The fast rise of green construction technology is encouraging, particularly during this time of economic uncertainty. Green projects—mostly in the form of energy-efficiency building retrofits—lately have been working their way into the market as funds for new projects have evaporated in the credit crisis. However, many of these systems are not performing as touted, especially cleverly hyped geothermal heating systems that are plagued with inflated savings claims and deficient designs. These deficiencies have been slowing acceptance of a basically sound and environmentally sensitive approach to design and construction.
Geothermal heat pumps are one example of the problem. 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.
Slick salespeople are not the only ones to blame. 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. Water temperatures in lakes, ponds and aquifers likewise vary. Both issues have a direct impact on the sizing of heat pumps, design of the overall geothermal system and the cost and financial performance of the completed project.
Is geothermal HVAC the same as renewable energy? Not quite. When you consider the inefficiency of the national grid and its dependence on coal-fired powerplants, the greenness quickly fades. Still, geothermal HVAC is excellent technology as long as it is carefully evaluated for project sites by experienced professionals before the drill rig arrives. The success of geothermal systems will depend on new educational courses for engineers, specialized craft training for plumbers, pipefitters and other installers and straight talk to owners about the variable benefits.