newbie looking for help

[isyl]

Hi all, I'm a student and i'm doing a work to graduate.
I saw this forum and i think that its very intresting.
My project consist in a stirling engine connected to a linear fresnel plant.
To complete my mathematical model i need some datasheet of stirling engines. In particular i need the graphs of efficency,power,temperature.
I can't find them on the web. The plant is around 100Kw but i can reduce the mirror surface if needed.
Please help me, i'm getting crazy. Thank you.

[Ian S C]

Isyl, ? 100kw, do you not mean 100watts, or even milli watts, 100kw solar would take up best part of a city block, it's going to be massive, thats industrial size, or is that the calculated out put from the Fresnel lens, I can't remember how many watts per sqare metre, and I think I only knew about parabolic lenses. Someone may know with any luck. Ian S C

[isyl]

consider a radiance of 800 watt/m and a lens sufrace of about 1000mq ---> the maximum power is 800*1000 => 800Kw but it goes down due to the losses

[Ian S C]

isyl, What pressure are you going to use in your Stirling Engine, and what sort of efficiency do you expect to get from the motor. Ian S C

[vamoose]

Hello isyl,
In the renewable energy industry, when calculating the potential output of a solar array we use a term called Peak Sun Hours. Depending on your latitude and time of year and orientation of the array to the sun, this can be quite variable. 1 peak sun hour is equivalent to 1000w per square metre,
this takes into account the overall average irradiance that will fall on a square metre over the entire day starting from 0 all the way up to whatever (say for example a 1300w value, depending where you live).
for example where I live, the Maximum expected peak sun hours, for regular conditions of a correctly orientated fixed array, range from about 4 to 6.5 depending on the time of year.
(so this equates to 4000w to 6500w per square metre, per day)
For an array size you can then do the calculations, also with other electrical conversion efficiencies progressively included.
A solar panel might hover around 15% efficiency before other losses.
A fresnel lense itself initially would have fairly minimal losses, but as soon as you start to move down the chain you have to start to calculate each new loss.
You can easily find out the average monthly peak sun hours for your area with a google search.
Hope this is of some help...

vamoose

[isyl]

thank you but for the "solar part" my mathematical model is done. I calculatd the efficiency of an ipotetical motor using a graph edited by sunpower. In that graph there was the fraction of carnot efficiency (real efficiency/carnot efficiency) in funciont of the temperature ratio. Now i have the efficincy of my engine, i have the power imput, the power output. I suppose to have the cold head at the costant temperature of 293K with a dedicated system. The big problem is: how can i calculate the temperature of the thermal fluid (diatermic oil) after the heat exchange with the hot head of the engine? What i know is: the temperature of the fluid before the excange, the mass/time of the fluid (kg/s), the temperature of the hot head. sorry for bad english

[Ian S C]

If you are heating by the transfer of heat from oil, it should be easy enough to instal a heat probe in the hot end of the displacer cylinder. Ian S C

[isyl]

yes my problem was only to calculate the heat and the temperature. By the way there was a bad mistake in the math model... the prof did it... now i have a new mathematical model to work on... i hope that now is fine.... i'm doing this thesis with the prof of electrical machines and energy conversion from renewable sources... i have an electrical circuit that simulate the thermodinamic cycle of the plant. the current is the heat and the voltage is the temperature.... the fuel tank is a capacitor and the engine is a resistance... i know i something sick but i have to do it to graduate