Assessment of Propane Fired Gas Air Conditioning, Heat Pumping and Dehumidification Technologies, Products, Markets and Economics Submitted to:

Transcription

1 Assessment of Propane Fired Gas Air Conditioning, Heat Pumping and Dehumidification Technologies, Products, Markets and Economics Submitted to: Mr. Gregory Kerr Director of Research & Development Propane Education & Research Council Street: 1140 Connecticut Ave. N.W Connecticut Avenue, NW, Suite 1075 Washington, DC Technical Review for PERC by: Richard Sweetser President EXERGY Partners Corp Meadowville Court Herndon, VA Submitted by: Dr. William Ryan Energy Resources Center The University of Illinois at Chicago Energy Resources Center (MC 156) 1309 South Halsted Street, 2nd Floor Chicago, Illinois January 19, 2007

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3 Table of Contents Executive Summary... vii Introduction and Focus...1 What is Gas Cooling?...1 Report Approach...1 Chapter 1: Gas Cooling Technology Background...3 Overview...3 Lithium Bromide Absorption Chillers...3 Operation...3 Lithium Bromide Absorption Chillers Application...3 Large Lithium Bromide Chiller (> 100 RT) Markets and Economics...4 Small Lithium Bromide Chiller (< 30 RT) Markets and Economics...5 Ammonia Water Cooling Systems...6 Absorption Chillers...6 Ammonia water absorption heat pump...6 Propane Firing...6 Issues with Small Absorption Chillers...6 Ammonia Water Refrigerators...7 Engine Chillers...8 Operation...8 Engine Heat Pumps...9 Issues with Engine Heat Pumps...9 Operating Engine-Driven Chillers and Heat Pumps on Propane...10 Solid Desiccant Systems...11 Operation...11 Propane Firing...11 Desiccant System Applications...11 Recent Developments in Solid Desiccant Systems...12 Liquid Desiccant Systems...14 Chapter 2: History and Issues in Gas Cooling Development...15 The Origins of Gas Cooling...15 The Residential Gas Air Conditioning...15 Specific Developments and Lessons Learned...17 Engine Heat Pumps...17 Triathlon...17 Thermo King...18 Goettl...18 Page: iii

4 Desiccant Systems: A Different History...19 Chapter 3: Propane/Gas Fired Cooling Equipment...20 Commercially Available Cooling Equipment...22 Broad 4.5 RT Double Effect HW Chiller...22 Rotartica...23 Robur Air Conditioning...24 Robur Heat Pump...24 Yazaki Energy Systems...26 Cooling Systems under Development...27 Ambien Heat Pump/Cooling System...27 Chemisorption Systems...28 Cooling Technologies Cooling System...29 Energy Concepts, Inc Thermax Ltd (Thermax-USA)...31 GEDAC Engine Heat Pump...32 Propane Refrigerators...33 Propane Refrigerators...34 Commercially Available Desiccant Dehumidification Systems...35 SEMCO Revolution...36 Munters...37 NovelAire Residential Gas-Fired Dehumidifier...38 Desiccant Dehumidification Systems under Development...39 Mississippi State Residential Desiccant...39 Kathabar Liquid Desiccants...39 AIL Research Liquid Desiccant Development...41 Chapter 4: New Applications for Propane Fired Cooling...43 The Hotel/Resort Market for Desiccant Dehumidification...43 Remote Eco-Tourist Hotels...44 Heat Pump Swimming Pool Heaters The Snowbird Desiccant Dehumidifier...45 The Remote Vacation Home...46 High End Homes with Unreliable Electric Supply...47 Chapter 5: Propane Opportunity in CHP with Thermally Driven Cooling...48 Smaller Reciprocating Engine Generating Systems...50 Hess Microgen...50 Coastintelligen...51 Tecogen...51 Microturbine Generators...53 Page: iv

5 Capstone Turbine...54 Ingersoll Rand...54 Elliott Microturbine...55 Small Generator Summary...55 Application of Thermally Driven Cooling to On-Site Generation...56 Applied Systems...56 Packaged Systems...56 An Economic Overview of CHP on Propane...58 Appendix: Available State and Federal Incentives...60 Chapter 6: Economic Analysis of Propane Fired Air Conditioning...61 The Economic Situation...61 Using the Economics Charts...62 Economic Analysis of Cooling and Heat Pump Systems...65 Propane Air Conditioning in a Conventional Application...66 Propane Fired Heat Pumps...68 The Commercial Rooftop Market for a Propane Heat Pump...73 Economics of a Commercial Heat Pump...73 Business Issues in the Commercial Rooftop Market...77 Third Party or Propane Dealer Financing...78 The Third Part Financing Proposition...79 Economic Analysis on Desiccant Systems...80 Opportunity...82 Snowbird Residential Desiccant System...83 Heat Pumps with Heat Recovery...87 Operation...88 Economics...88 Economic Proposition for the Propane Dealer...91 Chapter 7: Summarized Results and Suggested Directions for Propane Driven Air Conditioning Development and Commercialization...94 Opportunity Summary...94 Suggested Research and Development Directions Propane Commercial Engine Driven Heat Pump Snowbird Desiccant System Desiccant Hotel Dehumidification Propane Fired Absorption or Engine Driven AC in Off-Grid Homes Propane Fired Cooling with Heat Recovery...96 Opportunities Noted that Do Not Involve Propane Fired Cooling...97 Markets Not Recommended...97 Page: v

