Energy Harvesting and conservation techniques

[large_ghostman]

Hi, We are doing a ecology type theme at school, and I a doing an assembly. Mine is part based on something dad is doing, part of it involves energy harvesting (there has been alot of posts on here lately about that sort of thing),
I havnt ever realy considered power consumption of my projects before. I rarely if ever do battery ones, and dont really pay attention to how much energy a circuit uses. But I have been playing around with some the kits dad has for his project. Its been a real eye opener!!! staggering what can be done with nA's and the odd burst of 1mA! What shocked me most was putting one of my projects on a test bed, all it does is read a humidity sensor every 15 seconds.
It runs at around 200mA with burst's of around 300mA while reading!! that dosnt sound like much to me, That was until I put the same sensor onto one the energy micro 32 bit boards!!. Even with a very clunky program I dropped it to around 10mA, using there program example tho, I can read the same sensor and run it off a TEG at around 100uA. But the have an example that uses some clever sleep techniques and that draws 4 nA most the time with a couple of bursts of 10uA AND displays a segmented display continuously!!!!
So in light of this, I am going to see what I can get done for an assembly in 2 weeks time, the idea is to get the dev board to do something semi interesting and run it from a TEG and small cap bank.
What I was wondering, seeing as there has been a few posts on energy harvesting etc, how many people spend alot of time getting there code etc tight? and pay close attention to energy used? I think pics are way behind in this regard, yes ok the 32 bit chips can be monitored in real time using REAL ICE and a special header, but generally pic's dont have this function, having seen it in action I am surprised its not a feature. Watching the code live against a graph showing voltage and consumption, really helps. You can the scroll back and place the cursor on the energy peaks and it shows the code line, that was running.
As more and more battery apps become the norm and more energy harvesting is used, I can see this being a big thing for the future. So what are others views? TOY or TOOL??.
Just interested in a discussion with the pro's, on the advantages and disadvantages of these systems. and views on the future of energy harvesting from small sources

 

[Dr_Doggy]

hi, just a TOY unfortunately, but a great school project, demonstrating the use of natural sources, when you are mentioning these energy harvesting devices i am presuming that you are referring to things like the TEC's (therm-electrics) that run off body heat, or those things that crank when you bend your leg. the problem is that the energy that feeds these devices needs to come from the body, and digestion is not the most efficient process to supplement that said energy. maybe the spring in the sneaker would work, since gravity is what pulls down otherwise better off with battery and solar panel.

there was a funny little toy that scored a deal on the dragons den, one of those FAKE free energy circuits even, where there was a LED wired to a solar panel and the LED pointed to the solar panel so the energy coming out of the LED feeds back to the panel. The first problem to this is the losses you have, you will always loose power in resistance of wire, inefficiency of LED and PANEL, and photons lost that didn't travel back to the PANEL. this is the same example of those bendini circuits on you tube where they are doing the same lame thing but with magnetic fields.
DIFFERENCE that made the LED circuit so sell-able was that another factor that we need to calculate, and the buyers will fail to see, is the ambient sunlight that leaks in and is the actual source of charging the circuit. but the feedback loop lasts long enough to fool.

having said all that you are rite that P=VI and the lower you can get those numbers down the more efficient your circuit will be.. and with such low numbers TEG will run it np. But while you have TEG don't forget to run the numbers, check input energy(temperature & volume), and check for output power(VI) that TEG can do all on a timeline graph, as they will all go down to 0 eventually.

but also think about a PC, they have auto standby and auto shutdown for that very reason. and if you open one up the main CMOS chip runs off a watch battery which is enough to hold the memory to that chip for what? years? (a year?)

personally i think if any of these are to take off it will be the flexy solar cells that sew in to a jacket, but they are still working on things like that too since then they need to think about costs, a funny one is the solar panel backpacks!,
example: that's great to have carbon nano tube jacket to charges phone from sun(i think nano tubes do that?), but no one can afford, or would pay, $1,000,000 for said jacket.

i personally think that solar methods, and geo-thermal methods should be ones to take off, with tech like that in every home & with precision control we could actually change climates with infrared absorptions and reflections.
but again cost and efficiency are through the roof, so its not the best investment, and im just guessing in the dark that climate control would actually work either,.. again , just my guess, who knows rite!

