String inverters and microinverters each have  their own advantages and disadvantages.

An inverter is a critical component in a solar power system. The inverters function is to convert  the direct current (DC) of the solar panels into alternating current (AC) that can be fed into the electrical grid or used directly by standard electrical devices. In solar power installations, a number of solar modules are wired in series, creating a solar array or string.  Multiple strings are then connected in parallel to a central inverter that feeds the grid.

In contrast, a solar microinverter is a small device installed on the back of each solar panel that converts DC from a single solar panel to AC. The electric power from multiple microinverters is then combined and fed into the grid. The two approaches each have distinct advantages and disadvantages which varies  for different kinds of installations.

String Inverters

Inverters are a major part of the cost of a solar power installation. Central string inverters offer substantial economies of scale in large systems, particularly those in excess of 100 kW in size. For utility-scale PV systems, total costs including operating and maintenance costs are major and  therefore, large central inverters are dominant in that market.

The main shortcoming of the central inverter is that when solar panels are strung together in a  string, the panels performance is limited by the worst of the individual panels within it. If a single panel is shaded, its output drops dramatically, thus affecting the output of the entire string of panels even if the other panels are not shaded. In addition, inverters use a technique known as maximum power point tracking (MPPT) to optimize solar power output by adjusting applied loads. Once again, variations in an individual panel in a string will cause the inverter to change the MPPT settings, thereby deviating from optimal performance.

Microinverters

Microinverters have several advantages over conventional central inverters. The main advantage is that since each panel has its own inverter, reducing or even losing the output from a single panel does not affect the output of the entire array. Each microinverter is able to obtain optimum power by performing MPPT for its own panel. From a maintenance/reliability perspective, the failure of a single panel or inverter in this type of system will have a minimal impact on overall system performance.

 Microinverter-based solar power systems also simplify the overall system. They eliminate DC wiring, high-voltage DC switch boxes and protection circuits, and the facilities that house central inverters.

 Microinverters have become common where array sizes are smaller and maximizing performance from every panel is an important consideration. In residential or light commercial systems, the differential price-per-watt for the inverters has less effect on overall system investment. The improvement in energy collection given a fixed size array can offset this difference. For this reason, microinverters have been most successful in the residential market, where limited roof space and multiple sources of shade constrain system performance.

Germany holds 7 of the top 10 most efficient inverters in the World. Not surprising as Germany holds the top spot for photovoltaic installations with 7.74  GW’s (see graph below).  Second place goes to Italy with  3.74 GW’s installed. Below are the top ten inverters and their efficiency ratings:

1. Steca                      98.6%
2. Sunways               97.8%
3. Fronius                 97.7%
4. Diehl Ako             97.7%
5. Voltwerk              97.7%
6. SolarEdge             97.6%
7. Mastervolt           97.5%
8. Mirsibushi            97.5%
9. Solutronic             97.4%
10. Fefu                          97.4%

(This information was compiled from product data sheets).

The solar inverter market leader in terms of market share, SMA, is positioned just under the best ten companies. The difference in the claimed maximum efficiency between Steca and SMA is 1.6% .  In actual  applications, the energy losses through inverters should be considered over the 10-15 years’ lifetime and efficiency in real-life conditions.

Source: Solarbuzz Marketbuzz 2010

*Market size definition based on PV systems installed and/or delivered to site.

Sun City Solar has installed several of these inverters. If you would like further information on any of these inverters or others, visit our website.

The efficiency and quality of a solar power system  are measured by the efficiency and quality of each individual component of the system. An accurate choice of components, especially the modules and inverters is of fundamental importance for your solar power system to operate at it’s optimum performance.

A Photovoltaic solar power system must be able to function efficiently for 25-30 years in all weather conditions and under the hot summer sun.

Grounding Hardware

What is commonly called in the Photovoltaic  industry “BOS” (Balance of System), i.e. the “rest of the system” (rails, grounding, surge protection, wire, cables, etc.), plays a very important role in ensuring that you and your home or building are properly protected and have adequate power production for many years to come.

From an economic viewpoint, it is even more important for each individual component of a solar power system to be chosen on the basis of the warranties provided by the product and its manufacturer than for a normal electric system. Why? Because the operating specifications of each device must remain unchanged throughout the entire life cycle of your system and investment.

