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Archive for February, 2009
Friday, February 27th, 2009
Have noted that some distributors are selling slightly blemished solar panels. When advertised they indicate the panel meets UL/CE specs and carries the full warranty period as a normal solar panel. They also indicate the blemish will not hinder the output of the solar panel. In your years of experience are you aware if a blemished panel would have some drawbacks?
Depends on the cause of the blemish. For example, dents and scratches on the aluminum frame or backing is usually not a major concern. If one or more cells have failed and the voltage output has dropped, this could be an indication of possible further failures most likely doe to poor quality control during manufacturing.
If the modules still have a UL certification, and the seller documents they warrant the wattage at some specific level, then most likely you should be OK.
Hope this helps,
Tuesday, February 24th, 2009
I have a remote camp with no road acess so everythting needs to be taken in by boat or snowmobile. In the summer transport by boat isn’t bad but in the winter the trips for propane and kerosene are constant (25miles round trip).
My question is that I am considering a pellet stove but with no power except battery/inverter and generator, and the fact that the pellet stoves require power for the auger, blower and exhaust fan, can these be converted to DC motors more efficiently than using the inverter or am I just as well off using the battery /inverter combination and probably charging the batteries every two days instead of three to four days?
I think you will find the conversion over to DC motors is too much work and too many problems. However, the AC motors in the stove do not require the higher priced pure sinewave inverters, so you can get by with the lower cost modified sinewave inverters you see at all boat and RV outlets. Avoid the really cheap units as they are not designed to run for longer hours like your wood stove and they have a low efficiency so they will draw more battery power than the higher priced units. Also, unless you plan to also power lights and other appliances you don’t need a large inverter and will probably be able to use an inverter in the 500 watt range.
Good luck and stay warm,
Monday, February 23rd, 2009
I have a large river I would like to tap for power. I find very little information on how to set up a turbine or propeller type. River is 5 plus feet deep 40 ft wide. Average speed 5+. Plus if permits are needed on such a river, were would I get that information?
Usually its not how deep or how wide a river is that determines how good it is for making power, its how much it drops in elevation in a short distance. In other words, If I wanted to install a hydro generator, I would rather have a creek 5 feet wide and 2 feet deep that drops 30 feet in elevation while crossing my property, than a 100 foot wide river 20 feet deep that may only drop 1 or 2 feet in elevation. Yes, there are a few drag type hydro generators that you can have at the end of a cable in the middle of a river, but the real power comes from the drop in elevation. That is why they build dams!
Hope this helps and beware, most states have very strong regulations against damming up a creek or river. Unless you can find an old abandoned dam left over from when water wheels powered our industry to refurbish, odds are it will be more trouble than its worth.
Sunday, February 22nd, 2009
I love your articles on alternative energy!
I’ve been wondering something. Is there a significant difference in the quality of the PV panels and equipment from better known suppliers over the panels seen at places like Harbor Freight and Northern Tool?
Harbor Freight recently had a sale/coupon for a 45 watt panel with a few extras, such as a couple of 12vdc lights for about $180 each. I passed it up fearing the quality of the panels, as I cannot put them to use right away, and wouldn’t be able to return them down the road.
What a great question! Actually, for some reason the old adage that you get what you pay for is actually still true and surprise – it also applies to the solar industry. First we need to separate out the solar modules that were not built or intended to last 30 years. This would include the solar chargers and solar cells for portable devices and to charge car batteries, cell phones, MP3 players, ect. Typically, these will be under 10 watts in size.
The remaining solar modules that are intended to provide primary or backup power for homes, businesses, and remote telemetering sites normally carry the standard manufacturers warranty which these days is 25 years. I have solar modules on my home that were manufactured in 1980 and they are still going strong, although now sun bleached in color.
This past year there was a house fire caused by “cheap” solar modules that were built by the installer. These shorted out after a brief rain on an hot summer day, and the non-glass covering caught fire and melted down which then caused the roof to catch fire. Although I doubt that you will find semi-homemade solar modules in a store, it does show that the solar modules must be made from quality materials. The best way to find this out is look on the back label. The label should have the logo indicating the module is certified by “UL” or the Canadian equal “SA” or both.
There is a flood of solar modules now entering the US market. SUN-TECH is a very well respected China product and although I cannot say what the long term life of their modules would be, the ones I have inspected appear to be very well built. Unfortunately, there are many other made in China brands that have only been out a few months and we do not know their quality or the quality of their manufacturer. Many countries are desperate for cash right now and solar modules are the only game in town that is still selling. This means you not only might get some really great prices on some discounted quality solar modules, but also on trash modules that were cheap to start with.
If in doubt, pass it up.
