So, I have decided to address those concerns with some math.

The battery powered blanket is specifically designed for a stand hunter, who after he/she has walked into the hunting area, and now starts to sit and starts to get cold.

So, first off, there are several limitations that need to be addressed for this situation. First one is the Federal Government's law regarding electric heating blankets. Everyone remembers "grandma's" blanket that would get nice and cozy. Well apparently, it got a little too cozy and started several houses on fire. So, the Federal Government stepped in and placed limits on electric blanket manufacturers and how hot the blankets could actually get, via the federal flammable fabrics statue.

So, to get a waiver from the Federal Government or to get a manufacturer to violate that law is not very likely.

Because of that restriction, all blankets currently manufactured have a thermostat type of circuitry built into the heating filaments, that actually limit the amount of current (heat) that they can produce. So, no matter how much power is supplied, the circuitry will cut off the power at a certain temperature.

So, the topic of this blog post, is DOES IT WORK? Obviously, as in most blog posts the answer is the same, it depends.

So, some math.

There was a study done by Cornell University that breaks out in table form, how much heat the human body emits during various states. Of course there are many variables, such as physical fitness, square footage of surface area of the body etc. But, for an AVERAGE person, sedentary, the body emits approximately 300 btu's of heat, or approximately 100 watts.

The body emits during moderate exercise (hiking) approximately 200 watts, and during very strenuous exercise approximately 300 watts.

So, when the hunter is walking into his blind in the morning, most hunters have to stop from time to time to prevent "sweating" and from getting too hot. Then of course, if you did get sweaty on the walk into the blind, then you are wet, and now very susceptible to getting cold once you start sitting in the blind.

So, if the blanket could produce 100 watts of additional heat (your body produces 100 watts at rest), that would 'equate' to your body temperature while walking. Likewise if it could produce 200 watts of additional heat, then it would be the equivalent of you doing strenuous exercise inside your blind.

The low power blanket is rated at 12V and 4 amps, so approximately 50 watts.

The high power blanket is rated at 24V and 6 amps, so approximately 150 watts.

The low power seat heater is rated at 12V and 1.5 amps, so approximately 18 watts.

The high power seat heater is rated at 24V and 2.5 amps, so approximately 60 watts.

So, with those numbers, one should easily be able to quickly determine the appropriate blanket and or seat heater combination.

If you have any other additional questions, please don't hesitate to reach out.

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There have been 2 new products released : Portable Tent Heater and the Portable Shower

There are several more products currently finishing up field testing and final design. So be sure to keep up with the blog and stay informed of the latest.

We have also uploaded the new logo to the site and have been doing several other little tweeks on the backend of the system to make your experience here at offgridcomfort.com that much more user friendly.

We are also always available via email if you ever have any questions regarding any existing products, or even any product ideas. Our founder loves the challenge of creating new products to solve outdoor and outdoor comfort and convenience problems.

Be sure to check back often.

]]>5gallonairconditioner.com is now offgridcomfort.com

With our amazing success with our air conditioners, and with our tremendous feedback for "more stuff" we have decided to make our products and our site more general in nature, yet still stick to our core principle of "Outdoor Comfort and Convenience."

So, we have expanded our product line, and changed the look and feel of the website, to help us further that cause.

Keep watching the website, and reading this blog for the latest updates, as we are currently putting the finishing touches on several new great products that will make your next outdoor experience "that much better."

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I have hinted at the laws of physics in the past, as these dang laws that are causing us all of our problems etc.

So, in this short post, I will go over a few of these laws that no matter how hard we try, we are just not going to overcome them. I will try my best to keep the math to a minimum and keep it simple.

The first one is the automotive air conditioner condenser and the average automotive AC unit being rated at 1.5 tons. There are several conversions that I will go through on this for you, to try and make it as simple as possible.

So, as discussed previously 1.5 Tons of cooling capacity equates to 18K BTU/HR. Well, there is a conversion factor that goes from BTU/HR to HORSEPOWER. For simplicity sake, 18K BTU/HR = 7.074 HP.

So, for simplicity, that means that it takes 7.07 HP from the engine of the car to run the air conditioning unit in the car. An AVERAGE car makes about 150 HP, so therefore about 5% of the engine power is utilized for air conditioning.

But, there is also a conversion from BTU/HR to WATTS. Remember watts = voltage X amperage. So, 18K BTU/HR = approximately 5275.3 watts. An AVERAGE accessory in and AVERAGE car, such as the cigarette lighter, is run on a 15 Amp fuse. A 15A fuse on a 12V circuit is 180 watts. So, it would take approximately 30 cigarette lighter plugs outlets to supply enough wattage to supply a 18K BTU/HR air conditioner for a car.

A typical car alternator the produces electricity, generally has 2 different amperage ratings. A low speed rating and a high speed rating. Where the low speed rating is how much amperage the alternator produces while the engine is idling, and the other is how much amperage the alternator is producing while the engine is at WOT (wide open throttle). The AVERAGE car at the MID range (highway cruising speeds) of it's amperage output, puts out about 60 Amps. So 60A x 12V = 720 watts.

So, that is a lot of information and numbers to digest.

So, now let's theoretically look at how I could build a 5 gallon air conditioner unit to produce 18K BTU/HR to replace your automotive air conditioner.

First off, I would need to look at the largest amperage draw I could electrically pull from the engine. 60A. Then I could covert 720W (60Ax12V) into HP (0.96hp). Then I could convert HP to BTU/HR = 2442. So, going electrically, the BIGGEST unit I could build (using the laws of physics) for an AVERAGE car with and AVERAGE electrical system is about a 2500 BTU/HR unit. That is a little better than 1/8 the capacity of the current mechanical units.

So, electrically is the wrong approach for that application.

What about for big trucks, like Semi Trucks and delivery trucks etc. They have alternators that mid range produce about 200 amps. Following the same logic, about 8100 BTU/Hr would be the made AC size that could be built. So, about 1/2 the capacity of an AVERAGE car.

So, this is just ONE of the laws of physics that we have to contend with, weight is another, efficiency is another, over time, each of these different areas will be discussed as well.

