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I am starting this thread to document my progress with this project. I am also copying my first post on the subject 18/02/07 to this thread to give the background. Peter

Saving the waste heat.

I am actually doing a Prius thermos mod to one of my Insights as we speak. I shall keep you all updated with a full write up later.

The Prius Thermos fitted to some of the models in colder climates basically saves hot engine coolant between runs and dumps it into the engine on the next cold start, reducing warm up time and improving economy etc. It has been discussed on here before, but I don't think anyone has actually done it yet Until now that is!

As the Prius Thermos is impossible to get in the UK, I am using a 3L Emsa President pump pot stainless steel vacuum flask, This is an excellent model with some useful fittings as you can see from these few pics. I have a pump, and am now waiting for a 3 way valve to help finish the sytem.

I carried out some heat retention tests with the flask, and when filled with 95C water it was still above 45C 3 days later, about the same performance as the Prius flask.

I was saving this, but I will let you in on some of the details now.

My test system will be very simple with one thermometer showing the temp of the coolant in the flask. The pump and valve will be controlled by a simple push to make switch and one minute one shot timer.

Operating sequence is this, get in car on cold morning, check thermos temp on gauge, if hotter than ambient press button to transfer contents to engine. When you stop engine after your run press button again to transfer hot coolant from block to thermos. Easy. This can also be done automatically later with a simple circuit.

Here are a few teaser pics.
http://www.solarvan.co.uk/insight/Thermos01.jpg
http://www.solarvan.co.uk/insight/Thermos02.jpg
http://www.solarvan.co.uk/insight/Thermos03.jpg
http://www.solarvan.co.uk/insight/Thermos04.jpg

These two pics show how the Prius system works.
http://www.solarvan.co.uk/insight/Preheat.jpg
http://www.solarvan.co.uk/insight/Storage.jpg

These two pics show a crushed Prius thermos. (Thanks to Mike Dabrowski)
http://www.solarvan.co.uk/insight/crushedpriusflask.jpg
http://www.solarvan.co.uk/insight/cutopenpriusflask.jpg

I am also incorporating a low power 12V heater in the flask to help maintain the contents temperature. The could be run from the mains like the Insight block heater but would be hundreds of times more effcient. Just a few watts would maintain the temp in the flask, and 12v is a lot safer outside than 110v or 240v here in the UK. You could power this heater from a solar panel in the summer

Anyway I am away on hols next week so probably be at least a month before system is up and running, a lot depends on finding a suitable three way valve.

Peter UK
 

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Discussion Starter #2
Thermos Modification Update 030307

I should shortly have all the parts for the mod, Mike Dabrowski has kindly sourced me the three way valve and coolant pump from a Prius. I have been busy with the thermos incorporating a few things into it.

This was the original thermos purchase.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0077756153

Temp Sensor.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0088320553
I have already dissasembled this item and incorporated it into the thermos outlet assembly, so that the sensor gives a central coolant temp. The sensor itself is the sharp pointy thing in the pics.

12v 200w Water Heating element.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0089910606
Ditto as above this is now incorporated into the thermos outlet assembly.
Not quite sure if I will use this, but wanted to incorporate it anyway at this stage.

The thermos outlet assembly sealing is the tricky part, I have modified and used the original thermos pump outlet with the temp sensor and heater added to it. The thermos water inlet and outlet are 10mm ID. I potted the temp sensor and heater in resin to make it all nice and strong. I am using the original thermos top mounting M4 bolts, making a plate to compress the rubber outlet seal with the addition of a very HQ 250C+ temp/antifreeze stable flexible sealant.

Here are a few more pics.

http://www.solarvan.co.uk/insight/Thermos05.jpg
http://www.solarvan.co.uk/insight/Thermos06.jpg
http://www.solarvan.co.uk/insight/Thermos07.jpg
http://www.solarvan.co.uk/insight/Thermos08.jpg
http://www.solarvan.co.uk/insight/Thermos09.jpg
http://www.solarvan.co.uk/insight/Thermos10.jpg

I will be using my electric tyre pump set to (15psi) and thermos filled with water to hydraulicaly test the seal. I remain confident at this stage it can be made to work. Option two is to fabricate an inlet/outlet assembly in Stainless steel, and use low temp silver soldering techniques to join the two.