6 Propane Absorption Heat Pump...97 Propane Engine Driven AC...98 Propane Fired Absorption AC...98 Off-Grid Propane Driven Cogen & Cooling...98 Suggested Directions for Additional Market Research...98 Market Forces Affecting Propane Fired Cooling Deregulation and the Condition of the Electric Generating System in the US The Condition of Propane Supply Appendix 1: Desiccants and Energy An Example Movie Theater in a Humid Climate Ventilation Air Summary Appendix 2: Glossary Page: vi

7 Executive Summary This report is an overview of the current opportunities for the propane industry for gas cooling. Available equipment, current developments, and national economics are pulled together to find areas where propane can serve as the fuel of choice for cooling systems. This involved understanding that 1) exploiting existing equipment is more practical than expensive completely new research developments, 2) the propane dealer must have a reason for promoting any resulting systems, 3) customer must have a good reason to want the system and, 4) that customers are motivated by economics, enhanced comfort or other specific benefits. Specific markets are summarized in the table on the next page. Markets were selected based on operating costs, enhanced customers features and first cost. The chosen markets in priority order are: 1. Propane Driven Engine Driven Heat Pump and Propane Absorption Heat Pump (Residential Cold Climate Market, All Commercial Markets) Both systems reduce winter propane load and expands summer load. Equipment includes the GEDAC, Aisin Seiki, and Yanmar engine heat pump. Opportunities include Dealer Finance Packages for Commercial Applications. 2. The Snowbird Desiccant System (Southern Humid Market) Using a propane fired desiccant dehumidifier to preserve unoccupied humid climate homes in the summer without running air conditioning. This provides customer savings and enhanced dehumidification during occupied periods. 3. Desiccant Hotel/Resort Dehumidification (Southern Humid Market) Using a propanefired desiccant system to dehumidify ventilation air, reduce indoor humidity, odors, and mold, and preserve furnishings. Currently available equipment uses solid desiccant wheel technology with future opportunities in more efficient and compact liquid desiccant systems. 4. Propane Absorption AC with Heat Recovery (Hot Climate Market) Propane-fired air conditioning system capable of recovering heat for heating loads such as domestic hot water or pool heating. 5. Propane Driven AC in Off-Grid Homes and Off Grid Propane Driven Cogeneration Cooling (For Remote Locations Not Served by the Electric Grid) Both systems improve the economics of providing modern comforts to residences and small commercial buildings where connection with the utility grid would be either impossible or expensive. All of these opportunities are based on the adaptation of existing equipment and have the potential for near-term addition to the propane load and to the number of propane customers. The following tables summarize these opportunities. Table 1 shows the potential technologies and Table 2 shows the potential return to the propane dealer from added propane load from these new system. In the Opportunity Summary section of Chapter 7, an estimate is done of what a market roll out of one of these technologies could benefit the overall propane industry. In the example, the sale of 100,000 engine heat pumps to customers in mild climates that would have otherwise used electric heat pumps would be a total 10 year revenue addition of $741 million, and an estimated margin addition of $95 million. Page: vii

8 Market Market Size Operating. Cost on Propane Equipment Available Maintenance Needs First Cost Premium Better Comfort Propane Load Added MARKETS RECOMMENDED Snowbird Desiccant System Desiccant Motel Dehumidification Commercial Engine Driven Rooftop Heat Pump (GEDAC System) Engine Driven Split System Heat Pump (Aisin Seiki Type) Ammonia Absorption Heat Pump Ammonia Absorption AC in Off-Grid Homes Bromide/Water Absorption AC: Off-Grid Homes Gas Engine Heat Pump: Off-Grid Homes Off Grid Propane Driven Cogen & Cooling Propane Absorption AC with Heat Recovery MARKETS NOT RECOMMENDED Propane Engine Driven AC Ammonia Absorption AC Lithium Bromide/Water Absorption AC On Grid Propane Driven Cogen & Cooling Large Region Niche Good Fair Poor Domestic Foreign Develop Low Fair High None Yes High Yes No Good Fair Poor Table 1: Summary of Technologies Page: viii

9 Customer New Technology Conventional Technology Return to Propane Dealer Per Unit Type and Climate Heat Cool Type Heating COP Cooling COP Propane Use Propane Use Added Propane Use MBH RT Gal./Yr Gal./Yr Gal./Yr Residential Hot Propane Residential Mild 80 5 Heat Pump Residential Cold Furnace/ AC Furnace/ AC Furnace/ AC Residential Hot Elec. HP Propane Residential Mild 80 5 Heat Elec. HP Pump Oil Residential Cold Furn/AC Commercial Hot Propane Commercial Mild Heat Pump Commercial Cold Commercial Hot Propane Commercial Mild Heat Pump Commercial Cold Gas Rooftop Gas Rooftop Gas Rooftop Elect Rooftop Elect Rooftop Elect Rooftop Residential Hot Humid 400 CFM System Snowbird System 200 Elect. AC /Dehum Commercial Hot Humid CFM System Desiccant Ventilation Dehumidifier 3600 Elect.AC /Dehum Margin Calculation at $0.25 per Gallon Equipment Life Assumed to be 15 Years Table 2: Summary of Propane Dealer Financial Opportunities Page: ix

