Genesse River Water Cooling System Information
Project OverviewThe project team is making detailed recommendations on utilizing the Genesee River to assist in both the cooling and heating needs on campus. Our primary scope is focusing on the Riverknoll apartment complex, which RIT has planned to rebuild within the next five years. Currently, the majority of Riverknoll apartments have no cooling system in place. Although a conventional air conditioning system could be designed when rebuilding the complex, there is great potential to look into alternative methods that will reduce environmental impacts and lower cost. By using a localized renewable resource (river water) such a system can provide cooling with significantly less utility-based energy, thus reducing energy cost and the harmful environmental impacts associated with producing the energy.
The project is currently developing a detailed design of the Riverknoll cooling/heating system. For the best overall performance, geothermal heat-pumps are being recommended as the mechanism for heating and cooling the apartments. These heat pumps are fairly small units that have a reversible design so that they can either reject heat from an apartment into a water source (to cool the apartment) or reject heat from the water source into an apartment (to heat). The team has performed calculations on the cooling and heating capacity needs of the different apartment types to select appropriate heat pump configurations for each. The water source that will be used as an input to the heat pumps is a closed-loop system that indirectly exchanges heat with the river. A filtered intake system will be used along the bank of the river to siphon river water to a heat exchanger that will transfer heat with the apartment complexs closed water loop in such a way that the two water loops never mix. This allows us to utilize the cooling capacity of the river water in the summer and the heating capacity of the river water in the fall and spring without having to deal with the silt and particles associated with the water. Although the river water will not provide sufficient heat in the winter, it is still effective at heating in the fall and spring. This is because the closed water loop will always be at a cooler temperature than the river water due to the constant extraction of heat from this closed loop by the heat pumps. In winter, the river loop would be shut off and a small boiler would be integrated with the closed loop to provide the heat needed.
This proposed system will cost more initially, but the yearly electricity costs will be significantly less compared with conventional air conditioning. Also, NYSERDA (New York State Energy Research and Development Authority) has several programs that can provide significant funding for applications using geothermal heat pumps. It is estimated that $400-$1000 of funding can be provided for each heat pump unit. With 275 units being recommended, this could account for a considerable amount of the initial cost.
Senior Design 1
MSDI Schedule/ProjectSDI Project Plan
Customer Needs and Design SpecificationsCustomer Needs and Engineering Specifications
Concepts ReviewConcept Review Reading Packet
Design ReviewDesign Review Reading Packet
Prelimiary Investigation Plan for Senior Design IIInvestingation Plan
Senior Design 2
MSD2 Schedule/ProjectSDII Project Plan
Detailed Design ReviewDetailed Design Review Reading Packet
Function and Performance ReviewFuncation and Performance Review Packet
Technical PaperTechnical Paper
Feasibility Analysis PaperConference Paper
MotivationRIT currently allocates a significant amount of resources in both providing and operating the various cooling networks across campus. These resources primarily include the equipment needed and the energy consumption associated with the equipment. The motivation for this project is the idea that a renewable water resource can be used in place of the costly equipment to provide cooling with much less energy requirements. When considering a centralized, renewable cooling system, there are several potential benefits to be recognized. Based on our project scope, these benefits fall into four broad categories.
- Electricity Savings: the combination of using available river water and reducing the number of chillers in use can provide a significant reduction in energy use.
- Improved cooling efficiency: a well-insulated system can transfer cool water efficiently across significant distances.
- Easy to maintain: a centralized cooling/pumping facility will be easier to maintain and staff than the existing network of chillers.
- Use of available renewable energy as opposed to purchasing energy: the system will reduce RITs reliance on utilities.
Project ObjectiveThe objective of this project is to develop a central system utilizing the Genesee River that would provide adequate heating and cooling needs to parts of the RIT campus. The project will also consider integrating other campus applications into this heating/cooling network based on further investigation of such applications. Successful completion of this project will include the following tasks:
- Determine the feasibility of the project
- Evaluate the current campus cooling system (HVAC)
- Compare alternative designs
- Determine costs and requirements for project
- Determine location(s) of system
- Consider additional applications (for example: sprinkler system)
Bench MarkingBefore doing a preliminary campus and system analysis, we looked more in depth at other existing heating and cooling applications which made use of natural water resources. Performing this analysis can help give us an insight as to what concepts work well in particular situations, and it can also help with providing an idea of what type of investigations to perform and considerations to account for.
Two primary applications that we looked into were the Lake Source Cooling (LSC) system at Cornell Campus and the geothermal heat pump system at the Cornhill Landing apartment complex here in Rochester (used for both heating and cooling).
