John D's posts

Thanks Thomas, your posts have helped me understand some of the fine points of off-grid living.  However, my situation is much different, and I believe that is why we have different priorities where equipment is concerned.  Unlike you, I am grid-connected.  My goals are to get as much from my system as possible, reducing my carbon footprint and my electric bill, and to have a backup source of electricity to serve in the event of a grid failure. 

My VCS helps me to accomplish these goals by cutting and reconnecting the load at precise setpoints.  Before I installed the VCS, I had to disconnect and reconnect loads manually.  In doing so, I was not using my system to its full potential.  On several occasions (when I was away from home or sleeping), battery voltage dropped to unacceptable levels.  To avoid low battery conditions late at night, I found myself disconnecting loads at bedtime.  According to my calculations, I am getting about 50% more energy from my system than I did before installing the VCS.

How much PV do you have?  What do you use for refrigeration, heat, and cooling?  You must be doing a lot of things right to get by on 1600 amphours of battery capacity.

John

I respect your extensive off-grid experience Thomas, but the solution you suggest requires the user to constantly monitor battery voltage.  This may be a good strategy for those with big battery banks, but not so good for those of us with smaller ones.  I work away from home, and therefore don't monitor my batteries during the day.  I also needed to avoid sleep interruptions caused by Low-Voltage-Alarms.  For me, the voltage controlled switch (VCS) not only solved these problems, it allowed me to get more energy from my system, and it reduced my electric bill.  I suspect that Usman's system is also smaller than it should be, considering his loads, and that he might benefit from the solution I've suggested. He could, of course, buy bigger batteries, but not all of us can afford to do that.     

Ken's suggestion is good, but I like to periodically test my batteries under the conditions I would experience if I were to have a power failure.  I like to know how my system will perform in an emergency situation, so I simulate grid power failures once in awhile.  My loads are typical household loads, such as lights, refrigeration, microwave and kitchen items, TV, radio, cell-phone battery charging, and air circulation. I make journal entries concerning the loads, time of operation, and battery voltage readings.

sj
 

Bottom line is that you need another way to remove the load.  A VCS (voltage controlled switch) will meet your needs.  The VCS can be wired to a relay which turns off the inverter when the battery voltage reaches a specific state of discharge. (You set the voltage value).   The second setting on the VCS is the voltage at which the inverter is once again be reconnected.  I have mine set up to reconnect the inverter ONLY when the batteries are nearly fully charged.  By doing that, I am avoinding damage that would occur by chronically undercharging my battery bank.  You can find the details here: 

http://solarjohn.blogspot.com/2008/02/ive-automated-my-off-grid-pv-system.html

I hope that helps.  And, thank you Dave for the kind words.

SJ

How big is the surface area of the solar cell(s) you plan to use?  Maybee a high-intensity desk-lamp will do.  And, if you don't already have solar cells check with a source such as Jameco (www.jameco.com).  They sell solar cells and kits at reasonable prices.  If you're buying things separately, be sure to match the output of the solar cell(s) with the requirements of the load.  Consider a 2 volt motor, for example.  Also, keep in mind that a science fair project should not be a demonstration.  Good luck!

John

I don't want to confuse you with a lot of talk about ohms law and electrical stuff, so I'll get right to the point.  You have an 11 watt panel that I assume is rated for 12 volts.  This tells me that the current flow from the panel to the charge controller will not exceed 1 amp.  To be on the safe side, the wire that you use from the panel to the charge controller should be no smaller than 18 guage.  18 guage wire can handle 2.3 amps, maximum.  Your single LED light draws much less than 1 amp, so you can also use 18 guage wire from the battery to the light.  However, it is important to point out that your battery is capable of putting out much more than 2.3 amps.  A short circuit could cause 18 guage wire to catch fire.  To avoid this, be sure to use fuses. For your application, you could use automotive fuses and fuse holders.  Be sure to install a fuse at one of the battery terminals.  Connect nothing else to this battery terminal.  In doing so, you are making sure that a short circuit anywhere in your wiring will not result in a fire.

