What is Solar Electricity?

Beginner
Anatomy of a Photovoltaic (PV) Cell
Anatomy of a photovoltaic (PV) cell.
Solar-Electric (PV) Cell Types
Solar-electric (PV) cell types.
Batteryless Grid-Tied Solar-Electric System Diagram
Diagram of a batteryless grid-tied solar-electric system.
Solar-Electric (PV) Module Specifications
Solar-Electric (PV) Module Specifications
Anatomy of a Photovoltaic (PV) Cell
Solar-Electric (PV) Cell Types
Batteryless Grid-Tied Solar-Electric System Diagram
Solar-Electric (PV) Module Specifications

What is Solar Electricity?

Photovoltaic (PV) modules make electricity from sunlight, and are marvelously simple, effective, and durable. They sit in the sun and, with no moving parts, can run your appliances, charge your batteries, or make energy for the utility grid.

A PV array is the energy collector—the solar “generator” and does so via the photovoltaic effect. Discovered in 1839 by French physicist Alexandre-Edmund Becquerel, the photovoltaic effect describes the way in which PV cells create electricity from the energy residing in photons of sunlight. When sunlight hits a PV cell, the cell absorbs some of the photons and the photons’ energy is transferred to an electron in the semiconductor material. With the energy from the photon, the electron can escape its usual position in the semiconductor atom to become part of the current in an electrical circuit.

Most PV cells fall into one of two basic categories: crystalline silicon or thin-film. Crystalline silicon modules can be fashioned from either monocrystalline, multicrystalline, or ribbon silicon. Thin-film is a term encompassing a range of different technologies, including amorphous silicon, and a host of variations using other semiconductors like cadmium telluride or CIGS (copper indium gallium diselenide). Thin-film technology generates a lot of the current R&D chatter, but crystalline modules currently capture more than 80% of the marketplace.

To use the energy from the array, you may also need other components, such as inverters, charge controllers and batteries, which make up a solar-electric system. The components required are dependent on the system type designed. System types include:

PV-DIRECT SYSTEMS: These are the simplest of solar-electric systems, with the fewest components (basically the PV array and the load). Because they don’t have batteries and are not hooked up to the utility, they only power the loads when the sun is shining. This means that they are only appropriate for a few select applications, notably water pumping and ventilation—when the sun shines, the fan or pump runs.

OFF-GRID SYSTEMS: Although they are most common in remote locations without utility service, off-grid solar-electric systems can work anywhere. These systems operate independently from the grid to provide all of a household’s electricity. These systems require a battery bank to store the solar electricity for use during nighttime or cloudy weather, a charge controller to protect the battery bank from overcharge, an inverter to convert the DC PV array power to AC for use with AC household appliances, and all the required disconnects, monitoring, and associated electrical safety gear.

GRID-TIED SYSTEMS WITH BATTERY BACKUP: This type is very similar to an off-grid system in design and components, but adds the utility grid, which reduces the need for the system to provide all the energy all the time.

BATTERYLESS GRID-TIED SYSTEMS: These most common PV systems are also known as on-grid, grid-tied, utility-interactive, grid-intertied, or grid-direct. They generate solar electricity and route it to the loads and to the electric utility grid, offsetting a home’s or business’s electricity usage. System components are simply comprised of the PV array, inverter(s), and required electrical safety gear (i.e., fuses/breakers/disconnects/monitoring). Living with a grid-connected solar-electric system is no different than living with utility electricity, except that some or all of the electricity you use comes from the sun. (The drawback of these batteryless systems is that they provide no outage protection—when the utility grid fails, these systems cannot operate.)

Comments (19)

Ramon Gonzalez's picture

Thank you for your replies. We have 3 solar panels Brand new system less than a month old .What we have in more detail:
-3 solar panels 265W Kyocera Polycristalline
-Charger Controller Schneider MPPT 60-150,
- INVERTER PURE SINE WAVE Power Tech-on Model 1004 12V nominal 3000W Peak 6000W Input 12V output 120AC 60Hz
- 4 batteries 6V (US Battery) 208AMP hrs. Right now we are only using it to operate a small refrigerator 4.3 cubic feet , 1.5 AMPs.
By 6 pm it starts to get dark

Fred Golden's picture

My suggestion is only run the inverter 10 am to 6 pm, until your battery voltage is higher overnight. Check water levels, only use distilled water in the battery. Add more solar panels. The huge inverter might be consuming 5 amps with no loads connected to it. A smaller inverter might also conserve a lot of power. 500 watts might be large enough, and its smaller transformers and capacitors would have less standby losses. Even so, it might consume 1-2 amps with the inverter on and nothing plugged in.

