Ask Jeff Yago
Solar & Energy-Related Issues
By Jeffrey Yago, P.E., CEM
Sorry. Jeff no longer answers questions online
Yago's Article on Flashlights
Dear Dave, et al
First, this is the first time I have written to you guys, but I've been a subscriber for many years and love your magazine. It's the only one I read cover to cover, and I subscribe to several. You have got the knack for putting out interesting, informative information and balanced analysis of various topics, much different from the major media parrots.
What I'm writing about is Jeff Yago's Article on flashlights (#97 BHM, 1/2-06). I have two comments and a question/suggestion. The article makes no mention of the brightness of flashlights. My prior law enforcement training tells me that a flashlight sould have at least 13,000 candlepower, or whatever that translates to in lumens, to produce the dazzle effect when shined into the eyes. That dazzle effect is the involuntary wince and close of the eyes that puts the bipedal or quadrupedal target of the light beam off balance for a few seconds, giving an advantage in self-defence situations. Maybe Mas Ayoob can give more details or insight into this factor.
Also, there was no mention of the headlights now being marketed. These handy little lights strap onto the head or hat, are available in a variety of high power zenon, halogen and LED combinations, many come with different color light options for night vision or following blood trails of wounded game, and use little battery power per hour of use. Best of all, they leave both hands free to be involved in other activities, and can easily be focused where your looking.
Now my question. Jeff's article makes it clear that the great limiter of any light is the battery life, and the need to store batteries for long term insurance that the light will work when needed. I have seen various small solar battery chargers in various sporting goods and farm equipment catalogs that are made for charging boat or other equipment batteries. Could one of these small PV units be modified to make a small, portable battery charger to charge the various AAA, AA, C and D cells that may be used for flashlights? Possible attache the PV unit to a board with the various size battery charger units attached? This would permit use of rechargable batteries, minimizing storage of large quantities of regular batteries.
Well, that's my input for now. Love your magazine, my wife and I use your information in a variety of activities here on our 15+ acres in the White Mountains of Arizona. Thanks for all you do, keep it up.
Linden, Show Low, Arizona
While I appreciate that some people might find the "dazzle effect" when shining a flashlight in someone's eyes useful in making a choice, this article was intended on finding the best flashlight for emergency use around the home. As to not discussing flashlight brightness, please refer to the Testing Results table which lists the "foot-candles" measured at a constant distance for each model tested. Brightness or foot-candle readings chage for each foot of distance, which is why I held this measurment constant for comparison between each flashlight. As a side note, a policeman was buying the Dorcy 1 watt when I purchased mine for this test, and when I asked he gave it rave reviews for use during traffic stops at night. I assume he liked its "dazzle efect".
As to using rechargable batteries, I mentioned the much shorter life you get with a rechargable battery and the problem with recharging during a power outage. Yes, you could use a solar charger, but several of the flashlights tested operated over 100 hours non-stop on 3 small AAA batteries. This represents almost 2 weeks at 8 hours per day, and with 3 extra sets of batteries this provides 2 months of emergency power in a very small, easy to store package. My goal was to keep it simple, since during a real emergency most people have more to worry about than setting up solar chargers, adapter cables, and rotating batteries every day. If you are interested in a solar battery charger, please refer to my article in the Nov/Dec 2003 issue.
I considerd including the headlight strap-on lights you mentioned as I agree they are great and I own several. However, if you find one with the same combination of LED count and battery size as one of the models tested you should get about the same operating life and brightness. Again, this article was intended to find the best flashlight for having close at hand during an un-expected power outage, and I think the two models I recommended are the best for this purpose.
If you want to convert to your terms, 1 lumen per sq.ft. equals 1 foot-candle, which is value I listed in the table.
Thanks for your comments and interest in the magazine,
Corn burning boiler stove
Do you know where I can go to find plans for a corn burning boiler stove?
I answer this at great risk, as the last time I did an article on wood stoves some "nut" emailed me for weeks claiming I was stupid (among other things!)for not discussing the benefits of a corn stove.
First, BackwoodsHome had an article on corn stoves in back issue#42 which you may still be able to find. Basically, teh construction of a corn stove is similiar to a pellet stove, and there are some pellet stoves that can also burn corn, but both would take some skill to build due to the fuel feed system.
There is even a corn stove discussion group, but they do not provide any plans even with that group. More and more corn stove dealers and manufacturers are finding their way into the marketplace these days, and you should be able to find a fairly cheap one. We may get some information from other readers after this posting.
Battery charging...to cycle or not to cycle?
