John D's posts

Jonathan;

I use a Lascar USB data logger.  I paid around $70 or $80 for it, and it has only one channel.  It can measure DC voltage up to 30 volts, making it ideal for measuring the output from my panels, or my battery bank.  When I want to measure current I add a shunt resistor (low ohms, high watts) in the circuit, and measure voltage across it.  I simply apply ohms law in order to determine current:  I = e/r.

Try Googling "Lascar Data Logger", or check my blog archives:  http://solarjohn.blogspot.com

I know there are other inexpensive options, including a data logger board for a pc, but I don't have that information handy right now.

Let me know what you decide to do, as I'm interested in an upgrade to the single channel Lascar I currently use.

John
 

Thomas is correct.  Another way to look at it is to think of each solar panel as a battery:

Wired in series, the voltage is the sum of the individual panel voltages.  If all series-wired panels have the same maximum current rating, the total maximum current will be the same as the current available from one panel.

Wired in parallel, the voltage is the same as the voltage of an individual panel.  Maximum current will be the sum of the current from each of the panels. 

If panels of different current capacities are wired in series, the maximum current will be the same as the current available from the smallest panel.  (Avoid doing that).

If you'll be wiring your panels in parallel, you'll want to get a charge controller and an inverter that will operate on 12-volts.  For a large array, you will probably be better off with series-parallel array wiring, and a charge controller and inverter designed to operate at a higher voltage, typically 24 or 48 volts.

I hope this helps.

John

If you already have the 6-volt batteries, and their in good shape, why not use them? 

I'm not sure how to include a sketch, so I'll explain this way:

Think of your ten 6-volt batteries as five pairs of two batteries. For each pair, add a wire from the positive terminal of one to the negative terminal of the other.  Now you have five positive terminals and five negative terminals that have no wires on them.  Connect wires to join all five positive terminals together.  Connect wires to join all five negative terminals together.  You now have a series-parallel wired, 12-volt battery bank. (It will be easier to understand if you draw this as I've described).

By the way, if each of your six volt batteries is rated at 100ah, you now have a 500ah battery bank (not a 1000ah battery bank as you might expect).  This is due to the series-parallel wiring.

John   

Roberta,

Since it's not a good idea to parallel two battery banks made up of different types of batteries, here are a couple of ideas:

Morningstar makes a charge controller that can charge two separate battery banks.  You might also consider using a battery switch, perhaps to connect one battery bank or the other to your inverter. 

You could also come up with some sort of automatic switching scheme, possibly using a voltage-controlled switch. I'm probably going to use my Morningstar Relay Driver to do something like that, as I plan to replace my still-good battery bank in the near future.

I hope you'll let us know what you've decided.

John

I use my off-grid system to power my refrigerator and freezer.  I started out with a basic system;  PV panels, charge controller, batteries, and inverter.  I wanted to automatically switch over to grid-power when battery voltage was low, so I added an automatic transfer switch and a voltage controlled switch.  It's working well, and I'm happy to be getting as much as I possibly can from my system without the need to constantly monitor it and manually switch the loads.  You can read more about my system here:

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

John

The power unit needs to be capable of supplying more power than the laptop requires.  So it follows then that the power requirements for this particular laptop will never exceed 81.6 watts (IMHO).

John

The output of the power adaptor, and the actual power requirements of the laptop are two different things. You really need to measure power over time. 

Keep in mind that power usage will fluctuate, peaking when you access the hard-drive or the CD/DVD drive. 

If I were you, I'd take a Kill-A-Watt meter with me as I shop, and find a salesperson who will allow me to do some pre-purchase testing.

After you've purchased the computer, go into "Control Panel" and adjust the "Power Options" to turn off the monitor and hard drive after a period of inactivity.  Allow the system to hybernate, or go into standby mode, as well.