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14 days in the southern Utah desert in the middle of August, in a tent.

Here is the equipment list:

Solar kit - Panel, 12V battery, 50ft cord

EVAP unit - Variable speed with flow director

Daytime temperatures ranged from mid 80s to low 100s. Humidity ranged from 100% (raining) to 15%, with an average of 25%.

In a word, AMAZING!

Amazing is really the best way to describe how well this setup worked in this environment.

The 50ft cord worked perfectly, as I just set up the panel and didn't have to move it at all. The 50ft cord was the perfect length, to reach from one end of the camp to another. Just set it and forget it.

I would take the 5 gallon bucket air conditioner EVAP unit inside the tent while napping, and turn the speed down low for low noise, and the flow director would gently direct cool air right on my body making for the perfect resting temperature.

While outside manning the stove cooking lunch or dinner, I would put the 5 gallon air conditioner EVAP unit on that lower table (where pictured) and turn it on high, and the flow director would blow very cool air right on me while standing behind the stove. The noise wasn't bothersome, and the cool air was literally a breath of fresh air. At one point, during one of the 80 degree days, I actually had goose bumps on my arms because of the cold air blowing on me.

After a long hike, I would come back to camp, put on some flip flops, lounge back in the camp chair with a cold beverage, and put my feet on the top of the 5 gallon air conditioner bucket lid, and with the unit turned on high, and with the flow director, it would cool me off very quickly, and even give a chill.

I had the unit running for several hours at a time, as many as 8 continuously, and the battery and panel never lost power, even during overcast days. I left the solar panel connected to the battery the entire time, so the battery was always fully charged every day, and the system never lost power.

Water consumption wasn't bad. I would go through about a gallon an hour on average. The 5 gallon air conditioner EVAP model holds about 3 gallons, so on average, I would get 3 hours of usage before having to fill it back up.

On some of the 80 degree days, I would actually have to shut the air conditioner off, as it was too cold.

As mentioned, it did rain some days. I left the solar panel alone (where pictured) and tucked the battery under/behind the panel and never had any moisture problems with the battery or the panel functionality. The flow director provided some shielding from the rain as well on the fan, when I happened to leave the AC unit out in the rain while away from camp.

This EVAP model made the 2 week stay in the desert, not only comfortable, but downright AMAZING.

]]>If only there weren't these dang laws of physics to deal with, the world of temperature and thermal comfort would be a lot easier to deal with.

So, we here at 5gallonairconditioner.com get a lot of strange questions and situations presented to us, asking if our 5 Gallon Bucket Air Conditioners will work in X situation.

One of the most common questions is will it work in my car/van/truck/jeep etc, in the deep south with 90% humidity?

In order to answer that question, we have to look at the physics.

In any car/automobile, the air conditioning design engineers have dozens of factors to look at when designing/sizing the AC unit for the car. Some of those design factors are interior volume, car color, engine heat, exhaust heat, window size, paint adsorption, number of passengers, along with a dozens other factors etc. Because the thermal load in automotive applications is so high, the engineers have to make sure they account for everything "and then some." For ROUND numbers the AVERAGE automotive AC unit has a rating of 18K BTU/Hr, or what in the industry is 1.5 ton capacity.

So, now we can briefly discuss what TON means in terms of air conditioning. As has been mentioned in previous blog posts, the latent heat of fusion of ice is 143 BTUs per pound. So if you have 10 pounds of ice, it would take 1430 BTUs to melt that 10 lbs of ice, and turn it from 31.999 deg F ice to 32.001 deg F water. So, now if you have 1000 lbs of ice, it would take 143,000 BTUs. If you had 1 TON of ice, it would take 286,000 BTUs.

But, remember that BTUs don't really mean much until you put a time component on them. So, now if you had 1 TON of ice, it would take 286,000 BTUs to melt it. And if you melted 1 TON of ice in 1 day (24 hrs), then the math works out to 286,000/24 = 11,916 so for round numbers 12,000 BTU/HR = 1 TON.

So, a TON is really a comparison of ice. Therefore, we can make a direct correlation with our ICE model air conditioners.

So, now an AVERAGE car (we're talking Honda Accord/ Toyota Tacoma/ Ford Fusion etc) has an AC system that is rated at 1.5 Tons. Larger trucks get up to 2 to 2.5 Tons.

So, now with the 5 gallon bucket air conditioner filled with 30 lbs of ice, it is a very easy comparison, 30lbs of ice, is about 1.5% of a ton. It is 1% of 1.5 Tons. Remember 1.5 tons = 3000 lbs.

So, the factory air conditioner in an average car, has the cooling capacity of melting 3000 lbs of ice every day. That is the thermal load in an AVERAGE car. So, that calculates out to 125 lbs of ice melted every hour.

So, our little 5 gallon bucket air conditioners filled with 30 lbs of ice are not even in the same league.

So, in that situation, our 5 gallon bucket air conditioners ICE models will not work for long( nor as well as the factory AC unit designed for the car), as our 30 lbs of ice will melt in 1/4 (approximately) of an hour, or for round numbers, every 15 minutes. With the water coldness and the outside air temperature factored in, the "ICE model will work" in this environment for approximately 30-40 minutes before the water temperature is too high to have any meaningful difference.

So the answer to the question of, will it work in a car? The answer is YES, but only for about 30-40 minutes.

The next question we get asked a lot is about a small apartment that can't have window units due to fire escape blockage etc, of course in high humidity areas.

Here is the mathematical formula for that calculation.

House(room) square footage multiplied by 25, the product divided by 12,000, and minus 0.5, and that will equal the required tonnage.

So, let's look at a small 1000 sq ft apartment. Here's how the math works.

1000*25 = 25,000

25,000/12,000= 2.08

2.08-0.5=1.58

So, in this situation, the required size AC unit is 1.5 TONS or 18,000 BTU/hr. Again, this is the same thermal load as the automotive application above.

In this case, our little 5 gallon bucket air conditioner ICE model will not work.

So, now let's look at a dorm room. Let's say the dorm room is 200 sq ft. The math:

200*25 = 5000

5000/12000=0.416

0.416 - 0.5 = negative.

