DIY Solar Power

Green Earths Energy: Build Amazing Solar Panels Yourself!
'Building Your Own Solar Panels Has Never Been Easier And More Financially Sustainable! This Information Is For Anyone That Wants To Cut Their Dependence On Electricity And Use Alternative Methods For Power!'.
Green Earths Energy: Build Amazing Solar Panels Yourself!

Before even considering solar power, look into other energy reduction projects.  Does the home have adequate insulation?  Are all the doors and windows properly sealed?  Usually these projects are much more cost effective than solar power.

The goal of this system is to reduce the monthly electric bill by $100.00.  This system will only produce electricity during sunlight hours and no battery backup is required.  Let's say that there is a good five hours of sunlight daily and that the local power company charges $0.125 per kWh.

To save $100.00 per month, the daily savings would have to be $3.33 ($100 per month / 30 days per month).  The solar power system would need to provide 27 kWh per day ($3.33 per day / $0.125 per kWh).  With five hours of sun per day the system would need to supply 5400 Watts (27 kWh / 5 hours x 1000).

To account for system losses of 10%, the power would increase to 5940 Watts (5400 Watts x 1.1).

At a typical $3.50 per Watt for an on-grid system, this system would cost $20,790.00.  There is a 30% Federal Renewable Energy Tax Credit so that would reduce the cost by $6237.00 down to $14,553.00.  There could also be additional savings in the form of rebates from the state or local utility company.  Checkout the Database of State Incentives for Renewables & Efficiency website (dsireusa.org) for more information.

This DIY solar power system would pay for itself in 146 months ($14,553.00 / $100 per month) or in 12 years.

As you can imagine, other things need to be considered.

A Solar Power Inverter converts the direct current (DC) voltage from a solar panel array or a solar battery bank into alternating current (AC) voltage for powering the typical lights and home appliances.

It takes 12, 24 or 48 volts DC and converts it into 120 volts AC at 60 Hertz (cycles per second).  For Europe and other locations this could be 220 volts at 50 Hertz.

Although this is a pretty straight-forward application, the inverter is the most complicated part of a DIY Solar Power system.  The inverter has to deal with variations on the input voltage and output loads.  The voltages from the solar panels and batteries can vary as much as 35%.  The loads being powered can range from a small light to a large motor surge at start up.  The inverter must maintain a relatively fixed output voltage and frequency.

You don't need to know the inner operation of the inverter but you should be aware of the basic functionality and features in order to choose the correct inverter for your application.

Power Capacity

There are several power ratings that need to be considered when selecting an inverter.  They are continuous, limited-time and surge.

The continuous power capacity of inverters can run from under 100 to more than 5,000 Watts.  The continuous capacity should be sized in order to power all loads that would be on at the same time.

The limited-time power capacity is the amount of power that can be supplied for a fixed time of maybe 15 to 20 minutes.  This would be greater than the continuous power to allow for appliances that require higher power for a short period of time.

The inverter should also have an appropriate surge capacity to account for the starting up of certain 'inductive' types of load such as motors which require a very high current momentarily.  If the inverter does not have enough surge capacity then the room lights will dim and computers may even reboot.

Power Quality

As mentioned earlier, the inverter takes DC voltage and converts it to AC voltage.  The quality of the AC voltage is determined by the switching scheme that is used internally to get the power frequency.  The AC voltage from the power company has a sinusoidal (sine) waveform.

There are two methods that are used to obtain this waveform in an inverter; one method takes an electrical square wave and modifies it to get what is know as a modified sine wave.  The other method actually synthesizes a sine wave which is known as a true or pure sine wave.

The power from a modified sine wave inverter is electrically noisy due to the distorted waveform.  That means that a hum will be heard in audio devices and lines may be seen on TV and computer monitor displays.  Motors will run warmer.  Sensitive electronic equipment may not even work.  The modified sine wave inverter may be just fine for many applications such as off-grid cabins and such. Modified sine wave inverters are less expensive than pure sine wave inverters.

To eliminate the short comings mentioned above, a pure sine wave inverter is required.  Total harmonic distortion (THD) is a measure of the 'cleanliness' of the sine wave.  For most household applications, an inverter with a THD of less than six per cent is fine.  For some critical applications get an inverter with less than three percent.

Power Efficiency

The peak power efficiency of most inverters range from 85 to 90 percent.  That means that 10 to 15 percent of the power from the solar panels or battery bank is lost.  The inverter itself also uses some power.

