1. Solar Water Heating
Jack Cowan
Cowanhouse
www.cowanhouse.com
June 27, 2013

2. Objective: to provide a framework
for determining solar thermal
viability

3. Solar Water Heating Systems
(Solar Thermal Systems)
• Largest application is swimming pool heaters
• Black box collector first patented in 1891
Integral Collector Storage (ICS) (also Batch)
• Other collectors include flat plate and
evacuated tube
• Systems are either active or passive, direct or
indirect
• Expensive, but nearly free operation and most
environmentally friendly

4. Batch Heater System
• Source Arizona Solar Center

5. Closed loop drainback system
• source Arizona Solar Center

6. Closed loop antifreeze heat exchanger
system
• source Arizona Solar Center

7. Prerequisites to Solar Thermal
• Reduce hot water waste – conservation 1st
• Evaluate your hot water needs
• Compare solar to other water heating
technologies

8. Reduce Hot Water Waste
• Repair leaky faucets
• Insulate pipes where possible
• Use high efficiency shower heads and aerators
• Select most efficient appliances that use water
• Optimize hot water distribution (with new
construction design)
• Improve water use behavior

9. Evaluate Your Water Heating Needs

10. What can you tell about water heating requirements from utility billing
data if this house has a gas fired furnace and traditional gas tank water
heat? Source Jack Cowan 2006 utility data
Annual Gas Consumption
0
20
40
60
80
100
120
140
160
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Therms

11. Compare Solar to other Technologies
• Tank systems, gas and electric
• Heat pump water heaters
• Tankless systems, gas and electric

12. Tank Water Heaters
GE 50 gal Marathon 85 gal
traditional plastic lined

13. Tank Systems
• Inexpensive to install
• Stand by heat losses are biggest
drawback...this is what we need to avoid
• Most common in the US, but very uncommon
in most of the world

14. Heat Pump water heaters
Rheem GE Bosch

15. Heat Pump Water Heaters
• More expensive to install than tank system
• Very efficient in certain applications, i.e.,
basement located system in the south
• Pulls heat from surrounding air to provide up
to 50% reduction in energy usage compared
to electric resistance heaters

16. Tankless

17. Tankless (Demand) Systems
• More expensive to install than tank system
• Eliminates standing tank heat losses
• Only operates when hot water is running
• Can be electric, but more commonly gas
• Never runs out of hot water
• May have to coordinate use when using
multiple showers, laundry, etc.

18. Evaluate Costs
(good generic reference, but location and conditions unknown)

19. Jeff and Karen Cowan’s
Zero Energy Home, Atwood, TN

20. Solar installation ZEH
• HTP stainless steel 80 gal primary tank
• 4’x10’ flat plate collector
• Kyocera 20w PV module for power
• Backup electric resistance tank
• 12v pump, expansion tank, pressure gage,
valves, fittings, tubing, wiring, etc.
• Source: Bill Ball, bill@stellarsun.com

21. A bunch of happy installers!

22. Solar Collector installed

23. PV Module Powering
Circulation Pump

24. Solar Thermal primary and
secondary tanks

25. Summary
• Go through the process to ensure you’ve
made the right decision...Is Solar for you?
• If you choose Solar find a professional
provider to oversee the product selection and
installation
• Thank you. Questions?