The length of the wire is also an important consideration.  Wire has resistance, and you might need thicker wire to keep your voltage drop across that resistance to a minimum.  Here is a web page that might be helpful:   http://www.powerstream.com/Wire_Size.htm

John

Paul, what are your reasons for wanting to go solar?

To lower your electric bill?
Compensate for unreliable grid power?
Self-sufficiency?
A desire to be more environmentally responsible?

How much money are you willing to spend?

John

Thomas,

I'm not sure if I agree with your biblical interpretation.  When condidions are right, organisms thrive.  They multiply so quickly that the resources needed to sustain life are quickly used up, and then they die off in large numbers.  I fail to see how this relates to a "house built on sand". 

However, your theory regarding "the powers that be" maintaining a monopoly is reasonable.  Could it be that the cost of PV is not allowed to fall to a point where it would be cheaper than grid-supplied power?  I often hear about technological breakthroughs, but the price of PV has been about the same for several years.  The cost of TV's, Computer's, and other electronic equipment continues to drop, but the cost of PV panels does not.  I smell a rat!

Becoming self-sufficient, and not a slave to the utility companies, is one of the reasons I've installed PV. I'll continue to enlarge my system, in spite of the high cost, until I AM self-sufficient.  It's worth it! 

Building a house with a solid foundation, IMHO, means taking care of your family.  The person who cheats, doesn't come home, and/or is careless with household finances, is one who builds his foundation on sand.
   

Give a man a fish and he'll eat for a day.  Teach a man to fish and he'll die of mercury poisining within 5 years.

If we don't start taking better care of our earth, air, and water, we're all doomed!  We're not going to be able to feed ourselves, let alone others.  Politicians have let us down.  Under pressure from the Bush administration, the EPA has just relaxed rules for dumping mining waste into streams.  Since we can't count on responsible political leadership, ordinary people are going to have to lead by example.  Install PV, or solar thermal, or windmills, or hydro systems.  Do what you can.  It will make a difference.
 
 

The general consensus is that there will be no single solution when it comes to replacing fossil fuel.  Solar thermal is an efficient way to heat water.  Wind, hydro, and geothermal will be part of the solution.  Bio-fuels will also play a part.  Personally, I really like PV.  No moving parts.  My system just sits there, quietly and efficiently doing its job.  I'm getting closer to a fossil-fuel-free lifestyle, and I see that it is possible.  If I can do it on my limited budget, industry can do it too.  It just takes the desire.  I look forward to a new breed of electric cars, and other advances that will help move us away from fossil fuel.   

Thomas,

It seems to me that anything that can run off of grid-supplied electricity could also run off of a PV system.  My small PV array generates 30 amps.  Increasing the size of my system by 10X would yield 300 amps, and increasing it by another 10X would yield 3000 amps.  The Exeltech MX series of inverters can be stacked to provide 60KW at 208VAC 3 phase.  Strategies could be employed to overcome the high motor-starting current, and other challenges.  Conservation and energy-efficient equipment would be a big help of course. 

Michael,

I decided to "ease" my way into solar PV by starting with a small system.  I've made several upgrades over the years, and I've also made a series of home improvements and purchased energy-efficient appliances.  To make a long story short; as my PV capacity goes up, my consumption goes down.  Someday, I'll be generating as much as I am using. When that happens I'll unplug from the grid, perhaps only reconnecting during extended periods of cloud cover.

Since you're from the east, the electricity you consume probably comes from coal that was mined by blowing the tops off of mountains.  Not only are mountains being lost, the trees and overburden are dumped in the valleys and streams below.  Streams, rivers, and groundwater sources are being destroyed.  Personally, I don't want to contribute to that destruction.  Laws that are supposed to protect the environment, and reclaim mined lands, are not being enforced.  Typically, a thin layer of dirt goes over the rock and mining debris.  Grass might grow, but trees will not.  It's unstable, and not at all suitable for building.  Just imagine the loss of habitat that is occuring as a result of these practices.  Mountain people have been displaced, and their source of groundwater destroyed.  Why is this allowed to happen?  Politicians get big contributions from the coal industry.  I could go on and on, but just Google MTR mining and find out for yourself.  It will make you sick.

