Energy Efficiency Through Waste Heat Recovery Heat Recovery Centrifugal Chillers and Templifier Water Heaters
Innovative Solutions for Saving Energy McQuay offers two innovative methods of saving energy by obtaining hot water from the cooling cycle or other waste heat source: the Templifier product and Centrifugal Chillers with Heat Recovery Condensers. Both products save significant energy by converting readily available or usually discarded heat to more useful, higher temperatures for efficiently heating the building or domestic hot water. The Coefficient of Performance (COP) concept is what makes these systems economically practical. They offer COPs ranging up to 8 or higher; meaning that when one unit of purchased electric power is combined with seven units of waste heat, the result is 8 units of useful heat. A Cost-Effective Investment for Your Application In the right applications, the savings from waste heat recovery can have a payback of less than two years. In addition, ASHRAE 90.1-1999 Energy Standard (6.3.6.2 Heat Recovery for Water Heating) requires that recovered heat be used for service hot water heating and reheat in many buildings. Elevating water temperatures from a ground source to higher temperatures for space heating Applications where fossil fuel is not economical, available or desirable for emission reasons Economic Considerations For heat recovery chillers to be effective, a sufficient quantity of chilled water load is required when heating is required. Templifiers require a continuous source of lower temperature waste heat when higher temperature heating is needed. For example, a hospital is an excellent candidate where continuous simultaneous heating and cooling occur. Hospitals have large domestic hot water needs and large amounts of conditioned outside air. Conversely, a department store is not a candidate for heat recovery or a Templifier unit. The store is either heating or cooling (rarely simultaneously) with small domestic water heating loads. Any application requiring heat is a candidate to reduce energy costs with Templifier units or heat recovery centrifugal chillers. Domestic hot water for hotels and laundries Industrial processes requiring both heating and cooling or having a source of waste heat Hospitals and other health care facilities Make-up air for schools and factories Reheat applications for humidity control including museums and art galleries Heat source for the central loop of a water source heat pump system Facilities with high domestic hot water usage, such as hotels, can benefit from the energy savings in condenser water heat recovery systems. 2
McQuay Templifier Water Heaters A unique solution for efficient hot water heating Templifier Water Heaters remove heat in their evaporator from a waste heat source. By using the mechanical refrigeration cycle, the low-grade heat in the evaporator is increased to a higher, more useful temperature in the condenser and delivered to the heat load. A common application is to use the leaving condenser water from a traditional chiller at 95 F (35 C) as the heat source. The Templifier unit can then elevate the waste heat temperature and supply heat up to 160 F (71 C), efficiently making this hot water available for many practical uses, while reducing energy costs. Comparing Reciprocating and Centrifugal Templifier Water Heaters Reciprocating, Model THR Centrifugal, Model TSC Heating Capacity Range 500 to 3,000 MBH 3,000 to 24,000 MBH 150 to 880 kw 880 to 7,000 kw Maximum Hot Water Temperature 160 F (71 C) 140 F (60 C) Refrigerant R-22, R-134a R-134a Both Heating and Cooling Available Yes No Templifier Water Heater Benefits Can recover large amounts of heat that would otherwise be rejected from the building and then use it for either building heat or domestic hot water heating. Heats water more economically than fossil fuel fired boilers or electric resistance heaters. Can off-load overloaded boilers and/or cooling towers, thereby delaying or eliminating a capital expenditure required to increase their capacity. 3
Templifier Water Heater System Operation The system above is typical of a Templifier Water Heater recovering cooling load heat rejection from a conventional chiller s condenser water on the way to the cooling tower. The unit is sized to meet the heating load and often takes only a small part of the condenser water flow; consequently, the bypass line around it. The cooling tower rejects any leftover heat to the atmosphere. Templifier Water Heaters are controlled by the heating load and cool the warm source water in the evaporator as required by the heating load. They generally do not make chilled water, but extract heat from sources such as cooling tower water, ground water, solar heated water or industrial waste streams. Unlike a heat recovery chiller, they are controlled by the heating load and therefore only use the amount of energy required to meet the load. Templifier Water Heaters can be justified in new construction or retrofits, paying for themselves out of energy cost savings, compared to fossil fuel boilers or electric resistance heaters. 4
Typical Templifier Applications 5