So, in this case, the math works out to where our 5 gallon bucket air conditioner ICE model WILL work. Now, the key would be to have a constant supply of ice. But, from a capacity point of view, YES, our 5 gallon bucket air conditioners WILL WORK in this situation.

So, here are again more answers to the question of, 5 gallon bucket air conditioner, does it work?

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The fan is THE KEY COMPONENT to these types of projects. It is the fan that will determine whether the device works or not. The fan design is critical.

So, there are 3 main things one needs to look at when it comes to fans. Namely, the power requirements, cubic feet per minute (CFM) output, and the static pressure. Think of these three requirements as 3 points on a triangle. If you change one, then the other 2 will HAVE to change.

So, there are many fan types, shapes, designs etc., but at the end of the day, they all do the same thing, move air. So, it is naive to assume that fan design for the 5 gallon bucket air conditioner is very simple, you want the fan that moves the most air, period. That is very simply is NOT the case.

I have read and have seen all of the other 5 gallon bucket air conditioners on the internet. I can assure you, not one of them, other than mine of course, is designed by an engineer who "knows what he's doing." It's obvious. Because, of that, the 5 gallon bucket air conditioner is getting a 'bad rap' because so many 'other guys' are giving negative reviews, saying it doesn't work, etc. You won't hear that about my units. These things work. Because they are specifically designed, component by component to work as a system, for maximum performance.

The fan is the most crucial piece of this puzzle.

So, I see a lot of guys talk about using large "endless breeze" fans or even a Honeywell "turbo" fan etc. Beside the fact these things are huge and not aesthetically appealing, they don't work as well as my fans do. There are videos of little tassels and streamers showing the air flow etc. One may wonder why I don't show that on any of my videos? Simple, my fans produce so much pressure that it would rip the streamers right out of the tape, and the streamers would be 10 feet long and still blowing strong as they are blowing across the yard!

That's because, the key to these units is the fan pressure, not the air flow.

I read over and over, and I have to chuckle, about how these DIY guys, want bigger fans that move more CFM etc. Then I read where they found a fan that will move 900 cfm, and only draw 1.5 amps of current. That is comical.

I'm not saying there aren't fans that draw 1.5 amps of current, and move 900 cfm of airflow, I'm just saying, those fans won't work effectively for THIS purpose.

So, here are some pretty basic engineering principles that I am going to try and make as simple as possible for you to understand.

The first one is pressure.

Think of 2 square chambers, equal size, mounted side by side, connected with a small pipe. One chamber has high pressure in it, and one has low pressure. Obviously the pipe connecting the 2 chambers will EVENTUALLY put the 2 chambers at equilibrium pressure.

Now let's make that pipe, smaller and smaller, and in fact let's make that pipe so small that is considered 'an orifice' rather than pipe. Let's say that the orifice diameter is measured in thousandths of an inch rather than in inches.

Now, let's say that the pressure difference between the 2 chambers is less than 1 psi, when we open the orifice.

Now, how long will it take for the 2 chambers to equalize, assuming the chambers are very large?

A long time right? There simply isn't much pressure difference, and the orifice diameter is very small.

Now, let's change the scene a little bit. Now let's have the same situation, but let's make the pressure difference between the 2 chambers large, like 200 psi. Now what happens when the orifice is opened up? The air will be "screaming" going from the high pressure to the low pressure, right? There will be huge velocity going through the orifice, NOT A LOT OF AIR, but very fast air.

There are obviously many calculations on orifice flow, and orifice flow geometry, and orifice design and shape etc. But, for our overly simplistic example, one can see that at least in this example, there would be very high velocities of air flowing through our orifice.

So, now, how does one get such high pressure into the high pressure cylinder? This is where a pump comes into play. When thinking of a pump, think of it as something converting power into pressure. That power can be electrical power, can be chemical power, mechanical power, any kind of power, and then converting that power into pressure. In our case, that pressure is air pressure.

So, in most cases, one would use electrical power, to compress the air, and then use that compressed air to pressurize the "high pressure" chamber. There is no other way to create pressure, without power.

Ok, so now, with those basic understandings of power, pressure, and air flow, we can go back to talking about fans.

One can see, that with enough power, there can be a lot of pressure, but not necessarily a lot of airflow. The flipside is also true, if you use your power to move a lot of air, there won't be a lot of pressure.

So, now, with that basic understanding of engineering, you can now see where these DIY guys are talking about 10" fans that draw 1.5 amps and blow 900 cfm, that there is not any pressure. To put that in comparison to the 5gallonairconditioner.com fans, they draw over 4 amps of power and flow 250 cfm of air.

To compare the fans, my fans draw 3Xs the power, and blow 30% of the air, so what does that mean? That means that they have MASSIVE VELOCITY due to the very high pressure as compared to these other designs being touted on the internet.

Another way to think about it, is to place one of the competitors fans next to a book, and turn the fan on. Their fan will blow a lot of air, and may flip a few pages in the book. My fan? Flip the book over end over end and blow the entire book off the table, ripping pages out as it's doing so.

So, why is this important? Why the need for such pressure?

Simple.

Performance!

It is because of this pressure that makes the 5gallonairconditioner.com units work, and none of the others do.

So, to answer the question, 5 gallon air conditioner, does it work? The answer is, Yes !!

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We here at 5gallonairconditioner.com get asked a bunch of questions. Does it work is by far the most common question, and after 3 or 4 more questions, then the conversation gets to "well, what is the BTU/hr rating of your units?"

I have written several blog posts about the ICE model units and the BTU content of ice, and ice melting, etc. So, if you haven't read any of those blog posts yet, you may want to read through those to get a better understanding of the ICE model units and their cooling capacity and the proper application of those models, etc.

The EVAP models are a completely different device than the ICE models, yet they share many of the same characteristics. First and foremost, both models are completely portable, can be battery powered, are very lightweight, very durable, AC and DC powered etc. The EVAP models also include inexpensive pads, a small pump, and as I will show, they are a very good value for their cooling capacity.

We have conducted in house experiments to determine water usage and subsequent BTU output. The water volume put in the EVAP unit was precisely measured and the device was operated for a very exact period of time. Then exact water consumption during that specific period of time was then determined.

