California homeowners lead the rest of the country in residential solar installation as well as the purchase of do-it-yourself solar kits. Solar systems are not just an environmental decision for homeowners, but maybe more importantly, a cost saving one. There are a few things a homeowner (If you are installing yourself) or your solar contractor should consider when designing a system for your home or cabin.
Shading possibilities, slope and orientation, longevity of the solar panel manufacture and of course costs are some of the more important considerations for solar system design. We will point out a few basic solar application principles wither you live in California or outside the golden state.
Solar shading
Because solar panels are generally tied together in strings (Christmas Tree Light String Effect), even if one cell of one panel is shaded, you can substantially reduce the amount of energy the solar string will product or knock it out completely. This important solar design factor is often overlooked by too many California solar contractors. It is one of the first things an experienced solar installer will check when they get that “my solar panels are not producing power like my solar contractor said they would” … call.
Solar panels are very sensitive to shading. Unlike a solar thermal panel which can tolerate some shading, many brands of solar panels modules cannot even be shaded by the branch of a leafless tree.
Solar shading obstructions can be defined as soft or hard sources. If a tree branch, roof vent, chimney or other item is shading the solar panel from a distance, the shadow is diffuse or dispersed. These soft sources significantly reduce the amount of light reaching the cell of a solar panel. Hard sources are defined as those that stop light from reaching the solar panel cell, such as a blanket, tree branch, bird dropping, or the like, sitting directly on top of the glass. If even one full solar cell is hard shaded the voltage of that module will drop to half of its unshaded value in order to protect itself. If enough solar cells are hard shaded, the module will not convert any energy and will, in fact, become a tiny drain of energy on the entire system.
Partial-shading even one solar cell will reduce its electrical power output. Because all solar cells are connected in a series string, the weakest solar cell will bring the others down to its reduced power level. Therefore, whether ½ of one solar cell is shaded, or ½ a row of solar cells is shaded as shown above, the power decrease will be the same and proportional to the percentage of area shaded, in this case 50%.
When a full solar cell is shaded, it can act as a consumer of energy produced by the remainder of the cells, and trigger the solar panel to protect itself .The solar panel will route the power around that series string. If even one full solar cell in a series solar string is shaded, as seen on the right, it will likely cause the module to reduce its power level to ½ of its full available value. If a row of solar cells at the bottom of a module is fully shaded the power output may drop to zero. The best way to avoid a drop in output power is to avoid any type of solar shading when possible. (Source Kyocera Solar)
Solar Panel Design Considerations
Solar shading is a fundamental design consideration. However, over the last couple of year, solar micro inverters have become dramatically popular because of their added flexibly. The inverter is the brains of any solar system because it maximizes the solar system power output and syncs up with the electrical grid. One popular Northern California solar micro inverter manufacture, Enphase Energy, has taken the market by storm with 2 – 3 other solar inverter manufactures working hard to catch up.
The solar micro inverter works great in situations where there is a possibility of solar shading or when you have different roof orientations. Solar micro inverters are resilient to dust, debris and shading because you have no single point of failure. What that means, if you have one solar panel being with shading as shown in the example, the other solar panels operate independent of each other.
Solar Panel Tilt and Orientation Factors
To produce the highest electrical output a solar panel can generate, in most areas of Northern California a 30 degree tile (7/12 pitch) and a South orientation will produce the most energy. Annual solar harvesting is a function of panel orientation all other factors being equal. Tilt and Azimuth being the two strongest factors.
To compare the energy output of your solar array to the optimum value, you will need to know your home or cabin’s latitude, and the actual tilt angle of your array-which may be the slope of your roof if your array is flush-mounted. If a south-facing roof is unavailable, or the total solar panel array is larger than the area of a south-facing roof section, an east or west-facing surface is the next best option.
Solar panel prices differ, based upon several unique aspects. Initially, you must select how many panels you need installed in your house and even office. Solar panel prices are as adjustable depending on the configuration options available.
Solar Panel Prices
In the last 5 years there has been a rush to increase the availability of solar panels thereby creating a market condition that have been pushing down prices. Over the last 24 months the price of solar panels has dropped by as much as 50% so it is unlikely the current cheap solar prices are sustainable.
Greater solar panel manufacturing capacity has led to the price of California residential solar installations also falling due to cheap solar panels and improved module efficiency. In a study by Lawrence Berkeley National Laboratory, in the first ten months of 2010, the installed cost of solar PV systems fell by $1 per watt (DC), or a 14 percent drop in California, and by $1.20 per watt in NJ, which a 16 percent reduction. California is by far the largest market for solar panels in the U.S. with about three-quarters of the solar installations in the country. (Source; CNET)
In 1998, the cost to have solar panels installed was $10.80 per watt. The price in the first 10 months of 2010 in California was about $6.50 per watt, although prices vary significantly in other states, the study found. The overall downward trend in prices suggests that the solar industry has been successful in introducing more competition to spur efficiencies in delivering product.
An uncapped 30 percent federal solar tax credit for solar installations (hot water or photovoltaics) remains in effect until 2016. Solar rebate and tax credits from state programs vary.
Solar Panel Manufactures Longevity
When considering purchasing a California solar installation or pre-packaged solar kit, low-cost panels can be tempting but there are risks. While important, price should be weighed against the solar panels manufacturer’s longevity. Consider how good a 25 year solar panel warranty is when the company has not been in business for over 5 years. What’s more, in California, if you are having a local solar installer design and install your home solar system, they are required to warranty the installation for 10 years. If the cheap solar prices you have been quoted are too good to be true, well… you know.
Solar Installation and Beyond
If a home solar system is installed property, solar systems are almost maintenance free. It is rare when a solar system is broken. It is a good idea, especially here in Sacramento, to occasionally wash off your solar panels with a garden hose. Cleaning your solar panels is more important for low tilt angles and low rainfall areas, and dirty areas IE; near farms or freeways. Around year 15, your solar inverter will have to be replaced. Most reputable California solar installers will have calculated the cost of replacing the inverter in the long-term solar return on investment in your initial proposal.
About Blue Pacific Solar – Blue Pacific Solar is a Sacramento California-based solar dealer specializing in pre-packaged solar kits and integrated residential solar systems for all types of applications. A variety of pre-packaged kits are designed for residential solar systems, off-grid or stand-alone solar battery power kits as well as portable solar panels. Through its affiliate, Santa Cruz California headquartered, Suns Up Solar, Blue Pacific Solar is marketing installed residential solar throughout California.