U of U Dee Smith Athletic Center Solar Thermal Project
Prepared by Rod Hyatt, HTP National Solar Project Manager, 01 09 12
Parts list at bottom; separate files include panels and boiler room layout
Gallons per day (GPD): 6,650
Gallons per hour (GPH): 2,700
Estimating the ground water temperature to be 50° and raising that temperature to 110° = 60° increase. This is
based on 1/3rd being used 100° for showers and 2/3rds for dish and clothes washing at 130° (110° average).
Using the figure of 6,650 average gallons used per day, the numbers are as follows:
6,650 x 8.3lbs x 60° = 3,311,700 Btu
CONCLUSION: 3,311,700 Btu of heat required per day
Figuring the solar:
One HTP 4’ x 10’ collector (FP-40SC), based on the SRCC efficiency ratings and NOAA weather data for the SLC
area, produces = 27,000 Btu of heat per day.
Total Btu needed to heat all the 6,650 gallons divided by the Btu production of the solar panels:
3,311,700 Btu ÷ 27,000 Btu = 122 panels.
If 80% solar target (amount of hot water to be offset by solar) is desired, the numbers are as follows:
122 x 80% = 98. However, for balanced plumbing arrangement of 8 panels per string we will target 12 strings of
8 panels = 96 FP-40SC (could also be 6 rows of 16 panels with the plumbing going up the middle)
If collector angle was 50° at Utah’s 42° latitude, row spacing would place a 16.8ft shadow.
With larger solar hot water systems, sometimes it is easier to design and control two systems instead of one
(two 48-panel arrays, pumps and drainback tank into one central storage tank).
With 48 panels the copper trunk lines would be 2” with 1” return lines from each 8-panel string. Pump would
need to be sized between 60-70 Gpm at the lift from the DB tank to the panels. Final system design will
determine whether 2 array of 48 are used or one single with 96 panels.
CONCLUSION: 96 4x10” solar collectors
Figuring the water heater size:
Presently, heat and DHW is provided by 5 MMBtu of boilers (three units) feeding four old 119-gallon tanks via a
plate and frame heat exchanger. The recommended design will be to heat one tank to 130° using the boilers and
have additional three tanks for solar storage to achieve 180°. Because of the ceiling height restrictions of 8 feet,
four 580-gallon tanks will be suggested.
CONCLUSION: Use the existing three boilers and dispose of the old 119 gallon tanks.
Figuring the storage tank volume for the solar:
Considering that each 4’x10’ collector would provide 27,000 Btu per day based on a yearly average, and that a
total of 96 collectors are required, the numbers would be as follows:
96 x 27,000 = 2,592,000 Btu per day (total array production in one average annual day)
4 ea. 580-gallon tanks = 2,320 gal x 8.3 x 130° = 2,503,280 Btu (tank size to hold the full capacity of what the
collectors can produce filling all 4 tanks to 180°).
CONCLUSION: 4 ea. 580-gallon solar storage tank HTP-JS-48-084, insulated with no internal heat
exchangers.
Suggested materials list:
Qty
Item number
96
96
192
2
2
1
4
2
2
4
1
16
FP-40SC
FP-SM
FP-ST10
SSU-119DBX
8600-098
86008600-86
Item description
4 x 10’ solar collectors
Direct roof mount sets
Rear-strut legs
119 gallon drainback tank with internal heat exchanger
Variable solar pump control
DL3 Data logger with BACnet (trade $1,366)
0-10 signal box for pump modulation
Solar pump delivering 60-70 Gpm at figured fthd
Drainback-to-storage-tanks pump sized for Btu load
HTP-JS-48-084 580-gallon boiler storage tank
Anti-scalding valve (see note below)
8600-084
1” balancing valves with flow meter
Provider
HTP
HTP
HTP
HTP
HTP
HTP
HTP
Other
Other
HTP
Other
HTP
Note on anti-scalding valve design for the large swing of solar system: The valve should be able to temper to the desired temperature
from the maximum flow the pipe size and deliver down to 1.5 gpm at a temperature range of 120° to 180°.