Turning Roof Into Absorption Chiller

regworth: Glad to meet you again at the forum, nevertheless I will counter your approach to the problem as usual;

There can be stormy days with no sunshine say during a whole week that means the entire lot of meat in the storage might go to the garbage dump on at least a couple of occasions in an year.

More sensible approach to me is that you should consider co-generation in case steam is required for the processing or a gas turbine to run the conveyors, use of a Diesel Generating set is simpler and reliable on the face of it.

Usually the utilities are obliged to provide different tariffs for industrial and lighting loads, if that is the case in Bali; split the load and apply for a seperate tariff metering (new connection) for the lighting and office loads, in this case it would be the liability of the utility to arrange for the transformer or an additional feeder.

Thank you, it's always a pleasure to consult with you clever folk in this forum and it's good to be back. And you are right - despite Bali's reputation as the sunshine capital of the planet, we do get monsoon season every year and in that there are inevitably a few days of total overcast. In fact, this year we had rain all through our 'dry' season if you can believe it! Weather patterns are indeed changing over the last few years. I initially had recommended considering a hybrid system because that is what I thought would be the most prudent in this situation. The customer had applied for and been approved for the additional power, so I thought that if it's there as a back-up and they have the traditional cooling gear in place, there is no problem. On the days that need it, the system kicks in with full power from the utility and they have no loss of valuable inventory. However, they called me the other day and said that when they heard the costs PLN was going to levy for just installation, not even considering the monthly fees, they said thanks and passed. So, they really do need a solution now and one that will keep them operating rain or shine. Given this, I'm inclined to agree that a gen-set is required, but I'd still like to look at what type of system could be engineered to get them a good deal of the way there from thermal on the rooftop and then supplement where necessary with the traditional cooling equipment. Now the question comes down to the best and most cost effective approach to getting this in place.

This would probably be an ammonia/water absorption system. I don't know if a passive solar system can attain high enough temperatures to be effective, which might need a focused solar collector system.

The 80 kva is not a very large system, and may not justify the amount of customized design that is likely to be needed. I hate to sound pessimistic, because I think there could be good research in this direction. However, I'm inclined to agree with mountk2 and go for a genset and conventional compressor system.

CR4 member mrswamy may know of some applications from the mideast, if he joins this thread.

I do agree that a gen-set is probably mandatory now given that they will not be taking the utility upgrade for power. Initially it looked more promising because they would have the cooling power in place to take on whatever levels were required once the absorption chiller had done all it could - and in the case of an overcast day or days, the system would be more than capable of handling full duty. But with only 23 Kva from the utility, we do have to ensure that the plant remains functional during days when the absorption chiller is sidelined. For the moment, this means a gen-set on stand-by for either situation. What I need to do though is evaluate what savings could be realized if, say, the absorption method managed up to half the duty cycle and the other gear took care of the rest. Or maybe we could achieve 60 - 70% with the absorption? At this point I don't know enough and I also would need some assistance with what the best method is to off-set the traditional cooling as much as possible. So, I will hope that mrswamy or some others who are savvy on this subject drop in for a comment or two.

Some thoughts....

a) I will assume that the 80KVA will only be required for short intervals...

b) That there are supplimentary intermediate stage cooling methods available - by chilling your refrigerant with evaporative methods - before expanding it....

c) Increasing your insulation.

d) Using low energy cooling in the slaughtering rooms and dressing / boning areas - to drop the temperature from ambient by 10 - 20*C - in the form of a one way air conditioning system.

e) Spend $45K on solar cells / solar concentrator (microturbine generator)...

f) Use a set of thermal surge tanka - like a 10,000 liter or 20,000 liter insulated water tank that is kept as a "negative thermal capacitor" of cold evaporative chilled water AND then another tank of very very cold water or subzero brine - to prechill your refrigerant - and to increase it's capacity to cool.

g) Look up some of the adsorbtion or absorbtion chillers in commercial use.

There are lots of ways to make better use of what you have; and to increase the efficiency of it's use.

Air chilling meat from 30*C to 15*C by evaporative chilling as an intermediate step is a cheap and easy way to reduce the refrigeration costs by about half....

