Tax Breaks for Ground Loop Systems

With the signing of The Emergency Economic Stabilization Act of 2008, H.R. 1424, the Federal Government has put their money where their mouth is and have acted to make geothermal heat pump systems a more attractive HVAC alternative.



Commercial geothermal heat pump installations now qualify for a 10% tax credit, with no cap on the credited expenditures!

For commercial installations, an ITC is provided for geothermal heat pumps equal to 10 percent of the expenditures, including allocable labor costs for facilities placed in service after October 3, 2008. There is no cap on the amount of expenditures which can be used for the credit (and no cap on the credit itself). In addition, geothermal heat pumps are eligible for Modified Accelerated Cost-Recovery which provides for depreciation over 5 years. The credit is determined by the cost of the system. However, if the equipment is financed by any subsidy program (federal, state or local) or with tax-exempt bond, the basis of the equipment must be reduced by the amount of the subsidy. Contrary to the residential credit, on commercial applications the units do not need to be Energy Star rated to apply. To collect this credit, the taxpayer would need to complete IRS Form 3468. The form will need revision by the IRS to reflect the addition of geothermal heat pumps.

Every little bit helps to get these highly-efficient systems to pencil out. Uncle Sam has lent a hand to owners and designers who wish to utilize this exciting technology!

Heat your showers for FREE

Earlier in this series of articles, I discussed using the waste heat in available on-site water-based sources to heat water. Essentially, you just add a water-to-water heat pump system that allows you to move a lot of heat to a useful function with the expenditure of just a little energy.

Wouldn't it be nice if you could do this sort of transfer of heat from a waste source to a useful function without requiring the addition of a compressorized system?

Well, in existing refrigeration systems, there already exists a source of heat that is usually of a temperature that can provide useful heating for a domestic hot water application without need for additional compressors: The compressor superheat.



In a refrigeration process, where cooling is the desired function of the compressorized system, this compressor superheat is essentially waste heat, and serves no useful purpose. It is simply thrown away to the environment through whatever heat rejection process the system employs. But this compressor superheat was put into the system by the energy used to run the compressor, and therefore was paid for once by the operator of the equipment. Instead of paying for it again in the operation of the heat rejection fan or cooling tower, why not instead use it for something, saving the heat rejection costs and reaping a real benefit?

It was this sort of thinking that prompted Florida Heat Pump to develop their HRP Heat Recovery Package (pdf). This is an add-on heat exchanger that transfers the compressor superheat directly into a domestic hot-water source--using double-walled heat exchangers to protect the potable system.



The heat from the desuperheater system provides supplemental heat to the domestic hot water system any time the compressor operates--in heating or in cooling. This can greatly reduce the amount of electric or gas heat required for water heating--even completely displacing this direct heating during many times of the year, depending on the building loads and use of the space.

(Note, however, that the compressor superheat is lost to the heat pump space heating process and therefore the space heating capacity of the heat pump will be reduced by the capacity of the desuperheater. As long as this is taken into account in the sizing of the heat pump, this presents no problem to operation.)

But water-source heat pumps represent only a small part of the compressorized systems that are exisiting or installed every year. It seems there is an opportunity for taking advantage of this same heat source on many other systems and on existing equipment, too.

That is where the Heat Harvester Heat Recovery System can be used to great effect. This heat recovery system is a stand-alone desuperheating device that is pre-designed for various compressor system capacities and is available for retrofit on existing or new systems.

How much heating potential is there? Well, Heat Harvester has provided an interesting analysis of the desuperheat capacities of compressorized systems:

Size of Air Conditioning System tons	Gallons of Hot Water per Hour	Gallons of Hot Water per Day
3	15-to-25	180-to-300
5	25-to-40	300-to-480
10	50-to-80	600-to-960
20	100-to-160	1200-to-1800
30	150-to-240	1800-to-2880

These systems can be economically installed into just about any compressorized systems using positive displacement compressors: Scroll and Screw air-cooled chillers, Rooftop packaged units, Condensing units, CRAC units, you name it. Since the Heat Harvester heat recovery system consists of a package with a heat exchanger and a pump, the installation basically involves a little refrigerant and water piping. And in a cooling-only application, all of the heat recovered would have otherwise been lost to the environment.