I am thinking about phase change materials as well, and have bought a few bits to experiment with ;) I'll keep you posted.

Peter
 

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Nice work Peter. I'm assuming that you would use the 12 volt heater to boost the stored fluid temperature using solar?
 

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Discussion Starter #4
Solar Possibly!

b1shmu63 said:
Nice work Peter. I'm assuming that you would use the 12 volt heater to boost the stored fluid temperature using solar?
Possibly or it could be used like the Insight block heater, but much more efficient. Boost/Heat the coolant in the thermos with minimal losses, much higher effeciency and much safer as only 12v. A simpler discreet low cost 12v power plug could be integrated into the front grill like the Oem block heater part.
 

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Peter - thank you for tackling this and I look forward to seeing your progress. Quite elegant so far. Any idea how much weight the thermos+plumbing+fluid will add? JoeS.
 

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One working fluid to look at is paradichlorobenzene (moth balls). It's what they used to use in high school chem labs for the phase change experiement--probably don't now due to hyperactive safety rules.

But I think you will end up with wax...
 

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retepsnikrep said:
...it could be used like the Insight block heater, but much more efficient. Boost/Heat the coolant in the thermos with minimal losses, ...
Anybody game to do the math here :?:

Shooting from the hip it seems that the thermos idea is a minimal _overall_ "improvement" at best, but very drive cycle dependent. Long distance commuters probably seeing the least result, but multiple short hop drivers seeing quite a bit more. :)

Since Toyota integrates such a system in the Prius we'd like to believe there is some reasonable paypack time frame. ;) Although its added heat is time optimized during ICE warm-up making its contribution more significant than a simple caloric energy count might lead one to believe.

However, adding heat internal to the thermos can probably be "accounted" as a net loss in _overall efficiency_ vs. simple storage given energy savings vs. outlay in materials.

Peter, I think its GREAT your going to the extra effort of sharing such a modification for the many Insighters here. Just remember the more custom parts you choose the less other Insighters will be able to apply your modification (remember the "cardboard trick" ;) ). I have superficially investigated this option in years past. My problem was that recyclers here in the States had rarely seen a Prius. And the ones that had didn't have a clue as to what I was asking for.

Parts (new) from Toyota for the Prius system are around $1,000 :shock:
(Thermos, pump and valve). Additional parts that will be needed are mounting brackets, hoses and a control "system". The control system being the most intimidating for most Insighters, but in this case probably the lowest cost and "simplist" part of the mod (a couple out-of-the-box timed relays).

Sincerely,
 

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Discussion Starter #8
Comments

John and the others you make some good points.

To respond to a few. Joe asks about weight of mod, answer is I don't know yet. Probably 5-10kg all in. Lighter the better.

John

I concur the benefit will likely be with the short cycle commute. Exactly what my wife does, and the main reason I'm doing the mod. She drives 5 miles to the railway station each day, car is parked in car park and then she drives home 8-10 hours later. This is a real big hit on the mpg as the car barely gets warm, especially during the winter, and heating/demisting is poor. It has the big radiator block and this helps, but it's those first few minutes that kill the mpg.

I think adding heat to the thermos is a very effecient way of duplicating the block heater function. There will be only minimal heat loss from the thermos versus the block which acts like a giant radiator. It's safer to use this 12v heater incorporated into the unit as well.

If we do some rough calculations it seems most people use the block heater before driving for about 2 hours at 500w, call it 1kwh. I don't know what the final coolant temperature is when they drive off? can someone update us? Probably 50C+

3L of water takes about 3mins to heat from 20-95C in my 2kw kettle. Call it 6 mins at 1kw power, or a 10th of the power required by the block heater.

If you use the block heater but then don't drive the vehicle immediately the energy is probably all wasted within an hour or so as block cools down pretty quickly. Not so in the thermos ;) Also you usually can't plug the block heater in at the station car park, whereas the thermos will still benefit you on the drive home.

I appreciate the cost of the parts could be high, but I hope to do it relatively cheaply in the end. (Getting the key part a suitable thermos is the real key) The Emsa Pot looks a good choice and is available in 2 and 3L models. It's not a mod for the faint hearted, and I would expect anybody attempting to do it to use my post purely as a guide
and be fairly skilled at fiddling/experimenting. It's not a mod for the members who can't wield a spanner or soldering iron sadly.

