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Archive for December, 2008
Wednesday, December 31st, 2008
I have a fireplace in my basement and wood like to augment my propane/hydronic heating system with a wood stove fireplace insert similar to your setup. My question is about the water jacket that you use. Is it off the shelf product? Custom? Can you provide insight into the set-up that you did not detail. Your expertise would be appreciated!
This is another great example of class action lawsuits forcing great products off the market.
Throughout the 1970′s energy crisis there were several nationally sold fireplace inserts and fireplace grates that heated water. This made it easy to pipe all the wood heat to hydronic baseboard heaters in other parts of the house, or to a hot water coil in the ductwork and heat the return air being ducted to the other rooms without operating the electric strip heaters or gas burners. I purchased several of these “Hydro-Heaters” for other projects, including the one I now have in our solar home. I had it the new unit boxed up and put in storage for almost 15 years, then installed it in 1992, and it has worked perfectly for the past 16 years.
There also was a firm in northern California I visited in the late 1990′s that was making a great wood-fired hot water heater for remote home-sites. It looked like a standard gas hot water heater, but the bottom half was a fire-box and the flue went up the center. You built a small wood fire and waited about 30 minutes, then you had enough hot water for several showers and dish-washing. They made a “tank-less” version that was just a fire-box surrounded by a water jacket, and you pumped the heated water to a larger storage tank or hot tub. I also purchased one of each and am still keeping them for future since this firm is now out of business and to my knowledge was the last company still making these in the US.
What happened was most state and federal agencies viewed these products the same as a steam boiler since they can explode if not properly installed. For example, all of the models that were sold in the 1970′s always came with a temperature relief valve and a pressure relief valve. If you have a large fire going and the water pump stopped pumping when the power went out, without any water flow the water jacket would quickly turn all water still left in the heater to steam. I have witnessed several times when this happened and all the only thing you saw was some some steam safely venting to a floor drain or outside. However, if the relief valves were not properly installed, the pressure could reach a level that would rupture the steel jacket or under extreme cases even explode. There were not only cases of tank ruptures due to missing relief valves, but even a few cases where a relief valve was piped to the outside and a small drip through the valve due to a weak spring would run down the pipe and freeze during winter weather. After several days the relief valve’s discharge pipe would totally plug up with ice, then if the pressure increased due to a power outage stopping the pump there was no place for the pressure to vent.
I know that there are millions of these wood fired hot water heaters and hydronic fireplace grates being sold in third world countries every year, and I think the California manufacturer moved his operation to Mexico years ago, but I am not aware of anyone making a hydronic fireplace insert that is legal today. If any reader out there can provide this information we all would be grateful, but I think the cost to get these UL listed and the cost for liability insurance for any manufacturer makes this impossible today.
If you really want to heat your home with wood using a hydronic system, I suggest installing one of the many outdoor packaged units you see advertised in Backwoods Home, and in an article I provided on this subject. Since these outdoor units use a non-pressurized water jacket system to pipe hot water to heat the home, they are safe and easy to install.
Tuesday, December 30th, 2008
I am building a 6 soccer field complex on a 26.77 acre lot. There is a well on the property; not sure what it pumps.
I am keen on keeping this a natural facility and happened to come across the Solar panel discussion.
Without going too deep, as I am not a technical person, would Soalr panel energy work for 1) Bathrooms, 2) Watering the sports fields?
Thank you in advance
It depends on where you live and if utility power is close by and easy to connect. If you are in a state that offers solar incentives, this can really reduce the cost for any alternative energy system. If you are not near a utility line, they may charge a very high fee to run power to a remote location. Having addressed these first, here are the solar suggestions:
1. A solar hot water system can easily provide hot water for your bathrooms and any snack bar type sink. Since your afternoon or early evening usage matches the solar afternoon peak and stored up solar heated water, you most likely would need little or no backup hot water heater.
2. It is not feasible to power any heating equipment from a small solar system, so if this location is subject to freezing weather you would either need to drain down any piping that could freeze or have heating equipment powered by the electric grid, natural gas if available, or oil/propane equipment.
