I play devil’s advocate sometimes and search for negative press about solar panels.  It’s not something you see every day.

Today there was a Beltway blogger claiming that some photo-voltaic solar panels that appeared in a photo-op with Barack Obama will take 110 YEARS to pay for themselves.  He is basing this on one quote from a civil servant and the estimate was related to a purchasing option that did not happen.  There is not enough public information for me to try to come to an independent estimate of the payback time for that particular installation.

You have to take just about any estimate of how long it will take before your solar panels pay for themselves with a grain of salt.  The cost of energy derived from fossil fuels fluctuates a lot in response to supply, demand and geopolitics.  Supply is really going to come into play in the coming decades.  Once solar panels are in place, they provide energy for decades without any additional inputs.

Another variable is the amount of sunlight that hits your little patch of Earth.  Solar water heaters can pay for themselves pretty quickly in sunny spots like the California but Londoners might never live to see payback.

I did a quick and dirty survey on the Internet and I saw figures ranging from 10 years all the way up to 200 years.  A company that installs residential solar panels made a somewhat convincing estimate of 15 years before their solar panels pay for themselves.

SolarTradingPost.com saved me a lot of work by publishing an online Solar Payback Calculator

Lots of effort is going into lowering the cost of solar panels but the majority of the panels on the market are still first generation types that cannot be made much cheaper than they already are. Going with  DIY solar panels can shorten solar panel payback time by eliminating some of the costs. Every bit of sweat equity that you can afford to put into your solar energy solution will make the dream of free energy that much closer. Pay someone tens of thousands of dollars to design and install a solar panel installation for your home you may not see a real return on that investment in your lifetime.

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If you are already a bit of a handyman,  learning how to make solar panels is just a matter of details.

The technology required to build a solar cell is beyond the reach of the average homeowner.  The technology required to connect solar cells and house them in a durable solar panel is much simpler.  Durability is the most important criterion for solar panel materials.  Some types of solar cells are quite delicate, especially first generation silicon cells.  If the backing material or frame of your homemade solar panel warps too much, you could end up with broken cells.  Ideally, you should mount cells on your frame in a way that allows for some frame distortion without putting strain on the connections or cells.  Most instructions recommend a 1/4 gap between cells.  Lumber and plywood may be the cheapest materials and they are easy to work with.  If you choose to use wood, it is absolutely vital that you carefully apply a weather seal finish to all surfaces.  Aluminum sheets and framing materials are more durable, but also more expensive.  You may also find yourself shopping for some new tools if you go that route.   Keep your eyes peeled for local deals on materials and decide how to make solar panels based on what deals are available.  For small solar panel projects, you might want to check out architectural salvagers for good quality glass.  It is sometimes more practical to design a panel after you know the dimensions of your used glass.  Plexi-glass is an option worth considering, but you will lose some efficiency over the years as it gets scratched and dull from weathering.  On the flip side, plexi-glass makes more sense if you are placing the panels in a location where glass is at risk of breakage.

Regardless of which transparent covering you choose, they have to be weather tight or they may fog up.  Condensed water vapor inside your solar panel will greatly reduce its efficiency and it could potentially corrode connectors and other hardware.  Flexible sealing compounds are essential.

Photo Credit: GreenForAll.org

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I just had an idea. I think it should be possible to buy used lighting fixtures and retrofit solar power and LED light to them to make your own outdoor solar garden lights. I am not sure that it would save you any money. That would depend on several factors not the least of which is personal taste. If function is more important than aesthetics, you might do well to watch out for sales on basic plastic lights at Walmart. If you want some kind of Victorian wrought iron thing, you might save money by purchasing used lights from an architectural salvage company and retrofitting your solar.

If you decide to shop for off the shelf bargains, make sure they are designed to charge sufficiently. I was very interested in these things when they first started appearing in hardware stores and gardening supply stores. I was, however, very disappointed when I read on the box that they only provided light for a few hours. Market competition and consumer demands have resulted in some pretty good out of the box products in recent years, but the duds are still lining the shelves all over the country.

Many of these product are designed with a small solar panel mounted on a standalone light fixture. I personally prefer the designs that have a separate solar panel connected to one or more lights via 20 foot extensions. Low voltage direct current would be inefficient with longer cords. Having a panel that is separate from your light fixtures allows you to place the solar panel in a spot where it gets lots of sun.

The basic components of a low voltage solar landscape light are a solar panel, a battery, a light sensitive switch and an LED bulb. Housing these components in a rugged, weatherproof assembly is vitally important. If it is done right the first time, you could have years of maintenance free lighting.