Keep your thoughts coming.

Peter
 

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Re: Comments

retepsnikrep said:
I think adding heat to the thermos is [a] very effecient ...
Agreed, particularly for the drive cycle your using.

Hopefully the MPG improvement you will achieve will be significant and encourage other Insighters to follow in your footsteps. Using off-the-shelf recycled Prius parts will give the mod more mass appeal. :)

Sincerely,
 

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I like the idea so much I bought a couple of thermos bottles. Total cash outlay so far about 20 dollars. I'm hoping that I can find suitable fluid control valves from a washing machine, that can be modified to work on 12 volts. This could be something like, unwinding the bobbin, cutting the wire into three lengths and rewinding it with the wires in parallel. I have already used these valves to build a control system for our winter/shallow well which allows variable water flow rate depending on the depth of water in the well. I am counting on Peter's groundbreaking work to show the way.

As for payback, I do think that Toyotas heavier dependance on hybrid batteries makes this even more important for the Prius. Nevertheless, anyone who has started a car in a frozen parking lot without the benefit of a block heater plugged in, will understand the mental and physical benefits of such a system. It may actually save a little gas and extend the life of the gasoline engine too. ;)

I admit it's a project for gearheads, geeks, and techno-enviro-Edison wannabees. There I go, talking about myself again! :D I'm hoping that if a few of us build them we can get it down to a simple shopping list and a photo tutorial, so all those interested can clone it.
 

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Discussion Starter #11
A few more photos.

Work is still progressing, but like any project everything takes 4 times longer than you think.

I have now sealed the Thermos and tested it to 15psi with air, seems OK. I shall increase the final hydraulic test pressure with hot coolant to 20psi to give me a slight margin over the Insight radiator pressure cap which is 14-18psi rated.

I machined a round plate to coincide with the original thermos fittings, with the original rubber seals and a quality high temp silicone combined with the clamping action of the plate, a good seal seems to have been obtained.

http://www.solarvan.co.uk/insight/thermosupdate1.jpg
http://www.solarvan.co.uk/insight/thermosupdate2.jpg
http://www.solarvan.co.uk/insight/thermosupdate3.jpg

I have used extruded foam to fill/insulate the top of the thermos and help anchor everything in place. I had only just applied it in this photo, once cured I will trim, sand and paint it to give a neat finish.

http://www.solarvan.co.uk/insight/thermosupdate4.jpg

If the seal fails in my final pressure tests it means plan B will be required which is basically silver soldering a fabricated stainless outlet onto the thermos. Fingers crossed :)

Peter

PS Yes that is a tyre valve in the pics. I used that with my tyre inflator to test the seal.
 

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Update 20/04/2007

Dear All. Progress is still contnuing. :)

I have trimmed expanding foam from top of flask. Looks OK.

http://www.solarvan.co.uk/insight/thermos20040705.jpg

I have also tested thermos seals now with 95C water. Seems OK.

http://www.solarvan.co.uk/insight/thermos20040701.jpg
http://www.solarvan.co.uk/insight/thermos20040702.jpg
http://www.solarvan.co.uk/insight/thermos20040703.jpg

Also tested thermos internal 12v heater, worked well. Raised stored water temp 10C in about 40mins.

http://www.solarvan.co.uk/insight/thermos20040704.jpg

I have decided on a location for mounting the thermos, it is going in virtually the same place as on a Prius, under the headlight behind the fender/bumper where the resonator box is currently mounted. (The Resonator is a very light item and can easily be relocated.)

There is a massive space in this location with the resonator out of the way.

The resonator mountings are attached to the chassis and will provide a strong support for the thermos.

I have choosen this location as I think it's important to keep the thermos low and below the header tank level/cylinder head at least, to prevent it developing air locks.

I have decided not to cut into the heater pipes at the back of the engine to plumb the system in, as they are difficult to get at and quite specialised.

I am thinking of the oil cooler circuit or the Throttle body heater circuit both of which are at the front of the engine and easy to access from the thermos position. Any other ideas?