Cornell LSCIn 2000, Cornell completed construction on a Lake Source Cooling system that used cool water from deep in Cayuga Lake to provide cooling for the entire campus.
The cool lake water (consistently around 39F) is brought into a facility on the shore through a 56 inch diameter HDPE pipe. A basic screen covers the intake to prevent fish and other organisms from getting into the system. This type of pipe was selected since it will not be substantially affected by the lake water (as opposed to a steel pipe, which would corrode over time). In the facility, a wet-well concept is used to allow for fluctuations in the water intake and naturally siphon water in from the lake. Here, the lake water is run through a parallel set of heat exchangers to transfer heat from a closed-loop of water running to/from the campus. There are seven plate heat exchangers for a capacity of 32,000 gpm (resulting in a peak cooling load of 16,000 tons), and at least two are kept running at all times.
The campus loop consists of over 14,000 feet of 42 inch diameter AP15L Gr X65 carbon steel piping that is half inch thick. This loop distributes the cooling across the campus, with several tie-in points to the previous chilled water and HVAC system (using air handlers). This system does not use any insulation, because the ground temperature generally does not have a strong impact on the chilled water loop, and generally only 3/10 F is gained over the distance to campus.
This system essentially replaced the eight chillers that Cornell had previously used for the campus, and the only current power requirements now relate to pumping the water. Because of this, 90% less electricity is used compared with the previous method, resulting in 0.08 kW/ton of cooling.
However, there are several relevant issues that must be mentioned. First, this project was a long-term investment, and the college paid over $60 million to construct this system, (which is planned to last near to 100 years). Also, significant environmental studies had to be conducted to ensure that there would not be an impact on the natural lake habitat, and 43 permits were required due to environmental concerns. Also, one of the current issues deals with the intake system near the bottom of the lake. The intake system faced upward about ten feet from the lake bottom, and there is still substantial sediment buildup. This is an important concern because, in RITs case, the Genesee River is not much deeper than 10 feet and often has sediment buildup.
Cornhill Landing Geothermal Heat PumpsCornhill Landing is a local apartment complex here in Rochester that uses the Genesee River to assist the heating and cooling processes. This is of particular interest because RIT would be using the same river resource, and because the Riverknoll apartment complex on campus currently does not have a consistent cooling system, and it is an application of interest that may be similar to Cornhill Landings case.
The complex uses heat pumps within each apartment unit to provide the heating and cooling. These heat pumps are connected to a closed loop system that runs through a flat plate heat exchanger to transfer heat to a loop of river water. This river water loop draws water in using a vacuum pump through a 6-ft deep box that is built into the bank of the river. This allowed the system to retrieve river water without actually being built out into the river. The heat pumps in each unit can be used for heating or cooling, so each pump can reverse the direction in which heat is being transferred. These heat pumps have proven to be very effective, and will generally provide 350% efficiency (meaning that they will output 3.5 times the energy in the form of heat transfer that was input as electricity). This system cost around $850,000 for the complex of 167 apartments, with a max of 1.5 tons (per hour) per unit.
|The diagram to the left is a representation of the river intake concept used at Cornhill Landing.|
Initial ConceptsBefore delving into the details of the current cooling network or formulating a new approach to cooling, it is beneficial to identify the basic requirements for the generalized function of providing cooling. For these reasons, the team identified key components of the cooling process and developed a series of potential solutions to each component. This process is documented in (Appendix). The most reasonable solutions in each case were used to develop a select set of alternative designs. Four leading designs were developed, which included the following:
- A closed one-loop system that indirectly dissipates heat into the river and provides a single supply and return to the campus cooling applications that are integrated with the system.
- An open-loop and closed-loop (two-loop) system similar to the first concept, where river water pumped in through the open loop exchanges heat with the closed loop.
- A closed one-loop system that indirectly dissipates heat into the river and provides a branched network of supply and return lines to different campus cooling applications.
- An open-loop and closed-loop (two-loop) system similar to the third concept.
A comparison of these concepts using some basic criteria indicated that the second concept was favored among the others. However, there was a strong dependence on the cooling application(s) considered, which made it important to first identify a set of applications to focus on before proceeding further with the concept selection.
Campus AnalysisThe academic portion of the RIT campus currently uses a few different types of cooling systems, but the primary type of system is a combination of chillers and cooling towers. Table 3.1 below displays details about the current campus chillers (for both electric and absorption chillers).
Current Campus ChillersThe diagram below shows the currents chillers on campus
The table indicates that the campus uses a combination of various chiller styles and technologies. This complexity adds to the maintenance/service requirements and makes it more difficult to manage the cooling loads across the campus. The goal of utilizing the river for cooling purposes is to reduce the chiller-specific cooling requirements. Although the cooling system cannot fully replace the current network of chillers on campus, it could provide significant cooling in place of a select group of chillers. This, however, would be limited to part of the year rather than the entire year due to the variations in river temperatures. Still, it would be possible for certain applications to use the cooling capabilities of the river water in place of using the chillers for a significant portion of the year.
