Outdoor Assisted Cooling

This is not an area of expertise for me, but isn't that what heat pumps do?

I don't think so. I'm no expert either, but I'm talking about taking the compressor completely out of the loop in cold weather.

http://en.wikipedia.org/wiki/Heat_pump

http://www.ferrocement.com/casa-ca10/ch10.en-ferroHouse-web.html

like this perhaps?

Excellent article HUX, and exactly what I was thinking. I knew I couldn't have been the first.

In this age of "green" thinking, and constantly rising energy costs, this seems like a no brainer. The money and energy saved by retrofitting our cold storage units to utilize the outside cold air during winter, I would think would be astronomical.

Could be a very lucrative business opportunity too.

I have been acting on this in my own small way for several year. I pre-cool all my store bought "warm" beverages - bottled water, juices, etc... before I put them inot the fridge. This helps both energy costs, and prolongs spoilage of sensitive dairy products (milk, yogurt...) by limiting temperature fluctuations. My wife thinks I am nuts, but every little bit helps.

Great Idea for expanding this into a commercially viable sector.

Shawn

For the married, male CR4 users, I think that having wives that think we're nuts is a fairly common condition..............Welcome aboard!

PS- The one's that don't have wives that think they're nuts, usually have ex-wives that think they're nuts.

I think a thermostatically controlled air exchanger, that satisfied any local health codes, got the job done, and enabled the fairly large compressors to be off-line for a good part of the year would be pretty easy to design and implement. I also think that such a unit would sell itself.

My ex-wife thought I was nuts!! After we split, she went back to school, got a degree in software engineering and Guess What...

SHE'S NUTS!!

Bill

You have to realise that during the heating season, most of your appliances and lights run for free!

Could you please forward that memo to my power company? I don't think they got it.

Since the heat released by your fridge and TV stay in the house, your heating system works less. The fact that your energy bill goes up in the winter is from the loss of heat of the house, not your appliances consumption.

If you want to reduce your energy bill, insulate your house better and keep the doors /windows closed...

If your house is air tight, install an air exchanger with energy recovery to keep a good air quality in the house. It will use some energy but will save on medical expenses.

RE: You have to realise that during the heating season, most of your appliances and lights run for free! The heat that they release reduce your heating needs. There might be a small effect from heat distribution efficiency or cost of heat source but you save most of it.

There's something wrong with this answer, and I'm trying to figure out what it is and state it clearly. Yes, the waste heat from your appliances and lights goes to heat the house, so that is good. So, would it make sense to run (for example) 1000's of watts of lights to heat your house from the waste heat?

It really depends on other things.

One being (like marcot says) on whether you need heat or not--if you can keep your windows open year round, the waste heat we're talking about is something you might even have to pay to get rid of (in the form of air conditioning or ventilation fans).

If you do need heat, then whether the waste heat from the refrigerator is economically useful to you depends on the cost of your primary source of heat. For example, if you heat the house with free wood, then there is an extra cost associated with running a refrigerator to get "free heat"--that extra cost is greater than the cost of heating with free wood.

Aside:If it makes economic sense to run an appliance to add to the heat in your house, a refrigerator might be a particularly good one, because as others have said or implied, it is essentially a heat pump--for a given amount of electricity, you may get a little more heat than strictly based on the BTU value of a KWHR. (This from the heat extracted from the refrigerator.)

Still, I think it will not be very significant--you are not extracting much heat from that already cold refrigerator--maybe someone with enough analytic ability can quantify this for us. (Thinking about it some more, there may be so little heat extracted from the refrigerator that maybe you won't get more heat than strictly based on the BTU value of a KWHR.)

Even here in NC we get a lot of nights in the teens and low 20's. An over simplification, but as far as controlling the incoming cold air and temperature, I don't think it would require much more than a thermostat, an inlet and exhaust fan and an on/off switch. Of course it would have to be tied into the existing cooling system, with auto shut off when outdoor temps get too high.

I think it would save a considerable amount of electricity, but I have a feeling that it hasn't been pursued commercially, because it can't be patented, and therefore can't be monopolized. Just a guess.

Maybe it's not worth it, but it sure does seem like it would be cheaper to move cold from outside in, than to make cold using a compressor. I'll have to poke around on the internet and see what the power consumption is for commercial refrigeration units.

Re: In general, heat pumps are very efficient; so my somewhat educated guess (but yeah, still just a guess) is that the energy used to properly control the outside environmental 'cold' used for refrigeration would be more than the net 'heating system plus refrigeration system' energy.

I wouldn't think so if the energy used is just that to run a small solenoid or actuator to open and close a damper (or two) (in one or two short small ducts to the outside).

Kramarat, shouldn't you think of your refrigerator as being a heat pump that pumps the heat out of your food and into the rest of your house? Just another system to warm you in the cold winter months?

That is a correct way of looking at it. However, considering that I keep the house close to 70° F, and my refrigerator is a cold box sitting in the middle of the house, it's hard for me to look at it as a heating unit, even though that's technically correct, I think the heat output is negligible.

Especially when I'm paying money to run it and the outdoor temp is in the mid teens.