3. If your only load was a well pump for ground watering you could easily install a pole mounted solar array and solar DC well pump which would provide water when the sun was shining and no pumping when the sun goes down. If you have local utility power, you will find it may be less costly to stay with a standard well pump and no solar.
4. There are a few grants for non-profits to help pay for demonstration solar projects and you may be able to find one to offset most of this cost, but I am not aware of anything for private or commercial applications.
Hope this helps, now play ball !
Monday, December 29th, 2008
For the past couple of years I’ve been scouring the local Craigslist for used PV panels in preparation for my ultimate plan to move off-grid. I have been very fortunate in that I have amassed approx. 1.3 (rated)Kw of 12v nominal panels for an average of just about $3/watt. I realize that when dealing with this much rated capability it is normally recommended to up-size to a 24 or 48v system, but to keep things as simple as possible (KISS) I’m planning on sticking with 12v.
The drawback to this is that they are a mish-mash of manufacturers, sizes, and specifications (which also makes it difficult to wire in series for higher voltages). My primary concern lies in the fact that the open circuit voltages range from around 17v up to over 21v. It is my understanding that (in layman’s terms) voltage is roughly equated to ‘line pressure’.
With this in mind I’m wondering if the panels with a higher voltage specification would generate a ‘back pressure’, as it were, preventing the panels with a lower voltage specification from adding to the overall current (kind of like a garden hose trying to augment the flow of a fire hose). I asked an engineer friend of mine who’s been living off grid for almost 20 years now, and even he was stumped.
You did not say how many modules you have, but with a total of 1300 watts and all are nominal 12 volt, I assume we are talking about 22 to 26 modules. With your desire to keep everything at a nominal 12 volts, this means you will have all 22 to 26 modules wired in parallel, and that is not good. There are many reasons why this is not practical, but the big one is the UL label on the back that says the size of a series fuse required. For example, a typical module in this size range will probably be listed as requiring a 15 amp “series” fuse. If the modules have an average output of 5 amps, this means if you have more than 3 modules in parallel, it is possible for one module to have an internal “short” and all the current from the other 3 modules will be routed through this failed module and could cause a fire.
To reduce the number of parallel modules, I would set this up for 24 or 48 volts nominal. This means the modules will be wired in “groups” of 2 or 4 in series. Even with identical modules with the same model number you can have as much as a 10% difference from one module to the next, so you want to “match” the strings. Lay them all out where they receive the same amount of sun at the same time, then go down the line on a clear day and mark on the back what voltage each is producing. Next, using a meter that can read DC amps, short the positive and negative leads through the amp meter and also note this reading. You need to be fast as any change in sky conditions will throw off your readings.
Now try and “match” high and low modules in the same string so each separate string has the same voltage and amperage. The problem is not in having slightly different voltage modules in series, the problem is avoiding having multiple strings in parallel that have far different voltages. This is the same problem as hooking up different batteries in series. You will always have one or two individual cells wired in series that are lower or higher than the others, and the battery will settle on a voltage that levels these highs and lows. But if you have batteries with different voltages wired in parallel, the higher voltage battery will try to “charge” the lower voltage battery.
You should use a good quality MPPT type charge controller which will try to sort out any remaining mis-match. If your modules are really mis-matched and it is hard to do the above, you may want to use multiple charge controllers so you will have fewer modules wired in parallel. These can still charge the same battery bank.
Sunday, December 28th, 2008
I have been reading your articles on solar power and have decided to build a small battery room in the basement, as opposed to the battery box. However I am not certain about something and would like your advice. I will put the batteries on a treated plywood on upright 2×4′s floor in this 4′ x 7′ floor area room x 8′ ceiling height.
I am planning to run a vent from the wood furnace into the room to keep it at optimal temperature for battery performance. However I am not certain about how much venting to the outside is needed and won’t the vent to the outside also cause all the heat in the room to be lost?
Is there a one way valve of some kind that will allow fumes out but no cold air in? The furnace vent will provide fresh air as I am not going to have a cold air return from this room back to the furnace because of the battery fumes getting into the house air. Currently there are 8 batteries but there may be more batteries added in the future.
