Nothing special about the compressor other than it works regardless of which way it is rotated, some only work one way.
Little nugget of information: "Sanden standard compressors rotate in a clockwise direction only with the exception of SD5 Sanden models that can run in both clockwise and counter clockwise direction." and "SD5 Compressors have a straight cut gear allowing them to run CW or CCW"
Many people also note/complain about a growling noise from the SD5 compressor that isn't present with the SD7...I have a feeling the difference in gear profile is the answer. The generally higher efficiency of the SD5 may also be due to those straight-cut gears.
Seems like SD5 is the way to go to increase mounting versatility, and I'm sure the Europa engine bay is a welcome environment for more noise.
I found an SAE summary paper with details on the average continuous cooling load (not system input power) of a few newer vehicles, driving around Arizona in up to 105* weather, creatively titled "MOBILE A/C SYSTEM ENERGY REQUIREMENTS". That shows just over 6000 BTU/h to keep the "worst" vehicle on the worst drive at a comfortable temperature. Probably a larger SUV with a black interior, though the data is anonymized. Other cars required closer to 1-2000 BTU on a 95*F drive. I think it's safe to guess that the Europa likely requires no more than ~6000 BTU/h of cooling capacity to satisfy almost all drivers, when considering that automotive AC systems tend to be 2-4x oversized nowadays to quickly cool down then you start a car that's been sitting in the sun.
I ran those numbers by my dad, who worked on AC systems at GM for a few years in the early 2000s (C6 Corvette and others) and still does today for other companies, and he remarked that 6k BTU/h is definitely plenty for the Europa, even with the large glass areas.
Next in compressor sizing is matching the engine RPM to compressor RPM, basically just matching their top speeds and making sure the cruising engine RPM will result in enough cooling from the compressor. Typically, they're geared 1:1 or a bit lower in a high-reving engine.
The small SD5H09, a R134A compressor aimed at aftermarket applications, is capable of 12,000BTU/hr (1 ton) of cooling at 3000 RPM, which seems to be standard or a bit low for Europa cruising speed. At the Renault Europa's idle, 1k rpm iirc, it's still capable of more than 3,000 BTU/h, well above what's required to maintain cooling. It seems like a 1:1 pulley would be fine here as the max continuous RPM for the SD5H09 is 6500, with bursts to 7500 allowed (such as during an aggressive downshift), quite directly matching the redline of the tachometer. If you're going to 8k on the regular I assume you also do not want the weight of an AC system...
The SD5H09 is the smallest of Sanden's aftermarket-directed compressors, and still quite oversized for us, probably due to the small market for very tiny aftermarket AC systems.
Going with a smaller compressor means that it'll be running longer than a larger one (but not necessarily starting more often, depends on your temperature control logic), which is hugely beneficial for this weird application. A larger compressor would suck more mechanical power down, putting a large load on the camshaft and timing chain for a brief period, vs a smaller load over more time. That's a simplification; because of how AC systems work the mechanical power consumption varies a lot, but the SD5H09 is not capable of consuming more than 5hp under any circumstances. That's the easiest way to safeguard the timing chain; a large compressor could consume 10hp or more in certain conditions and would cause much more premature wear, though it could technically cool faster.
TLDR: I think SD5H09 is the "right" compressor for a Europa. Those come in several different drive styles, including normal V-belts, wider V-belts, and 4, 6, or 8 groove serpentine belts. Undecided on which makes the most sense, but I'm drawn to serpentine belts again for the flexibility in mounting, ease of reverse-bending, and lower parasitic losses.