I guess we need the fridge stuck into (and through) a north facing wall with some sort of insulation that automatically drops off or flips open when it is cold out. Sometimes it might open at night when it is cold and close up in the day.

Nah, if you wanted to do it, I think it could be accomplished with a couple of lengths of 1/2" insulated PVC going to the outside with an extremely small fan on the inlet side, controlled with a thermostat.

Hi Gaia,

We use what we have until we can pay for it. We start to improve or change when the old we cannot afford, and go for the next but never before.

More than 70 years ago, we have a small room, around 3x3=9 square metre, used to maintain its temperature equal to the outside. For months, we have the only fridge.

LEED construction helps to solve these questions but we don't use very much. Check out if is good for you, Gil.

I'll agree that the heat output is negligible, but that means you are not pumping much heat! i.e. you are not expending much energy cooling the innards of the icebox.

Hands down, the best bet is a properly insulated refrigerator. It's a remarkable analog to heating your house. Insulation, per penny, is by far the best investment to reduce your heating costs.

Coal fired power plants used a system where the combustion air is preheated from the flue gas using a rotary exchanger. I think that is in line with the idea.

Okay, I found an illustration, scroll down to Rotary Regenerators

The system you have in mine may very well save energy. But is it cost effective. You would be incorporating two systems into the basic unit one for cold months and one for hot months. Today they are contained units wheel them in and plug them in to AC and go. Now it would have to be connected to another source. Something that would have to be maintained by the home owner. Also something the manufacture would have a problem with covering under their warranty. As they have no idea of the state of the coolant you will be running thru the unit. You may be looking at double the cost of the unit. A 22cf refrigerator cost on average about $100 a year to run. So you in your new system we'll cut that in half. $50 savings if we ignore the power consumption of the pumps to feed the new system. Just bought inexpensive new fridge for work a scratch and dent model cost was $500+. If double the cost for your new system would have it run for 10 years to recoup any savings.

You're right, I don't think it would be feasible for the home refrigerator, and not something the manufacturers would be interested in. But when I walk around a grocery store, in particular, and look at the rows and rows of coolers, freezers, meat lockers, etc. and think of the average winter time temps across most of the US and Canada in the winter time, for up to 6 months, I can't help but think that we are wasting a valuable resource that is held in that outside sub freezing air.

I haven't had a chance to look into the cost of running these commercial cooling units, but I would think it would be substantial, especially considering that we are simultaneously heating the inside of these buildings.

In a commercial establishment, the efficient heat pumps in the coolers and reefers heat the building, and little extra heat is required. In the SUMMER, the excess heat is verrrrry bad, requiring air conditioning units to work twice as hard. Smart stores have roof mount condensers.

That makes sense, I guess. I didn't realize that the compressors for the coolers and freezers in a grocery store ran hot enough to heat the entire store, with just a little supplemental heat. I always figured they had heaters going full blast, especially when the outdoor temp is below freezing and doors are always opening.

So by maintaining the temperatures of the coolers and freezers at the desired temperature, heating the store is almost free? That is efficient!

In fact, the heat generated by the compressor and motor is proportionally quite small. Remember we are talking about heat pumps here, that literally move heat from one place to another. Most of the heat emitted by the condensor coils has been removed from the regrigerated zone by the evaporator coils-pipes. For example, if the fridge in my kitchen is chucking 600watts of heat out the back, 400 to 500watts of this is heat that has been extracted from inside the fridge and pumped back into the kitchen, from whence it came when the fridge door was opened. So it is just recirculating heat, and generating very little.

I was being a little tongue in cheek. I believe what ormon is saying is probably accurate, but that it would mostly apply to places like California, where temps don't get that cold. Much of the US gets very cold in winter, where I think a system like we're discussing would save real money. But I don't have any numbers to prove it.

Considering the number of times I've managed to stick my foot in my mouth, I need to relax on my comments until I have some time to look around and find some facts.

Thanks for the input.

The cost of air ducting would be sizable. The fan horsepower would probably be less than the hp of the compressor, but I'm not sure by how much.

I don't know if it would be feasible everywhere, but think of your typical grocery store here in the US. All of the large walk in coolers/ freezers are in the back of the store. Whether they permeated the roof or the back wall, it wouldn't be that much duct work. I think fan size could be pretty small.

Think about every 7-11 and convenience store across the US that would fall in areas where outdoor winter temps get cold. The walk ins are almost always on a back or side wall. Say they need to maintain them at 40° F and outdoor temps in winter get into the 30's for a high during the day. They are heating the inside of the store and have big, inefficient glass doors on the outside of the cooler letting in heat every time they're opened. How could a couple of fans on the exterior back wall not save a lot of electricity? They would have to be on a dampered system though, to prevent the space from getting too cold.

I'm a regular at the convenience store up the road from me. He uses fluorescent lighting, and really the only other electricity usage would be his large walk in coolers. I'll ask him what his monthly bill is. Maybe they have the large commercial cooling units so efficient that this whole idea is folly.

Combined heat power cycles, ( CHP),Heat pump, Heat recovery wheels, Natural ventilation, Mechanical type ventilation are some of the terms used to utilize the available energy in optimum means.