 

[nsaspook]

PIC controllers like most modern controllers have intensive power saving modes. Most hobbyist don't use them unless it's an application requirement.
https://www.microchip.com/pagehandler/en-us/technology/xlp/
**broken link removed**

Energy harvesting Device.

 

[large_ghostman]

PIC controllers like most modern controllers have intensive power saving modes. Most hobbyist don't use them unless it's an application requirement.
https://www.microchip.com/pagehandler/en-us/technology/xlp/
**broken link removed**

View attachment 84471
Energy harvesting Device.

Thats partly my point, Pics do have sleep modes, but unless you pay out for a REAL ICE and use a pic32, there is no way to monitor in real time how much current is drawn by each instruction. And as much as I hate to sound like I am PIC bashing again (honestly I am not), PICS are pretty low in the food chain for energy use. I am not sure how valid it is to compare a 8051 to a pic but, in that link you gave it boasts about the XLP range, its hard to compare figures as they are not given the same way. But the simple stuff like the " works down to 1.8V" sounds good, but an older 8051 has two modes one is 0.9V-1.8V and 1.8V to 3.6V, with all IO 5V tolerance and the option to up that to twice VDD.
Dosnt sound important? but its the difference between one cell operation and needing 2 cells. The rest of the figures will need a closer look because As I said they are not given the same way. However the energy micro 32 controllers blow the both of them clear out the water in regards to power saving. Again I will need to dig the info out in a form that relates. So why the sudden crusade? well it's not a crusade as such. But one day I will hopefully be designing products, and by then energy use WILL matter and matter alot, the more time goes by, the more energy saving will matter.
Electricity is getting very expensive along with batteries etc, more will need to be done yet use less power. So in a way I am paying attention now rather than later . Will my projects get better and use less power? unlikely for now, but for now learning is fun and not serious. Another 2 years and it gets serious, so I have 2 years to just kick back and enjoy myself , learn what I can what ever way I can until I get on the real learning train.
Maybe to older people all this stuff dosnt seem to matter, but no offense but for aot of you on here, 20-30 years then its all over, for me I hope I have at least 60 years left! so what I and my generation does now and later will matter to the generations that follow me. ^ 'I was trying to be kind' )

 

[NorthGuy]

But one day I will hopefully be designing products, and by then energy use WILL matter and matter alot, the more time goes by, the more energy saving will matter.

That would mean abandaning loops-inside-loops programming style in favor of sleeping and interrupts

 

[nsaspook]

Thats partly my point, Pics do have sleep modes, but unless you pay out for a REAL ICE and use a pic32

If you have REAL ICE this works on almost everything but you don't need fancy tools to do basic power tracking.
https://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=AC244008

The MPLAB REAL ICE POWER MONITOR enables designers to identify and eliminate code that consumes high current, in real time. Combined with the MPLAB REAL ICE in-circuit emulator and MPLAB X IDE, this development platform allows users to measure, graphically profile and optimize code power consumption for all of Microchip’s more than 1000 8-bit, 16-bit and 32-bit PIC® microcontrollers. Additionally, it offers unsurpassed micro-Amp current measurement, with an overall dynamic range up to 1 Amp, and a voltage range of 1.25V to 5.5V, making it ideal for a broad range of battery-powered, digital power-supply, motor-control and metering applications.

Remember:
Crusades are great motivators but are often misguided paths to the future.

 

[large_ghostman]

That would mean abandaning loops-inside-loops programming style in favor of sleeping and interrupts

Hmmmm, ok sod it! I will keep loops and just use a car battery for my designs , actually the power saving is pretty cool for some stuff, I have a led thats smd and easily seen blinking away at 1mA, I aso have it blinking and only using 200uA (ive used sample code for that).
Its alot of fun for now,maybe I will never have to design a battery device! maybe I will get to only design them, either way makes sense to have a go

 

[large_ghostman]

If you have REAL ICE this works on almost everything but you don't need fancy tools to do basic power tracking.
https://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=AC244008


Remember:
Crusades are great motivators but are often misguided paths to the future.

I didnt know it was for all chips!the bit I read only said 32bit, stll its a hefty price all the same, with EFM its built in and free (ok no such thing as free, but you know what I mean).
interesting stuff! one thing I do prefer with pics is the dip packages these efm chips are tiny and alot are BGA (yuk)

 

[4pyros]

Well for certain applications energy savings, not so much harvesting is a must.
I remember reading somewhere about a collage project for long term battery usage for a weather station or something.
One team was able to make it last ten times longer than all the others but it took ten times longer to program.
I just wish more developers would do this with phone apps!!!

