Renewable energy for your customers’ domestic hot water

Many Americans are surprised to learn that heating domestic water is the second largest use of energy within the home (second only to home heat at up to 50% or more).  Fortunately, the sun’s abundant energy is easily harnessed for the task.

Solar expert Dave Yates, president of F. W. Behler, Inc. in York, Pa., a full-service mechanical contracting and hvac firm, recalls a moment from early parenting.  “Are we there yet Dad?”  Many of us hear it, too:  the persistent refrain from the back seat on long vacation trips.  Yates is still in the driver’s seat, and it’s his customers who implore:  “Are we there yet?”

The newest wave in energy these days -- actually, more like a tsunami in the burgeoning green industry -- is renewable energy. All things green, with solar power at the top of the list. And, unfortunately, it’s a long journey home.

Yates missed the first solar revolution in the 1970s. Inspired by Jimmy Carter’s “Our neck is stretched over the fence and OPEC has a knife” speech, he built an insulated solar panel in his back yard. There were no installation standards in place and, said Yates, “It was an every man-for-himself, Wild West approach with not a single sheriff in sight!”

Yet at the time, it looked so simple. All that was needed: a solar collector mounted to face south and tilted toward the sun; water pumped through collectors; and a vessel to store the heated water. That’s how solar wildcatters did it in the ’70s and that’s also why very few systems survived. Of course, when the oil spigot was reactivated, we merrily bought bigger cars, homes and heating systems.

Things have changed with a vengeance. All things green have, at last, grabbed the attention of governments, businesses and consumers. How else could we respond to the looming threat of global

warming as ice continents melt away, and energy costs consume us?

Yates encourages his customers to explore and learn about the technology. Of course, there’s a lot of misinformation on the Web, but so much useful information, too. Solar Today and Home Power magazines are both excellent resources. He also purchased the following books: Solar Hot Water Systems by Tom Lane (see: www.ecs-solar.com/lessons_learned.htm); Planning and Installing Solar Thermal Systems and Planning and Installing Photovoltaic Systems -- both available through James & James (see: www.jxj.com).

But even for a pro like Yates, the information overload can be daunting. Of the thousands of solar heat systems components available today, he asks: “Which of them will work well together? I wanted cold, hard facts and a system-wide approach that would ensure reliability and the best performance. After all, if I’m going to promote and sell solar systems to customers, then I’ll need well-engineered technology with excellent performance and the prospect for a long life.”

While attending the ish expo in Germany a few years ago (the world’s largest plumbing and heating trade show), Yates visited Viessmann’s technician training school. Immediately impressed, he then attended training sessions at the manufacturer’s facility in Warwick, Rhode Island where he also received an introduction to their line of solar systems. “The emphasis being ‘systems,’” said Yates, “rather than just a few components.

“No mysteries -- just system-wide solutions: I felt like I’d arrived home.” (See: www.viessmann-us.com).

Yates was relieved to learn that before purchasing a Viessmann solar system, there is a detailed survey to complete to ensure the solar system will perform properly. In addition to training installers on proper assembly and commissioning of solar systems, training includes monitoring pH and testing glycol concentrations with a refractometer (See: www.apexbattery.com/lighted-glycol-refractometer).

Some of the basics learned: Solar systems involve the same dangers that contractors already face. Electrical work, roof penetrations, plumbing, and working with heavy components . . . on rooftops instead of basements. Permits and inspections are often required.

A solar system needs to tilt at, or close to, your latitude, which happens to be 39° for Yates’ York, Pa. location. Yates’ own roof pitch is at 37° with a 9/12 pitch, which makes a treacherous slope. “In the blink of an eye a fall can happen, so when we installed our own solar heat system for household water last year, we used a well-anchored safety harness and roof jacks and planks,” said Yates.

There’s also the issue of hot water safety. “Dealing with a hot water heating system that can’t be turned off meant that our potable hot water storage temperatures would fluctuate and, at times, rise well above scalding ranges. A must-have item is an asse certified 1017/1016 thermostatic scald-guard valve at the storage tank’s outlet,” added Yates.

One surprise for Yates reminded him of the old real estate adage, “location, location, location.” Though their home faces due south, he naively assumed that most, if not all, of their south-facing roof was suitable for panels. Trees that he thought were far enough away turned out to be shadow-casters during the late afternoon. “My solar real estate suffered major shrinkage,” he said in dismay. But fortunately there was one brightly lit spot just right for a solar array. And that’s where Yates planted the panel. It’s also good to note that roof direction and pitch aren’t necessarily a deal-breaker for solar panels. There are many panel frames that provide offsets for tilt and orientation.

Yates recalled a few “devil in the details” moments along the trail to roping-in the sun. Selecting a spot for the 120-gallon storage tank was easy. However, getting from roof panel to storage tank was not so easy.

