SOLAR TODAY - Get Started, Fall 2010

solar water-heating
automatic control systems. These add complexity and cost
to the installation.

The most common cold-weather system today is the closed-loop antifreeze heat-exchanger system, or active indirect system. When the collector is warm, a food-safe propylene glycol antifreeze solution is pumped through the collector and on through a heat exchanger, then back to the collector. The heat exchanger heats city water for domestic use. The heat exchanger is usually located at the bottom of an insulated storage tank. (Sometimes the storage tank is also the home water heater, with an electric or natural gas heating mechanism for use when the collector is cold.) a breach in the heat exchanger would leak antifreeze into the drinking water, which is why it’s necessary to use only food-safe propylene glycol in these systems. many local plumbing code officials require

Maintenance >> All hot water heaters need to be flushed annually, as do solar system storage tanks. The pumps and valves in an active system are electromechanical devices that will need periodic attention. Annual pressure testing can identify potential problems before they become major leaks.

Long-term corrosion is an issue in any plumbing system, but
a well-maintained system can go 20 years or more before
replacement of major parts.

Introducing...

The sun.

It’s the one thing that makes everything possible.

Space heating >> DSWH can also be used for space heating. The most efficient method is an in-floor radiant heating system that sends hot water through pipes embedded in the floor. A gas backup water heater is typically used because a house is coldest at night and in winter months. The solar collector area needed is generally 10 to 30 percent of the home’s floor area, depending on climate.

double-walled heat exchangers to permit systems in their
jurisdictions. GS
This article is adapted from the “Solar Energy Resource
Guide 2008,” published by the NorCal Solar Energy Associa-
tion ( norcalsolar.org), a chapter of the American Solar Energy
Society.
liz merry owns verve Solar Consulting ( vervesolar.com)

and writes SOLAR TODAY’s “ask ms. liz” blog. Diana young ( dyoung@sfo.com) is an editor and designer who worked on the Solar energy resources guide. Barry Butler, Ph.D., owns Butler Sun Solutions ( butlersunsolutions.com) and heads the aSeS Solar thermal division.