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New Solar Cell Technologies
Aug22

New Solar Cell Technologies

Over the years, we have seen the standard monocrystalline and polycrystalline PV modules increase in wattage per square foot, but they are getting close to the maximum possible efficiency on these typical solar cells. But manufacturers aren’t giving up, there are a few new up and coming technologies that will continue the progress of PV efficiency. Split cell technology uses the same solar material but cuts the cells in half. The new smaller solar cells have the same voltage as the original size cells, but they have half the amps. Putting 2 of these cells together gives you the same wattage as a single standard cell, but that wattage is a higher voltage and lower amperage. Power loss on conductors like the busbars inside a PV module is caused by voltage drop which is amps multiplied by resistance. Less amps means less voltage drop which means less power loss on the internal conductors. Voltage drop also causes heat build up so lower amps means the PV module is operating at lower temperatures, further increasing the efficiency. Overall, using split cell technology can increase solar panel power output by 5 to 8 watts per module. This lower operating temperature also increases the expected life span of the module as excessive heat leads to degradation. N-type solar cells are not new, but they are gaining popularity in the industry which until recently has been dominated by the p-type solar cells. Solar cells are made by “doping” silicon with very small amounts of either Boron to make the silicon more positively charged (p-type) or Phosphorus to make the silicon more negatively charged (n-type). The p-type solar cells are cheaper to make, but the n-type cells are more efficient. Adding to this, the Boron in the p-type cells causes an undesirable effect called Light Induced Degradation (LID). LID happens in the first few days and weeks that the p-type cell is exposed to sunlight and it can reduce its efficiency by 2%-3%. The n-type cells do not experience LID, so not only do they start at a higher efficiency than p-type and they maintain that efficiency over time. Another advantage of n-type cells is they are not as sensitive to impurities in the silicon base so manufacturers of n-type cells can use lower quality silicon without impacting the efficiency. Currently n-type PV modules are still more expensive than p-type, but many people are willing to pay for the higher efficiency, so the n-type is gaining in market share. Back contact (or rear contact) solar cells are another innovation coming to the forefront. A typical PV cell is made in a way that requires...

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Why Go Solar Now?
Aug14

Why Go Solar Now?

You know solar is a good idea. You see the systems on your neighbors’ roofs and you may have even heard them brag about the savings on their electric bill. So why are you waiting? Now is the time to get your system installed. The cost of solar has been dropping each year, but this doesn’t mean you should wait for it to drop more. For one thing, the equipment costs are about as low as they can get. At this point more than half of the cost to install a system cost is labor and that is not getting any cheaper. You also need to think about the money lost while you wait. The overall cost of solar of a solar installation has dropped about 2% in the last year.  That means a $30,000 system is $600 less than it was last year. But that system will generate about $2,500 worth of electricity in a year. So, if you did not install last year, you lost $1,900 waiting for the price break. Don’t make that mistake again this year. Another reason to stop dragging your feet is that government incentives don’t last. If there is a state or local rebate you can get, take advantage of that now. Most rebate and SREC programs are designed to end when a certain number of megawatts of solar are installed. This means the sooner you get your application in, the more likely you are to get a piece of that pie. Even the federal tax credit is not forever. The current 30% amount is set to lower for systems installed after 12/31/19 before it ends completely in 2021. This means there is going to be a frenzy of installs next year as all the procrastinators get on board to get the full tax credit. Solar installers can only get so many installs done so it is best to call one now and beat the rush. If you are concerned because you don’t have a big tax liability this year, you should still get your solar installed now. Take what you can of the tax credit and the remainder can roll over to future years for as long as the tax credit is in effect. Also keep in mind, the tax credit matters even if you are planning to lease your system. When you go solar using a lease or PPA program, the lease or PPA company is taking that tax credit and factoring it into your cost, so it is still important to be mindful of the deadline on it. Some people put off solar because they are deciding about selling...