Photo Credit: thingamejig

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Are you wondering how to build solar panels to satisfy your curiosity or do you want to build something for practical off grid living? Either way, the basic principles are the same. A solar panel is simply a number of solar cells connected together and housed in a rigid weatherproof structure.

The first step in planning your solar panel project is to determine the desired output in terms of voltage and current. A basic understanding of the principles of electricity are required for this. Each individual solar cell will produce around 0.5 volts. If you wanted to use your panel for something as basic as charging a 12 volt battery, you would need a panel that puts out 18 volts in full sunlight. That means your panel should contain 36 photovoltaic cells connected in series.

A typical arrangement would be 4 cells wide by 9 cells long. The standard practice is to connect PV cells in series within a panel and to create parallel connections of several panels to increase the wattage of the system.

A very important tip that I have only seen from a few sources is to attach the cells to the back of your panel using only a spot of silicon adhesive on the middle of the cell. The materials of your panel will expand and contract slightly as temperatures fluctuate. If you fasten the cells incorrectly they might break.

Another important tip is to test each panel and each connection as you progress with the project. It would be very frustrating to completely assemble a solar panel only to find that it doesn’t work and that you have no way of telling which of the dozens of cells and dozens of connections is at fault. This brings up another important point. Buy more solar cells than you think you need for your first project. Solar cells are delicate and you will probably break a few.

You can use a variety of building materials for the structural parts of the solar panel. Be sure to check out your local used building material outlets before you shell out for new materials. If you opt for lumber and plywood, be sure to seal all sides of every piece to make your panel as weatherproof as possible. The solar cells should last for decades, but a poorly constructed wooden frame will not. Metal materials are more durable, but you may find yourself buying specialized tools and hardware that will add to the cost.

Deciding between glass and plexi-glass is complicated. The plastic material is not as prone to accidental breakage but it may cloud slightly over time reducing your panel’s efficiency. If you are confident that your panels are not at risk from tree branches, hail, or baseballs, you might want to go with glass.

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Photo Credit: basykes

Used solar panels are a little bit like used cars with one very big difference.  The rate of depreciation is a big unknown with solar panels whereas depreciation is the major consideration with used cars.  Some of the earliest solar panels still function with a measurable but small drop in efficiency. If you have an unlimited area for your panels, efficiency is not a factor.  The measurement that you need to compare is dollars per watt.

If you are shopping in person for a used car, you will most certainly check to see if it runs.  The same is true for solar cells and it is pretty simple.  You bring a meter with you.  If the panels put out some volts and amps when in full sun, you are good to go.  Educate yourself about your meter and the expected currents from solar panels beforehand.  Frying an Amp Meter will surely ruin your day of solar panel shopping.  If there is no electricity generated, you should probably walk away.  You cannot predict how much time and effort it would take to repair them or if it is even possible.  An exception to this is burned-out bypass diodes.  If you can identify this problem as the reason for a solar panel malfunction you may be able to pick up some bargains from people who think that the panels are irreparable.  It is a common problem and it is not expensive to fix. Condensation under the glass is something that you want to avoid.

Panels do not degrade in storage.  Some types of used solar panels may have a plastic substrate that has turned brown after years of exposure to sunlight.  While this makes them look less attractive to buyers, it is not a reason to walk away.  If they generate watts when you test them in the sun, you should still include them in your comparison shopping.  Remember to compare dollars per watt generated.

If you test a panel and you are surprised by how much electricity you get, be aware that the nominal rating is lower than actual output in full sun.

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What? You don’t want to sink ten of thousands of dollars into a professionally installed solar power system? You want cheap solar panels?  With some smart shopping and DIY ingenuity, you can harness the sun for less.My first piece of advice for people looking for cheap solar panels is to AVOID OLD ADVICE.  Solar panel technology is in a stage of rapid development.  First generation solar panels are pricey because of the expensive materials and the skilled labor required to produce the cells.  Second generation solar panels hold some promise of affordability, but there is no way of knowing just how low they will go.

My second piece of advice is that FREE is the cheapest that you can get.  Free solar panels are often used and/or damaged.  They may or may not meet your needs.

The sticker price is only part of the cost equation. You have to compare efficiencies as well. A cheap panel with a much lower efficiency than a more expensive one may take decades to pay for itself.

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The efficiency of a solar panel is determined as the ration of power out or electricity; to power in or solar irradience striking the panel.  Usually it is described as a percentage.

