Uncertainties Plague Geothermal Heat Industry
Geothermal heat pumps continue to gain popularity as an alternative energy source. This energy technology doesn't come without uncertainties though. In fact, as ENR recently described it, there are significant problems with the geothermal industry: "[M]any of these systems are not performing as touted, especially cleverly hyped geothermal heating systems that are plagued with inflated savings claims and deficient designs."
The article goes on to describe three primary problems with the geothermal industry:
- "Their performance often is only superficially studied by equipment insiders whose main interest is selling more systems. As a result, the construction industry lacks a trusted set of independently audited best practices for design, installation and maintenance. This issue is becoming increasingly important as engineers scale up geothermal systems for larger buildings."
- "In particular, the coefficient of performance (COP) rating for a heat pump usually does not take into account the efficiency of the entire system. During design and installation, many variables can creep into that equation, such as the amount of electricity needed to pump water through piping loops, heat escaped through poorly built ductwork and seasonal imbalances in how much heat is dumped or pumped out of the ground. These all can compromise the COP and extend the payback time for systems."
- "Industry promoters working for owners, architects, engineers and contractors have done a poor job of educating consumers on the benefits and drawbacks of geothermal HVAC. There are large variations in average ground temperatures by region, but geothermal advocates would have potential customers believe ground temperature is a constant 55°F."
ENR's concerns about geothermal energy go to a larger point: owners and contractors should avoid promises of energy savings. Unless you are a performance contractor, there are too many variables during operations and maintenance that impact actual energy use.
What are your experiences with the risks and rewards of geothermal heat pumps?
What are your experiences with the risks and rewards of geothermal heat pumps?
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The challenge with complex, location dependent systems is that one cannot guarantee product performance. The payback time for these systems will vary according to location, depth of installed system, equipment/working fluid selection, and HVAC load. Each system will have a unique payback, which presents challenges in broadly marketing the technology. Assessments focused on regional applications may be of greater use.
To the point on average ground temperature, temperatures do vary across the US. 55oF is a reasonable estimate. Generally, ground temperature decreases the further north you are (FL average is 75oF, MI is 47oF). For VA, the ground temperature averages 59oF. For a list of temperatures in various states, refer to http://is.gd/5xndv.
The bigger picture is that geothermal heat pumps enable owners to reduce their reliance on electricity or natural gas for cooling and heating needs. While the payback may vary, carbon dioxide emissions are avoided significantly reducing the operating carbon footprint of a building.