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Reading Your Electric Bill
Aug09

Reading Your Electric Bill

Over the years electric bills have gotten more complicated. It is important to understand how you are being charged for your electricity, especially if you are trying to calculate your payback on installing solar. There are still some electric companies that have an old school, simple approach to billing. They add up how many kilowatt hours (kwh) you have used that month and they bill you a set amount per kwh. If this is your electric company, congratulations! Your bill is easy to understand. But on a “tiered” or “TOU” billing system things get a little trickier. If you are on a “tiered” electric rate, you will see different dollar amounts per kwh which can get a little confusing. The concept behind this type of billing is that the electric company will charge you a reasonable amount for the first kwh that you use, but as you use more, they charge more. It starts with a baseline amount of electricity which is decided by the electric company. For example, they may say that the baseline is 20 kwh/day. They will charge “Tier 1” price for this baseline electricity, in our example, we will say it is $.15/kwh. Then the electric company will assign another amount of kwh which will be “Tier 2”, for example it could be another 30 kwh/day and those will be billed at the “Tier 2” price of $.25/kwh. Anything above that would be considered “Tier 3” pricing which could be as high at $.35/kwh. Sometimes there will be even more tiers than that but we will work with just three for this example. So let’s say it is summer time and on day one of the month, you weren’t home so you set the air conditioning to 80 and you only used 45 kwh. On day two, you were home and it was hot out so your air conditioning was on full blast and you used 65 kwh. Day three was cooler so you only used 55 kwh. What would the electric company charge you on the tiered system for these three days? Tier 1            Tier 2            Tier 3             Total Day one:    (20 x $.15) + (25 x $.25)                         =  $9.25 Day two:    (20 x $.15) + (30 x $.25) + (15 x $.35) = $15.75 Day three: (20 x $.15) + (30 x $.25) + ( 5 x $.35)   = $12.25 Now, if you were one of the lucky people who has solar, how much do you save in a tiered billing system? The answer is a lot because the solar helps keep you out of the higher pricing tiers. Let’s look at this...

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How Many Solar Panels Do I Need to Charge my EV?
Aug03

How Many Solar Panels Do I Need to Charge my EV?

We are still miles away from being able to produce a practical, self-contained solar powered car but that does not mean you have to give up your dream of driving on sunshine. If you have an electric vehicle, you are halfway there. All you would need to add is some solar panels to your home charging station. Before we get into system sizing, many people have the idea that the solar electric vehicle charging station must be a stand-alone system, but that is not the best configuration. If the solar panels are only connected to the EV charger and you don’t drive anywhere that day, the solar power is wasted. The way to avoid that is to install a standard grid-tied system or a system with a SolarEdge grid-tied inverter with an integrated EV charger. With either of these options, the solar power produced when you don’t need to charge your car will be used to run other loads in your house or backfeed to the grid so it would never be wasted. So how many solar panels do you need to charge your EV? That depends on how much you drive. The average EV uses about .3 kwh per mile. This means if you average 50 miles per day, you would use about 15 kwh per day to keep it charged. With solar, it always best to talk about annual production because solar panels will always produce more energy in the long summer days than they will during the winter months. So let’s look at the annual usage for the car which is just the daily number multiplied by 365 days. In our example above, 15 kwh multiplied by 365 days is 5,475 kwh. That is the amount your solar would need to generate to off set the electricity used by the car annually. We have discussed system sizing in previous articles, but to give a short summary, you can start with PV Watts at https://pvwatts.nrel.gov/. Follow the prompts which start with entering your zip code so your production numbers will be location specific. It will also ask for a system size in kilowatts (kw). A good starting point is to take that kwh number you want to reach and divide it by 1,500. In our example above where you wanted to generate 5,475 kwh it would be 5,475/1,500 = 3.65 kw. Once you see the output on that system size, you can adjust the size up or down to get to the goal. You will also need to enter the tilt and Azimuth of the system. Tilt is just the angle from horizontal. If the system will...

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How Many Solar Panels Do I Need?
Jul25

How Many Solar Panels Do I Need?

Once you have chosen to go solar, the very important question arises. How many solar panels do I need? The first part of this is to figure out how many Watts of solar you need. This will depend on how much energy you want to generate. If you are shopping for a grid-tied system, you will find the answer in your electric bills. Every month, the electric company has tallied exactly how much energy (kiloWatt hours or kWh) you used so they could bill you for it. The meaning of that kWh figure and kW is commonly confused. The kWh is merely kW over time. For example: if 10 kW is consumed for 2 hours, that is 20 kWh. An analogy is kW is like a speedometer, indicating how much power is being consumed at one point in time. And kWh is like an odometer, indicating how much power has been consumed over time. All you have to do is look at the history of kWh usage on your paper electric bills or your online account with the power company. We recommend reviewing at least 12 months of electric history. You will definitely notice a difference in usage from winter to summer and basing your needs on just one month’s bill can be a big...

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