The Prius three way valve and pump are enroute from the US. The pump has some mounting damage but can be clamped easily enough with a rubber mount, so I am not worried about this.

http://www.solarvan.co.uk/insight/pumpandvalve.jpg

I have another strange idea to finally secure the thermos in position and give it some more insulation. ;)

I have been looking at the proposed mounting area and reckon I can seal all the gaps around this space. The expanding foam is then looking good again, it's very light, will help add insulation and stabilise the thermos in this cavity under braking etc. I think it can be totally encased in foam and the entire mounting space behind the bumper/fender filled :D

Mad? :evil: I can spray silicone lubricant where I do not want the foam to adhere (The headlight underside etc.)

I am on holiday again for a couple of weeks. More progress soon I hope. I am currently measuring the time for the heat to disipate from the thermos now it is sealed with pipes attached.

Regards

Peter
 

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Thanks for the update and Insights such as low mounting the thermos. :D
 

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Thermos Timer Control

A quick update about the Thermos control circuit.

Simplicity is the idea here. Basically the Thermos valve and pump will be controlled by a simple 555 timer circuit activated by a push button. The circuit is adjustable, so I can test how long it takes to transfer coolant too/from thermos and set timer accordingly. I think about 15-20 seconds will be about right.

http://www.solarvan.co.uk/insight/Timer01.jpg

It's built on veroboard and costs about $1.00 ;)

http://www.solarvan.co.uk/insight/Timer02.jpg

In the circuit shown I replaced R1 with an adjustable 5M pot, and replaced C2 with a 4.7uf 16v component as these control the timing interval. When activated the circuit drives the output at pin 3 high, this is connected via an led to a 12v relay which can switch the few amps needed by the pump/valve. When the time interval has elapsed it turns off. I simply need a 12v feed to the circuit. I intend to mount the led and micro push button in the blank left switch position shown below. I might put the LCD thermos thermometer readout here as well if I can make a neat install.

http://www.solarvan.co.uk/insight/Timer03.jpg

Why activated by a push button, and not simply when ignition is turned on/off? Well I wanted to retain control, and there a number of scenarios where you may not want the thermos to activate, i.e. just stopped for a few minutes, thermos temp lower than block temp etc etc.

I could make a super duper CPU controlled thingy but why bother? Just activate cicruit when you get in car in morning before starting to transfer hot coolant to engine etc. When you stop it later at end of commute, activate circuit on leaving car to store hot coolant. My wife can manage that ;)

Peter
 

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Re: Comments

retepsnikrep said:
I concur the benefit will likely be with the short cycle commute. Exactly what my wife does, and the main reason I'm doing the mod. She drives 5 miles to the railway station each day, car is parked in car park and then she drives home 8-10 hours later. This is a real big hit on the mpg as the car barely gets warm, especially during the winter, and heating/demisting is poor. It has the big radiator block and this helps, but it's those first few minutes that kill the mpg.
That's what they make 20 year old, subcompact, $500 junkers for. You buy an old small car that is known for longetivity, though not for creature comforts or attractiveness. For example, I picked up a 1988 Toyota Tercel hatchback (1.5L auto) for $600 with only 39,000 miles on the odometer (not 139,000). It needed brakes and an exhaust pipe ($400). It was also ugly as sin. I drove that car for the next 40,000 miles needing only brakes (twice) and a wheel bearing. I sold it again for (drumroll) $600.

My point is that for a total of 20 minutes per day of commuting, a junker isn't likely to wear out any parts or need any maintenance at all. Give it an oil change every year and check the fluids every couple of weeks (for leakage). Plus, nobody will steal it at the station. Think how little gas you are saving in your 2,500 mile per YEAR driving. A subcompact that gets 25 mpg city vs your 50 mpg or so in the Insight is a difference of 50 gallons of gas per year. That's 1 gallon per week.

Don't get me wrong, this is a great project, but I don't think YOU will see any meaningful savings because of your situation. I see savings for the person who drives locally all day and makes dozens of stops.
 

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Ogregev

It's not all about savings though, it's a hobby for me and I'm not that bothered about the money. It's about doing the install, designing it, making it work, sharing it with others and the satisfaction that comes from adding another few mpg to my LMPG. I actually think On my wife's commute it will make a considerable difference, certainly to her comfort on cold mornings. We shall see. ;)
 

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Hmm that's interesting, but too expensive if you include shipping to UK and customs etc.

I pound was stronger I might have considered it.
 

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