Cooling Loads for West Side of Campus
Chiller Power Consumption per Cooling Ton
The electricity usage per chiller is based on all operating components that run off of electricity (including the power needed for the physical air-conditioning and for the fans). The table indicates that the average power usage is more than one kW per ton of cooling.
It is most likely that a river-source cooling system would not be able to provide for the year-round cooling needs of the applications that it will be integrated with. Therefore, it is unlikely that any chiller will be entirely replaced by a tie-in with the river-source cooling system. Instead, the river-source cooling system would be used to cool the chilled water loop returning to the chiller, which can significantly reduce the operating requirements of the chiller (allowing it to be shutoff completely when the river temperature is favorable).
For tying the proposed river-source cooling system in with the two applications mentioned, it would be most reasonable to provide a non-contact heat exchange system with the chilled water loop just before the water returns to the chiller. This could effectively take the place of the cooling tower and allow the chilled water loop to maintain the same amount of water and pressure.
Concept Comparison & SelectionRiverknoll concept
- Riverknoll Cooling System
The Riverknoll apartment complex currently lacks a central cooling system, and only some of the apartments have air-conditioning capabilities. Since the complex is situated fairly close to the river, this could be a prime starting point to assess the performance of a river-source cooling system. Integrating such a system could provide all of the apartments in the complex with a centralized and reliable source of cooling.
- CIMS Cooling System
In the CIMS building, the cooling system for the printing applications (and several other applications) consists of two primary chillers that cool a chilled water loop and use an evaporative cooling tower to assist in lowering the return water temperature. One chiller is a centrifugal chiller, while the other is a screw machine. These chillers operate in the buildings main mechanical room (1255), and the chilled water loop that they cool is piped to the various bays (3, 5, and 6) where the printing presses and printing application labs are located. The chilled water specifically is used by the printing process (as mentioned before), while the rest of the working environment is cooled by running the chilled water loop through air handlers (on the second floor of the large bays) that tie in to an HVAC system for distributing cooled air.
CIMS has the advantage of being fairly close to both the Genesee River and the Riverknoll complex, so integrating it as one of the cooling applications would not require a substantial amount of additional piping.
- Microelectronics Laboratories
Building 17 has a variety of cooling (and heating) systems. The controlled environment Microelectronic laboratories use a chilled water loop cooled by one of two existing chillers located on the first floor of the building. These are two different types of centrifugal chillers, and a cooling tower is used in conjunction with whichever chiller is operating. This chilled water is used as processing water, but cooling is also provided for the HVAC system used within the laboratories. This chilled water loop needs to be maintained year round, meaning that there is always one of the two chillers operating during the entire year. The other portion of building 17 (including classrooms and offices) uses a heat pump system that will distribute the heat from portions of the building with excess heat to portions with insufficient heat. When the building overall has excess heat, the heat pumps work with another cooling tower to reject heat from the system.
Depth and Temperature statistics
A vital part of assessing the scale of a river-based cooling system is having a thorough understanding of the rivers variables and the trends within such variables. The primary variables we are interested in include temperature, depth, and flow rate.
Unlike the deep waters of a lake, the temperature of a river can very greatly over the course of the year. In the case of the Genesee River, the water temperature can generally span anywhere between 32F to 80F. The Genesee will most likely not freeze solid (other than just the surface), and will not drop below 32F at the depth that we are interested in.
The depth of the river also varies over the course of the year. This can be seen in the plot above of the Genesee River depth, taken at Ballantyne Bridge (Jefferson Road) throughout last year.
Variation at Ballantyne Bridge
With regard to flow, USGS reports that the river discharge near Balantyne Bridge typically ranges from 5,000 to 8,000 ft cubed/second. However, further analysis will need to be conducted to determine the cross-sectional area of the river at the point of interest and assess what impacts returning water will have on the river.
Risks and Regulations
There are several inherent risks associated with using river water in an application that will heat the water being withdrawn. The variability is a major risk, but there are also state regulations that must be identified.
Two major issues with using the river water include limitations as to how much water can be withdrawn from the river and how much the river temperature can be increased. State regulations allow up to 1,000,000 gallons per day to be withdrawn from the river per application. This correlates to about 690 gallons per minute. This puts a fairly fierce upper limit on the scale of applications that this river-source cooling loop can be used for. With regard to temperature, NYCRR thermal discharge regulations require that the water temperature at the surface of a stream or river does not exceed 90F. These regulations also state that 50% of the cross-sectional area of the river cannot be increased in temperature by more than 5F from the previous temperature.