Lowes.com sells a DC clamp on meter that measures dc amperage by clamping the $80 meter over one dc wire. This can tel you the standby losses, and fairly accurately measure input dc power say at noon with the inverter off.

If one panel does not have a good connection, you migght only collect 350 wats at noon, instead of the expected 700+ watts from your 800 watt rated system. You will not get 800 watts unless 1,000+ meters above sea level on a cool (10C) day.

Ramon Gonzalez's picture

We have 3 solar panels 265W Kyocera Polycristalline , a charger controller Schneider MPPT 60-150, inverter 3000W peak 6000 12V and 4 batteries 6V (US Battery) 208AMP hrs. Right now we are only using it to operate a small refrigerator 4.3 cubic feet , 1.5 AMPs.
At midnight we start running out of power and the inverter starts to beep . How can we improve this?? Do we need to add more batteries or more solar panels Thank you. We are off grid completely in a mountain in Puerto Rico

Fred Golden's picture

Ramon, if you are using a modified sine wave inverter to run the refrigerator, then the high torque motor will run very inefficiently. You need a pure sine wave inverter to run a high torque compressor motor.

Also the refrigerator motor will not last long with modified sine wave power. While rated at 1.5 amps on pure sine wave, the refrigerator might be using 2 or 3 amps on modified sine wave power. You have about 750 watts X 5 hours into the battery, so you should have plenty of power.

What is your inverter model number?

Ramon Gonzalez's picture

Thank you for your reply
3 solar panels 265W Kyocera Polycristalline
-Charger Controller Schneider MPPT 60-150,
- INVERTER PURE SINE WAVE Power Tech-on Model 1004 12V nominal 3000W Peak 6000W Input 12V output 120AC 60Hz
- 4 batteries 6V (US Battery) 208AMP hrs. Right now we are only using it to operate a small refrigerator 4.3 cubic feet , 1.5 AMPs.
By 6 pm it starts to get dark

Fred Golden's picture

My thought is the inverter standby power consumption is higher than anticipated. At this point, the best solution is to run the inverter from say 6am to 9 am, shut it off until say 5 pm weekdays, or while you need it at home. Then run inverter say 5-9 pm. Your batteries should have higher voltage after a week of not running the inverter as many hours.

Of course installing more solar panels will allow running the inverter and using power in a more care free way.

Michael Welch's picture
Hi Ramon. Either you are using more energy than you can get out of those batteries, or the batteries have lost a lot of capacity. The place to start for figuring this out is how much energy the fridge uses each day. That will require knowing exactly how many hours it runs, and how many watts or amps it operates at. Or, plugging it into a watt meter (like the Kill-A-Watt product) for 24 hours.

My guess is that it is a combination of using too much energy and the batteries not being at their prime.
Ramon Gonzalez's picture

Thank you for your reply
3 solar panels 265W Kyocera Polycristalline
-Charger Controller Schneider MPPT 60-150,
- INVERTER PURE SINE WAVE Power Tech-on Model 1004 12V nominal 3000W Peak 6000W Input 12V output 120AC 60Hz
- 4 batteries 6V (US Battery) 208AMP hrs. Right now we are only using it to operate a small refrigerator 4.3 cubic feet , 1.5 AMPs.
By 6 pm it starts to get dark

marcos1218's picture

I am thinking of having solar panels installed on my house. I would like to find dircectory of companies and certified installers in the Corpus Christi ,Texas area.

Philip A Jones's picture

I'm building a new home in Goodyear AZ, the sale persons introduce me to a solar company that has done work in the community. I request for a On-Grid Battery PV systems with micro inverters. The Sales person of the company stated that AZ is looking at prohibiting Solar battery systems? In-addition to stating that micro-inverter do not operate well in AZ climate. Can you shed some light on these issues..

Fred Golden's picture

Do you know that a battery based inverter system will not be nearly as energy efficient as a batteryless system, and also is more expensive to install, requires some maintenance that the batteryless system would not require?

So why do you want to include batteries? Do you have a reason such as the need to run medical equipment during a power failure? Do you have frequent power failures in your area? Most new homes have underground power, and thus much less frequent power loss.

