Solar Photovoltaic Power
Solar power is one of the first things that comes to most people's minds when the subject of alternative energy comes up. Solar power first gained wide public awareness during the 1970's energy crisis, and solar technology has advanced substantially since then. With present-day rising electricity costs and available Federal Tax Incentives – there has never been a better time to invest in your power future!
Photovoltaic (PV) panels, which use sunlight to produce electricity, can be very useful in northern climates. While the manufacturing process and the mechanism by which they work is technical, they are simple to install and maintain in actual use. Following is an overview of the function and purpose of photovoltaic panels, as well as the many benefits they have in alternative energy systems.
- How Photovoltaic Panels are Used
- Using PV Power in Alaska
- Types of Panels and their Uses
- Benefits of Solar Energy
- How Photovoltaic Panels Work
- Related Product Information
Solar electric panels are probably one of the simplest alternative energy sources to use. They can be mounted on a rooftop or a freestanding solar array rack.
Once mounted, a wire needs to be run from the solar panel to a solar charge controller, and a wire needs to be run from the charge controller to a deep cycle battery bank. If the building's electrical system runs on DC power, the battery bank can be wired directly into the system.Multiple solar panels increase the wiring complexity a bit, and of course, most homes will use 120 volt AC power or a combination of AC and DC power. AC power systems will require the use of an inverter to convert the DC battery power into useable 120VAC power, and other details can be added, expanded and customized from there.
However, the fundamentals of using solar power remains simple. The solar panels turn sunlight into electricity, and that power is stored in a battery bank for household use. The household power needs are drawn out of the stored battery power, and the solar panels recharge the batteries when their charge drops below a certain level.
Solar panels can be very practical in Alaska, contrary to popular belief. Our long hours of summer sun are ideal for taking advantage of solar energy. Also, photovoltaic panels operate more efficiently in colder temperatures, meaning they produce more power per daylight hour as daylight hours grow shorter. Here are the main considerations for effective use of solar power in northern climates:
- Photovoltaic panels will not be much use from November through January, as there simply aren't enough hours of daylight to produce much power (and you'd have to spend a lot of time clearing snow off the panels to make the most of those few hours of light). Plan on having an alternate source of power during these months. Wind generators can be highly effective, if your site has sufficient wind through the winter. Engine generators can also be a good backup source of electricity, as the weather has no effect on their output.
- While solar energy is very economical as compared to generator power, it's still a fairly expensive form of electricity. Powering electric heating elements is not an efficient use of your alternative electrical supply. Space heaters, stoves, hot water heaters and clothing dryers should be replaced with non-electric (gas or wood) heat models. (This isn't a bad idea for folks on grid power either!)
- Make sure to place your solar panels in a spot where they won't be shaded by overhanging trees or other obstructions. Even partial shading of a solar panel can significantly reduce its power output.
Solar panels are available in types and sizes for everything from recharging AA batteries to powering large household electrical systems. You can buy small, flexible panels designed for maintaining a fully charged battery (ideal for vehicles that go into storage for months at a time). You can get household power panels ranging up to 120 watt models, and you can add multiple panels to expand the system to any size you need. Of course, the most durable, efficient and highest output panels will be more expensive than the lower-end models, but for large, long-term applications the greater initial outlay is worthwhile in the long run.
Solar PV Panels
Flexible panels are limited to smaller output sizes. They tend to be more expensive per watt of rated output, and less durable in long-term applications. However, they're extremely convenient for intermittent use where the panel may need to be stored and moved around regularly.
Unframed rigid panels also tend to be available primarily in smaller sizes. They're much lighter weight than the more common framed panels, and convenient for portable applications. What these panels lose in convenience as compared to flexible panels, they make up in cost per watt and durability.
Framed rigid panels are the most common type of solar panel for full solar power systems. They are the most durable type of panel, and are generally used in permanent or long term installations for household, RV or marine power systems. Large framed panels can get quite expensive, but with 20-25 year warranties, high durability and low maintenance, they're worth it.
Solar roofing is one of the newer styles of photovoltaic unit. For a large household system, solar roofing can be found that mimics the appearance of regular roofing shingles or regular metal channel roofing. Probably the most cosmetically pleasing option for a full-house solar system, these products are now becoming available on a widespread basis.
Photovoltaic power is one of the most benign forms of electrical power available. It produces no emissions, uses no fuel, and other than the power storage batteries, PV system components are all solid-state, with no hazardous materials involved.
Most rigid photovoltaic panels come with 20-25 year warranties on their rated power output, and they require virtually no maintenance during that time. Cleaning the surface of the panels and maintaining a proper fluid level in the storage batteries are the two primary maintenance duties.
For villages and individuals outside the reach of the grid power system, solar panels can be a highly reliable and relatively economical source of power. They are also ideal for maintaining charge levels in RV and marine deep-cycle batteries, since RVs and recreational boats are used primarily during sunny summer months. In northern climates, photovoltaics are perfectly suited for powering remote summer vacation cabins, or providing a seasonal power source for year-round homes.
For commercial and industrial use, PV panels can be put to use powering monitoring stations, signal lights, telecommunications towers, and other remote sites where there are no full-time employees stationed. Solar power is also useful for small power loads even in grid-powered areas where running grid power to the load would be inconvenient or expensive (such as signal lights on an airstrip or parking lot lighting).
Solar electric panels are composed mainly of silicon. Silicon is used because it naturally releases electrons (electrical energy) when hit with a photon (light source). The trick for photovoltaic manufacturers was to find a way to "catch" the displaced electrons and use their energy.
Most solar panels consist of a clear protective top layer, two layers of specially treated silicon with collecting circuitry attached to the top layer, and a tough polymer backing layer. From there, the panel can be framed (adds durability) or unframed (reduces weight), and in some cases the layers are even comprised of flexible materials. The vast majority of PV panels work in the same way:
The top layer of silicon is treated to give it an electrically negative character. The back layer is treated to make it electrically positive. Due to these treatments and added elements, the top layer is rich in electrons, and the back layer is relatively electron poor. These two layers are separated by an electrically charged junction, which allows electrons to flow from back to front, but not the other way around.
When light strikes the PV panel, some of the photons are absorbed by the silicon layers. The photons cause electrons to be released from the silicon crystal, and those electrons "wander around" looking for somewhere to attach themselves. Some of the electrons are freed from the bottom layer, and they find their way through the junction into the top (electron rich) layer. Some of the electrons are freed from the top layer, and since they cannot travel to the bottom (electron poor) layer, and are being "crowded" by new electrons from the bottom layer, they are left free to be collected by electrical contacts on the surface of the top layer.
Those collected electrons are routed through an external circuit, providing power to the electrical system attached to the panels. The circuit is completed when the electrons return to the bottom layer of the PV panel, find "resting spots" in the electron poor bottom layer, and wait for the next photon to shake them loose.
There are no moving parts in the PV panel, so maintenance is limited to keeping the junction boxes and wiring free from moisture and corrosion, and keeping the surface of the panel clean enough to allow light through to the silicon layers.