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The RV energy consumption, while boon-docking, is a study within the efficient use and production of off grid power. Actually, the entire industry has maximum concerns of efficient use of energy from vehicle to living needs. This zone of study is excellent for alternative energy solutions. First, they have a large population of consumers with money in hand that desire to decrease cost and improve traveling life. They are not afraid to invest in good solutions and willing post the results. Their are many experiments on practical solar power, generation of power, battery calculations, propane comparisons, engine selection, tow vehicle performance, air drag, etc.. The savings for this group, from ability to go off grid are more pronounced as compared to home use. So, I've run many a calculation and read a ton. It is frustratingly complex with many a trade off and the solution must be compromised by your needs.

 

First, I will say, much hyperbola out there for solar. This solution is touted by the professional bloggers that attempt to maximize readership. You have to dig into their costs, benefits, and  hopefully follow up articles to dig out the truthful evaluation. Per my cost accounting training, most of solar is not a worthy way to generate all you power needs. However, just like were discovering in grid applications, solar power is best utilized as auxiliary supplemental. Withing the RV use it is best to avoid all but the simplest setups with low cost.

 

Second, high wattage generators, sized to power every possible device at the same time. No, just to heavy, expensive, an loud. The smallest Honda or Yamaha more than enough that can be moved to location to minimize noise or transported for additional needs, that will double the device usefulness. It's not max power the real concern, but minimal fuel consumption for long periods. For example, battery charging is all about low wattage and long cycles.

 

Propane should be the energy of choice for all high btu heat needs. Electric devices should be selected for minimal power draw and high efficiency. A couple exceptions would be AC, that is currently just has minimal alternatives other than grid connections. Sure, you can spend thousands to make it happen without grid power, but not a good use of your hard earned money. Buy a DC fan instead or use the smallest window shaker with the small generator power. Better yet, relocate to cooler region of country. Efficient minisplit AC technology is zeroing in on solving this problem. Lights, TV, and even DC powered refrigerators are all very useful. Propane/grid power refrigerator is the common accepted provided refrigerator, currently, within the RV industry, but high efficient DC refrigerators is the best option when that fridge dies. About 25 watts/hr for 10 cu/ft. The device will pay for itself as the traditional RV ridge will consume a $20 propane tank/month. Electric power is 10x a normal fridge and most hookups charge a premium for power.

 

It appears to me that every efficient device that must use electric power, is basically DC. We are wasting energy within the home with AC power. Were wasting energy by using electric for cooking and heating. Propane or natural gas is way cheaper and better for the environment. Refrigerators and AC appear to be equally efficient operating on DC. I can see no reason that households will eventually become powered by DC current. I think the battery car technology and adaptation will play into this as well as solar, and CHP power generators. The future household requirements will not depend on grid power, but only natural gas or propane. However, one can see a very formidable solution of ethanol fuel. Consider, the ease of use of ethanol and the very potent environmental benefit as well as low cost and simple infrastructure required. The solution works well with transportation and I do think there will be a crossover of auto and home energy solutions.

 

I can think of no better solution to both household energy needs and transportation then the following:

 

- Small auxiliary IC power plant to greatly augment battery storage needs and bring the car home upon low of power within limp mode. The power plant to be utilized for home power needs as well. The ICE utilizes ethanol fuel and high boost provided by hybrid charger/turbo or just electric. Variable boost pressure would make the engine efficient at low power needs or high power. Waste heat captured per the developing technology of vacuum bottle system. Heat to be dumped to household and the vehicle becomes an efficient CHP device for homes hot water and power needs. Efficiency of this setup above all possible power plant production systems. Factor in the costly and inefficient grid as a comparison, well, this system would just be a real winner. One must realize the power needs of an efficient home should evolve to a mere fraction of current practices. Natural gas can supplement the more efficient heat production of the automotive CHP system when needed. Remote housing may just standardize all energy needs on ethanol. Third world economies should do very well with this solution. Political and Corporate interests would fight such an inexpensive and independent of government solution. That would be the biggest hurtle.  