Further regulations may also need to be addressed depending on the final selection of the intake system location. Handling such issues is out of the scope of the project, and it is most likely that the issues would require negotiations between the institute and the appropriate authorities in order to determine what measures will be necessary to ensure that there is not a significant environmental impact on the surrounding river habitat. Some of the key authorities include the Department of Environmental Conservation and the Canal Authority (due to the connection with the Erie Canal).
There are also some issues with how to physically take in the water from the river if the designed concept is to pipe the river water to a remote location. One of the major concerns is the filtration of water that would most likely be needed. Individuals working with other applications using the Genesee River (such as the Cornhill Landing heat-pump project near downtown Rochester and the University of Rochester Cogeneration facility) have indicated that the river will become fairly mucky and full of sediment during the summer months, especially along the bed of the river. Therefore it is recommended that the water being utilized is filtered or strained to an extent at which debris in the water will not have an impact on the functionality of the system. Also, the intake point within the river will need to have a screen of some sort to initially prevent bulky sediments from being brought into the piping. Furthermore, many flat plate heat exchangers have grooves within the plates to assist in heat transfer, but these grooves can often allow for sediment to buildup fairly easy if it is within the piping loop.
These concerns show potential advantages for using a box-like design as was used in the Cornhill Landing project. The screen/filtration system itself could exist between the river and the box, ensuring that the water being taken into the piping has a specific maximum particle size.
Some major issues with construction also need to be addressed. For example, in building a connection with the river, the system would need to include piping underneath East River road, which is not owned by RIT. Also, some negotiations are necessary to provide land to work with in developing the intake system (since RIT also does not own land along the bank of the river). Furthermore traffic plans would need to be developed when doing any construction on/below East River Road. With regard to piping the water to campus, the piping route will need to avoid wetland space whenever possible. Wetlands are an important aspect of the surrounding ecosystem, and destruction of such wetlands requires measures that are nearly equivalent to re-establishing the same area of wetland in a new location.
OverviewThe Riverknoll apartment complex cooling application was determined to be the best alternative in performing a river-source cooling system analysis due to the following characteristics:
- RIT is planning on renovating/rebuilding the complex
- No current cooling system is in place (and one is needed)
- The complex has a favorable location
- Less restrictions are imposed on the layout (will not rely on existing equipment)
- The river can provide a significant portion (if not all) of the cooling load
Riverknoll Housing ConceptsThe Riverknoll apartment complex is located on the west side of campus just minutes from the academic buildings and the Genesee River. The current housing option and number of available units are listed below:
There are currently 275 apartment units and 1 office unit located on the Riverknoll parameter. All units have heating available, but only the 1 bedroom apartment units provide both heating and cooling.
Riverknoll Gas ConsumptionTo understand the demand of heating and cooling for the Riverknoll apartments, it is important to identify the annual gas and electricity consumptions:
Riverknoll Electricity Consumption
Riverknoll Heating and Cooling SystemsThe current heating and/or cooling applications for Riverknoll are:
For the past few years, RIT Facilities Management has expressed interest in replacing the entire Riverknoll apartment complex with new apartment buildings. Currently, there is no specific plan for when the replacement will take place. If the replacement plan becomes a reality, there will be great opportunities for the new heating and cooling systems.
The recommended application to provide cooling (and heating) in this situation is through a geothermal heat pump that utilizes the river. A heat pump would be installed at each apartment unit at Riverknoll and it would provide the majority of heating and cooling needs (but would require assistance from a boiler during winter operation). The river water will be used for cooling/heating in a once-through non-contact cooling system.
The basic system setup includes a closed loop and an open loop. The closed loop will be accessible to all of the geo-thermal heat-pumps used by the apartments, allowing them to reject heat into the loop to cool the apartment space. Thus, this loop will tend to remain at a fairly high temperature (initially estimated to be between 85F and 90F). The open loop will intake water from the Genesee River through a type of box established below the bank of the river. This box will provide initial coarse filtration of the river water, and allow for an intake system to be setup without protruding into the actual river. As the river temperature will generally range between 60F and 80F during the summer months, the river loop will always be cooler than the closed apartment loop. Therefore, a heat exchanger between the two loops will allow heat to be transferred from the closed loop to the river loop, maintaining the temperature of the closed loop.