I'm a college student at an upstate NY university, and i just had a conversation with my dad. We live in an alternative energy community, and our home system consists of 6 lead cell solar batteries (the tall ones). He charges his nycad and other rechargeables through a cycle, letting them run down totally and then recharging them fully. I say that this technique is also applicable to our solar batteries, but he says it is different with lead cell batteries, and doing that will cause sedimentation. We keep our bank at around 13, and charge it with a generator when the sun does not shine (long winters in Upstate NY). what is your opinion on this, is it better to keep them at a constant level, say 13 or to allow for them to discharge to a lower level and cycle them?
Thanks for your time.
Michael V. Marcinkowski
The answer is-------
First, your dad is correct . A lead-acid battery would soon be destroyed if it was cycled from full charge to full dischaged more than a few times. A Ni-Cad battery has a "memory" problem and when re-charged it will only goes back to the charge state it was before being charged. That is why you would fully discharge a N-Cad battery before starting the re-charge process. A lead-acid battery does not have this problem, and if you take 20% out, you can put 30% back in (not counting the charger efficency losses).
Really good quality deep cycle lead-acid batteries with heavy plates are designed to cycle each day from full charge to about 40% discharged (60% charge remaining). When the battery is left in a less than fully charged state for a period of time, lead sulfates build up on the plates and "insulate" the lead from the acid which reduces the plate area exposed to the acid, which reduces the battery capacity. Heavy charging can free these deposits which then fall to the bottom of the battery. If this continues, this sediment can reach the bottom of the lead plates and short out the battery.
You can occasionally discharge deep cycle batteries to very low levels, but when you start taking them below 50% each day you can shorten their life by half or more. A 12 volt deep cycle battery is actually 70% discharged if a voltmeter reads 12.0 volts, and 75% charged at 12.4 volts. It is 100% fully charged when the voltmeter reads 12.7 volts. If your dad keeps his at 13 volts all the time, I am surprised that he does not have lots of "out-gassing" and a high water loss, as this is a very high state of charge voltage. Perhaps he is referring to his charger setpoint which shuts off as soon as the batteries reach 13 volts.
Hope this helps, now stop arguing with your dad and go study!
A starter Solar System
I'm interested in learning/building/using a solar powered electric system. A starter system... perhaps a couple of batteries, a couple of solar panels and a suitable inverter. Something I can learn with and teach the children and neighbors with. Something that would be useful. Maybe run the small blower in my wood stove overnight, or make a pot of coffee, or power some lights or the refrigerator for a hour or two.. Not a toy, but not more than $2000.00 either. When I go to the web to look for information on solar panels, inverters and batteries, I'm overwhelmed. I have have no idea what to buy. Can you suggest a configuration for such a starter system and suggest some vendors who may offer such a packaged kit?
I live in Williamsburg, Virginia.
John L Hollis
Hello to a fellow Virginian!
Check the back issues of BackwoodsHome Magazine as I have written many articles for basic solar power applications.
ISSUE #73 - Emergency Solar Power for $950.00
ISSUE #83 - Battery Powered Retreat
ISSUE #87 - Solar Power 101 - Part 1
ISSUE #88 - Solar Power 101 - Part 2
ISSUE #89 - Solar Power 101 - Part 3
ISSUE #92 - Solar Powered Light
As far as costs, I receive many calls each day from people saying they just want a basic system to "experiment" with. To me, that is like calling up a NAPA dealer to buy a few car parts to "experiment" with. The solar hardware you are seeing is designed to provide very reliable electrical power for people living where grid power is not available, or they need a quality back-up power system. It is expensive because it is built to be very reliable, and most solar modules carry a 25 year warranty. Inverters from companies like Trace (Xantrex), Heart (Xantrex), Outback, Fronius, and Sunny Boy cost thousands of dollars because these companies know their equipment must be 99.99% reliable and in many cases, lives could be at risk and expensive medicines can be lost in remote areas if they fail.
I suggest if you are really wanting to do something with solar power but are on a budget, buy a good quality inverter and only a few solar modules to start, then add more solar modules later to increase system capacity which can be easily added to what you already have. If this is still too expensive and you really only want something to show the kids, check out a RadioShack store for some of their solar toys.
I just happened to be going through your site and decided to write you. My question is this. I want all my electrical plugs in my trailer to work when I'm on battery power. What can I do?
It would be nice to have a fan on at night but when on battery, my electrical socket doesn't work. Only when I turn on the generator do I get power. I'd like to plug in my trailer to a converter or inverter, don't know the difference, and have all my plugs work on battery.
Thank you for your time.
Astorville, Ontario Canada
First some basics. Your RV has a "converter" which converts the 120 volt AC coming into your RV from a generator or the park power plug into 12 volts DC to charge the RV batteries which powers all DC lights, the water pump, a DC television or radio, and maybe your heater blower fan depending on RV.
