Post by AD5DO on Sept 26, 2013 10:23:50 GMT -6
Solar power is not cheep! But you can construct a dependable backup power source. The first thing you need to do is decide how much power you want to store and how fast you want it to recharge. This will help you plan your system and control cost. Every piece of the system has a max power rating. If you decide to upgrade your system later you will have to purchase some of your existing components again if you started too small. For example: If you start with a 5 amp solar cell system and wish to upgrade to a 15 amp system, you will need a charge controller that will handle 15 amps. Your 5 amp charge controller will not work with the new system.
Plan the location of your solar cell in respect to maximum hours of sunlight. You should strive to have a location without shade from trees and buildings. Even the smallest amount of shade can reduce the cells energy output tremendously. Covering only 10% of the cells can reduce power output by 80%. The power loss is not linear (sorry not my rules) with the percent of shade. Even the shade from overhead power lines will have an impact on power output. Once you have decided on your location you will have to select which type and size of solar cells you want. There are differences between the various types of panel, that are worth knowing about but, in the end, it is the total overall power that makes the biggest difference. The two most common types of solar cells are monocrystalline and polycrystalline. They are very close in price so the only real difference is the fact that polycrystalline will produce a little more power on cloudy days due to the cut of the crystal, allowing light from more angles.
The solar cells in monocrystalline panels are slices cut from pure drawn crystalline silicon bars. The entire cell is aligned in one direction, which means that when the sun is shining brightly on them at the correct angle, they are extremely efficient. So, these panels work best in bright sunshine with the sun shining directly on them. They have a uniform blacker color because they are absorbing most of the light. Polycrystalline panels are made up from the silicon off cuts, molded to form blocks and create a cell made up of several bits of pure crystal. Because the individual crystals are not necessarily all perfectly aligned together and there are losses at the joints between them, they are not quite as efficient. However, this mis-alignment can help in some circumstances, because the cells work better from light at all angles, in low light, etc. For this reason, I would argue that polycrystalline is slightly better suited to winters duller conditions, but the difference is marginal.
Charge controllers are regulators; which determines the rate at which electric currents are added to drawn electric batteries. Basically this just means that the charge controller determines how much power the battery receives so that no electricity is lost or wasted. By controlling the charge that the batteries receive the product then becomes much safer from users. It also ensures that the battery sees a long life span and provides sufficient power to the user. Each battery has a voltage level they can sustain before causing the battery to suffer damage or die. Most charge controllers stop the charge completely when they see the battery coming very close to approaching the level at which it might sustain damage. MPPT charge controllers adjust the charging rate of the battery allowing the battery to charge at its maximum capacity without going over.
Your charge controller must be sized to meet the amp output from the solar panels. If you have a maximum of 15 amps delivered from the panels you will need a 15amp charge controller. You will also need to get a charge controller for the proper voltage. Will you need a 12v or 24v? More on this later.
The battery storage system is just as expensive as the solar panels themselves. There are several considerations which need to be addressed. Where do you plan on storing your battery bank? Conventional wisdom dictates the batteries should be as close as feasible to the solar panel and charge controller. DC current requires a substantially larger wire to move current than that of AC currents and the longer the run the higher the resistance and the higher the resistance the greater the loss through heat. House the batteries near the solar panels and protect them from the weather. What type of battery do I need? This is the question I hear the most. The standard car battery is a very poor choice. This type of battery is for rapid amp draw and not a good battery for deep discharge. With today’s battery prices you can get a marine deep cycle battery for a little more than a car battery. Batteries for golf carts are a good choice as well as gel cell batteries for scooters or wheel chairs. Be aware that the gel cell battery requires a different type of charger.
The solar inverter may seem insignificant, but it is most often the choke point of a photovoltaic installation. Many people fall into the trap of underestimating the system's needs for a solar inverter and purchase one that handles a smaller capacity than necessary in an attempt to save money. This is a mistake that can be costly in the long run. A better way to cut costs is to purchase an inverter with much more capacity than you plan to initially install and add more panels to boost production later on down the line. This leaves your system with room to grow. Its purpose is to change the direct current (DC) electricity that is generated from a photovoltaic panel into an alternating current (AC). Prices vary depending on watt capacity and sine wave. Once power leaves the inverter you will need a power panel to handle the ac voltage.
