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Ask Jeff Yago
Solar & Energy-Related Issues

By Jeffrey Yago, P.E., CEM
Jeff Yago

Solar power for existing well pump

We have an existing well that pumps near 10 GPM to a pressure tank. I'd like to power it with solar but from what I am seeing most solar well pumps pump to a cistern or holding tank of some type. Are there any systems that would be on demand as we have it now using batteries?

Thanks in advance!

Greg in Georgia

Greg:

The reason you are not finding this type of solar pumping system is because it would be a major waste of money. To power an on-demand well pump providing house pressure using a solar-powered pump means you would need a well pump in the 1/2 HP or larger size range depending on well depth. Since it would be an on-demand pump, this means it would only operate a few minutes every few hours when somebody flushed a toilet or took a shower, and the rest of the day it would not operate. When any pump first starts, it has an electrical power demand that can be 2 or 3 times its "run" power requirements, and this means you will need an inverter in the 3,600 to 4,000 watt range to handle this large startup electrical load.

Since almost all residential inverters are 120 volts and almost all well pumps are 240 volts AC, you will either need a second inverter or a 120 to 240 volt transformer at additional cost. Next, this inverter or inverters will draw as much as 200 amps DC (depending on battery voltage) when this pump first starts up, which would destroy a battery bank that did not have multiple deep-cycle batteries. Now that you have purchased these expensive batteries, inverters, and the solar array to charge the batteries, your pump will only operate a few minutes on most days, which means the system will sit idle the rest of the day, as the solar array will quickly re-charge the battery bank, due to the short pump run time, and then stop charging. This means all this available solar energy will not be collected, making this a very expensive waste of solar equipment.

If you install a small DC powered solar pump that has a small flow rate and low head pressure, it can still fill a 1000 gallon tank on an average solar day, and this small pump can be connected directly to the solar array, no batteries, no inverter, and no transformer. When the sun is shining, the pump starts filling the tank, when the sun goes down the pump stops but the tank is full. If the tank is located above the house you will not need another pump, if it is not, you will need an on-demand pressure pump from the tank to the house. If you go this route, be sure to have a good sand filter on the line from the tank as you will get some sand pumped out of the well which you do not want to run through the pressure pump. You will also need a carbon filter and bacteria type ultra-violet light filter on the water where it enters your home's plumbing as the water standing in the tank can start growing things if it sits for long periods. We advise clients to "dump" some bleach in their tank each week.

Good Luck,

Jeff Yago

Jeff:

Thanks for all the info. I can't really see replacing the pump and adding a reservoir. However, I could see powering more than the pump with solar cells and batteries. We have a commercial dog kennel and a home on 15 acres that has great exposure. Perhaps I should consider powering more than the well pump alone so as not to waste all that potential energy. Should I find a specialist in our area to assess our situation? If so, can you recommend someone in Georgia?

Thanks for your advice!

Greg

Greg:

Here is a list of NABCEP qualified solar installers in your state. This national organization tests and certifies solar pv installers and their technical requirements and testing are very difficult:

Kelly Provence, Dahlonega, GA (706) 867-0678 koprovence@solairgen.com

David George, Decatur, GA (404) 312-7155 inquire@intownelectric.com

Freeman William, Savannah, GA (912) 898-9627 willkfree@comcast.net

Tell them hi for me and good luck,

Jeff Yago


Question regarding off-grid insurance

My dad and I had recently read the question you answered regarding Solar Home Insurance, and he wants to know if the response you had givin to the question is subject to be updated? We are also having problems finding adequate homeowner's insurance for an off-grid property.

He wants to know if the information you had givin in the response is outdated or not. Has the defnition of off-grid changed much in Insurace companies' opinions since more off-grid and solar energy homes have been built? Has it gotten easier to find Insurance for these types of property?

Any information that can be givin will be much appriciated.

Thank you

Faith

Faith:

All of the information I provided to the earlier question about insurance should still be valid, except that things are getting better. I am even starting to see ads from lending institutions for solar home loans so I would assume they would have worked out the insurance problems if they are loaning money to buy or build a solar home.

