Economical Advantages in Using Conventional Energy Supplements in the Design of Geothermal District Heating Systems

Abstract

Most geothermal heating systems are designed to handle the maximum load anticipated during a normal heating season. Typically, this load is associated with an ambient temperature of near 0°F. Since geothermal water usage increase exponentially as the load demand increase, designing to handle such a high peak load results in a very low usage factor (less than 20%) for the heating season. This means that less that 20% of the energy that could be supplied by a geothermal source is actually used. Designing for peak loads to occur at higher temperatures (e.g. 20°F) and using natural gas as a supplement below that temperature, results in significant increased in geothermal utilization and overall natural gas savings. The economic tradeoffs in determining the optimum design temperate are discussed.