I'll continue to invest in PV as my budget allows, regardless if it makes sense from a financial standpoint.  I hope others will do the same. Since we can't depend on politicians to do the right thing, we have to do it ourselves.  http://solarjohn.blogspot.com

John
   

"Why don't we invest in America becoming energy independent."

I agree, and I hope things change dramatically when Obama takes charge.  However, I'm not waiting for that. I've installed PV and a bio-fuel heater.  With those things, and reasonable conservation and energy-efficiency upgrades I've already reduced my fossil fuel use by almost 50%.  Can you imagine the economic and environmental impact that would occur if everyone in the U. S. did that?  It would be staggering!  We've got to stop waiting for the politicians to solve our problems.  We have to do it ourselves.   

An inverter is most efficient when operating near it's maximum rated load.  You can look at the specifications via the alt energy store and compare various brands.  You say that your loads will be around 300 watts, so you might want to consider a 600-watt inverter. You may not be operating at maximum efficiency, but I wouldn't be too concerned about that.  You're probably going to turn off the inverter when you don't need it anyway.  Don't forget to consider the momentary high motor-starting current that you'll need if you plan to operate devices like refrigerators or water pumps.  Exeltech makes good inverters, I love mine.  They are made in the USA, a plus in my opinion.  You won't blow it up if you temporarily overload it.  The voltage just declines a bit until the overload is removed. 

You are wise to only consider a pure sine wave inverter. 

John

People tend to think that they need 1000kwh per month to power their homes.  And, of course, a large and costly PV array would be needed to provide that much power.  There is a perception that to make do with a smaller system would be a step backward, and would result in a less-comfortable lifestyle. 

In reality, most of those who currently use 1000kwh per month could easily get by on half that amount if they would make a few energy-efficiency improvements.  After a modest investment, the homeowner would not experence any adverse quality-of-life issues.  It would actually be a quality of life improvement, since the homeowners electric bill would go down. 

With this in mind, suddenly the cost of a PV system is cut in half, since the size of the system required is cut in half. 

If this can be done in the home, I see no reason why it couldn't be done in industry.  We could easily have a 50% reduction of fossil-fuel use across the board, which would have a tremendous impact on the environment and the economy.

If our government is willing to bail out irresponsible financial institutions, and auto companies who've made bad decisions, perhaps they could boost the incentives for going green, improving the financial outlook of such an undertaking. 

Solar panels could replace oil wells, if you have enough of them.  Expensive, yes, but doable.  If your daily work commute is short, you could power an electric car, in addition to powering your home.  Your food could be grown using fossil-free farming techniques.  Fuel to heat your home could also be grown. I heat mine with corn.  I've already cut my fossil fuel use by 50%, and I have a SMALL pv system at the present time.  Can you imagine the impact if everyone would do that? 
See http://solarjohn.blogspot.com

Amen!  You're preaching to the choir Sh Ja.  I hope our new prez is wize enough to put engineers and scientists back in charge, instead of the money managers who've screwed things up so badly.  http://solarjohn.blogspot.com/2008/11/look-to-engineers-for-change-we-can.html

Converting outdoor solar lights for indoor use may be more trouble than it's worth.  Why not just buy a small solar panel, a charge controller, and a battery.  You can run a bunch of LED lights with a setup like that.

The wind turbine would create drag, more than offsetting the electrical energy it produces.  For it do otherwise would be considered perpetual motion. However, a stationary windmill, used to charge batteries, which in turn could be used to charge an electric car, would work.  You could drive on free energy, created by the wind, or solar panels for that matter, but it would take a lot of them.   

