Solar Power for the Do-It-Yourselfer
The solar cell was developed in 1953 at Bell Laboratories (now AT&T labs). In 1956, electricity from a solar cell cost about $300 per watt. Today that cost has fallen to $5 per watt and continues to fall as new technologies are discovered. Increasing use of solar power is also creating economies of scale.
Solar power has long been used in the Space Program. It is also used to power communication and industrial devices in remote locations. Even in the suburbs, it is common to see solar powered school-zone-warning lights because it is more economical instead of running power lines to the lights.
We have had solar powered watches and calculators for a number of years and now see that solar power residential outdoor lighting is common.
With today's energy costs solar power is becoming extremely popular. The industry has an annual growth of over 30%. While it costs 10's of thousands of dollars for a commercially installed system to power a complete residence, much can be saved by starting small and doing it yourself. Even the smallest system will contribute to a smaller electric bill.
Solar power systems can be classified as on grid and off grid. On-grid systems are connected to the local power line and supply power only while the solar panels are producing electricity. Off-grid systems are not connected to a utility power provider and include a battery bank for energy storage so that energy may be supplied when the sun is not available. There are also hybrid systems which are attached to the power lines and also have battery storage.
The various components of a DIY Solar Power system are discussed below.
Solar power has long been used in the Space Program. It is also used to power communication and industrial devices in remote locations. Even in the suburbs, it is common to see solar powered school-zone-warning lights because it is more economical instead of running power lines to the lights.
We have had solar powered watches and calculators for a number of years and now see that solar power residential outdoor lighting is common.
With today's energy costs solar power is becoming extremely popular. The industry has an annual growth of over 30%. While it costs 10's of thousands of dollars for a commercially installed system to power a complete residence, much can be saved by starting small and doing it yourself. Even the smallest system will contribute to a smaller electric bill.
Solar power systems can be classified as on grid and off grid. On-grid systems are connected to the local power line and supply power only while the solar panels are producing electricity. Off-grid systems are not connected to a utility power provider and include a battery bank for energy storage so that energy may be supplied when the sun is not available. There are also hybrid systems which are attached to the power lines and also have battery storage.
The various components of a DIY Solar Power system are discussed below.
Solar Power Panel
Converting the sun's rays into electricity
The main component of a DIY solar power system is the solar panel. Each panel is made up of many individual photovoltaic (PV) cells.
A PV cell is small device that converts sunlight into electricity through the photovoltaic effect. These cells are also called solar cells. There are several different types of PV cells with the silicon wafer - based type being the most popular.
Since the individual cells only produce a relatively small amount of electrical power, they must be connected with other cells to obtain practical power levels. For example, if a PV cell was rated at 1 watt it would take 120 of them to create a 120 watt solar panel.
The solar cells are mechanically mounted on a sturdy substrate and then are wired together as stated above to obtain the amount of power required. The substrate is mounted within a frame which has a weather-tight cover of glass or Plexiglas.
Multiple solar panels are then attached to a mount to form a solar panel array. The array may be attached to a roof top, a pole or even placed on the ground. The array's location must be in a place that receives the most direct sun light with a minimum of shade.
A PV cell is small device that converts sunlight into electricity through the photovoltaic effect. These cells are also called solar cells. There are several different types of PV cells with the silicon wafer - based type being the most popular.
Since the individual cells only produce a relatively small amount of electrical power, they must be connected with other cells to obtain practical power levels. For example, if a PV cell was rated at 1 watt it would take 120 of them to create a 120 watt solar panel.
The solar cells are mechanically mounted on a sturdy substrate and then are wired together as stated above to obtain the amount of power required. The substrate is mounted within a frame which has a weather-tight cover of glass or Plexiglas.
Multiple solar panels are then attached to a mount to form a solar panel array. The array may be attached to a roof top, a pole or even placed on the ground. The array's location must be in a place that receives the most direct sun light with a minimum of shade.
Solar Power Battery
Batteries store excess energy from the solar panels to be used at night or when sunlight is not available. Batteries are electrochemical devices. Their performance is a function of climate, temperature, charge/discharge cycle history and age.
Although there are different battery technologies, lead-acid batteries offer the best performance per dollar and are the most commonly used type in solar power systems.
A battery's capacity is listed in amp-hours at a particular voltage. So a 100 amp-hour, 12 volt battery would provide 12 volts at 1 amp for 100 hours.
The power of an electrical appliance is rated in watts, a measure of energy consumption per unit of time. One watt delivered for one hour equals one watt-hour.