I would do an Internet search and this should point you in the right direction.

Good Luck!

Jeff Yago


Solar precision questions

Greetings Jeff,

Thank you for many practical directives relating to solar power through your magazine articles.

Our family is in the process of transitioning our home to solar just north of Raleigh, North Carolina. The first step has been to change the lighting through-out to energy efficient. Now we are in the process of transitioning to energy efficient appliances. The next phase will be purchasing inverter, solar panels and finally batteries.

The questions we have are the following:

1. We wish to set up the system to be utilized for non-major appliances. Solar will not be used then for ac/heating, washer/dryer, or water heater. Can the wiring be direct-wired (with ac fuses) from the inverter to the respective circuits in the home fuse box?

2. Any recommendation of solar panel distributors in the eastern part of the US? We likely will purchase panels for a 1.2kw array. It appears most of the distributors in the US are from the west and the current shipping rate greatly increases the price of panels.

3. For a 1.2kw system, likely with a 12 volt, 2000 watt xantrex inverter, would ask what would be the most feasible set-up for the battery back-up?

The last phase of the project will be to install a solar thermal heater. Not sure if we will buy or build it... to be determined.

There may be some inquiry on your part to give more precision to these questions. Please ask.

Sincere thanks,

Jon and Mary-Lou Kroeze
Creedmoor, NC

Jon and Mary-Lou:

Sounds like you are off to a good start by first reducing your energy loads. Directing the energy from an inverter tgo specific electrical loads is easy, just treat it like a backup generator and install a second circuit breaker panel. These are usually 100 amp panels having 8 to 12 circuits. You remove those circuits from the existing main panel and re-route to this panel for each circuit you want to be supplied from the backup power system.

Most higher quality inverters will include a built-in transfer switch which will route the utility power from your existing main panel into the inverter then out to the new emergency panel. This will require installing a new circuit breaker in the existing main panel to supply the inverter, which in turn feeds the new emergency loads panel. Most inverters can be programmed to supply the new emergency loads from a solar charged battery until the battery gets low, then switch to either a generator or back to utility grid power coming from the main house panel.

I disagree with your choice of a 2000 watt 12 volt inverter. This is way too small for this type application, and the low 12 volt DC input would require a very high current draw and large battery wire size. The higher the battery voltage, the less wear and tear on the inverter and the smaller the battery cables and fuses. If you are considering a DC refrigerator or freezer, you may need to select an inverter based on the battery voltage required for this DC load. However, 24 volts is the lowest system voltage I would recommend, and 48 volt is not out of the question. Never under-size the inverter if you have budget problems. You can always add more solar modules later, but you do not want to under-size the inverter and then have to replace it later with a larger unit.

Finally, you should not have any problem finding a solar dealer in North Carolina. I was asked to teach a 3-day solar installers course several years ago for the North Carolina Solar Energy Center, and there were many electricians and contractors attending this class. Your state is very active in promoting solar and you should be able to find a good solar installer through the State Energy office. P.S. Tell them hello from me!

Good Luck!

Jeff Yago


Battery bank transport

Hi Jeff.

You have given me advice in the past and it was much appreciated. I have a small home solar setup which uses two MK/ DEKA 183 Ahr gel cell batteries. If I am moving what is the best way to transport the batteries? MK/DEKA does not make terminal boots to cover the terminals; this pretty much means I can’t set anything on top of them that would risk creating an ‘arc’ between the battery terminals. Also, I might be living in an apartment for awhile and have to store my PV equipment. Any advice about keeping the batteries healthy while in storage (w/ out a steady supply of sunshine)?

Thanks again for your sage advice.

Respectfully,

Matt H.

Matt:

Almost all deep cycle batteries are shipped with a protective plastic insulator "cap" over the positive terminal. I am sure any battery supplier in your area would give you one as they throw them away by the bucket load.

Once a battery has been in use, its not good to let it discharge and stay that way for long periods. You could hook up a portable battery charger about every 3 months to replace the charge that will be lost just sitting around.

