Building going geothermal
More and more new commercial buildings are going geothermal as a viable means to reduce energy costs. The 40,000 square foot Central Iowa Shelter & Services building, currently under construction south of downtown Des Moines, features a geothermal system. The mechanical engineer for the project, Alan Langley of Alvine Engineering, says “the trend in Iowa is more buildings are using geothermal systems, in fact about 80% of the schools we design use geothermal systems. Offices and healthcare are good candidates also.”
Alan also adds “the trend started in Iowa when the utility companies started to provide hefty rebates for energy conserving systems like geothermal”. Basically, the utilities pay companies to lower their energy usage rather than bring on a new power plant costing millions of dollars.
A commercial system costs $16-$20 per square foot so the cost for a geothermal system for a 10,000 square foot building would be $160,000 to $200,000. The payback is typically 5 to 7 years and from day-one heating and cooling costs should be reduced by 35%-45%.
A geothermal system takes advantage of the earth’s constant temperature. The diagram shows the earth’s temperature near the surface in Iowa to be about 52 degrees. Therefore, the temperature of water when circulated through a closed system of vertical or horizontal loops nears a constant 52 degrees. The loop is tapped into by mechanical equipment which either transfers heat to the loop during the summer or takes heat from the loop during the winter.
An amazing result of the loop is the potential transfer of energy within a building during the winter. The interior zones of a large office building many times require year-round cooling while the perimeter usually requires heating. Mechanical equipment removes heat from the interior zone and transfers the heat to the loop. Mechanical equipment at the exterior zone reverses the process and removes the heat from the loop providing heat where it is needed. Now that is being Green!!!