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11 Introduction and Focus Both large and small scale fuel fired cooling systems have had a long history of application across wide areas of the built environment. The focus of this report is on smaller scale cooling and dehumidification systems and technology from larger systems that might scale down to sizes applicable to residential and/or light commercial propane-based systems. This report reviews existing and emerging gas cooling systems 25 refrigeration tons (RT) and below and reviewing technologies between 25 RT and 200 RT that could be adapted to residential and light commercial loads would be most amenable to propane firing. What is Gas Cooling? The expression Gas Cooling or Gas Air Conditioning is more a marketing term than a technical one. Over the years, Gas Cooling has come to mean any gaseous fuel driven system that can produce either sensible cooling, or dehumidification. As a gaseous fuel driven system, the most historically prevalent fuel has been natural gas. However, the market for propane fired systems, which will be largely where lower cost natural gas is not available, is less widely explored. Technologies included under the heading of gas cooling are: Absorption chillers and Heat Pumps Engine chillers, air conditioners, and heat pumps Desiccant dehumidification systems Report Approach This report is divided into distinct chapters: Chapter 1: Gas Cooling Technology Review which will cover the fundamentals of the processes and description of available technologies. Chapter 2: History and Issues in Gas Cooling Development includes general market data and reasons for success/failure to penetrate the markets. Chapter 3. Products and Current Developers of Gas/Propane Fired Air Conditioning - covering specific product and technologies providing Consumer Reports type assessment of each product/technology. Chapter 4. New Applications for Propane Fired Cooling Chapter 5. Propane Opportunity in CHP with Thermally Driven Cooling Chapter 6. Economic Analysis of Propane Fired Air Conditioning Chapter 7. Summarized Results and Suggested Directions Page: 1

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13 Chapter 1: Gas Cooling Technology Background Overview The technologies applied to Gas Cooling are diverse. Absorption and engine driven chillers, heat pumps and desiccant cooling/dehumidification systems are the main technical approaches. In this chapter, the basics of these technologies will be reviewed to provide the appropriate technical background for the report. Lithium Bromide Absorption Chillers Operation In a conventional electrically driven cooling system, a refrigerant is boiled at a very low pressure. At low pressure, the refrigerant boils at a low temperature, producing a cooling effect. The refrigerant vapor is then compressed to a high pressure in an electrically driven compressor. At this high pressure, the refrigerant will condense at higher temperature and reject the heat to the outdoor environment. The liquid refrigerant is then passed back to the low pressure and the process continues. Figure 1 - Vapor Compression Cycle Absorption chillers use a heat driven chemical process to completely replace the electrically driven compressor in an electrically powered cooling system. Two chemical are involved in any absorption chiller. One chemical, the absorbent, is distilled by using heat from a fuel. This occurs in the generator. This purified solution then absorbs the second chemical, a refrigerant vapor, at a very low pressure. This occurs in the absorber. Once the refrigerant is absorbed, the chemical passes back to the generator and the refrigerant is boiled out at a high pressure. In this way, the heat activated chemical process moves the refrigerant from a low to a high Figure 2 - Absorption Cycle pressure and replaces the electrically driven compressor. Lithium bromide absorption chillers are available in two versions. One is a lower efficiency single effects cycle which can operate on low temperature heat. These are used today for producing cooling from waste heat streams, particularly from cogeneration systems. The other is a higher efficiency double effect absorption cycle, which is operated either on high pressure steam or directly fired by a fuel burner. Lithium Bromide Absorption Chillers Application Lithium Bromide absorption chillers are typically applied to large commercial buildings. These systems are used to produce chilled water which is then distributed throughout the building and used to cool air via remotely mounted water cooled coils. Lithium Bromide Water Chillers are Page: 3

14 capable of Coefficients of Performance 1 of up to 1.0 (direct-fired). These systems require a cooling tower to reject heat to the environment. Cooling towers which are typically used in large buildings are less common in small applications because of water use and maintenance. The exception to this is Broad Air Conditioning, which has developed a 4.4 to 30 RT product line with integrated cooling tower which the claim requires only annual maintenance. Large Lithium Bromide Chiller (> 100 RT) Markets and Economics Lithium Bromide chillers are produced by all the major American HVAC equipment manufacturers including Trane, York, and Carrier, and have been traditionally used in areas where summer electric power is expensive, where gas company programs encouraged their use, or where electric service was too limited for electric chiller use. Currently, the largest domestic applications are replacing existing chillers, where summer steam is abundant (New York City), where waste heat streams are available Figure 3: Absorption Chiller for Larger Commercial Buildings (Courtesy of York International.) the use of large power consuming electric chillers that operate during the summer, which tends to be the highest electric demand period of the year. Absorption chillers are more expensive than electric chillers. In larger sizes, single effect absorbers tend to be roughly 25% more expensive and double effect absorbers roughly 100% more expensive than standard efficiency electric chillers. The current North American market penetration of large absorption chillers is roughly 5% of the overall market for large chiller systems. At current fuel prices, application of absorption chillers today tend to be only where summer electricity is (processes) and where on-site generators supply waste heat that is used to power the chiller. Globally, absorption chillers are used where regulation or rates discourage Figure 4: First Costs Per Ton of Capacity of Large Chillers extremely expensive, in particular the large urban areas along the East Coast or where a waste heat stream that can be used to drive an absorption chiller at low cost. The most common waste heat stream is heat rejected from power generation in cogeneration (CHP) systems. The future market potential for large absorption systems depends on the future course of electric deregulation and energy prices. Open electric contracting is becoming an opportunity in industrial and commercial markets. Commercial buildings draw a summer peak power demand that exceeds the peak demand throughout the remainder of the year. Open contracting for electricity, depending on the structure of the contract, may make covering this cooling system peak expensive and motive more sales of absorption chillers to operate on any available fuel natural gas, propane, or oil, depending on availability. 1 The Coefficient of Performance, often referred to as the COP, is, in this case, the amount of cooling developed per unit of fuel or heat input to the absorption chiller. Measuring the amount of cooling and heat input in Btu/Hr results in a COP value that is dimensionless (a simple ratio) Page: 4

