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Recover waste heat from a curling rink refrigeration plant.

Recover waste heat from a curling rink refrigeration plant.

Recover waste heat from a curling rink refrigeration plant.

(OP)
An interesting problem.
In our local community hall and curling rink, electric energy is used to run the ice plant. Natural gas is used to heat the community hall.
Is it feasible to recover heat from the ice plant to heat the community hall?
Yes I realize that in extremely cold weather there is not much waste heat available.
But, is it possible to effect enough savings in the milder months to realize a reasonable payback period?
Is it feasible to estimate the running hours of the plant from back copies of the power bills? (I think so, but has anyone done this?)
At this point I am wondering if there is enough probability of a good result to continue investigating.
I don't want to start bothering volunteer trustees for information if there is not a reasonable chance of success.
Thanks in advance.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Recover waste heat from a curling rink refrigeration plant.

If there is an engine running, there is potential to collect waste heat. How feasible that is for your application depends on the size of the engine, how long and when it runs, how much heat you need to do you some good, when the heat is needed and what you must do to recover any excess heat and deliver it to your consumer's location. Some basic data would help in determining if there is any potential to move forward.

What power bills do you have?

you must get smarter than the software you're using.

RE: Recover waste heat from a curling rink refrigeration plant.

(OP)
Hello BigInch. The curling rink and the community center are in the same building. There is an electrically driven refrigeration compressor to freeze the ice sheets for the curling rink. Thr compressor discharges hot gas to a condenser.
My thought was to add a heat exchanger and use glycol to transfer the captured heat to a radiator type heat exchanger in the building heating system ducts.
The greatest part of the electric consumption is running the refrigeration plant. I would estimate an allowance for circulating pumps and fans.
The greatest part of the natural gas load is heating the building.
My thought was to compare the monthly consumption of electric energy and of natural gas to get an idea of any energy overlap.
I expect that in the coldest months the natural gas consumption will be high while the ice plant will be running very little.
However there may be some useful overlap in the spring and fall.
Thanks for your reply.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Recover waste heat from a curling rink refrigeration plant.

You might possibly try to limit the system to pre-warming inlet air going into the existing heating system by ducting the engine exhaust through the heating air intake flow, making a kind of air/air exchanger, installing fans in the lower temperature building air intake ducts. Keeps it simpler by avoiding all the pump, energy for moving liquids around and the expense of the glycol exchanger and piping, which would be of higher pressure, more leakages, etc. A carbon monoxide detector and autoshutoff might be something you'd like to consider. Maybe overkill, not sure, but it seems like a good idea to me.

you must get smarter than the software you're using.

RE: Recover waste heat from a curling rink refrigeration plant.

You are on the right track for analysis. Electric bills would probably good enough to decide if it's not worthwhile. Probably need more detailed information to determine if it is worthwhile.

A google search for "skating rink heat recovery" returns many results, including this: http://www4.uwm.edu/energy/PETTIT/StudentFinal/Was...

RE: Recover waste heat from a curling rink refrigeration plant.

What ever you come up with, you need to be able to switch it off in the summer.

RE: Recover waste heat from a curling rink refrigeration plant.

Unless you want a heated wading pool.

you must get smarter than the software you're using.

RE: Recover waste heat from a curling rink refrigeration plant.

" Keeps it simpler by avoiding all the pump, energy for moving liquids around and the expense of the glycol exchanger and piping, which would be of higher pressure, more leakages, etc."

Definitely simpler, apart from having to install an engine in place of the electric motor. flowerface

Sounds like an interesting idea Bill. What is the discharge temperature of the compressor exhaust? Where does the condenser reject heat to at present - an air-cooled radiator or fin-fan bank? Could you substitute an indoor fan-coil to work direct from the hot(?) condensate, with the excess heat being rejected to atmosphere(?) as at present?

forum403: HVAC/R engineering might give you a thumbs up / thumbs down opinion on the idea before you get to the point of expending money.

RE: Recover waste heat from a curling rink refrigeration plant.

(OP)
Thanks for all the help friends. This is just in the concept stage in response to comments at a community gathering concerning the high cost of utilities to run our small local curling rink and community hall.
I understand that at one time a natural gas powered internal combustion engine was used to drive the compressor but it was replaced with a new electrically driven compressor some years ago.
Thanks for the link, MintJulep. It looks promising. I haven't had time to review it in depth but I will.
Hi Scotty. I agree that a direct condensate unit heater would be the most efficient,
BUT; I am hesitant to have refrigerant leave the machine room in a facility that is vacant much of the time and has minimal mechanical supervision by volunteers.
I will have to find out what the discharge temperature is. Systems that I am familiar with generally discharge at high enough above 100 deg.F to make heat recovery feasible but I am painfully aware that the discharge temperature at an ice plant in the winter may be so low as to make the idea a non starter.
As a back-up idea we may be able to use lower temperature energy for freeze protection of the community center during vacant periods.
I don't want to ask for more information from the committee members unless the idea has a reasonable chance of success. I would rather have my friends here shoot me down than to get hopes up in the community and then fail to deliver.
Although our community is tiny, we are in oil patch country and have a good selection of qualified tradesmen (electrical, instrumentation, and welding and fitting.) to tap for volunteer labour and several community minded oilfield service companies who may be willing to help with expenses.
I visualize a heat exchanger added to the hot gas discharge, a pump and a fin fan type unit heater. Add a glycol reservoir, glycol pump and some controls.
Thanks again for the suggestions.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Recover waste heat from a curling rink refrigeration plant.

