Friday, October 16, 2009

DIY Solar Part 2: Choosing A System

Last week we started talking about DIY solar and covering the topics that will help you decide if you can do solar yourself. There are plenty of different systems that can fit your solar needs. Let's cover the three most popular systems.

Grid Tied Solar
This is the easiest and most popular way to get started in solar power. These systems simply tie into your existing home power system and the utility grid. If your array generates more energy than you use, the energy is sold back to the power grid and creates a credit for you. The advantages of these systems are the relative simplicity and lower initial cost. A system like this typically requires a few panels, some wiring boxes and disconnects, and an inverter. The inverter converts the electricity from your panels to power that your home and the grid can use.




This system also requires an interconnection agreement with the local utility. This outlines just how the connection to the grid should be made and what the inspection schedule is. It is generally advisable to get your power company involved early on for a grid-tied system. Since there are often incentives and rebates in place from the state and the utility, it's well worth the call.

Advantages of a Grid-Tied System

* Initial Cost: The upfront cost of purchasing a system that would provide for a home's entire electrical needs can be very high. With variable climate and weather conditions across the globe, the use of off-grid systems requires expensive batteries. Off-grid systems generally require a secondary power source, such as a gas generator, to provide backup power which adds significant cost to the system. Grid tied systems are much cheaper than off grid.

* Operating Cost: The maintenance cost of grid-tied systems is very low. Solar panels routinely have 20-25 year warranties and some of the panels created in the 1950's as part of NASA's space program are still operational. Batteries associated with off-grid systems require regular maintenance and have a much shorter life than the panels. Backup generators also require significant maintenance and access to a cheap and reliable fuel source.

* Reliability: Grid-tied systems are relatively simple and can have virtually no 'down time' where the customer will be without electricity. The increased complexity of battery and generator backup systems often leads to significant down time and can be frustrating to a home owner. Often poor weather that leads to little energy collected from the sun also means decreased battery and generator performance.

* Flexibility: Having an alternative energy source AND a utility source means you can design your system to meet whatever needs you have now and still have the flexibility to add solar panels later. It also allows you to change your system parameters to meet your different needs in the future.


Disadvantages of a Grid-Tied System

* No Backup Power: Most grid-tied inverters are programmed to shut down when the grid shuts down to precent power from the panels going into the grid and potentially harming utility workers.


Grid Tied with Battery Backup
These systems are very useful in areas with frequent power failures. Provided there is ample sunshine, these systems give the customer more autonomy, while still providing a backup system in the utility grid.

Advantages of Grid-Tied with Battery Back-up Systems:

* Backup Power: with proper system design, they provide continuous power to the customer regardless of utility availability or weather conditions.

* Power Management: these systems make it easier to manage your power consumption, production, and storage.

* Power Pricing: Depending on the utility company's policy, the cost of the batteries can sometimes make up for the rate 'gap', meaning it is worthwhile to store the excess electricity you produce as opposed to selling it back to the utility.


Disadvantages of Grid-Tied with Battery Back-up Systems:

* Complex: increased system complexity means more components to install and tie together.

* Cost: adding batteries and their components can nearly double the cost of a system.

* Maintenance: batteries require regular fluid check, corrosion cleaning, and replacement every 5-10 years.

* Efficiency: batteries are usually about 80-90% efficient meaning you may be losing 10-20% of the power you generate.

* Environmental issues: The manufacturing and disposal of batteries involves chemicals and metals that most eco-minded consumers would rather avoid.


Off Grid Solar Power Systems
For reliable power in remote locations, often these systems are the only choice. They generally consist of a battery bank, a charge controller, an inverter and a solar array. Many systems require a secondary power source such as a gas generator.

Advantages of Off Grid Solar Power Systems:

* Remote Use: these systems are great for cabins or cottages that don't have a utility nearby. The cost of a system is usually far less than running power lines into the property.
* Independent: Maybe best reason of all, the user is not dependent on an outside entity for the power needs.
* Power Management: Since you generate, store, and use all your own power you can optimize your usage.


Disadvantages of Off Grid Solar Power Systems:

* Complex: increased system complexity means more components to install and tie together.
* Backup: most people will want a backup generator in case of inclement weather, which can cause additional headaches.
* Cost: adding batteries and their components can nearly double the cost of a system.
* Maintenance: batteries require regular fluid check, corrosion cleaning, and replacement every 5-10 years.
* Efficiency: batteries are usually about 80-90% efficient meaning you may be losing 10-20% of the power you generate.
* Environmental issues: The manufacturing and disposal of batteries involves chemicals and metals that most eco-minded consumers would rather avoid.


Next up we'll talk about the fun part: installation.

Kriss Bergethon is a writer and solar professional from Colorado. He lives off grid with his wife. Check out his website for more information at Solar Garden Lights.

2 comments:

vacuum1313 said...

Nice generalities, how about discussing actual components needed, where to get them and the costs.

Kriss Bergethon said...

You bet Vacuum, coming in part 3.