Main Home Page
How Does a Segway Work?
Folding Electric Motor Bicycle
Home Wind Turbine
106 mpg Air Car
Alternate Energy Site Map
Sitewide Site Map
Solar Panels can Harness the Power of the Sun at your HomeMany people are fascinated with the idea of "free energy". In a way, energy from the sun is free for the taking, but once you start to investigate further, you will quickly find that harnessing the power of the sun is far from free! The solar panels themselves can be a significant cost, but the rest of the system including mounting hardware, electrical equipment, and installation costs can really add up. The cost of setting up a home solar system will far exceed most people's expectations. Depending on how much you pay for grid power in your area, the payback time to recover your investment could be many years. With that being said, there are also other motivations behind setting up home solar panels. Listed below are some of the most common reasons that I believe that people are interested in solar power.
1) ENVIRONMENTAL REASONS: For some people, the motivation will be to help conserve natural resources by utilizing alternative energy. Some people feel that power being generated from fossil fuels like coal is not a sustainable or responsible way to generate electricity. They also are concerned about the pollution created by burning fossil fuels for power generation. As a result, they feel that they can help reduce their own carbon footprint by pursuing renewable energy sources such as solar power and other sources of alternative energy for their home.
2) ECONOMIC CONSIDERATIONS: For others, installing solar panels at their home will be solely a decision of economics and necessity. Some people live so far off the grid as to make it cost prohibitive to pay for grid power to be brought in to their home. For these people, it can be cheaper to set up an off grid power system, rather than paying the high cost of bringing in utility power to their remote location. It can cost as much as $30,000 per mile to pay for utility power to be brought in to a remote location. So, you can see that if you live far enough away, it would be extremely expensive to have grid power. Most people do not live that far out of civilization, and so most people are not in this category.
3) ENERGY INDEPENDENCE: For others still, the motivation for setting up some solar panels at their home is to provide a means of emergency backup power in the event that utility power goes down for an extended period of time. You can accomplish the same thing by having a good generator to provide backup power in an emergency. Even so, a generator is dependent on fuel to operate and some people do not want to be dependent on a fuel such as gasoline or diesel in order to produce electricity during an emergency. It is true that in certain circumstances of natural disaster or other emergency scenarios, fuel might not be easily accessible. On the other hand, the sun can be a consistent source of energy if you live in an area that has a lot of clear, sunny days.
Whatever the different motivations may be, the common outcome is usually a significant investment in money (and time - if you do the work yourself). Even with improvements in solar technology over the years, most home solar panels are typically around 13-15% efficient, with the most efficient commercially available panels pushing a maximum efficiency in the 17% range. What this means is that you need a lot of solar power square footage in order to be able to harvest a significant amount of power from the sun. Prices have come way down in recent years, but expect to pay anywhere from $10,000 - $30,000 for a typical solar system that can supplement some of your energy usage. If you use a lot of electricity and want to go completely off grid, then expect to pay much more than the prices mentioned. It's too hard to give exact prices, because there are many variables that affect the final price of a home solar system. Suffice it to say that it is not going to be cheap. Granted, you can save money by installing the system yourself if you are qualified (or willing to learn) to do so. Also, the price of a small solar system for people that live in an RV or a very small dwelling can be much lower. Just be aware that if you hope to generate a significant amount of useful power from the sun, then you need to be prepared to pay for it.
Small 2.1kW Solar System with 10 Solar Panels (210W each) Mounted on Shop Roof
The picture above shows my small 2.1kW solar system consisting of 10 Evergreen Solar 210W panels. Personally, my own motivation in setting up a solar system was to provide a means of backup power for my home. I wanted to be able to run my fridge/freezers and have some emergency backup power for lighting and other essential electrical needs. In my case, I combined my solar system with a wind turbine system to generate power to keep a battery bank charged. You can see the wind turbine tower right behind my house in the picture. In my situation, the battery bank is located in my basement, and it normally sits fully charged in standby mode. Most of the power that is produced is diverted to a special water heater. On most days with my off grid system, all the power produced with my home solar panels and wind turbine is used to heat water. This works well for me and my big family because we use a lot of hot water.