Think of irradience as the power of the sunlight striking a given area at a given moment.  Usually in Watts per meter squared.  Since the sun’s irradience is constantly changing due to the earths’ rotation, an average figure normally used by most manufacturers is 1000 w/m².  This will occur around noon on a clear day.

The panel’s manufacturer lists the maximum power in watts on the panel’s nameplate and from the values given, you can calculate the efficiency by dividing maximum power by 1000 times the surface area of the panel.

Example:

For a 40 watt panel with .5m² surface area, the formula would look like this..

70                                                          70
_________                                      ________
1000 x .5                 =                          500                      = .14   or  14%

Note:  Remember the 1000 used is an industry constant in reference to 1000 watts per meter square of solar irradience.

For informational purposes, solar panels are actually called solar modules in the solar industry.   Try not to get confused with all the differing terminologies used.  The field is developing rapidly and self-education is undoubtedly your best path to understanding the world of solar energy.

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I just finished watching a video interview of a professional solar panel installer.  He explains the process of getting set up with residential solar panels step by step.  I like the last step best:

“Watch your meter start spinning backwards.”

Some of the other steps made me uncomfortable, like the one where you give SolarDave a big chunk of money. The process of obtaining permission from your local government sounds like a bit of a hassle as well. In the future, people in the solar power industry are hoping to see some standardization of the approval process. As things stand, the time and cost involved in getting a permit to put residential solar panel on your roof is all over the map.

There is a whole other layer of bureaucracy if you want your system to be tied into the grid.

One way for do-it-yourselfers to avoid some of the bureacracy is to put the solar panels someplace other than their roof.  Using them in a closed off-grid system simplifies things even more.

Thermal solar panels, the ones used to heat residental water, are said to pay for themselves in less than ten years.  Heating water with electricity in one of the biggest inefficiencies in the modern home.  A solar water heater will save your family $6 per month per person and reduce your carbon emissions by 3 tons per year.

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Photo Credit: geocam20000

Unlike PV solar panels, there is no limit to how low-tech you can go when heating water with the power of the sun. Modern systems use vacuum tubes and they are very efficient. A simple collector that uses a black surface encased in insulation and glass with copper piping running through it will work too. Very basic systems are commonly used to raise the temperature of swimming pools. They can also help reduce the cost of heating the running water that you use in your home. Even if you live far away from the equator, you can offset your water heating costs by 25% or more with a solar water heater. Sunnier places can approach a 100% savings.

If you are thinking about a DIY solar water heater there are three many things that you have to consider when comparing plans or making your own. These are COST, DURABILITY, and EFFICIENCY.

There is no point in spending more on your do it yourself project than it would cost to get a factory made, plug and play water heater. Good quality solar water heaters cost in the neighborhood of $5000. One of the cheapest looking plans that I could find on the internet used Coroplast as a collector. The designer was quite confident about the panel’s efficiency but he admitted that it may not be durable enough to install as a residential water heater. So basically his simple solar water heater excels in one of the three considerations but falls short on the other two.

I saw elsewhere that someone had a plan to convert a free supply of old fashioned cast iron radiators into solar collectors. It seems like a simple plan since these things are incredibly durable. In this case, two out of three is bad. While the plan is cheap and the end product would be durable, the efficiency of the system makes it nearly useless.

The most common type of DIY solar water heater is common because it has the best balance of durability, cost and efficiency. These plans typical involve a collector plate made from a conductive metal like copper or aluminum. This plate is coated on one side with black paint. Copper piping is attached to the back of the plate. This collector assembly is then housed in a basic frame with the coil side next to insulation and the plate side covered with glass. A panel like this can be plumbed to the hot water line for you home. Obviously, the secondary system should be between the solar panel and the outlets (faucets). It would be very inefficient to pump water that you had heated with gas or electricity up to your roof on a cold, cloudy day.

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So you might be wondering how solar panels work….  or you might not.  I use a computer every day without having a precise understanding of how the actual processor works.  I’ve looked into that briefly, but I am not going to waste my time when it would be better spent learning how to effectively use the technology.  I feel the same way about solar technology, I’m happy to have just a basic idea of how it works.

This is the simplified explanation of how solar panels work. Solar energy hits the Earth as a particle that we refer to as a photon.  When a solar panel is bombarded with photons,  some of them are absorbed by the semi-conductor material (commonly silicon).  Each photon that is absorbed can potentially shake loose an electron.  An electric current is a flow of electrons.  Solar cells are constructed with materials that force the free electrons to flow in one direction, thus creating an electrical current.  A typical solar panel is composed of a group of solar cells joined in series and/or in parallel by a conductive material.

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