John

If you're planning a small system it's smart to be concerned about the self-consumption and efficiencies of the system components.  I chose a Morningstar charge controller because of it's low power requirements.  You can find those specifications on the Morningstar website.  As I recall, it is difficult to find that information concerning the MX-60, but I'm sure it uses more power for it's own operation than my Morningstar product does.  On the other hand, the MX-60 does things that the Morningstar product is not capable of, which might justify the larger self-consumption. 

Quote from Thomas:
 
Got a main breaker on your home? Go to it and try to turn it off. Easy right? Now leave it off. Through the keys to your petroleum fired automobile into the trash and leave them. Cant do it can you? Neither could I and neither could the other six billion people on the planet Earth I wager.

Thomas,

I disagree.  Although I can't do it at the present time, I'm building up to that.  My PV system gets bigger and better as my budget allows, and I currently generate about 10% of my household needs.  I expect to own an electric vehicle within the next three years, and power it with energy from my PV system.  And, at the rate gasoline prices are rising, everyone else will do the same eventually I suspect.

I don't think it is a neurological disorder that keeps us from turning off the main breaker.  We use electricity from the utility company because it is cheap and convenient, period.  Most of us here on this forum are interested in alternaives, but we're the exception.  In those few areas of the country where electric rates are high, people are taking notice of the alternatives.

Solomon,

Are you for real?  Assuming that you actually can get them, please don't poison my planet with nuclear materials.  You're time would be better spent working on "clean" alternatives.

Thanks!
John

Kimberly,

I don't know exactly where in Missouri you are, but you might want to attend an energy fair in New Bloomfield or Marshfield.  Check this link for fair dates and information:  http://www.hereshelpnet.org/

I'm no expert on hybrid systems, and I'm not sure how to answer your question.  My small system is wired for 12-volts.  It's simple really:  5-pv panels wired in parallel, a 12-volt charge controller, 12-volt batteries wired in parallel, and a 12-volt Exeltech 1100-watt inverter.  I've added a voltage-controlled-switch to prevent over-discharging my batteries.  Of course you'll need more equipment than that for a hybrid system. 

Bill,

Before getting into PV system design details, have you considered running electrictiy from your house to the shed?  That could probably be done for less than the cost of a PV system.  I'm guessing you would spend at least $2K on a PV solution if you did all the work yourself.

John

Jason, here's something that might sound far-fetched, but deserves some consideration never-the-less.

Put up an off-grid PV system at your dad's house.  Charge him for the electricity it provides.  In doing this, you'll meet all of your goals.

1.  You're spending money, so your net worth stays within the range necessary to keep you from losing your government funds.
2.  You've expressed an interest in helping the planet, and the proposed system does that.
3.  You're not wasting your money on junk, just to keep your net worth low.
4.  As you earn money, you can continue to enlarge the system.  This allows you to regulate your net worth.
5.  You can negotiate a rate with your dad which will benefit you in your sistuation.  Remember, it's not just the electricity you're providing, he's also paying for an emergency power system for times when the grid is down.
6.  In doing this, you'll be running a legitimate business.  You need not lie to the IRS.  This should please your dad since you're doing nothing illegal or immoral.

There you go, all of your goals are met!

John

I'm curious William....  You have a roof over your head, so why can't you put solar panels on it?  Are you in an appartment building?  And if it isn't practical to put PV on you roof, why not in the backyard?

I live in a city and I have PV on my roof.  It's a small off-grid system that meets some of my electrical needs.  It also serves as a backup system for when the grid fails. I have pictures posted on this website, and on my blog.   

John
   

Hello Paul,

Any effort to conserve natural resources and protect the environment, regardless of how small the effort, is admirable.  When I installed my small off-grid system it caused me to think about how much electricity was being wasted in my home.  I started working on energy conservation with the hope that someday my PV system could provide all of the electricity I need.  Two years later I'm still doing things to reduce my load, and on enlarging my PV system.  I hope others, like you, will do the same.  Everyone benefits.   

Thanks Robert,

that information is helpful.