15 Small Lithium Bromide Chiller (< 30 RT) Markets and Economics Small Lithium Bromide absorption machines are now being produced by foreign suppliers. The Broad small absorption chiller, a Chinese product, is shown in Figure 5. Another innovative system being produced in Spain is the Rotartica unit. The Rotartica system is only recently entered the market and should, at present, be considered a development effort. Figure RT Lithium Bromide Chiller (Courtesy of Broad.) Figure 6: Rotartica Cooling System (Courtesy of Rotartica.) Page: 5

16 Ammonia Water Cooling Systems Absorption Chillers Ammonia Water Absorption chillers have been traditionally used for small cooling systems. These systems also produce chilled water but use an air cooled condenser coils for rejecting heat to the environment. This allows these systems to be packaged into the same type of small air cooled outdoor units common on residences or small commercial loads. Popular in the 1960 s, these systems fell out of favor in American residential air conditioning due to low efficiency and high installed cost. Coefficients of Performance of 0.65 are as high as has been achieved in production systems to date. There is only one European supplier of these systems. Ammonia water absorption heat pump The sole manufacture of ammonia water air conditioners, Robur has, has Figure 9: Small Ammonia Water Gas Heat Pump (Photo Courtesy of Robur) Figure 8- Small Ammonia Water Gas Air Conditioner (Photo Courtesy of Robur) recently introduced a heat pump into the market. Information published on this heat pump indicates that heating efficiency can be as high as 140%, based on fuel consumption. This technology may be of interest to the propane industry. Although a heat pump would reduce fuel used during the heating season, the fuel used to meet air conditioning loads during the summer would, in most cases, increase the annual fuel usage. In addition more of the fuel would be used in the cooling season and less in the high demand heating season. Propane Firing Large absorption chillers are either fired by a boiler or are direct fired by a gas burner. By using the appropriate burners direct fired units can be driven by natural gas, propane, or even fuel oil. Steam driven units can be driven by a boiler burning any fuel. The small ammonia water absorption chillers discussed above, are currently available from the manufacturer with either a natural gas or propane burners. Issues with Small Absorption Chillers Smaller absorption chillers have had a traditional challenge with electric chillers and air conditioners based on high first cost and a lack of sufficient operating cost savings to produce a reasonable payback. In addition, the installation service network for small cooling systems is unfamiliar with absorption systems, which can make both installation and maintenance costly. On the positive side, absorption systems can often be left for long periods without regular maintenance. Page: 6

17 Ammonia Water Refrigerators Absorption or a gas refrigerators were common in the domestic market before Absorption refrigeration cycles are still produced in volume in both the United States and Europe, for use in three markets. One is the recreational vehicle market. Absorption refrigerators are used in recreational vehicles as they can be operated on either electricity or propane. Recreational vehicles operate the refrigerators electrically while is on the road, and switch to propane while the vehicle is parked, thereby saving the battery. The second market for absorption refrigerators is hotel room refrigerators and mini-bars. Absorption refrigerators have no moving parts and therefore operate soundlessly. This is a substantial advantage in the hotel rooms. In these applications, the refrigerators are operated by electricity. The third market for absorption refrigerators is for remote locations such as cabins and campgrounds. A number of manufacturers make refrigerator that resemble residential Figure 10 - Modern refrigerators for these applications, all Propane Refrigerator for propane fired. Residential Use (Courtesy of Danby) Absorption refrigerators use an ammonia water cycle, similar to the ammonia water absorption cycles discussed previously. Instead of having a solution pump or any moving parts, small refrigeration cycles use natural recirculation to send solution around the system. The cycle requires only a source of heat to operate. When driven by propane, a small burner is used. A resistance heater is used when the cycle is driven electrically. The use of propane to operate small refrigerators suggests expanding to other propane applications based on similar consumer needs. Mobile refrigeration on a small scale can be met by this type of refrigeration cycle. In general, the cycles are used only when the overall cooling load is less than a 1/2 of one ton of refrigeration. In addition, these cycles are not as efficient as larger ammonia water absorption chillers. However, the simplicity and long life of the cycle with no moving parts, often makes up for the low efficiency in smallscale cooling applications. Figure 11 - Drawing of the Absorption Cycle Loop on a Propane Refrigerator (Courtesy of Danby) Page: 7