Your insight and advice in this matter will be greatly appreciated and hopefully will help other readers as well.
John Mc Andrews
We do not get into detail design advice for a specific application on this web site for obvious reasons, but I will pass along the following general guidelines for building a battery room. Under no condition would I duct supply air into a battery room from a furnace, wood stove, air conditioner, or anything else that moves air. Any room, no matter how well it is sealed, is not air tight, and if you duct or blow air into any room it will find its way out, and not always out the path you intended.
I have seen a sealed battery room with a small exterior pipe to vent battery gases to the outside actually “suck” air back into the room located in the basement due to wind pressure acting on the home’s exterior wall surfaces, and this backward air flow forced hydrogen gas back into the basement. You want to always EXHAUST air at the highest point in a battery room and let the makeup air come from a louver located near the floor, under the door crack, or anywhere else it can find a path, but the room should be under a negative pressure (air being forced OUT of the room to the outside) in reference with the rest of the house and basement so any hydrogen gas will be exhausted to the outside and not forced back into other rooms or up through the ceiling to the floors above.
We usually use a battery-powered in-line exhaust fan installed inside a 3″ PVC pipe. These are made for battery gases and the brushless fan they use will not spark and cause a gas explosion. I would expect almost any basement under a house to not get too cold or too hot and would not expect any heating will be required. However, if you want to heat a battery room the only safe method that I am aware of is a very expensive explosion-proof electric radiant heater, or baseboard radiation around the walls that is heated by a hot water heating boiler or domestic hot water tank.
We always build a battery shelf made from pressure treated 2 x 4′s on edge with 1/2 x 4 spacers between each to allow for good draining and air flow. We place these on 8″ concrete blocks spaced every 3 or 4 feet to provide good air flow and to keep the battery bottoms from touching the much colder concrete slab floor. A floor drain is also helpful as it can get a little wet when you wash down the batteries with water and baking soda. Finally, we always add a good ABC type fire extinguisher, a vapor-proof glass “jelly jar” type light fixture, and a locking door having a warning sign.
Good Luck and don’t light a match when you are in your battery room if you can’t see!
Saturday, December 27th, 2008
Can two or more inverter outputs be connected in parallel?
Your question sure was short and to the point!
The answer is yes, you can most of the time, but there are a few electrical issues to deal with. Most high-end battery-based sine wave inverters made today have “stacking” communication links between each inverter. Since most residential-size inverters used with a battery based solar system are under 4 kW and only available in 120 volt AC, if you want 120/240 VAC you use the link which will synchronize the sinewaves of each separate inverter to provide true 120 and 240 volt AC power.
If you want to supply a load larger than 4 kW at 120 VAC, these same inverters can use the same communication “link” and their outputs are paralleled. To keep standby inverter losses low, only one inverter starts, then as the load increases the second inverter (or 3rd, or 4th) come online as needed to meet the load. You can also program multiple inverters to do both, with several staged for each leg of the 240 volt output. I would not mix and match inverters, and some lower cost inverters may “see” the output waveform of the other inverter connected to the same load panel and think the voltage or cycles are out of allowed range.
If you are doing a grid-tie system with no batteries, you can usually put as many inverters as you want in parallel with all their outputs supplying the same loads panel, but again, I would make them all the same brand as sometimes you still have some out-of-range problems that you have to adjust programming and this is easier if they are all the same size and model. Make sure each inverter has its own circuit breaker on the input and output for system service, and try and equal all wire lengths for separate array and grid connection circuits that are in parallel.
Saturday, December 27th, 2008
How can I become a CEM?
I am particularly interested in the broad area of Sustainable Energy & Refrigerants for Heating, Cooling and Refrigeration. On the Energy side I want to explore the application of Solar Systems to power residential and commercial HVACR appliances. I have been working in the HVACR industry for over 6 years and would like to acquire the specific knowledge and necessary certification in Sustainable Energy to broaden my skillset and marketability in this exciting and developing industry. If you don’t mind I would greatly appreciate your guidance on how to do this and I have the following questions for you:
1. What are the certification requirements to become a Sales Engineer/Marketer of Solar Systems?
2. Where can I access accredited training courses?
3. On completion of the required training & certification which are some of the companies that I could target for business opportunities preferably in Sales, Technical Training, Management Consulting and even starting a Small Business in sales, installations and servicing Solar Systems.