Ultimate Florida Heat Pump Cheat Sheet

One of the difficulties our customers have with Florida Heat Pump is that their product offering is so wide, that it can sometimes get confusing: Which models have ECM motors? Which have scroll compressors and which have recip? What sound packages are available for a given model, etc...

So, in the interest of clarity and ease of use, we've pulled together all of this information into one convenient place: The Ultimate Florida Heat Pump Cheat Sheet

Reducing Ground-Loop First Costs

Ground-Loop heat pump systems perhaps have the greatest potential for reducing energy use in the built environment than any other space-conditioning technology now in use. This potential has been long recognized by the EPA and the DOE, and represents a great opportunity for owners and designers attempting to create systems that out-perform those that are commonly built in this region.

They also have a reputation for being expensive--very expensive.

And with drilling costs in this region historically being quoted as high as $15/lineal foot, this reputation is well deserved. These prices usually put this technology out of the range of economic justification for typical projects.

So what can a designer do to minimize costs, yet still provide the energy benefits of this technology?

Add a cooling tower.

Hybrid Systems

To understand how adding a cooling tower to a ground loop saves costs, first you have to understand a simple concept about closed ground-loop systems. While the ground loop is often referred to as a "heat exchanger", the ground-loop (and the ground it occupies) acts more as a leaky heat storage battery. Unless there is sufficient ground-water movement through the well-field, most of the heat that is rejected into the ground remains there throughout the year unless it is later removed by the ground loop itself.

That means that over time, if the heat added is not balanced by heat removed, the ground temperature will continually increase over the seasons, increasing loop temperatures and decreasing system efficiency.

(graph showing increase in temperature over time for imbalanced loop of differing bore hole numbers. From here)

The best situation for a designer is when the heat added to the ground over the course of the year (by the process of cooling the building) is balanced by the amount of heat removed from the loop (by the process of heating the building). But a heat-pump does not just move heat from one source to another. Because a compressor is needed to perform this work, a heat pump always adds the heat of compression to the equation. This is a benefit in heating, since the heat of compression is added to the amount of heat moved from the loop to the building. This is a hindrance in cooling, since this compressor heat is added to the heat moved from the building to the loop. In practice, about 1.2 to 1.8 tons of heating are needed to balance out 1 ton of cooling. This means that many ground loops will see an imbalance where more heat is rejected to the loop than is removed from the loop over the course of a year. This effect can be significantly compounded (or mitigated) by the configuration and use of the building served--buildings with significant yearly cooling loads will be more affected than by buildings dominated by heating loads.

A ground-loop designer typically combats this effect by increasing the volume of the well field by increasing the number wells to a point where the relatively small amount of heat-leakage out of the well-field and added volume is enough to account for the imbalance of the system and minimize the heat gain. Thus ground loop well-fields are often sized due to the minimum requirements of either heating or cooling demand for the building. Cooling-dominated well-fields are more common throughout the US, especially in the southern portion of the country.

If the designer could correct for this imbalance and build the loop to the smaller size required by the heating load of the building, then fewer wells would be needed, and thus the overall cost of the loop would come down. One of the most cost-effective ways to provide extra cooling to balance out the loop on such a system is by way of a cooling tower or fluid cooler. When a cooling tower is used in conjunction with a ground loop, you have what is called a hybrid system.

Hybrid systems can be extremely effective at bringing down first costs of ground loop systems. A study by Kevin Rafferty of the Oregon Institute of Technology found that hybrid systems can reduce the cost of a ground loop by as much as half for some systems:


But can we expect similar reductions in first cost for the Puget Sound region, where we have a generally cool climate and a long heating season? For some systems, it appears the answer is yes. A presentation by Scott Hackel of the University of Wisconsin at the ASHRAE 2007 summer meeting investigated the cost savings possible using hybrid systems throughout the country. His study showed very significant reductions in ground heat exchanger (GHX) loop lengths for school, retail and office applications in the Seattle region:

(Click for larger image)

Hybrid loops may just make the next ground loop you consider pencil out.