Water has a very specific "BTU content." That BTU content is how air conditioner units are sized for residential and commercial applications. Because water has a specific BTU content, and evaporation is the process, then very simple calculations will show the "size" of the evaporative cooling capacity.

Water temperature has very little, in fact negligible affect on the BTU content of the water. So, some guys say "put ice in the water" so then the water/pads are colder. Other guys say, "no, you want the water to be hot so it will evaporate faster." Both "guys" in this context are correct, yet both are incorrect as well. Reality is that water temperature has such a little affect, that most engineers generally disregard the water temp in their calculations.

So, the cooling content of water is 8700 BTU/gal.

Now remember this is the "scientific" number of "perfect RO/Distilled" water at standard atmospheric conditions, etc.

But, this is the number that engineers use, almost universally in almost all but the most precise of applications and calculations.

So, 8700 BTU/gal is the number we will use.

So, with this number, it is very easy to calculate BTU/hr, right? Simply pour in 1 gallon of water, turn on the AC unit and see how long it takes for the gallon to completely evaporate.

Well, there's a little more to it than that, such as outside temperature and humidity level, enthalpy and efficiency, etc., but for our purposes, and to try and keep things as simple as possible that was in essence the measurement that was made in our experiments.

So, in 1 hour, there was 118 fl oz of water consumed/evaporated in the experiment (pad weight was precisely measured before and after also). There are 128 fl oz of water per gallon.

Using those numbers, we can calculate BTU/hr ie, sizing of the 5gallonairconditioner.com EVAP unit.

So, to find the percentage of a gallon consumed, simply divide 118 oz by 128 oz. So, 118/128 = 0.922. So that means that in 1 hours time, 92.2% of a gallon of water was evaporated.

Now multiply .922 by 8700 BTU cooling capacity of water. That comes to 8020 BTU/hr.

So now that we have the BTU/hr rating of this evaporative unit, then we can use it compare this AC unit with other AC units currently available.

According the the online charts, an 8000 BTU/hr AC unit should be able to "comfort cool" an area between 250 sq ft and 400 sq ft. An average sized bedroom is about 150 sq ft. The average kitchen is about 250 sq ft. The average 2 car garage is 400 sq ft.

Another thing to note, is that the 5gallonairconditioner.com EVAP unit will hold in excess of 3 gallons of water. So, that means that the AC unit will run for about 3 hours before it needs to be refilled on average.

So, now armed with all of that information we can talk about value.

So, considering the performance, a realistic measure of value, is to compare the 5gallonairconditioner.com EVAP model to what else is commercially available. They are admittedly tough to get an exact comparison, because the 5gallonairconditioner.com EVAP units have so many additional features, such as portability, DC powered, outdoor and off grid applications etc.

So, just a quick scan on the internet shows the current cost of an 8000 BTU/hr cooling unit ranges from about $200 up to a little over $400 depending on brand and features.

When compared to those units, on a performance basis, the 5 gallonairconditioner.com EVAP units are a good value. Then when you factor in the light weight, cost to run, portability, battery power option, ease of use, durability, no toxic chemicals/green, etc., the 5gallonairconditioner.com EVAP model is hard to beat.

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Here is a short video uploaded today, demonstrating the 5gallonairconditioner.com evap model on a hot summer day.

For the non-techie types, just watch the video, and the answer to the question of does it work, is an astounding YES!!

For you guys that like to dig into the dirt a little bit, here is some of the explanation and the engineering and physics behind what you are seeing in the video.

To understand what is going on, one must understand a field of science called psychrometry. That is just a fancy word for weather phenomenon. You will also need to understand phrases like dry bulb temperature and wet bulb temperature, dew point, relative humidity, and a whole host of other factors.

I will try my best to simplify this field of study the best I can for you.

Dry Bulb temperature is the temperature that a thermometer reads "normally." When you look at an outside thermometer, you are seeing the "dry bulb" temperature.

Wet Bulb temperature is the temperature that a thermometer reads if the "bulb" of the thermometer was wrapped in a wet rag, and wind was blowing on the wet rag. Wet bulb temperature is the "theoretical lowest temperature" that evaporative cooling can achieve.

These are the two main things to know to have a basic understanding of traditional evaporative cooling.

So, there are charts that scientists use called psychrometric charts, and it's from these charts that the scientists calculate relative humidity and a whole host of other weather physical properties.

For our discussion today, and for the purpose of this video, we will only concern ourselves with dry bulb temperature (dbT) and wet bulb temperature (wbT) and relative humidity (RH).

So, in order for anyone to make an accurate assessment on evaporative cooling performance, a very critical number that is rarely mentioned, but is absolutely critical in evaluating performance is humidity, or more specifically relative humidity.

Once you have the relative humidity, and the dry bulb temperature, then you can look at the psychrometric charts and figure out the wet bulb temperature and all of the other important factors. But, for our purposes, the key factor is the wet bulb temperature.

So, to obtain the RH, the easiest way is to log into the local weather station closest to your location and pull up the real time weather data. Temperature can vary a few degress, but RH is very accurate from these data sources.

So, then once you have the RH, then use a local, meaning, in your hand thermometer to measure the exact dry bulb temperature of your exact location.

As you can see from the video, getting a dead solid dbT is difficult because of the solar affect (mentioned in another blog) of surrounding objects. So, it's easiest to just average all of those dbT's that you get in your immediate area. So, even though in the video, the weather station temperature when the video was made was 101 degF, but due to solar affects from the concrete, and the steel of the table, and the 'cooling' of the trees etc, the average dbT was approximately 104 degF.

So, as mentioned in the video, the RH at the time of the video was 16%.

So, armed with that data, dbT of 104 degF and 16% RH, also the barometric pressure was 30.02 for those super technical guys. So, according to the psychrometric charts, the wbT (theoretical lowest temperature possible) is 67 degF.

So, when determining the performance of the AC unit, you can see, that you need to know all of those factors, before you can accurately answer the question, of "does it work"

As can be seen in the video, the output air temperature also bounces around, so an average needs to be taken there as well.

