Hawaii Law Requires All New Homes Install Solar Hot Water Heaters
All new homes built in Hawaii will be required to install solar hot water heaters beginning in 2010, cutting energy costs by 30%. The state of Hawaii has a goal of at least 70 percent renewable energy use by 2030. “Achieving this goal is nearly impossible without widespread use of solar water heaters,” Hawaii Sierra Club director Jeff Mikulina says. “The solar roofs bill is smart policy, sensibly crafted to smooth a transition toward zero-energy homes of the future.”
Via: Sierra Club
Image: This Old House
That is definitely a step in the right direction!
Mastercraft Exteriors
The diagram of the solar water heater shown in your post is only one of many types. Hawaii’s mild climate allows many types, from ICS (breadbox) to Thermosyphon . All have inherent problems, which new home buyers (and many experienced home buyers) will not be aware of. The biggest problem is water that gets too hot. Most storage tanks for hot water are designed to withstand 140 degrees F. Solar can reach much higher temperatures, with resulting corrosion of the tank. At 150 degrees, the corrosion rate doubles, and at 160 it doubles again, ditto for l70
and 180 degrees. Maintaining the temperature of the tank below 150 degrees could double or triple the life of the system, but unfortunately, there does not seem to be a mechanism available to limit the sunshine. In addition, the anode rod that is standard protection for a hot water tank, cannot be monitored for corrosion without considerable hassle, expense(if a plumber must be called) and frustration. It usually takes 2 men with a very long handled wrench just to loosten it, and then requires about 4 feet of overhead clearance to remove the rod. Most people are unaware that the rod exists.
While I salute the “green” thinking that prompted the passage of the Bill, I am afraid of what unwary homeowners are getting for the extra $5000 or so that the solar hot water will cost, and most of all, I am afraid that they may be getting a lot less for their money than if they had done the research and picked out a system that they could maintain themselves. I base the latter fear on a phone call to the Hawaii energy department which I made recently to inquire about the type of system most often used in Hawaii. I was told, “The type that makes the most money for the installer and the manufacturer.”
Yes, I live in Hawaii and have been on solar pv power for 18 years, with an on-demand propane water heater. When the price of propane doubled, I thought of solar hot water, but after discovering the negatives mentioned above, I’ve opted to use an electric “mini-tank” water heater, turned on only for the half hour it takes to heat the small tank., and that only in the morning when I have excess solar power. The propane water heater will stay, however, for rainy days and for guests.
What I would like to know is if the Bill specifies which solar hot water system must be installed. Any comments would be welcome.
Aloha,
Goose Girl