Ground Source Heat Pump Update
Andrew Holguin and Kaitlyn Thatcher build one of the geo-exchangers outside of WCEC’s laboratory
Traditional geo-thermal techniques require expensive drilling rigs that can bore vertically 200 feet into the earth. Large Diameter Earth Bore (LDEB) and Directional Bore installations aim to reduce these costs by reducing the drilling depth while maintaining an adequate amount of heat exchange with the earth. The LDEB’s innovative system utilizes a 24” diameter 20’ deep helical coil constructed of 1/2” diameter HDPE tubing placed into the bore hole and backfilled with dirt from the drilling, sand, rock, or other fill. Drilling for these shallow bore heat exchangers is quick, and far less expensive than conventional techniques. Typically each bore may take less than an hour to drill, allowing around 8 to be completed in a typical work day. A day of work may yield around 150 linear feet of heat exchange depth, however on a per foot basis the LDEB exchanger has more capacity due to the effective increase in surface area. The Directional Bore system drills many shallow lanes across a plot of land creating a large amount of heat exchange surface area in a short amount of time and at a reduced cost to more conventional GSHP.
In collaboration with the CEC and our Utility partners, WCEC is able to expand the scope of this project to include an even greater number of field tests. Ultimately, this research will lead to a more comprehensive understanding of the benefits and shortfalls of a more diverse set of GSHP strategies.
Directional Bore at Rio Mondego: Horizontal Geo-Thermal Shows Promising Results
A horizontally bored residential ground source heat pump (GSHP) system was installed in the Pocket neighborhood of Sacramento in mid-2013. The WCEC installed monitoring equipment on this system and has been collecting continuous data since July 17, 2013.
The graph on the top shows the efficiency of the heat pump at specific ground-loop water temperatures, and the graph on the bottom shows the percentage of runtime the heat-pump is running at specific water temperatures and the amount the heat-pump is running in either stage 1 or stage 2 heating/cooling. Of particular interest is the overall percentage the heat-pump runs at stage 1 heating or stage 1 cooling versus stage 2. For heating, the heat-pump is running in stage 1 only mode for roughly 90% of the entire runtime. For cooling, the story is quite similar, running in stage 1 for approximately 80-85% of runtime. More specifically, well over 50% of the cooling being done by the heat pump is between the water-loop temperatures of 80-90F, leading to a running EER efficiency during that time between 17-14—a significant overall efficiency rating for a residential system. Likewise, during the majority of heating runtime, the heat-pump’s efficiency is at an EER of 15 and above.
Large Diameter Earth Bore at Capay House
Kaitlyn Thatcher installs LDEB helix inside a culvert pipe for the Capay House installation.
Another large diameter earth bore (LDEB) geo-exchange field is being constructed in Capay California. The construction of the field here is similar to the LDEB at West Village project, but instead of back filling with earth or cobble, the bore is left empty and filled with water. The water is being used as a thermal storage medium for use with a residential split system heat pump. In addition to geo-exchange, there is a cooling tower that can be operated to reject additional heat.
In the last 3 months, we’ve completed construction of our hybrid thermal storage ground heat exchangers. The process involved constructing “braids” of HDPE tubing that were placed inside HDPE culvert pipe. The ends were plastic welded with large plates to create roughly 450 gal tanks. The site is being prepared for installation currently. In the next weeks, 36” diameter bores 23-feet deep will be drilled and the tanks will be placed. The volume around these bores will be backfilled with concrete and the tanks will be buried. The hybrid ground heat exchangers will be connected to the GSHP system and cooling tower. The system should be ready to collect data in the nextt summer cooling season.
Emerging Technolgies Summit: October 20-22, 2014
What is the ET Summit?
From October 20-22, more than 500 stakeholders in the energy efficiency and demand response emerging technologies sector will gather for an interactive conference at the Parc 55 Hotel in San Francisco to learn, ideate and debate the intersection of utility programs, technology, market drivers, customer engagement, policy and implementation in order to impact the advancement and adoption of emerging technologies.
The ET Summit's presenting Sponsor is The Emerging Technologies Coordinating Council (ETCC). To help achieve the state’s ambitious energy savings goals, Pacific Gas and Electric Company, Southern California Edison, Southern California Gas Company, San Diego Gas & Electric, Sacramento Municipal Utility District, the California Energy Commission with oversight from the California Public Utilities Commission created the ETCC.
The ETCC provides a collaborative forum for its members’ to exchange information on opportunities and results from their Emerging Technologies activities. Efforts are focused on identification, assessment, and support for commercialization of energy-reducing technologies, such as advanced lighting, water heating, and air-conditioning systems, for residential, commercial, agricultural and industrial customers. ETCC members are committed to helping achieve California’s energy-reduction goals by screening potential technologies, assessing them to validate performance and customer acceptance, performing in-situ demonstrations and recommending the proven winners for IOU customer education and rebate programs. The ETCC is particularly interested in technologies that offer large energy savings and rapid market penetration.
- » Opening night reception at The Exploratorium
- » Thought leaders engaging in cross-cutting breakout sessions
- » Showcase of the latest innovative technologies and services
For more information including a list of the distinguished presenters, organizations involved and how to register, please go to: Emerging Technolgies Summit: Accelerating Innovation in Energy Efficiency