This system will be operational through a significant portion of the year. Furthermore, this layout would be acceptable in providing heating during the fall and spring months. However, the river water alone will not consistently provide the heat needed during the winter months. During the winter, the heat pumps will be extracting heat from the closed apartment loop. Thus, it will remain at a low temperature (which we initially estimate at 30F and 35F). The river loop will only be able to keep this loop at equilibrium if the river water temperature exceeds 40F (to prevent freezing). Based on historical data and by benchmarking other local applications of geothermal heat pumps, it is estimated that such a system would be operational from April through November, with boilers needed to add heat to the closed loop during the winter months.
Limitations and ConstraintsDeveloping the details of this proposed system requires that the underlying limitations and constraints are identified. Some of the major constraints in this situation relate to the land and river use, both of which were discussed in depth in the previous section. With respect to this specific application, though, the following limitations are most prominent:
- Narrow land availability along river edge. This makes it difficult in both designing and constructing an intake system.
- Wetlands located along the east side of East River Road. These need to be avoided if possible.
- Variability in river temperature. Ranges from near freezing to around 80F
- The amount of river water that can be displaced is limited to 1,000,000 gallons per day
- The river temperature cannot rise by more than 90F at the surface.
- Using river water directly will require a level of filtration and routine cleaning
When the water is near its freezing point, it is difficult for the river loop to effectively provide heat to the apartment loop. Due to this issue, the loop could be combined with the CIMS chilled water loop to channel the heat rejected by that loop to the apartment loop. CIMS has the advantage of being fairly close to both the Genesee River and the Riverknoll complex, so integrating it as one of the cooling applications would not require a substantial amount of additional piping.
Heat Pump InformationAlthough heat pumps have been around for a while, geothermal applications using heat pumps have been fairly limited. Traditional heat pumps have the main advantage of being able to transfer heat in both directions, meaning that they can provide heating or cooling depending on the direction of flow of the working fluid. Also, they have the advantage of being able to move heat using less energy than typical air-conditioning configurations and across a wider range of temperatures. Geothermal heat pumps have the additional advantage of being able to either reject or provide the heat that is being moved using a closed loop system with only simple pumping to keep the system at equilibrium. No additional energy is needed (other than the pumping) to reject heat.
The internal workings of a heat pump are similar to that of an air conditioning unit, but with the ability to reverse the flow direction by means of a valve (known as a baseball valve). Figure below shows the basic functionality of a heat pump.
Although the working fluid always flows the same way through the compressor, the valve allows for the flow through the coil and heat exchanger to be reversed. Thus, the system can either take heat from or reject heat to the water supplied through the heat exchanger.
Apartment Heating and Cooling LoadsInitial calculations have been made to determine the heating and cooling requirements for the current Riverknoll apartment layouts. Since there is no indication of what changes would be implemented in rebuilding the apartments, the proposed heat-pump system will be based on the current needs of the complex. Also, the calculations are based on an average of 300 sq. feet of living space per person by considering the occupancy rate of the three types of apartments (1-bedroom, 2-bedroom, and 3-bedroom).
Three main considerations in determining the heating and cooling needs of the apartment layouts are the construction materials, the solar exposure, and the radiant heat given off by the occupants. Here, the ASHRAE handbook was used to assist in calculating these effects. The table below shows the approximate material, thickness, R-values, and U-values used in calculating the conduction loss and heat gain.
With respect to the solar exposure, many of the apartments are oriented with different exposure to the sun. Also, some have 2 exposed walls, while some have 3 exposed walls. For obtaining calculations representative of all apartment orientations, the worst case scenario was used for each apartment type. Also, the radiant heat given off per person was considered using a sensible load of 215 btu/hour per person and a latent load of 185 btu/hour per person.
Taking all of the factors into consideration, the resulting heating and cooling loads per apartment type are displayed in Table below.
Heat Pump and Temp. SelectionBased on the calculated apartment loads, specific heat pump models were selected that best suited the needs for the load. McQuays geothermal horizontal heat pumps were the preferred heat pump style due to the wide selection and the availability of detailed specifications. The units (models) selected and the details of each are displayed in Table below. The entering water temperature (EWT) was determined to be 85F to ensure that the loop remains warmer than the river water. Also, the energy efficiency rating (EER) is calculated as follows:
EER = Total Cooling Load (btu/hr) / Energy Use (Watts/hr)
Therefore, power draw can be determined when provided with the cooling load and EER.
Piping and Pumping SelectionThe piping layout is based on the current Riverknoll apartment complex layout. Using the GPM values provided per selected heat pump, the total GPM required for the closed loop is calculated as shown in Table below.
Flow Rate Calculations
Building Configurations and GroupsThere are 35 buildings in the complex, each containing several of the same type of apartment (1, 2, or 3 bedroom). Building Configurations table displays the GPM calculations per building based on the apartment types in that building.
