and ext Inlet Temp) 0.165 GPM (avg between Int and ext Inlet Temp)
0.66 GPM (avg between Int and ext Inlet Temp) 0.165 GPM (avg between Int and ext Inlet Temp)
0 01 02 03 04 05 06 07 08 09 10 11 12 -1000 -0800 -0600 -0400 -0200 0 0200 0400 0600 0800 1000 -1100
FIG. 6.25 MVP Prototype I comparison of normalized annual energy using 2.50 l/min (0.66 gpm) vs 0.625 l/min (0.165 gpm) using the system inlet temperature of an average between indoor and outdoor temperatures.
CUMULA
TIVE ENERG
Y (kW
h/m
2)
NORMALIZED ANNUAL ENERGY vs TIME (0.66 GPM and 0.165 GPM, Photovoltaic and Solar Thermal)TIME (mo)
Solar Thermal (770.3 kWh/m2/yr) Photovoltaic (200.8 kWh/m2/yr) 0 01 02 03 04 05 06 07 08 09 10 11 12 -1000 -0800 -0600 -0400 -0200 0 0200 0400 0600 0800 1000 -1100
FIG. 6.26 MVP Prototype I comparison of normalized annual energy using 2.50 l/min (0.66 gpm) vs 0.625 l/ min (0.165 gpm) compared to Photovoltaic and Solar Thermal outputs.
While cumulative power is one measure of system efficacy, the access to available power is a better real world measure of how much the TACE system can impact EUI. As shown in Figures 6.27 and 6.28, Heat and Coolth were simulated for a year using: 1) daily varying groundwater temperature over the year as inlet temperature; 2) consistent 22° C (71.6° F) inlet temperature. These cases represent both a varying and static inlet temperature, and while they do not reflect real world performance, they illustrate the impact of the inlet temperature and its importance. Ultimately, to characterize the real work performance, the inlet temperature was simulated as a function of the outlet temperature after the working fluid has transferred energy with the thermal battery through the countercurrent heat exchanger and was captured in the results of the Bay and Floor and Building energy simulations.
5 10 15 20 25 30 35 40 45 22 TEMPER ATURE (°C)
OUTLET FLUID TEMPERATURE vs TIME (0.66 GPM, Ground Temperature vs 22°C) 0
Hot Outlet Flux
Daily Average Ground Temperature Cold Outlet Flux
TIME (mo)
0 01 02 03 04 05 06 07 08 09 10 11 12
FIG. 6.27 MVP Prototype I comparison of temperature flux at 2.50 l/min (0.66 gpm) flowrate using ground temperature and 22°C (71.6° F) as inlet temperatures.
5 10 15 20 25 30 35 40 45 22 TEMPER ATURE (°C)
OUTLET FLUID TEMPERATURE vs TIME (0.165 GPM, Ground Temperature vs 22°C) 0
TIME (mo)
0 01 02 03 04 05 06 07 08 09 10 11 12
Hot Outlet Flux
Daily Average Ground Temperature Cold Outlet Flux
FIG. 6.28 MVP Prototype I comparison of temperature flux at 0.625 l/min (0.165 gpm flowrate using ground temperature and 22°C (71.6° F) as inlet temperatures.
The results of the inlet temperature simulations indicated:
–
That using average groundwater temperature yields the most heating potential of all three cases–
That using 22° C (71.6° F) yields the most cooling potential of all three cases–
The inlet temperature should be determined according to the heating and coolingdemands required for achieving thermal comfort if it can be controlled outside of the outlet temperature for the thermal cycle of the TACE system
–
That although hot water systems or radiant systems could not be replaced based on these results, one form of integration could be to precondition the water that was feeding domestic hot water or radiant system, whereas the TACE systems become a thermal preconditioner.–
That there appear to be diminishing returns for the ability to provide hot water as the inlet water temperature increased, while conversely, the cooling potential improves as the inlet water temperature increased.Although the cooling potential of the TACE system was not investigated initially as part of this thesis, conditions exist that suggest that the TACE system can provide free cooling to the building under certain conditions – as shown in Table 6.2, there was more cooling energy available than heating energy in the New York climate zone. In order to provide cooling with TACE, the outside air temperature must be lower than the comfort range within occupied space while the temperature in the space with additional cooling would naturally be higher than the comfort zone. This condition was actually quite common and happens routinely on warmer winter days and predominantly during shoulder months, as shown in Figures 6.27 and 6.28. As a means to compare the New York results, several cases have been simulated for the Phoenix, Arizona and Amsterdam, Netherlands climates. These comparative cases are detailed in Section 6.4.3.1.
