By Don Magglioli
Nov. 3, 2011
When it comes to using alternative heating sources, commercial building owners often overlook geothermal heating and cooling as an option. Truth be told, geothermal is more cost-efficient to install and offers a substantial return on investment for commercial building owners than other conventional systems.
There is often confusion of exactly what is geothermal. Geothermal can mean using hot waters that are naturally occurring below the earth’s surface for either direct-use heating or electrical power generation. Geothermal can also mean simply using the constant temperature of the earth’s shallow temperatures (6 ft. to 1,500 ft. below ground surface) as a heat storage medium. This heat storage is also known as geoexchange. Heat pumps are used to heat or cool the building and the earth is used to store heat. The heat pumps are used to “exchange” the heat from or to the earth.
The three main geoexchange systems are:
Open Loop; and
Standing Column Well.
In a closed loop system, a pump circulates a heat transfer fluid through a series of buried pipes in a closed loop: the fluid never leaves the system, but rather travels back and forth in a loop between the earth connection and the heat pump. The length of the ground loop is determined by the size of the heating and cooling loads of the building and the ground thermal properties. The loads are defined by the size of the building, type of construction, use of the building, duration of the heating and cooling seasons, and climate.
Closed-loop systems are environmentally benign. They are sealed so that no fluid is exchanged with the environment. The fluid often includes an antifreeze solution to protect the heat pump equipment. The high-density polyethylene piping used in geoexchange systems is the same or higher grade of pipe used in cross country natural gas piping and often comes with a 50-year warranty.
The piping is installed either horizontally or vertically. The vertical bore configuration is a popular choice for systems of all sizes because of its efficient use of space. Each bore hole is 4 to 6 inches in diameter. A pipe is lowered to the bottom of the bore, makes a U-turn and returns to the top of the bore. The remaining space is filled with a grout to seal the hole from potential ground water penetration. Grout provides the means for thermal contact between the pipe and the surrounding earth. The header combines the flow through all the circuits before going to the building portion of the loop. The header can be installed outdoors in a valve pit or all of the circuits can be brought into the building before being combined. Six to twelve individual bores are typically connected together to form a circuit. The circuit connects to a header through a shut-off valve so a circuit can be isolated.
So, how much does it cost to install a geothermal system and what kind of savings can commercial building owners expect?
Let’s use a 50,000 square foot building as an example. The cost to install a basic geothermal heating system is comparable to the costs of conventional systems except for the additional cost for installing the ground heat exchanger. The installation of the ground heat exchanger for this building can cost up to $500,000. Yet many geothermal heating systems can reduce heating and cooling costs by as much as 40 percent. That can enable commercial building owners to pay for an entire system out of savings accrued in roughly seven to 10 years.
The additional cost of the heat exchanger can further be reduced by installing a Hybrid Geothermal system. The U.S. Department of Energy (DOE) highlighted a recent report – Hybrid Ground-Source Heat Pump Installations: Experiences, Improvements and Tools – demonstrating hybrid ground-source heat pumps (GSHP) as a viable solution to reduce energy use in commercial buildings. A hybrid system can dramatically decrease up-front costs while delivering financial and environmental benefits nearly equivalent to standard ground-source heat pump systems. Hybrid GSHP technology could be deployed widely, saving energy and money in commercial, industrial, and institutional buildings.
You can learn more by referring to the following link and downloading the full report: http://apps1.eere.energy.gov/news/progress_alerts.cfm/pa_id=631.
Having a geothermal heating system can also increases the value of your property and can make you eligible for a number of state and federal tax incentives. Most importantly, geothermal heating systems can drastically reduce greenhouse emissions. In fact, the U.S. EPA reports that geothermal heating systems reduce emissions anywhere from 40 percent to 70 percent, which is far superior to any kind of alternative energy source.
Sure, we all want to be greener and lessen our carbon footprint. Geothermal is a way to accomplish that and improve your bottom line.-¨
Former Green Beret Don Magglioli, PE, LSP, LEED AP, CGD, is the owner of Alares LLC, a Service-Disabled Veteran-Owned Small Business (SDVOSB) a green design/build construction firm based in Quincy, Mass. For more information, visit www.alaresLLC.com.