John

Hello again Robert,  I'll try to answer your questions:

First of all, I don't want to mislead you.  I use electricity from the utility company, and natural gas for my furnace, water heater, and clothes dryer.  Still, my goal is to minimize, if not eliminate, those.  I'm working on that a little at a time.  Most of my lights are CFL's, and I replace older appliances with the most energy efficient ones I can find. 

I live in Southern Illinois, 13 miles east of St. Louis, MO.

My stove, which serves as a supplement to my natural gas furnace, burns shelled corn.  I've cut my heating bill since I started using it, even though the price of corn has doubled in the past two years.  I've written about it here:  http://solarjohn.blogspot.com/2007/11/i-burn-corn-to-heat-my-home.html

I put up my first PV panel about 2 years ago, and I add to that whenever I can afford to.  It has served us well when grid power failed, and I'm now trying to use power from the system on a regular basis in order to reduce my electric bill.  I'm about to install a voltage-controlled switch in order to automate the process.  Too much energy goes unused while I'm at work during the day.  I write about that on my blog as well.

My chest freezer is small, about half the size of a "typical" chest freezer.  Instantaneous watts ~ 100.

When I decided to buy a new refrigerator I looked for one with a low energy-star power rating.  I didn't want a small one because extra trips to the grocery store use more energy than the extra electricity I'll use with a larger one.  I ended up with a 25 cu. ft. Sears Kenmore, with an energy-star rating of 499kwh/yr.  In reality, it uses more than that.  When the compressor first kicks on, the Kill-A-Watt meter shows about 150 watts.  That drops to about 120 after it has been running for a few minutes.

I don't use DC for anything.  My inverter is an Exeltech 1100 watt (pure sine wave).  I love it.  About the only thing it won't run is my washer and dryer.  The motor-starting current is just too high I suppose. 

I'm interested in knowing how much you can get out of those batteries before you have to shut things down.  My next major purchase will be the replacement of my battery bank, and since funds are limited, I want to choose wisely.

John
 

Hi Robert,

My system is about the same size as yours, so I was interested in what you wrote.  I have 425 watts of PV, and I've seen it produce a little over 30a at times, probably "edge of cloud" events, as you mentioned.  I'm still on my "learner" set of batteries, which are about 2 years old now.  They are 105ah Marine Deep Cycle, and I have four of them.  How do you like your Trojans?  My system is not yet automated, so I use it evenings and weekends when I can monitor it closely.  I've found that I can get about 1.5kwh on a good, sunny, Saturday or Sunday.  When I use the system in the evening, I get about 0.5kwh out of the batteries.  These measurements were the result of connecting my Kill-A-Watt meter to the output of the inverter.  The load is typically my refrigerator and freezer, or about 250-watts when both compressors are running, and maybe a light bulb or two. 

I was wondering how this compares to your system's production.  I suppose you do better, because of your batteries. I would like to be able to run the motors on my bio-fueled stove all night, but I'm not quite there yet.  That amounts to about 185-watts.   

John

Keith,

I'm wondering if it would be better to skip the tracker and use the money you save for more solar panels and batteries instead. 

John

I would be concerned that doing this may cause warranty problems.  Even though my warranty doesn't specifically say anything about channeling the suns rays onto the panels, it does mention improper use and installation.

Mounting panels flat on the roof, as you suggest, would limit the air-flow under the panels.  This would result in a heat build-up, which would reduce the output of the panels.

John

This is ONLY MHO:

I hear reports of problems with trackers, both mechanical and control-board related, and I'm sure you know that batteries have a limited lifespan.  Beyond that I would recommend proper grounding, fusing, and lightning protection.  Wiring and electrical connections should be checked once a year, and the PV panels should last over 20 years.

John

It would be helpful if you would better define your power needs.  Consider checking each item with a Kill-A-Watt meter.  Record kwh, and the hours-per-day that each item runs.  Motor starting current is also an important consideration.  Does the cistern motor run continuously?  You're off to a good start, with energy-efficient lights/appliances and alternative heating.   