Thank you - a lot to consider here. Couple of things I'd like to explore if you don't mind - c) Increasing your insulation - this is one area I had already suggested they address - the building is the usual warehouse approach here in Bali with batako brick walls and they haven't done anything extra to insulate further. Inside the walls are clad with white ceramic tiles. Given this construction it's not so easy to inject an insulating layer into the brick, so I would expect that the exterior walls could take an insulating layer on the outside of the building and interior walls would need to be dealt with on interior of chillers - any suggestions for this and what material is the best insulator for this purpose? e) Spend $45K on solar cells / solar concentrator (microturbine generator)... this is what I was hoping to get around with the existing roof generating decent levels of thermal heat from solar and one thing I was considering is a copper tube radiator layer on the roof with small pump circulating the fluid through. Does this one make sense or too little return for the effort?

Thanks Mr. Gene. I am very happy to hear from you after long time.

Though solar energy is available throughout the year in middle east countries as on date its application to air conditioning is very limited. During recent years governments in these countries have taken some initiatives to explore the possibilities of using solar energy based cooling systems in GCC countries.

One of the professors from U.K in his report on Global Renewable Energy Forum reported that driving factors such as the sharp increase in oil prices, high demand for coal coupled with limited supply, implication of climate change and pressure to reduce harmful gases, concern over nuclear proliferation, high coal price and policy change, and world demand for high energy consumption etc will force the countries throughout the world to bring about a radical shift in investments in favor of cleaner, more efficient and more secure energy technologies. The United Nations Environmental program identified three of the GCC countries as those with the highest per capita energy consumption in the world, and furthermore concluded that the six GCC countries contribute approximately to 45%–50% of the cumulative Arab countries' CO2 emissions. A research scholar has recently carried out an analytical review of the current renewable energy sources in the GCC region, and concluded that these countries are available to use solar applications for the following applications:

· Solar home systems in order to provide power for domestic lighting and other DC appliances such as TVs, radios, sewing machines, etc.

· PV modules for lighting especially for homes and community buildings as well as to telecom towers.

· Solar cooling systems for commercial applications, such as supermarkets, theatres and cinemas, since air-conditioning is one of the largest electricity consumers in the region.

· Solar water heaters to reduce electricity consumption in water heating sectors for many hot water domestic and industrial applications.

· Large solar power plants supplying off-grid desert communities

In South Africa a renewable energy company Voltas Technologies has installed, and is monitoring, a solar-thermal driven air-conditioning system at the Net care Moot hospital, in Pretoria. The solar plant is situated on the roof of the Moot hospital, and the air-conditioning absorption chiller unit is powered by hot water, which is heated through 50 collectors. These solar collectors operate at 91% efficiency, and the water can reach temperatures of up to 120 ºC.The absorption chiller is powered by solar energy collected in the evacuated tube solar thermal panels. The thermal energy is delivered to the absorption chiller using a Glycol (antifreeze) solution and a simple, but carefully designed, system of pipes, pumps and controllers. Engineers from Turkey designed a system using solar energy in combination with Aquifer Thermal Energy Storage (ATES) to provide heating and cooling to the hospital by storing solar heat underground in summer and cold in winter. It is reported that by implementing this project the savings in fuel oil (1000 m3/year) will approximately decrease the CO2 emission by 2100 tons/year, SOx by 7 tons/year, and NOx by 8 tons/year. The replacement of 2 MW of current chillers using Freon-12 will result in a saving of approximately 0.7 tons/year of Freon-12.I have carried out many feasibility reports to use solar cooling systems mainly combining solar collectors and absorption system. 19th century was the age of coal and the 20th century is the age of oil and 21^st century will be the age of the sun and absorption system with Li Br water system driven by solar energy has got good market potential.

I am also fascinated with the concept of using heat for an absorption chiller, especially since heat is our largest natural resource here in south Texas. I would like to harness the sun for domestic cooling, since when the available heat is the greatest the largest cooling load exists.

Considering a generator set, it seems very inefficient to connect an engine to spin magnets to make electricity which goes to a motor to spin magnets to turn a compressor. It would be much cheaper to both obtain and operate an engine-driven refrigerant compressor.

That's a very good point - optimizing the system will be one of the key considerations to realize the greatest gains in cooling while using the least amount of power possible. Aside from the chiller rooms, there isn't a great deal of peripheral equipment drawing significant power so the rooms are truly our main challenge here. I will factor your suggestion into whatever system evolves as the most feasible and see if we can't bypass the need for a gen-set.

Hi Regwoth,

I am not expert on this subject but I recollect one of the research institute in India had developed cheapest method for cooling homes in rural areas. It had suggested of covering the roof of the homes with jute bags/mats and sprinkling of the water on these bags. This has resulted in evaporation of the water leading to cooling effect inside the homes.

