Folks, I recommend you stay away from lithium bromide. The main problem is its corrosive nature. Also, it's not easy to devise a good absorber using this substance. I know because I built a very small test unit using the stuff.
I recommend you all look into adsorption systems using water as the refrigerant and solid adsorbents like silica gel and zeolites. While these present serious difficulties as well, there is no problem whatever with corrosion. The main problem there is the high heat exchanger surface required to cool the adsorbent while it's adsorbing the water vapor, and heating the adsorbent during regeneration. Commercial units are using conventional finned copper heat exchangers by packing them with small beads of the material. I think a unit with a low cooling capacity and operating for long periods can work well and be fairly simple, but I do NOT recommend solar as a heat source. I think a biomass furnace used to generate steam might work - or even better using the steam exhausted from a steam engine to drive the unit to get electricity and cooling (and use the steam for heat during winter months).
I did brief testing on a small lithium bromide unit I assembled from scratch - I did this just to answer questions - it was not a useful unit. What I found that should interest anyone who wants to go this route is that establishing and maintaining a high vacuum on a small system is not terribly difficult. A trick I found was to use steam to help displace the air when drawing vacuum. So, I was able to pull out virtually all the air with a crappy vacuum pump by first putting hot water in the system, then drawing down the system at a low point since water vapor is less dense than air. It worked perfectly. I was able to chill the water to 30F (lower than freezing since I probably had some salt in the water that lowered it freezing point). In other words, there was a near perfect vacuum in the system even though I used a vacuum pump that can't get anywhere near that.
Now, ammonia is VERY promising for this application. However, getting that to work with a low temperature heat source is a lot MORE difficult than other systems. If someone is dead set on using solar heat as the driving energy, then go with silica gel/water adsorption. The best feature of ammonia is the ease in making the absorber, and one doesn't have to deal with a vacuum. It's possible to use a water column as the absorber where the evaporator connects to the base to bubble ammonia vapor into the column. As long as the water is kept cool, then it will work. A continually operating system used to maintain a modest capacity does not require much ammonia. Seriously, just a gallon or so will work. What is needed is a pressure pump to force the ammonia water solution from the absorber through a heat exchanger tubing coil placed in the furnace. The solution is partially vaporized, then pushed into the separator. The ammonia vapor leaves through the top of the separator and into the condenser, turns to liquid, then moves to the evaporator via the expansion valve. The weak ammonia water solution in the separator leaves at the base, should be used to preheat the rich ammonia water solution leaving the absorber, then the now cool water enters the absorber to take in the ammonia vapor from the evaporator. Note that with a high temperature heat source, it's possible to have a unit run without electricity by using the high pressure ammonia vapor from the separator to drive a micro expansion engine to force the pressure pump - however, it makes more sense to just use a small dc motor for very small units. NOTE: Can't use copper with ammonia - use steel tubing - use aluminum for the evaporator.
NOTE: I posted this primarily for interest. I think small vapor compression units are the way to go for off grid space cooling, and photovoltaics makes sense in most settings. A wood fueled absorption/adsorption cooling system might be practical if designed for a low cooling capacity and run for long periods, but the development costs would most likely be prohibitive. I'd like to see it, but I decided I'm not willing to risk the resources in its development.