Sun City Solar Energy is dedicated to providing reliable products from the direct current (DC) side through to the Alternate Current grid connected point. In fact, the solar panel we suggest, after careful research, has a 30 year unprecedented warranty!

Back-up power allows you to continue using certain (or all) appliances when utility provided electricity is not available.

If a storm knocks out your power or you simply want to disconnect from the grid, a back-up power system with a bank of batteries can be kept charged with solar panels OR BY THE GRID WHEN IT IS OPERATING and can supply power for a limited amount of time, depending on how many batteries you have and your battery charging method.

Here are your choices in order of complexity and cost:

1) Install an Emergency Battery-Based Back-Up System which can be kept charged by the grid when the grid is on line. This system will provide power until the batteries are depleted.

2) Install a battery-based backup system which can be kept charged with either  your utility provider, a generator or solar panels. This can work in a home or business that has grid power or in an off-grid situation where there is no grid power.

3) If you already have a Solar Power Grid-Tie system, you can install a battery-based back-up system which can be kept charged with the grid, when grid electricity is available or with your grid-tie system’s solar panels even when the grid is down. This can be planned at the time of purchase of your grid-tie system, or it can be added later.

Sun City Solar Power Battery Back Up Installation Little Rock, Arkansas

 When planning your back-up power system, the back-up power must be sent to a sub-panel that is not directly connected to your main AC service panel.

During a power outage, power will be supplied only to the backed up sub-panel, not to the main panel. This requires that you relocate specific circuits that you wish to have powered when the grid is down, to the new sub-panel. This is best accomplished by a solar company with licensed electricians.

The reason for this is twofold. First, if you were to send the “AC out” from the back-up system to your main panel, you would be back feeding a “down” grid. This is illegal and dangerous. Secondly, when the grid is “up”, power will be flowing, unregulated, back through the “AC out” connection on the back-up system. This means the state of charge on the battery bank is not regulated and the batteries will be overcharged and ruined.

When the grid is “up”, power will flow from the main panel through the battery back-up system to power the loads / circuits in the sub-panel. This power is limited by the power transfer capability of the inverter.  Sun City Solars’ technicians can help find the products that are right for you. For pricing and product information give us a call at 918-494-0886. We’ll also answer any questions you might have .

Sun City Solar installed a Commercial Solar Power system with the mounting hardware designed specifically for membrane roofs. Membrane roofing is a type of roofing system typically for commercial  buildings. It is used on flat or nearly flat roofs to prevent leaks and move water off the roof. Therefore, while membrane roofs are great, penetrating them can lead to leaks.

This solar mounting system is the only all stainless steel mounting system on the market today.  Here are pictures of the non-penetrating install:

Anything that blocks sunlight from your solar panels, such as tree branches, dirt and leaves can reduce your energy output. The Solar Electric Power Association (SEPA) states that energy output can be decreased by about 10% due to dirt and other residues. In areas with heavy bird droppings, pollution, dust or pollen, the efficiency can decrease as high as 15-20%. Sun City Solar recommends you clean your solar panels as part of your regular home maintenance. Clean panels will also maximize your investment and allow you to use all of the energy output available.

For convenience, hosing off the solar panels should get them clean enough to improve efficiency. However, if cleaning the solar panels requires more than a hose (for bird droppings and such), you will need to manually clean the solar panels with a brush and water.

To clean your solar panels manually, here are some factors to consider:

• It is recommended you NOT use soap and use SOFT water where possible. Hard water (with a high mineral content) can eventually build up heavy deposits.
• Never climb onto the array – use a soft brush with an extension pole. Boat cleaning brushes (around $30) are the best.  Boat cleaning brushes are designed not to scratch and offer flow-through handles which deliver water right to the bristles.
• If chemical cleaning is required, use a detergent that will not damage aluminum. Many domestic detergents can damage panel frames and clamps.
• For large arrays, a commercial window cleaning system is advised. These brushes can extend up to 30′ and will deliver deionized water directly to the glass surface to remove dirt and leave no deposits.
• Never power wash the solar panels.  The high pressure may dislodge wiring or damage the shingles around the roof mounts.

Solar panels benefit from natural cleaning from rain which usually removes most of the dirt and grime. How often you clean your panels is determined by the weather in your part of the country. For areas with less dirt, it is recommended to wash them around 1-2 times a year.