I averaged the output air temperature at 70 degF for the following calculations, where you can see depending on the exact location of the pointer, it ranged from 60degF up to about 74 degF. So, 70 is a pretty good average.

To calculate efficiency, simply divide out the average measured temperature difference by the maximum possible temperature difference.

So, the calculation is as follows:

Efficiency = (104-70)/(104-67) = 34/37 = .919 = 91.9% efficient.

Now, what if you think that the 104 is on the high side, and you just take the weather station data of 101 degF.

In that case, the wbT is 66 degF.

So, then the efficiency calculates out as follows:

Efficiency = (101-70)/(101-66) = 31/35 = .886 = 88.6% efficient.

As a means of reference, most house/home swamp coolers sold at big box hardware stores like Home Depot or Lowes etc. Those swamp coolers using the best pads achieve around 75-80% efficiency. Large industrial swamp coolers typically achieve about 85-90% efficiency. Most "old school" swamp coolers from the 70s and 80s had efficiency in the 60-65% range.

So, to answer the question, of "Does it work?"

The answer is YES!

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So, we here at 5gallonairconditioner.com constantly get asked, after "does it work" the next question is "how noisy is it?"

So, in this short blog post, I will talk about decibels, typical decibel levels, and simple facts.

A decibel is the unit scientists use to measure the intensity of sound. One odd thing about the decibel scale is that it's logarithmic. Now, don't let that scare you, logarithmic scales are very simple to understand.

Since the human ear is very sensitive to sound, scientists need a VERY BIG range to accurately measure sound intensity. For instance, when it is completely silent in a room, and you can hear your fingertips slightly rubbing against each other vs standing right next to a jet fighter airplane with full afterburner engines. That is a VERY BIG range of sound intensity that the human ear can hear, and so therefore, the decibel scale is logarithmic.

Think of a logarithmic scale this way, ADD ZEROS. So, for instance, total silence is 0 decibels. Then a sound (such as rubbing your fingers slightly together at 1 ft away from your ear, about the lowest the human ear can hear) that is 10 decibels, is 10X more powerful than total silence. So, in that case, you added 1 zero for 10 decibels.

So, now a sound that is 20 decibels, you ADD A ZERO, so that sound (rustling leaves in a slight breeze) has 100X more intensity of sound than total silence. So, think of the 2 in 20 decibels, as 2 ZEROS (100). So, 20 decibels is 100X more intense.

30 decibels is 1,000X more intense. (very quiet human whisper)

40 decibels is 10,000X more intense, etc. (very quiet library, rustling of books etc)

So, the loudest sound the human ear can hear before permanent hearing loss, is about 200 decibels.

Some decibel examples:

50 decibels - refrigerator compressor, car driving by at 50 ft, percolating coffee maker.

60 decibels - normal voice, dishwasher

70 decibels - vacuum cleaner, loud talking

80 decibels - alarm clock, doorbell, cake mixer

90 decibels - screaming, yelling, shouting

100 decibels - loud factory machines, airplane at 1000ft away

110 decibels - rock concert, chainsaw

120 decibels - police siren

So, here at 5gallonairconditioner.com, I have designed these AC units with a 64 decibel fan. Why you ask?

Performance of course! Oh yeah, and that nasty little thing called the laws of physics.

Think of sticking your head out of the window of a moving car. When the car is going 20mph, there is a sound of wind blowing by your ears. Now, theoretically, if you stuck your head out of the window while the car is going 70mph, that wind noise will be "a lot" louder. That's just simple physics.

So, again, it is a performance trade-off that must be made. I could design a "quiet" fan, but then the fan wouldn't move much air ( 20mph example above). Then you would be disappointed that "the dang thing doesn't blow enough."

So, then I design a "loud" fan, and the comment comes "this dang thing is too loud." But, in this case, what I don't hear is "this thing doesn't blow enough."

A normal "room size" fan sitting in the corner of a bedroom, a typical 20 inch 110V fan on the high setting is approximately 70 decibels, the low setting is about 55 decibels.

So, a fan, any fan that moves any noticeable amount of air, will make noise between about 50 and 70 decibels.

It's simple physics, the more air flow, the louder the sound, ie, stick your head out of a moving car example above.

Another question, we here at 5gallonairconditioner.com get asked a lot is, why not put in a bigger fan?

Again, the answer to that question is, "it's a series of tradeoffs" and "the line has to be drawn somewhere." There are much larger diameter fans that will physically fit, no question. The question becomes, which fan takes the least current draw (as discussed in a previous blog post) for battery life concerns, AND produces enough pressure to actually push the air out the ports and into the room/space, AND moves enough air volume to be effective, AND isn't cost prohibitive AND is DC powered for efficient off grid applications AND fits within the confines of a 5 gallon bucket AND is moisture resistant.

When I factored all of those valid concerns into the design, the result is a fan that makes 64 decibels of noise, takes about 4 amps of current draw, moves 250 cubic feet per minute of air, and has about 1.5 inches of water of pressure.

So, it's a series of trade-offs in the design.

But the final answer to the question, of "does it work?" is OF COURSE IT DOES!

And, to the question of, "how noisy is it?" About as loud as any other fan. Not as quiet as some, but quieter than others.

So, then the next question that get's asked is, "is there a variable speed model" available?

That will be the topic of the next article in the 5 gallon air conditioner - does it work series.

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By definition, the purpose of insulation is to "reduce the heat transfer between the outside environment and the inside environment."

So, that is exactly the opposite of what we are trying to do with the ice model units.

Ok, so here is a quick thermodynamics lesson, in easy to understand language. First off, you need to think in terms of heat, not cold. So, when an item is cold, like an ice cube, in layman terms that means that it is "giving off" cold, but in thermodynamics, it is "bringing in" heat. So, remember, think in terms of heat, not cold.

So, when something "brings in heat" that means, by definition, that it is "giving off" cold.

So, now, in our ice model units, when the user puts a block of ice inside the bucket, what is the ice going to immediately start doing? It's going to immediately start melting right? When ice is melting, thinking in terms of thermodynamics, what is happening? It is absorbing the surrounding heat, right? That's what we want.