18 Engine Chillers Figure 12 - Large Engine Driven Chiller for Use in a Larger Commercial Building. (Photo Courtesy of York International) Operation Another approach to gas cooling is to use the same cycle as an electric air conditioning system with a fuel driven engine to drive the compressor, replacing the electric motor. With such a system, a Coefficient of Performance as high as 2.0 is possible. Engine chillers have been built in large sizes for commercial building with some domestic marketplace success. Systems down to 15 tons have been produced though the smallest size currently available is 50 RT. When built in smaller sizes, the systems are put into an air cooled package that sits outside the customers building, provides cooling water, and requires no cooling tower. Coefficients of Performance in Cooling for smaller systems are generally in the 1.0 to 1.2 range. Two manufacturers, York and Tecogen have been producing engine chillers for the last ten years. Although not new, these chillers have only achieved a minimal penetration into the market. Figure 13 - Small 50 ton Air Cooled Packaged Engine Chiller for Smaller Scale Application (Photo Courtesy of Tecogen) Page: 8

19 Engine Heat Pumps During the 1980 s, in parallel with the development of engine chillers, a number of small scale engine heat pumps were developed for the 3-50 ton market. These systems are air cooled and directly replace electric heat pumps. These small systems have not been successful to date in the United States although over 40,000 systems have been installed in Japan 2. Figure 14 - Engine Heat Pump in Operation (Photo Courtesy of Yanmar) Unlike engine chillers, engine heat pumps provide both cooling in the summer and winter heating. Heat rejected by the engine allows engine heat pumps to provide efficient heating at lower outdoor temperatures than electric heat pumps. Although an engine heat pump will add propane load during the summer, the heating function is generally at COP s above 1.0, and therefore will not add as much propane load in the winter as a conventional furnace. Engine heat pumps may be most attractive to the propane industry in areas where electric heat pumps are the major competitor for propane heating. Figure 15 - Schematic of an Engine Heat Pump (Drawing Courtesy of Advantica) Figure 16 - Mitsubishi Engine Heat Pump (Photo Courtesy of Mitsubishi) Issues with Engine Heat Pumps Although engine heat pumps can offer customers a more highly efficient system than absorption based gas cooling, the engine will require regular maintenance, including oil and spark plug changes. Significant progress is being made by engine heat pump manufacturers in extending these service intervals up to 10,000 operating hours. Unless these systems are maintained, they will be damaged or fail to operate entirely. Given that the electric heat pump and propane furnace service network is not attuned to doing essential maintenance, this can be a major cultural change in the distribution channel for heating and cooling systems. Propane suppliers may wish to provide or contract for this service to assure that proper maintenance is done, as well as develop a new line of business that with little expert competition. In this way, service contracts could be packaged with the overall sale and standard service charges might be included with the propane billing. 2 The Gas Heat Pump, Presentation by Colin Heap Advantica Technologies Ltd, UK Heat Pump Network 19th March 2002 Page: 9

20 Operating Engine-Driven Chillers and Heat Pumps on Propane Engine-Driven chillers and heat pumps have generally been operated on natural gas. In order to adapt the systems to propane, carburetion systems and engine timing would need to be adjusted to handle the different fuel chemistry. In general, operating on propane may involve some degrading of the engine, as propane may cause the engine to knock if not retuned. Page: 10

21 Solid Desiccant Systems Operation Desiccant systems are a variation in gas cooling. Desiccant systems supply pure dehumidification and are generally used in buildings that are otherwise conventionally cooled. Desiccants have particular advantages for any application that can gain from enhanced dehumidification over and above that normally done by conventional cooling systems. Applications include any building in a humid climate that requires significant amounts of outdoor air. Schools, movie theaters, and motels are major examples. Another market is any Figure 17 - Solid Desiccant Dehumidification System (Drawing Courtesy of Munters) Solid desiccant systems are composed of a solid desiccant material or material with a desiccant coating, often arranged into a wheel. Air passes through the majority of the wheel and is dehumidified. The wheel rotates slowly in the air stream as the humidity is adsorbed onto the wheel. To remove this water from the wheel, a small segment of the wheel is heated to drive the humidity off and away to the outdoors. The dried surface of the wheel rotates back into the air stream and repeats the cycle. Propane Firing Desiccant systems use the heat from a burner to generate hot air which is then used to drive the humidity off of the desiccant wheel. The fuel used in this burner application that can gain from very low indoor humidity like ice arenas and cold storage warehouses. Figure 19: Desiccant Wheel Structure (Drawing Courtesy of Novelaire) does not affect the process. To date natural gas is largely been used for this function. Propane can be used by equipping the system with the appropriate burner. Figure 18: Desiccant Dehumidifier Structured for Industrial Applications (Photo Courtesy of Munters) Desiccant System Applications Unlike engine or absorption cooling systems, which simply replace the electrically driven air conditioning or cooling system, desiccant systems are used specifically to remove humidity, thereby reducing the overall air conditioning load. In many applications the desiccant systems ability to reduce humidity to a greater extent than is possible with conventional air conditioning systems is a significant customer benefit. For instance, in ice arenas, desiccant systems are Page: 11