An easier way might be a small battery maintainer charger. These are about the size of a pack of cigarettes and cost about $15. They are electronic and put out a very tiny charge which you leave connected all the time. These are designed for things like a generator starter battery which may sit idle for months but needs to stay fully charged.

Good luck!

Jeff Yago


Energy related puzzlement

Jeff,

We recently had our home completely remodeled from top to bottom. As part of the construction we had all new wiring, panels, and associated electrical work done brand new. Additionally we had a 3.2 KW solar array mounted onto our new metal roof. This solar array is grid inter tied with a 8 gel battery backup connecting 3 circuits in our home. We moved in on December 15th 2007 and have lived without any issues until June 7th, 2008.

On June 4th, 2008 we had a violent wind storm that dropped a tree limb on the power line serving our street. The power went out, our batter back up kicked on and all was fine. On June 6th the power company restored power to the street and we were back running on AC power from the power company with the solar array supplement.

Starting from June 7th through the date of this letter my wife and I have been experiencing physical discomforts such as intermittent “electrical shocks” and what feels like a mild electrical current running through our bodies. Additionally we have been getting recurring dull headaches where neither of us have had them before.

We have had our electrician, solar company, city inspector and power company out to check things out and all have said that they cannot find anything wrong.

The only time that we find complete relief from these physical symptoms is when we shut down the power at the utility junction breaker.

I am reaching out to you to see if you have any ideas of what may be causing these physical symptoms. We are both sane individuals in our early 40’s with no history of mental or physical ailments of this type.

I hope to hear from you soon.

John N

John:

I am not a doctor and don't play one on TV either, but I can provide some information that may at least rule out some things.

I won't insult you about how many of these type problems can be psycho-somatic, as I am sure you already know that and still feel there is something physical involved.

You did not describe your system but said it was grid-tie and battery based. From this I can only guess that it is a 48 volt DC system which would hardly give you a shock even if you touched the battery terminals unless you were standing barefoot in water! Of course many grid-tied solar arrays are wired for over 400 volts DC which can give you a severe shock.

You said the solar array was installed on a metal roof and you had a recent strong storm, and all this started after the storm. I have seen bad wind and rain storms cause one or more of the array wires to short out on the array frame or rub a bare spot on a array wire touching the metal roof. Normally this would trip the array ground fault breaker, but you may not have one. Also, if the metal roof has a poor ground or the ground fault circuit was wired wrong, if the array is now energizing a metal this may not trip the ground fault breaker.

I am not sure how even a metal roof could cause the problems you are experiencing even if it is energized, but this is easy to check. Did the service installer do a "meg-ohm" test of each array down lead in reference to ground? We do this for every installation to make sure there is no dead short or electrical "leakage" to ground or to the metal roofing.

Are you near high voltage power lines and could your metal roof be acting like an antenna? Again, making sure the solar array frame and metal roof are grounded to an earth ground would keep this from happening. Does your solar array have lightning arresters installed? These can fail after a severe lightning storm and may allow electrical path to the metal roof since they are wired to both the positive, negative, and ground wires. These are also easy to dis-connect and check for shorts.

Some inverters can develop a very high frequency "hum" that can be very annoying and can act like a dog whistle that most people cannot hear. This type of high frequency noise has caused headaches in some test subjects, but I have not heard anything specific related to an inverter. This can be checked with a sound pressure meter which can be purchased at Radio Shack. It can check sound levels in many different frequencies, and I would expect you are concerned with those frequencies just above normal hearing range or ultra-low.

If these checks prove negative, then shut the system down for a few weeks and see if anything changes, otherwise, take two Bayer, and don't call me in the morning.

Hang in there,

Jeff Yago


Cross check my design

Hi Jeff,

I am impressed on your publications and answers you do give to questions on Energy problem.

It will do me good if you attend to mine own question/solution to my need.

I have the need to have a back up power for my data center active devices, servers and other equipments and in the addition to the provision of a generator I still need an Battery Power back up that will take over on emergency.