Don't know how applicable it would be in your situation, but I once was involved in the installation of an air compressor that had a oil cooler where we ducted off the oil cooler into the warehouse type building it served. Had a diverter in the duct so that in the summer that hot air stayed outside but in the winter it would be blown into the building. If your ice plant has (or could be given) a radiator for disposal of its waste heat, that could be ducted into the make-up air for the building heating.

RE: Recover waste heat from a curling rink refrigeration plant.

(OP)
Thanks David. That's the kind of synergy I am hoping to achieve.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Recover waste heat from a curling rink refrigeration plant.

It looks like you have a couple of options, one is air with ducting off the condenser coils, the other is diverting the hot refrigerant to a second set of coils somewhere in the heating circuit using hot gas bypass valves or similar devices.
The unknowns are: Does this arena use ducting , or unit heaters. Is it a Freon type system , or ammonia?
B.E.

You are judged not by what you know, but by what you can do.

RE: Recover waste heat from a curling rink refrigeration plant.

First you need to calculate how much heat is available for recovery from your refrig unit, determine what that heat is costing you to provide with natural gas, and do the calc. to see how much capital you have to spend on whatever changes you will be doing.

What I suspect you'd be doing in this case is just wasting electricity, running your refrig plant less efficiently by driving up your cold sink temperature, reducing the EER of the heat pump. You'd be using more electricity in the coldest months of the winter than you are now, because instead of rejecting heat to the cold outdoor air you'd be rejecting it to the warm indoor air. The extra electricity you're going to use, which was probably generated by burning natural gas, is in that case being used to save the burning of natural gas to generate low grade heat- something you are already generating from natural gas with relatively high efficiency.

RE: Recover waste heat from a curling rink refrigeration plant.

(OP)
Thanks berkshire:
Given the consequences of a possible refrigeration leak in the heating system, not just the effects of the gas but the cost of replacement, I will have to go with an indirect system. Depending on the physical layout we may be able to effect cost reductions by using some ducting with an indirect system.

Good call molten metal:
I remember years ago taking a attending a short seminar on energy efficiency. An example was given of a school in a northern community which implemented a system of cutting corridor lighting between classes and reducing classroom lighting near the windows when sensors indicated lots of sunlight.
This was in an area where the heating season overlapped most of the school year, electricity was cheap and heating oil was quite expensive.
I asked a question similar to yours, are we saving cheap electric energy and replacing it with expensive oil heat energy.
No answer.
But in answer to your question:
I will certainly be guided by your reminder. There is no doubt that there are BTUs being rejected to the atmosphere by one system while BTUs are being produced by another system. The first question is, can these BTUs be harvested. The second question is, will the cost of the inefficiencies of harvesting outweigh the cost of the BTUs replaced.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Recover waste heat from a curling rink refrigeration plant.

How's the building's insulation doing?
Probably save more money with double glazing and another insulation layer in the attic, etc.
I doubt that is the elegant solution you were looking for, but it should always be the first order of business.

you must get smarter than the software you're using.

RE: Recover waste heat from a curling rink refrigeration plant.

I didn't sift through all the posts above, so forgive me if I repeat someone else's thoughts.

I think the most cost effective solution would be to insulate the refrigeration room, and depending on how the heat is expelled from the compressor, install a standard HRV (Heat Recovery Ventilator)on the air intake going to the existing heating system.

Discussion:
-The HRV would be installed upstream of the current heating equipment, with the hot side input coming from the compressor room and the cold side input coming from the current air source (recycled, exterior, where ever)
-Cold side output goes to the current heating equipment, hot side output to atmosphere (hoar frost warning, danger, danger)
-The HRV would simply pre-heat the input air for the current heating equipment, giving you some savings
-This doesn't have the high cost of a more efficient glycol solution, but you will lose out on some potential heat transfer
-would require a (potentially new) fan to be installed to force air movement to the HRV from the compressor room, and could need a booster fan for the air input depending on new piping route needed / losses through the HRV
-Air fan for compressor room could be linked to the current heating controls (or just use a pressure sensor in the ducting to know when it is pulling) to allow you to only have the fan on when the furnace is going; letting you 'store' heat energy in the compressor room

This is getting more and more redneck as I type so Im gonna leave it here - happy curling. If you want a really neat side project to impress your curling buddies look into making an automated pebbler for one of the ice surfaces. The ice keeper might tell you to take off though. It was a fun pet project of mine a couple years back.

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