McQuay Heat Recovery Chillers Heat Recovery Chiller Evaporator Connections How Heat Recovery Chillers Save Energy The centrifugal chiller with heat recovery uses a second bundle of tubes in the condenser to recover heat that would normally be lost in the cooling towers. The tower side tubes and the heat recovery side tubes are in parallel in a common shell side. The compressor s hot refrigerant gas passes over both sets. Tower Connections A heat recovery chiller is first and foremost a chiller, producing chilled water and controlled by the cooling load. The hot water temperature is controlled by artificially keeping the tower water temperature elevated through the use of the tower bypass valve. The useful heating output of these units can vary from zero (all heat to the tower) to all of the heat (cooling load plus the compressor power), converted to useful heat. Heat Recovery All of the heat rejection of the chiller is at the elevated heating water Connections temperature. These units are optimized economically when most of the total heat rejection is utilized for useful heating, most of the time. The electric cost of the heat is all the incremental compressor input power required to make the hot water; i.e., the power at the high water temperature, minus the power that would be required for a conventional chiller operating at a lower, optimized tower water temperature. Remember that all the compressor power is at the higher kw per ton. Benefits of Heat Recovery Chillers Potential for excellent return-on-investment. Heating COPs can be as high as 20. Relatively low first cost. The addition of a second set of condenser tubes, and the cost of pipe and fittings to connect up, are the only extra cost added to a standard chiller. Reduced fossil fuel use. A Btu of energy from natural gas or oil produces much more useful heat when used to generate 20 COP of electricity than when used in a boiler. Often the electric energy is nuclear or hydroelectric sourced, meaning no fossil fuel at all is used for heating. McQuay centrifugal chillers use R-134a refrigerant which is environmentally friendly with no phase-out schedule. 6
Heat Recovery Centrifugal Chiller System Operation The temperature of the heating water is controlled indirectly by controlling the tower water temperature. The temperature controller positions the tower bypass valve to establish the desired hot water temperature. Since both condenser bundles are in the same refrigerant gas stream, they will both leave the condenser at the same temperature. Analyzing the Economic Justification for Templifier Water Heaters and Heat Recovery Chillers Proper sizing and economic justification for heat recovery chillers and the Templifier product can be done by the McQuay Energy Analyzer Program. Just input the building parameters, choose the proper HVAC system type, and let the program do the system simulation. The following operating conditions improve the economic feasibility: As warm as possible source water for Templifier units or chilled water for heat recovery chillers. Output hot water temperature as low as possible. Constant availability of a cooling load for heat recovery chillers or heat source for Templifier units. Low electricity cost compared to higher priced fossil fuels. DesignTools ENERGY ANALYZER Applied Terminal Systems Unit Controllers Version 3.0 2002 McQuay International, www.mcquay.com 7
Technical Specifications Model THR Reciprocating Templifier Water Heater THR Model Number Heating Capacity (MBH) COP Sound Power (dba) Dimensions 040 571 5.9 78 117x34x63 045 659 6.0 79 117x34x63 050 780 5.7 80 117x34x63 060 880 5.9 80 117x34x64 070 1070 5.6 82 117x34x64 080 1162 5.6 82 117x34x64 085 1282 5.8 84 116x34x67 090 1375 5.9 85 116x34x67 095 1446 5.8 86 143X34x77 100 1537 5.8 86 143X34x77 110 1684 5.7 87 143X34x77 115 1709 5.8 87 143X34x77 120 1844 5.7 87 143X34x77 130 2004 5.6 88 143X34x77 145 2167 5.8 88 143X34x77 155 2277 5.7 88 143X34x77 165 2465 5.7 89 143X34x77 175 2682 5.7 90 143X34x77 185 2782 5.9 90 146X35x79 195 2971 5.8 92 146X35x79 210 3180 5.8 92 146X35x79 NOTE: Capacity is based on 75 leaving source temperature, and a 10-degree temperature drop in the evaporator. Leaving condenser water temperature is 120 F with a 10-degree temperature rise. Model TSC Centrifugal Templifier Water Heater TSC Model Number Heating Capacity (MBH) COP Sound Power (dba) Dimensions L x W x H 063 4632 5.2 85 169x63x80 079 6336 5.0 88 175x71x88 087 8040 5.6 95 175x101x100 100 13848 5.6 89 175x101x99 126 16380 5.3 94 181x119x106 NOTE: Capacity is based on 75 F leaving source temperature, and a 10-degree temperature drop in the evaporator. Leaving condenser water temperature is 130 F with a 10-degree temperature rise. Model HSC Centrifugal Templifier Heat Recovery Chillers HSC Model Number Cooling Capacity Range (Tons) Heating Capacity Range (MBH) Approx-Heating COP Dimensions L x W x H 063 150 250 2205-3675 20 175x57x94 079 275 400 4042-5880 20 175x 84x109 087 400 550 5880-8085 20 175x104x106 100 550 750 8085-11025 20 175x104x106 126 750-1200 11025-17640 20 175x126x118 NOTE: Capacity is based on 45 F leaving chilled water, and a 10-degree temperature drop in the evaporator. Leaving condenser water temperature is 105 F with a 10-degree temperature rise. COP based on 100% of chiller load being recovered. 2002 McQuay International (800) 432-1342 www.mcquay.com A/SP HR (01/03)