Common Questions About Solar Energy
Understanding solar energy can be challenging. We have gathered a number of questions we hear most often at Kyocera Solar. If you have other questions, please contact us at firstname.lastname@example.org.
- Q1: How do solar cells generate electricity?
- Q2: Will solar work in my location?
- Q3: How much will a system cost for my 2000 square foot home?
- Q4: Can I use all of my normal 120/240 VAC appliances?
- Q5: What components do I need for a grid-tie system?
- Q6: What components do I need?
- Q7: Can I use PV to heat water or for space heating?
- Q8: Are incentive programs available in my state?
- Q9: What happens to my system when it's cloudy or dark outside?
- Q10: Is solar electricity really cost-effective?
Q1: How do solar cells generate electricity?
A1: Photovoltaics or PV for short can be thought of as a direct current (DC) generator powered by the sun. When light photons of sufficient energy strike a solar cell, they knock electrons free in the silicon crystal structure forcing them through an external circuit (battery or direct DC load), and then returning them to the other side of the solar cell to start the process all over again. The voltage output from a single crystalline solar cell is about 0.5V with an amperage output that is directly proportional to cell's surface area (approximately 7A for a 6 inch square multicrystalline solar cell). Typically 30-36 cells are wired in series (+ to -) in each solar module. This produces a solar module with a 12V nominal output (~17V at peak power) that can then be wired in series and/or parallel with other solar modules to form a complete solar array to charge a 12, 24 or 48 volt battery bank.
Q2: Will solar work in my location?
A2: Solar is universal and will work virtually anywhere, however some locations are better than others. Irradiance is a measure of the sun's power available at the surface of the earth and it averages about 1000 watts per square meter. With typical crystalline solar cell efficiencies around 14-16%, that means we can expect to generate about 140-160W per square meter of solar cells placed in full sun. Insolation is a measure of the available energy from the sun and is expressed in terms of "full sun hours" (i.e. 4 full sun hours = 4 hours of sunlight at an irradiance level of 1000 watts per square meter). Obviously different parts of the world receive more sunlight from others, so they will have more "full sun hours" per day. The solar insolation zone map on the right will give you a general idea of the "full sun hours per day" for your location.
Q3: How much will a system cost for my 2000 square foot home?
A3: Unfortunately there is no per square foot "average" since the cost of a system actually depends on your daily energy usage and how many full sun hours you receive per day; And if you have other sources of electricity. To accurately size a system to meet your needs, we need to know how much energy you use per day. If your home is connected to the utility grid, simply look at your monthly electric bill. Using this information, your authorized Kyocera solar Dealers can design a system to meet you needs.
Q4: Can I use all of my normal 120/240 VAC appliances?
A4: Maybe. Many older homes were not designed or built with energy efficiency in mind. When you purchase and install a renewable energy system for your home, you become your own power company so every kWh of energy you use means more equipment (and hence more money) is required to meet your energy needs. Any appliances that operate at 240 VAC (such as electric water heaters, cook-stoves, furnaces and air conditioners) are impractical loads to run on solar. You should consider using alternatives such as LP or natural gas for water/space heating or cooking, evaporative cooling instead of compressor based AC units and passive solar design in your new home construction if possible. Refrigeration and lighting are typically the largest 120 VAC energy consumers in a home (after electric heating loads) and these two areas should be looked at very carefully in terms of getting the most energy efficient units available. Great strides have been made in the past 5 years towards improving the efficiency of electric refrigerators/freezers. Compact fluorescent lights use a quarter to a third of the power of an incandescent light for the same lumen output and they last ten times longer. These fluorescent lights are now readily available at your local hardware or discount store. The rule of thumb in the renewable energy industry is that for every dollar you spend replacing your inefficient appliances, you will save three dollars in the cost of a renewable energy system to run them. So you can see that energy conservation is crucial and can really pay off when considering a renewable energy system.
Q5: What components do I need for a grid-tie system?
A5: Grid-tie systems are inherently simpler than either grid-tie with battery back-up or stand-alone solar systems. In fact, other than safety disconnects, mounting structures and wiring a grid-tie system is just solar modules and a grid-tie inverter! Today's sophisticated grid-tie inverters incorporate most of the components needed to convert the direct current form the modules to alternating current, track the maximum power point of the modules to operate the system at peak efficiencies and terminate the grid connection if grid power is interrupted from the utility.
Q6: What components do I need?
A6: There are many components that make up a complete solar system, but the 4 main items are: solar modules, charge controller(s), batteries and inverter(s). The solar modules are physically mounted on a mount structure (see question 7) and the DC power they produce is wired through a charge controller before it goes on to the battery bank where it is stored. The two main functions of a charge controller are to prevent the battery from being overcharged and eliminate any reverse current flow from the batteries back to the solar modules at night. The battery bank stores the energy produced by the solar array during the day for use at anytime of day or night. Batteries come in many sizes and grades. The inverter takes the DC energy stored in the battery bank and inverts it to 120 VAC to run your AC appliances.
Q7: Can I use PV to heat water or for space heating?
A7: No. Photovoltaics converts the sun's energy into DC electricity at a relatively low efficiency level (14-16%), so trying to operate a high power electric heating element from PV would be very inefficient and expensive. Solar thermal (or passive solar) is the direct heating of air or water from the heat of the sun and is much more efficient for heating applications than photovoltaics.
Q8: Are incentive programs available in my state?
A8: Yes, incentives are available through the California Solar Initiative (CSI), which is authorized by the California Public Utilities Commission (CPUC). The program, which began on January 1, 2007, has a total budget of $2.165 billion to be distributed over 10 years. Municipalities and local utilities may have different or additional incentives.
For more information, direct to dsire page: http://dsireusa.org/ or PV calculator
Q9: What happens to my system when it's cloudy or dark outside?
A9: Your solar electric system will not produce electricity without direct or diffused sunlight. On cloudy days you will still be generating electricity though not as much as on sunny days. During cloudy days and at night, you can draw electricity from the grid. You build up credits on sunny days and draw from these credits on cloudy days and at night.
Q10: Is solar electricity really cost-effective?
A10: It depends on a number of factors but frequently YES. With decreasing costs, the systems are becoming more attractive for a larger segment of the population. In fact, in many cases a solar system can provide returns higher than the stock market average. An authorized Kyocera dealer can provide a free site evaluation and estimate what your return on investment will be and how much you will save over the life of the system. ??The economic attractiveness of the system is tied to what future utility rates will be. This is difficult to predict but historically rates have increased 5.5% annually since 1970.