22 commonly used to reduce humidity to an extremely low level, thereby preventing condensation on the ice sheet. This improves ice quality and reduces the overall load on the refrigeration system used to maintain the ice sheet. In commercial buildings, the most common application for a desiccant system is to remove humidity from outdoor ventilation air. In humid climates, a large flow of ventilation will often build up indoor humidity to a level that cannot be adequately controlled by conventional air conditioning systems. By using a desiccant system to produce dry outdoor ventilation air, the cooling load is reduced and the tendency to build up humidity is eliminated. Figure 20: Desiccant Dehumidifier Structured for Treating Outdoor Air for a Commercial Building (Photo Courtesy of Munters) These applications illustrate that desiccant systems can be used to produce costumer benefits that can not be produced in any other way. Therefore, desiccant systems are often used in applications where their benefits exceed a simple operating cost advantage. This means that desiccant systems are often used where there is a need that extends beyond simple economics savings, for example in manufacturing production processes that require low humidity, in commercial buildings that can be damaged by humidity, or in commercial applications where customer comfort is the paramount concern. In these types of applications, desiccant systems are generally used regardless of operating costs. Recent Developments in Solid Desiccant Systems Enhancing the dehumidification capability of air conditioning with desiccant systems has broken down in recent years to three approaches. Each tends to be appropriate to different situations. periods. Figure 21: Passive Desiccant System (Drawing Courtesy of Munters) The first approached is passive desiccant dehumidification. In a passive desiccant dehumidifier, the desiccant wheel dehumidifies ventilation air as it enters the building. The desiccant wheel is then regenerated by using exhaust air from the building. Exhaust air at 70 F to 80 F will provide only a mild regeneration of the wheel, which in turn results in the wheel doing only a small amount of dehumidification of the air entering the building. Also, there is no direct control as to how much dehumidification will actually occur. However, in a moderately humid climate, a passive desiccant system may improve dehumidification adequately during hot summer The second approach, which has emerged in recent years, is using the heat rejected from a vapor compression (electric) cooling system to regenerate the desiccant wheel. This provides regeneration air to temperatures as high as 100 F to 115 F. As this is a higher temperature than the building exhaust air, the desiccant wheel is more thoroughly regenerated and provides greater dehumidification. However, there are three disadvantages to the system. First, the dehumidification provided by the system is still quite limited. The desiccant wheel is not capable of taking large amounts of humidity out of the outdoor air. Second, the desiccant wheel can Page: 12

23 only be regenerated when the air conditioning system is actually operating. This keeps the desiccant system from removing humidity during periods of cool damp weather. Third, there is no capability to independently control the degree of dehumidification that is occurring. As with the passive wheel, the customer must accept the amount of humidity removal being delivered Finally the most effective way of regenerating a desiccant wheel is to use a fuel fired heater. This allows regeneration air to be as hot as 150 F to 160 F. This hot regeneration air will dry the desiccant wheel thoroughly, allowing the desiccant wheel to provide substantial dehumidification. In addition, by using an independently operated fired desiccant heater, the dehumidifier can be operated at any time, whether or not the air conditioning system is in operation. This allows for independent control of humidity and temperature. In general, this type of system would be best justified in the most humid climates with the added benefit of being able to operate the during humid cool winter weather Page: 13

24 Liquid Desiccant Systems Liquid desiccant systems are also used for dehumidification, largely in industrial processes. Applications to commercial space conditioning dehumidification loads have been tested at a number of locations. Rather than using a desiccant wheel, a liquid desiccant system sprays a lithium chloride and water salt solution through the air stream to be dehumidified. As long as the lithium chloride concentration is high enough, the solution will draw humidity directly out of the air stream and into solution. Once the solution is diluted, it is taken to a regenerator. In the regenerator the solution is heated and sprayed through an outdoor air stream. The solution gives up moisture to the outdoor air and is re-concentrated and the cycle repeats. Figure 22 - Liquid Desiccant Dehumidification System Liquid desiccant systems have a number of advantages over solids systems. These include: Scalability: Liquid desiccant systems can be built to larger sizes and capacities than solid desiccant systems. As solid desiccant systems become larger, the size of the wheel becomes larger in diameter, finally reaching a size that is structurally impractical. Liquid desiccant systems have no such limitation Component Arrangement: A liquid desiccant system consists of two components, the dehumidifier and the regenerator, interconnected by piping. These two components can be located separately as is convenient for the installation. For instance, the dehumidifier could be located indoors near the area requiring dehumidified air and the regenerator located outdoors. In addition, if desired, a single liquid desiccant regenerator can be used to operate multiple dehumidifiers in a piped desiccant system serving a number of dehumidified air loads. Air Sterilization: Liquid desiccant systems spray a strong salt solution through the dehumidified air stream which has been proven to kill pathogens in the air, an advantage for medical applications. Higher Efficiency: Liquid desiccant systems under development have the potential to operate at higher energy efficiencies than that of solid desiccant systems by using heat recovery heat exchangers to reduce the amount of heat needed in the regeneration process. New System Designs: New heat exchanger designs for liquid desiccant systems, particularly those aggressively using plastic plate technologies, hold the promise of making these systems more compact and affordable and therefore more suited for commercial applications. Page: 14

