Solar Electric systems are usually classified into three types: Grid-Tied, Off-Grid, and Grid-Tied Battery Back-up. Mission Solar Electric has installed all three types of system.
Grid-Tied Systems are the majority of the installations in the USA. They are designed to offset your electricity bill. During the day, when your system is producing excess electricity beyond the needs of the residence or building, the electricity will flow back onto the Grid spinning your electrical meter backwards, thereby gaining credits. At night, the electricity flows from the Grid to your residence or building, spinning your meter forwards. The systems operate seamlessly. Electrical Power flows back and forth from/to the Grid. Usually you are billed for the Net amount that your Meter goes forward, if any, during a annual cycle. Grid-Tied systems are efficient, reliable, proven, and require little maintenance. Because California’s electricity rates are high, the economics are solid and the system will usually pay for themselves many times over during the life of a system. The only drawback is the systems do not provide Emergency Power Backup. If the electrical Grid fails, the systems will turn-off. If you want Emergency Power Backup, you will need to purchase a Grid-Tied Battery Backup system.
Off-Grid Systems are for supplying electricity where there is no Grid connection such as a remote residence or cabin but can also apply to systems on boats or RVs. The heart of Off-Grid systems is the Battery Bank. The Solar Modules charge the Batteries through a Charge Controller. These systems tend to be expensive, more complex, and require more maintenance. Usually they require a back-up Generator so the batteries can be charged if the weather is bad for a extended period of time. The key to Off-Grid systems is energy efficiency. The more electrical power used, the larger the battery bank and Solar Array will need to be. The costs escalate quickly.
Grid-Tied Battery Back-up Systems usually operate as normal Grid-Tied systems but in the event of a Grid failure, have some Emergency Power Backup capability. These systems require Battery Banks which makes them more expensive and more complex. Unless are in an area with frequent Grid outages, it is difficult to justify the cost. Usually, you would be better off with a standby Generator. This may change in the future as more products become available and the cost of Batteries decrease.
Solar Electric Modules, technically called Photovoltaic Modules, or PV Modules for short, are the heart of any Solar Electric system and convert the sunlight to electricity. They are often called Solar Panels but because that term also refers to Panels that heat water from sunlight, the Solar Electric industry uses the term “Modules” instead of “Panels”. For the remainder of this section we will use the term Solar Modules.
Solar Modules are modular so by adding additional Modules to a system you can build a system to any size from around 10 Solar Modules for a small residential system to thousands of Solar Modules for a Utility scale Solar Electric plant. The complete system comprised of many Solar Modules is referred to as the Solar Array. Solar Modules come in different sizes that usually correspond to different power outputs. For example, a 240 Watt Solar Module is usually physically bigger than a 200 Watt Solar Module.
There is a global oversupply of Solar Modules right now which is good for consumers and installers. This was not always the case. From 2004 through 2007 there was a global shortage. Although it appears there are many quality products on the market, the preferred Solar Modules of Mission Solar Electric are from Kyocera Solar, Inc. Although there are many choices for the consumer, consider the following about Kyocera Solar Modules:
* Kyocera has been a leader in Solar Electric for over 35 years. They have been mass producing Solar Modules for 31 years, having produced over 7 Million modules. Very few other companies have been in Solar Electric as long as the power output warranty of their Solar Modules, which is typically 25 years.
* Kyocera Solar, Inc is part of the Kyocera Group which is made up of 212 companies with annual revenues over $10 Billion. The Kyocera Group has been profitable every year of operation and has a strong balance sheet (Cash $2.7 Billion in 2010). No other solar company has such strength.
* Kyocera has a strong local presence in the greater San Diego community. Kyocera America is headquartered in Kearny Mesa. The Solar Modules are assembled in both Tijuana, Mexico and at their facility in Kearny Mesa. They were a large contributor to the Rebuild a Greener San Diego program after the 2003 Cedar Fires, selling the Solar Electric equipment at wholesale prices so that residents rebuilding their residences could afford Solar Electric systems.
* Kyocera Solar, Inc. is vertically integrated and manufacture the solar cells and assemble their modules. Indeed, they have complete control of every step of the manufacturing process. This results in a high quality, efficient Solar Module that gives excellent long term results.
If you are installing a Solar Electric system, which is a long term investment, you want to make sure the installed Solar Modules are top quality and from a Manufacturer who will be around to honor the warranty. See www.kyocerasolar.com for more info.
Inverters and Micro-inverters:
The other key component of a Solar Electric system is the Inverter which converts the DC electrical power from the Solar Module to AC electrical power used by the residence/building or to back feed the electrical power grid. Traditionally, multiple Solar Modules are wired together in series/parallel and then the combined output is routed to a Inverter which does the DC to AC conversion. Inverters typically range in size from 1.5 kW which can handle less than 10 Solar Modules to commercial scale Inverters that can be as large as 1 MW which can handle thousands of Solar Modules. Some sites, especially residential, may have multiple Inverters.
Within the last few years, Micro-Inverters have become popular. Micro-Inverters are small Grid-Tied Inverters but are small so they can handle only a single Solar Module, hence the “Micro” prefix. Having a Micro-Inverter for each Solar Module has many advantages over an Inverter that has multiple Solar Modules connected primarily related to flexibility of design and the ability to monitor the output of every Solar Module.
Mission Solar Electric has installed both Inverter systems and Micro-Inverters. Although it appears there are many quality products on the market, Mission Solar Electric has used the following Inverter manufacturers below many times with success and would most likely specify one of them for your Installation.
The world leader in Grid-tied Inverters and a German manufacturer renowned for quality and reliability, their “Sunny Boy” Inverter line has been extremely successful and is probably the most time tested Inverter line. SMA is probably the safest choice for any Solar Electric installation. See the photo below of a dual Inverter system. The box between the Inverters is the SMA WebBox which allows Internet data logging and monitoring of the system. See www.sma-america.com for more info.
The world leader in Micro-Inverters. Initially, Mission Solar Electric took a wait-and-see approach to Micro-Inverters, recognizing their obvious advantages but worried about the reliability, especially long term. Since the Micro-Inverter is installed underneath the Solar Module with elevated roof temperatures, the reliability concerns seemed logical. However, the Enphase Micro-Inverters have proven to be very reliable so far. The latest generation product, the M215 comes with a 25 year manufacturer warranty which would seem to indicate incredible confidence in the long term reliability of the product by the manufacturer. The Internet monitoring is incredible, allowing you to see the production of every Micro-Inverter at any time of day. The advantages of Micro-Inverters can be summarized as follows:
(1) No single point of failure. All micro-inverters are independent and in parallel so the failure of one does not affect the others.
(2) 25 year warranty on micro-inverters (normal Inverters have standard 10 year warranty).
(3) Free Module level Internet monitoring which functions as QA on the Solar Modules.
(4) Better shade tolerance.
(5) Safe (no high voltage DC).
(6) No space need for Inverter.
(7) Flexibility (different orientations, roof faces, etc.) on Solar Module installation
See photo below that shows the Enphase Micro-Inverters attached to racking system, one under each Micro-Inverter. See www.enphase.com for more info.
Another German manufacturer known for quality and reliability, Kaco has been manufacturing Inverters for 60 years. Mission Solar Electric has used their Inverters when the SMA Inverters have not been a good fit and they
have proven to be reliable and given good results. Kaco has 100% CO2 neutral manufacturing. See www.kaconewenergy.com/ for more info.
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