Sunday, August 15, 2010

Re: [Electric Boats] Re: Water Temperature

 

 "The reason is I have 250 square feet of collector surface with a large heat battery.  Solar heat collectors are much cheaper than PV of any style so there you have it."
 
 
Kevin:
 
I really like the out of the box thinking of you and others in the group. I've been converting my house over to solar here and there over the years. Actually had solar hot water since the 1980's. But, I'm thinking I need more heat more than hot water so I am going to be modifying it this year for that purpose. Never thought of the idea of electric generation. But, makes sense. Good luck with your conversions and experiments. The ideas of this group get me thinking diferently too. Thanks. 
 
Capt. Mike
http://biankablog.blogspot.com 


--- On Fri, 8/13/10, Kevin <pembertonkevin@gmail.com> wrote:

From: Kevin <pembertonkevin@gmail.com>
Subject: Re: [Electric Boats] Re: Water Temperature
To: electricboats@yahoogroups.com
Date: Friday, August 13, 2010, 2:31 PM

 
Yes, the cost is high!  I think I figured the cost of a set of junctions from TE on the net at $150 us for 6 amps at 15 volts, using a temp difference of  200c..  Lower temp difference will be much higher.  You can find all the data on the TE website to do the calculations.  Using a evacuated tube solar collector as heat source temps of 300 deg F. temps are possible, and with a water sink (pumping water from a deep keel not the surface) would help reduce the number of units needed.  If however you loose your cooling water flow catastrophe failure is a sure bet.

On the positive side such a system can be run 24/7 should you devote space for a heat battery that will supply enough heat to run through the night.  As an alternative, fuel oil will supply the heat needed on cloudy days.

The catch for such a system is the roughly 95% loss to inefficiency.  If you have plenty of collector space the energy losses mean little, and it is accepted that a square meter of surface area receives 1000w of heat energy from the sun, even 50% recovery of heat is considered good making 500 watts realistic.

Lower losses have been realized with a solar heat engine (stirling engine), however life expectancy for a well designed system may point you in the direction of the pelter junctions over the stirling engine.  Both techs work with a any heat differential however and have been studied for many years.  Deep space probes use the stirling engine with a nuclear heat source, go figure.  My small proto-type using solar uses Pelter Junctions and I feel the daily output is better than any PV on the market even though the efficiency rating of some panels are better than 50%. The reason is I have 250 square feet of collector surface with a large heat battery.  Solar heat collectors are much cheaper than PV of any style so there you have it.

Kevin Pemberton
On 08/10/2010 03:23 PM, Ron wrote:
 
Hi Bill,
As Lonner said, the price will be the killer, we used these in some applications when I worked in a wafer fab. I have not checked prices after 2000 but they were high back then.

Ron

--- In electricboats@yahoogroups.com, William Grace <jwsys@...> wrote:
>
> Hi Ron
>
> Your concept of using the wasted heat from anywhere has got me thinking.
>
> If I remember my physics correctly, pairs of thermocouples can provide
> this result. Solid state chiller boxes use this principle in reverse
> (refrigerators without compressors). These thermocouples consist of
> dis-similar metals connected electrically, and are used in pairs. In
> the chiller set up, one of the thermocouple joints is inside the box
> whilst the other is outside. The thermocouples are connected in
> series and are then connected to a battery of suitable voltage. The
> current flowing through the series system causes the joint temperature
> to change, one becoming hotter, the other colder. Most of the simple
> chiller boxes have a 'heat' option which is derived by reversing the
> connections. Theoretically, it is possible to reverse the process
> so that a current is produced when the thermocouples are held at
> different temperatures. One could be under a solar panel whilst the
> other half of the pair could be attached to a skin fitting which would
> hold it at water temperature. The parts could be obtained by
> disassembling a chiller box. Usually the thermocouples are attached
> to heat sinks, one being placed inside the box with the other outside.
>
> I have not tried this but expect it would work although the current
> generated would be of a similar order to that used to run the chiller.
>
> Bill Grace
> NZ
>



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