I dont know if this may be of any interest to you but you can give thought to it because I think your customer has limited funds to spend.

Hi Suresh, that is a very interesting approach to cooling interior space in hot climates - thank you for pointing it out. In this situation, I'm looking at not just reducing the ambient temperature in the building by a few degrees (although I'm sure the workers in these areas would greatly appreciate it) but to drop temperatures in the chiller rooms down significantly so that conventional cooling equipment already in place can take them the rest of the way using minimal energy. This means capturing the heat that exists at roof level and redirecting it to an absorption system that is designed to chill and deliver the coolant to whatever distribution system is employed. Having said that though, you do certainly make a good point about how simply we can use whatever materials are around us to provide an inexpensive, effective solution in certain situations.

While the absorption chiller is interesting, one could look at a standard compression heat pump with a COP of 3 to 4 to do the same from the present electricity source. You might end-up using less electricity than with the absorption chiller.

If you use the heat output to provide the hot water needed in the plant and maybe the neighborhood. The dense population of India would make it possible to distribute (sell) the surplus hot water.

You could also use the heat produced by the generator for the same application.

The cold side would run the freezers as it normally do.

This is less risky and can produce a symbiosis with the neighbors (industrial or not).

If you do use an absorption chiller, consider using the hot water produced by your generator or the neighbors.

Another source of heat is the exhaust of air conditioners. I use mine to make house hot water and to heat the pool during our relatively cool summer days.

I see a recurring theme in your reply and it's a good one - look at available energy that's already there on the site and make sure it's not wasted. If there's a gen-set running that means there's heat energy that can be captured - if there is another process that produces energy and it's just dissipating into space, grab it. That practice alone is enough to save many businesses thousand per year. However, the one I'm most interested in is one we don't produce ourselves through a process - it's there all the time and we are only beginning to realize it's potential. I'm speaking, of course, of the sun and this is the main issue I"m trying to explore right now - can I get there using passive solar or do I need PV to optimize it's potential? Is there a way to think outside the box and come up with an innovative approach to harnessing all that energy to produce heat without the high investment in PV panels? It may well turn out the answer for the moment is no - but that is why I'm putting this out there - so that a lot of innovative and creative minds may trigger some thought that leads to a solution or points out some existing technology that could be combined to get the job done.

Your concept is interesting, as you already know sunshine is not consistent. A Gen set is the next option. The question is what fuel do you plan to use? If you have a lot of waste heat from a gas turbine, than this can be used to run an absorption chiller.

A storage system of chilled brine cooled either from the roof of the waste heat chiller will allow you to cover the gaps between low electrical loads and lack of sun.

This will be a hybrid system that will take a lot of thought and money.

In rough numbers, an evaporative cooling tower can achieve temperatures a few degrees (say 5-10°C) above the local wet bulb temp.

A lithium bromide/water chiller, water being the refrigerant, has an evaporating temperature above freezing, and achieves chilled water of about 10°C. This is suitable for air conditioning, and maybe some product pre-cooling, but is not adequate for lengthy product storage. It has the advantage of not needing a very hot regenerator temp, and thus might work with passive solar collection.

For temperatures below freezing, ammonia/water works; but I think it needs a hotter regenerator temp than passive solar can produce. Thus the possibility of focused solar.

These are just preliminary ideas. I've engineered lots of compressor systems, but no absorption setups.

Hi Tornado, coming back after a couple of heavy weeks of project deadlines but I hope we can pick-up and take this a little further. One thing I've done during the hiatus is narrowed down the possible options for the system in question to a hybrid approach. With a low-pressure pump feeding a radiator tube array on the corrugated tin roof (with southern exposure) we should be able to attain daytime temps for the solution of near 80 C - enough for the lithium bromide chiller to keep room temps inside the chillers at 15 C and this is the temp most of the rooms require. A couple others need 0 C and one needs -22 C. I'm looking at using the 23 Kva power with existing equipment to cool those rooms the additional 15 and 37 degrees respectively but should use far less energy to do this as all the rooms will achieve ambient temperature from the absorption chiller of 15 C. This should translate to significant savings long-term as they will not have had to increase their power from what they use now and will likely require much less of that power to get their colder rooms to the desired temps. For evening hours I've learned that they do have a smoker and the process heat from this can be taken to a heat exchanger to deal with keeping the solution temp at a consistent 80 C. That's where I'm at to this point - if you have other thoughts on changes / improvements I'm interested in looking them over?