A Few Things to Know About Solar

Thinking of saving electricity by investing in a solar photovoltaic (PV) system? Here are a few good things to know, pulled from a recent Greenbiz.com webinar on Solar Powered Buildings: Worth Another Look as Prices Fall.

Powerhouse Solar Shingles

Federal tax credits— The 30 percent residential renewable energy tax credit is good through 2016. This gives you up to a 30 percent credit for the cost and installation of a solar PV, solar thermal, wind, geothermal heat pump and fuel cells. There is no ceiling, and excess credit can generally be rolled forward to the next tax year. So if you’re interested in solar technology, it’s a good idea to start pricing and planning now. You can find federal and local incentives at dsire.com

Micro-inverters— The traditional solar PV setup includes an inverter that converts the DC energy created at the solar panel to AC for your home’s use. But one inverter for an entire array can pose limitations on how much energy you realize from your PV system. It’s complicated, but by using one inverter, a solar panel that’s shaded or not performing well can lower a centralized inverter’s maximum power point, and thus the amount of electricity you receive from the system. So in some smaller systems, a micro-inverter is used for each panel. These cost more, but your system may perform better. Some reports indicate that micro-inverters can boost energy harvesting in residential systems up to 15 percent.

DC optimizers—< Also called power boosters, these can be placed on every panel and used with a central inverter to maximize the power coming from the panels and eliminate issues such as shading on one of more panels.

Costs— According to Greg Sheppard, chief research officer for IHS iSuppli, residential solar costs continue to fall, from about $2.50 per watt per module (or panel) in 2009 to about $1.50 per watt today, and costs are expected to drop to almost $1 per watt (or about $200 per panel) in 2015. Though these are panel costs, not installation costs. According to the Open PV Project from NREL (National Renewable Energy Lab), the average cost for solar panel installation in the United States was $6.94 per watt in 2010. Manufacturing costs will certainly continue to decline. “Manufacturing is a lot more efficient,” Sheppard says. “A lot of [assembly of solar panels] was done by hand up to a couple of years ago.”

Thin Films are Coming— Most solar panels today are made with crystalline silicon, though expect to see more flexible, thin panels that use technologies like CIGS (copper indium gallium selenide), Cadmium Telluride (CdTe), and amorphous silicon, though for now the efficiencies of crystalline silicon are better. The best efficiencies in available high-end monocrystalline silicon panels are about 19 percent, according to Sheppard. Look for thin-film technologies in BIPV (built-in photovoltaic) systems like roofing shingles. This year Dow Chemical will introduce its Powerhouse Solar roofing shingles, with the solar panels provided by Global Solar. The flexible CIGS panels are built right into asphalt shingles.

Energy Monitoring— Good energy monitoring systems exist for solar arrays, and are recommended to properly measure a PV system’s performance. An inverter, for example, will display the output of electricity but not what goes into it. So an improperly working inverter may go unnoticed without energy monitoring. Systems that can monitor a solar array’s energy production include eMonitor, EcoDog and Agilewaves.