When I attended the Solar 2008 conference in May, I had the opportunity to interview Tom Lane, a pioneer in the solar energy field. Tom started in the industry in 1973 and turned professional in 1977, doing solar hot water and electric. He was elected to the Solar Hall of Fame in 2006 (there’s been 47 people elected since 1976). His company, ECS Solar, does solar electric, hot water and pool heating systems in Florida. He wrote the book “Solar Hot Water: Lessons Learned 1977 to Today”, which some consider the bible of the industry, and contributes to Solar Today and Home Power magazines.
While Tom was very busy at the expo giving workshops and sitting on panels, he was gracious enough to sit down for 20 minutes and share his thoughts.
Q- What’s the state of the art now in solar hot water?
Solar hot water technology is at the apogee of its technology right now. Solar heating technology was invented in the 1880s and perfected in the 1980s. The only thing that’s improved since then is the digital controls that give a lot more automation and functions. As far as the basic collection of solar thermal energy from the sun, it’s a very simple technology.
Q- For a California homeowner, what would be the first step in finding a reliable dealer?
You would want to Google for local sources or go to the California Solar Energy Industry Assoc for a list of contractors who do installations. Solar hot water is really the low-picking fruit for people to save money, because most systems cost about $5500 to $7000 and there’s a federal rebate of $2000 for systems which is a good deal for residential customers. For example, if you were heating your water with a PV electric system, you’d have to pay $20,000 to $22,000 to accomplish the same thing as a $5000 thermal system.
If you have an electric hot water heater, it’s a no-brainer; you just put in a bigger tank so you have back-up when you need it. It’s a little bit more complicated if you have gas, in that you have to have room for the gas tank, which is typically 25” in diameter. You can’t use a standard gas water heater in a solar set-up, because regular gas water heaters heat from the bottom. The problem with feeding solar-heated water into conventional gas water heaters is that the heater thermostat won’t click on and heat the water.
You can put in a gas tankless water heater or get rid of your gas backup and install an electric backup heater to the solar electric.
Q- So electric water heating is the best backup heater system?
Yes, electric backup heaters are usually the best choice. Remember, a thermal solar system is sized to provide between 85% and 95% of home water heating and so there very little need for backup when it’s temperate. In warm climates, people can go eight or nine months and never turn their backup heater on. Solar hot water systems are sized on an average day of the year, depending on the size of the family and their needs on an average day, to last 1.5 to 2 days.
All solar hot water systems are configured either to pre-feed a gas water heater or an electric element in the holding tank.
Tomorrow: Conclusion of Interview - What are the pitfalls homeowners should watch out for?
