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Solar PV (photovoltaic) cells convert the sun’s energy into electricity. They rely on the the photoelectric effect: the ability of matter to emit electrons when a light is shone on it.
Sunlight is composed of miniscule particles called photons, which radiate from the sun. As these hit the silicon atoms of the solar cell, they transfer their energy to loose electrons, knocking them clean off the atoms.
Freeing up electrons is however only half the work of a solar cell: it then needs to herd these stray electrons into an electric current. This involves creating an electrical imbalance within the cell, which acts a bit like a slope down which the electrons will flow in the same direction.
Silicon atoms are arranged together in a tightly bound structure. By squeezing small quantities of other elements into this structure, two different types of silicon are created: n-type, which has spare electrons, and p-type, which is missing electrons, leaving ‘holes’ in their place.
When these two materials are placed side by side inside a solar cell, the n-type silicon’s spare electrons jump over to fill the gaps in the p-type silicon. This means that the n-type silicon becomes positively charged, and the p-type silicon is negatively charged, creating an electric field across the cell. Because silicon is a semi-conductor, it can act like an insulator, maintaining this imbalance.
As the photons smash the electrons off the silicon atoms, this field drives them along in an orderly manner, providing the electric current to power calculators, satellites and everything in between.
Net metering allows consumers who generate some or all of their own electricity to use that electricity anytime, instead of when it is generated.
1. Solar Panels- Solar panels are mounted on a roof or a freestanding mount to make up a solar array. These solar panels are made up of photovoltaic cells (PV), which convert the suns rays into direct current power (DC). The size of the array depends on the amount of power to be produced.
2. Inverter- The DC power from the solar array is sent to an inverter, where it is converted into alternating current power (AC), the same as household electrical current in your home.
3. Electrical Panel- The AC power flows through the homes existing electrical panel and is used just like power flowing from the utility grid.
4. Utility Meter- The home utility meter is changed to a "two way" meter so when the solar array produces more power than the home is using, the meter spins backwards and accumulates credits with the utility company to be used at a later date. This concept is called net-metering and is the most cost efficient method used to solar production.
5. Utility Grid- The home continues to be connected to the utility grid to supply power when the solar array is not producing. Also, the utility becomes the home's battery, storing power in the form of credits to be used during not sunlight hours.
Video Series #2
Properly sizing a grid tied solar system requires a few pieces of information.
1. Your electricity consumption. It is important to get an annual consumption statement from your utility company. This will give you the total number of kw/h (kilowatt hours) of energy you consume.
2. Your solar energy yield based on your geographical location. This number is expressed in kw/h per kW of installed solar PV. Alberta, Manitoba and Saskatchewan locations range between 1000-1400 depending on the location. miEnergy utilizes state of the art satellite software to pinpoint your location to accurately estimate your system size.
3. Now take your consummation (kw/h) and divide by the solar energy yield to get the size solar system required to offset the energy load.
Ex. Total yearly energy consumption = 6500 kw/h
Location in Regina SK with solar energy yield = 1400 kw/h per kW
6500/1400 = 4.7kW Solar System
Depending on the power class (wattage of each module) determines the number of modules and the installed system size.
Ex. Assuming 270watt modules, 18 modules would be used to total 4.8kW total system size.
** System design is much more complex then the above example. Other considerations such as string lengths, voltage drops, size restraints, and temperature play a large part in accurate design. Contact us to walk you through the process.
Since solar panels work with light, not heat, it doesn’t matter how cold it gets outside. In fact, solar panels perform better in cooler temperatures than very hot temperatures.
Since it’s so cloudy in the winter, will my solar panels produce any electricity at all?
Yes. Even when it’s cloudy outside, your solar panels will still produce electricity. As long as there is light, your system will convert it into energy. Since the days are shorter, you won’t produce energy for as long as you would during long summer days.
What about snow?
miEnergy will design and install your system in the best position to get the maximum amount of sunlight possible; ideally, your system will be facing the south. Since the panels are smooth, snow doesn’t stick to them like it would to rough roof shingles, so it typically melts or slides away quickly and easily on its own. If any potion of the panel is exposed to the sun, it will generate heat and melt the snow away. There are times that the snow may pile up during blizzards. If you need to remove the snow from your roof because you’re concerned about the weight and how long it will take to melt, we highly recommend using a snow rake with extreme caution. A study conducted by NAIT in Edmonton Alberta concluded that a system with no snow removed throughout the winter will reduce production be less than 5 percent.
Stand-alone inverters, used in isolated systems where the inverter draws its DC energy from batteries charged by photovoltaic arrays. Many stand-alone inverters also incorporate integral battery chargers to replenish the battery from an AC source, when available. Normally these do not interface in any way with the utility grid, and as such, are not required to have anti-islanding protection.