We want "the space" that we are trying to cool, to be devoid of heat, so therefore, we want as much coolness as possible.

So, how do we go about doing that?

By design, the ice model AC unit fan sucks in hot/warm air in the top, and blows that hot air straight down into the bucket cylinder. There is ice inside that cylinder, the ice absorbs the heat (melts) and as the ice absorbs the heat, it gives off cool, and then that cool air is forced out of the ports on the side of the cylinder. Pretty basic and simple.

But, what would happen if the cylinder was insulated? That is the question.

Well, first off, there would be less space available for ice, so there would be less "cooling capacity" just simply due to volumetrics. But, in reality, would the ice last longer, that's what everyone wants to know, right?

That's where the concept of air flow comes into play.

Let's just use the example of a 10'x10'x8' room. Let's use the example of that room, which is a pretty small bedroom, or approximately a 6-8 man tent. So, the cubic volume of that room is 800 cubic feet, right? 10*10 = 100, and then 100*8=800. So, there is 800 cubic feet of air inside that room, if the room was completely sealed, w no air leaks etc, and let's also assume that the room is perfectly insulated, and no heat escaped our enclosure.

Now, let's assume that the air inside that room is 90 degF, and for simplicity, lets assume 0% relative humidity.

So, here is the formula:

BTU=1.08 * dT * CFM

1.08 = BTU multiplier at sea level. Well, what does that mean, right?

That calculates out as this: Air weighs 0.075lbs per cubic foot multiplied by the specific heat of air (0.24) multiplied by 60 minutes in an hour. When you multiply that out it comes to 1.08.

dT= the change in temperature of input air to output air.

CFM= the cubic feet per minute of circulating air flow.

We also know that ice has a BTU content of 144 BTUs/lb.

We also know that our fan on these units flows 250 cfm.

Ok, so now we have plenty to work with. Let's assume that we have a 10lb block of ice in our ice model AC unit, and there are no people etc, inside this perfectly insulated enclosure.

What would be our lowest temperature we would be able to obtain?

In this case, we are solving for dT.

dT=BTU/ (1.08XCFM)

dT=1440 (10lbs of ice) / (1.08 X 250) = 5.3 degF.

But, what does that really mean?

That means, that the air inside our test chamber will be 84.7 degF at the instant the last chunk of ice melts and turns to 32 degF water.

But what about insulation, right? That's what we're trying to figure out. If the AC unit is "more efficient" when it's insulated.

When you look at these calculations, you can see that there isn't "a factor" involved inside the test chamber. Now, you definitely want the OUTSIDE of the test chamber to be insulated, but INSIDE, it doesn't matter. The physics and the calculations are the same.

From a practical standpoint, in our 800 cubic foot (cf) test chamber, and a 250 cfm fan, the air inside the chamber is exchanging approximately every 3 minutes.

So, now, from a physical perspective, 3 exchanges per minute, that's a lot. That is "noticeable" airflow, that's almost considered "breezy."

So, if air is blowing by a 5 gallon bucket that has ice inside it, that means that the outside surface of the bucket is cool to the touch as well, and this warm "breezy" air is blowing by the cool outside surface of the bucket, then the bucket will absorb more heat, and cool the air faster.

So, if the bucket absorbs more heat, that means that the ice is melting faster. If the ice is melting faster, then that means that the ice won't last as long.

BUT...

It also means that the ice absorbed the heat faster, and therefore the space cooled down faster.

So, the bottom line in all of this discussion is, YES insulating the bucket will make the ice last a little longer. BUT, that also means that if the bucket is insulated, then it will take a little longer to cool down the space.

So, it's a trade-off, with no practical difference, and virtually no difference when the amount of reduced ice/cooling capacity is factored in.

So, then when looking at things practically, the foam liners are very thin, don't offer much if any real insulation value, they take up space which could be used for more ice, the foam is very "brittle" which means that it leaves those little pellet sized foam "nuggets" everywhere and is always breaking and cracking. Also, even if the sides of the bucket were insulated, there is still a gaping hole in the top of the bucket where the fan attaches and the fan is blowing hot air inside the unit, which is what the insulation is trying to protect against, in addition to the 3 gaping outlet holes.

So, for all of those reasons, the ICE model 5 Gallon Air Conditioners are un-insulated.

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So, I will take a little break from the "does it work" series, to battery life, and battery life calculation to answer the "how long" question.

When talking about DC powered devices, there are 2 things to remember about "power," namely the quantity and how fast. So, how much power, and how fast is it coming, so to speak.

In electricity terms, these are called AMPS and VOLTS. Volts describes the how fast, and amps describe how much.

Think of electrical current this way. Think of a river, let's say a BIG river, like the Mississippi river. Let's say that the river flows at 10 miles per hour. But, because the river is so BIG, it flows 600,000 cubic feet per second.

Now, lets compare that to a small fishing stream in Minnesota, that also flows at 10 miles per hour. But because of it's size, it only flows 500 cubic feet per second.

In this analogy, both rivers flow at 10 mph. But there is a huge difference in the QUANTITY of water that flows.

That is the same with electricity. There are many common DC (Direct Current) batteries on the market. There are AA, AAA, C, D, Car Batteries, Marine and deep cycle batteries, rechargeable batteries, etc. So, for now, we will focus this discussion on 12V batteries.

In a 12V battery, the voltage rating is 12V, in our analogy, this is equivalent to 10mph. So, the big question is current, or in electrical terms, the Amperage.

In the current model 5 gallon bucket air conditioners that are being sold, the current draw is approximately 4.5 amps. What that means is that the fan takes 12V and 4.5 amps to work properly. Remember, you need both, voltage AND amperage numbers to make an accurate "power" assessment.

So, the power consumed by these air conditioners is 12V and 4.5 amps.

So, electrical "power" is called WATTS. Watts is simply the voltage multiplied by the amperage. So, in these air conditioners, they take 54 WATTS to run them. Where 12*4.5=54.

So now that we know the power consumption, we can then calculate how much power we will need to run the device, and for how long the device will run by battery power.

