SCENARIOS
"Business as Usual" Model
The total electricity consumption of the SLO Swim Center is 83,349 kWh/year. Using this value and the assumption that the pool pump consumes 70% of total electricity, the pool pumps currently consume approximately 58,344 kWh/year. This leaves 25,004 kWh consumed by the Sinsheimer facility itself.
Assumptions (values provided by the City of San Luis Obispo):
Total Electricity used by the SLO Swim Center (produced by the Cogen System) : 83,349 kWh
Total Natural Gas Consumed By Facility: 3,403,091 kWh
Cogen Electrical Conversion Efficiency: 25%
Cogen Waste Heat Availability: 45%
Boiler Efficiency: 88%
70% of Total Electricity Consumed is used to run the pumps -
83,349 kWh * .7 = 58344.3 kWh for the pumps
83,349 kWh * .3 = 25,004.7 kWh for the building
Cogen Heat Output - 83,349 kWh * .25 *.45 = 150,028 kWh
Total Natural Gas Consumed by the Boilers (w/out VFP)-
3,403,091 kWh - (83,349 kWh / .25 ) = 3,069,695 kWh
Heat Necessary for Pool Heating-
2,701,331 kWh + 150,028 kWh = 2,851,360 kWh
Total Heat Output to the Pool (w/out VFP)-
3,069,695 kWh * .88 = 2,701,331 kWh
Scenario #1 : Variable Flow Pump only
Installation of a variable flow pump is the simplest improvement from a system analysis standpoint. It represents an efficiency improvement akin to replacing incandescent lights with LED. For the purposes of this analysis, the facility electricity will continue to come from cogeneration, while any extra heating load from lower cogeneration power is shifted to the boilers.
Installation of a variable flow pump is the simplest improvement from a system analysis standpoint. It represents an efficiency improvement akin to replacing incandescent lights with LED. For the purposes of this analysis, the facility electricity will continue to come from cogeneration, while any extra heating load from lower cogeneration power is shifted to the boilers.
Installation of a variable flow pump is the simplest improvement from a system analysis standpoint. It represents an efficiency improvement akin to replacing incandescent lights with LED. For the purposes of this analysis, the facility electricity will continue to come from cogeneration, while any extra heating load from lower cogeneration power is shifted to the boilers.
Installation of a variable flow pump is the simplest improvement from a system analysis standpoint. It represents an efficiency improvement akin to replacing incandescent lights with LED. For the purposes of this analysis, the facility electricity will continue to come from cogeneration, while any extra heating load from lower cogeneration power is shifted to the boilers.
With the electricity consumption of the pool pumps reduced by 60%, the calculated electricity consumption for the pumps is 23,337 kWh/year and 48,342 kWh/year overall for the facility. This reduction in electrical consumption negatively impacts the Cogen system's output heat resulting in an increased heat output reliance on the boiler system. Contrary to the expectation of the authors, the installation of the variable flow pump is predicted to increase both natural gas consumption and carbon emissions of the SLO Swim Center.
Scenario 1 Calculations:
VFP reduces energy consumption by 60% -
58,344.3 kWh * .4 = 23,337.72 kWh ← new energy consumed by the VFP
New total electricity generated by the Cogen -
23,337.72 kWh + 25,004.7 kWh = 48,342 kWh
If energy consumption is reduced, then waste heat generated is also reduced-
48,342 kWh * .25 *.45 = 87,016 kWh
Total Natural Gas Consumed by the Boilers (w/ VFP)-
3,069,695 kWh + (150,028 kWh - 87,016 kWh) = 3,132,707 kWh
Total Heat Output to the Pool (w/ VFP)-
3,132,707 kWh * .88 = 2,756,782 kWh
Scenario #2 : Variable Flow Pump and Heat Pump on Grid Electricity
A heat pump is meant to completely replace the heating load of the boilers by drawing electricity to push heat against a temperature gradient (ambient air and pool water). The electrical power can derive from the cogeneration system or the grid; the exact proportions may depend upon electricity and fuel prices, as well as decarbonization goals. It is assumed that in the long term, the proportion of renewable energy in grid electricity will approach 100%, such that full decarbonization is best achieved by running a heat pump on grid electricity.
A heat pump is meant to completely replace the heating load of the boilers by drawing electricity to push heat against a temperature gradient (ambient air and pool water). The electrical power can derive from the cogeneration system or the grid; the exact proportions may depend upon electricity and fuel prices, as well as decarbonization goals. It is assumed that in the long term, the proportion of renewable energy in grid electricity will approach 100%, such that full decarbonization is best achieved by running a heat pump on grid electricity.
This scenario looks at the installation of both the VFP (from scenario 1) and heat pumps that will run on entirely grid electrical energy. The VFP and cogeneration system runs the same as scenario 1. Implementing a heat pump with a COP of 4 adds an additional 681,086 kWh load from the grid allowing this heating system to reduce carbon emissions to 35 tons.
This scenario looks at the installation of both the VFP (from scenario 1) and heat pumps that will run on entirely grid electrical energy. The VFP and cogeneration system runs the same as scenario 1. Implementing a heat pump with a COP of 4 adds an additional 681,086 kWh load from the grid allowing this heating system to reduce carbon emissions to 35 tons.
Scenario 2 Calculations:
Heat Pump Output -
2,701,331 kWh + 87,016 kWh = 2,764,343 kWh
Heat Pump Electricity Input w/ COP of 4-
2,764,343 kWh / 4 = 691,086 kWh
Scenario #3 : Variable Flow Pump and Heat Pump on Cogen Electricity
Drawing an increased load from cogeneration electricity for heat pump operation entails increasing the heating capacity of the cogeneration waste heat. This means that the heating capacity of the boilers is displaced by the work of both the cogeneration system and the heat pump. A pattern of covariance is thus observed, with an approximate ratio of marginal cogeneration heating capacity per marginal heat pump capacity of 2:1. In this way, every 1 kWh of heat provided by the heat pump carries an additional 2 kWh of heat generated by cogeneration of the electricity needed to drive the heat pump.
Drawing an increased load from cogeneration electricity for heat pump operation entails increasing the heating capacity of the cogeneration waste heat. This means that the heating capacity of the boilers is displaced by the work of both the cogeneration system and the heat pump. A pattern of covariance is thus observed, with an approximate ratio of marginal cogeneration heating capacity per marginal heat pump capacity of 2:1. In this way, every 1 kWh of heat provided by the heat pump carries an additional 2 kWh of heat generated by cogeneration of the electricity needed to drive the heat pump.
This scenario relies on entirely cogeneration electrical production resulting in an increased usage of natural gas into the cogeneration system. The heat output of the cogeneration system dramatically increases allowing the heat pumps to produce less heat for the pool. Despite this scenario being more cost efficient due to less electricity from the grid, it still emits a larger amount of carbon over scenario 2, but half as much carbon compared to scenario 1 and the "business as usual" system.
Scenario 3 Calculations:
Heat Pump Output -
2,764,343 kWh * (4 / 5.8) = 1,906,444 kWh
Heat Pump Electricity Input w/ COP of 4-
1,906,444 kWh / 4 = 476,611 kWh
Cogen Electricity Produced w/ Heat Pump -
476,611 kWh + 48,342 kWh = 524,953 kWh
Cogen Heat Output w/ Heat Pump -
524,953 kWh * .25 * .45 = 944,916 kWh