Solar showers for summer campers

[nick pine]

R. writes:

> We are planning a huge event in July in Montana for about 600-800 campers. We are in need of a simple solar shower design that is cost effective

NREL says 2220 Btu/ft^2 of sun falls on the ground on an average 72.5
July day with an 86.7 high and a 0.0080 humidity ratio in Billings MT.
The groundwater temp is 47.1 F.

http://www.sunfrost.com/efficient_shower.html says fully-enclosed
showers can be much more comfortable and energy-efficient than showers
with lots of airflow through the shower compartment, especially with
dry outdoor Montana air. You could put up a well-airsealed $1K 14'x96'
commercial plastic film high-tunnel greenhouse with an Astroturf or
horse stall mat or landscape fabric floor and let people take showers
inside. If each person has 8'x10' of floorspace, 12 people can shower
at once, with 6x12 = 72 10-minute showers per hour, or 864 showers in
12 hours.

While in the Navy, Bucky Fuller noticed that wind-driven spray on the
deck of a ship kept his skin clean. IIRC, his Dymaxion house shower
used 1 pint per hour of water, with heat lamps and a compressed air
mist. It inspired McGill U's $6 Water Conservation and the Mist
Experience pamphlet, which suggested using a garden sprayer full of
hot water, eg this $8.37 1-gallon sprayer from Wal-Mart
http://www.walmart.com/ip/RL-Flo-Master-1-Gallon-Sprayer/13376324 If
800 people each take a single 1-gallon 110 F shower per day, that's
800x8.33(110-47.1) = 420K Btu/day.

If the greenhouse temp is 110 F during the day and 110 F water inside
a single 1 ft^2 horizontal layer of plastic under the greenhouse cover
gains 0.9x2220 = 1998 Btu/day and loses 12h(110-65)1ft^2/R1 = 535 Btu
at night, the net gain is 1463 Btu/day, so we need 420K/1463 = 287
ft^2 of glazing, eg a 30" diameter poly film greenhouse air duct
http://www.greenhousemegastore.com/product/power-tube-tubing/fan-jets-power-tubes
laid flat on the ground inside the south wall of the greenhouse. A 96'
$99 unpunched "power tube" duct inflated with 1600 gallons (214 ft^3)
of water would be about 8" tall x 40" wide with about 96'x40/12 = 320
ft^2 of sun surface.

Israeli greenhouses store solar heat in water-filled poly film ducts
on the ground between rows of plants. They tie the ends of the duct up
to stakes in the ground to contain the water. You could fill the
sprayers with some sort of pump. Are there any cloudy days in July in
Montana? In PA, 4 fully-inflated 30" ducts containing 1885 ft^3 of hot
water inside a 14'x96' high tunnel might be covered with soap bubble
foam on cloudy days and at night.

Nick