Ask an Expert

Q:What is a solar tracker?

A:

A solar tracker is a mechanical device used for orienting photovoltaic panels towards the sun. Solar powered equipment works best when pointed at or near the sun, and trackers can increase the total output of a PV module by 30-50% versus if they were mounted in a fixed position. There are a variety of trackers available on the market, but the most common is a motorized version that is used in conjunction with a timer or light sensor to move the module to the most efficient position based on time of day or the heading of the sun. Trackers are designed to draw electricity for their motor from the attached photovoltaic modules and can be set up to draw from a wide variety of voltages.

08-31-2009 by CalSolar Category: Solar Panels

Q:What is a solar charge controller?

A:

A charge controller, or charge regulator is similar to the voltage regulator in your car. It regulates the voltage and current coming from the solar panels going to the battery. Most "12 volt" panels put out about 16 to 20 volts, so if there is no regulation the batteries will be damaged from overcharging. Most batteries need around 14 to 14.5 volts to get fully charged.

08-24-2009 by DeanS Category: Solar Panels

Q:What do they mean when they talk about the efficiency of photovoltaic modules?

A:

PV conversion efficiency is the ratio of the electric power produced by a PV device to the power of the sunlight shining on the device. Cell efficiency defines how much energy in sunlight is actually converted into electricity. For example, if the sun is at 100% of potential energy on a cloudless day and the PV module has a 15% efficiency rating under the same conditions, 15% of the potential energy is being actualized into direct current (DC). Thin-film (also known as amorphous) silicon modules have lower efficiencies than crystalline materials. The efficiency of both thin-film and crystalline modules have improved markedly in recent years. Cell efficiency degrades progressively with use, and are typically rated to the nameplate efficiency standard for a period of 20 years.

08-11-2009 by CalSunGuy Category: Solar Panels

Q:Is my solar array insurable?

A:

If you buy solar panels and install them on your house, your insurance policy will likely cover them, just as they insure the rest of your property under a homeowners' policy. But make sure you read your insurance policy's terms and provisions carefully to see if there are any exclusions and consult with your insurance agent.

07-21-2009 by Dean Category: Solar Panels

Q:My lights have been out all day, but lights are not on. How can I make my lights work? Is there a switch to turn the lights on?

A:

Most solar lights operate with a light sensor to automatically switch the bulbs on and off when there is less than 20% available ambient light. However, there is a large variety of solar lighting products, and some of them are equipped with an on/off switch as well. This enables the user to override the light sensor to turn the lights off if they would like to do so. If a solar lamp contains an on off switch, it is listed in the product ‘specs & features' tab on our product page.

07-21-2009 by Name Category: Solar Lights and Garden

Q:Should I get a solar electric or solar thermal system?

A:

There are advantages to choosing either solar electric or solar thermal for your home or business. Both allow you to produce your own renewable energy safely and both are eligible for generous tax incentives and financial benefits through local, state, and federal government programs. However, here are some of the pros and cons of each that may influence your decision:

Benefits of solar electric systems:

• Solar PV systems produce energy year-round; their performance is not diminished with colder weather. 
•  A solar electric system can be grid-tied, allowing you to be paid by your local utility company for any excess energy your system produces.
•  Some feel that a solar PV system has less obtrusive appearance once installed than a solar thermal system.

Benefits of solar thermal systems:

• A solar thermal system will require a lower up-front cost and a give you a faster return on investment.
•  The efficiency of a solar hot water system is much higher than a solar electric system.

Update: July 20, 2009. We just posted a video in our community section under solar water heater videos that highlights some of the differences between solar electric and solar thermal.

07-12-2009 by GreenGirl Category: Solar Water Heaters

Q:Do I need batteries for my solar power system?

A:

If you live in an urban area and have your solar electric system grid-tied to your local utility, you will not require batteries for your system. Any energy produced by your solar array that is over and above what you use at any given moment will be pumped into your local utility system, negating the need for batteries for energy storage. If you live in a remote location or in a community without a net metering program, you may wish to purchase batteries to make the most out of any excess energy your system produces throughout the day.

07-11-2009 by DiggerDan Category: Solar Panels

Q:Is my roof big enough for a solar system?

A:

Ultimately, the amount of space you will require for your solar PV system will depend on how much energy you want to produce. According to the US Department of Energy, for every Watt of energy to be produced you'll require 10 square feet of space. But remember, your solar electric system doesn't have to be installed on your roof. Pole-mounted and ground-mounted systems also exist, giving you greater flexibility should you require additional room. For a solar thermal system, on the other hand, the Energy Information Administration estimates that the average system size is between 199 and 187 square feet.

07-10-2009 by Liz579 Category: Solar Panels

Q:Where can I get incentives for purchasing a solar system for my home?

A:

It has never been easier to get financial assistance from local, state, and federal renewable energy programs. Start by checking the Database of State Incentives for Renewables and Efficiency for the most comprehensive listing of incentives and rebates for both homeowners and business owners. Then look into what is offered by your state's energy office. A list can be found on the US Department of Energy's site: http://apps1.eere.energy.gov/state_energy_program/seo_contacts.cfm. We are also blogging about the incentives offered in several critical states and profiling homeowners who have taken advantage of these incentives. Check out the solar blogs on our community page.

07-09-2009 by GreenGirl Category: Solar Water Heaters

Q:Can I sell my excess solar power back to the utility grid?

A:

Most urban utility companies now have a net metering program in place, requiring that your solar system be tied to the utility grid. This means that when your solar array produces more energy than your home consumes, the excess energy is pumped back into your local utility system rather than into a battery. Your utility will then pay you (usually at the same rate charged to you) for any extra energy you produce.

If, however, you live in a region without a net metering program, you can either choose to have your solar installed off-grid (which would require that you have a battery system for storing excess energy) or opting for another form of renewable energy, such as a solar thermal system which remains cost-effective even without net metering.

07-08-2009 by GreenandSolar Category: Solar Panels