Pre-Update: I apologize for not having photos showing details explained in this diary. This is because of the restrictions on hosting photos and I do not currently have an account at Photobucket or Flikr or any of the approved sites. This will soon change, and when it does I will update this diary. Thanks for the understanding in advance!
UPDATE: Enough users have asked me to write a diary with detailed explinations, drawings, photos, etc. of this project. OK-- you got it! Although I have a lot of it done already, I want to take a few more pics and do some more detailed explaining on how I did what I did and debunk some of the myths about how changing over to a supplimental solar system can yield a reasonable monthly savings on the electric bill. Some commenters have asked me how I managed to save up to $100 a month doing this -- well it is a joint effort combining the supplimental solar (which does NOT replace conventional grid power), eliminating a component of grid useage, more efficient appliances and a realization of waste and elimination of that waste, which means a slight lifestyle change.
..............
As we all know, the price of energy is going out the ceiling. At the same time, carbon emissions are contributing to global warming. If we Americans continue to use electricity at the rate we are currently using it we will soon need to build more electric generating plants. Some states like Texas propose (warning -- some links on page are PDFs) building many more carbon-producing coal plants. And we all know what that means.
Four years ago the central air conditioning in my house failed. The old system was 20 years old and really was mechanically at life's end, so it was just not worth paying a high price to fix. The solution for me was to install several inexpensive window air conditioners. You may have seen these at several home improvement and big box stores -- those $70 5000 BTU models. These small A/C units actually work very well and as a hidden benefit, use a lot less electricity than the old central air unit did. But one thing was certain, using these room A/C's reduced my electric bill by about $40 a month and that got me thinking....
Since these small A/C units use so little power, could I actually run them using solar power? Could I use the very sun that heats my house to cool it down instead? Electricity way out here in the rural Texas countryside is not cheap, so I did a bit of research, math and experimenting. If I could suppliment my power useage with solar, then it would save me some cash and as a side effect, help reduce the carbon footprint.
I am a retired electronics engineer. I still maintain a website for those who are involved in my neck of the woods, which is amusements and entertainment. The website also offers up many projects for the experimenter and college student, and for those who are just beginning to get interested in electronics and want to give a few projects a shot. I go into detail how each project works and how you can build it yourself and enjoy learning from your own work. You can visit my website at Lupine Systems. (Some of you may have met me at Netroots Nation where I displayed the LCD Calculator project completed and ready to use.)
In the past year or so I have been bombarded with E-mails on how to save money on electricity and if there are any projects that can be done by the layman using solar, wind or other alternate-renewable sources.
The answer to that question is YES THERE IS!!. In fact, a small, but effective solar installation can be done with very little effort.
Being an electronics engineer I am aware of just how many appliances in a household are actually 12 volts once you get rid of the power supply which converts the 110v AC down to low voltage DC, so I knew that many appliances could be run directly from 12v DC as they are in RVs and camper trailers. If I could use this 12v directly, it would be to great benefit because I would not need power inverters to up-boost the power to 110v.
TVs, laptops, cell phone chargers, computer monitors, many stereo systems and some lighting all can be run on 12v DC. Just think of how many of those wall-wart transformers are in your house..??? If you get rid of the wall-wart, then in most cases you have 12v (some 6v or 9v, but to get that from 12v is a simple regulator).
Four years ago, when I replaced my A/C units, I did some research into what kind of solar panels were available. One of the stops I made was Ebay. There I found many different panels for a number of applications. Many of these panels are part of a particular product, such as a solar powered charger for your cell phone, others are the type of panels used on top of houses. I was interested in a larger panel, the type you would normally use in a full-blown installation. And I found several at a very affordable price. So I wound up buying a panel with a winning bid of only $230 plus a $30 shipping charge.
