Thanks.
But it's not quite that good: You are assuming 100% of the 1000watts of solar energy (at equator, and normal to surface) gets transferred as heat thru the thermo-electric pile. That won't happen. There is reflection & radiation involved, so it's not likely you'd come close to 1000watts of convection per square meter. I'd guess that 40% would be optimistic. And heat flow thru the TE devices is what generates the electricity so you need to ensure the path of flow is maximized and that the TE pile doesn't just get hot---think flow.
Let's say we had a 200watt solar panel and added TE devices to cover the backside---which would be awesome!
Assuming this is a 1-sq meter panel, and assuming the most heat we could pull thru the panel is another 100watts, you'd need at least 25 TE devices at 4watts each. These TE devices would be approx. 4sq-in each, thus requiring about 100-sqin of the back panel, making them a bit sparse on the back side, but with a heat spreader, that might work. The cost of these 25 devices would be about $500.
You'd also need 25 heat sinks and some sort of fan and ducting to ensure that the back side of the TE devices are cool, thus pulling heat thru them and delivering electrical energy (it's not enough to just get these hot---it's heat "flow" that generates the electric power).
Bottom line is that you need to visualize this as you would a modern CPU heat sink with TE device topped with a high conductivity heat sink and fan attached.
To be efficient, you end up with a stack of these components.
-MT
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Kevin Pemberton
Sent: Thursday, September 20, 2012 4:51 PM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Re: 48v diesel telecommunications standby gen?
Yes, efficiency is important. this increases with temp differences. Low heat applications using solar and other heat sources would be quiet. Because of the quiet times in some locations, having a system to fall back on helped me out. Even at 4% 1 sq meter could produce 40w but the same system supplemented with a burner over 24hrs would figure out to over 140w on the low side. I find that to much time is spent in our quarter of the world thinking about efficiency, and not enough time thinking outside the box.
Think about solar A/C. Not very efficient but in the real world with such short comings, is coming of age.
When I stack the junctions I use potted junctions on the cold side. This is worst case efficient but protects the investment so is worth the loss. Controlling the heat valve controls the charge voltage and saves the heat for later use. I think all is good and did go with it. On my canoe space made the investment a worthy goal. The burner is the evening and morning fires.
Kevin Pemberton
On 09/20/2012 05:10 PM, matwete@comcast.net wrote:
Peltier junction T.E. generation is only 4% efficient...but if the $/watt is low, go for it...the last time I bought them they were about $20 for a 4watt device...not too cheap...
From my HTC Sensation 4G on T-Mobile. The first nationwide 4G network----- Reply message -----
From: "Kevin Pemberton" <pembertonkevin@gmail.com>
To: <electricboats@yahoogroups.com>
Subject: [Electric Boats] Re: 48v diesel telecommunications standby gen?
Date: Mon, Sep 17, 2012 9:53 pm
It might be time to pipe in.
If I were to use a transportation alternator I would likely use a commercial truck alternator. They are built to be abused. Second thing is the diodes used in this type or automotive alternators will withstand over 100v. For this reason I would likely change the regulator to run at the 48v charge voltage.
If I were to consider using a 3ph alternator I would consider downloading a PDF from the national renewable resource labs called investigation of self excited induction generators or something like that. I would carry it a little further and parallel the windings of the induction motor to half, or more, the output voltage.
as the air cooled diesel goes. I bought a 4000w genset on Amazon a few years back. The injector pump was jammed because it was assembled wrong. I fixed it by assembling it the way it should have been. Because of the problem, I had to replace the pump withing a year. No one was there to return the generator to. Being one cylinder it is loud, vibrates a bunch, and has never burned clean. Heat must be removed from below deck when air cooling as well. The advantage of water cooling is recovery of heat in the form of hot water.
If you would like quiet. I might suggest Peltier junctions. TE inc. in Michigan has Engineering papers to help design the system. I have built a 12v system and it cost me 250 US 150 of that was the junctions used two years ago. Because cooling water is available and the system works in heat variations as well as moving that heat. A system on a boat would be a no brainer. The heat can come from more than one source. Solar is a good choice because a meter squared of collector area in clear skys is good for 1000w of heat. When at rest solar can top the batteries. When in motion any heat source will do including a stove top burner. The system could be referred to as a solid state heat engine.
The system requires that energy only travels in one direction so diodes are needed.
Have fun and happy sailing.
Kevin Pemberton
On 09/15/2012 11:42 AM, Robert Lemke wrote:
Good thread. I am considering using a new 10 hp air cooled diesel on ebay for $619 and (4) automotive alternators to charge a 48 volt bank. Entire set up should be only $1K and produce just shy of 7kw of charging.
Bob
--- On Sat, 9/15/12, hardy71uk <dottir@hotmail.com> wrote:
From: hardy71uk <dottir@hotmail.com>
Subject: [Electric Boats] Re: 48v diesel telecommunications standby gen?
To: electricboats@yahoogroups.com
Date: Saturday, September 15, 2012, 10:27 AMI'm thinking of using a 3phase generator . Use three transformers to bring the voltage down to the required value . Make the output DC via a 3phase rectifier. Should make a simple charger.
Chris S
--- In electricboats@yahoogroups.com, Michael Mccomb <mccomb.michael@...> wrote:
>
> other than the Panda stuff which is VERY expensive has anyone come across a 48v dc diesel charging system.... i'd rather use a sort of RAID approach with a much less expensive diesel/PMA system but am pushing the limits of my understanding to devise such a system.... seemingly both diesel engines AND permanent magnet alternators of sufficient power/capacity can each be had for under $1k... some electronics is undoubtedly needed but adding this would still bring a system in perhaps 10k under the Panda price
>
> one can stumble across all sorts of reference to 48v diesel units used for telecommunications systems but i have had great trouble actually tracking such a unit down
>
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