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How many articles have you read on the value of lithium? The superiority of choosing this battery technology. Same for AGM battery that actually is getting more popular. So, much info, but if one drains the swamp and accumulates a list of general benefits, the plain old wet cell acid battery is the cost effective champion. The battery is very forgiving, well understood, easy to evaluate, low cost, and a whole host of benefits. Sure, upon a test bed with accurate control they are inferior in every way. In real life economics and life span they win. This is why the auto is still utilizing the battery. Even the cost efficient hybrids of the future. Read the solar blogs recommendations for max cost effectiveness and durability. They all are buying 6v golf cart batteries. They claim the lithium has incredible lifespan, well, maybe in ideal environment. Factor in the cost of money and the battery fails to compete. It may in the future be a super battery, but this technology and science stuff takes a long time to prove itself beyond the hype to convince those of us that want to read real life results. The AGM may have 2x the battery life of a golf cart battery. True. But that would be the most ideal abuse environment to make the comparison. Under normal deep cycle battery operating conditions and maintenance they are equal. Oh, the golf cart battery costs 1/2 as much.

 

Same for solar. Under ideal conditions the device preforms well. Problem is, you can't depend on them and as a result you still need to maintain your original generator specs. Some solar enthusiasts will max out battery power storage to span several days without sunshine. Even three days when subjugating all to advantage solar. Consider the cost and inconvenience of proving to the world you can go without a generator. No thanks. I'm more practical and less bull headed than that. Besides solar is way to expensive and inconvenient. You have to continually monitor the system and make adjustments. It requires very expensive control equipment, expensive batter bank, and very expensive installation. Non the least it is inflexible. You can't decide to park in a shady spot to keep cool. You can't decide to top your battery bank off at 6:00 am or 8:00 pm.  Some claim solar is best utilized as a battery maintainer. That running a generator for long time periods is impracticable for a complete charge as compared to solar quiet operation. You read that you must completely charge an acid carbon battery or suffer a shorter lifespan. Well, true enough, but conversely the lithium has problems if stored at maximum charge. All batteries suffer if stored with minimal charge. The truth is a working battery never achieves full charge status at least for any length of time. So, a working wet cell need not be fully charged for days. However, it should be fully charge upon storage or non use. Storing a partially charged carbon acid battery is a bad maintenance practice. Given a working battery may never achieve full charge status for any length of time, one would think the lithium would be the best. Again, when considering the real world economics one can suffer a lead acid battery with less than maximum life span. I see Sam's club sells an excellent 6v golf cart battery for $89. You will need two and enjoy 220 amp hours of power storage, but alas best to only use 50% of that for good battery practice. Sure you could go 80% with lithium maybe or 60% maybe with AGM, but again the cost efficient economical choice by far is the plain golf cart battery. If you screw something up and completely ruin the batteries, which one would you prefer. 

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The telecommunications industry has a long history of operating equipment from batteries and utilizing generator recharge. They use lead acid batteries. They are utilizing generators instead of alternators, too. Caterpillar study had most efficient setup when generator matched with recharge requirements. This improved the efficiency of  their diesel engine. Efficiency of most engines at max torque. Again, with ethanol propensity to maximize torque, even above diesel, should be wake up call of efficiency potential of an ethanol engine. So, oversize generator is a loser. Match the generator to battery bank recharge requirement.

 

Flipping back and forth from AC to DC is also a losing proposition. Inverters and converters just extra baggage drag on power. For example an AC portable fan will require 2x or more wattage when running on the RV battery bank as compare to equivalent DC fan. It seems that if and in fact when one is attempting to be off AC grid, everything should be DC. The over the road trucking industry has developed DC products for this reason. Refrigerators, A.C., microwaves, etc. I read even the Tesla car is rethinking the AC and DC complexity and cost. The DC brush less motor is quickly becoming superior solution. More torque and speed with less weight and complexity. Battery charger become less complicated as well. 

 

When one factors in the apparent move of automotive to 48v power, this will greatly accelerate the off grid DC solution. Not bad for large households to jump to a 96v or 144v DC standard.

 

What is changing? Power production is available at the point of use. This takes away the primary advantage of AC power. Also, electronics can control voltage, nowadays. Also, you can see how a mobile battery bank and generator aka your car can integrate and provide value.   