4. On the commercial Refrigeration side I have a solar concept that I would like to explore and am looking for an organization that has the facilitiy, resources and might be interested in working on developing and testing the prototypes that could be taken to a few Commercial clients that would be interested in this type of innovation.
Thanks and looking forward to hear from you.
There are two areas of interest, and both will really pick up after the new solar energy credits take effect after Dec 31, 2008.
If you are interested in Solar hot water heating it sounds like you already have a good background in this field which is more plumbing related. Skills would include all types of plumbing and piping related products for domestic hot water.
Some community trade schools offer adult classes in plumbing and electrical fields, and this may be a good place to start.
If you are interested in solar electric, then I suggest getting in with a local electrician and learning more about wiring by helping out and start studying for the state electricians license.
Regardless of which path you choose, the best certification you can earn in the solar field is to be a NABCEP certified installer, and they offer an entry level certification. This requires both testing and field experience, which you can only get by working under someone who can provide work experience.
Review the NABCEP site for more information.
Friday, December 26th, 2008
I am interested in generating electricity by burning wood. I haven’t seen much about this subject on the website. Why would burning wood be a good choice or a bad choice for generating electricity?
Any information that you could pass along would be much appreciated.
The reason you have not much about this subject is it is not very practical today. This does not mean it does not work, but 99% of these systems require a wood-fired steam boiler which could explode if not designed and operated properly, it takes constant fire management to maintain proper steam pressure, it takes a good supply of water that is properly tested and treated to reduce chemical buildup inside water tubes, it takes a daily “blow-down” of the mud drum which will fill up with sediment, it takes daily removal of ash, and it takes regular lubrication and adjustment of all the moving parts.
If you check, you will find that almost all of this equipment is refurbished equipment somebody found or saved from the 1930′s and 40′s. Many states require any steam boiler, regardless of use, to be inspected every year by the states safety inspector, and many require that you maintain liability insurance for its use. Many states require steam boilers above a specific size to be operated by a full time boiler operator, and many states require this operator to be a licensed steam plant operator.
In other words, turning firewood into steam is not as simple as you think and is not very cost effective unless you already have the equipment and have lots of time to operate and maintain all the working parts. Most of these systems today are part of a steam show or other event. At one time I had a 20 kW steam driven generator that was new WW2 surplus and it was almost 10 feet tall and weighed 4 tons. It was too big, too heavy, and too much trouble to keep operational so I finally scrapped the whole thing.
Here is a test for you. Put a very large pan on your stove full of water right out of your tap. Now boil it until all of the water has been boiled off, then see how much scale and chemical deposits remain on the sides and bottom of your pan. Now do this 24 hours per day and how long do you think it will take to totally coat the pan with deposits you can’t remove and that reduce heating efficency. Now imagine this was boiler tubing inside a steam boiler to convert water to steam to drive a steam boiler.
Good Luck and be safe!
Wednesday, December 24th, 2008
I hope this is a easy question.
I have a motor home that has 3 deep cycle 12 volt batteries.
I want to keep them charged with solar as much as possible.
Will connecting 2 or more 45 watt separate systems charge them better than just one?
As they are all the same watt I am not sure adding 2 or more same watt systems will charge any more than 1.
Att: Help Please:
I assume you mean connecting each battery to its own solar module and charger verses connecting one solar charging system to all three batteries. For good battery voltage balance, its better if you connect one solar charger to all batteries wired in parallel. I don’t know how you could do this separately unless each battery can be disconnected from the others, since normally they all are wired to the same 12 volt positive and negative mains. Assuming you could separate them from each other, as soon as you connected a battery that was at a higher charge than the others, current will flow from one to the other until they are equal in voltage.
Keep it simple,