6.4.2.1.2
Results of Heat and Coolth Harvesting by Flowrates
The results as shown in Table 6.2 compare flowrates in the functional mode as heating or cooling measured in terms of annual energy captured measure in kWh/ yr. The 0.625 and 2.50 l/min (0.165 and 0.66 gpm) cases were simulated. The 2.50 l/min (0.66 gpm) flowrate case can produce more energy, 272.70 kW/hr heating energy more than the 0.625 l/min (0.165 gpm) case - but at a reduced temperature, 9.03° C (16.25° F) lower than the 2.50 l/min (0.625 gpm) case. The same behaviour was observed from the simulation of Coolth, where 2.50 l/min (0.66 gpm) case stored 105.38 kWhr/yr more Coolth than the 0.625 l/min (0.165 gpm) case, though again at a lower temperature, 5.37 kWhr/yr. As shown in Figures 6.29 and 6.30, the power available daily shows diurnal and seasonal energy availability. Understanding the pattern of potential Heat and Coolth was critical to developing the system design to be able to access the energy as well as in developing the control logic in the EnergyPlus simulation.
TIME (mo) 0 01 02 03 04 05 06 07 08 09 10 11 12 -1000 -0800 -0600 -0400 -0200 0 0200 0400 0600 0800 1000 PO
WER PER AREA 22°C (W/m2)
NORMALIZED POWER vs TIME (0.165 GPM)
-1100 -0800 -0600 -0400 -0200 0200 0400 0600 0800 1000 PO
WER PER AREA Gr
ound T emper at ur e (W/m2) 1200 1400 0
FIG. 6.29 MVP Prototype I comparison of power per area at 0.625 l/min (0.165 gpm) flowrate using ground temperature and 22°C (71.6° F) as inlet temperatures.
TIME (mo)
0 01 02 03 04 05 06 07 08 09 10 11 12
PO
WER PER AREA 22°C (W/m2)
NORMALIZED POWER vs TIME (0.66 GPM)
PO
WER PER AREA Gr
ound T emper at ur e (W/m2) -1000 -0800 -0600 -0400 -0200 0 0200 0400 0600 0800 1000 -1100 -0800 -0600 -0400 -0200 0200 0400 0600 0800 1000 1200 1400 0
FIG. 6.30 MVP Prototype I comparison of power per area at 2.50 l/min (0.66 gpm) flowrate using ground temperature and 22°C (71.6° F) as inlet temperatures.
While power per unit area appears to be significant as shown in Figures 6.29 and 6.30, in both cases, the low simulated temperature differentials, when including the energy needed to move the fluid, reveals a system that cannot compete with contemporary highly concentrated energy used in current efficient systems that use electricity and natural gas as primary sources. Depending on the application, or end use, one could modulate the flowrate depending on the most impactful use towards a particular demand. Where more temperature but less energy was desired, for example, the lower flow might be warranted, wherein other conditions, the high flow with lower temperatures but more energy might be warranted.
6.4.2.2
Analysis of HVAC Scenarios at Multiple Scales
The sub question addressed in this chapter was initially directed towards understanding what HVAC system could best be integrated with the TACE system and was intended to find the supportive synergies in system combinations. Initially, it was the intention of this study to offset the energy use of a variety of HVAC systems by directly augmenting the heating and cooling loops at the terminal delivery of the heating and cooling systems. Based on the initial results of the 12 Module Array, the fluid temperatures as demonstrated in the simulation in Figures 6.27 and 6.28, were significantly more moderate than those which were used by conventional HVAC systems (e.g., Fan Coil Unit, Variable Air Volume Unit, Chilled Beam, etc.) which operate at temperature ranges from 12.8° C (55° F) for cooling and 60° C (140° F) for heating.
In the observed simulated temperature in the standard HVAC systems, it quickly became apparent that the temperatures that could be captured and stored from the TACE system were not enough to impact existing heating and cooling systems; therefore a new approach was needed to make use of the harvested energy. In the round of simulations used for generating the following results at the Bay and Zone scales, the TACE system used radiant heating and cooling panels as the terminal delivery for heat and coolth. This radiant system was decoupled from the primary building heating and cooling system, which remains as described in Section 6.4.1.3 and as shown in Figure 6.19.
6.4.2.3
Energy Use Intensity Reduction Potential MVP Prototype I: Bay
Scale
The bay-scale energy model simulations were run using the three different building envelopes, as described in Section 6.4.1.2. The Bay Scale Simulation 1 was
established as the baseline for EUI improvement from which results of the other two cases were compared.
The results are shown in Table 6.3 of the Bay Scale Simulation 1 of the Howe Center with the existing envelope show an annual average total EUI for the Bay Zone of 870.0 MJ/m2 (76.6 kBtu/ft2).