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D.C. power is the best choice for micro grid. Most of our electronics and appliances run more efficiently with direct power. Motors, TV, lights, computers, and even refrigerators. Twelve volts power is fine for low wattage devices, such as lighting, but most appliances need a multiple of this. Within the RV, power demands of a battery bank drops drastically when omitting the A.C. devices.

 

They have good and growing market for DC devices. TVs drop wattage down by 50% when powered directly by DC and avoiding the  transformer or converter loss. LEDs drop to a fraction of AC variant. You can find low wattage hair dryer, small AC units, fans, and of course computers. I read some companies think homes and commercial buildings will go DC with micro grid control because of the low power and efficiency gain. These companies are investing in products for the up coming change. Rooftop solar does dovetail nicely with this technology. I think way to many technical people are attempting to operate their household with DC power within the conventional method operating AC equipment. These people are really undermining the value of DC power with inverter and/or converter equipment and the subsequent low efficiency. My evaluations point to the increase use of natural gas or propane for high BTU loads and a complete DC system for the rest. In other words utilize electrical power whereupon it is most valuable and natural gas where it is most valuable. Natural gas is 3x more efficient if utilized at home instead of producing far off electric power. Why do Environmentalist attempt to utilize the grid power for everything? If Environmentalist are attempting to maximize the benefit of green power portion of the grid, the highest priority would be to minimize the use of grid power and allow the green portion to grow.  If attempting to maximize grid power efficiency one has to consider the high cost of appliances and not to forget the high repair cost or shorter lifespan equipment such as heat pumps. Utilizing NG for cooking, hot water, and space heating seems to be a no brainer for the environment and consumer cost savings. 

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I crunched the solar cost justification numbers, again. I do dream of having a solar system, but will not act foolishly with money. Per my conventional (maybe higher than normal) ROI requirements,  solar needs to improve a bit. Not just a bit but a whale of a bit. I took the most cost effective system I could come up with, other than home built. A portable 120w system with charge controller for $700. This is a good unit since it packs up very efficient for transport and can be pulled or directed to where the sun shines for higher utilization. I was more than generous with the cost savings dollars, but could only justify 1/10th the cost. You have to realize the solar system can't displace any power generation as solar is not reliable. It's just supplemental or auxiliary system. It requires a lot of work to setup and manage. One can easily overspend on equipment to automate solar or make it more effective. Solar is not worth considering or bothering with. It's a toy and only to be used for entertainment such as experimental and human interest storytelling.

 

I have a Yamaha 1 kWh generator that provides the boondocking power. It is very quiet, about like the Honda's, but some say quieter. I bought this generator as the fuel consumption rating was the best. I don't have a kW meter to fully evaluate the cost of electricity, but it doesn't matter much given the generator needs to be on to produce AC power. Meaning the battery bank can be greatly downsized if one plans on utilizing a higher percentage of power during generation times. Also, the bulk charge for battery is easy accomplished  with smaller batteries. Again, best to run generator until this battery charge point is met and until AC power demand is gone. Incredibly the generator for my hours of production, mostly on low engine RPM is an incredible .7 cups of gasoline per hour.  That is less than one cup per hour. I'm guessing all in all my AC power cost approximately $.25/kWh. 

 

If you like extreme quiet, utilize a inverter for AC needs in early morning and late evening. Beyond that a sound box is easily constructed. One which the muffler has a longer path and ported out of the box. The box would need stiff hard material such as 1/2" cement board. Cement is the absolute best material to stop noise. The classic design has a box in a box with air gap inbetween. Every crack sealed with butyl rubber caulk. The bottom rests on open ground. Intake air fan may be needed as well. Results to be expected- all but silent operation. The generator is light and will prove to be very useful for many activities all year long.

 

So, my contention for domestic power production that is both cost effective and good for the environment still is get rid of as much A.C. load as you can and convert to D.C. equipment. To utilize no more than 1 kWh golf cart battery pair to power the home when off generator times. That the most efficient and environmental home would operate on DC and utilize a very small CHP power generator to produce both power and heat. This is basic technology stuff, already available, just that corporate America or government hasn't figured out a way to control the market for gain. Natural gas or propane would be the energy source. No expensive and unreliable grid required. I wouldn't bother with solar either. Even lithium batteries, not a cost effective solution.  

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