Before going any further, let's talk a little bit about the 3 main types of home solar systems:
1) OFF-GRID: In an off-grid solar system, the alternative energy is stored at your home and is independent from utility grid power. This is the type of system that I have at my home. My solar power is used to charge a large battery bank, and then any excess power is used to heat water with a special 80 gallon water heater which is equipped with special 48V DC heating elements. An off grid system can be more expensive than a grid tie system, because you need to have a battery bank in an off-grid system in order to be able to store the electricity that you produce for use at a later time. The sun doesn't shine 24 hours a day (unless it's certain times of year in places like Alaska). As a result, you need to have a way to store the solar energy produced during sunny times for use when the sun goes down or the sky is overcast. The benefit of an off-grid system is that you can be energy independent. During natural disasters or other events that might shut down utility power, you will be isolated from this and still have some power available. The downside of an off-grid solar system is that the cost can be quite high if you have high energy needs. A sufficient number of solar panels, the appropriate charge controller(s), a big enough battery bank, and a large enough power inverter (converts battery power to household power) will be required to meet your power needs. This is a good place to mention that the best investment you can make into your renewable energy system is in conservation. In other words, it's usually much cheaper to figure out ways to conserve energy and reduce your power consumption, rather than spending a lot more money to pay for an oversized system to meet excessive electricity demands. Energy efficient appliances and good habits are a key to minimizing power consumption.
2) GRID-TIED: In this type of system, all electricity produced is fed back into the electrical grid which is hooked up at the home. There are no batteries in a grid tied system, but in a way, the utility grid acts like a "battery" of sorts to store power produced by your solar panels. The power being fed into the grid offsets any power consumption that occurs in the home. If power generation from the solar system is greater than the power being consumed, then excess power is fed back into the utility's grid. Then, in most cases, the utility will pay the homeowner a certain rate for all the energy that is fed back into the grid. This system is commonly known as net metering. Oftentimes, the utility will set up a special electrical meter at your home which will record the amount of energy that you push back into the grid. A grid tied system like this requires permission from your local utility and also expensive equipment in order to be able to safely do so. A downside to this grid tied approach is that when the grid power goes down, your home solar system will also be shut down. This is for safety reasons to prevent utility workers from being shocked while working on power lines when grid power is down. When grid power goes down, the power inverter in a grid tied system will automatically shut off. As a result, a grid tied solar system is not a good choice for emergency backup power. In my opinion, this is one of the biggest downsides of a grid-tied system. Just when you'd need the power the most (when utility power is off), your home solar panels will be a no worth to you in terms of providing backup power. Your home might be covered with a large number of solar panels capable for producing a large amount of energy, but you won't be able to use a single watt of this energy if your utility grid power is down.
3) HYBRID: Thankfully, there is a type of system that offers the best of both worlds. A hybrid solar system is set up to feed excess electrical power into the grid, but in the event of a utility power failure, the hybrid system will have an inverter that is able to stay on and run from battery power. This is probably the most versatile way to use home solar panels, but here again the biggest issue is cost. It's not cheap to purchase a hybrid power inverter. Expect to pay around $3,000 - $4,000 for a good hybrid inverter. One of the most popular hybrid inverters is the Xantrex XW-6048 which can supply up to 6,000 watts of continuous power with limited surges up to 12,000 watts. This is an impressive hybrid inverter with many great features. In my opinion, the hybrid system is probably the best option for the person that is looking to sell back excess power to the grid and also have emergency back up power in the event of utility power being down. Again, the downside of the hybrid system is cost. Like the off-grid system, you will need to purchase batteries which are expensive and have a finite lifespan.