To provide the most efficient piping system, the proposed piping layout will consist of a primary (central) loop with six separate branches to groups of buildings. The configuration of these building groups is shown in Buildings Groups Table.
Closed Loop Piping NeedsThe piping will lead back to a mechanical room to provide the heat transfer with the river loop. The table below shows the calculated pipe lengths for the various sizes of piping used in the layout.
Based on the length, diameter, and route of the piping, the total head loss for the closed loop was determined to assist in selecting an appropriate pump and determine the energy requirements for operating that pump. The head loss calculations for both the supply and return portions of the loop can be find in the Conference Paper. In order to maintain the flow at the desired level of 1100 GPM, it was determined that a 150 horsepower pump would be needed within the loop. For backup purposes, it was also recommended that two pumps be installed in the loop (in parallel) with only one pump operational at any given time.
Heat Exchanger Calculations and selectionA heat exchanger is necessary to move heat from the closed (apartment) loop to the river loop, and vise versa, without physical contact between the two loops. To provide the most efficient heat transfer at the needed flow-rates, a flat-plate heat exchanger is recommended. Figure belwo shows a schematic of the heat exchange process between the two loops.
Ideally, it is desired to keep the entering water temperature to the heat pumps at around 85F to keep a consistent capacity. However, in conditions where the river water is near 80F and the apartment heat pumps are all running near full capacity, maintaining such a level is nearly impossible. In such a case, the supply portion of the closed loop would only be reduced to about 90F. However, the heat pump units selected were provided with enough of a buffer between the required and the maximum cooling load that they will still provide sufficient cooling up until about 95F EWT. The energy efficiency, though, is reduced at these levels. Still, it is very unlikely that all of the complex apartments would be operating at full capacity at the same time. This is especially true since there is typically only 35% occupancy of the apartments during the summer months.
Based on the flow and temperature requirements determined, a specific heat exchanger model was selected with assistance from outside sources. The heat exchanger model specifications can be find in the Conference Paper. Additionally, model is a Graham plate heat exchanger with a plate thickness of 4 mm.
Facility NeedsA specific facility (or mechanical room) would be necessary to contain the heat exchanger, pumps, boiler, and any other equipment deemed necessary for the system. An assessment of two possible locations for a pumping/cooling station was performed to determine the feasibility of each, benefits of each, and limitations of each. The goal of this analysis was to identify the most desirable and reasonable location of the group.
- Along hillside near Red Barn
- Near the river front
Figure below displays the general regions that these potential locations are referring to. It also displays the areas considered to be wetlands, which will strongly influence the locations of and the routing to and from a pumping facility.
The tables below summarize a comparison between these locations based on critical criteria. The criteria includes: cost (including the piping and construction considerations), efficiency, facility operation, environmental impact, and disruption (to other school-related functions). The first two tables below display a rating and reasoning for each particular location, while third table is a direct comparison between all locations.
The ratings displayed in the last table above demonstrate that the most favorable location for the facility is the hillside near the red barn. This location has the advantage of being both within a reasonable distance of the river and within a reasonable distance of the primary applications. Also, there is a sufficient amount of un-used land in this location without intruding upon wetland territory. When discussing this location with the facilities management personnel, it was further concluded that it is a reasonable location given the applications that will be considered and because there is no planned expansion projects that will be using this portion of the campus.
Intake SystemThere are several intake systems that are proposed for this design. There are several factors that will affect the decision for the layout. Since construction and infrastructure costs will remain similar, the main factors will be land negotiations, environmental impacts, and aesthetics. The two designs that show the most promise can be seen in the figures below. Layout one contains a water-well located towards the heat exchangers. A vertical turbine pump is used to pump water through the piping to the well. This concept allows for a more aesthetically pleasing area since the river back is minimally disturbed. In addition, it is assumed that it would be easier to build on privately owned land. The second concept involves the water well being placed closer to the river where a river water inlet will be constructed at a six foot depth using a 20-inch pipe connection. Water is then pumped using a vertical turbine pump, which is place at the top of the well, through pipes to the heat exchangers. The main advantage here is to limit the size of the open loop system and thus minimize the contact to the natural environment. These two concepts both have advantages and disadvantages for each.
Intake System ComparisonThe two proposed designs are shown below:
A matrix was created to assist in the selection process. The table below illustrates this.
The table indicates that Layout 1 has the highest ranking of the two. Therefore, a more detailed schematic of the intake system was developed using Layout 1 as a guideline. This more detailed layout can be fine in the Conference Paper. The layout includes a box or wet well that water would flow freely into through a 20-inch pipe between the box and the river (although a screen will be in place to block debris and fish). Water will then be pumped to the heat exchanger from this box.