John 

Steve,

You mentioned that Ameren is your utility company.  Do you know about the Ameren plan that lets you pay for electricity based on demand?  If you're unable to go "grid-tied", at least you might be able to use solar or wind energy to offset a portion of your electric bill.  By using electricity from your alternative system during peak hours, you should do well.  Check here for more information:

 http://www.powersmartpricing.org/

John

I should have mentioned that I'll be paying as little as 2 cents per kwh, and I'll be billed as much as 15 cents per kwh. 

Having said that though, I realize that my biggest savings will come from conservation and energy-efficiency improvements.  If I can avoid using my central air conditioner during the day when rates are highest, I'll save the most. Storing and retrieving energy is an interesting experiment, but load-shifting is how I'll save the most money.   

John

My utility company now has a program that allows electric customers to pay for electricity based on demand.  Generally speaking, rates go way down after 10:00pm, and are higher during the day.  To make the most of this plan, I'll run my dishwasher and laundry equipment late at night.  Furthermore, I'm planning to store power in batteries at night, and use that power during the day when electric rates are high.  I'll also use power from my PV system, of course, but it supplies only a fraction of my household needs. 

It's unfortunate that this plan doesn't help to reduce my carbon footprint, but I'm working on that as well.  With PV panels at about $5.00 per watt, it will be awhile before I can disconnect from the grid entirely.

I've recently purchased a three-stage battery charger, and a transfer switch.  I'm designing a circuit that will monitor battery voltage, and switch the inverter on and off depending on battery SOC.  I would like to hear from others who are doing similar things.

For details, check out my blog:  http://solarjohn.blogspot.com

Information about the utility company plan:  www.powersmartpricing.org

John

Thanks Nick!

I enjoy participating in the forums, and I hope my contributions have helped others.  At the same time I've learned a great deal from forum contributors, and I appreciate the information provided by the alternative energy store's website.  I believe that those of us who use PV and renewable energy can be considered pioneers in what will someday be common. It's good to be in on the ground floor, and I'm glad to see so many of us helping each other.

John D.

Ed Begley Jr. rides a stationary bicycle to produce electricity.  He uses that energy to make toast, but you could just as easily use it to charge a battery. 

Check him out:

http://www.livingwithed.net/

John

Quote:  "If there is an enemy in this, its our own selfish desires for energy."

Thomas,

I don’t think it is selfish to desire energy.  Maintaining a comfortable temperature in our homes helps keep us healthy.  It takes energy to prepare food and keep it fresh.  Our children are better educated because they live and go to school in comfortable and well-lit surroundings.  I agree that we should strive to be free of foreign and domestic energy sources if that energy comes from burning fossil fuels.  Those things, after all, contribute to global warming, and supplies are not infinite.  I’m not a fan of nuclear energy either, given its problems.  For these reasons, I embrace renewable energy.  And yes, I know that it takes energy to produce solar panels, but it is better to do that than it is to just burn fossil fuels and end up with nothing.  Another thing to consider is that unless we want to live like cave men, we will never be independent.  After all, I can’t make a solar panel, or a decent battery, etc.  I’ll try to use as little fossil fuels as possible, and avoid sending money to foreign countries that want to harm us, but at the same time I'll try to maintain a comfortable home.  I don't feel selfish or guilty for doing that.

John

I am not aware of tankless water heaters for the purpose of heating your home.  My tankless experience was not good.  I wrote about it here: 

http://solarjohn.blogspot.com/2007/10/environmentally-friendly-products-are.html

John

Paying $5 per watt for PV (just the panels) when I could be purchasing electricity for less than ten cents per kwh IS as sacrifice.  Buying expensive equipment, installing it, maintaining batteries, and monitoring the system are just a few of the tasks I'm willing to do.  By doing so I am not just helping to reduce global warming, I'm also preserving fossil fuels for future generations.  I also have a backup system for times when the grid is down.  In other words, being as self-sufficient as possible is important to me.  Should a natural disaster occur in my area, you probably won't see me on TV begging for help (as you saw in New Orleans after Hurricane Katrina).   


John