Lee,

The reason you don't see any plans on the web for the system you propose is that it is not practical.  It would require a HUGE PV system.  It's just too expensive to do it that way.  It would be better to consider a system that uses the sun to directly heat water.  But using the sun to power a pump, circulating water through a solar heat exchanger might work.  Take a look at Solar Gary's website for some ideas:  www.builditsolar.com

John

Actually, the relays came from my spare parts box.  They were bought many years ago from Radio Shack.  You can use any relay with a dc coil voltage that matches your battery bank, 12volts dc for example.  Try Jameco, Digikey, or some other on-line source of electronic parts. 

Thanks for the kind words Rene.  If you'll check through my blog archives, you'll find a diagram of my system in my 2/25/2008 post.  You're welcome to duplicate my work, but you'll have to make some adjustments if you're using equipment that is different than mine. The heart of my system is a Morningstar Relay Driver.

My goal is to use as much of the available energy as possible (minimize waste).  I'm constantly monitoring performance, and tinkering with potential system improvements.  I'm working on diversion load control enhancements right now. 

If you have any specific questions, I'll be happy to respond.

   

Without going into a lot of detail, what you need is an automatic transfer switch.  (Some inverters have this functionality built-in).  I have a separate automatic transfer switch, configured to use my inverter as the primary source of AC.  My inverter is configured to shut-down when battery voltage drops below acceptable levels.  When the inverter shuts down, the automatic transfer switch connects grid-power to the loads. 

Your equipment will be different than mine, but basically you need two things:  1.  A way to shut down the inverter when batteries get low.  2.  A way to switch to grid-supplied power when the inverter shuts down.

You might look into an IOTA automatic transfer switch.  I have more information about my system on my blog:  http://solarjohn.blogspot.com

Hope this helps.

John
 

Since neither your roof or the fence seem like good choices, I would consider a sunny spot in the yard.  If you're going to do the work yourself, the least-expensive opition might be a mounting structure made from wood posts.  I would mount four or more posts in concrete.  You could use aluminum rails on top to which the solar panels would be mounted.  Others may tell you to use a single pole, mounted in concrete.  This is not a bad idea, but it might not be as resistant to heavy winds IMHO.  You might also consider a product like Envision's Life Tree.

If you do a little searching on the Internet you'll find plans to build windmills out of items like computer tape drive motors, brake drums, and other things.  I've also seen plans for a pretty cool generator made from an old lawnmower and a car alternator.  I think it would be a better idea to use someone else's successful design than to reinvent the wheel.  IMHO

I agree with Ken, and would like to add this:

If you want to switch back and forth, using either the grid or an inverter, you need an "automatic transfer switch".  Some inverters have this functionality built-in.

Also, if you're wanting to offset $100 worth of electricity each month, you're probably going to need a big PV system, possibly making the project unfeasable.

The wattsun website has some tools you can use for this purpose.  http://www.wattsun.com/

Travis,

If an overnight spike of $1 per gallon for no apparant reason wasn't greed, then what was it?

Yes, an electric car that can get me to work and back each day using no gas would be great, even if I have to charge it most of the time with grid power.  And yes, solar panels are expensive, but I'll keep buying them.  Gasoline is expensive too, and it's climbing faster than solar panels are. 

If your converted Dakota meets your needs, great, but it doesn't meet mine.  I'm leaning toward a series hybrid.  With a series hybrid I could avoid using gasoline for my daily work commute, but I could still use the car for longer trips (at the expense of burning gas), when I need to.     

The car makers are following market demands?  Are you serious?  U. S. carmakers don't seem to be aware that what we need is a small car, perhaps a two-seater, but without sports-car performance and the sports-car price tag.  How could they have missed that?  They deserve to go bankrupt.

Sorry if I've offend you with my comment about Islam, it was a rough week.

Check out the IOTA battery charger line.  They have chargers with different current ratings, from 15 amps up to 90 amps.  Which one would be the best for you?  I think that would depend upon the type of batteries you have. 

Using two inverters connected to the same battery bank shouldn't be a problem, and it can have advantages.  An inverter is most efficient when operated near its maximum capacity.  Using a big inverter to run a small load, for example, would not be very efficient. 

If you're going to run two inverters don't daisey-chain the wiring.  Run separate wires from the battery bank to each inverter.