Energy ConsumptionDetermining the energy consumption associated with the recommended system can provide an understanding of both the operating costs of the system and the environmental impacts from running the system. For purposes of comparison, it is also necessary to determine the energy consumption of a conventional cooling system (such as an air-cooled chiller system or a water-cooled chiller system).
Proposed SystemThe first table below displays the energy consumption calculations for the three heat pumps used, while second table below provides energy consumption calculations for pumps used in the closed loop and river loop. The energy consumption of a heat pump is correlated with the percent of the full capacity load that the heat pump is providing. Typical heat pumps will provide the most efficient energy use (kWh/ton) when operating at 50% of the full capacity. The calculations in both table account for this by indicating the predicted number of occurring hours for each percentage of the full cooling load.
Energy Consumption of Heat Pumps
Energy Consumption of Water Pumps
Cooling System AlternativesA conventional system could use either an air cooled chiller to reject the heat from the closed loop or a water cooled chiller and cooling tower combination to reject the heat from the closed loop. Both setups will be assessed and compared with the river-source heat pump system. Figure below displays a schematic of a water-cooled chiller and cooling tower configuration.
Chiller and Tower Cooling System
Both the air cooled and water cooled chiller configurations will run at a lower closed loop temperature of around 55F to increase the cooling efficiency provided by the heat pump (the EER). Although this reduces the energy use by the heat pumps, the energy needed to operate the chiller will still be a burden in each case. First table displays the energy use associated with an air cooled chiller, and the second table below displays the energy use associated with a water-cooled chiller. In the water-cooled chiller system, the cost of the lost water relates to about 2% of the loop water evaporating in the cooling tower (and needing replacement constant replacement).
Air Cooled Chiller Energy Consumption
Water Cooled Chiller Energy Consumption
Construction and Installation CostsA first step in determining the capital costs for the cooling system is to calculate the piping costs. Black carbon steel piping was used in the closed loop, since the loop needs to function for both heating (with a supplemental boiler) and cooling. The piping costs for each diameter are shown in table below.
Fixed (Capital) CostsThe total piping cost and the other equipment costs (capital costs) associated with the cooling system are displayed in figure below. The trench cost for the piping assumes that supply and return piping would be contained within the same length of trench. Some equipment, such as a boiler and the apartment ductwork, is not included. This is because the costs are not specific to the river-based cooling system (they would be about the same in a conventional cooling system).
Operating CostsOne of the primary benefits of most geothermal heat pump systems relates to the reduced operating cost, which is based mostly on the reduced energy consumption. Table below indicates the total cost associated with both the heat pump and water loop pump energy use.
NYSERDA funding opportunitiesThere are several funding options when utilizing energy efficient geothermal heat pumps in New York State. NYSERDA (the New York State Energy Research and Development Authority) has two different program opportunities for obtaining funding. The Environmental Power Systems Technologies program offers up to $250,000 per project, with two periods for submitting proposals (fall and spring). The Industrial Research, Development and Demonstration program will provide for 50% of the project cost up to $400,000, with three periods for submitting proposals (in March, July, and November). However, the requirements and periods for submitting a proposal, in both cases, will most likely be different by the time the system is being implemented.
Cost ComparisonsThe heatpump system is expected to last 20 years without replacement. Therefore, a life cycle of 20 years will be used to appropriately weigh the capital costs with the annual operating costs (as well as the funding opportunities). This life cycle cost is shown in table below assuming a 5% effective interest rate to account for inflation and the time-value of money.
20 Year Life Cycle for River-Cooled Heat Pump
To truly determine how favorable this system cost is, it is necessary to compare both the capital and operating costs with those of a conventional heat pump cooling system. The first table belwo displays operating costs for an air cooled chiller system, and second table below displays operating costs for a water cooled chiller system. In the water cooled chiller system, the cost of the lost water relates to about 2% of the loop water evaporating in the cooling tower (and needing replacement constant replacement).
Air Cooled Chiller System Operation Cost
Water Cooled Chiller System Operating Cost
The capital costs of these two systems are be less than the cost of the river based water system (since the river loop, intake system, and vacuum pumps are not needed). However, the chiller cost still contributes significantly to the total equipment cost. Also, since the operating costs are higher in the chiller systems than in the river-cooled system, it is important to look again at a 20-year life cycle for each system. The first table below displays the life cycle for an air cooled chiller system and second table below displays the life cycle for a water cooled chiller system. Again, an effective rate of return of 5% is used to account for both interest and inflation rates.