You probably do not have an "inverter" which goes the other way and converts 12 volts DC from your on board batteries into 120 volt AC to power small appliances or standard household lights. Most RV batteries are not large enough to power a typical inverter very long under large loads. For example, you could not power your air conditioner or microwave, but you could power a TV, computer, and a few lights.
I have a satallete system on my RV that provides both television and high speed internet for my laptop computer. Since this system and the laptop do not use much power, I wired a second outlet behind the computer desk that is powered directly from an small 800 watt inverter I mounted next to my RV batteries. All the electronics are plugged into the same outlet strip, and when we are on park or generator power I leave this outlet strip plugged into one of the the trailer's standard AC wall outlet. When we are on our own and no generator or park power, I move this outlet strip plug from the standard outlet to my inverter wired outlet next to it. (different color to keep straight!)
You would need about 4 to 6 six volt golf cart batteries (very heavy) and a 2 to 3 kW inverter to power all your appliance outlets, lights, and microwave, so I suggest you keep it simple and use a small 800 watt inverter (size of cigar box) powered from your existing RV batteries, and only power one outlet (new). If you want to watch TV or use the computer system, you have enough power from this small inverter and batteries for several hours, but anything more is not very cost effective when you have a generator that has much more power at less cost and much less weight.
Hope this helps,
Alternative energy insurance
I have been thinking about installing a small home windmill and or solar batteries for home energy use and before I set off any red flags and get nonrenewed with my insurance, I was wondering if home owners insurance will cover these items?
Have you had any experience with this? any comments or suggestions, research would be appreciated.
P. Allen Myers
The answer depends on where you live and your insurance carrier. In states like Florida and California where solar and wind power is very common this is usually not a problem. Also, regardless of your location, some insurnace carriers have had experience with other solar homeowners before you and they have a good comfort level.
I have also heard of insurance carriers that did not have a clue and had little or no desire to break new ground, in which case you are going to have a problem. The only way you will know for sure is to ask. I think if you include several photos that explain what you are installing and have copies of any permits that were issued by code officials you will have an easier time of it.
Gravity-fed outdoor solar shower
Do you have ideas for this type of project? I am a carpenter and will build the structure out of wood. I also have a mostly sunny location, and I will haul the water. I need the tank, possibly to be installed on the roof of the shower, and a spring loaded valve with chain pull to get warm water to shower head.
You are are really going back in history! All over Florida and the west coast during the 1930,s there were commercial solar hot water systems being installed where there was no natural gas available and most homes had very limited electrical power (if any!). Most systems started with a cut a hole in the roof and then dropping in a galvanized tank. Since it was tall and needed to be at a high point for the thermo-syphen system to work (no pumps), the tank stuck up above the roof peak a few feet. They would stuff rock wool insulation around it and then build a wooden box that was covered with fake brick to look like a chimney!
Since there was no pump, they mounted 2 solar hot water panels at the roof eve which was several feet lower than the storage tank above at the roof peak. The solar panels consisted of piping soldered to a metal backing, with a wooden frame and a layer of glass over the front. Each was about 18 sq.feet of solar area which will heat about 60 gallons of hot water per day.
The sun would heat up the water in the solar panels which caused the hotter water to rise up the pipe into the upper part of the tank. The colder water in the bottom of the tank was then drawn down into the return piping manafold along the bottom of each solar panel. A check valve kept the system from working backwords at night. Cold water was pumped from a sistern or well by a hand pump up into the tank if city water was not available, and hot water was piped off near the top of the tank.
If you decide to build your own solar panels, remember it can get over 250 degrees inside on a sunny day if there is no water flowing through the interior piping to carry away the heat. This means your selection of wood and insulating materials need to be types that will not "out-gass" and "fog" the inside of the glass or fall apart from the heat which are common problems with cheaper materials.
Most "do-it-yourself" solar modules are designed around a glass storm door which is a very cheap way to get an 18 sq.ft. piece of tempered glass! That is why most solar hot water panels are still made with the odd dimensions of 35" wide and slightly over 6 feet in length, and not some common construction dimension based on 2 feet or 4 feet! I suggest you get a replacement glass for a storm door and build your own frame.
There is another home-made solar hot water heater design called a "batch" heater. These are easy to make and consist of a bare galvanized hot water tank (no insulation or outer shell) which is painted black and mounted longways in an insulated wooden box with a glass front. SInce everything is in the box, there are no pumps, valves, or piping from the tank to separate solar panels. You can mount this on a roof or on the ground. There are many plans on the internet for these types of home-made solar water heaters.
Home power questions
Over the years we have given much thought to providing our own energy off the grid. Living in Vermont, we don't have an abundance of sunshine or warm weather, so relying on the typical solar, wind, or hydro power is a bit scary. Ideally we'd like to have some system that is consistent regardless of weather and climate; and we'd also like to generate enough energy (no storage batteries; and sell back what we don't use). So I have several questions that I hope you can answer, or provide some links to further our research.