Small 48V Battery Bank Consisting of (16) Group 31 Size AGM Batteries
Speaking of batteries and lifespan, typical flooded lead acid batteries might have a lifespan of anywhere from around 3-7 years. Much of the lifespan depends on two main factors: Quality of the battery and Proper care. Some people have used high quality, heavy duty forklift batteries in their renewable energy systems, and the batteries are still going strong over 20 years later. There are brands of batteries such as Surrette that make batteries with a lifespan possibility in the 10-20 year range. On the other hand, it's possible to use some cheap automotive type batteries that are not intended for deep cycling and have them fail in less than a year. Even the best quality batteries can be ruined with improper care such as: overcharging, undercharging, or neglecting to add water when the electrolyte levels get low. It has been said many times that a person's first set of batteries should be considered "learning" batteries. Many people learn valuable lessons in battery care and maintenance with that first set of batteries. In addition, many people also make mistakes that can shorten the life of the batteries. I made some big mistakes with my first battery bank. The biggest mistake I made was to purchase a set of batteries that sat for a long time. They were brand new Lifeline Concorde AGM batteries, but they sat in a warehouse for a long time. At the time I was purchasing them, I didn't know it, but I later found out from the date codes on the batteries that they were around 2 years old when I got them! This is not good! All batteries have a self discharge rate and even though AGM batteries have one of the lowest self discharge rates, 2 years is a LONG time to sit idle with not boost charge. The batteries sat in a discharged/drained state for a long time. As a result of my ignorance (I was trying to save money and got these batteries "cheap"), I ended up with a battery bank with sulfated batteries that have reduced capacity. I spent a lot of time and effort to try to desulfate and condition the batteries, and while that did help, they are still far from ideal. The batteries do not have full capacity as they should, and none of the batteries are perfectly matched to one another. They were all in slightly different states of sulfation after sitting for so long. The moral of the story is to make sure that you are getting factory fresh batteries. You don't want the headaches that come along with batteries that sat for too long!
A couple more tips related to renewable energy battery banks. First of all, you need to be aware that batteries have a limited number of cycles (discharging & recharging). The deeper you discharge the battery, then the lower the number of cycles that you can expect to get from any given battery. A good general rule is to not discharge a battery bank any more than 50%. In other words, you don't want to completely drain a battery before you recharge it. The deeper the batteries are discharged, then the less number of cycles a battery will give before failing. Another important tip in helping ensure longer battery life is to make sure that the battery is fully charged. A battery that is partially discharged and left that way for a long period of time can be permanently damaged and their lifespan & performance potential will be degraded. That's what I learned the hard way with my battery bank. To try to keep costs down, some people just choose go out and buy some relatively inexpensive golf cart batteries and consider that good enough. Golf cart batteries are designed for deep cycle usage and they can be a decent choice for some people with battery life expectancy of around 5 years with proper care. There are also sealed batteries like Absorbed Glass Mat (AGM) and Gel where the acid electrolyte is not in liquid form like in flooded lead acid batteries. In AGM and gel batteries, the electrolyte is captured in gel form or absorbed in mats located between lead plates in the case of AGM batteries. These sealed batteries are designed to require less maintenance and to produce less explosive hydrogen gas. As a result, sealed batteries are considered safer to be located inside, where as flooded lead acid batteries outgas much more flammable hydrogen and need to be located out in a place with adequate ventilation. Sealed batteries are also considered "maintenance free" and do not require adding water regularly like in flooded lead acid batteries. The downside of these sealed batteries is a much greater cost. You can easily pay double (or more) for a good quality AGM battery. In addition, these sealed batteries do not typically last as long as some premium flooded lead acid batteries, and they do not tolerate overcharging as well because there is no way to add water to a sealed battery that has gassed off excessively. Even though they are "sealed" batteries, there is still a safety vent on each battery that releases excessive pressure from inside the battery such as is caused when overcharging. These pressure regulated valves can be popped off and then allow hydrogen gas to vent off. Eventually, a sealed battery will dry out and be ruined if it outgases too much.
Mounting Evergreen Solar Panels on Shop with Unirac Rails (5 panels mounted, 5 to go)
Enough about batteries... back to a little more details about my specific home solar panels installation. As noted above, I chose panels made by Evergreen Solar. I bought them through Sun Electronics. I had a good experience with Sun Electronics and so I can recommend them to others based on my own experience. They had great prices and I received great service from Shelley Ospino in the Miami office. Now, regarding the Evergreen Solar panels themselves, I have been pleased with them, but since Evergreen went out of business, then you won't find these panels readily available any more. Last I checked, Sun Electronics still had some Evergreen solar panels available, but they are the only place that I know about that still has some of these panels for sale. I bought B grade panels which meant that there were cosmetic defects on the solar panels. Defects such as small chips or cracks along the edges of some of the silicon solar cells was obvious. Discoloration of some of the solar cells was also visible in places on some panels. Once they were mounted on the roof, then these defects were not visible. I chose the B grade panels because they were less expensive at the time, and because the performance was the same as the A grade panels. Solar panel technology has been changing over the years and there are a variety of different types of solar panels. The Evergreen solar panels that I bought are known as polycrystalline type.
