Solar-Assisted Residential Heat Pump to Hit Market

November 10, 2008
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“Solar thermal and PV devices are dependent on light, not heat,” said the SEIA, “and this light does not need to be direct. Put another way, if you can find your way around outside, a solar panel could be working.” This makes the system applicable throughout most of the United States.


DALLAS - Solar technology is hardly new, but the ways in which it is being applied to carry smaller portions of the load is new. Lennox Industries, for example, recently unveiled SunSource™, an integrated, solar-assisted residential heating-cooling system. It was introduced at the Association of Energy Services Professionals’ (AESP’s) 4th Technology Symposium in Long Beach, Calif., and will be available to the public in 2009.

According to the Solar Energy Industry Association (SEIA), “The most rapidly growing segment of the solar industry is for ‘grid-connected’ systems - rooftop solar panels on homes or businesses that remain connected to the conventional electrical grid.”

“We’ve taken a unique approach to solar,” said Bill Cunningham, product manager - Cooling Splits. “It’s a simple and cost-effective way of using solar in heating and air conditioning.”

This single solar panel application provides peak load control, and it offsets some of the heat pump usage, he said - a 6-8 percent reduction in full sun. “We get greater efficiency gains in lower-tonnage units,” he said. Reductions come from the condenser fan portion of the system.

A traditional HVAC system accounts for more than 50 percent of the energy consumption in a home, Cunningham pointed out. “When utilities look at places to reduce the load, the HVAC system is the place where they start.”

The technology of the solar system itself shouldn’t tax the abilities of today’s HVAC contractors, he added. The low-voltage dc system uses a two-wire connection to carry the voltage from the solar panel to the outdoor unit. “Contractors may choose to seek training specific to roof mounting of solar panels - adobe tile roofing, shingles, etc. We plan to provide the education, either internally or through a third party. I view this [technology] as an opportunity for contractors to expand their energy services.”

BRIGHT SUN NOT NEEDED

The new Lennox system integrates solar power with a traditional heat pump. A single, 190-W solar panel, which measures approximately 3-by-5 feet, provides power to assist the fan motor that moves air across the outdoor coil.

The solar panel, which should be installed so that it faces southwest for maximum exposure to the sun, offers flexibility of installation. It can be placed on the building’s roof, on a fence, or even pole mounted in a convenient location. The panel-mounting option “gives you the option to hide the panel a little bit,” Cunningham said. “None of your neighbors have to see it,” though he suspects some customers will want to have it mounted prominently on the roof, as a badge of good stewardship.

According to the company and sources including SEIA, sunny days are not necessary. Even on days with limited sun exposure, the system takes advantage of the available solar resources and reduces energy usage.

“Even in partly cloudy conditions, the Lennox SunSource can still generate a level of solar energy that is usable,” states company literature.

This makes the system applicable throughout most of the United States. According to the SEIA, “PV [photovoltaic] works across the whole country. In fact, the second leading state for PV installations is New Jersey.

“Solar thermal and PV devices are dependent on light, not heat,” the association stated, “and this light does not need to be direct. Put another way, if you can find your way around outside, a solar panel could be working. While the Southwest enjoys particularly good resources, the entire United States has adequate solar resources.”

The price of daytime electricity and the existence of incentives for clean energy is more important to the economic feasibility of solar systems than direct sunlight, explained SEIA.

This cutaway shows the interior of the solar-powered condenser unit, which will be formally introduced in early 2009.

MORE APPLICATIONS

Integrating solar power into other components of a typical home comfort system - including indoor motors, compressors, IAQ products, and thermostats - is currently being evaluated. So is the system’s ability to be used for central cooling alone.

“Future integration with the indoor section is possible,” Cunningham said. “When you do that, it’s a 12-15 percent reduction, anticipated, for both.”

“The Lennox SunSource is another step towards the acceptance of single-point solar technology applications,” said Doug Young, president and COO, Lennox International Inc. Residential Heating & Cooling. “This unique application specifically targets reducing peak demand, while improving energy efficiency and maintaining comfort.

The system is currently applied to 10 test sites throughout the country, including an engineer’s home in Dallas, said Cunningham. “It’s doing the job,” he said, with the solar panel placed about 150 feet away from the heat pump.

This shows the condenser unit with the solar panel. The solar panel can be located where convenient, so long as it has a Southwest-facing exposure.

GOOD TIMING FOR ALTERNATIVES

The timing could be ideal for solar-assisted systems. The recently passed Emergency Economic Stabilization Act of 2008 (aka, the bailout bill) includes an extension of federal solar tax credits, specifically production tax credits (PTCs) and investment tax credits (ITCs). The tax credit package will extend PTCs for one year and ITCs for eight. The extensions would be at least partially paid for by a change in the tax code for the oil and gas industry.

On the consumer end, a desire for both good stewardship and energy cost savings has increased the interest in alternative power. “It’s a trend that definitely is growing in popularity,” Cunningham said. “I hesitate to use the word green, but there is an interest in minimizing the impact on the environment and saving a little money. We also think the renewable energy side will become more attractive,” possibly through tax incentives and utility rebates.

The typical customer, he said, would be one who otherwise would be interested in a top-of-the-line system. The company anticipates that the SunSource will cost approximately $3,000-$4,000 more than a typical high-efficiency heat pump system.

“Together with the electric industry and the support of our outstanding North American dealer network,” said Young, “we can begin to make a significant, positive change in 2009.”

For more information, visit www.dsireusa.org.

Sidebar: Solar Notes

According to definitions from the Interstate Renewable Energy Council report, different solar energy technologies create energy for different end uses. Two technologies - photovoltaics (PV) and high-temperature concentrating solar thermal electric - produce electricity. A third technology (low-temperature solar thermal collectors) produces heat for hot water, space heating, pool heating, and process heat.

“Photovoltaic cells are semiconductor devices that generate electricity when exposed to the sun,” the report explains. “Manufacturers assemble the cells into modules, which can be installed on buildings or in ground-mounted arrays. PVs were invented in the 1950s and first used to power space satellites.”

Publication date: 11/10/2008

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