Ask Jeff Yago
Solar & Energy-Related Issues
By Jeffrey Yago, P.E., CEM
I'd like to set up a solar system for my existing well. I have a deep well, 104ft., have a one-horse power Stay-rite pump, 220AC. What do I need to run my well independently (batteries, panels, inverter, etc.)?
A well pump can require up to 2 times its normal run amp draw just to start. The normal run time load of a pump is about 0.9 kW per horsepower, or 900 watts for your well. However, I can assure you that even the most robust battery inverter would have a very hard time starting a 1 HP pump unless it was at least 3.6 kW in size. To supply an inverter this size would require about 8 size L-16 batteries. Since you only have a few hours of full sun each day, your solar array would need to be 900 watts in size to run your pump 2 or 3 hours each day. For double the run hours you would need double the array. A battery based solar system today runs about $12 to $14 per watt in these smaller sizes, which means your system will cost a minimum of $11,000 to $14,000, and I would not be surprised if it even costs more.
Now that you have fallen on the floor in shock, you can see why we do not design these larger capacity systems just to power one load like a well pump. If you have to install all this just to run a pump a few minutes each day, why not keep the same batteries and inverter and power all your lights and appliances the rest of the day? At most you may only need to add a few more solar modules.
Since you most likely will not pay $14,000 or more to power a well pump the few times each year the power is out, if you really want a backup system, buy a $600 generator, which should easily run this size pump. The only other suggestion I have is do what we did at my home and put 2 well pumps down the well. One is a 120 VAC pump which runs most of the time from the grid, and a 24 VDC pump closer to the surface which only runs when the grid is down or our inverter is out to lunch. The DC pump has a much smaller flow rate, but it can plug along all day pumping about 2 GPM directly from a 150 watt solar panel without any batteries or inverters. When the sun is shining it can pump and fill a storage tank, when the sun goes down the pump stops but you have a large tank of water. At 2 GPM, this can almost fill a 1000 gallon tank in one afternoon.
Hope this helps,
So I've checked the local library and done some surfing and I find very little about home generated methane gas production. I have 6 horses so I have lots of raw material. Any thoughts or suggestions?
Christopher W. Spear
Although you have a good idea, I am not sure if you have enough animals to make it worthwhile. You need to buy or build a biogas digester. Here are some plans for these and some links to more information,
Earth Sheltered Homes
My wife and I are very interested in building an earth sheltered home but don't have any real first-hand information that is un-biased. Do you have any current resources or information.
T. E. Durham
Underground construction has a few more design challenges than conventional construction, but knowing the do's and don'ts will keep you out of trouble. I have found the most problem with my clients living in underground homes is high humidity. The cool walls and cooler temperatures inside can really increase dampness if you are in a humid area.
Here are two low cost books to get you started:
Used forklift batteries for solar powered home
I have heard you could use forklift batteries for power in a solar powered system. Have you written anything on this or would you recommend it.
It depends on their condition and age. An electric fork truck battery makes a great battery for a solar and backup inverter power system if they are in good condition. In fact, most "solar" batteries are the same type and size battery as sold for battery powered fork trucks and floor scrubbers, they just place a "Solar" decal on them. These batteries have very heavy construction, very think plates, lots of space for liquid to avoid constant watering, and will take a very heavy charge and re-charge cycle each day.
The down side is most used industrial batteries are really really used and there is not much life left in them which requires far more energy to re-charge. There are a few large plants that replace all their batteries on a fixed schedule and some sold as surplus have been used very little. Check the manufacturing date stamped somewhere on the case.
Solar heater tanks
Hello Mr. Yago,
I have been a subscriber for several years and I am now ready to put in a solar heater for my home.
I would like to know if I can use regular electric water heater tanks for my system safely, in a batch heater system? I am looking to put in three 80 to 120 gallon tanks, will they work okay if they are in good condition or should I go with pre-made solar tanks? I do not believe that I will have a problem with piping everything in with electric type of tanks if they will hold up.
Thank you for all of your helpful knowledge and information that you put out and thank you ahead of time if you get around to this mail. I realize you are busy.
Many people do make solar batch heaters out of used electric hot water tanks. Of course any used pressure vessel has a higher risk of failure and you must make sure you have code-listed temperature relief valves and pressure relief valves, and that they are properly sized for each tank.
The downside of using these used electric tanks is they are "glass" lined and most solar hot water tanks are "stone" lined. You want to store the solar hot water as hot as possible and a glass lined tank is more likely to crack at these higher temperatures which is why solar tanks use a heavier and higher temperature rated lining.
I have gone to fairly good lengths to get to you…Mother Earth Magazine, Backwoodssolar, and finally Backwoods Home magazines.
