solar assisted absorption cooling 1

[jayson30]

For designing a conventional electrical air conditioning system for a given space, the cooling load has to be estimated (internal gains + external gains)

I have found the cooling load, and I plan on using absorption chillers which would use hot water to operate. The hot water would be obtained from solar energy.

I am confused as to how do I start off?

except for calculating the cooling load I haven't done anything.

 

[willard3]

You will have to find absorption units that will operate in the same temperature range as the solar panels and are small enough for your load.
Not that easy; the smallest lithium bromide absorption units I know of are 10 tons.

 

[317069]

You can Not depend 100% on solar energy, it help as abooster source of energy, not the main source.
select your unit first, then talk with manfucturer.
also do everything under suppervision of an older engineer in your company
finaly do your load calculation by hand not by a program.

 

[jayson30]

thanks for the reply 317069 and willard3

I have found a few LiBr-water absorption chillers by Yazaki and Trane

My next doubt is regarding the calculation of the solar collector area

for a fact I may use TRNSYS to find out the collector area but im looking for hand calculations

 

[Drazen]

Apparently, you are just entering the field, and the basic thing you should know about solar designs is that solar system provide only auxiliary energy source, so you need main source, in your case that means source of hot water available year-round, or some of direct-fired absorption chillers.

Than you certainly need to have temperature regimes aligned as Willard mentioned.

Some manufacturers indeed developed absorption chillers intended to low and moderate load for HVAC applications, but they seems to be very ineffective in overall, I already attended some courses where thermodynamical analysis are conducted and shown how ordinary chillers and much more energy efficient, low load absorption chillers have EER close to miserable and even direct firing cannot improve energy balance much.

I believe that technology is yet to be developes. Absorption chillers are unparalleled for large-scale refrigeration applications, but that is not the case for moderate commercial projects.

 

[jayson30]

Thanks for your reply Drazen

the thing is I plan to make se of LiBr-water absorption chiller which if not completely, partially be powered by solar energy

I have read through quite a few journals written on Solar assisted absorption cooling but none of them specify the formulas (hand calculations) as to how was the system sizing done along with the collector area, inlet temp. for the system etc.

please help me obtain hand calculation formulas/method

Thanks

 

[chicopee]

You may want to peruse thru older written material in libraries since at one time there were absorption type refrigerators for the residential market. I use to have such a refrigerator in my rented apartment back in the 60's. The primary heat source was natural gas for this refrigerator.
Also mechanical engineering handbooks of older editions have sections devoted to this subject.

 

[IRstuff]

I think you need to do the math on this, PDQ. A typical house requires between 10 to 20 kW for heating. Over a 12 hr night, that's something on the order of 180 kWh.

I'm guessing that a place that needs heating will only get less than about 5 kWh per day per m^2 of collection area. That means you'd need a minimum of 36 m^2 of collection area, or ~400 ft^2, and that's only to account for the direct heat load. There are losses and there may be other limitations. While that area is something that will fit on a rooftop, that'll be a gigantic dead load on the roof structure.

TTFN
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