25 Chapter 2: History and Issues in Gas Cooling Development The Origins of Gas Cooling Gas or fuel fired cooling systems have a history that goes back to the beginnings of the refrigeration industry. Early refrigeration systems developed in the nineteenth century used one of the two methods of operation. One was a conventional refrigerant system using a compressor not dissimilar to modern electric refrigeration systems. However, at that time, larger electric motors were not available and electricity was extremely expensive. These refrigerator systems were generally driven by steam engines which obtained their steam from a boiler, and were therefore fuel fired refrigeration systems. Absorption systems were also commonly used at that time, for low temperature refrigeration applications, mainly making ice. These absorption systems used acid solutions rather than the lithium bromide solutions used today. Absorption systems fell out of favor for ice making systems early in the twentieth century. However in the 1930 s and 1940 s, absorption was adapted to making cold water for air conditioning in large buildings. During that period, natural gas also became available in many large urban areas, replacing the far more expensive manufactured gas that had been previously used. At this point, absorption systems became a major player in the market for large commercial air conditioning. By the 1960 s, half of all large air conditioning systems sold in the United States were absorption chillers. Since that time, the market share has declined to roughly 5% due to advances in electric chiller design and reduction in electric prices in the 1970 s and 1980 s. The Residential Gas Air Conditioning Production of very small air conditioning systems for homes and small commercial applications began in the 1950 s. Electric air conditioning systems of the time were both expensive and relatively expensive to operate. The availability of extremely low priced natural gas made gas air conditioning an opportunity. Figure 23: 1960 s Arkla-Servel (Now Robur) Gas Air Conditioner Installation (Photo Courtesy of Robur) During the 1950 s, gas fired ammonia water absorption air conditioning system were developed by a number of manufacturers, most prominently Carrier, and introduced into the market. During much of the 1960 s gas air conditioning enjoyed a substantial market share. During the same period, the number of new homes built with central air conditioning systems expanded. There was a steady reduction in electric prices during the 1970 s which led to a larger volume of electric air conditioning systems being sold. This larger volume led to a substantial reduction in the first cost of electric air conditioning systems making the competitive market for gas air conditioning more difficult. Although a number of efforts were made to reduce the cost and increase the efficiency of gas air conditioners during this period, the overall result was a substantial first cost disadvantage for gas air conditioning systems by Page: 15

26 With the energy crisis of the 1970 s, new gas connections were curtailed in suburban areas where new homes were being built. The belief that natural gas availability was diminishing had more to do with the regulatory environment of the time than any real resource limitation. This was realized by the late 1970 s and new home construction was once again opened to gas connections. However, during this connection hiatus, new gas air conditioning system sales declined substantially. This led a number of manufacturers to leave the gas air conditioning market with only one manufacturer remaining by the 1980 s. This manufacture was later bought out by Robur, the one remaining manufacturing the small gas air conditioners today. During the late 1980 s and much of the 1990 s, the price of natural gas was in decline. This was particularly true for natural gas delivered during the summer. The predominant use for natural gas is heating. This means the natural gas was in substantial oversupply during the summer, which set the stage for low summer prices. In reaction to this, the natural gas industry once again began to promote the use of natural gas for air conditioning. At the same time, both the natural gas industry and the Department of Energy began work on natural gas fired heat pumps. The attraction of a gas fired heat pump is a higher level of the heating efficiency than is possible with natural gas furnaces, and the removal of summer cooling load from an overloaded summer electric generation and distribution system. Significant development work was devoted to gas heat pump technology during this period, with overall financial support from both the gas industry and the department of energy totaling in excess $50 million. One product that has been commercialized the from these efforts is the Robur heat pump The current environment for natural gas prices is far more volatile than it was during the nineteen nineties. Deregulated and open markets have affected natural gas prices. Higher oil prices have brought natural gas prices up, as many users have switched from oil to natural gas. The oversupply of natural gas in the summer is no longer as major an issue, as natural gas is now extensively purchased for storage systems during the summer, eliminating the much of the summer oversupply for natural gas. More natural gas is now used for generating electricity, particularly in summer. Page: 16

27 Specific Developments and Lessons Learned Engine Heat Pumps Triathlon The Triathlon was a 3 ton engine driven heat pump developed by the Gas Research Institute in the late 1980 s, commercialized by York International, and featured an engine built by Briggs and Stratton. Although over 3000 of the units were sold and installed, the product was not a success in the long run. Lessons learned in the overall development and commercialization include; The unit used a Briggs and Stratton engine developed solely for this application. During the commercialization process of a product of this type, sales volume was too low to make engine manufacturing practical. Figure 24 - Triathlon Engine Driven Heat Pump (Photo Courtesy of Battelle) Using an engine that is also applied in other markets would have helped generate greater production volume and lower production costs. Overall production cost of the product was quite high and the commercialization involved a subsidy from the gas industry. As this subsidy declined during the commercialization processed, the manufacturer attempted to go through a cost reduction process on both the heat pump system and the engine. Unfortunately, although early production units were extremely reliable, the cost reduction process affected reliability of the unit. Subsequent unit failures in the market were a major cause for the unit to be withdrawn. The dealer network was a major problem in the commercialization. Installers were unfamiliar with the usual installation process involved and mistakes were commonly made. In addition, the unusual installation process prompted installers to charge a substantial installation premium. A gas heat pump product with an installation process that is typical of other products in the industry would have aided commercialization During the commercialization process, it became clear that customers desiring this heat pump were early adopters interested in the technology. This group tended to be composed of more affluent customers who possess larger homes than could be easily handled by a three ton heat pump. Unfortunately due to the dedicated engine, it was not practical to expand the product line to a larger size range as a new engine would have had to have been developed. Using an existing production engine line might have allowed for greater ease in increasing the size of the product to conform to these homes. Page: 17

