The Romans used solar-thermal energy to heat their tubs. Now, thousands of years later, modern systems are being added to commercial buildings to handle large hot-water loads, according to the Energy Trust of Oregon. But Doug Bolen, commercial solar program manager for Energy Trust wants to see more.

“I don’t think that commercial building owners are aware of what solar can do for them,” Bolen said. “There are a number of engineering and installation firms who can install these systems, but there is not a huge sales force out there that goes after these buildings.”

Solar-thermal energy has been used since 1000 B.C., when the Romans began running water over hot rocks for their famous baths. Solar-thermal water heaters may vary in size and details, but they all gather heat from the sun in a solar collector and transfer that heat directly to the water supply, while storing the heated water until it’s used.

“You’re not changing (the solar energy) into electricity like photovoltaics, so it’s a more efficient process,” said Frank Vignola, director of the Solar Radiation Monitoring Lab at the University of Oregon. “The excess energy is turned into heat so you don’t lose as much energy.”

Randall Stevens is a co-owner of Ra Energy, which designs and installs solar hot-water systems. He says he has seen increased inquiries for commercial systems, which he says are far more efficient than photovoltaics for heating large quantities of water. Buildings with heavy water usage, such as industrial laundries and food manufacturers, are ideal candidates.

“You could put a football field of PVs somewhere and you still can’t heat water more efficiently than solar-thermal does,” Stevens said.

Ra Energy has installed systems for the Lucky Lab Brew Pub and the Lucky Lab Beer Hall, which use the hot water to brew beer, and is currently working on a solar-thermal system to heat a 50,000-square-foot greenhouse in Cornelius. By combining a solar-thermal hot-water system with heat pumps, the project will reduce natural gas consumption at the greenhouse from 30,000 therms per year to 10,000. A therm is a unit of heat energy equal to 100,000 BTUs.

“I feel like I’ve been an evangelist for solar-thermal,” Stevens said. “The solar hot-water industry is fragmented and driven by smaller companies. And there is so much marketing and publicity around PVs. It’s up to individuals to get the word out.”

Despite being more efficient than photovoltaic systems, solar-thermal has a bad reputation in Oregon, according to John Sorenson of Neighborhood Natural Energy, because of poor installations performed in the 1970s. As the technology gained popularity, many fly-by-night companies performed improper installations of the systems, causing roof leaks, and sometimes causing entire ceilings to cave in.

“It was the people, not the technology,” Sorenson said. “But people associated the two.”

But today, companies must meet strict training qualifications before Energy Trust will certify them to perform solar-thermal installations in commercial buildings. Qualification for tax credits is dependent on installation by a certified firm.

Bolen says tax credits can significantly lower the costs of a solar-thermal energy system. The Oregon Business Energy Tax Credit will cover 50 percent of the cost, a federal energy tax credit will cover 30 percent, and Energy Trust incentives – which are dependent on how much energy a system produces – can cover 10 to 15 percent.

One caveat is that Stevens says there is less third-party financing available for solar thermal systems than for photovoltaics. Perhaps lenders aren’t aware of economic studies that show that after four years, building owners will see an 8-percent return on investment.

“We’re working on getting some better marketing strategies that target businesses with heavy hot-water use,” Bolen said. “The only issue with solar-thermal is you can’t run the meter back. You produce the hot water and you have to use it the same day or over the next couple days. You can’t bank it with a utility company. But having steady day-to-day water usage year-round, like an athletic facility or detention center, is what makes it work efficiently.”

Sorenson says that 44 percent of the energy consumed in Oregon is in the residential and commercial sector, more than industrial or transportation.

“Why are we putting so much of our capital into photovoltaic panels when solar-thermal is three to four times more efficient and cost-effective?” Sorenson said. “It’s because people don’t know anything about it. There’s a perception that needs to be overcome.”