The panel I purchased was a Siemens 12v, 200W panel. Using Ohm's Law, you can calculate the available current from this panel to be 16.67 amps. Ohm's Law states Power in Watts [P] = Current in Amperes [I] times the voltage in Volts [E] for the equation P=IE (okay, PIE but it's not what you'd want to eat!). Therefore P=200, we don't know I, and E=12. So divide 200 by 12 you get 16.67. I = 16.67 amps.
A panel which can produce this much current is a rare find at that price but makes for an excellent choice for a small solar installation.
Battery Truth or Consequences
Every solar installation needs to have batteries as a storage medium and to act as an electrical "ballast", or cushion. The solar panel itself cannot produce enough current at all times to operate the load at a constant rate, so therefore you need some form of storage to balance out the load.
It is a misnomer that you can only use certain types of batteries for solar electricity storage. However it is true that certain battery types are better than others and it is regulation in some states that certain battery types must be used in full-blown installations. But for what I was up to, about any high-capacity storage cell would do.
So off to the auto parts store to purchase a car battery -- a medium duty battery would do just fine. Although a marine-use deep-discharge battery would be better and would last longer, the whole idea behind the project was to get an inexpensive system up and running, and to prove that it could be done using easily obtainable parts.
So with a bit of work on top of the house to mount the panel, the entire system was coming together. I installed the panel on the rooftop in an area fully open to sunshine both in the morning and in the evening and throughout the day, and connected the panel to the battery more-or-less directly using regular 16-gauge Romex. I also installed a 20-amp blocking diode between the panel's positive terminal and the battery's positive terminal. The diode is necessary because solar panels actually draw power rather than produce it when they are in the dark, and if the battery were to be directly connected to the panel without the diode, the battery would run down at night simply from the drain of the panel.
Purists Note: The blocking diode drops the voltage by about 1 volt. This is not an issue because the 12 volt solar panel is actually 16 volts output. This rating difference is normal because the panel's rating is based on actual voltage at point of application. It is kinda-like a car battery is actually 13.6 volts, not 12 volts. Once the panel is wired to the battery array via a blocking diode and some length of copper wiring, the available voltage will be 13.6 volts or darn close to it. This is also why quite a few commercial solar panels are 17 volts -- to accomodate for the loss in the wiring and to give a bit of electrical "overhead" needed by the power inverters for smooth regulation and for passing clouds, birds or other obstructions which may from time to time lower the voltage.
Now some of you readers out there are going to recognize that it is possible to overcharge the storage battery this way, but with a constant load on the system the possibility of this happening is very little, and even if it did there would be no measureable damage to the battery. Car batteries are very forgiving in cases like this so I was not too overly concerned with the possibility of overcharging. Besides, battery charging is a function of voltage, current and time and as long as the voltage from the panel never exceeds the voltage rating of the battery the two will act as if they were two batteries in parallel.
WARNING: If you try any of this, do NOT put a car battery inside your house! This is because car batteries emit hydrogen gas when charging and this gas can build up and become explosive. Keep the battery outside. In my installation, I put the car battery on a wooden stand up against the house and constructed a wire cage around the battery to keep squrells and other critters out. You do not want to sit a battery on the ground or on concrete because this can cause the battery to discharge.
The next step was to wire the house with low voltage wiring. This can easily be done using standard home wire Romex. You should however use 14-gauge wire (12-gauge is even better) since DC current does not travel as well as AC does.
Important Note: Why wire for low voltage?
Most solar systems take the power from the solar panel and battery array and feed it into a power inverter. The inverter is only necessary if you are going to be using nothing but 110v or 220v appliances and lighting. Modern inverters are very efficient compared to those of years past, but any waste is still waste, and so the question arrises....why invert and waste when you can use direct?
Before wiring the system to anywhere, there must be a fuse or breaker installed. This is simply to prevent fire in case of a short -- the same reason you have breakers in your house today. But regular breaker boxes are made for normal AC grid power. That's OK as long as you have the right breakers in place for the correct voltage and current.