The power efficiency is a function of the load on the inverter.  The 'peak' power efficiency is typically at two-thirds of the inverter's power capacity.  With a low load, the power efficiency may fall to less than 50 per cent.

There are many factors to take into consideration when selecting a Solar Power Inverter.  Be sure to study the manufacturer's data sheets and talk to your supplier.

After searching around several distributor sites, I came up with the following costs.  These costs include all of the necessary components. The primary system components consist of a solar panel array and a solar power inverter for an on-grid system. Add batteries and a charger controller for an off-grid system or an on-grid system with battery backup. Typical costs per watt are $2.60 for solar panels, $3.50 for on-grid systems, $6.50 for off-grid systems and $6.50 for on-grid with battery backup systems. This doesn't include mounts or labor.

It is important to control the charging of the battery bank to extend its life. Like most battery chargers, a solar power charge controller monitors the battery voltage and decreases or stops the charging current as the voltage increases. Likewise as the voltage decreases, the controller increases the charging current to the battery.

Controllers come in different sizes depending on the current requirements of the system. Most controllers are designed to handle a 25% over current for a short time but continuously exceeding the current rating will destroy the controller.

The current capacity of the solar power charge controller must be large enough to meet the existing system requirements. As the controller current capacity increases so does the cost, but future system expansion should be taken into consideration.

Solar panels only produce electricity when sunlight is available. Batteries are required to store any energy that is not used during production.

Since batteries are electrochemical devices their performance is a function of temperature. The actual age of the battery and its charge/discharge cycle history also affects performance.

Although there are many different battery technologies, lead-acid batteries are the most commonly used type in solar power systems since they are the most economical. They offer the best performance per dollar.

The capacity of a battery is listed in amp-hours at a particular voltage. So a 150 amp-hour, 24 volt battery would provide 24 volts at 1 amp for 150 hours.

Electrical appliance power 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 solar power 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.

Just like there are many types of battery technologies, there are also different types of lead-acid batteries. There are sealed batteries and those with removable caps. Batteries with caps are preferred so that the electrolyte solution can be checked.

There are also shallow-cycle and deep-cycle batteries. Cycle refers to how much a battery can be discharged before being recharged.

An automobile battery is an example of a shallow-cycle battery. It supplies very high power for a relative short time before it starts being recharged by the car’s alternator. It is not a viable choice for solar power.

Special deep-charge batteries are made especially for solar power systems. They are able to have most of their capacity discharged before being recharged. Although they are capable of discharging 80% of their power before being recharged, it is best to size the number of batteries so that only 50% is discharged before recharging. The less deeply the solar power battery is cycled, the longer it will last.

There should be enough battery storage to allow for 3-5 days of operation without any sunlight.

A photovoltaic (PV) solar power panel is made up of individual PV cells, also known as solar cells. The PV cells are very fragile and must be mounted on a sturdy substrate before being electrically interconnected.  The substrate is then attached to a metal frame and a glass or Plexiglas cover is attached.  The solar power panel is used as a component in a solar power system to provide electricity.  Below is a photograph of a typical PV solar power panel.

Photovoltaic Cell

Photovoltaic cells convert light energy (photons) from the sun into electricity through the photovoltaic effect.  Semiconductor processing techniques are used to create PV cells.  There are a couple of different technologies used.  One uses a silicon wafer-based construction while the other uses thin film technology where a transparent oxide is deposited on a substrate.  The wafer-based cell is the most popular.  All cells are relatively fragile, especially the silicon wafer-based ones, and require special handling and protection.  Here is a close-up view of a wafer-based cell.

Solar Power Panel

Individual PV cells must be mounted mechanically to a firm base to prevent damage.  The base is then typically installed in a metal frame. Since each individual PV cell only has a small power capacity, they must be electrically interconnected.  A certain number of cells are connected in series to achieve the desired voltage and then these groups are connected in parallel to increase the available current. After the electrical connections are made, a glass or Plexiglas cover is attached to the frame to protect the cells and interconnections from damage due the weather and moisture.

Solar Power System

Since each solar power panel is only capable of a certain amount of power, it must be connected to other panels until the desired power level is accomplished.  The array of connected panels is then attached to an appropriate mount for mounting on the roof or attached to a ground-mounted pole.

A solar power system installation typically includes an array of solar panels, an inverter, batteries and interconnection wiring. The system may operate as an independent power source to power applications away from conventional power lines (off grid) or it may actually be attached to existing power lines (on grid) to reduce the electric bill.