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
Quote:
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.
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.
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.
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.
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.
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.
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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2002 Silver MT, MIMA, FAS, hand throttle, lmpg 77.7
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Two Corbin Sparrow EVs
1965 Saab EV Conversion
2012 Mitsubishi iMiEV
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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.
...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
(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).
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.
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.
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! 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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Kip Munro
The laws of physics don't need changing, but rather our attitude and values. 72.8 LMPG
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Insight Thermos Modification
I'll keep you posted.
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.