In the rare case where you might have a power failure in the middle of summer, you would be best served going to a library, as most inverter systems are not large enough to run the HVAC in your home, unless it is specifically designed to run with a large inverter, large battery bank, and fair sized solar system. For this case, should you have a medical reason to have cooling all summer, I would suggest a ductless heat pump in one room, with about 15,000 Btu's capacity. It would run from a small inverter, and not run the battery empty quickly after sunset.

Personally I would use a batteryless inverter unless you can justify spending the extra $4,000 for the batteries and more expensive inverter.

GregorS-PVpro's picture

You are going to have problems with mini-inverters in the blazing summer months in Arizona, especially if the structure has heating issues during the peak hours of the day. Many factors actually go to play there including direction of azimuth of your roof, angle of the roof, and the capabilities of cooling any system on top of your roof. In addition you require more system equipment if you decide to get a battery backup system. In contrast, a natural gas generator for inclement weather backup might be more cost effective and offers the same safety AC cut-off that is required of a battery backup system without the need for controller and charger control systems or conversion losses from AC to DC and then back again. It simply makes permitting and design much more complicated. Try looking for the best practices of both Solar PV and of generator backups before you make up your mind. Cost is going to be a major factor in that decision. You're just better off with a conventional inverter system unless the load is high and you are running a commercial system. Even then, unless you are using specific Solar PV such as Thin Film, it is more cost effective to use a single inverter and it produces a cleaner energy signal. But always compare. Knowing what you want to do with your back up is also important in determining a practical backup.

Michael Welch's picture
I agree with Ian, look around. Coming to our web site is a good start, but we cannot cover local differences for every state and community. I don't see what is special about the AZ climate that would specifically affect microinverters. So be cautious. I do want to add that microinverters won't interface directly with batteries. You will need a battery-based inverter for that. However, you might be able to have a combination of microinverters and a battery-based inverter.
Ian Woofenden's picture
Hi Philip, I'd suggest talking with a few more solar contractors to get broader information. I'm not up on the politics in Arizona, but have heard that there are changes happening. I might not trust any one person's take on what the changes mean for solar-electric systems. The same goes for the question on micro-inverters -- opinions vary widely. My son is a solar installer in Arizona and his company uses microinverters almost exclusively. His father (me!) is still a bit skeptical of the microinverter trend. In any industry, there are strong opinions based on a variety of factors, which drive specific people to promote specific products. Again, I recommend getting more opinions and bids for your new home. Regards, Ian Woofenden Home Power senior editor
Judy Merry's picture

Under Batteryless grid-tied systems above you say 'they generate solar electricity and route it to the loads and to the electric utility grid'. I live in California (SCE territory) and thought there is no way to route it 'to the loads'. I realy would LIKE to ... how can it be done? Judymerry@aol.com

Justine Sanchez's picture

Hi Judy,
Thanks for posting! In the case of a batteryless PV system, generally speaking the output of our grid-tied inverter will connect with our main service panel by "back feeding" a circuit breaker in that panel. After that point either the loads in the home will use all the power as it is generated by the PV system, if the household power requirements meet or exceed the PV system production. If the PV production exceeds what is required by the household loads then the excess power is then pushed onto the grid. And conversely if the Pv system isn't producing enough power to cover the requirements of the household loads, then the grid will supply the additional required power.
Now that is the common way to interconnect the PV system with the grid…however some incentive programs may require a buy-all-sell-all configuration (perhaps that is the case with SCE?) where the PV system simply "sells" all power to the grid (via a supply side connection and separate meter) and the house "buys" all power from the grid. And this is common for Feed-in-Tariff programs.

Either way your system is producing electricity from sunlight and that energy is offsetting energy that would normally come from other sources, how it is exactly connected and metered doesn't negate that fact.

Hopefully I have answered your question, but if I was off the mark feel free to post again!
Cheers,
Justine Sanchez
Home Power Magazine

joyfifth6's picture

I hope every home in the community can afford to install these solar panel so that we can have a greener environment and we cannot harm the ozone layer. And with regards to energy source this is very ideal because there are no coals to burn or any pollution can accumulate in the city. This is ideal for the city and the local to keep our technology rolling.
Thanks for this wonderful information and this will solve the problem with regards to pollution.

Aaron Longwell's picture

MLA Style for citing a web site would look like this:

"Solar Electricity Basics." Home Power Magazine
3 Dec, 2012. https://homepower.com/articles/what...

Here's some more on the MLA style:
http://www.easybib.com/reference/gu...

Yeneng Sun's picture

Great article! I'm wondering how to cite this page for my school project, any help here?

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