So, for a typical alkaline D cell battery, it has both a voltage rating and an AMP-HOUR rating. So, now an amp-hour is simply how many amps over how many hours. So, in our D cell example, it has a 1.5V and 17ah rating.

So, some quick calculations show, that if you have 8 D cell batteries hooked in series they will add up to 12V, and here's the tricky part, you don't add the AMP-HR ratings, they stay the same when the batteries are hooked in series. So, 8 D cell batteries hooked in series will make 12V and have 17ah of capacity.

So, now let's go back to the 5 gallon bucket air conditioner. It takes 12V to run the fan, and the fan draws 4.5 amps of current (actually less, but for our example, that's what we'll use). So, if you hook up 8 D cell batteries, how long will the fan run?

Very simply, divide the 17ah rating of the batteries by the 4.5 amps of current draw of the fan, and that comes to approximately 3.8 hours.

So, there is the answer to the HOW LONG question. If you hook 8 D cell alkaline batteries in series, in the 100% efficient case, the fan will run for 3.8 hours before the batteries will need to be changed. In all practicality, with inefficiencies and battery age and battery temperature etc., 3 to 3.5 hours is probably more accurate.

So, when choosing a battery to run your new 5 gallon bucket air conditioner, a quick and dirty way to answer the "how long" question is to look at the AMP-HOUR rating of the 12V battery, and then divide the AH number by 5, and then that will give you the approximate number of hours that battery will run the fan before the batteries need to be replaced or recharged.

But, please remember, that the AH rating of a battery, is until "total discharge" so that means, as everyone from a common sense perspective knows, that even though the battery has an AH rating, that doesn't mean that the battery will have a "full charge" throughout that entire time frame. Every battery has a different discharge profile, so even though the battery life may calculate out to 3 hours, that doesn't mean that the fan will be blowing "full speed" over that entire 3 hour period.

That "discharge profile" will be the subject of another blog post in the future, but for our purposes at this point, just remember that the device has a 4 amp power draw, and you can calculate the total battery life question, by simply dividing the battery AH rating by 5, to get a "ball park" estimate of battery life hours.

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So, the next concept that one needs to understand when it comes to Air Conditioning, or more appropriately, temperature control,I need to describe some concepts called "solar affect" and "greenhouse effect."

So, in the most basic terms, solar affect is the phrase used to describe the heat that is absorbed in certain materials by the sun. It's why the dashboard of your car is hotter than the outside temperature in the summer, or your vinyl seats are hot on your legs in your car when you get in.

So that is "solar affect."

The "greenhouse effect" is the phrase for the "trapping" of that heat that is being radiated from the hot surfaces. So, the hot dashboard, seats, and carpet of your car absorb the heat from the sun. But, there is also air (oxygen, nitrogen, CO2, etc.) inside the car as well. So, the heat radiates off the surfaces, and the air absorbs the heat energy. That's why cars are hot and "muggy" in the summertime with the windows closed.

That is the "greenhouse effect."

So, in doing the BTU capacity calculations for an air conditioner, one also needs to take into account the solar affect and the subsequent greenhouse effect of the space needing to be cooled.

Let's use an example.

Let's say there you have a van, parked in a parking lot, with the windows rolled up, and it's 90 degF outside. There are multiple clear windows in the van, and no "heat shades" or shade or anything like that, just a van sitting in the middle of some empty parking lot somewhere. For the purposes of this example we will disregard several factors like color of van, or color of interior, or humidity etc.

So, after 1 hour, what is the approximate value of the solar affect, and the resulting greenhouse effect, and bottom line, how hot is it inside the van after 1 hour?

Well, there are engineering calculations for this, that involve surface area calculations, emmissivitiy, thermal convection, solar reflectance, sun angle of incidence, and it also involves solving the root of a 4th order polynomial, pretty complicated stuff.

So, to spare you all of that headache, let's just say "hot." For ROUND numbers, let's just say that it will get 40-50degF hotter. So, the interior temperature after 1 hour will be approximately 130-140 degF.

Now, you also have to calculate, the continuing solar affect (heat energy that is continuing to be added due to the van still being parked outside in the sun) and the interior air volume of the van. In order for the van to cool down, you must cool off all of the interior space, as well as overcome the additional heat that the sun is continuing to generate.

For ROUND numbers, we can use 100 btu/hr per sqft of exterior in the sun, as the continuing solar affect calculation.

So for ROUND numbers, let's assume the van is a cube, that is 15ft long, 7ft high, and 7 ft wide. So, to calculate the square footage of the roof of the fan, simply multiply 15ft x 7ft = 105 sqft. To calculate the square footage of the side of the van, 15ft x 7ft = 105 sqft. (sf)

Then of course the VOLUME of the van is 15ft x 7ft x 7ft = 735 cubic feet (cf)

Next, we need to make an assumption, that the van will be in direct sunlight, but that direct sunlight will heat the roof of the van and 1 side (the bottom of course not, and the other side will be shaded). Of course we know these are big assumptions, but we are working towards a ballpark estimate.

So, we are asking our air conditioner, to drop the temperature from 140 degF down to 70 degF (70 deg temperature drop), in a space of 735 cf, with the sun beating down on the van where the sun is adding 21000 BTUs/hr to the space due to the solar and greenhouse effects.

Also, keep in mind, this is a SEALED system, or at least "not rolling down the windows" situation. Obviously, that will be the next subject of the next blog post, but for this example, we are glutton for punishment and keeping the windows rolled up and are assuming no airflow.

So, first off, we know we need AT LEAST the 21000 BTU/hr in cooling power to offset the solar affect. Then we need to calculate how much capacity to cool the space 70degF.

There are many online calcuators that will do this for you, but for the purposes of this article, I will just average them out at about 9000 BTU/hr in this example to cool 735 cf 70degF.

So, we will need an air conditioning unit capable of 30,000 BTU/hr to keep this van "comfortable" in this situation. Granted, this is a worst case condition, and round numbers, but it is "ballpark."

So, remembering from previous posts, a 10lbs block of ice has about 2000 BTU of cooling capacity. So, in this situation, utilizing an ice model air conditioner, one would use 15 blocks of ice per hour, or utilize 150 lbs of ice/hr.

