Recent Maryland legislation formally recognizing geothermal heating and cooling (GHC) system as a renewable energy resource has great potential for increasing the adoption of ground source heat pump technology. The Geothermal Exchange Organization (GEO) is to be applauded for their work on this initiative and their continuing efforts with other states and the United States Congress. Beginning in 2013, Maryland residents who commission a GHC system will be eligible for Renewable Energy Credits, similar to the existing solar (SREC) program.
The development in Maryland follows the recent roll-out of the UK Renewable Heat Incentive (RHI) that provides financial incentives for the generation of renewable heat from a variety of sources, including ground source heat pumps (GSHP). Because of uncertainty in the performance of residential GSHP systems (as reported by the Energy Savings Trust), the UK’s RHI is not yet available for residential systems. For commercial installations that are eligible for the RHI, the incentive is based on the site-specific measured amount of renewable heat generated.
In the US, the addition of energy produced by GHC technologies towards Tier 1 Renewable Energy Portfolio Standards is expected to significantly increase the application of GSHP systems as homeowners will begin receiving Renewable Energy Credits, thus increasing the financial benefits of their GSHP systems.
From the Maryland legislation, the amount of RECs to be awarded for geothermal energy will be determined using web-based calculators. This follows from the commonly used practice for SRECs in which the NREL program PVWatts is used to determine solar energy production from photovoltaic panels. PVWatt accounts for specific installation parameters (panel orientation, climatological measures of solar radiation, etc.) and, because of the spatially uniform production of solar energy, this one-size-fits-all approach is appropriate.
However, field studies of ground source heat pumps typically result in a range of renewable energy production. The Energy Trust Study found a large range in heat pump efficiencies, suggesting that meeting a specific heating demand would result in a correspondingly large range of renewable energy production. The GxTracker™ measures the heat exchange with the ground loop — arguably the most appropriate measure of renewable energy production. Our field observations over the past few months have shown less of a range in performance but a significant range in heating and cooling demand, reflecting differences building efficiency and end-user heating and cooling preferences.
Given the observed variability in heat production from both the Energy Savings Trust study and our own data, developing a one-size-fits-all web-based calculator for GRECs will have its challenges. An alternative would be to follow the UK model where renewable heat production is measured. Using a web-based calculator that is based on actual system performance and measured quantities of GeoExchange would provide a more accurate measure of renewable energy production. In addition, a web-based monitoring system that provides real time data, system alerts, and illustrates cost savings and carbon offsets would have the added benefits of increasing customer satisfaction and consumer confidence.
UPDATE: At the time of this Post, we were so busy watching Maryland, we didn’t see that New Hampshire had passed similar legislation! The NH Bill (SB218) calls specifically for measuring renewable thermal energy.