14 June 2002
SOLAR ENERGY CASE STUDY AT FORT HUACHUCA, AZ
G-1. PURPOSE. The purpose of this study is to present findings on the installation
and the subsequent operation of the solar hot water heating system in the Koch
barracks (Building 80306) at Ft. Huachuca in Sierra Vista AZ. Systems Engineering
and Management Corporation (Systems Corp), under Contract Number DACA88-94-D-
0016 for the U. S. Army Construction Engineering Research Laboratories, completed
G-2. SCOPE OF WORK (SOW). The scope of work (SOW) required that a 1,000 ft2
(93 m2), or larger, flat plate solar energy system be developed for installation on
Building 80306. The system was to connect to the existing recirculating domestic hot
water (DHW) heating system. Systems Corp determined through load calculations that
a 1,000 ft (93 m ) system was too large for Building 80306. The final system design
included 384 nominal ft2 (36 m2) of collector area.
G-3. CONSTRUCTION ISSUES. During the development of this project, multiple
issues arose which were obstacles to design completion. The primary issues were
building selection, system selection, and storage tank size.
a. Building Selection. Approximately eight different buildings were evaluated
for the installation of the previously described system. Different factors were used
during the evaluation, including domestic hot water (DHW) load and building
orientation. Building 80306 was selected because of a relatively large DHW load and
because of its orientation.
b. System Selection. The SOW required that the solar energy system be
designed in accordance with TM 5-804-2 (now UFC 3-440-01). Systems Corp designed
a system that corresponded to the requirements of the technical manual as closely as
possible. Two problems were encountered. The first was connecting the solar energy
system to the existing DHW system. The existing system is a recirculating system that
is not addressed in the manual. The second problem encountered was the location of
the solar system storage tank. According to the technical manual, the storage tank
should be sized to hold 1.5 to 2 gals of water per square foot (61.1 to 81.5 L of water
per square meter) of collector area. For the original system at 1,000 ft (93 m ), this
equates to a minimum tank size of 1,500 gals (5678 L). For the revised system at 384
ft2 (36 m2), at least 576 gals (2180 L) of storage is required. With the existing
equipment in place, the mechanical room is too small for that amount of storage.
Therefore, the storage tank for this design had to be located outdoors.
c. Storage Tank Size. Several options for outdoor storage tanks were
evaluated for this project. The first option was the use of a single "standard" domestic
water storage tank insulated for outdoor installation. The price for a nominal 2,000 gal
(7571 L) cement-lined storage tank, evaluated for the 1,000 ft2 (93 m2) system, was