This year was the first where I was able to run entirely on solar and have the yurt cooled every day I was there Setup time is about 12-14hr solo, less than half that with another person helping. I still brought a backup generator, because I lack faith and hate heat.

Along the way, I have built a mister-driven evaporation column, 4+ different evaporative coolers , two air-to-air heat-exchangers, three solar power systems, a mylar dome cover + door (16' 2V geodesic ) , a shade structure for 20 people, an H13 Hexayurt (2" RMax + radiant barrier), a 6' stretch Hexayurt with a novel sandwiched material walls (mylar, corrugated plastic, RMax), and even a data logging system to track temp/RH throughout the cooling system. In other words, I'm obsessed.
Disclaimer: I'm not asserting the following is an easy, cheap, small, or minimum power/water solution to cooling a hexayurt. It does work, though. All prices are approximate.
OVERVIEW
The system I'm now focussed on couples an evaporative cooler with an air-to-air heat transfer unit, i.e. Indirect Evaporative Cooling as they say in the HVAC-biz. Ambient indoor temperature inside my H13 Hexayurt is about 25F below outside temperature (e.g. 73F on a 98F afternoon) at about 40% relative humidity -- and virtually no dust! This is achieved using about 4Gal of water/day and ~300W of power.
In the current configuration, the heat-transfer happens AFTER The evaporative cooler, and is used ONLY to cool the internal air. This allows me to get the cold, but not the humidity. This is not power efficient, but it leave the inside of the yurt completely comfortable.
SOLAR
I'm finding that solar panels on the playa do not deliver more than about 60-65% rated efficiency at the peak of the day. 600W of panels deliver about 2.5-3KWhr/day, or over 8-9 cooling hours, about 300W. Dry blowing or sweeping the panels gives about 5% over doing nothing (the first day, it'd get worse I'm sure) but pouring water, squeegy-ing, and wiping with clean paper towels improves things by 5-10% additional, i.e. it's significant. Panels are 6 100W Renology ($800) on the ground facing south with the appropriate inclination as advised by solar panel calculation sites. They are mounted in pairs onto 1.5"x4"lengths of wood using normal z-brackett flipped over to make the wood mount closer to flush, and a horizontal length of 3/8" square tube steel to provide rigidity. Each pair weights perhaps 40-50lbs, and has a simple setup using nylon cord and three lengths of wood as legs to provide the tilt. They are staked down in case of high wind.
I had run the system with 12V with panels all in parallel using the cheapest MPPT charge controller I could find. The lack of sufficient information about system state, plus the improvements in line-loss, reduction in wire size, etc lead me to the current setup with 24V batteries (2 80AHr AGM batteries in series, $400) using a Victron Energy Charge controller, battery monitor and battery protector ($275 total, has bluetooth monitoring!), a charge balancer ($30) a 12V inverter with a 24-12VDC converter ($200), DC circuit breakers on the solar, batter, and inverter ($60), cables & a couple cheap inline voltmeters ($50).
I removed the standard solar power connectors and went to spades and terminals as I found dust in the connectors plus repeated connection/disconnection was making them unreliable. The battery hardware is mounted in an old tourister hard-side makeup-box carry-on, and the inverter/controller/etc are in an old CDJ+mixer flight case to keep them safe in transport and dry during winter storage.
EVAPORATIVE COOLER:
The evaporative cooler is built into a plastic footlocker and uses modern cardboard-honeycomb evaporative media to achieve 30degF+ temperature deltas. I would not use the footlocker again, as after 5 years the tape began to fail and I had to use a bunch of spray sealant and tape to keep it watertight -- yuck. Building into a rubbermade or a large food cooler (both watertight, the later has a drain) is a a better option
The evaporative media is vaguely like corrugated cardboard, but with bigger holes, wavy layers, and variable density -- http://www.coolingmedia.com/celdek/ . I use an 8" thick section, about 16" x 20", though the usable area is likely closer to 12"x18". Water distribution is via 4 lengths of 1/2" PVC pipe with tiny holes drilled every 1-2",. fed by a single 1/2" flexible hose from a 12V pump submerged in a 5 gallon bucket, with the hose ziptied to a lenght of rebar to hold the pump down. (don't ask about the less clever ways I mounted pumps.) The cooler sits just above the bucket and drains water back into it. The bucket is a perfect place to cool drinks (beer, coconut water, etc) down to about 58F.
HEAT EXCHANGER
To avoid bringing the humidity inherent in evaporative cooling into the living space, the cold air is used to cool in the internal air *without mixing* via an air-to-air heat exchanger unit. The HXU is built out of corrugated plastic (eg. election signs), cut into about 40sheets 1'x3' and sandwiched with channels going in alternating directions. By feeding internal air through one path, and the cold-wet cooled air through the other, the internal air is chilled. The now-slightly-warmer wet air is vented out. (by using two baffles, im effectively getting a counter flow heat exchanger with 3 cross-flow stages out of a single 1'x1'x3') stack of plastic) (Exlcuding salvage plastic, $50 for tape and caulk etc)
Typical steady state mid afternoon temperatures are:
Stage 1, evaporative cooler: Intake air 95F. -> Cooled air: 64F. (Water supply: 58F)
Stage 2, heat exchanger, wet side: Humid cooled air: 64F -> Exhaust Air 73
Stage 2, heat changer, dry side: Inside Air 75F -> Output air (70F)
FANS/DUCTING/AIRFLOW
I've been using 6" AC centrifugal duct fans (about 100W each), but the inverter losses and the rather-painful inductive load at startup is leading me to consider fully switching to 4" marine bilge fans (I've used two midway through the main airhandling loop with good effect, but they are LOUD. (duct fans: $120, bilge fans, $80, ducting $100?)
The air intake/outflow vents are venturi effect vents (roofvents.com) which produce airflow via the wind blowing across them -- reducing power usage. ($100)
I've tried using flexible plastic ducting, but the static pressure loss is unacceptable. Rigid-flexible metal ducting seems to be a good compromise. The ducting is set up (one T-juction and a couple quick-connect hoses) to allow me to easily run just stage 1, or just the exhaust.
A good door, thorough taping, plus "mudding" the bottom edge of the yurt on the outside is necessary to avoid airflow, i.e. convective heat loss
Next steps:
Back to a cooler for the evaporative cooler container.
Add a precool stage using exhaust air
Switch to entirely DC.
Reflect further on the fact a generator and AC would be cheaper, lighter, and easier in every way.
Questions, comments, thoughts, welcome. More pictures to follow someday.
Apologies for typos, out of time for today.