By my load evaluation on the equipments running for 12hrs per day and working for two days with out charging, an average total watt-hour per day of 49,964.57wh/d.

I have in mind of using a 48v, 200Ah battery for my battery bank. Taking this into consideration I have an average amp-hour/d of 1,040.93 Ah/d.

The sum of all the power ratings of the equipments is approximately 16KW, and I intend deploying a single 20Kw inverter with thirty 48v,200Ah battery or in other have have six 3kw inverters with six same battery for each inverter and balance-distribute the loads among them.

This is exactly what I have in mind and I want to know your view to it. Also which brand of inverter and battery will you recommend? In each situation, how long will take to charge the bank?

Thanks

Chekwube Kamah

Chekwube:

Based on your description of system capacity, this is a very large and very expensive backup power system. Any casual review of your plans with the limited information you have provided is not possible to address on a "free advice" web site.

Since just the inverter alone will cost as much as $35,000.00, not to mention thousands of dollars for batteries, I am quite sure you can spend a few thousand dollars more for the assistance of a solar system designer which you clearly will need.

If you thought you could do all this for a few hundred dollars and free design services you are going to be in for a real surprise.

Good Luck,

Jeff Yago


Cast iron/copper pipe conversion

Hi Jeff,

I'm remodeling my basement and the over head cast iron heat pipes that supply heat to the radiators are positioned low and a bit from the walls. A plumber suggested replacing them with copper pipe and lifting them closer to the ceiling and walls where they can be enclosed in a safit. My question is will a smaller copper pipe reduce the effiency of heat supplied by the radiators throughout the house? The current cast iron pipes are about 3.5 inches wide.

Thank you,

John

John:

Many of these older heating systems used very large size cast iron pipe because they did not have any hot water pumps to circulate the hot water and they operated at very low or no pressure. The large piping provided a kind of thermo-syphen effect which allowed hot water to rise and cold water to return without a pump. In this case, the large pipe size was not due to a high water flow rate. If your new system now has a circulating pump, you will not need large piping since the higher flow rates and system pressure to remove air can transfer much more heat per hour.

A 1-1/2" copper pipe has a flow rate of over 20 gallons of hot water per minute with a nominal pressure drop, which is probably more than your pump can pump. A 1" copper pipe can flow 9 gallons per minute. Except for the main headers, I would bet most of your piping run-outs to radiators are only 3/4", but this size pipe can still flow 5 GPM in each leg which will add up to the main header flow rate. Remember, a smaller pipe costs less to insulate.

Hope this helps,

Jeff Yago


Luminescent solar concentrator

Hi, Jeff,

I was wondering of you have had the time to look into this development.

It appears that it will become a real boon to back woods types. Can you make any guess as to when we might look for it to come onto the market? Next year? Five years?

Thanks for all you do!

Jim

Jim:

This specific article is referring to industrial concentrating solar collectors usually installed in large groups in dry desert locations. I am not aware of anyone using focusing pv solar modules in a residential application for the reasons discussed in this article - high cost, complex computer controlled tracking systems, and cooling systems to remove the very high heat behind these concentrators. The reason most of these systems are installed in remote dry locations is that all focusing type lenses requires a clear blue sky to operate, and will produce almost no output if sky is overcast.

At least one manufacturer is already manufacturing a tri-layer pv solar cell with each layer producing electricity from different wavelengths of light as each layer absorbs that part of the light spectrum it converts. The solar field is having lots of innovation these days, but don't expect to see something you saw in a report about a research project to turn into something sold at Sears anytime soon.

Good Luck,

Jeff Yago


Spark igniter

Hi Jeff!

We own a home which is "off grid". Rather than use a wood burning stove, I want to install propane and get a propane range. Problem is, we don't want the pilot light burning all the time, and the existing spark igniters are all electric! The easy solution is to light a match every time I want to light a burner, but I'm wondering if there isn't a way to modify (or build) a non-electric spark igniter that sparks when I turn the burner on (or that is powered by a couple of AA batteries). Got any ideas?

