As my first BLOG, I’ve opted to present an article I wrote a while ago, I welcome your comments and feedback.
First of all, kudos to everyone who spoke out in the recent issues of BIG GREEN (Big Green Digest – 05/05/03) regarding Ground Source aka geothermal heat pumps, it is that passion that will drive the changes we are all striving for….
I would like to convey my take on this, if nothing else, interesting technology. Since 1982, I have lived with a system, installed hundreds of systems, sold material on well over a thousand installations, and designed scores of systems, and prior to becoming a geojunky, I received the UTC Design Achievement Award for Heat Pump Design while working at Carrier Corporation. So although I continue to be a student of the technology, the “scar tissue” I have acquired in the past 25 years has provided me with a perspective that is at least a well-founded bias….
To characterize geothermal heat pump systems with a brief discussion about COP’s and electric generation efficiency is like trying to describe your mother as “a woman with gray hair”… I don’t even know your mother, but I am sure that description does not do her justice.
The geothermal technology is truly multi-dimensional, however, before I embark on a treatise to fully describe the technology and it’s place in the marketplace, I would like to support the concept that it is better to reduce demand then to discuss the most efficient heat/cool source. As an example, the Cambria (GOLD – LEED 2.0) Project reflects an approach that reduced demand (compared to typical office space the square feet per ton was about 650 vs 350-400 sq feet per ton for a typical similar office). This demand reduction was accomplished through the architectural elements of incorporating day lighting, efficient artificial lighting controls, and a raised floor air distribution system to name just a few. However, this reduced demand allowed the geothermal system to be downsized and the entire mechanical system was installed for $11/sq foot (without any of those exorbitant utility rebates). So let’s talk economics….
Perhaps the biggest myth about geothermal is that it does not reflect a good economic choice without rebates… Personally, I am not a big fan of rebates, because they do create an artificial market, where the investments of many businessmen and women are at the mercy and subject to the whims of utility companies. Fortunately, the utility landscape has changed and today the most common rebate/incentives are managed state-wide through a more long term approach through organizations such as the New York State Energy Research Authority (NYSERDA), which is currently offering a pre-qualified rebate of $800/ton.
When discussing economics, it is important to separate the residential market from the commercial market. The HVAC industry in the residential market is plagued with a constantly degrading commodity mentality. There is extreme variation across the country, with Florida being an example of how low it can go. Air conditioning systems with electric resistance heat are being installed for as little as $400 a ton. And in that market I know several contractors who are successful at selling geothermal systems in the residential market albeit at a much higher price tag.
Within, the residential Market there is also a great disparity in the economic realities. Most markets do not have experienced contractors who can price a job with the experience that would allow them to make money without a whole lot of “contingencies” built in. However, I am familiar with contractors who have installed thousands of systems. For example, in Oklahoma, I am familiar with a contractor who is changing out air source heat pumps for $4995 for a 3-ton system, including the loop field and heat pump, and he is making money.
The geothermal “do-it yourself” market is an un-tapped opportunity. I have helped dozens of homeowners, who, with access to a backhoe, were able to install systems for $5-7,000. The development of “Stab” fittings and non-pressurized flow centers has allowed the geothermal technology to be installed almost as easily as installing a washer and dryer (including plumbing and electric hook-ups).
Consequently, it is very difficult to make blanket statements about the economic justification of geothermal HVAC Systems in the residential market.
The commercial market, although very diverse, has a more consistent level of quality and pricing. At the low-end of the spectrum are the gas-electric rooftop equipment/systems, while 4-pipe VAV systems dominate the high end. The typical range for a commercial HVAC System is $8 to $20 per square foot, with local market conditions affecting it up or down. In the past 3 years, all the geothermal projects that I have designed and were installed, fell in the range of $10 to $16.50 per square foot, prior to any rebate. The projects included a dormitory, office building, several schools and a doctor’s office. Rebates provided a discount from $2-$4 per square foot. So, I can emphatically state that geothermal is directly competitive with comparable commercially available technology, and anything the architect can do to reduce the load will manifest itself with an even more competitive geothermal option.
But there are many horror stories out there…. Such as a project that went to bid and the result was a geothermal system that came in at $36/sq foot, obviously blew the budget… I would suggest that engineers who elect to design a geothermal project without the benefit of experience are doing a disservice to their client. The danger of poor design is not only a higher first cost, but also operating costs that are way out of line. I actually performed an energy audit on a facility with a geothermal system, and it turned out that the circulating pump was consuming more energy then all the heat pumps combined, the engineer should have been “Tarred & Feathered”. The conventional engineering mantra of “2X + 1” can kill a good design before it even gets off the drawing table. Let’s go beyond economics….
