Alternative energy advice from Ask Jeff Yago. Volume #27

Ask Jeff Yago
Solar & Energy-Related Issues

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

Sorry. Jeff no longer answers questions online

LED Lighting


I read the article on LED lighting in the most recent Backwoods Home magazine and I have a couple of questions for Mr. Yago:

Do these lights have mercury in them, and if so, how can these lights be disposed of properly so they do not adversley affect the environment? And, what about the radiation that these lights emit? I have read many times that the LED alarm clocks should never face directly towards one’s bed as they emit low doses of radiation. This is a real concern for me as I realize that so many of the electronic gadgets we use emit radiation and I wonder if over time we will see more cases of cancer and other illnesses due to this radiation exposure?

Thanks for a great magazine!

Lori Smith


Not to worry, there is no mercury in an Light Emitting Diode (LED) lamp, but there is mercury in Compact Fluorescent Lamps (CFL). The only radiation an LED lamp projects is light energy, no radioactive radiation like you are concerned with.

The older style clocks did have their glow-in-the-dark hands coated with a phosphorescent paint, and years ago they did use a very low radioactive type material. Since radiation travels in a straight line, turning these clocks away from you would be a good idea. However, much tighter regulations has forced most of these products to switch to non-radioactive and safer materials.

Perhaps you need one of those talking alarm clocks!

Jeff Yago

Biodiesel in Oil Furnace


I have an oil burning (#2 diesel) furnace installed in the mid “80s”. Can I use bio diesel. My tank is inside.

Jeff Yakobics


The answer is yes, under certain conditions. Straight biodiesel burns a little hotter than #2 fuel oil, and has a higher cetane rating. But biodiesel will turn to a gel before regular diesel fuels do. Biodiesel fuels also form more deposits and have more solids than diesel fuel, and require replacing filters more often. Biodiesel also has a corrosive effect on some types of rubber hoses and seals, which is why some diesel engines have problems and others do not, depending on the type of seal material used.

If you still want to do this, I suggest using a “blended” biodiesel fuel that is usually 20% biodiesel mixed with regular diesel fuel. Most suppliers also add special “solvents” that reduce this filter clogging problem. If this lower mix fuel works out you can try a higher percentage mixture of biodiesel.

Jeff Yago

Efficient Water Heater

Dear Jeff,

I built my home about 23 years ago, and the original water heater is still in operation. It is a 30 gallon Rheem (natural gas). What would you suggest when I have to replace it. I would like to go as energy efficient as possible and still us gas. Thanks for all of the information you share with us.

Lee Wilkerson


After 23 years, its way past time to change that water heater!

Since your water was manufactured there have been major improvements in water heater construction, insulating materials, burner efficiency, and government efficiency regulations.

All appliances now have an energy usage tag and I would only consider those with the highest ratings. I do not know your hot water needs, but many have found the tankless water heater to be a good choice.

There are also several gas water heaters made with very-high efficiency combustion chambers which are easy to identify as they do not require a high-temperature metal flue since the water absorbs most of the heat from the flame before it gets exhausted. This is the type I have, but keep in mind it requires a small blower and several controls that use electricity, so they will not heat water if the power is out even though they are gas-fired.

Good Luck,

Jeff Yago

Charge controller

I have been looking into building my own wind generator from a treadmill motor and I have seen where others had built a homemade charge controller but they didn’t explain it in detail. Could you explain to me how to build a charge controller and wire everything up and maybe show some pics of this and I was wondering if a person could use an old car battery charger/jumper and convert it to a charge controller and if this will work how to do it




Sounds like you have lots of time on your hands, as a commercially made charge controller this small would most likely cost under $50. However, if you want to build your own, the link below will provide all kinds of free design information for this and other home-made solar power equipment.

Your biggest problem will be matching the RPM required by the generator to produce the right voltage and current, and the speed of the blades. You will also need to design some type of over-speed control or limiter since any wind turbine can over-speed and start slinging blades in all directions in a high wind if not protected.

Most charge controllers in cars are not designed for your needs since most control the output of a brush-less alternator which is AC, not a generator with brushes which is DC.

Heres the the link:

Good luck,

Jeff Yago

Wind Generator Heating System


Is it possible to have a supplemental electric home heating system hooked directly to a wind generator? Do these systems exist? I’m thinking a heat coil in your furnace duct or electric baseboard for example. If they exist are they practical? $50,000 for a 10 kw wind turbine system will pay a lot of gas bills.


Mike in Minnesota


Solar power and wind power are still very expensive, although utility-size mega-watt wind turbines are starting to produce power that is competitive in states with high electric rates and lots of wind. (assuming you have an extra 2 million dollars to buy one) .