There is no set time to wash your solar panels, but you may want to include the maintenance with other seasonal chores, such as cleaning the gutters or washing windows.  Clean solar panels will definitely improve your energy output and put more money in your pocket. Call Sun City Solar Energy and, for a nominal fee, we will be happy to wash your panels for you.

Would you like to live completely off the grid? The Harris’ have decided to do just that! Building a beautiful new home with Off-Grid Solar Power designed and installed by Sun City Solar Energy. The Harris’s will moved in at the end of August and are very excited to be energy independent. 

In Tulsa, one of our many repeat customers, Mr. Russell, has asked Sun City Solar to install his fifth installation with our team. Starting last November with a solar power system with battery back up and Solar Hot Water, Mr. Russell has asked Sun City Solar to install another solar power system with battery back up and Solar Hot Water on another home.

Sun City recently designed and installed a solar lab for Oklahoma Gas and Electric so they can test several inverters.

Last week we finished a large Solar Hot Water system for Eureka Springs Transit Authority, a  Solar Power system for the City of Springdale, and a Solar Pool Heater for Eco Apartments.

Of course, we continue to install many residential grid tie systems and enjoy our customer’s smiles when they see their meter spin backwards!

Sunpower, an American company, sells the solar module with the highest efficiency of 19.6%.  Number three Sanyo  HIT technology combines a crystalline silicon cell with an additional amorphous silicon layer. The difference between the leader and the number 10 is 3.4%; Although a small difference, it could be relatively significant. The difference could mean you will use less space on your roof to achieve the same system power or energy yield. It also means you need less Balance Of System components such as mounting hardware. Does it  pay to use the higher efficient modules?

This ranking does not say anything about the module cost per Watt, nor about the most important concern, the cost per produced solar kWh. It could mean that a module of lower efficiency is so much cheaper that the extra cost for other system components (more frame, cables, installation work) can easily be covered by the money saved on the modules. Also, some modules perform better in real life conditions rather than in the standard test condition as mentioned on the their certified datasheet.

All but one of the  the top 10  modules are manufactured in Asia.  The number one, Sunpower, is from the US, but their cells and modules are manufactured in the Philipines.   Several well known brands did not make it into the Top-10 as most are  young and unknown brands.It will be interesting to see what market position these young companies obtain.   The future will tell as the top 10 listings  will continue to change.

Solar Power is quickly becoming competitive with new nuclear, new natural gas, and, soon, new coal. We are starting to realize grid parity in solar all with technologies available today.

It takes decades to install one nuclear power plant. Solar, a modular technology, can be produced and installed at a pace far faster than most energy technologies.

This year, the U.S. industry may install 2 gigawatts of solar. The last nuclear power plant to come online in the U.S., Watts Bar 1, has a capacity of 1.1 gigawatts — but that took 23 years to complete, not two years.

Natural gas peaker plants, which are idle most of the day are an expensive option for utilities.

Over the last few years, 153 coal plants have been abandoned, in large part due to uncertainty over environmental regulations.

So what does all this mean? It means that the notion that “solar is too expensive” doesn’t hold up anymore. When financing providers can offer a home or business owner solar electricity for less than the cost of their current services; when utilities start investing in solar themselves to reduce operating costs; and when the technology starts moving into the range of new nuclear and new coal, it’s impossible to ignore.

According to SunPower’s Tom Dinwoodie: “The cross-over has occurred.”

Tulsa Tech and Sun City Solar Teach On The Job Solar Electric to Students

The Tulsa Technology Center and Sun City Solar Energy have formed a work-based program for the Technology Center’s electrical students. Master Electrician Larry Batson from Tulsa Technology and Installation Manager Garret Roth of Sun City Solar Energy will teach students how to install solar electric systems on actual solar installation projects.  The program will allow students to work in a hands-on environment. Students will have the opportunity to learn solar electrical concepts for several different solar electric system applications.

The Solar Installation program will provide needed job skills for the students and serve as a resource for the growing solar energy industry. The students will be evaluated on a regular basis by Sun City Solar professionals to ensure compliance with industry standards.  The program was developed by Tulsa Technology and Sun City Solar Energy jointly.

For more information about this program, contact:

Garret Roth, Installation Manager, Sun City Solar Energy at 918-494-0886

Larry Batson, Master Electrician and teacher at Tulsa Technology Center 918-955-0047