20 Year Life Cycle for Air Cooled Chiller System
20 Year Life Cycle for Water Cooled Chiller System
This analysis shows that the 20-year cost for a river-cooled heat pump system is over $100,000 less than that of a conventional system. The funding can play a major role in the difference between capital costs, so it is important to compare scenarios involving no funding and significant funding to see how much of an impact it will have. The first figure below compares the capital cost for the three systems (both with and without NYSERDA funding for the river-cooled heat pumps). Also, second figure below displays a comparison of the operating costs for the three systems.
Life Cycle Comparisons - Capital Costs
Life Cycle Comparisons - Operating Costs
Net Present Value ComparisonsComparing different values for the effective rate of return can also indicate how sensitive the net present value of each system is to the rate of return. Table below shows a breakdown of the net present value for each system based on different effective rates of return, and it also indicates the payback period for the river-cooled system in each case.
The data indicates that providing the absence of NYSERDA funding would have a major impact on the payback period of the project, especially as the rate of return increases.
Enviromental ImpactsThe three primary categories of environmental impacts for this proposed project relate to the effects on river temperature, the impacts of refrigerant usage, and the requirements for electricity production.
Effects of Energy ConsumptionOne of the major impact issues with this project deals with the CO2 production associated with the energy consumption. In Rochester, it is estimated that 1.44 lbs of CO2 is produced in delivering 1 kWh of electricity. Based on this relationship, Figure below displays the CO2 production comparing the three systems discussed in the section above.
CO2 Production Based On Energy Consumption
Based on this figure, the river-cooled system has the best performance in minimizing the CO2 production associated with providing cooling.
River Temperature ImpactsWith respect to river temperature, there are state regulations that require a river not exceed 90 F at any point at the surface. In the proposed system, the heat exchanger is setup such that the max temperature flowing out of the river loop side is 90 F. Since water in this loop is first released into a box along the shore, the water will enter the river at several feet below the surface. Since the river temperature naturally reaches a maximum of 82 F, the addition of 90 F water at the box depth will disseminate within the river and result in minimal change to the surface temperature. It is important, though to provide the necessary screens between the boxes and the river to prevent aquatic life from entering the supply and return boxes, which will still remain near to 90 F.
Heat Pump Refrigerant AssessmentIn choosing a refrigerant for the heat pump applications, R-22 is commonly used within heat pumps in industry. However, R-410A is another option that will also work effectively with heat pumps. The table below shows a comparison between the two types.
ODP represents the ozone depletion potential, and it is an indicator of the ability of a refrigerant to destroy stratospheric ozone molecules (using CFC-11 as a base of 1.0). GWP is the global warming potential, and it indicates the ability of a refrigerant to trap radiant energy (relative to C02 over 100 years). R-410A has no ODP, nor a phase-out date based on the Montreal Protocol. However, it has a higher GWP. The GWP, though, only accounts for direct effects on global warming. According to TEWI (the Total Equivalent Warming Impact), direct effects are only responsible for an average of 7.5% of the total global warming impact. The TEWI index accounts for both direct and indirect (such as electricity use) effects. In 1999, R-410A had the best performance of the eight refrigerants examined according to the TEWI index. Furthermore, the EPA has formally recognized R-410A as an acceptable substitute for R-22.
Recommendations and ConcernsComparing the river-cooled system with conventional cooling systems indicate that the river-cooled system will reduce the operating (annual) system costs, but will also increase the capital cost. However, depending on the funding available for geothermal heat pump applications through NYSERDA, the capital costs could be significantly offset. Our estimates indicate that over $200,000 in funding could be provided, lowering the capital cost near to that of a conventional cooling system. Since the operating costs are lower, the river-cooling system would clearly be the best option in this case. When compared with the air-cooled chiller system, the river-cooled system will have a payback period of about 3-4 years. When compared with the water-cooled chiller system, the river-cooled system will pay off immediately. Without the funding opportunity, though, the river-cooled system would have a much longer payback time, as is apparent in Table 8.9. In this case, the river-cooled system would not be an economically viable alternative when compared with the water-cooled chiller system.
Leading concerns that still need to be addressedSome of the leading issues that hold the project back from further development relate to the location of the intake system and the negotiations needed to approve the use of such an intake system. With this information, more specific river data at the point of interest can be collected and analyzed. This would allow for a detailed intake system drawing to be developed, and it would provide significant information that would help in assessing the environmental impacts of displacing and warming the river water.
Actions recommended to further develop projectFuture work along the scope of this project should focus on obtaining a detailed estimate for the NYSERDA funding opportunities available. This funding can sway the project significantly from being favorable to being unfavorable (economically), so it is important that a reliable baseline value can be determined.
With respect to the system functionality, more detailed statistics comparing the air temperature with the river water temperature at different points throughout the year could allow for a relationship to be developed between the two. This relationship can be used in developed a detailed assessment of the cooling loads and the heat exchange process throughout the cooling season.