550MegaWatt PV installation in California. NO offshore drilling catastrophes, oil tanker collisions, fracking, CO2 emissions, nuclear disasters, etc, etc etc. Just environmentally safe, clean, sustainable, CO2 offsetting sun energy collected for 50 years!
Interesting factcheck.org discussion regarding some misconceptions circulating on man-made versus volcanic eruptions CO2 emissions. According to USGS, human activities release at least a hundred times more CO2 every year than all the world’s volcanoes combined.
While it can appear a little daunting at first, a PV system can be broken down into easily understood building blocks as follows:
1) Several PV modules are strung together
2) whose output is accumulated in a combiner box
3) whose output is sent through a DC disconnection switch
4) which is then fed to an AC inverter (that converts the DC to house/grid compatible AC)
5) that is then fed to your house service box (which is already connected to the grid)
Typically, all of these building blocks have UL and NEC compliance and use UL and NEC compliant cables and connectors to bring it all together. Not so complicated, right?
The high cost of crystalline silicon wafers (they make up 40-50% of the cost of a finished module) has led the solar industry to look at cheaper materials to make solar cells from. Thin film technologies use significantly less silicon which reduces initial manufacturing costs. They also use a silicon deposition process that lends itself to very flexible construction which opens up uses in many consumer electronics applications, as well as, may offer particular design advantages for Building Integrated PV (BIPV) applications. Some people prefer the aesthetics of the black thin film modules to better match their black asphalt shingle roofs as well.
Thin film also has some significant disadvantages though. Since they use less silicon, they can produce as much as 50% less power output. That lesser output translates into more up front modules and hardware required and higher long term operating costs through more real estate and roof space required for the system. They have also shown some significant degradation of performance (15-35%) over time versus the crystalline cell modules which also contributes to higher long term operating costs.
With all that said, one of the largest commercial and utility scale module producers in the world, First Solar, uses CdTe thin film in their module designs. https://sunlution.wordpress.com/2012/09/11/top-10-solar-module-manufacturers/
There are several different companies offering methods for securing panels to your roof. While they do differ somewhat, they all have the important task of securely attaching the panels while providing a weather-tight seal for each roof penetration. The image below shows one companies approach (Quick Mount PV). They use an engineered combination of roof flashing, lag bolt and sealing approach that accomplishes a long term, highly reliable weather-tight connection to your roof. The installer simply locates your joists, lags into them and positions the flashing under your existing shingles. They then attach the aluminum rails that the solar panels are then secured to. It’s a fairly straight forward and well thought through approach. Make sure you have a south facing roof and don’t have any obstructions (ie. trees) while the sun is up. See ya on the sunny side…
Basic electrical theory says that a Watt = Volts (V) x Amps (I). Watts are also sometimes referred to as “power”. Knowing this allows you to correlate the power requirements for different things. The image below shows how many 200 watt solar panels you’d need to run a corresponding number of 100 watt incandescent light bulbs. In very rough terms, if these 5 solar panels collected 5 hours of energy from the sun in a given day (5KWh) you’d logically be able to run 10 100W (.83A @ 120V) incandescent light bulbs for 5 hours as well. Using more efficient equivalent 30W compact fluorescent light (CFL) bulbs could allow you to run 3 times as many light bulbs. The following NREL website provides examples of the power requirements for different household items. Using some of that data, you could extrapolate that these same 5 solar panels capturing 5 hours of sun a day (5KWh) might run your oven on bake for approximately 4 hrs a day or run an energy efficient refrigerator for 55 hours. You wouldn’t need to capture the energy because you’re feeding your power into the power companies’ grid and they give you the credit towards your power bill.
Some companies are mounting AC and DC electronics on the backs of the solar modules either within the junction boxes or other separate boxes (ie. micro-inverters, DC converters, etc). Some of the companies are Tigo, Esmolo, Enphase, Shoals, SolarEdge, Azuray, Westinghouse, Huber Suhner and many others. One of the primary reasons claimed for doing this is to improve the overall energy harvest of the module and system. Other possible reasons are listed below.
– Remote monitoring
– Remote shutdown and control
– Start up and shutdown ramp rate control
– Voltage control and boost (inverter matching)
– Arc fault interruption (fire protection)
– Maximum Power Point Tracking (energy harvest)
– Module theft protection
– Installation safety
– Remote troubleshooting
Opponents (ie. central inverters and combiners) to this module level “granularity” claim that these on-board module solutions add unnecessary cost, complexity and lesser reliability to system designs since, as they claim, the central solutions offer much of the same features at lesser complexity and cost. The debate continues…