28 Thermo King The Thermo King unit was brought out at the same time as that of the Triathlon. Thermo King is a major manufacturer of engine-driven refrigeration systems for use in mobile applications such as refrigerated trucks. Thermo King undertook the development of a rooftop style 15 ton commercial cooling system based on their existing refrigeration packages. Figure 25: Thermoking Engine Driven Rooftop AC (Photo Courtesy of Thermoking) Goettl Taking lessons learned from the Triathlon product development, Goettl air conditioning developed an engine heat pump in the late nineteen nineties. Goettl is a regional air conditioning manufacturer in the southwestern United States. Goettl developed and commercialized a 15 and 20 ton engine driven roof top heat pump. The engines were supplied by Volkswagen Industrial engines. This avoided the complexity and expense of developing a proprietary engine, and allowed for a number of sizes to be built. More importantly, as these engines are sold into the industrial market for multiple uses, Goettl could obtain the engine in low volumes, as needed, without concern that the engine manufacturer would drop the engine line. Unfortunately, the Thermo King package was quite expensive. Thermo King s manufacturing approach was industrial in style, using more expensive materials that are common in the HVAC industry. Thermo King ultimately decided that the profit margins in the HVAC industry were not sufficient to maintain their interest in the product, in comparison to the higher margins in their normal refrigeration business. Figure 26 - Goettl Engine Heat Pump (Photo Courtesy of Goettl) Ultimately, Goettl decided that the sales volumes were not sufficient to maintain their interest and the product was dropped. However the use of an existing engine line and a more conventional rooftop installation approach were of value in this product introduction, as many of the problems seen with the Triathlon were avoided. Page: 18

29 Desiccant Systems: A Different History The history of desiccant dehumidification systems is considerably different than that of other gas cooling technology options. Desiccant systems began almost entirely as industrial equipment. When dehumidification is provided by conventional air conditioning systems, the removal of moisture from the air is a byproduct of the cooling process. In many applications, there is a desire for dry air to dehumidify, without reducing the temperature of the space. This is one of the prime applications of desiccant systems in industrial processes. Desiccant systems also allow humidity to be reduced to a level that cannot be supplied by conventional air conditioning systems. Some manufacturing processes require extremely dry environments to operate properly, and desiccant systems are essential in these processes. The first major application for desiccant systems in the 1930 s was cargo preservation. By dehumidifying the holds of ships, cargoes sensitive to humidity could be carried without damage. After the Second World War, desiccant systems became widely applied to preserving the ships themselves. A large number of naval vessels were placed into storage at the end of the war, generally at storage docks, and desiccant systems were widely used to prevent internal rusting. Further industrial applications were developed throughout the 1950 s and 1960 s. Desiccants became common for providing very dry air for pharmaceutical pill packing operations, chocolate preservation in candy manufacturing, and a number of other specific manufacturing applications. Beginning in the late 1980 s, the gas industry began to see desiccant systems as a gas cooling opportunity. Desiccant systems were extensively explored as a potential air conditioning system, in which the desiccant system would be teamed with an evaporative cooler to provide a full fuel fired air conditioning system. However the overall cost of desiccant materials and the size of the resulting air conditioning systems made this approach impractical. Starting in the early 1990 s, a new focus for desiccant systems was found. Desiccant systems were targeted to provide highly dehumidified ventilation air for commercial buildings. Specific commercial building applications where humidity posed a problem were selected. The most successful of these applications is in ice arenas and supermarkets. By the late 1990 s, a large segment of the new ice arena market was using desiccant systems to provide ventilation air. In addition a number of major national chains began to specify desiccant systems for new supermarkets in humid climates. Page: 19

30 Chapter 3: Propane/Gas Fired Cooling Equipment A survey was done on small capacity fuel fired cooling equipment that is currently available on the global market. This survey included absorption chillers, engine driven chillers, engine heat pumps, and desiccant a dehumidification systems. A large number of systems are available globally; however, many of these systems are in a larger size range that is of interest for this report. A table of the available small systems can be seen below. Manufacturer Cooling Capacity (RT) Vol. ft 3 /RT Type lbs / RT $ / RT Cooling COP Hot Water Input Cooling Water Use (GPM/RT) Propane Fired Broad Bromide 207 $2, Direct Fired 3.5 Rotartica Bromide 751 $17, F None Robur 3 ACF NH $1, Direct Fired None Ambien 5 NA NH 3 NA NA ~0.7 Direct Fired None CoolTec NH $1, Direct Fired None Yazaki 10 Bromide F 3.5 Thermax Bromide F 3.5 Propane Fired = Current Unit is Hot Water Driven = Current Unit is Gas Fired Could be Converted to Propane = Propane Version Available Status = In Development = In Production Table 3: Small Lithium Bromide and Ammonia (NH3) Chillers Status Manufacturer Cooling Capacity (RT) Cooling COP Heating Capacity (MBH) Heating COP (Eff) $/RT lbs / RT Propane Fired Heating Type Status Robur Robur 5 GAHP-AR % $1, %- 140% 126.2% $2, Ambien NA 140% NA NA Propane Version Heating Type Status = Currently Gas Fired Can be Converted to Propane = Propane Version Available = Chiller/Heater = Heat Pump = In Development = In Production Table 4: Small Absorption Cooling/Heating and Heat Pump Units 3 Robur Sales Literature 4 Robur Sales Literature 5 Robur Sales Literature 6 Ammonia Absorption Technology Development for Air Conditioning Heat Pumping and Refrigeration, Distributed Energy Peer Review 2005, DOE Page: 20