It could be done of course with enough coolers, but for all practical purposes, a singe ice model 5 gallon air conditioner would NOT work in this situation.

But remember those nasty assumptions.. we will come back to those in some upcoming articles.

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Ok, so this concept is very easy to say, but a bit difficult to think about.

A few days ago, I wrote about a BTU and what BTU is a measure of, and why we measure air conditioner capacity in BTUs.

So, this short blog post is going to give a little more info, specifically about ICE air conditioners. I will give the specific scientific definition, and then follow it up with a "regular Joe" translation.

"Latent heat or heat of fusion, is the amount of heat energy required to melt one pound of a given substance from solid to liquid state without a change in the substance temperature."

Translated, in our application, it means, how much heat energy is required to completely melt 1 lb of ice.

So, let's create an example. Let's say you are in a deer blind, 6ft x 6ft x 6ft (no insulation), it's 90 degF inside the blind, and you intend to stay in the blind 4 hours.

According to the laws of physics, it takes 144 BTUs to completely melt 1 lb of ice. So, therefore if you place a 10 lb block of ice in one of my ice model air conditioners. The air conditioner will have transferred 1440 BTUs (assuming 100% efficiency) of cooling energy into your space, the instant the last chunk of ice melts.

At that point, all of the ice is melted, but the 10lbs of water is still 32 degrees. Therefore, there is still "plenty" of cooling capacity left in the bucket.

Let's try and calculate what "plenty" is: remember the definition of a BTU is the amount of heat energy required to raise one pound of water, 1 deg F.

So, if the water temperature is 32 degF, and the outside temperature is 90 degF, therefore there is 58degF of temperature difference, and 10 lbs of water. Therefore there is still 580 BTUs of cooling capacity left in the water.

There are many online calculators that can be used to determine AC size based upon structure type and size. So, assuming worst case scenarios, with the 6x6x6ft deer blind, we come up with the following.

So, according to the online calculators, there is a requirement of approximately 2000 BTUs, and we just calculated that 10lbs of ice to go from a 10lb block of ice into 10lbs of 90degF water, that the 10lbs of ice will give off 2020 (1440+580) BTUs of energy.

So, at first glance, everything looks like it should work perfectly, and you should be perfectly comfortable in your deer blind when it is 90 degF outside.

But, remember from my previous blog post about BTUs, TIME is the factor to keep in mind. In this case, the online calculator said 2000 BTU, but remember that is actually 2000 BTU/hr.

So in that case, it looks like at first glance you would need 40 lbs of ice. But again that assumes that it will be 90 deg F the entire 4 hours. It also assumes that you as the person will be giving off 250 BTU/hr as body heat, which it will probably be more than that when you first sit down due to sweat etc., but then later will be less due to being sedentary. The online calculator also assumes "comfort" which isn't defined, but can be assumed to be a temperature of about 75deg F.

So you can see that there are a lot of assumptions and calculations. But, once you factor in the time of day, and the daily temperature changes, and the body heat etc., one can see that approximately 20-30lbs of ice is needed for this application, which in ballpark terms is about 3.5 gallons of ice.

Which is the approximate capacity of your new 5 gallon bucket air conditioner!

Perfect fit!!

So, to answer the question of does it work? In this application, a 6x6x6 deer blind 90degF outside and 30lbs of ice, it will keep you comfortable for approximately 4 hours. So, YES, is the answer to the "does it work" question for this application.

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This is the first blog in a series of short articles that will answer these questions. I am a chemical engineer and I will try my best to explain the nuances and the physics, in plain language, so that I can educate each of you on this simple yet very complex question.

Do you want it to cool down your whole 2000sf house 20 deg F in 10 minutes? In that case, it doesn't work.

Do you want it to keep your deer blind "comfortable" so that you don't sweat up a storm baking in the heat? In that case it works perfectly.

Do you want it to keep a room in your house cool? Well it depends on what you mean by cool, and how big the room is etc.

Do you want it to keep your van/trailer/tent cool at night? Depends on a lot of factors, but yes in most cases.

So, as mentioned in the previous blog post, there are a lot of factors to consider in the question of does it work. I will over the next few weeks, work on trying to sort out the complexities of temperature control, humidity control, thermal efficiency, portability, power consumption, solar affect, expectations, BTU output, etc.

So, that by the time I'm done, each and every one of you will be able to definitively answer for yourself, and for your own application, on whether a 5 Gallon Bucket Air Conditioner will work for you!

]]>Today we will be talking about BTUs, what they are and why they are important.

BTU = British Thermal Unit.

In engineering terms, it means the amount of "heat energy" required to raise one pound of water, one degree Fahrenheit.

But, what does that REALLY mean?

When you go to a home improvement store, and you see a portable air conditioner, and it says that it is a 10,000 BTU unit, what does that really mean?

First off, there is one important term left out of the marketing of air conditioners. A 10K BTU AC, means what? It is missing a time component. Think about it for a second, in the terms of cooling capacity. 10,000 BTUs of heat (cooling) energy produced is what the marketing materials say. But, the big factor that they DON'T SAY, is OVER WHAT PERIOD OF TIME.

For instance, if I say that I have an air conditioner that is a 10K BTU unit, but it takes 14 hours to drop the temperature 5 degrees F in a 15 x 15ft work space vs. a 10K BTU unit that can drop the temperature 20 degrees in 15x15ft work space in 1 hour, which is the "better" unit, they are both 10K BTU units? Obviously the one that cools the space more and faster right?

So, that is a little marketing trickery that an educated consumer needs to be aware of.

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While my team and I were researching various vapor generation technologies, we came across some old cold war era studies, calculations, and experiments performed by Army researchers in some recently declassified research studies.

We performed our own studies and analysis, and using modern computer modeling, and computational fluid dynamics, we greatly improved on the over 50 year old studies, and designed and built several dissemination systems that are still being used today in the US Army testing and research centers.

It is this technology and background that I am taking out of the annals of US Army research, and bringing into the commercial world.

I am currently applying for patent and intellectual property rights protection for this proven technology.

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