 

[large_ghostman]

I know its all cost related etc, but when I was talking to dad about it he said we use way less power these days than we used to, I thought he was mad because when he was young there wasnt many appliances. No X box's mobile phones etc.
His reasoning though is back then, he said colour TV's were left semi switched on all the time, they had to be warm to work, and if you went near them you could feel the heat, but he says now you get huge colour TV's that use 100W or less, and the same with washing machines etc.
So my thinking is, as electric keeps going up, then you will reach the point were its possible to be off grid and worth while, or there will be a day when we have two power circuits in a house, one low power for LED light etc, and a higher power one (240V). At the moment the 7 segment display on our new cooker cost is low enough that it out ways a low energy LCD that uses many many times less power but costs more. But what happens when the cost finaly gets outwayed by the saving.

I have probably been as clear as mud, but what I am saying is, in the future we might reach a point where its possible to power small things with energy harvesting, like we have a small TEG in the cold frame, the warm side is out side the box with a heat sink on, the cool side is in the box, it produces enough to power the control system in the green house, when its at max it stores some in a cap bank, for when its not so good.
This is a trial thing for something else, but so far in the 4 weeks its been working, its worked well. Not useful as is, but it isnt going to be used like that.
It does show though that alot can be done with very little power.
We are doing energy harvesting at school, this is mainly because wind farms are everywhere here! and they are trying to make them sexy to us. But I cant help thinking there is a better way to make a wind turbine

 

[4pyros]

or there will be a day when we have two power circuits in a house, one low power for LED light etc, and a higher power one (240V).

This has been done for years in recreational vehicles like boats and campers.
Also in houses in the northern parts of the US, lots of snow, ware they can lose grid power for months at a time, they have battery back up.
Look up off grid living.
It will not become main stay where cheep reliable grid power is available.

 

[large_ghostman]

thats just it, grid power in the uk is not cheap, we dont live in the middle of nowhere as such, but we have no end of power cuts! 23 since end of July, most are less than 12 hours. But its enough that it wouldnt take much for off grid to be a better option.
Sometime this year we are getting solar water system, and the wood burners are going to have back boilers on. We own a wood so it makes sense to use it for hot water and heating in the winter, solar in the summer.
If you think about it we use less electric now but we pay more. That wont change, I have no idea what the cost is in the USA, but here its totally out of control. When we had the farm 3 years ago dad paid around £2000 a month in electric, just before we left that had gone upto around £2900 a month, yet we were using less and less.
Its one reason we sold it in the end, dads family had owned it for nearly 300 years, he is still really sad that he was the generation that was the last there. Our house was 500 years old in parts, but its now going to become flats, and the barns are going to be converted into housing.
It must really hurt dad, I am pleased we left, it was killing my dad and I would rather have him than the farm.

 

[NorthGuy]

So my thinking is, as electric keeps going up, then you will reach the point were its possible to be off grid and worth while, or there will be a day when we have two power circuits in a house, one low power for LED light etc, and a higher power one (240V).

We have already reached this point here. Low voltage LED circuits are not a good idea though because of much higher losses in the wiring.

 

[large_ghostman]

We have already reached this point here. Low voltage LED circuits are not a good idea though because of much higher losses in the wiring.

Thats interesting, I assumed higher loss with 240V. Each LED needs to be dropped and has to have half cycle protection? so wouldnt a 12/5V circuit be better?
I dont get the higher loss? or is it distance to each house? My idea assumes each home making its own low voltage energy. I know solar is obvious choice but I hope we are missing something out. My concern is not only the use of a resource (oil) past peak point but also the rise in cost.
I am working on the assumption of falling technology cost as well, Dad has a ancient maplin catalog from 1980!!! in it there is two types of LED, RED which is £1.08 and the new green ones lol, that are £1.27 each! these are 5mm Leds nothing special. now he says he knows back then that a pint of beer was 48p a pint.
so working on an assumption that beer is now £3.20? a pint, they used to cost over 2 pints, or in todays beer over £6 each!!!
OK so not reliable, but technology gets cheaper. Maybe another 10 years or so and it will be worthwhile every home making at least some of there power

 

[NorthGuy]

Thats interesting, I assumed higher loss with 240V. Each LED needs to be dropped and has to have half cycle protection? so wouldnt a 12/5V circuit be better?
I dont get the higher loss? or is it distance to each house?

