Great article (“The State of Energy: Revisited,” March). It lays out the energy economic arguments in a very clear and concise manner. Matter of fact and to the point.
Kevin L. Wyman, PE, LEED AP
South Windsor, Conn.
I read the article “The State of Energy: Revisited” with great interest. It provided me with a great overview of the economics of the various forms of renewable energy, which will help me explain to clients which is the best way to go when retrofitting/designing a project.
One thing I hope the author can provide some insight on is ground-loop heat pumps. I know they have been around for some time. While it seems the energy efficiency is good, the cost is high. Under what circumstances are they an economic solution?
Raymond Niu, P.Eng.
Giffels Associates Ltd./IBI Group
Ground-loop heat pumps have been around for some time, but there are some new developments.
Ground-loop heat pumps are total-electric systems and, therefore, suffer from the question of carbon-dioxide emissions. Until we solve the coal-fired pollution/cost problem, it will be difficult to base a national policy on a total-electric economy. Further, the systems primarily are best in northern climates, where both heating and cooling are required, because the heat removed from the ground during winter will be replaced during summer, maintaining a uniform annual ground temperature.
The biggest new development is the implementation of a 30-percent residential tax credit for the total cost of a geothermal heat pump (GHP). This is better than the tax credit for other residential HVAC systems and great enough to make GHP competitive where conditions are favorable. Generally, GHP use 25- to 50-percent less electricity than conventional all-electric heating or cooling, saving 44 percent compared with air-source heat pumps and 72 percent compared with electric resistant heating.
In general, residential GHP cost $2,500 per ton, or roughly double a conventional HVAC system. The energy-efficiency ratio (EER) for cooling typically is 13 to 18; however, two-speed systems have offered EER of up to 25 in special cases. On the heating side, the Energy Star rating for coefficient of performance (COP) is 2.8; therefore, for each 1 kw of input, GHP will produce 2.8 kw of heating output. Some manufacturers' COP are up to 5.
Installation costs depend on geology, hydrology, and land availability, all of which must be investigated before a GHP is selected. There are closed-loop and open-loop systems; moreover, they can be horizontal or vertical. Horizontal systems typically use polyethylene pipe and are 4- to 6-ft deep, while vertical systems require wells 100- to 400-ft deep. Open systems may have U.S. Environmental Protection Agency or local code issues.
GHP systems are especially cost-effective where natural gas is not available and electricity is cheap and reliable.
Alfred E. Guntermann, PE
New Haven, Conn.
I wanted to personally thank you for today's (March 18) Engineering Green Buildings newsletter.
The U.S. Green Building Council write-up on the economic-recovery bill that you highlighted (“President Obama Signs Economic Recovery Bill With Billions for Green Building”) was incredibly useful. I had recently been tasked with “going through” a 121-page analysis of the stimulus package when I received your newsletter. Needless to say, that article, along with the related summary from the House Committee on Appropriations, made a daunting task much easier and spared me an Everest-esque search online for such a write-up.
I imagine you don't often get personal feedback on the newsletter. I just wanted to share my thanks for the timely content.
Extech Instruments, a FLIR company
(Editor's note: To subscribe to HPAC Engineering's monthly Engineering Green Buildings electronic newsletter and/or its semimonthly Fastrack electronic newsletter, go to http://hpac.com/newsletters/subscribe.)
I really enjoy the many helpful and useful articles HPAC Engineering makes available. In our busy lives, we often forget to stop and say thanks for this information, which helps make our jobs easier to perform.
Dennis H. McKee
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