This means it’s not practical to use solar electric or wind power just to heat water or space heating due to the very high loads these present and the high cost of the wind or solar systems required. However, when a residential-size wind turbine is really putting out the power and the battery is fully charged and there are no other loads operating, many wind charge controllers include an auxiliary diversion load relay that re-routes the wind power to electric heaters or an electric element in a the hot water heater. In other words, if you have no load for the solar or wind to consume, its better to divert this output then to just shut the system down.

Yes, you can still buy lots of gas for $50,000.00.

Good Luck,

Jeff Yago

PV for hot water

I am a final year b-eng building services student.

I am doing some research into PV system incorporation into building services and I have read some of your articles with interest. If possible I would would like to clarify some thoughts.

1) Would it be practical to run a PV array directly without storing the energy in batteries or inverting it to AC.

2) Would it be possible to use a system on a roof above the a toilet block where point of use water heaters are located. The system would drive a DC heating element, rated at 1.5 – 2 kW 12v.

3) At worst the system could reduce the difference between incoming and outgoing water temperature or at best provide all the required power to heat the water from ±15C° to 70C° through an instant heater. The power from one 20m2 array could power several point of use water heaters because diversity of use would ensure power demand would remain below peak.

4) Alternatively, the energy could be used to heat water in a hot water cylinder in affect a heat store. With minimal losses because power from the array goes directly to the heater element (of course circuit protection and control is necessary)

5) If my calculations are correct I should be able to heat water in a hot water cylinder with a capacity of 110 litre via a 2kW 12v DC element in just over 3.5 hours. I expect the array would span 20m2 of roof area. Higher operating voltage arrays could reduce losses further.


1) No inverter, reduced cost

2) No batteries, reduced cost and more environmentally friendly.

3) Water storage could be boosted via conventional system where necessary.


1) System usage reduced to on demand (possible life expectancy increase)

2) Payback period increased

Thank you

Mike Maher


Your calculations on energy usage may indicate to you that this will work, but you have not considered the economics. A 4 ft. X 8 ft flat plate solar hot water collector will easily heat this much water and cost around $900. A solar photovoltaic module this same size would cost over $3,000 for the same area of collection. The ONLY time we use solar pv power to heat water is with a diversion controller on a battery based solar power system for those times when the solar energy would have been lost. Otherwise, it is much cheaper to use solar thermal panels for heating and solar pv modules for non-heating type electric loads.

Anytime you cannot use solar power directly as it is generated, you will lose about 15 to 20% in the conversion process from electric energy to chemical energy, then back from chemical energy to electric energy. When you add another 5 to 10% conversion efficiency loss through the inverter and a charge controller, you end up with about 70% of the original solar energy back after storing in the batteries. This loss cannot be helped if you want to save collected solar electric energy for use later. However, heating a well insulated hot water storage tank with solar thermal heated water has much less standby losses and does not have the added energy conversion losses of a chemical battery storage system. Therefore, a direct grid tie solar power system is more efficient and lower cost than a battery based solar system to generate electrical power, but many systems still need battery storage. However, I think you will find there is a good reason solar thermal panels are still best for heating applications.

Hope this helps,

Jeff Yago

Wood fired hot water

Hi Jeff.

I have a small cabin and I want to build some kind of hot water shower fired by wood, something very simple CAn you lead me in the right direction? It is in the summer only that I will be using it.

Thank you.


All of these wood-fired small hot-water heaters are now only made in Mexico and are hard to import because they do not meet our plumbing and boiler codes. Up until a few years ago there was one small company in Eureka, California that was making these by hand and they were really well built. However, they went out of business in the US and the last I heard they were trying to set up production in Mexico.

Several companies make a small wood-fired hot-water heater to heat an outdoor hot tub and you may be able to use one of these if you can’t find a way to import the model from Mexico. There are many of these wood-fired hot water heaters used in less developed countries.

Good Luck,

Jeff Yago

Wood Burning Stove

We have a Scan wood burning stove, the pipe goes from the rear of the stove into the chimney. The only problem is that the wall is plastered and the plaster keeps cracking, have you any suggestions.

Lesley Morris


Nice stove!

You did not provide any information on your home’s age or construction, but sounds like there is enough heat radiating out the back that is heating up the plaster wall. If this is the problem, there is a concrete type 1/2″ board that has a fiberglass mesh on each side that is fireproof and used as a backing board behind tile work. This is sometimes used as an insulator to reduce the heat reaching the wall behind a fireplace.

However, if the heat loss is around your flue pipe, this may indicate your fireplace construction is not built to accommodate this type application.

Try the backing board and if this does not help you may need to talk with a fireplace builder.

Good luck,

Jeff Yago

Reflective materials for solar arrays

Hi Jeff

Has anyone tried to set up solar arrays with supporting reflective materials around them?