Saturday, February 21st, 2009
Would these batteries work as a battery bank — Caterpillar 175-4370-pho Cat lists these as heavy duty, deep cycle, deep discharge they are 12 vdc. I can get a good price on these from the cat dealer and they weigh 62#
On using a array of PV panels, for aesthetic reasons, would like to mount in back of house. This would mean a cable run of approximately 50 feet.
For a 12vdc system what size cable should I expect to use? Same question but for 24vdc? I have access to some free cable if right size. Also is it normally multi strand or single solid conductor.
Cable from battery to inverter, approximately 5 feet run. Expected cable size?
In choosing a inverter, if I use a 12vdc supply source (pv) would the inverter have to be 12vdc input or is there one that is selectable input voltage? I expect to increase the incoming voltage as I can afford 2 or 3 more panels.
This unit will not be grid tied. It will be used for my shop, Expected maximum power usage at any one time, 1000 watts, then would drop off. I can only operate one tool at a time.
Biggest load to be expected for short bursts (3-5 minutes) 115 vac wire feed (currently grid connected) other loads is just small hand tools, circular saw, drill, saber saw , one flourescent light etc.
The 12 volt Caterpiller battery you referenced weighs 62 pounds. A 6-volt golf cart battery weighs 63 pounds. Since you would need two 6-volt batteries to provide 12 volts, this means a 12 volt battery made from golf cart batteries would weigh 126 pounds, or double the weight of the 12 volt Caterpiller battery you referenced. The heavy weight indicates more lead plates which provides more amp-hour charge capacity. If your system will not cycle every day from full to low charge, then this battery might give you good life. However, most starter batteries are designed to provide one heavy discharge during starting, then several hours of slow recharge. Solar systems do not operate this way.
As noted in many past answers to email questions, we cannot provide specific design answers like what wire size to use as there are many variables we would not know about your specific application, and we do not have the time for this level of help. Please check the most recent article I have in Backwoods Home Magazine that describes how to make an off-grid solar system for a remote cabin which will answer many of your other questions.
Friday, February 20th, 2009
We live in a small cabin and rely on deep cycle batteries to power our lights. The wood stove is going pretty much 24/7.Is there any way to make a battery charger to sit on the wood stove and make enough energy to charge one battery at a time?
I have an electric fan device that sits on top of our wood stove and the unit generates electricity from the heat to run the small fan. Unfortunately, you get only a very tiny amount of electricity from this solid state thermal energy conversion process, and all the electrical equipment must be able to withstand the high temperatures. Yes, you could get enough electricity from wood stove to do this, but the cost and size of the equipment to do it would be un-realistic. Your best bet is to spend your money on solar modules.
Thursday, February 19th, 2009
My 1928 stucco frame house has I believe no insulation in the walls. I do have blown insulation in the attic. I’ve done some research on installing expandable foam in the walls so as not to have to remove the interior plaster walls. It’s going to be expensive and the payback is about 6-7 years. Any comments on the foam issue?
Yes, older homes are a real problem to heat, but on any home the most heat loss is usually out the roof and air infiltration. Wall heat losses are far less if you can seal up all the cracks around windows, doors, wall outlets, and anywhere else the wind blows. In other words, I would first put the most money in insulation for the attic and sealing all the cracks. We did tons of computer energy modeling that showed it made sense to install thermal windows in new construction, but the high cost to retrofit them in an existing older home with many other problems was not worth the high cost.
As far as spray in foam insulation, its a great insulator, but if not done right, you can get voids if the mixture is too little, and you can blow off the siding if the mixture is too much. They also have to drill lots of holes around the exterior walls and I am not sure how well those can be patched to look good after.
Wednesday, February 18th, 2009
I enjoy your articles whenever they appear in BHM.
I have been hearing about “thin-film” voltaic cells in the press for the last few years and I think your readers would enjoy an article discussing the present state of this inovation and how long it will be before they reach the mainstream market.
Are they really going to be as cheap in comparison to the current product as the press would have us believe?
Actually I have discussed thin film solar module technology in past articles. Thin film solar modules are called amorphous cells and are one of several research attempts to lower the cost of solar modules. Unlike standard modules which are assembled from individual solar cells and then wired into a module and vacuum sealed behind tempered glass, the amorphous solar module is made by a plating process which deposits a thin film of photovoltaic material on the back of the glass or on the surface of a metal plate. A laser is then used to divide the single large cell into separate cells to increase the voltage, and this process is much faster and cheaper.
Unfortunately, although an amorphous solar module is less than half the cost of a conventional solar module, so far they are less than half the efficiency so you need to buy twice as many and use twice the roof area for the same amount of collected energy. They are also developing solar paints or inks that can be applied like spray painting a car, but these also are much lower efficiency and have a shorter life. There will, of course will, be some applications where system life and efficiency are not as important, as long as they are cheap.
There are many things in the news these days about improving solar technology and lowering costs, but so far, almost all of these articles are talking about things that are years away from being turned into real products you can buy.
Hope this helps,