Jessica Laube

Jessica:

The answer depends on the brand and model of your stove. Most very basic stoves with no electronic displays or timers, will have a spark ignition system that uses little or no electricity except for the brief period the valve triggers the spark. However, we designed an off-grid solar-powered home several years ago that based on our calculations would only need the generator to run about 3 hours once a week. After completion, the generator had to run several hours every day to avoid a drained battery each night. We said this was not possible, and returned to the site with full metering equipment.

After checking every circuit, we discovered their General Electric propane gas stove used more electricity than the entire house! Since GE loves electricity, they designed their gas stove with a "glow plate" down next to the oven burner which glows cherry red the ENTIRE time the oven is operating! Needless to say, we sent this stove back and had the homeowner purchase a non-electric model.

I would not try and modify your gas stove. Check to see how much electric ignition and controls draw when off, and then when energizing the spark ignition. If this is too much, then dis-connect and light with a match. This way there is no pilot light wasting gas.

Good luck!

Jeff Yago


Engine-driven generator

Can I hook up a engine driven generator to the grid in a net metering arrangement? Can I do this with an AC generator head? Can I do this with a DC generator head? How would I go about it and what equipment would I need?

Thanks.

Alexander Lapatka

Alexander:

If your state allows net metering then you can do this, but I do not know why you would want to. By every measurement I have seen, you cannot generate electricity with a generator cheaper than what you are paying the utility for power. The only way this might work out would be if the utility has very high rates and you ran the generator on waste methane gas from a large refuse pile or other source of free gas. Still, the wear and tear on the generator and replacement cost usually still makes this not a very good economic process.

If you do try this, most utilities will NOT under any circumstances allow a direct connect between your generator and the grid. You must separate with a power inverter that has been tested and approved for grid inter-connect. Without this separation the grid power will blow out your generators windings if the grid is energized, and if you did try this during a power outage, the 240 VAC backfeed from your generator will go through the utility line transformers "backwords" and be stepped up to thousands of volts that could kill a utility worker repairing the power lines down the street.

Good luck!

Jeff Yago

Jeff,

Thanks. I understand that much. I have already been in contact with the Utility Company and New Jersey DEP. I qualify for net metering. I also have a source of free or cheap fuel that I plan to burn, so that has been thought through. My question was about availability of equipment that would allow me to use an AC generator head to grid connect. Alternatively, if I use a DC generator head, can I simply hook it up to the inverter the way I would do for an array of solar panels? Thanks, and I appreciate your time. I had tried getting answers from the inverter-companies, but got no-where.

Al

AL:

If you connect a fuel-driven generator to back-feed the utility grid, it is not only illegal, IT WILL BLOW UP YOUR GENERATOR!

One way you can make this work is by using an inverter certified for grid-tie application and designed to operate with a DC battery bank. The inverter serves as the "translator" between the DC battery bank and the utility grid to match the grid voltage, current, and 60 cycle wave form. The battery serves as a "buffer" . One manufacturer recently introduced a grid-tie inverter that can take the straight output from a DC wind turbine without using a battery bank, but you most likely would need to have a high voltage DC head on your generator to match the DC input required for this inverter.

In the battery-based system, the generator is separately connected through a battery charger to charge the battery bank which means you can use either a DC or AC generator depending on the battery charger. If this system will be under 8 kW, you might check into the several grid-tie inverters that are available that have connection for a generator input and include a battery charger. With the proper sizing of the generator, battery charger, and inverter, the batteries should never become discharged since you are supplying battery charging into the battery bank at the same rate the inverter is taking battery power out of the batteries at the other end.

Large utility size mega-watt co-generator plants and gas fired peaking plants do connect their generators directly into the the utility grid without first charging batteries, but they use custom designed power conditioning equipment and extensive safety equipment to prevent all of the many power and safety problems that can occur. I assume you do not have several million dollars for this equipment and do not want to spend another $100,000 for the utility permit and inspection process to allow direct inter-connection.

Check these links -

Xantrex XW System

Grid Interactive

Windy Boy 6000U

Thats all you get for free!

Jeff Yago



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Sorry. Jeff no longer answers questions online

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