The breaker panel I chose was a Homelite 8-breaker 100A (AC 110v) box, available very inexpensively at a popular home improvement store. The exact same panel with a different model number is also available at RV dealers but at a much higher price. A quick phone call to the factory and a conversation with the engineers there led me to find that there were breakers specifically made for 12 volts that fit my breaker panel. This is because the breaker panel I chose is often used in RVs and can be used for 12 volts. So I ordered a set of breakers rated in 12 volts. The breakers look different but still fit the same space and work the same, but you cannot plug the 110v versions in side by side with them because of a "tab" on the 12 volt breaker. This is to stop mixing of the breakers which would be a disaster.
The solar panel connects to the box with the POSITIVE terminal to the bus bar and the NEGATIVE to the return. A simple run of Romex to each place in the house I wanted 12v to be was the next step and that took a few hours but was even easy for me --a guy with heart disease.
Now that I have all of this 12v power, what do I do with it?
For one, I use it to power my laptop. Free computing! I also use it to charge my cell phone. And with a quick stop to an RV dealership, I found those nice twisty-fluorescent bulbs popular nowadays in 12v models. So I use it to light up the room at night as well.
During the day I can run most everything without any restriction, but at night I limit the useage to only what I need to use.
Now back to where this all began. Air conditioning. I found out that I needed to add another four batteries to the system to provide enough power to run one of the small A/C units via a power inverter. But that is not a major problem. Adding more batteries is fairly easy to do. And small power inverters capable of running these tiny A/C units are inexpensive and work very well. And since I only need the air conditioner in the bedroom at night, I run only one of these A/C's so the five-battery array is enough to keep the one A/C running all night long with plenty of power to spare. (During the day the grid power is used for all of the other A/C's because of the number of A/C units being run. This system cannot run but one A/C both night and day.)
I also installed a switch between the bedroom A/C and the grid power and solar source so I could switch between the two in case the battery power was low or there was not enough sunshine to fully recharge the battery array during the day. The panel produces enough power during the day to power the A/C and recharge the batteries using a battery switch tied to a timer. This way while one battery is running the A/C, the panel is recharging the others and eventually the clock switches the batteries back-and-fourth and gets around to charging every battery.
In the end, I run my laptop and my desktop, my LCD TV, the lighting in the dining room, hallway, den, bedrooms and bathroom, charge my cell phone and laptop batteries and one A/C unit, all from this small, supplimental solar system built from parts obtained from Ebay, an auto parts store and a local home-improvement center. The system is capable of doing all of this because of the 5-battery array, the Texas sunshine and the use of the power in its raw 12-volt form without wasting any of it with unnecessary inverters. Sounds like a lot, but 16A of charging current being switched between 5 batteries all day in the Texas sunshine, which seems never to quit, produces a lot more power than one may think.
No, it is not the best system. But it works. And it was cheap to build. And it helps keep the cost of electricity down for someone who lives on a fixed income. The results of all of this experiment was a savings of over $100 each month on the power bill. Not bad for an investment of less than $750 and a few Saturdays. The system paid for itself in less than a year and is now still working fine, saving me cash month after month and reducing the carbon footprint by reducing my dependence on grid power, which I still have to use for the stove, hot water heater, refrigerator, washer and dryer and a few other things around the house.
If enough folks were to do this it would impact the need for future power plant construction.
And you can do this too. And that is where you come in. Do you want to have me write a detailed diary outlining how I did what I did here at my home, with intricate step-by-step procedure and pictures? Or do you want to dive into other solar power projects which may be simpler or more affordable? There are many possibilities and opportunities for YOU to help reduce carbon emissions while enjoying a substantial savings on your electric bill.
So I need your input/suggestions. The project I mention above is not for everybody and does contain a few "shortcuts", but it was never to be something major-- it just so happened to turn into something major.
So give me your thoughts and in the meantime, Stay Wolfy!