To convert a battery's amp-hour capacity to watt-hours, multiply the amp-hours times the voltage. The product is watt-hours.
To calculate the required battery capacity to run an appliance for a given time, multiply the appliance power in watts by the desired number of hours of operation to get the total watt-hours. Then divide by the battery voltage to get the amp-hours. For example, to determine the capacity of a 12-volt battery to power a 60-watt light bulb for one hour divide 60 watt-hours by 12 volts to get 5 amp-hours.
A battery bank should be sized to be able to store power for 5 days of operation without any sunlight.
The battery type should also be a 'deep-cycle' type. That means that the battery is capable of having most of its capacity discharged before being recharged. An automobile battery is a 'shallow-cycle' type and is therefore not good for solar power applications.
Although there are different battery technologies, lead-acid batteries offer the best performance per dollar and are the most commonly used type in solar power systems.
A battery's capacity is listed in amp-hours at a particular voltage. So a 100 amp-hour, 12 volt battery would provide 12 volts at 1 amp for 100 hours.
The power of an electrical appliance is rated in watts, a measure of energy consumption per unit of time. One watt delivered for one hour equals one watt-hour.
To convert a battery's amp-hour capacity to watt-hours, multiply the amp-hours times the voltage. The product is watt-hours.
To calculate the required battery capacity to run an appliance for a given time, multiply the appliance power in watts by the desired number of hours of operation to get the total watt-hours. Then divide by the battery voltage to get the amp-hours. For example, to determine the capacity of a 12-volt battery to power a 60-watt light bulb for one hour divide 60 watt-hours by 12 volts to get 5 amp-hours.
A battery bank should be sized to be able to store power for 5 days of operation without any sunlight.
The battery type should also be a 'deep-cycle' type. That means that the battery is capable of having most of its capacity discharged before being recharged. An automobile battery is a 'shallow-cycle' type and is therefore not good for solar power applications.
Solar Power Charge Controller
To prolong the life of the battery bank, a controller is normally required. The primary function of a controller is to prevent the battery from over charging, which significantly reduces battery life expectancy. A controller monitors the battery voltage and reduces or stops the charging current as the voltage increases. When the battery voltage drops the controller will allow the current to increase to charge the battery.
Controllers are rated by how much current they can handle. Exceeding the amperage ratings of a controller can destroy it. Controllers are designed to handle a 25% over current for short periods of time.
It is a good idea to initially install a larger capacity controller if you plan on future expansion of your system. A larger controller usually doesn't cost that much more.
Controllers are rated by how much current they can handle. Exceeding the amperage ratings of a controller can destroy it. Controllers are designed to handle a 25% over current for short periods of time.
It is a good idea to initially install a larger capacity controller if you plan on future expansion of your system. A larger controller usually doesn't cost that much more.
Solar Power Inverter
The battery bank stores direct current (DC) power from the solar panels. This is usually 12, 24 or 36 volts. In cases where the system you want to power is a DC system, such as a recreational vehicle (RV) or other DC appliances, then an inverter is not even required. But typical household appliances use alternating current (AC) power.
An inverter converts low DC voltage from the batteries into a higher AC voltage, such as 120 or 240 volts that can power the appliances.
The inverter also establishes the AC frequency which is 60 Hertz (cycles-per-second) for the USA. It also provides a sinusoidal (sine) shaped waveform which is required for most electronic appliances. Some inverters approximate a sine wave which results in lower cost and are fine for many applications. The best inverters offer a true sine wave and typically supply better quality power than the utility power company.
The inverter needs to be sized to handle the required system power. Brand-name inverters are very reliable and have conversion efficiencies of around 90%. Make sure the inverter has a California Energy Commission (CEC) certification. Stay away from cheap imported inverters without CEC certification.
An inverter converts low DC voltage from the batteries into a higher AC voltage, such as 120 or 240 volts that can power the appliances.
The inverter also establishes the AC frequency which is 60 Hertz (cycles-per-second) for the USA. It also provides a sinusoidal (sine) shaped waveform which is required for most electronic appliances. Some inverters approximate a sine wave which results in lower cost and are fine for many applications. The best inverters offer a true sine wave and typically supply better quality power than the utility power company.
The inverter needs to be sized to handle the required system power. Brand-name inverters are very reliable and have conversion efficiencies of around 90%. Make sure the inverter has a California Energy Commission (CEC) certification. Stay away from cheap imported inverters without CEC certification.
