Let the sun heat your water by erica

The 1bog team learned just about everything we ever wanted to know about solar thermal water heating at the San Francisco Solar Hot Water Heating Tour and Exhibit on June 21 ((International Solar Day). The exhibit, sponsored by SF Environment, was designed to educate businesses and residents about the advantages of heating water with sunlight, a technology that could reduce the average household’s carbon footprint by up to 30% and cut electricity bills by 50-80%. 1bog is exploring solar water heating products so stay tuned for news about availability in your area.

Here’s how it works: A solar hot water heater passively harnesses the sun’s energy to pre-heat water before it enters your home’s conventional hot water tank or tankless heater. A rooftop solar collector facing the sun absorbs the sun’s heat and then either directly heats the water or heats a non-toxic fluid that heats the water through a heat exchanger. (The fluid is propylene glycol, which also works as an anti-freeze, a critical function in cold climates). The heated water is then either pumped or allowed to passively flow to a storage tank (this might be your existing hot water tank or a supplemental tank) . During its stay in the storage tank, the water gets a small fossil fuel-powered boost to the extent needed to heat the water to the desired temperature (typically 120 degrees).

Confused yet? You can read more about how solar thermal works here. Bottom line: You turn on the hot water tap and get free hot water courtesy of the sun (you still gotta pay for the water though and, of course, the solar water heater).

During the tour, we got to see a large solar water heater on the roof of Project Open Hand, a non-profit that provides meals to seniors and people with AIDS and other critical illnesses. Open Hand’s twin solar electric and solar hot water systems save the organization $15,000 a year. The solar hot water heater is a product of Luminalt, a San Francisco-based solar electric and thermal appliance manufacturer.

We also got to see state-of-the-art Heliodyne and SunWater Solar systems up close. These companies have taken a simple design concept and elegantly engineered systems that perform optimally and conserve tons of energy–pretty impressive.

Solar water heaters start at around $7000, but a 30% federal renewable energy credit can help offset the cost. And 1bog is working on getting the price down by negotiating group discounts with manufacturers and installers. In the meantime, you can save energy by setting your water heater no higher than 120 degrees, taking showers instead of baths and keeping your showers under five minutes.