You won't produce your power at 12V, so to get 12V you need to down-convert. The efficiency cost of DC-AC followed by AC-DC conversion (assuming you're making AC for your water pump etc. anyway) is just slightly worse than direct DC-DC.

However, the wire loss is I^2*R. R could be quite substantial if you run it from your power plant and then all around the house. To transfer the same energy at 12V you need I 20 times more than for 240V, so your wire losses become I^2 = 400 times higher. If you lose 100mW with 240V, you will lose 40W with 12V, which is 1kWh a day or 360kWh/year.

And if you go 5V (good for LEDs), it'll be not 400, but 2300 times more losses (if you ever get 5V at the LED end) and your 100mW loss becomes 230W or 5.5kWh/day - enough to power a small house!

so working on an assumption that beer is now £3.20? a pint, they used to cost over 2 pints, or in todays beer over £6 each!!!

If you judge by the price of gold, the beer got cheaper too. Just don't tell this to those guys at the pub

 

[large_ghostman]

Nicely explained! So what is the answer? apart from depends what the output voltage is of the producers. Have a high voltage go to nodes that then drop the voltage? Say room by room?? I know its all just theory but its an interesting problem, and I honestly think it will matter alot one day.
We have small generators, and will get bigger ones this year. But some of it could be done by other means, ok it may not be practical and certainly not cheap, but take high power leds, they burn up and over heat unless in free air, what if some of that heat was used to power a TEG? The one I have played with would make a great heat sink cooler! and would give a small amount of power back.
I used dads coffee to power it and it cooled it very quickly! would make a good Led cooler but they are not cheap enough yet to become heat sinks.
LCD is another good saver, but cost needs to drop. I have a small 128 segment lcd that uses less than 500uA, when I look around at things like the cooker and fridge and washing machine, I cant help but think, if these were used world wide in appliances then the total global energy use would fall a fair bit.
But then you have the cost of manufacture and power used to produce to factor in. So all in all its very hard for me to work out, what looks cheaper from what actually is cheaper. One thing that haunts me and makes me think we are doing it wrong, I live in a very beautiful part of the uk. Its really special it has a dark park status, the hills etc are really awesome, but they have started sticking wind farms up all over the place!!! when we moved here last year, from the house I could see 11 wind turbines in total from the top floor. Now I can see 47!! They are ugly and kill bats, but what gets me is, apparently they use more power to make and install than they will produce!!
So I dont get why they are used???

As for the beer thing, dad was about 14 and it was the only price he could remember from all those years ago .
So beer became the comparison . Still makes you realise how much Leds have dropped in price, and looks like back then a choice of only two colours! NO RGB leds!!.
Anyway I am going to blog my school projects, I never get around to posting details of the stuff I finish, I want to change that. I manage to finish a fair amount of my projects, would be nice to look back at some of them. So this year a vow to blog more

 

[4pyros]

Most of the residential low voltage systems I have seen use 24 volts or even 48 volts, so they can use smaller wire and keep losses down.

 

[4pyros]

I have thought about running 24 volts around my house from solar and stepping it down as needed to replace all the wall warts that stay on all the time.
Have you hard of vampire power suckers?
https://electronics.howstuffworks.com/everyday-tech/vampire-power.htm

 

[large_ghostman]

That seems to make more sense to me, especially for a low voltage system based around each house.
One thing I should mention, I am lucky I live in a large house with no one near by. So I am looking at it from that perspective, we have 20 acres to stick stuff and not just a small roof on a house, so alot of it wouldnt be suitable for say a small house in a town. Some would still apply though, and the idea of TEG's as lighting heat sinks makes alot of sense to me, Leds produce a great deal of heat and get life limited by overheating, most places you want light dont have alot of free air, so they get too hot, using a heat sink that moves alot of heat and gives a return in power is a good idea, I will try it out on a high power Led see how much cooler I can get the led to light. If the TEG's were cheaper it would solve the LED heat problem nicely, far less waste by using the heat produced to make power.
I have been looking at homemade solar water heaters, this I am going to try out on my shack this year !

 

[large_ghostman]

No I will look at the vampire thing