Heating Your Showers with Your Cooling Tower

Most large buildings are throwing heat away for many hours of the year. In a large facility, this is most often accomplished by way of a cooling tower. Commonly, the cooling tower cools water from about 95º to around 85º. Many hundreds of thousands of btuh's from lighting, solar loads, equipment and any of the myriad heat load sources in these facilities are rejected to the atmosphere in this cooling process. Wouldn't it be nice if you could reclaim some of that heat and use it for a something that always requires heat input, like domestic water heating?

Sure, you could take the cooling tower water and run it through a heat exchanger to preheat the makeup water from the city utility before it enters your hot water heater, but that would only offset part of the heating load. The highest temperature you could reach would be on the order of 93º--any higher would require artificially allowing the condenser water to heat up, penalizing the efficiency of the chiller it serves.

It would be a lot more convenient if there were some way to use the heat in the condenser water loop to create higher temperature water--water that could be directly used to heat domestic water. And that is exactly why Colmac developed their HPW series of water-to-water heat pumps, specifically designed for domestic service.

These heat pumps include a circulating hot water pump and a double-wall heat exchanger as required for domestic service. They can directly heat the domestic water to temperatures of 140º or higher, using water as cold as 55º. This means that they can actually be used to pre-cool chilled water to reduce load on a chiller, as well as take waste heat out of a condenser line.

Florida Heat Pump also has a full line of water-to-water heat pumps for similar heat recovery jobs. These are a competitive alternative when domestic water service is not required, or where an external heat exchanger can be provided to meet domestic service requirements. These are also very flexible alternatives to traditional central plant chillers, with the ability to reverse cycle and provide hot water or cold, and come in convenient modular sizes for ease of installation and efficient capacity staging.

And there is no reason to stop at considering condenser water systems for sources of heat. Using water-to-water heat pumps, any source of flow that carries waste heat can be utilized to provide usable energy for your system. Why not pump heat out of your sewer lines? Luckily for the creative energy engineer, smells aren't transfered by the refrigeration cycle!

ECM Motors and Heat Pumps

What are electronically commutated (ECM) motors?

These are single-phase motors running off of a DC power signal (rectified, if running off of an AC power source) that use an electronic method of switching power to alternating coils around the rotor in order to induce a rotating magnetic field. (More information available here).

They are much more efficient than traditional electro-mechanically commutated motors, and local utilities offer rebates for their use. But ECM's also provide additional benefits on heat pump applications.

Because the motor speed is controlled by the speed at which the magnetic field rotates around the shaft, and that speed is controlled by the electronic switching of the ECM, these motors are inherently variable speed devices. When applied in equipment, this variable speed capability is either used directly, providing a variable speed capability on the fan, or, more commonly on packaged refrigeration equipment, as a self-balancing mechanism to provide a fixed discharge airflow, independent of external static pressure.

Additionally, the electronic switching in these devices allows for more torque to be delivered to the rotor, allowing for greater static pressure capability on the fan it is driving.


Florida Heat Pump has capitalized on these advantages by offering ECM motors on their heat pump products. FHP ES and GS series heat pumps are supplied with ECM fan motors for efficiency, ease of air balancing, and unmatched static pressure capacity.

Let's consider those last two further. FHP uses the ECM to self-balance their units to a set leaving air flow (low, medium and high settings controlled by jumpers on the control board) regardless of external static on the fan (within a given range). Let's look at the fan table for these units (2 1/2 ton ES030 shown):

(click for larger image)

You either get 850, 1000 or 1150 CFM at anywhere from 0.10" to 1.2" of external static pressure. All you do is set the jumper to the flow rate you want to see and then the fan motor will automatically adjust itself to provide the airflow desired.

But look at that range of static pressure! Typical heat pump fans might only provide three tenths of an inch or so external static. Having over an inch available (smaller units offer about 0.80" external) is a game changer, making it very possible to have improved filtration (LEED® points) or air side economizers (energy code requirement) on these inherently efficient heat pump systems!

And these advantages are above and beyond the improved energy efficiency that is realized by using the more efficient fan technology.

ECM motors improve WSHP efficiency, reduce balancing labor and widen the applicability of these already efficient systems.