This is an article primarily by Richard Ellenbogen that estimates projected annual operating costs and emission reductions for New York commercial facilities when the new building codes are implemented.  It is also an example of how peer review should be done.

Heat Pump Hype

I am a long-time critic of the New York State Energy Research & Development Authority’s (NYDSERDA) biased promotion of all green energy technologies.  Their description of cold climate heat pumps is a good example: “Today’s cold-climate heat pumps are a smarter, more efficient option to keep your home comfortable all year long. These all-in-one heating and air conditioning systems are environmentally friendly, extremely efficient, and affordable to operate.”  In another example, they breathlessly exclaim that heat pumps outsell gas furnaces for the second straight year.  This claim uses national figures and could be solely the result of new building sales that are much stronger in southern states where heat pumps are a cost-effective choice.  Ellenbogen addresses the affordability claims below.

Ellenbogen Heat Pump Experience

Ellenbogen installed geothermal heat pumps when his house was completed in 2004.  He has 21 years of experience with them and has maintained a database of the performance and costs.  His monitoring system includes temperature sensors on the inputs and the outputs of the wells and water flow.  Because he uses a geothermal system, he can rely on it even during the coldest periods when air source heat pumps cannot extract enough energy from the air to keep the house warm.  Furthermore, his system uses deeper wells than are currently allowed by law that were legal when the system was developed.  They are also open loop which greatly increases their efficiency but that is also no longer allowed. In his configuration, his heat pumps can pull 7 tons of heat transfer per well where current geothermal wells are limited to about 2.5 tons per well.  As a result, his system can achieve a Coefficient of Performance (COP) of about 5.5 whereas current Geo-thermal systems can achieve a COP of about 3.5 with the restrictions on well depth and having to be closed loop.  During long periods of cold temperatures that force the heat pumps to run for extended periods, the well temperatures can drop and the efficiency of the system decreases so it will use more energy.

One of the things I admire as a techno-weenie is Ellenbogen’s quantitative nature.  He built his house “as a science project to satisfy his intellectual curiosity” and it has yielded an enormous amount of data. When the Indian Point nuclear station was operating, he ran a calculation and found his geo-thermal system was about 7% more carbon free than his 95% efficient modulating gas boilers that were originally installed as a backup in case of a power failure.  After New York politicians shut down Indian Point the carbon emissions of local electricity increased and the GHG emissions advantage vanished.  Given his concerns about GHG emissions he decided to figure out a cost and energy comparison.  He turned the heat pumps off this winter and used the duplicate gas system to compare with multiple years of data with the heat pumps operating.