I am thinking of those sun blankets they used to sell in the 80s that looked like tin foil–they bounced back the sun’s rays onto bodies and increased sun exposure and accelerated tanning. Do you think a surround like this could bounce back rays onto solar panels and increase their efficiency? Do you think this sort of solar panel support system would be effective and cost efficient?

Also, rather than setting up solar panels on individual homes, is it possible to set up community solar arrays? Is there theoretically any physical or technical barrier to collecting energy in this fashion and then sending it out to various nearby home sites? I guess you would need a lot of panels as your article mentions, but as the technology improves, perhaps they could go from supplying homes with 20-30% of their power needs up to greater percentages. It may be easier to organize it this way, rather than putting the burden on each individual homeowner to finance and build their own mini solar power plant–forcing them to sport the lovely (not!) solar panels on their home roofs and deal with shadows from trees and surrounding objects. Would it be difficult to set up a solar system that supplemented and interfaced with traditional electric power for a group of nearby homes?

Thank you. Looking forward to your response


Mary Morrissey


Adding reflectors has been tried since the solar module was first invented. Several large utility-size solar power demonstration projects in the late 1970’s used reflectors on the solar modules. There are a few problems that makes this impractical on a small scale system.

If you are reflecting part of the surrounding solar energy that would be lost back onto the modules, this tends to cause much higher temperatures on the modules so you get more discolorization and shorter life since the higher the temperature, the lower the efficency of any solar electric module. They have made special very high temperature modules that have cooling coils behind them to take way the heat and they are made of materials that can take mirrored reflectors to really concentrate the solar energy onto them. However, any type of reflector, mirror, or concentrating lens requires a very clean surface and a clear sky since clouds covering the sun stops all focusing of these devices. This means the only places they work well is out in the desert with strong solar energy, no clouds, nothing to dirty up the reflectors, and a maintenance staff working full time to make adjustments, repairs, and clean the reflectors.

Yes, there have been a few attempts to do a community size solar system and I think you will see more. So far, most of these have been on islands and isolated areas where everyone was willing to live a low energy lifestyle, i.e., no air conditioning or heating appliances, and limited power requirements. There are some tax advantages for someone setting this up, but there are very high startup costs and you could only make it work in areas where regular utility power is not available at any price.

Hope this helps,

Jeff Yago

Grid Tie Solar


With all the rebates in Florida, we decided we should put in a grid tie system. We went to a local home expo already committed. When we talked to the man selling solar systems, he told us that in Florida, you cannot use your grid tied system when the grid is down. This is supposed to be a safety requirement. It seems to me, it’s just another way the power company discourages people from installing grid tied systems.

Is it true that some states, especially Florida, have this “safety” requirement? Do you really think this is a necessary safety requirement? Isn’t there some kind of safety switch used that will disconnect my solar panels from the grid when the grid is down?

It’s always sunny after a hurricane, or ice storm, when the power can be off for days or weeks. For us, one of the major benefits of such a grid tie system would be that we would have power for at least 4 to 6 hours a day even when the grid was down. That would allow us to run the well pump, the freezer, the hot water heater. Those 4 to 6 hours of electricity would make life a lot more bearable while the grid was down.


Allyn Uptain


Funny you ask. I just had an article on this subject in a solar trade magazine but it is for those in the business and I doubt you can find it at a book store.

Yes, all grid-tie systems shut down when the grid fails but this is not a utility scheme, it is required by the design of all grid-tie inverters. The only way the grid-tie inverter can sell solar power back into the utility grid is to match the grid’s sinewave and voltage and cycles perfectly. If any of these do not match, there will be no flow out to the grid. This means the inverter is constantly taking these measurments which it uses to make this perfect match and cause the flow from the solar power back out to the grid.

However, almost all battery-based inverters designed to also sell power back to the grid first put the solar energy into the battery bank, then this stored battery energy is converted to grid power and sent out on the grid. In otherwords, battery based inverters have no problem providing power to your emergency loads when the grid fails, but this means you will need a large battery bank, a room for these batteries, and a higher cost inverter.

I have found that many of the newer solar dealers just entering the solar business have never installed a battery based solar system as they are harder to design, harder to install, and cost much more so they have very few people interested in buying this type system.

Those of us who have been installing solar systems for years have no problem installing battery systems because at one time NONE of these solar systems sold power to the utility grid and they all had batteries. I recently had a client tell me another solar dealer told them the manufacturer would void the warranty if they installed a battery based system. Keep in mind both systems use the same size and type solar modules. The only difference is a grid tie system will wire 10 to 12 modules in series and use a high voltage DC inverter which allows using smaller wire to connect the array. A battery based system will have the solar array wired for 24, 48, or 60 volts DC to match the battery bank voltage. This requires a different wiring arrangement but can use the exact same module.

Hope this helps. Time to find another installer.

Jeff Yago

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