LOW MAINTENANCE/HIGH RELIABILITY
A comment was made as to “How could geothermal heat pumps have lower maintenance costs then regular DX systems that use the same components?” There are two very significant differences in the stress that is experienced by the identical components in two different applications.
The first is the inherent pressure ratios differences associated with air-cooled condensers vs. water-cooled condensers, and the fact that the stress on the compressor is directly related to pressure ratio. An air-cooled DX system will condense at temperatures 25 to 35 degrees above the air temperature, while a water-cooled condenser will be 12 to 15 degrees above the water temperature. Additionally, for a given air conditioning load, the temperature of the fluid in the ground loop is considerably cooler then the air temperature, further reducing the stress on the compressor.
Secondly, when compared to an air-source heat pump, there are no defrost cycles on a water source heat pump. Consequently, the same components will experience significantly different stress levels, thus increasing the inherent life expectancy for a compressor in a water source heat pump. But what about comfort….
Ideally, in the heating mode for forced air systems, the perfect supply air temperature is one that feels warm to the touch, but not so warm as to cause excessive air stratification. Two extreme examples of an uncomfortable supply air temperature are an air-source heat pump that can supply air at such a cool temperature that it can feel drafty and a conventional furnace that can supply heated air at temperatures as high as 140, which will cause stratification and a sense of having a warm head, but cold feet. A geothermal water source heat pump supplies air at a temperature between 95 & 105, which is ideal.
Perhaps the most comfortable form of heat is in-floor radiant heat, which a water-to-water heat pump can deliver at extremely high efficiencies. A COP of 5.0 is easily achieved when producing water at a temperature of 80-90 degrees.
One of the keys to comfortable cooling is humidity management. Cooling without enough dehumidification can result in a clammy feeling, which is certainly uncomfortable. Water source heat pumps have excellent sensible heat ratios, and as a result of a consistent loop temperature can be sized closer to the load requirements, which minimizes the negative effects of short cycling. How can we be comfortable if we are damaging our environment….
Using Carbon Dioxide emissions as the key parameter of gauging environmental impact, and comparing the New York State Average CO2 emissions per KWH of .957 lbs/KWH to the embodied CO2 for natural gas of 117 lbs/Mbtu a comparison of geothermal to conventional HVAC systems can be made. With an average COP of 4.0 and a 40% improvement in cooling performance and a Natural Gas combustion efficiency of 82% (and adding fan energy impact of 5.8 lb/Mbtu, which is typically overlooked) a CO2 emission reduction of 47.7% is easily obtained. Being located in Rochester Gas & Electric Service Territory would result in a 62.4% reduction. And the ultimate goal would be to source the electricity from a renewable source and eliminate CO2 emissions by 100%.
As we as a society become better at producing electricity a geothermal installation that is “plugged into the grid” will continue to improve in environmental performance, as opposed to an on site fossil burning technology, which will lock the facility into a given emissions level for the life of the system/facility.
Show me an architect who appreciates not having to hide outdoor equipment or try and make a chimney look good and I will show you an architect who likes geothermal heat pumps. Numerous historical renovation projects have benefited from the use of geothermal heat pumps because of being able to maintain much of the original character of the building. As I am writing this, Auburn Memorial City Hall is an example of such a project. For 70 years, the employees of the City of Auburn did not have air-conditioning, not even a window AC Unit. Currently a geothermal system is being installed, and by the time the heat of the summer arrives the system will be operational with no visible sign of the system. The citizens of Auburn will be pleased that they are not only efficiently keeping the facility comfortable, but it is being accomplished without compromising the visual appeal of the building.
Geothermal heat pump systems offer an incredible opportunity, but not just on one front. From simple economics, to comfort, to excellent reliability, to reducing our environmental impact, etc., this technology is commercially available and is applicable on virtually all types of applications, including underground electrical vaults, to ice rinks, to office buildings, to schools, to historical projects, to low income housing, to hospitals to name just a few.
I look forward to hearing/reading your comments.Respectfully submitted,
John D. Manning, PE
Earth Sensitive Solutions, LLC
PO Box 3; Skaneateles, NY 13152