1. About 10 years ago I started researching geothermal closed loop ground source heat pump systems and found several that claimed a coefficient of performance (COP) greater than 1 since the system obtains energy from the earth. With a high COP, I would think that these systems could be reworked by installing a turbine in the cycle (in place of the heat exchanger) in order to generate electricity instead of heat. Some of the electricity would be used to keep the unit running, the rest for the house electric. I spoke with one company at that time (United States Power Corporation from Allentown PA) about this idea and they claimed to already have some patents in this area. They were in the process of moving south, so I�m not sure what became of them. Anyway, do you think this is feasible, and do you know of any company working at something like this?
2. Another thought is to install many very small windmills in our yard and link them all together (cheap replaceable units requiring minimal support structures). Could a group of pinwheel, propeller, or vertical devices similar to toys we had as kids, coupled with bicycle sized generators be a feasible solution? Anyone working on small windmills like this?
3. We are looking to replace our roof asphalt shingles and have seen some ads for solar shingles. Can you provide any info or links on this technology? We have no attic, so we might need some type of shingle that interconnects rather than ones that requiring drilling multiple holes thru the roof plywood for running wires.
4. Last question. I see lots of articles and ads for free energy devices and inventions using magnets, nails in trees, and other interesting technology. Do you know of any that really exist, or look promising for generating home power?
Thats a lot of questions! First, its hard to tell what direction you want to go, because at first you said you wanted to provide your own energy off the grid, but then you said you did not want batteries and you wanted to sell back what power you don't use. Sorry, but you can't have it both ways. Any alternative energy system (Solar, wind, hydro) either must have a battery bank to store excess power and to provide power for those hours the system receives no input, or it must be connected to the local utility grid which serves as the "battery".
Yes, a ground source heat pump with a high COP will provide much more energy savings than a straight air source heat pump. However, the system you described to turn a turbine is what we engineers call trying to grab your own ankles and lifting yourself off the ground! Think about it - all the ground source heat pump is doing is using a motor driven pump to circulate water from a closed heat exchanger in the unit through the piping loop under the ground to be warmed a few degrees (in the winter) or cooled a few degrees (in the summer). To expect this to turn a turbine which then turns a generator to generate electrical power is no more practical than putting the turbine under your kitchen faucet and expecting that to generate power. There is a Sterling Cycle engine that can be powered by heat, but this requires lots of heat like a burner, not 50 degree water from the ground.
You may be able to utalize a wind turbine in your area for power, but you will need a tower since most of the wind speeds required to generate any usable power are 35 or more feet above ground (unless you live on a cliff!)
There are a few firms selling solar roofing, but I have found that roofs make the best roofs, and solar molules make the best solar modules. There is a solar module made from a flexible material that can be bonded to metal roofing that seems to work fairly well, but there is always the problem of wiring inter-connects.
Finally, as for your questions related to free energy from magnets, nails in trees, and other "interesting technology" I have a bridge in Brooklyn you might be interested in buying. Bottom line, nothing is free, especially energy, and even "free" sunlight requires many thousands of dollars in solar modules and hardware to collect. Most of the solar homes we have designed and built that could truly operate free of the utility grid required a minimum of $50,000 in the solar hardware. You want a guaranteed way to save lots of energy - replace all your lightbulbs with compact fluorescents!
Grid tie inverters during power failures
Can any of the grid tie inverters - those with no batteries - power the house circuits (or some of them) from the solar panel array during a grid power loss? Or do they all shut down completely when the grid fails?
In order to obtain a UL or similiar code approval for an electrical device, any inverter designed to send power into the local electric grid is tested to meet very strict guidelines proving they will NOT send any power back during a power outage. The IEEE code body also provides these testing guidelines for grid-tie inverters. During a power outage, if the 120 or 240 volt output from an inverter energized the feed from your house to the power pole, this would "reverse flow" through any step-down transformer resulting in a very high voltage going out over the power lines in your area. Although power linemen ground all lines before working on any line, they do not normally expect a downed line to be energized in the reverse direction which could be a danger.
Inverters are also tested to prevent "Islanding", which is when you have several homes next door to each other with solar powered inverters which could "see" the voltage output from one inverter going out on the same local power lines during an outage and "think" the grid was still operational and try to also energize the line.
Not only are grid-tie inverters prevented from operating during a power outage by design (see above), but any inverter needs a battery or the grid as a "reference" to stabalize their voltage output. If you could over-ride these safety features, the output voltage from the inverter would be very unstable with rapid changes as the solar array output changes.
Bottom line, any inverter based system that operates during a power outage will require a battery bank, regardless of the size of the solar array, and the inverter output will be directed only to the home loads using the battery between the inverter and the solar array.
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