Grid-tie inverters, which match phase with a utility-supplied sine wave. Grid-tie inverters are designed to shut down automatically upon loss of utility supply, for safety reasons. They do not provide backup power during utility outages.
How does solar work?
What is Net Metering?
Does it work in the winter?
What is an inverter?
There are 3 types of technology utilized in the solar panels available on the market today, these are monocrystalline, polycrystalline, and thin film amorphous.
This is the oldest and most developed of the three technologies. Monocrystalline panels as the name suggests are created from a single continuous crystal structure. A Monocrystalline panel can be identified from the solar cells which all appear as a single flat color. They are made through the Czochralski method where a silicon crystal ‘seed’ is placed in a vat of molten silicon. The seed is then slowly drawn up with the molten silicon forming a solid crystal structure around the seed known as an ingot. The ingot of solid crystal silicon that is formed is then finely sliced ingot what is known as a silicon wafer. This is then made into a cell.
Polycrystalline or Multicrystalline are a newer technology and vary in the manufacturing process. Polycrystalline also start as a silicon crystal ‘seed’ placed in a vat of molten silicon. However, rather than draw the silicon crystal seed up as with Monocrystalline the vat of silicon is simply allowed to cool. This is what forms the distinctive edges and grains in the solar cell. Polycrystalline cells were previously thought to be inferior to Monocrystalline because they were slightly less efficient, however, because of the cheaper method by which they can be produced coupled with only slightly lower efficiencies they have become the dominant technology on the residential solar panels market.
Polycrystalline are now very close to Monocrystalline cells in terms of efficiency.
Thin film panels are a totally different technology to Mono and Polycrystalline panels. They are a new technology compared to Mono and Polycrystalline cells and would not be considered a mature technology as vast improvements in this technology are expected in the next 10 years. A thin film panel can be identified as having a solid black appearance. They may or may not have a frame, if the panel has no frame it is a thin film panel. Thin film panels are made by depositing a photovoltaic substance onto a solid surface like glass. The photovoltaic substance that is used varies and multiple combinations of substances have successfully and commercially been used. Thin film cells have got a reputation as being the ‘worst’ of the solar panel technologies because they have the lowest efficiency. However, this is only because they have a lower power efficiency which only means they require the most space for the same amount of power.
The solar array can be mounted on rooftops, generally with a few inches gap and parallel to the surface of the roof. The panels can be mounted on rails or with a rail-less mounting package. If the rooftop is flat, the array is mounted with each panel aligned at an angle. The location of the solar array determines the appropriate angle.
When sufficient land is available, the solar array can be mounted on a free standing racking structure. This structure should be build out of aluminum and is anchored to the ground with piles. The pile are typically screw, pounded beams or ballasted concrete.
Inverters convert the DC electricity from the solar panels into AC electricity. The three main inverter options are string inverters, micro-inverters, and power optimizers.
Power optimizers offer many of the same benefits as micro-inverters. Like micro-inverters, power optimizers are located at each panel, usually integrated into the panels themselves. However, instead of converting the DC electricity to AC electricity at the panel site, they “condition” the DC electricity and send it to a string inverter. This approach results in higher system efficiency than a string inverter alone. Similar to micro-inverters, power optimizers reduce the impact of panel shading on system performance, and also offer panel performance monitoring.
String inverters are the most cost-effective inverter option if the roof is not shaded at any point during the day and does not face in multiple directions
The solar panels are arranged into groups connected by “strings.” Each string of panels is connected to a single inverter, which transforms the DC electricity produced by the panels into AC electricity. String inverter technology has been used for decades. It is a tried-and-true technology, but is not suitable for certain types of installations. A string of solar panels will only produce as much electricity as its least productive panel – if one or more of the solar panels is shaded during any part of the day, the power output from that entire string would be reduced to its level. For this reason, if the solar panels are installed facing different directions, a string inverter may not be a good choice. One of the most common reasons for a panel to produce less power or stop producing power altogether is shading from nearby objects. If the roof is prone to shading any time during the day or in certain seasons, either remove the source of the shade or install the panels where they will not be shaded.
Micro-inverters are installed on each individual panel in a solar energy system. They convert the DC electricity from the solar panels into AC electricity on the roof, with no need for a separate central inverter. In many cases the micro-inverters are integrated into the solar panel itself, but they may also be mounted next to the panel on the mounting system. One of the major advantages of micro-inverters is that they cancel out the negative impacts of partial or complete shading. The DC-AC electricity conversion takes place at each panel, there is no “bottleneck” when one panel’s production decreases.
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