Now that I have given a thumbnail sketch of a solar design lets open the forum to Questions and share ideas.
AD5DO
Plan the location of your solar cell in respect to maximum hours of sunlight. You should strive to have a location without shade from trees and buildings. Even the smallest amount of shade can reduce the cells energy output tremendously. Covering only 10% of the cells can reduce power output by 80%. The power loss is not linear (sorry not my rules) with the percent of shade. Even the shade from overhead power lines will have an impact on power output. Once you have decided on your location you will have to select which type and size of solar cells you want. There are differences between the various types of panel, that are worth knowing about but, in the end, it is the total overall power that makes the biggest difference. The two most common types of solar cells are monocrystalline and polycrystalline. They are very close in price so the only real difference is the fact that polycrystalline will produce a little more power on cloudy days due to the cut of the crystal, allowing light from more angles.
The solar cells in monocrystalline panels are slices cut from pure drawn crystalline silicon bars. The entire cell is aligned in one direction, which means that when the sun is shining brightly on them at the correct angle, they are extremely efficient. So, these panels work best in bright sunshine with the sun shining directly on them. They have a uniform blacker color because they are absorbing most of the light. Polycrystalline panels are made up from the silicon off cuts, molded to form blocks and create a cell made up of several bits of pure crystal. Because the individual crystals are not necessarily all perfectly aligned together and there are losses at the joints between them, they are not quite as efficient. However, this mis-alignment can help in some circumstances, because the cells work better from light at all angles, in low light, etc. For this reason, I would argue that polycrystalline is slightly better suited to winters duller conditions, but the difference is marginal.
Charge controllers are regulators; which determines the rate at which electric currents are added to drawn electric batteries. Basically this just means that the charge controller determines how much power the battery receives so that no electricity is lost or wasted. By controlling the charge that the batteries receive the product then becomes much safer from users. It also ensures that the battery sees a long life span and provides sufficient power to the user. Each battery has a voltage level they can sustain before causing the battery to suffer damage or die. Most charge controllers stop the charge completely when they see the battery coming very close to approaching the level at which it might sustain damage. MPPT charge controllers adjust the charging rate of the battery allowing the battery to charge at its maximum capacity without going over.
Your charge controller must be sized to meet the amp output from the solar panels. If you have a maximum of 15 amps delivered from the panels you will need a 15amp charge controller. You will also need to get a charge controller for the proper voltage. Will you need a 12v or 24v? More on this later.
The battery storage system is just as expensive as the solar panels themselves. There are several considerations which need to be addressed. Where do you plan on storing your battery bank? Conventional wisdom dictates the batteries should be as close as feasible to the solar panel and charge controller. DC current requires a substantially larger wire to move current than that of AC currents and the longer the run the higher the resistance and the higher the resistance the greater the loss through heat. House the batteries near the solar panels and protect them from the weather. What type of battery do I need? This is the question I hear the most. The standard car battery is a very poor choice. This type of battery is for rapid amp draw and not a good battery for deep discharge. With today’s battery prices you can get a marine deep cycle battery for a little more than a car battery. Batteries for golf carts are a good choice as well as gel cell batteries for scooters or wheel chairs. Be aware that the gel cell battery requires a different type of charger.
The solar inverter may seem insignificant, but it is most often the choke point of a photovoltaic installation. Many people fall into the trap of underestimating the system's needs for a solar inverter and purchase one that handles a smaller capacity than necessary in an attempt to save money. This is a mistake that can be costly in the long run. A better way to cut costs is to purchase an inverter with much more capacity than you plan to initially install and add more panels to boost production later on down the line. This leaves your system with room to grow. Its purpose is to change the direct current (DC) electricity that is generated from a photovoltaic panel into an alternating current (AC). Prices vary depending on watt capacity and sine wave. Once power leaves the inverter you will need a power panel to handle the ac voltage.
Now that I have given a thumbnail sketch of a solar design lets open the forum to Questions and share ideas.
AD5DO