Just to give you an idea of some of the most common types of solar panels, below you will find the descriptions of 3 different types of solar panels.
1) Polycrystalline - This is probably the most common type of solar panel made today. As the name implies, in a polycrystalline solar panel there are multiple silicon crystals joined together to form each solar cell. Generally, it is less expensive to produce solar panels in this way as compared to monocrystalline solar panels. Polycrystalline panels are sometimes also referred to as multi-crystalline.
2) Monocrystalline - A monocrystalline panel is made in such a way that each solar cell is formed from one uniform silicon crystal. This type of solar panel is generally more expensive, because it is more difficult to consistently make larger silicon cells. A monocrystalline solar panel is typically slightly more efficient than an equivalent sized polycrystalline panel, but today the efficiency differences are often negligible.
3) Amorphous - Another type of solar panel is the amorphous panel. A thin film of silicon solar material is deposited onto a plate of glass. For their size, amorphous panels do not produce as much power as a polycrystalline or monocrystalline. On the other hand, amorphous solar panels have been known to be more effective in gathering power from the sun during low light conditions.
This was just a very brief summary of 3 different types of solar panels. Regarding the installation of my solar panels, first of all, let it be known that I am moderately afraid of heights. Not that it will stop me from doing something that I need to do, but it was enough of an issue to make me dread working on the roof of my shop installing my solar system. In the picture above, you can see that I have a fall protection rope hanging off the edge of the roof. Before I started the project, I decided that I would buy fall protection gear. Thankfully, I was able to find a used fall protection harness and rope on eBay for a very good price. I had the rope tied to one of the big support poles on the other side of the shop, and I draped the fall rope over the top and down the other side where I would be working. When I ordered my Evergreen solar panels, I also ordered the Unirac mounting system. Since the area where we live can be quite windy at times, I wanted to make sure that my solar panels were securely attached to the roof of my shop. I ordered extra L-feet (the brackets that bolt to the roof) to ensure that my mounting rails were held down very well. I used 1/4" galvanized lag screws and pre-drilled pilot holes through the sheet metal roof and into the wood supports underneath. I used generous amounts of high quality GE silicone sealant. Since I was dealing with metal on metal, then I felt that the silicone was a good choice. Different roofing materials would require different types of sealant. In the photo above, you can see that I have 7 L-feet per rail. Then the panels are held down to the rails using special mounting clamps. I have a large shop that is over 100 feet long, so my solar array looks relatively small compared to size of my shop. Just to give you an idea of the size of this solar array, the Unirac mounting rails are 17 feet long. One more note about mounting solar panels. It is important to choose a location where you can most effectively harness the power of the sun. You want to try to keep the panels angled in such a way as the directly face the sun. A tracking system that moves the solar array to face the sun, or a mounting system that allows the angle to be adjusted during different times of year, can help to increase the amount of power that you can harness. In my case, I tried to keep it simple and minimize costs, so I went with a mounting system that keeps the panels at a fixed angle all the time. I wanted to keep the panels flush along the surface of the roof to minimize the possibility of strong winds ripping the panels off the roof. Physically mounting the solar panels is an important step, but then you need to electrically connect your home solar panels before you can tap into the power of the sun. In my case, I already had a battery bank located in the basement of my home which was set up for my wind turbine. I needed to run over 200 feet of wiring from the solar panels on my shop roof over to the house. This was a longer distance than ideal, but I decided that I didn't want to drill through the roof of my house. I didn't want to risk possible water leaks down the road. I have a large shop and even though I was careful to try to eliminate potential leaks, the consequences of a water leak dripping on farm equipment was much less of a concern than a water leak in my house. In any case, I ran the wiring through PVC electrical conduit down the roof and then into my shop where it ran along the wall. Eventually it dropped down and needed to travel the rest of the way to the house underground.
