Here's your post #10 --

Myself as well......

The stored energy is volts times amps time seconds.

The most accurate statement you can make is that it requires some amount of energy to store some number of amp-hours of charge which can then produce some number of watt-hours worth of energy under some discharge-cycle-specific conditions.

All for various values of "some", and all of which have more unknowns and variables than you can shake a stick at.

I don't have tables for my battery bank, mostly because it doesn't cycle, so I can't give you worked examples, but I can give you a thought exercise.

How much energy does it take to recharge a battery at C/10 from 50% state of charge? At C/5? At C/20? Can we agree that at 100% state of charge, the battery has the same =potential= energy?

How much energy can be removed from a battery at C/10 to 50% state of charge? At C/5? At C/20? Can we agree that at 50% state of charge the battery has had the same amount of CHARGE removed, even if the energy is different?

Finally, if we can agree that 50% state of charge is 50% state of charge, and that 50% state of charge is the same number of amp-hours, and we can agree that three completely different amounts of energy were removed using a C/5, C/10 and C/20 discharge rate, can we agree that 50% state of charge being the same number of amp-hours remaining (or required for a recharge) is more "the same" than those three different amounts of energy, either charging or discharging?
 
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