Nearly all conventional residential and light commercial buildings use refrigerant type air conditioning systems for cooling the interior space. These units all have the familiar outdoor condenser units. Variations include packaged heating/cooling units and air source heat pumps. All use outside air to cool the refrigerant, while rejecting heat into the surrounding air. These units will be referred to as "air source" equipment.Comparisons between Geothermal and conventional air source units are convoluted because of the sharp decrease in efficiency of air source equipment as a function of outside air temperature. Manufacturers of air source equipment are quick to post impressive EER and SEER (Seasonal Energy Efficiency Ratios) numbers on their "high efficiency" models, but a closer examination of the actual performance data shows that these lofty numbers do not correlate well under realistic installed conditions. A typical example of a 3-ton air source unit shows manufacturer's EER as 12.0. However, a closer look at performance values yields a calculated EER value of 10.5, at rated conditions. This would represent a daytime temperature of about 32.2° C.
| EER Comparison Geothermal v. Air Source Cooling | |||
|
Outside Temp |
32.2°C |
37.7°C |
43.3°C |
|
Geothermal |
17 |
17 |
17 |
|
Air Source |
10.5 |
9 |
8 |
When the outside temperature rises to 37.7°C, the air source EER drops to 9.2, which represents a reduction in efficiency of 12%. If outside temperature rises to 43.3° C, the air source EER drops even further to 7.7, which represents a reduction in efficiency of 27%. This means that the unit is requiring 27% more electricity to yield the same cooling.
Another aspect of the air source units is that the cooling ability of the unit is also a function of outside air temperature. A typical 3-ton unit can put out 3 tons of air conditioning when the outside air temperature (at the condenser) is 35° C. But, if the outside air temperature rises to 43.3° C, the unit can only put out approximately 2.6 tons, a reduction of 14%. Condensers that are clogged with dirt or debris will have even further reduction in efficiency.
The performance of an appropriately designed geothermal system is independent of changes in outside air temperature and humidity. Since the temperature of the earth where the geothermal occurs is relatively unchanged throughout the year, Geothermal efficiency of both heating and cooling seasons is fixed. Typical efficiency for a 3-ton Geothermal Systems in cooling mode with entering water temperature (EWT) of 20° C is approximately 17 EER. The following table and chart gives a comparison of Geothermal to air source units as outside temperature varies:
As indicated in the table above, Geothermal systems for air conditioning are considerably more efficient than the conventional air source units. Simple calculations show that energy costs for a Geothermal are nominally 40% less than air source; 50% less than air source at 100 degrees; and can be as much as 55% less than air source as temperatures rise further. This efficiency analysis is attempted to examine like units for an "apples and apples" comparison. It has not included the effect of a Geothermal “desuperheater”, the hot water feature capability. With warm-hot climates, if the Geothermal is used to provide supplemental hot water to a conventional gas or electric water heater, the efficiency disparity becomes even greater. With the Geothermal “desuperheater” (HWG – Hot Water Generator) in service, hot water in warm-hot climates such as India essentially becomes free.
The Savings Calculator is an approximation
based on our experience to date and uses Conventional Central Air-conditioning
as the benchmark for comparison. The Savings Calculator should
be used as an indicator only. Geothermal India is able to calculate
specific and accurate savings for each and every project after
in-depth analysis of your proposed installation.
Contact us now to find out how much we can save for you!
Contact us now to find out how much we can save for you!