So glad somebody brought this up.

My plan years ago, when I was still living in a place that had winters, was not to bypass the vapor-compression mechanism completely but to build a "chimney" that would bring in outside air to cool the condenser coil of the 'fridge. The chimney would seal around the refrigerator and be insulated so as not to cool the living space. The compressor would still operate, but would draw less power because the thermal gradient would be less, or even negative. During summer the chimney would still be used because exhausting the refrigerator heat outdoors would reduce the cooling load for the living space. I never did it because I never owned the places where I lived, so I couldn't make the necessary modifications. Here in the Philippines I'm thinking of cooling the condenser coil with cool water from a stream.

I built a pantry for my home using two outside walls and well insulated on all four and door, using a 5k air conditioner in the summer and outside air in the winter when it was time to stock up food. It saved space and winter the food was around 35 degrees and come summer the beer stayed aroun 40 on the floor. Food remained fresher year round. Little extra work but built it with used material, garage sale air contioner. Saved on space, money and food expense..Size 6' by 4'..

Good thinking! I really see no reason why this wouldn't involve savings on a larger scale.

A lot depends on how big your fridge is, and whether it is located inside or outside. For a new build (such as jtd405s) or a commercial walk-in fridge this could make sense, but if you are talking about modyfying or supplementing a domestic fridge in your kitchen, I doubt it is worth the effort.

My fridge uses about 180w (or possibly less), which equals about 4kWh per day if run continuously. Assuming it runs about 25% of the time, then about 1kWh per day. If the system and weather were good enough to allow me to rely entirely on outside air for 3 months of the year, my average daily consumption would drop to 0.75kWh, a saving of 0.25kWh.

I doubt that this would justify the hassle & expense, and, as has been pointed out (in a fashion) by marcot, you would also lose the heat being recirculated back into your living space (which might even be greater in energy terms than any savings from not running the compressor).

Yeah, marcot is right......you too. It wouldn't be worth it to retrofit a household refrigerator, but I think it might be for large commercial units and walk ins.

My perspective is a little different.............I heat with wood. The house is nice and warm, so every time I hear the refrigerator running, from my perspective, it's fighting to keep itself cold against a warm house.

I have nothing to complain about. I just got the electric bill yesterday for my 2000 sq ft house, $59 including tax.

Days in period 31

Total kWh 550

Daily average 18

Not bad. I'll have to see if I can track down some numbers on the large commercial units and see if I can't narrow it down a little on feasibility.

What is even more crazy is cooling commercial walk-ins and warehouses - places the public doesn't go.

I found some pertinent information. My electricity is costing a little over .10 per kWh right now.

I was also mistaken in my thinking that an outdoor assist unit would have to be tied into the main cooling unit electronically. The on cycle would just have to be set about 2° lower than the one on the heat pump. Duh! Also, an exhaust fan would not be necessary.................the inlet would blow in outside cold air at floor level, and it would simply exhaust through an opening in the ceiling going back outside.

http://oee.nrcan.gc.ca/industrial/equipment/commercial-refrigeration/index.cfm?attr=5

Based on this, I think a large part of the US, and almost all of Canada could benefit from outdoor assist systems. Relatively small fans, with a high cfm rating could keep these indoor coolers and freezers cold for most, if not all of the time, while the large, power hungry heat pumps and compressors sit idle. In the spring of the year, the relatively small openings required would be plugged with insulated plugs until the following winter, and traditional cooling methods would be used. ( This is a NOAA map, no copyright infringement)

We're spending a lot of time trying to find new ways to feed our hunger for energy, and not enough time figuring out how to do the things we already do......smarter.

Now imagine being able to practically shut down your heat pumps and compressors for 6 months of the year, and cooling your spaces with one of these. This is a 12" inline, but I think they could be even smaller.

http://www.industrialfansdirect.com/IND-FA-T-T/LFI-DDA12T30033BM.html

You are right on. In non-residential facilities, "free" cooling has been utilized for years...it's known as an "economizer cycle" which will kick in automatically when there is a call for cooling and the outdoor temperature is low enough, say 55F. The compressors are turned off and the system will circulate outside air to provide indoor comfort. Geothermal systems are becoming very prevalent. They use subterranean ground water or the earth itself as a "heat sink" and extract heat from it for heating and reject heat to it when cooling. With these systems compressors are still required but they will operate at a more economical level.

Food storage is a more complicated animal. One savings the super markets have been using for a long time is that of using the heat from the air cooled condensers serving their coolers and freezers to heat the occupied areas. Their profit margins are typically so slim that they don't miss a beat in saving another penny here and there.

Well, here it is in action. As far as my question about why it isn't in greater use, I think it's mainly because this guy has created a system that's initially quite expensive to install. I don't think it has to be expensive, either.

Originally, I thought it would have to be electronically tied into the primary controller for the main system, which he has done here. But by lowering the switch on temp of the outdoor assist unit just 2-3° lower than the primary system, I think it could operate independently and be just fine, as well as way cheaper.

http://www.youtube.com/watch?v=Hh5-zrNW_N0