I am trying to get the info together to build a much smaller trailer than your 6’ X 12’ that you describe in your article. What I had in mind is something that could power, let’s say, a RV-sized refrigerator or refrigerator/freezer combo via 12 volt, or 110 /120 volt using a small bank of batteries, a small solar array, and very likely a small generator….gasoline or propane-powered.
It is my intent to use this trailer for fairly remote camping, and it must be small enough to go over fairly narrow trails, and being light and small enough to be pulled by a 4-wheel drive ATV.
I have not gone through the thought process far enough to determine if this trailer needs to be dedicated to the energy aspect along, OR could the trailer also double as a trailer for all of the various and sundry camping gear that we all want, such as: tents, ice chests, folding chairs, etc., etc.
If I could find a ‘recipe’ that would include sizing, wiring, and other ‘engineering’ issues, and WHERE to buy these pieces of hardware. Well, that is my goal.
Can you / will you help?
I appreciate anything you can do.
You should be able to do this without any problem. The trailer could be only 2 or 3 feet high with access doors on each side and back. Several doors could access the batteries and solar hardware, others could be tent storage and camping supplies. The solar array could lay flat on the top and could fold out when you get where you are going. Pick the trailer size and type that works best for your other needs and adapt for the solar equipment.
If you plan to actually provide much solar power, you will still need a solar system at least close to the size of solar array, batteries, and hardware that I used in the article, but you can cut down the trailer height and width as needed.
Solar power for hot water and dryer
I am trying to find information about how to run my electric dryer and hot water heater off of solar power. What I can't find is information about using my current dryer and water heater off of batteries charged by solar panels. If that is even possible. I have a family of seven and am trying to cut down on my electric bill. Any advice you have will be greatly appreciated.
Sounds like you need more than a solar power system to provide energy!
Forget the solar power for your dryer, it would cost many thousands of dollars.
However, a solar hot water heater has a much lower installed cost and with a large hot water tank could pay for itself in only a few years.
How can I convert truck to solar power?
I have a 1997 Nissan 4-cylinder truck and want to convert it to a solar power truck.
How do I do it?
This is a good truck to convert as it is small, light weight, but sturdy and has room for batteries. There are several firms making conversion kits. You will need a battery bank which will be located in the truck bed, an electric traction motor and adapter plate that matches your transmission, and a battery motor controller which will regulate the motor RPM based on a signal from a foot pedal. These new systems do not use resistors to control motor speed as this wastes battery energy, but they are expensive. You can buy a conversion kit for your specific truck, check out these web sites:
I'm building a new home on a 35ft high bluff overlooking Cook Inlet. We have a healthy amount of wind, and I would like to generate some of my electricity requirements with a wind turbine. I was thinking in the 3-5kw range. The 2 names up here most often used are Kestrel and Skystream. Are those my best options or do you recommend another brand?
Sounds like a wind turbine will work really well at your location. However, larger models like you are looking for will require a very tall and very heavy tower. Also, servicing a wind turbine on top of a 75 foot tower is not for the meek.
If you do not want to install this heavy tower, perhaps you might consider installing two (2) smaller wind turbines which can be "tilt-up" type towers. They may be just as tall, but can be raised and lowered without climbing.
I have on client with two 500 watt wind turbines on his farm house, and another client that has two 1,500 watt turbines on his greenhouse, both trying to avoid a major steel structure standing near their home.
Otherwise, for a larger system you will need a regular installer with a very tall crane, and have some type of service contract.
That sounds like a good solution. And I like the idea of a tilt up tower. How far can I go with 24V from my house where I need the power and how do I best convert the 24V into 240V AC?
If you have to run DC wiring very far, you want to have it as high a voltage as possible. If this will be a battery based system, you would want a 48 volt DC system, and keep the wire run under 200 feet or you will need a really expensive and large size copper cable.
You use a DC to AC inverter. Check out Outback and Xantrex brands. Most are 120 volt AC output, so for 240 volt AC you will need two identical units or a 120 to 240 volt transformer.
Battery company investment
If you were to invest in the future on a battery company would you have any recommendations to give to my broker. I feel batteries are on the horizon for our economy. Can you give me any feedback.
Thank you for your help.
Well my broker is E.F. Hutton, and E.F. Hutton says...
I assure you that you do not want me giving advice to any stock broker. However, if you are interested in investing in battery manufacturers in general, I can give you my experience with several firms. For a low investment risk I would think staying with an old-line long-term firm would be the safest. Unfortunately, I expect the next breakthrough battery technology may come from some guy working in his garage!
Trojan, Rolls, Concord, and Decca are very well established battery firms making many of the deep cycle batteries currently sold for solar power and alternative vehicles.
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