Domestic Hotwater Topics

Topic: Why heat water before living space?

From: page-ed

Any house can be non solar in siting and in design and still find a place on the roof or property with reasonable sun exposure for heating hot water for showers ... many commercial solar water systems assume that collectors will be remote in some part of the yard or on a roof and a pump an heat exchanger is assumed in the system. The owner must simply find a location that is available to sun during both the summer overhead sun and the winter slanting sun.

Lets assume that a family of 3 can get by with 60 gallons of hot water daily and incoming water must be heated from ground temperature of about 55 degrees to 115 for usage.. at 8.3lbs per gallon, the 60 degree rise in water temperature requires about 30,000 BTUs of heat energy which can be collected at a flat plate collector of modest size (say 32 sq ft). Allowing for inefficiencies in moving heat from a collector to the storage tank we might assume to gather 300 BTU per hour per square foot of collector... enough to gain 30K BTU in 3 hours on a good sunny day.

There are many assumptions and some solar hot water collectors might be more efficient or less... but themain point is that it would take a huge collector area to attempt to heat living space and this oversized collector space would not be needed except during winter when heat needs can exceed 30000 BTU per houreasily. It is more efficent to attend to a problem that exists every month of the year... heating hot water ... and get a payback on the investment in usage every day.