Trenching for the Solar Panel Wiring (notice wind turbine behind the house)
As mentioned, I wasn't looking forward to working on the roof of my shop. Another part of the solar project that I wasn't looking forward to was the trenching that would be needed to run the wiring to the house. I had some experience with trenching when I ran the wiring of my wind turbine into the basement. I can still remember how brutal it was to dig in the rocky, hard packed soil. While trenching for the wind turbine, I was hitting so many big rocks that it severely jolted my hands and arms. After swinging the pick for hours and hours, it got to the point that I would cringe every time I swung the pick, because it was literally very painful. I eventually even snapped the hardwood handle of the pick! Anyway, when thinking about the longer trench needed to run the solar panel wiring, I dreaded the idea of digging in the rocky soil again. I inquired about renting a trencher, but I was told that it would not work in our rocky soil. I knew that I would have to dig the trench by hand again, but I decided that I would try to work smarter instead of harder. I bought a soaker hose and used it to soak and soften the ground where I needed to dig. After running the soaker hose for several hours, I would let it soak in overnight and then dig the next day. I would soak again, and then dig some more. I did this over the course of some days. This made a big difference, and it was much easier to trench this way. In addition, it turns out that the soil on this side of my house did not have as many big rocks, so that also made the trenching go faster. I was planning to dig it all by myself, but some of my children wanted to help and so the extra help made it even easier. In the end, the trenching was not as bad as I expected. Nevertheless, I was sure glad when that part of the project was done. Even though the wiring was rated for direct burial, I ran it through PVC electrical conduit to further protect it.
Speaking of wiring, this brings up another important note to mention here. It is critical to choose the right size wiring for your home solar panels. If you choose wire that is too small, then you will be wasting energy with additional voltage drop. Basically, some of the energy will be wasted in heating the wiring. If possible, it is desirable to try to limit voltage drop for a solar system to around 3%. There are a few different ways to try to reduce voltage drop in solar system wiring, and we'll look at some of these ways below.
1) Keep wiring runs as short as possible. The longer your wiring, then the higher the resistance and the greater the voltage drop. If you can locate your solar panels closer to your battery bank or where you will tie into the grid, then you can benefit in saving money on wiring. You will be able to get away with less expensive wiring if your runs are shorter. For longer runs, you will need to go up to a larger size (gauge) wiring in order to minimize energy losses. In my case, I knew that 200+ feet was not ideal, but I knew that the roof of my shop was the best location for my solar panels, since I did not want to drill through the roofing on my house.
2) Run the largest gauge wiring that you can afford. This one is closely related to #1, because the longer your wiring run, then the larger gauge wiring you will need to use in order to minimize losses. I ran a voltage drop calculator and found that I would need to run large 4 gauge copper wire in order to keep voltage drop closer to 3%. In the end, I chose to go with 6 gauge copper wiring and accepted a larger voltage drop of around 5% in order to substantially save on wiring costs. I found a large roll of high quality 6 gauge direct burial wire on eBay for a very low price and so I went with that. Going up to 4 gauge would have more than doubled my wiring costs and since my finances were limited, I just made the choice to go with the 6 gauge wire. So far, I don't have any regrets, because voltage drop calculations are based on maximum power output of the solar panels and in reality my panels do not run at their maximum output all the time. At least that's the case with mine, since they are mounted at a fixed angle which is not optimal during many times of the year. As a result, most of the time the power loss through the wiring is not as significant as I calculated using the maximum power output. Now, if a person had their solar array mounted to a tracking system that moves the solar array to face the sun optimally all the time, then you might want to go with the bigger gauge wiring to harness as much power as possible. Actually, if a person had the money to be able to afford an expensive tracking system, then paying the additional money for larger gauge wiring would likely not be a problem. Since my finances are limited, then I am always weighing the cost to benefit ratio in my decisions. If I had more money to spend, then I would definitely go with the larger gauge wire.