The first impediment was the deal-breaker. When he first suggested the idea of installing roof-mounted solar panels, his bride replied, “They’d better not be ugly or you’ll be removing them!” So Dave produced detailed photos and illustrations, going so far as to show how they’d look on the roof by cut-and-paste digital photography. Lois Yates acquiesced, leaving Yates to the task of making it come together mechanically.

The connections between roof to basement, as it turned out, was a challenge, chiefly because the job would be a retrofit, not a new home installation. The easy way was to route insulated tubing through the garage beside a doorway they used each day. “Our only acceptable route was to drill through a number of joists that rest over the concrete garage floor -- a real stretching exercise and, as it turned out, the worst part of the entire installation,” said Yates. “But we got ‘er done.”

Yates’ closed solar loop is what’s called an “active system” filled with a 50/50 mix of water and glycol. It bears great similarity to most closed-loop hydronic (hot water heat) zones in that careful attention is required to “think like water” and how it will flow. A key need is to avoid a rise in system piping, followed by a fall. That’s where air will sit tight, causing a problem, stopping flow. Given that we wouldn’t be able to turn off the sun whenever we experienced a system malfunction, the fluid trapped in the roof’s solar array would quickly turn to steam and its glycol would suffer degradation. Ensuring the elimination of air is critical.

There were just a few remaining pieces of the puzzle to contemplate:

Yates loses power about six times a year. Typically, he returns home from work to a house-full of blinking digital clocks. Now that he’s dealing with solar, power loss meant trouble. Generating steam in the solar array would quickly occur and the resulting temperatures and pressure spike would both degrade the glycol and a potential relief-valve dump to the system’s catch-basin.

Though he has a whole-house generator and transfer switch, it’s not (yet) an automatic system. He wasn’t yet ready to install a solar PV (photo-voltaic) electric generating system, yet very much wanted a reliable back-up. The Viessmann Divicon incorporates the epicenter for power to operate the differential sensor control and a Grundfos low-watt circulator. He bought an inexpensive backup battery power-pack to carry them over short-term power outages. For an added measure of safety, the Viessmann Solar System package includes an oversized thermal expansion tank designed to accept the full volume of the collector and higher pressure if steam is created during stagnation.

There was one remaining concern. He can’t turn off the sun at will once the storage is up to maximum temperature, which can be above 200 F with a vacuum tube system! A reliable means for shifting excess solar energy was needed so that they could go away for more than a day without concern. He’ll soon solve that with a small radiator, typically used as an oil cooler for motorcycles. It will be put to use with a 12-volt computer-tower fan, powered by a small PV panel. For the present, they’ll automatically shift the excess sun’s energy into their sidewalk and garage snow-melt systems. He will soon expand the solar array, adding a large thermal-storage vessel so that they can harness and store the sun’s energy to supplement the home’s hydronic radiant heating. By using load-shifting between the domestic and

hydronic storage vessels, they’ll be able to “cut the gas line” for their domestic hot water.

For a complete listing of Federal and state-by-state tax and rebate incentives, visit the “Database for State Incentives for Renewable Energy” (www.dsire.org).

The Federal Government’s tax incentive program can offset a solar investment by as much as 30% up to a maximum of $2,000.00 for qualified solar hot water systems and an additional credit of equal value for solar pv systems (www.fsec.ucf.edu/EPAct-05.htm#solar).

Partnering with a company whose system is already listed as approved can also help. This credit is applied against taxes owed, so it might be necessary to alter payroll deductions to ensure maximum use of any credits. The great news is that “payments” begin with an advance on your tax credit! As author Tom Lane puts it, that’s tax free money and that means every dollar is worth an average of $1.30 (www.ecs-solar.com/solar_tax_credit.htm).

In order to qualify for the Federal or state tax credits and/or rebates, systems might need to be certified for performance by the non-profit Solar Rating Certification Corporation (www.solar-rating.org/) or a comparable entity endorsed by your state government.

Yates installed the Viessmann vacuum tubes on a Thanksgiving weekend during cloudy weather. The following day, while they installed the vacuum tube clips, the sun was out in full force and they gained 30,000 Btus. His storage tank holds 120 gallons, which weighs 1,000 lbs. and they had a 30° rise. (An 82% efficient water heater would have used 37-cubic feet of gas to provide a net of 30,000 Btus). For the next several weeks he had solid cloud cover. A vacuum-tube array continues to harvest solar energy in cloudy weather and he saw a net gain of 2,000 to 10,000 BTUs per day.

When spring arrived, the solar array was harvesting 25,000 to 28,000 Btus on sunny days, and 33,000 to 45,000 Btus in June, July and August while supplying all of the home’s domestic hot water needs -- liquid sunshine!

“Are we there yet Dad?” wonders Yates. No, but the long journey home has begun.