3) Increase voltage to reduce amps. Another way to try to minimize electrical losses in the wiring is to try to keep the current (amps) as low as possible. This can be done by wiring your panels in such a way as to increase system voltage which results in lower amps for any given solar array. It's the higher AMPS that leads to additional resistance in the wiring. Resistance to the flow of electricity in a wire is directly related to the amount of current that is flowing through that wire. As a side note, that's why utility power is transmitted over long distances at very high voltages. This helps keep losses at a minimum. You may not be aware of this, but high power transmission lines can be as high as 765,000 volts! Most high power transmission lines do not run this high, but on the other hand there has been some discussion of transmission lines running high as 1,000,000 volts. Even the lower voltage transmission lines that run in the 100,000 - 200,000 volt range are still very high. When the power lines get closer to the point of use (home or business), then transformers are used to step down the voltage to a lower level. In a similar way, if you can wire your home solar panels with a higher voltage, then you will have less losses and you won't need as heavy gauge wiring to efficiently transfer the power. The key to being able to run with higher voltages is to have a charge controller that it designed for high voltage. Many common solar charge controllers are designed to handle a maximum of 150V. If you exceed this voltage limit, then you can fry your charge controller. That is true of the TriStar MPPT-45 charge controller (shown below) that I chose, so I wired my panels so that the maximum system voltage should never exceed 150 volts. Another important thing to keep in mind when selecting your solar panels and deciding how to wire them, you need to make sure that the maximum voltage never exceeds the voltage limit of the charge controller. This is not just based on the normal voltage output of the panel, but rather it needs to be based on a "worst case" scenario calculated from the lowest possible temperature in your area. Something that many people do not realize with solar panels (neither did I until I started learning more), is that the power output of a solar panel is affected by temperature. Ironically, when the sun rays are most intense, such as during the summer, this is not necessarily the time when the panels are capable of putting out maximum power. That's because as the silicon solar cells heat up, they become less efficient in producing electricity. On the flip side, as temperature drops, the efficiency of the solar cells increase. Because of this, the maximum voltage output of a solar panel will often be at a time when the temperature is very low. When calculating the maximum voltage of your solar panel system, be sure to take this into account. You don't want to fry an expensive charge controller because of a simple oversight.
TriStar TS-MPPT-45 Solar System Charge Controller
There are other charge controllers that are designed to run with higher voltages. Midnite Solar produces the Classic line of charge controllers that are available in higher voltage models. The Classic 150, 200, and 250 give you the option of running higher solar system voltages. As the model numbers imply, you can safely run up to 150V, 200V, and 250V respectively. In addition, the Midnite Classic has a feature known as Hyper Voc. Basically, this means that you can exceed the voltage limit by your battery bank voltage (so a Classic 250 would be safe up to 298V with a 48V battery bank). The Classic would stop the flow of power to your battery bank if you are running in the Hyper Voc range, but it would prevent your controller from being damaged. It is an additional level of safety. The Classic has many other great features. If I think the Classic is so great, then why do I have a Tri-Star TS-MPPT-45 charge controller? Quite simply, it is because I bought the TriStar controller a long time ago when I was slowly collecting parts for my home solar system. I bought it before the Midnite Classic was even available to purchase. As a result, since I already had it and my finances were limited, I decided to just keep it and see how it worked. It turns out that it works well. I do also have a Midnite Classic 150 controlling my wind turbine, and I like it a lot. So, I would recommend considering the Classic for your charge controller needs. They are designed to work for solar, wind, or even small scale hydro power. If you really want to run high voltages, Xantrex also offers a solar charge controller that is capable of handling up to 600V. Keep in mind that these higher voltage levels bring with it a higher risk of electric shock. In addition, many of the conventional solar system components such as circuit breakers are designed and rated for a maximum of 150V.
As I've been writing this article, I keep thinking about other details and aspects about solar power. I realize that it is impossible to capture every detail in one single article, but my hope is that this will give you a little glimpse into some of what is involved in setting up some home solar panels. Having both wind and solar power, I can say from personal experience that solar power is more straight forward once you have everything set up and operating properly. Unlike a wind turbine, solar panels do not have any moving parts. Once they are set up, they can operate maintenance free for 20-30+ years. There may be electrical equipment such as the charge controllers that needs to be replaced more often, but the solar panels themselves should be maintenance free for many years. Even 20-30 years later, they still have the potential of working well. It's just that the silicon wafers used to produce solar panels can lose some of their capacity over long periods of time, so they might have reduced power output 30 years from now. Solar power is much more hands off after the initial installation, while wind power has the potential to have more challenges and hassles. In most cases, people looking to get into alternative energy would probably be better off getting into solar power. As was stated from the beginning of this article, harnessing the power of the sun is not exactly "free power". There are substantial costs involved in setting up home solar panels along with the accompanying system. Even so, prices continue to come down on solar panels, and various government incentives can help to offset the cost even further. If you are interested in the idea of solar power for your home, then now might be a good time to pursue it. Having a solar system that produces your own power from the sun can be very satisfying.